Correcting for Peculiar Velocities of Type Ia Supernovae in Clusters of Galaxies P.-F

A&A 615, A162 (2018) Astronomy https://doi.org/10.1051/0004-6361/201832932 & © ESO 2018 Astrophysics

Correcting for peculiar velocities of Type Ia supernovae in clusters of galaxies P.-F. Léget1,2, M. V. Pruzhinskaya1,3, A. Ciulli1, E. Gangler1, G. Aldering4, P. Antilogus5, C. Aragon4, S. Bailey4, C. Baltay6, K. Barbary4, S. Bongard5, K. Boone4,7, C. Buton8, M. Childress9, N. Chotard8, Y. Copin8, S. Dixon4, P. Fagrelius4,7, U. Feindt10, D. Fouchez11, P. Gris1, B. Hayden4, W. Hillebrandt12, D. A. Howell13,14, A. Kim4, M. Kowalski15,16, D. Kuesters15, S. Lombardo15, Q. Lin17, J. Nordin15, R. Pain5, E. Pecontal18, R. Pereira8, S. Perlmutter4,7, D. Rabinowitz6, M. Rigault1, K. Runge4, D. Rubin4,19, C. Saunders5, L.-P. Says1, G. Smadja8, C. Soﬁatti4,7, N. Suzuki4,22, S. Taubenberger12,20, C. Tao11,17, and R. C. Thomas21 THE NEARBY SUPERNOVA FACTORY

1 Université Clermont Auvergne, CNRS/IN2P3, Laboratoire de Physique de Clermont, 63000 Clermont-Ferrand, France e-mail: [email protected] 2 Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics, Stanford University, Stanford, CA 94305, USA 3 Lomonosov Moscow State University, Sternberg Astronomical Institute, Universitetsky pr. 13, Moscow 119234, Russia 4 Physics Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA 5 Laboratoire de Physique Nucléaire et des Hautes Énergies, Université Pierre et Marie Curie Paris 6, Université Paris Diderot Paris 7, CNRS-IN2P3, 4 place Jussieu, 75252 Paris Cedex 05, France 6 Department of Physics, Yale University, New Haven, CT 06250-8121, USA 7 Department of Physics, University of California Berkeley, 366 LeConte Hall MC 7300, Berkeley, CA 94720-7300, USA 8 Université de Lyon, Université de Lyon 1, Villeurbanne, CNRS/IN2P3, Institut de Physique Nucléaire de Lyon, 69622 Lyon, France 9 Department of Physics and Astronomy, University of Southampton, Southampton, Hampshire SO17 1BJ, UK 10 The Oskar Klein Centre, Department of Physics, AlbaNova, Stockholm University, 106 91 Stockholm, Sweden 11 Aix-Marseille Université, CNRS/IN2P3, CPPM UMR 7346, 13288 Marseille, France 12 Max-Planck Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching, Germany 13 Las Cumbres Observatory Global Telescope Network, 6740 Cortona Dr., Suite 102 Goleta, CA 93117, USA 14 Department of Physics, University of California, Santa Barbara, CA 93106-9530, USA 15 Institut fur˜ Physik, Humboldt-Universitãt zu Berlin, Newtonstr. 15, 12489 Berlin, Germany 16 Deutsches Elektronen-Synchrotron, 15735 Zeuthen, Germany 17 Tsinghua Center for Astrophysics, Tsinghua University, Beijing 100084, PR China 18 Centre de Recherche Astronomique de Lyon, Université Lyon 1, 9 Avenue Charles André, 69561 Saint-Genis-Laval, France 19 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA 20 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany 21 Computational Cosmology Center, Computational Research Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road MS 50B-4206, Berkeley, CA 94720, USA 22 Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583, Japan

Received 1 March 2018 / Accepted 6 April 2018

ABSTRACT

Context. Type Ia supernovae (SNe Ia) are widely used to measure the expansion of the Universe. To perform such measurements the luminosity and cosmological redshift (z) of the SNe Ia have to be determined. The uncertainty on z includes an unknown peculiar velocity, which can be very large for SNe Ia in the virialized cores of massive clusters. Aims. We determine which SNe Ia exploded in galaxy clusters using 145 SNe Ia from the Nearby Supernova Factory. We then study how the correction for peculiar velocities of host galaxies inside the clusters improves the Hubble residuals. Methods. We found 11 candidates for membership in clusters. We applied the biweight technique to estimate the redshift of a cluster. Then, we used the galaxy cluster redshift instead of the host galaxy redshift to construct the Hubble diagram. Results. For SNe Ia inside galaxy clusters, the dispersion around the Hubble diagram when peculiar velocities are taken into account is smaller compared with a case without peculiar velocity correction, which has a wRMS = 0.130 0.038 mag instead of wRMS = 0.137 0.036 mag. The significance of this improvement is 3.58σ. If we remove the very nearby± Virgo cluster member SN2006X (z < 0±.01) from the analysis, the significance decreases to 1.34σ. The peculiar velocity correction is found to be highest for the SNe Ia hosted by blue spiral galaxies. Those SNe Ia have high local specific star formation rates and smaller stellar masses, which is seemingly counter to what might be expected given the heavy concentration of old, massive elliptical galaxies in clusters. Conclusions. As expected, the Hubble residuals of SNe Ia associated with massive galaxy clusters improve when the cluster redshift is taken as the cosmological redshift of the supernova. This fact has to be taken into account in future cosmological analyses in order to achieve higher accuracy for cosmological redshift measurements. We provide an approach to do so. Key words. supernovae: general – galaxies: clusters: general – galaxies: distances and redshifts – dark energy A162, page 1 of 12 Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A&A proofs: manuscript no. SNIa_in_Clusters A&A 615, A162 (2018) erating expansion of the Universe (Perlmutter et al. 1998, 1999, Riess et al. 1998, Schmidt et al. 1998). The most recent analysis 1.of Introduction SNe Ia indicates that for a flat ΛCDM cosmology, our Uni- cluster redshift histogram verse is accelerating; this analysis found that Ω = 0.705 0.034 Doppler shift Type Ia supernovae (SNe Ia) are excellent distanceΛ indicators.± Observations(Betoule et al. of 2014 distant; Scolnic SNe Ia et led al. to2017 the). discovery of the accel- Cosmological parameters are estimated from the luminos-

