arXiv:1401.3228v1 [astro-ph.GA] 14 Jan 2014 ob eyeetv ehdt n aaisu to up galaxies find to method proven effective has of sky very use the a on The be area to wide redshift. a over high filters band at narrow populations galaxy studied Ly strong through n utcneta ihrrdhfs Beyond decreas- redshifts. the higher to at due content expected is dust which ing 2010), al. et (Stark 02 n ta.21) h osblt ffidn LAEs finding of al. possibility et The Schenker 2012; 2012). al. from al. 2011; et et al. Shibuya Ono et 2012; 2012; Vanzella 2010; al. al. et et Fontana Rhoads 2006; al. et (Iye ie thsbe bevdta h A rcinin fraction LAE to the up that redshift with observed increases been galaxies cosmic has selected over UV evolution It galaxy understand time. to used be can og Gonz Jorge eCie .Mcen 80 atao Chile Santiago, 4860, Mackenna V. Chile, de USA 87801, NM corro, USA 20742, MD Park, Germany Bonn, 53121 d’Here H¨ugel 71, dem Martin Saint 38406 Universitaire, France Domaine Piscine, Italy Pisa, Germany Heidelberg, D-69117 17, USA 14853, NY Ithaca, Building, ences 782 4860, [email protected] Vicu˜na Mackenna Chile; Santiago, Macul, Av. 0436 Chile, Cat´olica de versidad ya-lh mtes(A)aeglxe selected galaxies are (LAE) Emitters Lyman-alpha cetdfrpbiaini h srpyia Journal. L Astrophysical using the typeset Preprint in publication for Accepted Neri 9 8 7 6 5 4 3 2 1 ainlRdoAtooyOsraoy .O o ,So- Cat´o 0, Universidad Astro-Ingenier´ıa, Pontificia Box de O. Centro P. Observatory, Astronomy Radio College National Maryland, of University Astronomy, of Department Au Bonn, of University Astronomy, for Institute Argelander la de Rue Millim´etrique, I-56126 300 RadioAstronomie 7, de Cavalieri Institut dei Piazza Superiore, Normale Scuola K¨onigst f¨ur Heidelberg, Institute Astronomie Planck Sci- Max Space 220 University, Cornell Department, Astronomy F´ısica, Pontificia de Astrof´ısica, Facultad de Instituto z 5 ∼ rn Bertoldi Frank , of pe ii nte[C the in limit upper bevtoswt LAadCCAT. Keywords: and ALMA [C with for observations search the for relevant AS67J n ftehgetrdhf aaycniaet dat to candidate galaxy redshift highest the of one , MACS0647-JD CRA n h lta eBr nefrmtr(dI.W obs We in (PdBI). Research Interferometer for Bure Array de Combined Plateau the the using and galaxy (CARMA) J-Dropout one and mosrain.FrIK1 D 121.+708adSFJ132 Mic SDF Cosmic and of the J132415.7+273058 luminosity of FIR SDF effects the dist the IOK-1, energy for account For spectral limits into a taking using observations. galaxies and mm the 6946 of NGC luminosity galaxy FIR the to limits o h [C the for epeettesac o h [C the for search the present We D 121.+708( J132415.7+273058 SDF addt on eidteglx lse AS04.+05 For MACSJ0647.7+7015. cluster galaxy the behind found candidate Asdsoee nteSBR epfil SF n h utpeImage Multiple the and (SDF) field deep SUBARU the in discovered LAEs < to 1 6 alez-L ´ . 1 z × ERHFR[I]EISO IN EMISSION [CII] FOR SEARCH ∼ 10 1. α II aais ihrdhf–glxe:idvda IK1 D J132415.7 SDF (IOK-1, individual galaxies: high-redshift– galaxies: 120.+753 AS67J)–S:lnsadbands and lines –ISM: MACS0647-JD) J132408.3+271543, ielmnst of luminosity line ] opez ´ 10 A hw htti yeo galaxies of type this that shows 7 msinadaeaogtemost the among are and emission INTRODUCTION T × E tl mltajv 04/17/13 v. emulateapj style X ( nraFerrara Andrea 1,3,9 µ/ 6 let .Bolatto D. Alberto , 15) oii .Riechers A. Dominik , II msinof emission ] − 1 L z ⊙ cetdfrpbiaini h srpyia Journal. Astrophysical the in publication for Accepted 6 = (where II msini ihrdhf aaisa ela h iclisfrfuture for difficulties the as well as galaxies redshift high in emission ] . < 4)adSFJ3483214 ( J132408.3+271543 SDF and 541) < 4 < 2 II ioaGallerani Simona , 2 . µ msinln nthree in line emission ] 05, . 