erating expansion of the Universe (Perlmutter et al. 1998, 1999; number of galaxies Riessity distance-redshift et al. 1998; Schmidt relation et al. of 1998 SNe). Ia, The using most the recent Hubble analysis dia- zobs µ Doppler shift ofgram. SNe Generally, Ia indicates particular that for a attention flat ΛCDM is paid cosmology, to standardization our Uni- verseof SNe is accelerating; Ia, i.e., to increase this analysis of the found accuracy that ΩΛ of= luminosity0.705 0.034 dis- (tanceBetoule determinations et al. 2014; Scolnic (Rust 1974 et al.; 2017Pskovskii). 1977, 1984;± Phillips Hubble law 1993Cosmological; Hamuy et al. parameters 1996a; Phillips are estimated et al. 1999 from; Riess the luminosity et al. 1996; True SN Ia redshift distance-redshiftPerlmutter et al. 1997 relation, 1999 of; Wang SNe Ia, et al. using 2003 the; Guy Hubble et al. 2005 dia-, Observed SN Ia redshift gram.2007; Generally,Jha et al. 2007 particular; Bailey attention et al. 2009 is;paid Wang to et standardization al. 2009; Kelly et al. 2010; Sullivan et al. 2010; Chotard et al. 2011; Blondin of SNe Ia, that is, to increase of the accuracy of luminosity dis- µ et al. 2012; Rigault et al. 2013; Kim et al. 2013; Fakhouri et al. ∆ tance determinations (Rust 1974; Pskovskii 1977, 1984; Phillips Doppler shift 19932015; ;Phillips Sasdelli et et al. al. 1999 2016; ;Hamuy Léget 2016 et al.; 1996aSaunders; Riess 2017 et). al. The 1996 un-; Perlmuttercertainty on et the al. 1997 redshift, 1999 is very; Wang often et al.considered 2003, 2009 negligible.; Guy et The al. zc 2005redshift, 2007 used; Jha in et the al.luminosity 2007; Bailey distance-redshift et al. 2009; Kelly relation et al. 2010 is due; Fig. 1. Hubble diagram demonstrating how large peculiar velocity can to the expansion of the Universe assuming Friedman-Lemaitre- Chotard et al. 2011; Blondin et al. 2012; Rigault et al. 2013; Kim affectFig. 1: the Hubble measurements diagram of the demonstrating expansion history how of large the Universe. peculiar The ve- Robertson-Walker metric, i.e., the motion within the reference P.-F. Léget & SNfactory: Type Ia supernovae and Galaxy clusters et al. 2013; Fakhouri et al. 2015; Sasdelli et al. 2016; Léget 2016; insetlocity plot can is a aff typicalect the velocity measurements distribution of of the galaxies expansion inside a history cluster. of frame defined by the cosmic microwave background radiation Saunders 2017, in prep.). The uncertainty on the redshift is very the Universe. The inset plot is a typical velocity distribution of (CMB). We refer to this as a cosmological redshift (z ). In fact, often considered negligible. The redshift used in the luminosityc galaxies inside a cluster. these assumptions has negligible impact on our results due to the redshift observed on the Earth (z ) also includes the contri- distance-redshift relation is due toobs the expansion of the Uni- the low redshifts of our SNe Ia and the fact that H0 is simply versebution assuming from the Friedman–Lemaitre–Robertson–Walker Doppler effect induced by radial peculiar metric, veloc- absorbed into the Hubble diagram zero point. thatities is, (z thep), motion within the reference frame defined by the cos- 1 mic microwave background radiation (CMB). We refer to this is σV = 1038 km s− (Colless & Dunn 1996). The dispersion as a cosmological redshift (zc). In fact, the redshift observed on inside the cluster can be much greater than that usually assumed 2. Nearby Supernova Factory data (1 + zobs) = (1 + zc)(1 + zp). (1) the Earth (zobs) also includes the contribution from the Doppler in cosmological analyses and therefore can seriously affect the This analysis is based on 145 SNe Ia obtained by the SNfactory effectAt induced low redshift by radial and peculiar for low velocities velocities compared (zp), to the speed redshift measurements (see Fig.1). Moreover, within a cluster, collaboration between 2004 and 2009 with the SuperNova In- of light in vacuum, the following approximation can be used: the perturbations are no longer linear, and therefore cannot be (1 + zobs) = (1 + zc)(1 + zp). (1) corrected using the smoothed velocity field. Assuming a linear tegral Field Spectrograph (SNIFS; Aldering et al. 2002, Lantz Hubble flow, we can transform the dispersion due to peculiar ve- et al. 2004) installed on the University of Hawaii 2.2 m tele- At low redshift and for low velocities compared to the speed zobs = zc + zp. (2) locities into the following magnitude error: scope (Mauna Kea). The SNIFS is a fully integrated instrument of light in vacuum, the following approximation can be used: optimized for semi-automated observations of point sources on The component of the redshift due to peculiar velocities in- a structured background over an extended optical window at zobs = zc + zp. (2) 5 σV cludes the rotational and orbital motions of the Earth, the solar σm = . (3) moderate spectral resolution. This instrument has a fully filled orbit within the Galaxy, peculiar motion of the Galaxy within cz ln(10) 6.400 6.400 spectroscopic field of view subdivided into a grid The component of the redshift due to peculiar velocities the Local Group, infall of the Local Group toward the center of of 15× 15 contiguous square spatial elements (spaxels). The includes the rotational and orbital motions of the Earth, the solar Calculations using Eq.3 show that for the low redshift region × the Local Supercluster, etc. It is well known that peculiar veloci- 1 1 dual-channel spectrograph simultaneously covers 3200–5200 Å orbit within the Galaxy, peculiar motion of the Galaxy within (z < 0.05) this error is higher than the 150 km s− and 300 km s− ties of SNe Ia introduce additional errors to the Hubble diagram Fig. 2. Redshift uncertainties (in magnitude units) due to different levels the Local Group, infall of the Local Group toward the center of that is usually assumed and is two times larger than the intrinsicff (B-channel) and 5100–10000 Å (R-channel) with 2.8 and 3.2 and therefore have an impact on the estimation of cosmologi- Fig.of peculiar 2: Redshift velocities uncertainties as a function (in ofmagnitude the cosmological units) due redshift. to di Theer- the Local Supercluster, etc. It is well known that peculiar veloci- dispersion of SNe Ia around the Hubble diagram (Fig.2). This Å resolution, respectively. The data reduction of the x, y, λ data cal parameters (Cooray & Caldwell 2006; Hui & Greene 2006; entsolid levels black of line peculiar corresponds velocities to the as Coma a function cluster of velocity the cosmological dispersion; ties of SNe Ia introduce additional errors to the Hubble diagram means that standard methods to take into account peculiar veloc-1 cubes was summarized by Aldering et al.(2006) and updated in Davis et al. 2011; Habibi et al. 2018). To minimize the influence redshift.the dashed The and solid dash-dotted blackline lines corresponds correspond to to 300 the and Coma 150 km cluster s− , and therefore have an impact on the estimation of cosmologi- ities do not work for galaxies inside clusters, and another more Sect. 2.1 of Scalzo et al.(2010). A preview of the flux calibration of poorly constrained peculiar velocities, in some cosmological velocityrespectively. dispersion; The red linethe dashed shows the and intrinsic dash-dotted dispersion lines of correspond SNe Ia on cal parameters (Cooray & Caldwell 2006; Hui & Greene 2006; totheaccurate 300 Hubble km method diagram s 1 and needs found 150 km to for be sthe developed1, JLA respectively. sample for (Betoule these The redspecial et al. line 2014 cases. shows). is developed in Sect. 2.2 of Pereira et al.(2013), based on the at- analyses all SNe Ia with z < 0.015 are removed from the Hubble − − mospheric extinction derived in Buton et al.(2013), and the host Davis et al. 2011; Habibi et al. 2018). To1 minimize the influence the intrinsicFor a supernova dispersion (SN) of SNe in a Ia cluster on the it Hubble is possible diagram to estimate found diagram fitting and a 300–400 km s− peculiar velocity disper- cl subtraction is described in Bongard et al.(2011). For every SN of poorly constrained peculiar velocities, in some cosmological forzc more the JLA accurately sampleusing (Betoule the ethost al. galaxy2014). cluster redshift (z ) in- sion is added in quadrature to the redshift uncertainty (Astier that contains more than 10001 host members, the velocity dispersion factory analyses all SNe Ia with z < 0.015 are removed from the Hubble stead of the host redshift1 (z ). The mean cluster redshift is followed, the SN creates a spectrophotometric time se- et al. 2006; Wood-Vasey et al. 2007; Amanullah et al. 2010). In is σV = 1038 km s− (Colless & Dunn 1996). The dispersion diagram fitting and a 300–400 km s 1 peculiar velocity disper- not affected by virialization within a cluster. Of course clusters ries composed of 13 epochs on average; the first spectrum was particular, this is the approach taken− for the cosmology analysis inside the cluster can be much greater than that usually assumed ∼ sion is added in quadrature to the redshift uncertainty (Astier also have peculiar velocities that can sometimes manifest them- taken before maximum light in the B band (Bailey et al. 2009; using Union 2.1 (Suzuki et al. 2012). Another way to apply the in cosmological analyses and therefore can seriously affect the et al. 2006; Wood-Vasey et al. 2007; Amanullah et al. 2010). In selves as cluster merging, for example, Bullet clusters (Clowe Chotard et al. 2011). In addition, observations are obtained at peculiar velocity correction is to measure the local velocity field Tullyredshift & Shayameasurements 1984; Blakeslee (see Fig. et1). al. Moreover, 1999; Radburn-Smith within a cluster, et al. particular, this is the approach taken for the cosmology analy- et al. 2006). However, clusters have much smaller peculiar ve- the supernova location at least one year after the explosion to assuming linear perturbation theory and then correct each su- 2004the perturbations; Karachentsev are et no al. longer2014). linear, To account and therefore for the peculiar cannot1 ve- be sis using Union 2.1 (Suzuki et al. 2012). Another way to apply locities than the galaxies within them (i.e., 300 km s− ; Bahcall serve as a final reference to enable the subtraction of the under- pernova redshift (Hudson et al. 2004). Willick & Strauss(1998) locitiescorrected of using galaxies the in smoothed clusters velocityBlakeslee field. et∼ al. Assuming(1999) proposed a linear lying host. The host galaxy redshifts of the SNfactory SNe Ia the peculiar velocity correction is to measure the local1 veloc- severalHubble& Oh 1996 alternative flow,; Dale we can etapproaches. al. transform 1999; Masters The the first dispersion et is al. to 2006 keep due). using to the peculiar indi- estimated the accuracy of this method to be 100 km s− , Riess are given in Childress et al. 2013. The sample of 145 SNe Ia ity field assuming linear perturbation theory∼1 and then correct vidualvelocitiesThe velocities fact into that the of there following galaxies is additional magnitudebut to add velocity extra error: dispersionvariance in of quadra- galax- et al.(1997) adopted the value of 200 km s − , and Conley et al. / contains those objects through 2009 having good final references each supernova redshift (1Hudson et al. 2004). Willick & Strauss tureies inside for the the clusters clusters according that should to beσ taken(r) = intoσ / account[1 + (r/ hasr )2 been]1 2, (2011) used 150 km s− . This approach was used in the Joint1 cl 0 0 known for5 σV a long time. Indeed,1 the distance measurements are and properly measured light curve parameters, including quality (1998) estimated the accuracy of this method to be 100 km s− , where σ = 700 (400) km s− and r = 2 (1) Mpc for Virgo (For- Light-Curve Analysis (JLA; Betoule et al. 20141).∼ However, it σm = 0 . 0 (3) cuts suggested by Guy et al.(2010). Riess et al.(1997) adopted the value of 200 km s − , and Conley nax).degenerate Thecz ln(10) second in terms approach of redshift is to use due a tofixed the velocity presence error of andgalaxy to has been shown that the systematic1 uncertainty on w, the dark The nearby supernova search is more complicated than the et al.(2011) used 150 km s − . This approach was used in the removeclusters the and virial this dispersion is accounted by assigning for when galaxies Tully-Fisher their method group- energy equation of state parameter, of different flow models is at search for distant SNe Ia because to probe the same volume it is Joint Light-Curve Analysis (JLA; Betoule et al. 2014). However, averaged(TullyCalculations & Fisher velocities. 1977 using Nevertheless,) is Eq. applied (3) show to measure peculiar that for distances. velocity the low correction This redshift prob- the level of 0.04 (Neill & Conley 2007). 1 necessary to sweep a much larger sky field. Rather than target- it has been shown± that the systematic uncertainty on w, the dark withinregionlem is (galaxy knownz < 0.05 clusters as) this the triple error has received is value higher problem, little than attention the which 150 and inis theSN 300 factIa km stud- that s− It has nonetheless been observed that velocity dispersions ff ing high-density galaxy fields that could potentially bias the sur- energy equation of state parameter,1 of different flow models is at ies,thatfor awith is given usually the distance exceptions assumed one and of can Feindt is get two three et times al. di 2013 largererent and thanvalues Dhawan the of intrinsic redshift et al. can exceed 1000 km s− in galaxy clusters (Ruel et al. 2014). vey, at the beginning of the SNfactory experiment (2004–2008) the level of 0.04 (Neill & Conley 2007). 2017dispersiondue to. The the redshift ofpresence SNe correctionIa of around a cluster theinduced (see, Hubble bye.g., galaxy diagram Tonry clusters & (Fig. Davis2). is 1981 Thismen-; For example,± in the Coma cluster, a large cluster of galaxies SNe Ia were discovered with the 1.2 m telescope at the Mount It has nonetheless been observed that velocity dispersions tionedmeans1 onlythat standard briefly in methods those analyses, to take into as their account objectives peculiar were veloc- to that contains more than1 1000 members, the velocity dispersion Hereafter, we refer to this procedure as peculiar velocity correction. Palomar Observatory (Rabinowitz et al. 2003) in a nontargeted can exceed 1000 km s− in galaxy clusters (Ruel et al. 2014). measureities do not the work bulk forflow galaxies with SNe inside Ia (Feindt clusters, et and al. 2013 another) and more the mode, by surveying about 500 square degrees of sky every night. For example, in the Coma cluster, a large cluster of galaxies Hubbleaccurate constant method ( needsDhawan to be etal. developed 2017). However, for these atspecial low redshifts cases. Article number, page 2 of 13 In all 20000 square degrees were monitored over the course of this correction is necessary, which is why we focus on it here. A162, page 2 of 12 a year.∼ The SNfactory performed follow-up observations of a In this paper we identify SNe Ia that appear to reside in few SNe Ia discovered by the Palomar Transient Factory (Law known clusters of galaxies. We then estimate the impact of their et al. 2009), which also were found in a nontargeted search. We peculiar velocities by replacing the host redshift by the cluster chose to examine this sample, despite it being only 20% of all redshift. As our parent sample we use 145 SNe Ia observed by nearby cosmologically useful SNe Ia in order to use a homoge- the Nearby Supernova Factory (SNfactory), a project devoted neous dataset primarily from a blind SN Ia search to avoid any to the study of SNe Ia in the nearby Hubble flow (0.02 < z < bias due to the survey strategy. However, 22 SNe Ia in the sample 0.08; Aldering et al. 2002). We then compare the Hubble residu- were not discovered by these research programs but by amateur als (HRs) for SNe Ia in galaxy clusters before and after peculiar astronomers or specific surveys in clusters of galaxies. In par- velocity correction. ticular, SN2007nq, which will be identified as being in a cluster, The paper is organized as follows: In Sect.2 the SN factory comes from a specific search within clusters of galaxies (Quimby dataset is described. In Sect.3 the host clusters data and the et al. 2007); SN2006X and SN2009hi, which were also identi- matching with SNe Ia are presented. In Sect.4 we introduce the fied as being in clusters, come from targeted searches (Suzuki, peculiar velocity correction and study how it affects the HRs. We & Migliardi 2006; Nakano et al. 2009). discuss the robustness of our results and the properties of SNe Ia As mentioned above, SN2006X is located in the Virgo clus- in galaxy clusters in Sect.5. Finally, the conclusions of this study ter and is a highly reddened SN Ia with a SALT2 color of are given in Sect.6. C = 1.2. This SN Ia would not be kept for a classical cosmo- Throughout this paper, we assume a flat ΛCDM cosmology logical analysis, but since we are only interested in the effects of 1 1 with ΩΛ = 0.7, Ωm = 0.3, and H0 = 70 km s− Mpc− . Varying peculiar velocities, we have kept it in the analysis.

Article number, page 3 of 13 P.-F. Léget et al.: Type Ia supernovae and Galaxy clusters

For a supernova (SN) in a cluster it is possible to esti- Integral Field Spectrograph (SNIFS; Aldering et al. 2002; Lantz mate zc more accurately using the host galaxy cluster redshift et al. 2004) installed on the University of Hawaii 2.2 m telescope (z cl) instead of the host redshift1 (z host). The mean cluster red- (Mauna Kea). The SNIFS is a fully integrated instrument opti- shift is not affected by virialization within a cluster. Of course, mized for semi-automated observations of point sources on a clusters also have peculiar velocities that can sometimes mani- structured background over an extended optical window at mod- fest themselves as cluster merging, for example, Bullet clusters erate spectral resolution. This instrument has a fully filled 6.4 00 × (Clowe et al. 2006). However, clusters have much smaller pecu- 6.400 spectroscopic field of view subdivided into a grid of 15 15 liar velocities than the galaxies within them (i.e., 300 km s 1; contiguous square spatial elements (spaxels). The dual-channel× ∼ − Bahcall & Oh 1996; Dale et al. 1999; Masters et al. 2006). spectrograph simultaneously covers 3200–5200 Å (B-channel) The fact that there is additional velocity dispersion of galax- and 5100–10 000 Å (R-channel) with 2.8 and 3.2 Åresolution, ies inside the clusters that should be taken into account has been respectively. The data reduction of the x, y, λ data cubes was known for a long time. Indeed, the distance measurements are summarized by Aldering et al.(2006) and updated in Sect. 2.1 degenerate in terms of redshift due to the presence of galaxy of Scalzo et al.(2010). A preview of the flux calibration is clusters and this is accounted for when Tully–Fisher method developed in Sect. 2.2 of Pereira et al.(2013), based on the (Tully & Fisher 1977) is applied to measure distances. This prob- atmospheric extinction derived in Buton et al.(2013), and the lem is known as the triple value problem, which is the fact that host subtraction is described in Bongard et al.(2011). For every for a given distance one can get three different values of red- SN followed, the SNFACTORY creates a spectrophotometric time shift due to the presence of a cluster (see, e.g., Tonry & Davis series composed of 13 epochs on average; the first spectrum 1981; Tully & Shaya 1984; Blakeslee et al. 1999; Radburn-Smith was taken before maximum∼ light in the B-band (Bailey et al. et al. 2004; Karachentsev et al. 2014). To account for the peculiar 2009; Chotard et al. 2011). In addition, observations are obtained velocities of galaxies in clusters, Blakeslee et al.(1999) pro- at the supernova location at least one year after the explosion to posed several alternative approaches. The first is to keep using serve as a final reference to enable the subtraction of the under- the individual velocities of galaxies but to add extra variance lying host. The host galaxy redshifts of the SNFACTORY SNe Ia in quadrature for the clusters according to σcl(r) = σ0/[1 + are given in Childress et al.(2013). The sample of 145 SNe Ia 2 1/2 1 (r/r0) ] , where σ0 = 700 (400) km s− and r0 = 2 (1) Mpc for contains those objects through 2009 having good final references Virgo (Fornax). The second approach is to use a fixed velocity and properly measured light curve parameters, including quality error and to remove the virial dispersion by assigning galaxies cuts suggested by Guy et al.(2010). their group-averaged velocities. Nevertheless, peculiar velocity The nearby supernova search is more complicated than the correction within galaxy clusters has received little attention in search for distant SNe Ia because to probe the same volume it is SN Ia studies, with the exceptions of Feindt et al.(2013) and necessary to sweep a much larger sky field. Rather than targeting Dhawan et al.(2018). The redshift correction induced by galaxy high-density galaxy fields that could potentially bias the survey, clusters is mentioned only briefly in those analyses, as their at the beginning of the SNFACTORY experiment (2004–2008) objectives were to measure the bulk flow with SNe Ia (Feindt SNe Ia were discovered with the 1.2 m telescope at the Mount et al. 2013) and the Hubble constant (Dhawan et al. 2018). How- Palomar Observatory (Rabinowitz et al. 2003) in a nontargeted ever, at low redshifts this correction is necessary, which is why mode, by surveying about 500 square degrees of sky every night. we focus on it here. In all 20 000 square degrees were monitored over the course of In this paper we identify SNe Ia that appear to reside in ∼ a year. The SNFACTORY performed follow-up observations of a known clusters of galaxies. We then estimate the impact of their few SNe Ia discovered by the Palomar Transient Factory (Law peculiar velocities by replacing the host redshift by the cluster et al. 2009), which also were found in a nontargeted search. We redshift. As our parent sample we use 145 SNe Ia observed by chose to examine this sample, despite it being only 20% of all the Nearby Supernova Factory (SNFACTORY), a project devoted to the study of SNe Ia in the nearby Hubble flow (0.02 < z < nearby cosmologically useful SNe Ia in order to use a homoge- 0.08; Aldering et al. 2002). We then compare the Hubble residu- neous dataset primarily from a blind SN Ia search to avoid any als (HRs) for SNe Ia in galaxy clusters before and after peculiar bias due to the survey strategy. However, 22 SNe Ia in the sample velocity correction. were not discovered by these research programs but by amateur The paper is organized as follows. In Sect.2, the SN FAC- astronomers or specific surveys in clusters of galaxies. In par- TORY dataset is described. In Sect.3 the host clusters data and ticular, SN2007nq, which will be identified as being in a cluster, the matching with SNe Ia are presented. In Sect.4 we introduce comes from a specific search within clusters of galaxies (Quimby the peculiar velocity correction and study how it affects the HRs. et al. 2007); SN2006X and SN2009hi, which were also identi- We discuss the robustness of our results and the properties of fied as being in clusters, come from targeted searches (Suzuki & SNe Ia in galaxy clusters in Sect.5. Finally, the conclusions of Migliardi 2006; Nakano et al. 2009). this study are given in Sect.6. As mentioned above, SN2006X is located in the Virgo clus- Throughout this paper, we assume a flat ΛCDM cosmology ter and is a highly reddened SN Ia with a SALT2 color of 1 1 C = 1.2. This SN Ia would not be kept for a classical cosmo- with ΩΛ = 0.7, Ωm = 0.3, and H0 = 70 km s− Mpc− . Varying these assumptions has negligible impact on our results due to logical analysis, but since we are only interested in the effects of peculiar velocities, we have kept it in the analysis. the low redshifts of our SNe Ia and the fact that H0 is simply absorbed into the Hubble diagram zero point. 3. Host clusters data 2. Nearby Supernova Factory data In this section we describe how we selected the cluster candi- This analysis is based on 145 SNe Ia obtained by the SNFAC- dates for associations with SNFACTORY SNe (Sect. 3.1). We TORY collaboration between 2004 and 2009 with the SuperNova then present our technique for calculating the cluster redshift and its error (Sect. 3.2). Our final list of associations appears 1 Hereafter, we refer to this procedure as peculiar velocity correction. in Sect. 3.3.