1 3 3 33, z . stemgicto atr.W xlr h ieetconditions different the explore We factor). magnification the is 36 ∼ < × 7 tis it 6 . hitpe .Carilli L. Christopher , z z 10 9ad7 and 79 2 4 oet Decarli Roberto , ABSTRACT Uni- ∼ ∼ . lica uhl 8 2and 52 Z × s, 6 7 - f ( 6 = µ/ 15) . . 72 5 xetdta h A rcindcessa h amount (H the Hydrogen as decreases neutral fraction of LAE the that expected o1 ftettlifae uioiyi oegalax- some in luminosity infrared total the of 1% to aino lentv en osuytehgetred- [C highest e.g., lines, the far-infrared emission study include structure explo- candidates fine to the Promising motivates means galaxies. and This shift alternative strength derive. of line to ration Ly-alpha con- difficult reso- the the on are from through constrains shape by properties direct escape and gas Therefore the absorption, its outflows. dust from and by tribution region depth scattering, optical emission high nant its the by complicated in is been Ly-alpha has of that sion line at only the observed wavelengths, 2013). optical/UV al. at et Coe 2012; al. et (Zheng JD t157 at of detection of consistent rate is success This 2011; low 2012). Ly al. al. comparatively et et the Pentericci Schenker (IGM) 2010; with 2012; al. al. Medium et et Stark Intergalactic Ono 2008; al. the et of (Ota reionization plete 03,adtecniae on eidglx clus- galaxy behind found al. et candidates Capak al. at 2013; the et ters al. (Bouwens et and (UDF) Brammer 2013; Tele-2013), al. Field et Space Deep Ellis 2011; Hubble Ultra (HST) the scope in discovered UDFj-39546284 nl eta G at IGM neutral ingly obdb H by sorbed thg esit uha h candidate the as candidates such the redshift, confirm high spectroscopically at to difficult be < − − mn h sa neselrmdu IM tracers (ISM) medium Interstellar usual the Among fLmnapapoosfo redshifts from photons Lyman-alpha If 4 × α n eploInfante Leopoldo and , 1 10 1SA-OMN GALAXIES. STAR-FORMING 11 L 10 msinat emission . ⊙ 56 . 11 74 z > z n nuprlmti h I luminosity FIR the in limit upper an and L × ∼ 3 ⊙ ainWalter Fabian , µ 10 9 I ,wihi o ffce yteincreas- the by affected not is which m, epciey o h esdgalaxy lensed the For respectively. > z 6 . nteIM(aa err 02,i will it 2012), Ferrara & (Dayal IGM the in 8 AS19J and MACS1149-JD 6 . ya-lh mtes(LAEs) emitters Lyman-alpha 5 8 L z with e ireCox Pierre , ⊙ re he bright three erved z 6 = h AsIK1( IOK-1 LAEs the nglxe sL-lh.Teemis- The Ly-alpha. is galaxies in 4 iuintmlt ftelocal the of template ribution & 0.+753w n upper find we 408.3+271543 epciey efidupper find We respectively. ilmtrwv Astronomy Millimeter-wave oaeBcgon nthe on Background rowave 7. . 5)w n pe limits upper find we 554) z > z ph lensed d I nrae,det h incom- the to due increases, ) 10 = 1,9 3 ii Vallini Livia , n a con o up for account can and 7 5 lsbt aCunha da Elisabete , . 7 235,SDF +273058, − +0 z 0 . . ∼ z 6 4 z ∼ II eptan put we ∼ 1galaxy 11 ( ] 6 = 10 2 6 z P . . MACS0647- 7 . z 5 965), 3 ∼ 4 / − ≥ Roberto , 2 2galaxy 12 → 7 r ab- are 7 2 P 3 1 , / 2 ) 2 Gonzalez-L´ opez´ et. al. ies, especially in those with low luminosity and metallic- is presented in Sect. 5. Throughout this paper we use −1 ity (Crawford et al. 1985; Stacey et al. 1991; Israel et al. a Λ-Cold Dark Matter cosmology with H0 = 70 km s −1 1996; Madden et al. 1997). Mpc , ΩΛ =0.7 and Ωm =0.3. The [C II] line traces photo-dissociation (a.k.a. photon- 2. OBSERVATIONS dominated) regions (PDRs), as well as diffuse H I and H II regions. In PDRs, the far-UV radiation produced 2.1. Source