A162, page 3 of 12 A&A proofs:A&Amanuscript 615, A162 no. (2018) SNIa_in_Clusters

3.1.3. Host Preliminary clusters cluster data selection 46 SeveralIn this section methods we for describe identifying how we clusters selected of the galaxies cluster have can- 1500 beendidates developed for associations (e.g., Abell with 1958 SNfactory; ZwickySNe et al. (Sect. 1961 3.1; Gunn). We 45 etthen al. present1986; Abell our technique et al. 1989 for; Vikhlinin calculating et the al. cluster1998; Kepner redshift 1300 etand al. its 1999 error; (Sect.Gladders 3.2). & Our Yee ﬁnal 2000 list; ofPiffaretti associations et al.appears 2011; 44 ]) Planckin Sect. Collaboration 3.3. XXIV 2016). However, each of these 1 1100 ] − methods contains assumptions about cluster properties and is 1 −

subject to selection effects. The earliest method used to identify [erg s 43 900 [km s

clusters3.1. Preliminary was the analysis cluster of selection the optical images for the presence of 500 V over-density regions. Finding clusters with this method suffers 700 σ fromSeveral contamination methods for by identifying foreground clusters and of background galaxies have galaxies been log(L 42 thatdeveloped produce (e.g., the Abell false effect1958; ofAbell over-density, et al. 1989 which; Zwicky becomes et al. more1961;significant Gunn et al. for1986 high; Vikhlinin redshift. et al.The 1998 method; Kepner that et helps al. 1999 to; 500 reduceGladders this & projection Yee 2000; effect Piffaretti is the et al.red 2011 sequence; Planck method Collaboration (RSM). 41 Thiset al.method 2016b). is However, based on each the of fact these that methods galaxy contains clusters assump- contain 300 ations population about cluster of elliptical properties and and lenticular is subject galaxies to selection that efollowffects. 40 anThe empirical earliest method relationship used between to identify their clusters color was and the magnitude analysis 0.00 0.02 0.04 0.06 0.08 0.10 andof the form optical the so-called images for red the sequence presence (Gladders of over-density & Yee regions.2000). z TheFinding projection clusters of with random this method galaxies su atffers different from contamination redshifts is not by Fig.Fig. 3:3. LuminositiesLuminosities of [0.1-2.4 [0.1–2.4 keV] keV] within R500 of MCXC MCXC clus- expectedforeground to andform background a clear red galaxies sequence. that The produce RSM the also false requires effect ters (Piffaretti et al. 2011) as a function of redshift,500 up to z = 0.1. ters (Piffaretti et al. 2011) as a function of redshift, up to z = 0.1. multicolorof over-density, observations. which becomes Spectroscopic more significant redshift measurements for high red- The colorbar shows the corresponding cluster velocity dispersion σV helpshift. tremendously The method that in helps establishing to reduce which this projection galaxiesare effect cluster is the calculatedThe colorbar from showsEq. (7). the Black corresponding plus signs indicate cluster clusters velocity from the disper- cur- members,red sequence although method even (RSM). then the This triple method value is problem based on can the lead fact rentsion analysis.σV calculated The black from curve Eq.7 corresponds. Black plus to signs the intrinsic indicate dispersion clusters tothat erroneous galaxy clusters associations. contain a population of elliptical and lentic- offrom SNe the Ia on current the Hubble analysis. diagram The found black for curve the JLA corresponds sample (Betoule to the ularA galaxies third popular that follow and effective an empirical method relationship to detect between galaxy clus- their etintrinsic al. 2014 dispersion) projected of onto SNe cluster Ia on the luminosities Hubble diagram by combining found the for terscolor is and to observemagnitude the and diffuse formthe X-ray so-called emission red radiatedsequence by (Glad- the luminosity–massthe JLA sample and (Betoule mass–velocity et al. 2014 dispersion) projected relations. onto cluster lu- hotders gas & (10 Yee6–10 20008 K)). The in the projection centers of of the random clusters galaxies (Boldt at et dif- al. minosities by combining the luminosity-mass and mass-velocity 1966ferent; Sarazin redshifts 1988 is). not In expected virialized to systems form a the clear thermal red sequence. velocity dispersionTo measure relations. the redshift of the cluster, it is necessary to know ofThe gas RSM and alsothe velocity requires of multicolor the galaxies observations. in the cluster Spectroscopic are deter- which galaxies in the cluster field are its members. Galaxy clus- minedredshift by measurements the same gravitational help tremendously potential. As in a establishing result, clusters which of ters considered in this paper are old enough (z < 0.1) to exhibit galaxies are cluster members, although even then the triple value virialized regions (Wu et al. 2013). Therefore, to characterize the galaxies where peculiar velocities are important appear as lumi- 3.2. Cluster redshift measurement problem can lead to erroneous associations. 43 cluster radius we used the virial radius R200, corresponding to an nous X-ray emitters and have typical luminosities of X 10 – 45 1 L ∼ 1 average enclosed density equal to 200 times the critical density 10 Aerg third s− . popular Such luminosities and effective correspond method to to detectσV & galaxy700 km clus- s− Some published cluster redshifts have been determined from a (seeters Fig. is to3). observe The gas the distribution diffuse X-ray can emission be rather radiatedcompact by and the thus hot ofsingle the Universe or few galaxies. at redshift As wez, as want follows: to have a precise redshift cor- gas (106–108 K) in the centers of the clusters (Boldt et al. 1966; rection, we cannot simply replace the redshift of the host galaxy unresolved by X-ray surveys at intermediate and high redshifts. R200 R ρ=200ρ , (4) However,Sarazin 1988 nearby). In clusters virialized (z < systems0.1) are the well thermal resolved, velocity eliminating of gas by the≡ redshift| c of another galaxy. We therefore adopt the follow- and the velocity of the galaxies in the cluster are determined by ing method to improve cluster redshift estimates. contamination from X-ray AGN or stars. 2 the same gravitational potential. As a result, clusters of galax- To3H measure(z) the redshift of the cluster it is necessary to know Finally, clusters of galaxies also cause distortions in the ρc = , (5) CMBies where from peculiar the inverse velocities Compton are important scattering appear of the as CMB luminous pho- which8 galaxiesπG in the cluster field are its members. Galaxy clus- 43 45 tonsX-ray by emitters the hot and intra-cluster have typical gas.luminosities In the of fourthX and10 –10 final ters considered in this paper are old enough (z < 0.1) to exhibit erg s 1. Such luminosities correspond to σ & L700∼ km s 1 (see wherevirializedH(z regions) is the (Wu Hubble et al. parameter 2013). Therefore, at redshift to characterizez and G is the the cluster− identification method, this signature,V known as− the Newtonian gravitational constant. Sunyaev-Zel’dovichFig.3). The gas distribution (SZ) effect, can be is rather used compact to identify and thus clusters un- cluster radius we used the virial radius R200, corresponding to an resolved by X-ray surveys at intermediate and high redshifts. averageAccording enclosed to density the virial equal theorem, to 200 times the velocity the critical dispersion density (Planck Collaboration XXIV 2016). σ inside a cluster is given as However,Using the nearby SIMBAD clusters database (z < 0.1) (Wenger are well et resolved, al. 2000), eliminating we chose ofV the Universe at redshift z, as follows: allcontamination the clusters from projected X-ray within AGN or2.5 stars. Mpc around the SNe Ia ∼ R200 RGMρ=200200ρc , (4) positionsFinally, and clusters with redshift of galaxies differing also from cause that distortions of the super- in the σV ≡ | . (6) ≈ novaCMB by from less the than inverse 0.015. Compton SN Ia scattering host redshifts of the were CMB used photons to r R200 initiallyby the hot determine intra-cluster the distance. gas. In the We fourth did not and consider final cluster objects identifi- clas- 4 3 Using Eq.2 (5) and M = πR 200ρ , we find sifiedcation as method, groups this of galaxies signature, (GrG), known although as the Sunyaev-Zel’dovich there is no strong 3H (z) 200 3 200 c ρ = , (5) boundary(SZ) effect, between is used these to identify and clusters clusters since (Planck GrG are Collaboration character- c π σV 108 RG200 H(z). (7) izedet al. by 2016b smaller). mass and therefore smaller velocity dispersion ≈ where H(z) is the Hubble parameter at redshift z and G is the 300 km s 1 (see Fig. 5 in Mulchaey 2000). The uncertainty cl Using the− SIMBAD database (Wenger et al. 2000) we chose NewtonianThe cluster gravitational redshift uncertainty constant. (zerr) can be found from the introduced∼ by such velocity is properly accounted for using all the clusters projected within 2.5 Mpc around the SNe Ia clusterAccording velocity dispersionto the virial and theorem, is written the as velocity dispersion thepositions conventional and with method redshift of di assigningffering∼ from a fixed that uncertainty of the supernova to all σV insideσ a cluster is given as SNe Ia to account for peculiar velocities. cl V by less than 0.015. SN Ia host redshifts were used to initially zerr = , (8) determine the distance. We did not consider objects classified Ngal 3.2.as groups Cluster of redshift galaxies measurement (GrG), although there is no strong bound- GM whereσ Np is200 a number. of cluster members used for the calcula-(6) ary between these and clusters since GrG are characterized by V ≈ galR Somesmaller published mass and cluster therefore redshifts smaller have velocity been determined dispersion from300 a tion. r 200 single1 or few galaxies. As we want to have a precise redshift∼ First, we took all the4 galaxies3 attributed to each cluster in km s− (see Fig. 5 in Mulchaey 2000). The uncertainty intro- Using Eq.5 and M200 = πR 200ρc we find correction,duced by such we velocitycannot simply is properly replace accounted the redshift for using of the the host con- literature sources and added3 200 the SNFACTORY host galaxy if it galaxyventional by the method redshift of assigning of another a galaxy. fixed uncertainty We therefore to all adopt SNe the Ia was not among them. Then, these data were combined with the followingto account method for peculiar to improve velocities. cluster redshift estimates. Dataσ Release10 R 13H( ofz). the release database of the Sloan Digital Sky(7) V ≈ 200 A162,Article page number, 4 of 12 page 4 of 13 P.-F.A Léget&A proofs:et al.: Typemanuscript Ia supernovae no. SNIa_in_Clusters and Galaxy clusters

lit yes R200 = R 200 t N >10 R = R v R query gal 200 t 200 200 t no Estimation t t of R200 t N <10 R = 1.1t Mpc gal 200 t t t SDSS DR13 t t query t t t t Simbad Galaxy cluster Remove Galaxyt list SNF host t query list duplicates in clustert area t t t Literature t request query t