Selection by OB stars heats the surface layers of molecular clouds, The three Lyman-α emitters targeted in this study which cool preferentially through [C II] emission. It has were discovered in the Subaru Deep Field (SDF). Two been observed that most of the [C II] emission in IR- of the LAEs observed belong to the sample of LAEs at bright galaxies is coming from PDRs, and that the PDR z ∼ 6.6 discovered by Taniguchi et al. (2005). The tar- gas mass fraction can be up to 50% in starbursts like gets are the brightest LAEs (sources 3 and 4 in their cat- M82 (Crawford et al. 1985). alog) and have a narrow and bright Lyman-α emission Modeling of FIR emission lines observed in starburst line. The third LAE (IOK-1) was discovered at z ∼ 7 galaxies showed that at least 70% of the [C II] emission is by Iye et al. (2006). It is one of the brightest and most produced in PDRs (Carral et al. 1994; Lord et al. 1996; distant LAEs known to date. Colbert et al. 1999). In the low-metallicity system Haro The fourth target, MACS0647-JD, is a lensed Lyman- 11, on the other hand, at least 50% of the [C II] emission break galaxy (LBG) discovered behind the galaxy cluster arises from a more diffuse, extended ionized medium MACSJ0647.7+7015 at z =0.591 (Coe et al. 2013). The (Cormier et al. 2012). The different conditions in which galaxy was discovered as a J-Dropout galaxy lensed into the [C II] emission is produced, and the direct or indi- 3 magnified images as part of The Cluster Lensing And rect relation of these conditions with the star forma- Supernova survey with Hubble (CLASH) (Postman et al. tion process, suggest that [C II] emission should be a 2012). The three images of the galaxy MACS0647-JD1, good tracer of the global galactic star formation activity MACS0647-JD2 and MACS0647-JD3, have a magnifica- (de Looze et al. 2011), at least for galaxies with low Tdust tion of ∼8,∼7 and ∼2 respectively. The photometric 2 or low ΣIR = LIR/πrmid−IR (Diaz-Santos et al. 2013). +0.6 redshift of the galaxy is 10.7−0.4 (95% confidence lim- [C II] is found to be the strongest emission line, stronger its). This is one of the highest redshift galaxy candidates than CO, and thus is the most promising tracer of the known to date. dense, star forming regions in distant galaxies where [C II]can be detected with ground-based telescopes due 2.2. CARMA Observations to the redshift into observable atmospheric windows. Observations of the three z ∼ 6.5 − 7 LAEs were In the past years, the [C II]158 µm emission carried out using the Combined Array for Research line has been established as a promising observ- in Millimeter-wave Astronomy (CARMA) between 2008 able in high-redshift galaxies (Maiolino et al. 2005; July and 2010 July. The array configurations used were Iono et al. 2006; Maiolino et al. 2009; Walter et al. the most compact, D and E, to minimize phase decoher- 2009; Hailey-Dunsheath et al. 2010; Stacey et al. ence and maximize point source sensitivity. The [C II] line 2010; Ivison et al. 2010; Wagg et al. 2010; Cox et al. has a rest frequency of 1900.54 GHz (157.74 µm). For 2011; De Breuck et al. 2011; Valtchanov et al. 2011; the redshifts of the targets, the line is shifted to the 1 Gallerani et al. 2012; Venemans et al. 2012; Wagg et al. mm band. The receivers were tuned to a frequency ∼150 2012; Walter et al. 2012a; Carilli et al. 2013; Wang et al. kms−1 bluer than the expected frequency from the red- 2013; Willott et al. 2013; Riechers et al. 2013). Most shift determined by the peak of the Lyman-α line. This of the high-z detections were for infrared-luminous is for taking into account the possible absorption