output Ngal>Npaper computation Biweight

ﬁnal result zcl, zcl,err

for all clusters Keep literature else per cluster value

Fig.Fig. 4. 4:Workflow Workflow for for redshift redshift calculation calculation and and other other inputs inputs for matching for matching of SNe of to SNe galaxy to clusters.galaxy clusters. In this scheme, In thisN scheme,gal correspondsNgal corresponds to the number to N ofthe galaxies number used of togalaxies compute used theredshift to compute and thepaper redshiftcorresponds and N topaper the numbercorresponds of galaxies to the used number to estimate of galaxies the redshift used in to the estimate literature. the redshift in the literature. Survey (SDSS; Eisenstein et al. 2011; Dawson et al. 2013; Smee members were first transformed to the CMB frame. The trans- et al. 2013; SDSS Collaboration 2017). We selected all galaxies formation to the CMB frame made use of the NASA/IPAC withα = 1 spectroscopic.64 (see Table redshifts 1 in Arnaud located et al.in 2010 a circle). The withL500 thevalues center for moreExtragalactic spread out Database — like (NED). a filament would be. We conclude that, correspondingMCXC clusters to ( thePiff clusteraretti et coordinates al. 2011) as and a projectedfunction of inside redshift the consistent with the lack of X-rays, this is not a cluster. R radius of the cluster. A 5σ redshift cut was adopted in the are200 presented in Fig.3. Moreover,V in Fig.3 a continuous black 3.3.Two Final other matching clusters, and ZwCl confirmation 2259+0746 and A87, also require redshift direction (see Eq. (7)). line represents the minimum value of L500 that is required for discussion. Within 2.30 of the center of ZwCl 2259+0746 there theThe velocityR200 dispersionvalue was ofextracted the cluster from to the cause literature a deviation when frompos- isOnce a source the redshifts of X-ray emission, and R 1RXSvalues J230215.3 were obtained+080159. for How- each sible. For the clusters without published size measurements we 200 the Hubble diagram greater than the intrinsic dispersion in lumi- ever,cluster, the we size performed of the emission the final region matching. (30) is very A supernova small in compar- is con- estimatednosity of SNeR200 ourselves Ia. The figure from shows the velocity that all distribution the clusters of hosting galax- isonsidered with aR cluster500 value member for the if cluster the following (400). In addition,two conditions according are iesSNe around Ia except the clusterone are position above this following threshold the and procedure it is therefore described very tosatisfied: Mickaelian et al.(2006) this emission belongs to a star. There- inlikely Beers that et the al.( Doppler1990) with effect an induced initial guess by these of R clusters200 = 1 causes.1 Mpc. a fore,r we< R did200, not where assignr is this the X-ray projected source distance to ZwCl between 2259+ the0746. SN Ifdispersion the number in the of Hubble cluster membersdiagram that with is greaterspectroscopically than the intrinsic deter- Another• and cluster case is center. A87, which belongs to the A85/87/89 complex mineddispersion redshifts in luminosity was less of than SNe ten, Ia. Moreover, the value ofmore 1.1 than Mpc a washalf host cl σV of clustersz z of galaxies.< 3 c . According to Durret et al.(1998) the adoptedof the low as a redshift virial radius. clusters This are value above corresponds this limit, indicating to the average that galaxyThe•| SNe velocities Ia− that| did in not the satisfy A87 region these showcriteria the were existence removed of from sub- Rthe200 peculiarof clusters velocity in the correctionMeta-Catalog has of to X-Ray be taken Detected into account Clusters if groups,further consideration. which all have an X-ray counterpart and seem to be ofa SN Galaxies Ia belongs (MCXC; to a Piffaretti cluster of et galaxies al. 2011); and see is Fig. observed3. at low fallingOur onto final A85 criteria along are a slightly filament. different Therefore, than A87 those is applied not really by redshift.To estimate the redshift of a cluster we applied the so-called 1 aXavier cluster et but al.(2013 a substructure) (1.5 Mpc ofand A85σV that= 500 haskm a svery− ) and prominent Dilday biweightTo check technique for a linear (Beers red et al. sequence 1990) on feature, the remaining SDSS data redshift were dietff al.use 2010 X-ray (1 emission Mpc h 1 (andPiffaretti∆z = et0.015 al. 2011). These). We authors applied stud- our distributions. Biweight determines the kinematic properties of − employed. From the SDSS Galaxy table we chose all the galax- redshiftied the properties measurement and technique rate of supernovae to determine in theclusters CMB and redshift their galaxy clusters while being resistant to the presence of outliers ies in the R200 region around the cluster position. We extracted ofchoices the virialized were made region to be of consistent A85. Thus, with we previous included cluster A85/A87 SN inIa and is robust for a broad range of underlying velocity distri- model magnitudes, as recommended by SDSS for measuring ourrate final measurements. table for the These peculiar values velocity roughly analysis. characterize an average butions, even if they are non-Gaussian, using the median and colors of extended objects. cluster and we were guided by the same thoughts when mak- an outlier rejection based on the median absolute deviation. The final list of SNfactory SNe Ia in confirmed clusters con- We checked for detections of the SZ effect using the Planck tainsing the 11 preliminary objects. The cluster resulting selection association (2.5 Mpc of SNe and Ia∆z with= 0.015 host, Moreover,catalog of Beers Sunyaev-Zel’dovich et al.(1990) provided sources a (formulaPlanck Collaborationfor the cluster redshift uncertainty, but it cannot be used for clusters with clusterssee Sect. is 3.1 given). However, in Table1 since. Column clusters 1 is have the SN different name, size Col. and 2 et al. 2016a). All the clusters in our sample with SZ sources also containsvelocity dispersion, a name ofwe the determined identified host or extracted cluster of from galaxies, the litera- and fewhave members. X-ray emission, Therefore, as expected instead we for used real clusters.Eq. (8), which can be applied for all of our clusters. Col.ture the 3 is physical the MCXC parameters name. The of each MCXC cluster coordinates (R200 and ofσ theV ). Thishost ForSome some of our of the supposed clusters clusters the literature do not provides show X-ray only or the SZ final sig- clustermethod center provides are an given individual in Col. approach 4. Column to each 5 contains SN-cluster the pro- pair redshiftnatures of and a cluster. the number As described of galaxies, in Sect.N 3.1,, that low were redshift used clus- in jectedand allows separation, associationD, in with Mpc a between cluster to the be SN defined position with and greater the ters are expected to have X-ray emission.paper Therefore, only such the calculation, without publishing a list of cluster members. hostaccuracy. cluster center. The R200 value is in Col. 6 and the CMB su- Incandidates those cases, were if kept the for number further of analysis members (see collected Fig.3). by us sat- pernovaFollowing redshift Carlberg is in Col. et 7. al.The(1997 CMB), redshift and Rines of the & cluster Diaferio and Cases in which the red sequence is clearly seen but for which its uncertainty can be found in Cols. 8 and 9. The velocity dis- isfies Ngal < Npaper we adopted the redshift from literature. The (2006), we constructed an ensemble cluster from all the clusters detailedthere is no scheme diffuse of X-ray the cluster emission redshift can calculation be explained is eitherpresented by the in persionassociated of the with cluster SNe Ia estimated to smooth from over the theR200 asymmetriesvalue is shown in the in Fig.superposition4. of nearby clusters or being a group embedded in Col.individual 10. The clusters. number We of scaled galaxies the that velocities were used by σV forand cluster positions red- a filament.All the calculations For example, described our study above of the are redshift based on distribution spectro- shiftwith calculationthe values of is inR200 Col.for 11. each In clusterCol. 12 to we produce indicate Fig. the5. source This scopicaland sky projection redshifts. around Before the performing proposedhost the calculations cluster [WHL2012] of the ofshows galaxy our redshift selection information boundaries (lit. and is exhibits an abbreviation good separation for litera- of J132045.4+211627 of SNF20070417-002 revealed that many of ture).cluster In galaxies the last from Col. we surrounding summarize galaxies. all references for the cluster cluster CMB redshift, all of thecl heliocentric redshifts of its the redshifts used to determine z come from galaxies that are coordinates, R200, and non-SN galaxy redshifts. A162, page 5 of 12 Article number, page 6 of 13 P.-F. Léget & SNfactory: Type Ia supernovae and Galaxy clusters A&A 615, A162 (2018)

cl 1.2 The cluster redshift uncertainty (zerr) can be found from the clusters are expected to have X-ray emission. Therefore, only cluster velocity dispersion and is written as 4 1.1 such candidates were kept for further analysis (see Fig.3).

3 1.0 Cases in which the red sequence is clearly seen but for which there is no diffuse X-ray emission can be explained either by the cl σV 2 0.9 zerr = , (8) superposition of nearby clusters or being a group embedded in Ngal 1 0.8 a ﬁlament. For example, our study of the redshift distribution r V

σ 0 0.7

− and sky projection around the proposed host cluster [WHL2012] / v where Npgal is a number of cluster members used for the calcula- g 1 0.6 J132045.4+211627 of SNF20070417-002 revealed that many of tion. the redshifts used to determine z cl come from galaxies that are First, we took all the galaxies attributed to each cluster in 2 0.5 more spread out – like a filament would be. We conclude that, literature sources and added the SNfactory host galaxy if it 3 0.4 consistent with the lack of X-rays, this is not a cluster. was not among them. Then, these data were combined with the 4 0.3 Two other clusters, ZwCl 2259+0746 and A87, also require Data Release 13 of the release database of the Sloan Digital . 0.2 discussion. Within 2 30 of the center of ZwCl 2259+0746 there is Sky Survey (SDSS) (Eisenstein et al. 2011; Dawson et al. 2013; 0 1 2 3 4 5 a source of X-ray emission, 1RXS J230215.3+080159. However, r/R200 Smee et al. 2013; SDSS Collaboration et al. 2016). We selected the size of the emission region (30) is very small in compari- all galaxies with spectroscopic redshifts located in a circle with Fig. 5. 5:Speed Speed normalized normalized by by velocity velocity dispersion dispersion within within the ensemble the en- son with R500 value for the cluster (400). In addition, according the center corresponding to the cluster coordinates and projected clustersemble vs. cluster the distance vs. the between distance galaxies between and ensemble galaxies clusterand ensemble normal- to Mickaelian et al.(2006), this emission belongs to a star. There- inside the R radius of the cluster. A 5σ redshift cut was 200 V izedcluster by R normalized200. The small by pointsR indicate. The small galaxies points with indicate spectroscopy galaxies from fore, we did not assign this X-ray source to ZwCl 2259+0746. adopted in the redshift direction (see Eq.7). SDSS. The big points represent200 the positions of host galaxies of our Another case is A87, which belongs to the A85/87/89 complex of SNewith Ia. spectroscopy The color bar from shows SDSS. the corresponding The big pointsg r representcolor; the the points positions of host galaxies of our SNe Ia. The color− bar shows the clusters of galaxies. According to Durret et al.(1998), the galaxy The R value was extracted from the literature when pos- filled with gray do not have color measurements. The solid lines show 200 corresponding g r color; the points filled with gray do not have velocities in the A87 region show the existence of subgroups, sible. For the clusters without published size measurements we the cuts we applied to associate SNe Ia with clusters, and the dashed color measurements.− The solid lines show the cuts we applied to which all have an X-ray counterpart and seem to be falling onto estimated R ourselves from the velocity distribution of galax- lines represent the prolongation of those cuts. 200 associate SNe Ia with clusters, and the dashed lines represent the A85 along a filament. Therefore, A87 is not really a cluster but ies around the cluster position following the procedure described prolongation of those cuts. a substructure of A85 that has a very prominent diffuse X-ray in Beers et al.(1990) with an initial guess of R200 = 1.1 Mpc. As it was mentioned in Sect. 3.1 there are several methods emission (Piffaretti et al. 2011). We applied our redshift measure- If the number of cluster members with spectroscopically deter- to identify a cluster. Initially we considered everything that is ment technique to determine the CMB redshift of the virialized mined redshifts was less than ten, the value of 1.1 Mpc was classified as a cluster by previous studies. However, some of region of A85. Thus, we included A85/A87 in our final table for adopted as a virial radius. This value corresponds to the average theseThe SNe classifications Ia that did not can satisfy be false. these For criteria the remaining were removed clusters from we the peculiar velocity analysis. R200 of clusters in the Meta-Catalog of X-Ray Detected Clusters checkedfurther consideration. for the presence of X-ray emission, a red sequence, or The final list of SNFACTORY SNe Ia in confirmed clusters of Galaxies (MCXC, Piffaretti et al. 2011); see Fig.3. the SZOur effect, final criteria as described are slightly below. different than those applied by contains 11 objects. The resulting association of SNe Ia with host 1 To estimate the redshift of a cluster we applied the so-called XavierWe et used al. 2013 the (1.5 public Mpc ROSAT and σV = All500 Sky km Surveys− ) and imagesDilday clusters is given in Table1. Column 1 is the SN name, Col. 2 1 biweight technique (Beers et al. 1990) on the remaining redshift withinet al. 2010 the (1 energy Mpc h band− and 0.1–2.4∆z = keV0.015). to These look forauthors extended stud- contains a name of the identified host cluster of galaxies, and distributions. Biweight determines the kinematic properties of X-rayied the counterparts properties and2. The rate expected of supernovae [0.1–2.4 in clusters keV] luminosity and their Col. 3 is the MCXC name. The MCXC coordinates of the host galaxy clusters while being resistant to the presence of outliers within R500 can be extracted from the luminosity–mass rela- cluster center are given in Col. 4. Column 5 contains the pro- choices were made to be consistent withα previous cluster SN Ia and is robust for a broad range of underlying velocity distribu- 7/3 L500 M500 jected separation, D, in Mpc between the SN position and the tionrateh measurements.(z)− 44 These1 = C values14 roughlywith characterizelog(C) = 0. an274 aver-and 10 erg s− 3 10 M tions, even if they are non-Gaussian, using the median and an × αage= cluster1.64 (see and Table we were 1 in guidedArnaud by et the al. 2010 same). thoughts The L whenvalues mak- for host cluster center. The R200 value is in Col. 6 and the CMB outlier rejection based on the median absolute deviation. More- 500 MCXCing the preliminaryclusters (Piffaretti cluster et selection al. 2011 (2.5) as Mpca function and ∆ ofz = redshift0.015, supernova redshift is in Col. 7. The CMB redshift of the cluster over, Beers et al. 1990 provided a formula for the cluster redshift aresee presented Sec. 3.1). in However, Fig.3. Moreover, since clusters in Fig. have3 a continuous different size black and and its uncertainty can be found in Cols. 8 and 9. The velocity uncertainty, but it cannot be used for clusters with few members. linevelocity represents dispersion, the minimum we determined value oforL extractedthat is from required the liter- for dispersion of the cluster estimated from the R200 value is shown Therefore, instead we used Eq.8, which can be applied for all of 500 in Col. 10. The number of galaxies that were used for cluster red- theature velocity the physical dispersion parameters of the of cluster each cluster to cause (R a200 deviationand σV ). from This our clusters. themethod Hubble provides diagram an greaterindividual than approach the intrinsic to each dispersion SN-cluster in lumi- pair shift calculation is in Col. 11. In Col. 12 we indicate the source For some of the clusters the literature provides only the fi- nosityand allows of SNe association Ia. The figure with a shows cluster that to beall defined the clusters with hosting greater of galaxy redshift information (lit. is an abbreviation for litera- nal redshift and the number of galaxies, Npaper, that were used SNeaccuracy. Ia except one are above this threshold and it is therefore very ture). In the last Col., we summarize all references for the cluster in the calculation, without publishing a list of cluster members. likelyFollowing that the DopplerCarlberg effect et al. induced(1997) by and these Rines clusters & Diaferio causes a coordinates, R200, and non-SN galaxy redshifts. In those cases, if the number of members collected by us satis- dispersion(2006) wein constructed the Hubble an diagram ensemble that cluster is greater from than all the the clusters intrin- fies N < N we adopted the redshift from literature. The gal paper sicassociated dispersion with in SNe luminosity Ia to smooth of SNe over Ia. Moreover, the asymmetries more than in the a 4. Impact on the Hubble diagram detailed scheme of the cluster redshift calculation is presented in halfindividual of the clusters. low redshift We scaled clusters the are velocities above this by σ limit,V and indicating positions Fig.4. thatwith the the peculiar values of velocityR200 for correction each cluster has to to produce be taken the into Fig. account5. This Since we have a list of 11 SNe Ia that belong to clusters, we can All the calculations described above are based on spectro- ifshows a SN our Ia belongs selection to boundaries a cluster of and galaxies exhibits and good is observed separation at low of apply peculiar velocity corrections and study how they affect the scopical redshifts. Before performing the calculations of the redshift.cluster galaxies from surrounding galaxies. HRs. The following method is implemented. cluster CMB redshift, all of the heliocentric redshifts of its mem- As it was mentioned in Sect. 3.1 there are several methods The theoretical distance modulus is µ th = 5 log d 5, To check for a linear red sequence feature, SDSS data were 10 L − bers were first transformed to the CMB frame. The transforma- employed.to identify From a cluster. the SDSS InitiallyGalaxy we consideredtable we chose everything all the galax-that is where dL is the true luminosity distance in parsecs, and tion to the CMB frame made use of the NASA/IPAC Extragalac- classified as a cluster by previous studies. However, some of ies in the R200 region around the cluster position. We extracted zc tic Database (NED). these classifications can be false. For the remaining clusters we c dzc0 model magnitudes, as recommended by SDSS for measuring rmdL = (1 + zh) , (9) checked for the presence of X-ray emission, a red sequence, or H 3 colors of extended objects. 0 0 ΩΛ + Ωm(1 + zc0 ) the SZ effect, as described below. Z 3.3. Final matching and confirmation We checked for detections of the SZ effect using the Planck catalogWe of used Sunyaev-Zel’dovich the public ROSAT sources All (Planck Sky Survey Collaboration images where zh is the heliocentricp redshift, which takes into account the fact that the observed flux is affected not only by the Once the redshifts and R200 values were obtained for each clus- XXVIIwithin 2016 the energy). All the band clusters 0.1-2.4 in our keV sample to look with for SZ extended sources 2 ter, we performed the final matching. A supernova is considered alsoX-ray have counterparts X-ray emission,. The as expected expected [0.1-2.4 for real clusters. keV] luminosity cosmological redshift but by the Doppler effect as well. a cluster member if the following two conditions are satisfied: within R500 can be extracted from the luminosity-mass relation We assign the cosmological redshift zc to be Some of our supposed clustersα do not show X-ray or SZ 7/3 L500 M500 signaturesh(z)− of44 a cluster.1 = C As described14 with in Sect. log(C) 3.1,= low0.274 redshift and cl 10 ergs− 3 10 M z , if inside a galaxy cluster, r < R200, where r is the projected distance between the SN × c • 2 and cluster center 2 http://www.xray.mpe.mpg.de/cgi-bin/rosat/http://www.xray.mpe.mpg.de/cgi-bin/rosat/ zc = (10)  host host cl σV z , otherwise. z z < 3 rosat-survey  c •| − | c   A162, page 6 of 12 Article number, page 5 of 13  P.-F. Léget et al.: Type Ia supernovae and Galaxy clusters