by the starbursts, many of which also show signatures of AGN. IGM in the Lyman-α line. The setups provide an instan- See the review by Carilli & Walter (2013) for more taneous bandwidth of ∼ 1.5 GHz (∼ 1800kms−1) with details. − −1 ∼ − 1 With star formation rates of a few tens M⊙yr , based a spectral resolution of 31.25 MHz ( 37 39 kms ). on the Lyα and UV continuum emission, LAEs are classi- The observations were processed using MIRIAD fied as “normal” star forming galaxies. Different studies (Sault et al. 1995). The absolute flux calibrators used claim that LAEs are young, dust free, starbursting galax- are 3C84, MWC349, 3C273 and Mars, the latter being ies, supported by UV observations (Gawiser et al. 2006; the most used. As passband calibrators the QSOs 3C273, Finkelstein et al. 2007; Lai et al. 2008). Recent MIR de- 3C345 and 0854+201 were used. As gain calibrator the tection of LAEs at z ∼ 2.5 and z < 0.3 show that a sig- QSO 1310+323 was used. The time on source for IOK- nificant fraction of the star formation in these galaxies is 1 was 58.5 hours, for SDF J132415.7+273058 was 15.9 strongly obscured by dust (Oteo et al. 2012a,b). Thus, hours and for SDF J132408.3+271543 4.6 hours. The fi- LAEs are promising targets for the detection of [C II] at nal cubes were made using natural weighting to maximize high redshift. point source sensitivity. The observations resulted in the following beamsizes: IOK-1: 1.86” × 1.33”, PA= −0.34◦, Previous attempts to detect [C II] in a small sample of ◦ ∼ SDF J132415.7+273058: 1.92”×1.56”, PA= 83.45 , SDF LAEs at z 6.6 were unsuccessful (Walter et al. 2012b; ◦ Kanekar et al. 2013; Ouchi et al. 2013). J132408.3+271543: 2.54” × 2.01”, PA= 88.02 (all tar- Here we present the result of a search for [C II] in three gets: D and E configurations). For D configuration the LAEs at z > 6.5 and in a lensed galaxy at z ∼ 11. In minimum baseline is 11 meters and the maximum is 150 Sect. 2 we describe the target selection and observations. meters. For E configuration the minimum baseline is 8 The data is shown in Sect. 3 together with some impli- meters and the maximum is 66 meters. Table 1 summa- cations and analysis in Sect. 4. A summary of the paper rizes the sensitivities reached for the observations of the LAEs. Search for [CII] emission in z =6.5 − 11 star-forming galaxies. 3
2.3. Velocity offset [km s-1 ] PdBI Observations 500 400 300 200 100 0 -100 -200 -300 -400 -500 All MACS0647-JD observations were carried out in 4.0 IOK-1 2012 November as part of a DDT (Director’s Discre- tionary Time) program with the Plateau de Bure Inter- ferometer (PdBI). The target was observed with 4 WideX 2.0 frequency setups (3.6 GHz bandwidth each), covering 80% of the photometric redshift range (z = 10.1 − 11.1). 0.0 Two of the three lensed images (JD1 and JD2) are within 18” of each other and they were covered in a -2.0 common 2 mm pointing. The absolute flux calibrators used are MWC349, 2200+420, 3C279 and 0716+714. density[mJy/Beam] Flux As gain calibrator the QSO 0716+714 was used. The -4.0 total on source time for all tunings was 7.4 hours (6- 238.5 238.6 238.7 238.8 238.9 239.0 239.1 239.2 239.3 antennas equivalent). The observations were processed Frequency [GHz] -1 using GILDAS. The beamsize of the observations is the Velocity offset [km s ] ◦ 500 400 300 200 100 0 -100 -200 -300 -400 -500 following: MACS0647-JD : 2.10”×1.76”, PA= 102.0 (C 10.0 configuration). For C configuration the minimum base- SDF J132415.7+273058 line is 22 meters and the maximum is 184 meters. Table 2 summarizes the sensitivity reached for the observations 5.0 of MACS0647-JD .