Table 1. Association of the SNFACTORY SNe Ia with host clusters.

a host cl cl σ SN name Host cluster MCXC name Cluster coordinates r R200 zc zc zerR200 VR200 Ngal Source Ref. (Mpc) (Mpc) (km/s) SNF20051003 004/SN2005eu RXJ0228.2+2811 J0228.1+2811 02 28 09.6+28 11 40 0.24 0.92 0.0337 0.0340 0.0015 644 2 lit. 1, 2, 3 − SNF20060609 002 A2151a J1604.5+1743 16 04 35.7+17 43 28 0.64 1.16 0.0399 0.0359 0.0002 812 146 SDSS+lit. 1, 4 − SNF20061020 000 A76 J0040.0+0649 00 40 00.5+06 49 05 0.72 1.06 0.0379 0.0380 0.0008 742 9 SDSS+lit. 1, 5 − SNF20061111 002 RXC J2306.8-1324 J2306.8 1324 23 06 51.7 13 24 59 0.66 1.08 0.0677 0.0647 0.0018 756 2 lit. 1, 6 − − − SNF20080612 003 RXC J1615.5+1927 J1615.5+1927 16 15 34.7+19 27 36 0.52 0.76 0.0328 0.0311 0.0004 532 19 SDSS 1 − SNF20080623 001 ZwCl8338 J1811.0+4954 18 11 00.1+49 54 40 1.02 1.17 0.0448 0.0493 0.0005 819 36 lit. 1, 4 − SNF20080731 000 ZwCl 1742+3306 J1744.2+3259 17 44 15.0+32 59 23 0.34 1.55 0.0755 0.0755 0.0026 1085 2 lit. 1, 7 − PTF09foz A87/A85 J0041.8 0918 00 41 50.1 09 18 07 2.23 1.84 0.0533 0.0546 0.0004 1288 148 SDSS 1, 8 − − SN2006X Virgo J1230.7+1220 12 30 47.3+12 20 13 1.19 1.14 0.0063 0.0045 0.0001 798 607 SDSS+lit. 1, 9, 10 SN2007nq A119 J0056.3 0112 00 56 18.3 01 13 00 1.11 1.43 0.0439 0.0431 0.0003 1001 153 SDSS+lit. 1, 4, 11 − − SN2009hi A2589 J2323.8+1648 23 23 53.5+16 48 32 0.10 1.33 0.0399 0.0401 0.0004 931 54 SDSS+lit. 1, 4, 12

(a) Notes. The value was calculated from R500 with equation R200 = 1.52 R500 (Reiprich & Böhringer 2002; Piffaretti et al. 2011). References. (1) Piffaretti et al.(2011); (2) Wegner et al.(1993); (3) Li(2005); (4) Smith et al.(2004); (5) Hudson et al.(2001); (6) Cruddace et al. (2002); (7) Ulrich(1976); (8) Nugent et al.(2009); (9) Suzuki & Migliardi(2006); (10) Kim et al.(2014); (11) Quimby et al.(2007); (12) Nakano et al.(2009).

The uncertainty on zc (both SN Ia and host cluster) is propagated hosts inside the clusters are taken into account (wRMS = 0.130 tot2 0.038 mag). When using the redshift of the host instead of the± into the magnitude error σi as redshift of the cluster, the dispersion of these 11 SNe Ia is σ tot2 = σ 2 + σ 2 + σ 2 , (11) wRMS = 0.137 0.036 mag (see Fig.6). In order to compute the i LCi z int significance of this± improvement, the Pearson correlation coeffi- σ cient and its significance between HR before the correction and where LCi is the propagation of uncertainty from light curve cl host parameters to an apparent magnitude of SN Ia in the B-band, 5 log10(z /z ) are computed. The Pearson correlation coeffi- σ cient is ρ = 0.9 0.1, and its significance is 3.58σ, which is and m∗B, int is the unknown intrinsic dispersion of SN Ia. The ± value σz is the uncertainty on redshift measurement and peculiar significant. In order to cross-check this significance, we did a velocity correction (see Eq. (3)), which is assigned as Monte Carlo simulation. For each simulation, we took the difference z cl z host for the 11 SNe Ia in clusters and then randomly − 5 √z cl 2 applied these corrections to the same 11 SNe Ia. For each simula- err , z cl ln(10) if inside a galaxy cluster, tion, we examined how often we get a wRMS less than or equal to σz =  (12) the observed wRMS after the fake random peculiar velocity cor-  host 2 2  5 √zerr +0.001 rection. On average the wRMS is higher and the probability to  , otherwise.  z host ln(10) w . 4  have the same or lower dispersion in RMS is 5 9 10− , which  is in agreement with Pearson correlation significance.×  1 The 0.001 value corresponds to the 300 km s− that is added Even though the p-value is low, we still need to clarify why to the redshift error of SNe Ia outside the clusters to take into the decrease in wRMS is not higher. In order to examine whether account the unknown galaxy peculiar velocities, as in a classical the corrections are consistent with what it is expected, we com- cosmological analysis. For cases in which a SN Ia belongs to a pute the distribution of the pull of peculiar velocities and the galaxy cluster, we assume that the redshift error contains only expected distribution of HRs of our correction. These two dis- the error from the redshift measurement of a cluster. tributions are shown, respectively, in Figs.7 and8. For the By fitting the Hubble diagram using only SNe Ia out- pull distribution shown in Fig.7, which is defined as the dis- side the galaxy clusters3, we obtained SN Ia SALT2 nuisance tribution of difference between the host galaxy redshift and the parameters: α and β, the classical standardization parameters host galaxy clusters redshift, divided by the peculiar velocity for light curve width and color, respectively; and the absolute dispersion within the cluster, we should expect to get a cen- magnitude M , and intrinsic dispersion. These nuisance param- B tered normal distribution with a standard deviation of unity. eters remained fixed during our analysis. Once the nuisance The standard deviation of the pull is 0.82 0.18, which is parameters were estimated, we computed the difference between consistent with the expected unity distribution± of the pulls. In observed and theoretical distance modulus (HRs). In order to addition, we showed in Fig.8 the expected distribution of the study the impact of peculiar velocity correction, we computed correction, the expected distribution of the correction convolved the HRs for the SNe Ia in clusters before and after correction. with uncertainties on HR, and the observed distribution of the We used the weighted root mean square (wRMS ) as defined in correction. It is seen that the observed distribution of the cor- Blondin et al. 2011 to measure the impact of this correction. We rections and the predicted distribution of the corrections are used the same intrinsic dispersion established during the fitting consistent. (σ = 0.10 mag) to calculate all wRMS . SN2006X was not int To resume, the Pearson correlation coefficient and its signif- taken into account during the computation of the wRMS because icance, the distribution of the pull, and the comparison between it does not belong to the set of so-called normal SNe Ia. How- the expected correction and observed correction show that our ever, SN2006X is included in the statistical tests described below correction is consistent with expectations given the cluster veloc- (for details see Sect. 5.1). ity dispersions and uncertainty in SN Ia luminosity distance. The dispersion of these 11 SNe Ia around the Hubble dia- w gram decreases significantly when the peculiar velocities of their In addition, the RMS we found for SNe Ia inside the clusters before correction, 0.137 0.036 mag, is also smaller than the ± 3 Taking into account all the SNe Ia does not affect the Hubble diagram wRMS for the SNe Ia in the field (wRMS = 0.151 0.010 mag). fitting because the number of SNe Ia inside galaxy clusters is small. This is consistent with a statistical fluctuations,± but could be

A162, page 7 of 12 A&A proofs: manuscript no. SNIa_in_Clusters

A&A proofs: manuscript no. SNIa_in_Clusters wRMS=0.151 0.010A&A mag 615, A162 (2018) SNe Ia inside clusters, before correction ± wRMS=0.137 0.036 mag 0.4 SNe Ia inside clusters, after correction ± wRMS=0.130 0.038 mag SNe Ia outside clusters ± wRMS=0.151 0.010 mag SNe Ia inside clusters, before correction ± 0.3 wRMS=0.137 0.036 mag 0.4 SNe Ia inside clusters, after correction ± wRMS=0.130 0.038 mag SNe Ia outside clusters ± 0.2 0.3