3. RESULTS 0.0
-5.0 3.1. Line Emission density[mJy/Beam] Flux
-10.0 The spectra of the three z ∼ 6.5 − 7 LAEs are pre- 251.8 251.9 252.0 252.1 252.2 252.3 252.4 252.5 252.6 sented in Fig. 1 and the spectrum of MACS0647- Frequency [GHz] JD is shown in Fig.2. No significant emission is de- Velocity offset [km s-1 ] tected at the redshifted line frequencies or close to them. 500 400 300 200 100 0 -100 -200 -300 -400 -500 25.0 The observations were sampled to a channel resolution SDF J132408.3+271543 of 50 kms−1 similar to the expected FWHM of the 20.0 [C II] emission line (see Sect. 4.1). We use our non- 15.0 detections to put constrains on the luminosities of the 10.0 [C II]lines for all targets. The results for the LAEs can be seen in the Table 1 and for the MACS0647-JD in Ta- 5.0 ble 2. The upper limits were estimated assuming that the 0.0 sources were unresolved. For MACS0647-JD the spectra of the two images were corrected by the primary beam -5.0 Flux density[mJy/Beam] Flux pattern before combination. The [C II] luminosities were -10.0 estimated assuming that the velocity integrated flux of -15.0 251.2 251.3 251.4 251.5 251.6 251.7 251.8 251.9 252.0 the line is Iline=Sline ∆v, with Sline being 3 times the Frequency [GHz] r.m.s. of the 50 km s−1 channel and ∆v = 50kms−1 Figure 1. Spectra of the LAEs with a velocity resolution of 50 the range in velocity (details on Tab. 1 notes). Using km s−1 . The relative velocities are with respect to the frequency −1 3σ over a 50 kms channel to estimate the upper limit expected for the [C II] line including absorption by the IGM (150 −1 in the luminosities can result in a underestimation. We km s to the blue of zLyα). The redshifts of the target are z=6.965 point out that for a more conservative estimation the lu- for IOK-1, z=6.541 for SDF J132415.7+273058 and z=6.554 for minosities should be multiplied by a factor 2. (i.e. 3σ SDF J132408.3+271543 . −1 over 200 kms channel). Assuming a channel width of 4. DISCUSSION −1 ∼ 200 kms , our IOK-1 [C II] limit is 10% deeper than 4.1. Width of the [CII] emission line. the previous PdBI limit (Walter et al. 2012b). Previous studies have presented the non-detection 3.2. Continuum Emission of [C II] (Walter et al. 2012b; Ouchi et al. 2013) with a −1 No continuum emission is detected in our observations channel resolution of 200 kms , a choice motivated by of the three LAEs and the z ∼ 11 LBG. The sensitivity the width of the Lyα emission line. We argue that re- reached for the continuum observations is given in the cent observations and models of [C II]in LAEs suggest Tab. 1 for the LAEs and a continuum map for the three that the [C II] line could be narrower that the previously LAEs is shown in Fig. 3. The results for the MACS0647- assumed value. JD are given in Tab. 2 and the continuum map is shown 4.1.1. II in Fig. 4. In Sect. 4.2 we discuss how the CMB affects [C ] detection on a LAE z=4.7. our continuum observations and in Sect. 4.3 we use our In support of a the narrow emission line is the de- continuum measurements to constrain the nature of our tection of [C II] in a LAE at z = 4.7 (Lyα -1) with targets. ALMA (Carilli et al. 2013). The FWHM of the emis- 4 Gonzalez-L´ opez´ et. al.
Table 1 Summary of Observations and Results for the LAEs
a b c d e N6946 f g h source RA DEC z νobs σcont σline L[CII] LIR,CMB SFRdust,CMB SFRUV −1 −1 8 11 −1 −1 J2000.0 J2000.0 GHz mJy b mJy b 10 L⊙ 10 L⊙ M⊙ yr M⊙ yr IOK–1 13:23:59.80 +27:24:56.0 6.965 238.881 0.19 1.17 <2.05 <6.34 <109.1 ∼24 SDF J132415.7 13:24:15.70 +27:30:58.0 6.541 252.154 0.37 2.82 <4.52 <10.3 <177.2 ∼34 SDF J132408.3 13:24:08.30 +27:15:43.0 6.554 251.594 0.75 5.67 <10.56 <21.0 <360.9 ∼15
Note. — All luminosities upper limits are 3 σ. a References: IOK–1:Iye et al. (2006); Ono et al. (2012) –SDF J132415.7+273058 and SDF J132408.3+271543 : Taniguchi et al. (2005) b Observing Frequencies; tuned ∼125MHz blueward of the Ly–α redshifts for all targets. c 1σ continuum sensitivity at 158µm rest wavelength. d 1σ [CII] line sensitivity over a channel width of 50 kms−1. e −1 −3 −1 2 3σ [CII] luminosity limit over a channel width of 50 kms assuming Lline = 1.04 × 10 Iline νrest(1 + z) DL, where the line luminosity, Lline, −1 is measured in L⊙; the velocity integrated flux, Iline=Sline ∆v, in Jy kms ; the rest frequency, νrest = νobs(1 + z), in GHz; and the luminosity distance, DL, in Mpc. (e.g. Solomon et al. (1992) f 3σ limit based on the SED of NGC 6946 and including the effect of the CMB. g N6946 3σ limit based on LIR including the effect of the CMB. h UV–based SFR from Jiang et al. (2013a)
[CII] Redshift 11.0 10.8 10.6 10.4 10.2 8
6
4
2
0
-2
Flux density [mJy] density Flux -4
-6
-8 158 160 162 164 166 168 170 Observed frequency [GHz]
Figure 2. Spectrum of MACS0647-JD . The spectrum shows the added fluxes measured on the positions of the two lensed images JD1 and JD2 (combined magnification µ ∼ 15). The spectra of the two images were corrected by the primary beam pattern before combination. The 4 setups are plotted in different colors, blue, red, green and orange the colors for the setups A, B, C and D respectively. The error bars correspond to the quadrature of the errors of the individual measurement of the fluxes for JD1 and JD2 in each frequency channel. For display purposes, the spectrum is sampled at a channel resolution of 200 km s−1 , but the search of the [C II] line as well as the analysis was made with the spectrum sampled to 50 km s−1 . sion line is 56 km s−1 , which is one order of magni- conclude that the quasar is unlikely the source of heat- tude narrower than the width of the Lyα emission line ing and ionization in the LAE. of ∼ 1100 kms−1 of the same source (Petitjean et al. Based on deep, spatially resolved optical spectroscopy 1996; Ohyama et al. 2004). Despite of the LAE being of the LAE, Ohyama et al. (2004) argue that the LAE at a separation of 2.3′′ (∼ 15 kpc) to the quasar BRI is likely the composition of a normal star-forming galaxy 1202-0725, there is no evidence for a significant influ- and an extended nebula with violent kinematic status. ence of the quasar on the properties of the LAE from This nebula emission would produce a broadening of the the observations. Carilli et al. (2013) tried to model the Lyα emission. This nebula can be explained, at least in a emission of the LAE taking into account the radiation qualitative way, as a superwind caused by the supernovae coming from the luminous nearby quasar. All the mod- explosion of OB stars in the late phase of the evolution els that reproduce the [C II]and Lyα luminosities predict of a starburst. higher luminosities for other UV lines that are not de- In conclusion, this LAE is not intrinsically different tected (Ohyama et al. 2004). Given this results, they from the general population of LAE. The [C II] detection Search for [CII] emission in z =6.5 − 11 star-forming galaxies. 5
8.0
6.0 SDF J132415.7+273058 SDF J132408.3+271543 IOK-1
4.0
2.0
-0
-2.0
DEC (arcsec) DEC -4.0 ∆ -6.0
-8.0
-8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0 8.0 -8.0 -6.0 -4.0 -2.0 -0 2.0 4.0 6.0 8.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0 8.0 ∆RA (arcsec) ∆RA (arcsec) ∆RA (arcsec)
Figure 3. Rest-frame 158 µm continuum maps of the LAEs. Each contour level represents 1σ steps (±1σ levels are not shown). Solid contours are positive signal and dashed contour are negative signals. The 1σ levels are 0.75 mJy beam−1 for SDF J132408.3+271543 , 0.37 mJy beam−1 for SDF J132415.7+273058 and 0.19 mJy beam−1 for IOK-1. The blue crosses represent the position of each LAE as given in Tab. 1. 15.0 Table 2 Summary of Observations and Results for MACS0647JD 10.0 JD1 Parameter MACS0647-JD1, JD2 Coordinates (J2000) JD1 06:47:55.731,+70:14:35.76 Coordinates (J2000) JD2 06:47:53.112,+70:14:22.94 5.0 µ (JD1+JD2) ∼ 15 +0.6 Redshift 10.7−0.4 −1 UV SFR ∼ 1 [M⊙yr ] ν 156.7-171.1 [GHz] 0.0 a −1 σcont 0.17 mJy b b −1 JD2 σline (Setup A) 3.31 mJy b b −1 σline (Setup B) 4.12 mJy b (arcsec) DEC -5.0