0.1 0.2

µ 0.0 ∆ 0.1

0.1 µ 0.0

− ∆

0.2 0.8 − SN2006X 0.1 − − 1.2 − 0.3 µ ∆ 0.8 − 1.6 0.2 − SN2006X − − 1.2 2.0 −

0.4 − µ 0.002 0.004 0.006 0.008 0.3 − ∆ 1.6 zc − −

2.0 0.01 0.02 0.03 0.04 0.05 0.06 0.407 − 0.08 0.09 0.002 0.004 0.006 0.008 zc − zc Fig. 6: Hubble diagram residuals. For cluster members red circles (blue squares) and histograms0.01 0. correspond02 0.03 to residuals0.04 for0 SNe.05 Ia in0.06 0.07 0.08 0.09 galaxy clusters before (after) correction for peculiar velocities of the hosts inside their clusters. The black histogram correspondszc to all SNe Ia after correction. SN2006X is presented in the inset plot separately from the others owing to its very large offset. Fig.Fig. 6. 6:Hubble Hubble diagram diagram residuals. residuals. For For cluster cluster members members red red circles circles (blue (blue squares) squares) and histograms and histograms correspond correspond to residuals to residuals for SNe for Ia SNe in galaxy Ia in clustersgalaxy beforeclusters (after) before correction (after) correction for peculiar for velocities peculiar of velocities the hosts ofinside the hoststheir clusters. inside their The clusters.black histogram The black correspondsP.-F. histogram Léget &to SNfactory: allcorresponds SNe Ia Typeafter to Ia supernovae and Galaxy clusters correction.all SNe Ia SN2006X after correction. is presented SN2006X in the inset is presented plot separately in the from inset the plot others separately owing to fromits very the large others offset. owing to its very large offset. in Fig.8 the expected distribution of the correction, the expected Despite the low significance of their smaller dispersion, we distribution of the correction convolved with uncertainties on 5 4.0 could expect some difference between SNe Ia inside and outside RMS = 0. 82 0. 18 Changes expected based on Cluster V200 HR, and the observed distribution of the correction. It is seen ± clusters because the properties of the galaxies inside the clus- that the observed distribution of the corrections and the predicted in Fig.8 the expected distribution of theobserved correction, pull distribution the expected 3.5 Adding convolution with HR errors ters are known to be different from those in the field. While in distribution of the corrections are consistent. distribution4 of the correction convolved with uncertainties on 5 the field all morphological types of the galaxies are observed, 3.0 RMS = 0. 82 0. 18 To resume, the Pearson correlation coefficient and its signif- HR, and the observed distribution of the correction. It is seen ± the central parts of the clusters usually contain a large percent- icance, the distribution of the pull, and the comparison between that the observed distribution of the corrections and the predicted observed pull distribution age of elliptical galaxies. The oldest stars, with ages compara- 2.5 the expected correction and observed correction show that our distribution3 of the corrections are consistent. 4 ble to those of the Universe, lie in elliptical/lenticular galax- To resume, the Pearson correlation coefficient and its signif- correction is consistent with expectations given the cluster ve- # 2.0 ies. Moreover, dust is often absent in these regions. As shown icance, the distribution of the pull, and the comparison between # locity dispersions and uncertainty in SN Ia luminosity distance. 2 3 by previous studies, narrow light curve SNe Ia are preferen- In addition, the wRMS we found for SNe Ia inside the clus- the expected correction and observed correction show that our 1.5 tially hosted by galaxies with little or no ongoing star forma- ters before correction, 0.137 0.036 mag, is also smaller than correction is consistent with expectations given the cluster ve- # tion, and usually occur in more massive galaxies (Hamuy et al. ± 1.0 the wRMS for the SNe Ia in the field (wRMS = 0.151 0.010 locity dispersions1 and uncertainty in SN Ia luminosity distance. 2 1995, 1996b; Riess et al. 1999; Hamuy et al. 2000; Sullivan mag). This is consistent with a statistical fluctuations, but± could In addition, the wRMS we found for SNe Ia inside the clus- et al. 2003, 2006, 2010; Neill et al. 2009; Smith et al. 2012; ters before correction, 0.137 0.036 mag, is also smaller than 0.5 Johansson et al. 2013; Hill et al. 2016; Henne et al. 2017). In- be owing to a lower intrinsic luminosity dispersion for SNe Ia in- ± the wRMS0 for the SNe Ia in the field (wRMS = 0.151 0.010 1 deed, if we examine Fig.9, we see that 11 SNe Ia found in side galaxy clusters. This possibility is explored in the Sect. 5.2. 3 2 1 0 1 2 ± 3 0.0 mag). This is consistent with a statisticalzhost zcl fluctuations, but could 0.8 0.6 0.4 0.2 0.0 0.2 0.4 0.6 0.8 Pull = c σ− clusters are consistent with those studies, SNe Ia with higher × V HRb HRa be owing to a lower intrinsic luminosity dispersion for SNe Ia in- | | − | | X1 belong to the hosts with higher local specific star formation 0 5. Discussion Fig.side 7. galaxyVelocity clusters. pull Thisdistribution possibility (in blue) is explored in comparison in the Sect. with 5.2 a. 3 2 1 0 1 2 3 rate (sSFR) and smaller Mstellar. The properties of 48 SNe Ia in Fig. 7: Velocity pull distribution (in blue) in comparison with a Fig.Fig. 8. 8:Distribution Distribution of of the the difference difference inzho absolutes int absolutezcl HR HR after after (HRa ()HR anda) Gaussian distribution with the observed standard distribution of the Pull = c σ− clusters versus 1015 SNe Ia in the field were studied in Xavier beforeand before (HRb) peculiar (HR ) velocitypeculiar correction velocity× (in correctionV blue). The (in black blue). line rep- The 5.1. SN2006X velocityGaussian pull. distribution This is compatible with the with observed the expected standard standard distribution deviation of b et al.(2013), who found the following mean values for SN the velocity pull. This is compatible with the expected standard resentsblack linethe expected represents distribution the expected of the distribution difference in of HR, the and diff theerence red of5. unity. Discussion = . . . . Throughout the analysis, we treated SN2006X in a special way deviation of unity. curveFig.in HR, 7: is Velocity and the expected the red pull curve change distribution is convolved the expected (in blue) with change in error comparison distribution. convolved with with The a LC parameters: X1 0 14 0 04 (field), 0 40 0 20 (clus- results are compatible with the observed distribution given the Poisson ± − ± because this SN Ia is highly reddened SN, i.e., it is associated Gaussianerror distribution. distribution The with results the areobserved compatible standard with distribution the observed of ters), and C = 0.011 0.004 (field), and 0.03 0.02 (clus- owing5.1. SN2006X to a lower intrinsic luminosity dispersion for SNe Ia inside uncertainties of each histogram bin. − ± − ± with dusty local environment (Patat et al. 2007). This SN Ia af- the velocity pull. This is compatible with the expected standard ters). For comparison our means are X1 = 0.01 0.09 (field), galaxy clusters. This possibility is explored in the Sect. 5.2. distribution given the Poisson uncertainties of each histogram − ± fects the interstellar medium and exhibits very high ejecta ve- Throughout the analysis, we treated SN2006X in a special way deviation of unity. 0.65 0.36/ 0.56 0.34 (clusters without/with SN2006X), and bin. − ± − ± locities and a light echo (Patat et al. 2009). These special fea- Whilebecause SN2006X this SN canIa is bias highly the dispersion,reddened SN, only i.e., the it di isfference associated be- features put it very far off the Hubble diagram, and makes C = 0.01 0.01 (field), 0.02 0.03/0.13 0.11 (clusters with- tures put it very far off the Hubble diagram, and makes this SN 5.tweenwith Discussion dusty the residuals local environment before correction (Patat et for al. 2007 peculiar). This velocity SN Ia and af- this SN unsuitable for cosmological analysis. However, it was out/with SN2006X).± The correlation± between± HRs for 11 SNe in fects the interstellar medium and exhibits very high ejecta ve- unsuitable for cosmological analysis. However, it was included 5.1.after SN2006X correction for peculiar velocity is taken into account in included in the analysis because we are interested in the impact clusters and the mass of their host galaxy is the same as shown in the analysis because we are interested in the impact of pecu- thelocities computation and a light of echo the significance (Patat et al. of 2009 the). signal. These This special correc- fea- ofWhile peculiar SN2006X velocities can bias within the dispersion, galaxy clusters, only the not diff cosmologyerence be- in Fig. 15 of Xavier et al.(2013). 0.7 magnitude correction improves the dispersion on the Hub- liar velocities within galaxy clusters, not cosmology alone, and it Throughouttiontures for put SN2006X it very the analysis, far is off aroundthe we Hubble treated550 diagram, kmSN2006X s 1 in and velocityin makes a special and this way has SN alone,tween and the it residuals passes the before light correctioncurve quality for criteria peculiar defined velocity in Guy and − ble∼ diagram. Indeed, the original Hubble residual was measured passes the light curve quality criteria defined in Guy et al.(2010). becauseaunsuitable huge impact this for SN cosmologicalon Ia magnitude is highly analysis. at∼ reddened nearby However, redshift. SN, that Init is, was this it includedis case asso- the etafter al.(2010 correction). While for SN2006X peculiar velocitycan bias isthe taken dispersion, into account only the in We also performed a morphological classification of the as 1.7 mag when using the host galaxy redshift instead of ciatedin the withanalysis dusty because local we environment are interested (Patat in the et al. impact 2007 of). pecu- This differencethe∼ computation − between of the the residuals significance before of the correction signal. This for peculiar correc- hosts (see Table2) based on the information provided by SIM- the redshift of the galaxy cluster, whereas1 the Hubble residual is Article number, page 8 of 13 SNliarIa velocities affects within the interstellar galaxy clusters, medium not and cosmology exhibits alone, very and high it velocitytion for andSN2006X after correction is around for550 peculiar km s− velocityin velocity is taken and into has BAD and HyperLeda databases (Wenger et al. 2000; Makarov 1.0 mag. This correction is∼ <50% of the original offset, and ejectapasses velocities the light curveand a lightquality echo criteria (Patat defined et al. 2009 in Guy). These et al.( special2010). accounta∼ huge − impact in the on computation magnitude ofat nearby the significance redshift. In of this the case signal. the et al. 2014) and images from Childress et al.(2013). The host of smaller than the corrected residual from stretch and color only. SNF20080612-003 is classified as elliptical by HyperLeda and A162,Article page number, 8 of 12 page 8 of 13 Considering the importance of the correction for SN2006X as spiral by Sternberg et al.(2011). However, the classification and the fact that this object is peculiar, it makes sense to cal- by Sternberg et al.(2011) is based on images from Digital Sky culate the significance of the peculiar velocity correction when Survey. This host looks elliptical without any sign of spiral arms SN2006X is not taken into account. Without SN2006X, the Pear- on the SDSS image. Therefore, we assigned this galaxy to ellip- son correlation coefficient decreases substantially to ρ = 0.5 0.3 tical as in HyperLeda. We found that four SNe belong to ellip- with a signifcance of 1.34 σ. Moreover, by carrying out the same± tical/lenticular galaxies while the other seven are located in spi- Monte-Carlo simulation as in Sect.4 for the remaining cluster rals. All of the early-type (elliptical and lenticular) galaxies fall 4 2 SNe Ia, the p-value changes from 5.9 10− to 6.6 10− , which on the red sequence for their clusters (see the color-magnitude is in agreement with Pearson correlation× significance.× Thus, re- diagrams (g r vs. r) for the clusters within the SDSS footprint moving an object for which the correction is large decreases the in Fig. 10). For− the most part the spiral hosts are very close to significance of the correction, especially given the small sample the red sequence as well, i.e., these galaxies are characterized by size. redder colors.

In Figs.9 and 11 we also show how the peculiar velocity cor- 5.2. Physical properties of SNe Ia and their hosts in galaxy rection c ∆z and the absolute change in HRs due to peculiar ve- | | clusters locity correction depend on the supernova parameters X1 and C, host properties such as local sSFR, stellar mass, morphological In Sect.4 it was shown that the wRMS around the Hubble dia- type, the difference between (g r) of the host and corresponding gram for the SNe Ia in clusters is less than for SNe Ia in the field, (g r) of the red sequence (RS− residuals), relative SN position − which suggests that SNe Ia in clusters might represent a more inside the cluster, and cluster mass M200 (Childress et al. 2013; “standard” subclass of SNe Ia (see Fig.6). In order to compute Brown et al. 2014; Rigault et al. 2018). The c ∆z plot shows that the significance of this lower dispersion we perform 106 Monte most of the SNe whose redshifts are significantly| | changed have Carlo simulations. For each simulation, we randomly select 11 X 0 and are hosted by blue spiral galaxies that have high local 1 ' SNe Ia in our sample and compute the wRMS . For all the sim- sSFR and smaller Mstellar, r/R200 0.7 (see Fig.9). This is con- ulations we compute how often the dispersion is lower than the sistent with the distribution of galaxies' in clusters such that the dispersion of wRMS =0.130 0.038 mag observed inside clusters massive, elliptical, and passive galaxies are located in the center after the peculiar velocity correction.± In this case, the probability but outer region contains spiral galaxies as well and with veloc- 1 to have such a low dispersion is 3.8 10− , which is not signifi- ity profiles inside the clusters (see Fig.5, Carlberg et al. 1997, cant. × their Fig. 1, and Rines & Diaferio 2006, their Fig. 15).

Article number, page 9 of 13 P.-F. Léget et al.: Type Ia supernovae and Galaxy clusters

Table 2. Properties of host galaxies of SNe Ia belonging to galaxy clusters.

SN name Host name Host type log(LsSFR) log(Mstellar) SNF20051003 004 NSFJ022743.32+281037.6 Sab 10.53 9.01 SNF20060609−002 MCG+03 41 072 Sbc −10.79 10.19 SNF20061020−000 2MASXJ00410521+0647439− − Sab −13.07 10.26 SNF20061111 −002 ... Sb − 9.85 9.02 SNF20080612− 003 2MASXJ16152860+1913344 E −11.15 10.17 SNF20080623−001 WINGSJ181139.70+501057.1 Sc −10.39 8.86 SNF20080731−000 ... Sb −11.87 10.14 PTF09foz− 2MASXJ00421192 0952551 S0 −13.31 10.49 SN2006X NGC 4321− Sbc− — — SN2007nq UGC 595 E 11.26 12.12 SN2009hi NGC 7647 E −12.54 11.51 P.-F. Léget & SNfactory: Type Ia supernovae and Galaxy clusters− 1 2 Notes. LsSFR (yr− kpc− ) – local speciﬁc SFR (SFR per unit galaxy stellar mass; Rigault et al. 2018), Mstellar (M ) is the host galaxy stellar mass (Childress et al. 2013).

1.6 1.6 Considering the importance of the correction for SN2006X 1.2 1.2 -10 and0 the.2 fact that this object0.2 is peculiar, it makes sense-10 to 0.8 0.8 calculate0.0 the significance of0.0 the peculiar velocity correction 0.4 0.4 when SN2006X is not taken into account. Without SN2006X, 0.2 0.2 0.0 0.0 the− Pearson correlation coefficient− decreases substantially to 3 2 1 0 1 0.1 0.0 0.1 0.2 ρ = . 3 2. 1 0 1 0.1 0..0 σ0.1 0.2 − − − − 0−5 −0 3 −with a signifcance− of 1 34 . Moreover, by car- X1 C ± X1 C 1.6 1.6 rying out the same Monte-Carlo simulation as in Sect.4 for the 4 1.2 1.2 remaining0.2 cluster SNe Ia, the0.2P-value changes from 5.9 10− -11 . 2 ×-11 0.8 0.8 to 6 6 10− , which is in agreement with Pearson correlation significance.0.0× Thus, removing0 an.0 object for which the correction 0.4 0.4 ]

1 0.2 0.2

is| large decreases the signiﬁcance of the correction, especially − 0.0 0.0 − − 15 14 13 12 11 10 9 9 10 11 12 givencorr the15 small14 13 sample12 11 10 size.9 9 10 11 12 − − − − − − − − − − − − − − log(LsSFR) log(Mstellar) HR log(LsSFR) log(Mstellar) 1.6 1.6 | − | log(LsSFR) log(LsSFR) [1000 km s 5.2. Physical properties of SNe Ia and their hosts in |

z 1.2 1.2 0.2 0.2 HR | ∆

| galaxy clusters c 0.8 0.8 -12 0.0 0.0 -12 0.4 0.4 In Sect.0.2 4 it was shown that the0.2 wRMS around the Hubble dia- 0.0 0.0 gram− for the SNe Ia in clusters− is less than for SNe Ia in the field, E S0 Sab Sb Sbc Sc 0.4 0.3 0.2 0.1 0.0 E S0 Sab Sb Sbc Sc 0.4 0.3 0.2 0.1 0.0 − − − − − − − − Morphology RS residuals which suggestsMorphology that SNe Ia in clustersRS residuals might represent a more 1.6 1.6 “standard” subclass of SNe Ia (see Fig.6). In order to compute 6 1.2 1.2 the significance0.2 of this lower0 dispersion,.2 we perform 10 Monte 0.8 0.8 Carlo simulations. For each simulation, we randomly select -13 0.0 0.0 -13 0.4 0.4 11 SNe Ia in our sample and compute the wRMS . For all the 0.2 0.2 0.0 0.0 simulations− we compute how− often the dispersion is lower than 0.0 0.4 0.8 1.2 14.0 14.5 15.0 the dispersion0.0 0.4 of0.w8RMS1.2 = 0.130 140.0038 14mag.5 observed15.0 inside ± r/R200 log(M200) clusters after ther/R200 peculiar velocity correction.log(M200) In this case, the 1 probability to have such a low dispersion is 3.8 10− , which is Fig. 9. Peculiar velocity correction, c ∆z , for SNe Ia that belong to × | | not significant. clusters, as a function of supernova parameters (X1, C; triangles), host Fig. 9: Peculiar velocity correction,1 2c ∆z , for SNe Ia that be- Fig.Despite 11: Absolute the low change significance in HRs due of their to peculiar smaller velocity dispersion, correc- we properties (local specific SFR (yr− kpc− ),| stellar| mass (M ), morpho- longlogical to type, clusters, RS residuals as a function [(g r) of( supernovag r) ]; circles; parameters Childress (X1 et, C al.; tioncould for expect SNe Ia some that belongdifference to clusters between as SNe a function Ia inside of and supernova outside RS 1 2 triangles),2013; Brown host et al. properties 2014; Rigault (local− et− al. specific 2018− ), relative SFR (yr SN− positionkpc− ), inside stel- parametersclusters because (X1, C the; triangles), properties host of theproperties galaxies (local inside specific the clusters SFR 1 2 larthe mass cluster (M and), cluster morphological mass M200 ( type,M ); squares. RS residuals The colorbar [(g r shows) (g the (yrare− knownkpc− ), to stellar be different mass (M from), morphological those in the field. type, While RS residu- in the − − − rcorresponding)RS ]; circles, localChildress specific et SFR. al. 2013; Brown et al. 2014; Rigault alsfield [(g all morphologicalr) (g r)RS ]; types circles, of theChildress galaxies etare al. 2013 observed,; Brown the − − − et al. 2018), relative SN position inside the cluster and cluster etcentral al. 2014 parts; Rigault of the et clusters al. 2018 usually), relative contain SN position a large percentage inside the mass M200 (M ); squares. The colorbar shows the correspond- clusterof elliptical and cluster galaxies. mass TheM200 oldest(M ); stars, squares. with The ages colorbar comparable shows to 1 ingThis local correction specific for SFR. SN2006X is around 550 km s− in veloc- thethose corresponding of the Universe, local lie specific in elliptical/lenticular SFR. galaxies. More- ity and has a huge impact on magnitude∼ at nearby redshift. In over, dust is often absent in these regions. As shown by previous this case the 0.7 magnitude correction improves the dispersion studies, narrow light curve SNe Ia are preferentially hosted by on the Hubble∼ diagram. Indeed, the original HR was measured galaxies with little or no ongoing star formation, and usually as approximatelySince the majority1.7 ofmag galaxies when inusing the theUniverse host galaxy are not redshift found ficeoccur of High in more Energy massive Physics galaxies of the U.S. (Hamuy Department et al. of Energy1995, 1996b under Contract, 2000; ininstead galaxy of clusters, the redshift− but in of filamentary the galaxy structures cluster, whereas such as the the HRGreat is No.Riess DE-AC025CH11231. et al. 1999; Sullivan Support et in al. France 2003 was, 2006 provided, 2010 by; CNRS Neill/IN2P3, et al. CNRS/INSU, and PNC; LPNHE acknowledges support from LABEX ILP, sup- Wallapproximately (Geller & Huchra1.0 mag. 1989 This), SNecorrection Ia in galaxy is <50% clusters of the areoriginal rare 2009; Smith et al. 2012; Johansson et al. 2013; Hill et al. 2016; − ported by French state funds managed by the ANR within the Investissements inoffset, untargeted and smaller searches than such the as corrected SNfactory residual. Next from decade stretch surveys and d’AvenirHenne programme et al. 2017 under). Indeed, reference if ANR-11-IDEX-0004-02. we examine Fig.9, we NC see is grateful that 11 to suchcolor as only. the Zwicky Transient Facility (ZTF) or the Large Synop- theSNe LABEX Ia found Lyon in Institute clusters of Origins are consistent (ANR-10-LABX-0066) with those studies, of the University SNe Ia tic Survey Telescope (LSST) (Bellm 2014; LSST Science Col- de Lyon for its financial support within the program "Investissements d’Avenir" (ANR-11-IDEX-0007) of the French government operated by the National Re- laboration et al. 2009) will observe thousands of SNe Ia and search Agency (ANR). Support in Germany was providedA162, by DFG page through 9 of 12 therefore have much larger samples of SNe Ia in clusters. These TRR33 "The Dark Universe" and by DLR through grants FKZ 50OR1503 and can be used to study dependencies between SNe Ia and host FKZ 50OR1602. In China support was provided by Tsinghua University 985 clusters with greater certainty. LSST will be much deeper than grant and NSFC grant No 11173017. Some results were obtained using re- factory sources and support from the National Energy Research Scientific Computing SN or ZTF, so the method of cluster selection based only Center, supported by the Director, Office of Science, Office of Advanced Scien- on the presence of X-rays will not be viable until much deeper tific Computing Research of the U.S. Department of Energy under Contract No. all-sky X-ray surveys are performed. Even though the impact of DE-AC02- 05CH11231. We thank the Gordon & Betty Moore Foundation for peculiar velocities decreases with distance and becomes negligi- their continuing support. Additional support was provided by NASA under the ble at high redshifts, SN Ia rates in clusters (Sharon et al. 2010; Astrophysics Data Analysis Program grant 15-ADAP15-0256 (PI: Aldering). We also thank the High Performance Research and Education Network (HPWREN), Barbary et al. 2012) and the difference in SN light curve param- supported by National Science Foundation Grant Nos. 0087344 & 0426879. This eters inside and outside the clusters could be fruitful avenues of project has received funding from the European Research Council (ERC) under investigation for future cosmological analyses. the European Union’s Horizon 2020 research and innovation programme (grant agreement No 759194 - USNAC). PFL acknowledges support from the National Acknowledgements. We thank the technical staff of the University of Hawaii 2.2 Science Foundation grant PHY-1404070. MVP acknowledges support from Rus- m telescope and Dan Birchall for observing assistance. We recognize the signif- sian Science Foundation grant 14-12-00146 for the selection of SNe exploded in icant cultural role of Mauna Kea within the indigenous Hawaiian community, galaxy clusters. This research has made use of the NASA/IPAC Extragalactic and we appreciate the opportunity to conduct observations from this revered Database (NED), which is operated by the Jet Propulsion Laboratory, California site. This work was supported in part by the Director, Office of Science, Of- Institute of Technology, under contract with the National Aeronautics and Space

Article number, page 11 of 13 A&A proofs: manuscript no. SNIa_in_Clusters

SN Name Host Name Host Type log(LsSFR) log(Mstellar) SNF20051003-004 NSFJ022743.32+281037.6 Sab 10.53 9.01 SNF20060609-002 MCG+03-41-072 Sbc −10.79 10.19 SNF20061020-000 2MASXJ00410521+0647439 Sab −13.07 10.26 SNF20061111-002 ... Sb − 9.85 9.02 SNF20080612-003 2MASXJ16152860+1913344 E −11.15 10.17 SNF20080623-001 WINGSJ181139.70+501057.1 Sc −10.39 8.86 SNF20080731-000 ... Sb −11.87 10.14 PTF09foz 2MASXJ00421192-0952551 S0 −13.31 10.49 SN2006X NGC 4321 Sbc− — — SN2007nq UGC 595 E 11.26 12.12 SN2009hi NGC 7647 E −12.54 11.51 − 1 2 Table 2: The properties of host galaxies of SNe Ia belonging to galaxy clusters. LsSFR (yr− kpc− ) — local speciﬁc SFR (SFR per unit galaxy stellar mass; Rigault et al. 2018), Mstellar (M ) is the host galaxy stellar mass (Childress et al. 2013).

A&A 615, A162 (2018)

2 SN2009hi PTF09foz SNF20060609-002

0 r − g

2 SNF20080612-003 SNF20061020-000 SN2007nq

12 14 16 18 20 12 14 16 18 20 12 14 16 18 20 r P.-F. Léget & SNfactory: Type Ia supernovae and Galaxy clusters Fig.Fig. 10. 10:Color-magnitude Color-magnitude diagram diagram (g r (gvs. rr) plottedvs. r) forplotted the clusters for the from clusters Table1 from for the Table six clusters1 for the for six which clusters SDSS for galaxy which redshifts SDSS and galaxy colors − areredshifts available and (Eisenstein colors are et availableal. 2011; Dawson (Eisenstein− et al. 2013 et al.; Smee 2011 et; Dawson al. 2013; SDSS et al. 2013 Collaboration; Smee et2017 al.). 2013 Red points; SDSS show Collaboration the positions et of al. supernova 2016). hosts,Red points most of show which the are positions located near of supernova the red sequence. hosts, most of which are located near the red sequence.

1.6 1.6 with higher X1 belong to the hosts with higher local specific star formation1.2 rate (sSFR) and1 smaller.2 M . The properties-10 of 0.2 0.2 -10 stellar factory 48 SNeThe0.8 Ia small in clusters size of versus our sample 10150.8 SNe does Ia not in the allow field us were to perform studied match0.0 of 145 SNe Ia observed0.0 by SN with known clus- cosmological0.4 fits separately for0.4 the SNe Ia inside and outside ters of galaxies and used the cluster redshift to measure the red- in Xavier et al.(2013), who found the following mean values for 0.2 0.2 galaxy0.0 clusters or to perform0 more.0 detailed study of the behav- shifts− of the SNe Ia instead− of the host galaxy redshift. Among SN LC parameters: X1 = 0.14 0.04 (field), 0.40 0.20 (clus- ior of the3 supernova2 1 0 light1 curve parameters0.1 0.0 0 in.1 both0.2 subsamples. the full3 sample2 of1 SNe0 Ia,1 11 were0.1 found0.0 0 to.1 be0.2 in clusters of − − − ± − − ± − − − − ters), and C = X01.011 0.004 (field), andC 0.03 0.02 (clus- X1 C Once1 samples.6 of− SNe Ia± in clusters1.6 become− much± larger, it will galaxies. ters). For comparison our means are X1 = 0.01 0.09 (field), be interesting1.2 to perform such1. analyses2 again,− especially± to find 0.2 0.2 out0.65 whether0.36/ variation0.56 0. of34 the(clusters light without/withcurves parameters SN2006X), and-11 lumi- and The technique we developed improved the redshift measure--11 − 0±.8 − ± 0.8 Cnosity,= 0.01 could0. be01 important(field), 0.02 for cosmology.0.03/0.13 0.11 (clusters with- ments0. for0 low and intermediate0.0 redshifts (z < 0.1) and decreased 0.4 0.4

] ± ± ± out/with1 SN2006X). The correlation between HRs for 11 SNe in the spread0.2 on the Hubble diagram.0.2 When peculiar velocities are | − − − clusters0.0 and the mass of their0 host.0 galaxy is the same as shown wRMS = . takencorr into account for the SNe in clusters the 0 130 15 14 13 12 11 10 9 9 10 11 12 15 14 13 12 11 10 9 9 10 11 12 − − − − − − − − − − − − − − ± in Fig. 15 of Xavier et al.(2013). . HR wRMS = . . 6. Conclusionslog(LsSFR) log(Mstellar) 0 038 mag is smallerlog(LsSFR) than the log(M0 137stellar)0 036 mag found 1.6 1.6 ±

We also performed a morphological classiﬁcation of the when| − | no correction is applied. The correction is statistically log(LsSFR) log(LsSFR) [1000 km s |