b −1 Δ σline (Setup C) 3.19 mJy b b −1 σline (Setup D) 6.42 mJy b c × 7 × −1 L[CII] (Setup C) < 6.78 10 (µ/15) [L⊙] c × 8 × −1 L[CII] (Setup D) < 1.36 10 (µ/15) [L⊙] -10.0 N6946,d × 11 × −1 LIR (Corrected CMB) < 1.65 10 (µ/15) [L⊙] e −1 −1 SFR (LIR) (Corrected CMB) < 28 × (µ/15) [M⊙yr ] f × −1 −1 SFR (L[CII]) (Setup C) < 5 (µ/15) [M⊙yr ] -15.0 f −1 −1 -15.0 -10.0 -5.0 0.0 5.0 10.0 15.0 SFR (L ) (Setup D) < 9 × (µ/15) [M⊙yr ] [CII] ΔRA (arcsec) Note. — All luminosities upper limits are 3 σ. References: Coordinates, magnification, redshift and UV-SFR from Figure 4. Continuum map of the field of MACS0647-JD . Each Coe et al. 2013. contour level represents 1σ steps (±1σ levels are not shown). Solid All the luminosities and SFR are corrected by magnification. a contours are positive signal and dashed contour are negative sig- 1σ continuum sensitivity at 158µm rest wavelength. nals. The 1σ level is 93 µmJy beam−1. The blue plus signs rep- b 1σ [CII] line sensitivity over a channel width of 50kms−1. c −1 resent the positions of the two lensed images MACS0647-JD1 and 3σ [CII] luminosity limit over a channel width of 50kms as in MACS0647-JD2 as given in Tab. 2. Tab. 1. The two results correspond to the most sensitive and the least sensitive setups. clumps of individual size ≤ 3 kpc. They present a spec- d 3σ limit based on the SED of NGC 6946 and including the effect of the CMB. trum for the simulated [C II] emission, where the FWHM e N6946 −1 3σ limit based on LIR including the effect of the CMB. of the main peak is ∼ 50 kms , very similar to the f −1 Based on the De Looze et al., 2011 L[CII] − SFR relation. The two 56 kms of the LAE at z=4.7. This suggests that the results correspond to the most sensitive and the lest sensitive setups. width of the [C II] line is to first order determined by the in this LAE can thus be used as a reference for gravitational potential of the clumps. The [C II] emission [C II] searches in other LAEs at high redshift. produced in the CNM follows the gravitational potential of the clumps, resulting in narrow emission lines associ- 4.1.2. Himiko simulations. ated with each clumps. An ensemble of emitting clumps Simulations also suggest narrow [C II] emission lines at moving through the galaxy following the potential of the high redshift for LAEs. Vallini et al. (2013) combine a galaxy could combine and produce a broader line. Such high resolution cosmological simulation with a sub-grid behavior is not observed in the simulations, where just a multi-phase model of the interstellar medium to simulate small number of clumps dominate the [C II] emission. −1 the [C II] emission in a halo similar to the LAE Himiko at We conclude that the adopted width of ∼ 50 kms for z =6.6. They find that 95% of the [C II] emission is gen- the [C II] line in LAEs agrees with recent observations and erated in the Cold Neutral Medium (CNM), mainly in simulations. Nevertheless, we do not discard the possi- 6 Gonzalez-L´ opez´ et. al.
νobs [GHz] observations of high-redshift galaxies. Here we will follow 5 4 3 10 10 1000 100 the prescription formulated by da Cunha et al. (2013) to 10 take into account the effects of the CMB in the contin- Arp220 IOK-1 102 M82 uum observations of galaxies at high redshift in the mm M51 z = 7.0 and sub-mm. We will apply this prescription to the SED 101 NGC6946 of the local galaxies, as if they would be observed at a given redshift z. 100 The templates that we use are those presented by
-1 Silva et al. (1998) for the galaxies Arp 220, M82, M51 10 and NGC 6946. For the galaxies assume cold dust [mJy] z=0 ν -2 with temperature T and an emissivity index β. For
F 10 dust z=0 Arp 220 we used Tdust = 66.7 K and β = 1.86 10-3 z=0 (Rangwala et al. 2011), for M82 Tdust = 48 K and β =1 z=0 -4 (Colbert et al. 1999), for M51 T = 24.9 K and β =2 10 dust (Mentuch Cooper et al. 2012) and for NGC 6946 we used -5 z=0 10 Tdust = 26 K and β = 1.5 (Skibba et al. 2011). At a 0.001 0.01 0.1 1 10 given redshift the CMB contributes to the dust heating λobs [mm] such that the equilibrium temperature is: ν [GHz] obs 1 5 4 4+β 3 10 10 1000 100 z=0 4+β z=0 4+β 4+β 10 Tdust(z)= (Tdust ) +(TCMB) (1+z) −1 . Arp220 MACS0647-JD 102 M82 (1) z ∼11.0 z=0 M51 Tdust is a measurement of the mean dust temperature as 101 NGC6946 determined by a modified blackbody fit to an observed galaxy IR SED at z = 0, representing the total IR lu- 100 minosity of the galaxy. As a representative fit, this is
-1 equally applicable to both optically thin galaxies and op- 10 tically thick as in Arp 220. So long as the galaxy is trans- [mJy]
ν -2 parent to the CMB radiation (true for even Arp 220), Eq.