Unknownz 1.2 peculiar velocities1 are.2 an additional source of uncer- 0.2 0.2 signiﬁcantHR with a value of 3.58 σ; however, when we exclude

hosts (see Table2) based on the information provided by SIM- | ∆ | BADtaintyc 0 and. on8 theHYPER HubbleLEDA diagram.databases0.8 Usually, (Wenger they et al. are 2000 taken; Makarov into-12 ac- SN2006X0.0 the significance of the0.0 correction decreases to 1.-1234 σ. 1 count0. by4 assuming 150 – 3000.4 km s− as an additional statis- et al. 2014) and images from Childress et al.(2013). The host 0.2 0.2 oftical SNF20080612 uncertainty0.0 in003 the is calculations classified0.0 as or elliptical by applying by HYPER correctionsLEDA We− also found that the Hubble− diagram dispersion of the 11 based onE linearS0 Sab flow−Sb maps.Sbc Sc However,0.4 0.3 the0 velocity.2 0.1 0.0 dispersion for SNe Ia thatE S0 belongSab Sb to clustersSbc Sc is smaller0.4 0.3 than0.2 for0.1 SNe0.0 in the field, and as spiral by Sternberg− et− al.(−2011−). However, the − − − − Morphology RS residuals Morphology . 1 RS residuals classificationgalaxies1.6 inside by galaxySternberg clusters et al.1.6( can2011 be) is much based higher on images than from these but with a p-value of 3 8 10− , which is not statistically sig- methods account for. In this paper we developed a method for nificant. Among 11 SNe found× in clusters, the SNe Ia hosted by Digital1.2 Sky Survey. This host1. looks2 elliptical without any sign 0.2 0.2 assigning SNe Ia to clusters, we studied how the peculiar veloci- blue spiral galaxies,which have high local sSFR, smaller Mstellar, of spiral0.8 arms on the SDSS image.0.8 Therefore, we assigned this ties of SNe Ia in galaxy clusters affect the redshift measurement-13 r/R2000.0 0.7, show higher0 peculiar.0 velocity corrections-13 (see galaxy0.4 to elliptical as in HYPER0.4 LEDA. We found that four SNe and propagate through to the distance estimation. We tested the Fig.90)..2 ' 0.2 belong0.0 to elliptical/lenticular galaxies0.0 while the other seven are − − located in spirals. All of the early-type (elliptical and lenticu- Article0 number,.0 0.4 page0.8 10 of1. 132 14.0 14.5 15.0 0.0 0.4 0.8 1.2 14.0 14.5 15.0 lar) galaxies fallr/R on200 the red sequence forlog(M their200) clusters (see the r/R200 log(M200) color–magnitude diagrams (g r vs. r) for the clusters within the SDSS footprint in Fig. 10).− For the most part the spiral hosts Fig. 11. Absolute change in HRs due to peculiar velocity correction for SNe Ia that belong to clusters as a function of supernova parame- areFig. very 9: Peculiar close to velocitythe red sequence correction, as well,c ∆z , that for is, SNe these Ia galaxies that be- Fig. 11: Absolute change in HRs due to peculiar velocity correc-1 2 ters (X , C; triangles), host properties (local specific SFR (yr− kpc− ), arelong characterized to clusters, as by a redder function colors. of supernova| | parameters (X , C; tion for1 SNe Ia that belong to clusters as a function of supernova 1 stellar mass (M ), morphological type, RS residuals [(g r) (g r)RS ]; 1 2 triangles),In Figs. host9 and properties 11 we also (local show specific how SFR the peculiar (yr− kpc velocity− ), stel- parameterscircles; Childress (X1, C et; al. triangles), 2013; Brown host et properties al. 2014; Rigault (local− et specific al.− 2018− ), SFR rel- ∆ 1 2 correctionlar mass (Mc ),z morphologicaland the absolute type, change RS residuals in HRs [( dueg r to) pecu-(g (yrative− SNkpc position− ), stellar inside mass the cluster (M ), and morphological cluster mass M type,200 (M RS); squares.residu- | | − − − liarr)RS velocity]; circles, correction Childress depend et al. 2013 on the; Brown supernova et al. parameters2014; RigaultX1 alsThe [( colorbarg r) shows(g ther)RS corresponding]; circles, Childress local specific et al.SFR. 2013; Brown andet al.C 2018, host), properties relative SN such position as local inside sSFR, thecluster stellar mass, and cluster mor- et al. 2014− ; Rigault− − et al. 2018), relative SN position inside the phologicalmass M200 type,(M ); the squares. difference The colorbar between shows(g r) of the the correspond- host and cluster and cluster mass M200 (M ); squares. The colorbar shows − correspondinging local specific(g SFR.r) of the red sequence (RS residuals), relative theFig. corresponding9). This is consistent local specific with SFR.the distribution of galaxies in − SN position inside the cluster, and cluster mass M200 (Childress clusters such that the massive, elliptical, and passive galaxies are et al. 2013; Brown et al. 2014; Rigault et al. 2018). The c ∆z located in the center but outer region contains spiral galaxies as plot shows that most of the SNe whose redshifts are significantly| | well and with velocity profiles inside the clusters (see Fig.5; changed have X 0 and are hosted by blue spiral galaxies that ficeCarlberg of High et Energy al. 1997 Physics, their of the Fig. U.S. 1; Department and Rines of Energy & Diaferio under Contract 2006, Since the majority1 ' of galaxies in the Universe are not found havein galaxy high clusters, local sSFR but in and filamentary smaller M structuresstellar, r/R such200 as the0.7 Great(see No.their DE-AC025CH11231. Fig. 15). Support in France was provided by CNRS/IN2P3, ' CNRS/INSU, and PNC; LPNHE acknowledges support from LABEX ILP, sup- Wall (Geller & Huchra 1989), SNe Ia in galaxy clusters are rare ported by French state funds managed by the ANR within the Investissements A162,in untargeted page 10 of searches 12 such as SNfactory. Next decade surveys d’Avenir programme under reference ANR-11-IDEX-0004-02. NC is grateful to such as the Zwicky Transient Facility (ZTF) or the Large Synop- the LABEX Lyon Institute of Origins (ANR-10-LABX-0066) of the University tic Survey Telescope (LSST) (Bellm 2014; LSST Science Col- de Lyon for its financial support within the program "Investissements d’Avenir" (ANR-11-IDEX-0007) of the French government operated by the National Re- laboration et al. 2009) will observe thousands of SNe Ia and search Agency (ANR). Support in Germany was provided by DFG through therefore have much larger samples of SNe Ia in clusters. These TRR33 "The Dark Universe" and by DLR through grants FKZ 50OR1503 and can be used to study dependencies between SNe Ia and host FKZ 50OR1602. In China support was provided by Tsinghua University 985 clusters with greater certainty. LSST will be much deeper than grant and NSFC grant No 11173017. Some results were obtained using re- factory sources and support from the National Energy Research Scientific Computing SN or ZTF, so the method of cluster selection based only Center, supported by the Director, Office of Science, Office of Advanced Scien- on the presence of X-rays will not be viable until much deeper tific Computing Research of the U.S. Department of Energy under Contract No. all-sky X-ray surveys are performed. Even though the impact of DE-AC02- 05CH11231. We thank the Gordon & Betty Moore Foundation for peculiar velocities decreases with distance and becomes negligi- their continuing support. Additional support was provided by NASA under the ble at high redshifts, SN Ia rates in clusters (Sharon et al. 2010; Astrophysics Data Analysis Program grant 15-ADAP15-0256 (PI: Aldering). We also thank the High Performance Research and Education Network (HPWREN), Barbary et al. 2012) and the difference in SN light curve param- supported by National Science Foundation Grant Nos. 0087344 & 0426879. This eters inside and outside the clusters could be fruitful avenues of project has received funding from the European Research Council (ERC) under investigation for future cosmological analyses. the European Union’s Horizon 2020 research and innovation programme (grant agreement No 759194 - USNAC). PFL acknowledges support from the National Acknowledgements. We thank the technical staff of the University of Hawaii 2.2 Science Foundation grant PHY-1404070. MVP acknowledges support from Rus- m telescope and Dan Birchall for observing assistance. We recognize the signif- sian Science Foundation grant 14-12-00146 for the selection of SNe exploded in icant cultural role of Mauna Kea within the indigenous Hawaiian community, galaxy clusters. This research has made use of the NASA/IPAC Extragalactic and we appreciate the opportunity to conduct observations from this revered Database (NED), which is operated by the Jet Propulsion Laboratory, California site. This work was supported in part by the Director, Office of Science, Of- Institute of Technology, under contract with the National Aeronautics and Space

Article number, page 11 of 13 P.-F. Léget et al.: Type Ia supernovae and Galaxy clusters

The small size of our sample does not allow us to per- community, and we appreciate the opportunity to conduct observations from this form cosmological fits separately for the SNe Ia inside and revered site. This work was supported in part by the Director, Office of Science, outside galaxy clusters or to perform more detailed study of Office of High Energy Physics of the U.S. Department of Energy under Contract No. DE-AC025CH11231. Support in France was provided by CNRS/IN2P3, the behavior of the supernova light curve parameters in both CNRS/INSU, and PNC; LPNHE acknowledges support from LABEX ILP, subsamples. Once samples of SNe Ia in clusters become much supported by French state funds managed by the ANR within the Investissements larger, it will be interesting to perform such analyses again, espe- d’Avenir programme under reference ANR-11-IDEX-0004-02. NC is grateful to cially to find out whether variation of the light curves parameters the LABEX Lyon Institute of Origins (ANR-10-LABX-0066) of the University de Lyon for its financial support within the program “Investissements d’Avenir” and luminosity, could be important for cosmology. (ANR-11-IDEX-0007) of the French government operated by the National Research Agency (ANR). Support in Germany was provided by DFG through TRR33 “The Dark Universe” and by DLR through grants FKZ 50OR1503 and 6. Conclusions FKZ 50OR1602. In China support was provided by Tsinghua University 985 grant and NSFC grant No 11173017. Some results were obtained using resources Unknown peculiar velocities are an additional source of uncer- and support from the National Energy Research Scientific Computing Center, tainty on the Hubble diagram. Usually, they are taken into supported by the Director, Office of Science, Office of Advanced Scientific 1 Computing Research of the U.S. Department of Energy under Contract No. account by assuming 150–300 km s− as an additional statis- DE-AC02-05CH11231. We thank the Gordon & Betty Moore Foundation for tical uncertainty in the calculations or by applying corrections their continuing support. Additional support was provided by NASA under the based on linear flow maps. However, the velocity dispersion for Astrophysics Data Analysis Program grant 15-ADAP15-0256 (PI: Aldering). We galaxies inside galaxy clusters can be much higher than these also thank the High Performance Research and Education Network (HPWREN), methods account for. In this paper we developed a method for supported by National Science Foundation Grant Nos. 0087344 & 0426879. This assigning SNe Ia to clusters, we studied how the peculiar veloci- project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant ties of SNe Ia in galaxy clusters affect the redshift measurement agreement No 759194 – USNAC). P.F.L. acknowledges support from the National and propagate through to the distance estimation. We tested the Science Foundation grant PHY-1404070. M.V.P. acknowledges support from match of 145 SNe Ia observed by SNFACTORY with known clus- Russian Science Foundation grant 14-12-00146 for the selection of SNe exploded ters of galaxies and used the cluster redshift to measure the in galaxy clusters. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California redshifts of the SNe Ia instead of the host galaxy redshift. Among Institute of Technology, under contract with the National Aeronautics and Space the full sample of SNe Ia, 11 were found to be in clusters of Administration. Funding for the Sloan Digital Sky Survey IV has been provided galaxies. by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of The technique we developed improved the redshift measure- Science, and the Participating Institutions. SDSS-IV acknowledges support and ments for low and intermediate redshifts (z < 0.1) and decreased resources from the Center for High-Performance Computing at the University of Utah. The SDSS web site is www.sdss.org. SDSS-IV is managed by the Astro- the spread on the Hubble diagram. When peculiar velocities are physical Research Consortium for the Participating Institutions of the SDSS taken into account for the SNe in clusters, the wRMS = 0.130 Collaboration including the Brazilian Participation Group, the Carnegie Institu- 0.038 mag is smaller than the wRMS = 0.137 0.036 mag found± tion for Science, Carnegie Mellon University, the Chilean Participation Group, when no correction is applied. The correction± is statistically the French Participation Group, Harvard-Smithsonian Center for Astrophysics, Instituto de Astrofísica de Canarias, The Johns Hopkins University, Kavli significant with a value of 3.58σ; however, when we exclude Institute for the Physics and Mathematics of the Universe (IPMU)/University of SN2006X the significance of the correction decreases to 1.34σ. Tokyo, Lawrence Berkeley National Laboratory, Leibniz Institut für Astrophysik We also found that the Hubble diagram dispersion of the 11 Potsdam (AIP), Max-Planck-Institut für Astronomie (MPIA Heidelberg), SNe Ia that belong to clusters is smaller than for SNe in the field, Max-Planck-Institut für Astrophysik (MPA Garching), Max-Planck-Institut but with a P-value of 3.8 10 1, which is not statistically sig- für Extraterrestrische Physik (MPE), National Astronomical Observatories of × − China, New Mexico State University, New York University, University of Notre nificant. Among 11 SNe found in clusters, the SNe Ia hosted by Dame, Observatário Nacional/MCTI, The Ohio State University, Pennsylvania blue spiral galaxies,which have high local sSFR, smaller Mstellar, State University, Shanghai Astronomical Observatory, United Kingdom r/R200 0.7, show higher peculiar velocity corrections (see Participation Group, Universidad Nacional Autónoma de México, University Fig.9). ' of Arizona, University of Colorado Boulder, University of Oxford, University of Portsmouth, University of Utah, University of Virginia, University of Wash- Since the majority of galaxies in the Universe are not found ington, University of Wisconsin, Vanderbilt University, and Yale University. in galaxy clusters, but in filamentary structures such as the This research has made use of the SIMBAD database, operated at CDS, Great Wall (Geller & Huchra 1989), SNe Ia in galaxy clus- Strasbourg, France. We acknowledge the usage of the HYPERLEDA database ters are rare in untargeted searches such as SNFACTORY. Next (http://leda.univ-lyon1.fr). 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