F 10 1 holds. The additional heating by the CMB affects the 10-3 SEDs such that the peak of the emission is shifted to a shorter wavelength and the total luminosity associated 10-4 z=0 (4+β) to the cold dust is higher by [Tdust(z)/Tdust ] . We need to modify the intrinsic SED of the galaxies to in- 10-5 0.001 0.01 0.1 1 10 clude this new Tdust(z). The flux density depends on the black body radiation for the given temperature, λobs [mm]
Figure 5. Top: Spectral energy distribution of IOK-1. The pho- Fν/(1+z) ∝ Bν (Tdust(z)), (2) tometric points correspond to those measured by Iye et al. (2006); Ota et al. (2010); Cai et al. (2011); Ono et al. (2012). The red tri- To include Tdust(z) we have to apply the following fac- angle corresponds to the 3σ upper limit given by the CARMA tor to convert the intrinsic SED flux density to the emis- observations. The colored lines correspond to the SEDs of local ∗ galaxies shifted to the redshift of IOK-1 and scaled to the ob- sion associated with the new temperature Fν/(1+z). servations in the UV band. The dashed lines correspond to the B (T (z)) observed SED of the local galaxies after the effects of the CMB on ∗ int × ν dust the observations are taken into account. Bottom: Spectral energy Fν/(1+z) = Fν/(1+z) z=0 . (3) distribution of MACS0647-JD. The photometric points correspond Bν (Tdust ) to those presented by Coe et al. (2013). The SED of the galaxies follow the same prescription as in the upper panel. The red triangle This factor will only apply to the part of the SED corresponds to the 3σ upper limit calculated as the quadrature of that correspond to the emission of the cold dust. To the errors of the individual fluxes of JD1 and JD2, in the same way accomplish this, we scale a modified black body (MBB) as the errors presented by Coe et al. (2013). The 1σ photometric to the peak of the FIR emission of the SED at T z=0, uncertainty of the observations is 0.093 mJy, and the error of the dust added fluxes is 0.13 mJy. and then use this MBB emission to estimate the ratio (Rν ) of emission associated with the cold dust at a given bility of [C II] lines being broader than our assumption, frequency, but that the occurrence of unusually narrow lines in this population appears plausible. KνβB (T z=0) R = ν dust , (4) ν F int 4.2. CMB effects. ν where K is just the scaling factor. The flux density as- The Cosmic Microwave Background Radiation (CMB) z=0 sociated to the new temperature of the cold dust will emits as a black body with a temperature of TCMB= be: 2.7 K. The temperature of the CMB increases linearly with (1 + z), becoming an important factor to take ∗ int F = Mν × F (5) into account for observations of objects at high redshift. ν/(1+z) ν/(1+z) da Cunha et al. (2013) showed the effect of the CMB on with Search for [CII] emission in z =6.5 − 11 star-forming galaxies. 7
1999). We conclude that the CMB effects on the [C II] line Bν (Tdust(z)) observations are negligible for our observations. M = (1 − R )+ R × . (6) ν ν ν B (T z=0) ν dust 4.3. Spectral energy distribution of the galaxies. Finally, following da Cunha et al. (2013), we have to Using the upper limits on the continuum, we compare take into account the effect of the CMB as an observ- the targets with the spectral energy distribution tem- ing background. For this we have to multiply the flux plates of local galaxies (SEDs). For the LAEs, the SEDs associated with Tdust(z) by Cν , of the local galaxies are scaled to the flux of a near-IR filter that is not contaminated by the Lyα emission line. Bν (TCMB(z)) Cν = 1 − , (7) For MACS0647-JD , the filter used for the scaling is the Bν (Tdust(z)) one next to the Lyman Break. The photometry of IOK-1 resulting in the flux observed of the galaxies as: and MACS0647-JD together with the SED of local galax- ies are shown in Fig. 5. For SDF J132415.7+273058 and SDF J132408.3+271543 (not shown) the situation is very F obs = C × M × F int , (8) ν/(1+z) ν ν ν/(1+z) similar: the sources have a similar redshift, the contin- uum upper limits are comparable and the CMB effects with Cν ×Mν representing the effect of the CMB in the observations at a given frequency. The same corrections are of the same order. Our upper limit for IOK-1 is com- are derived when an optically thick emission is assumed, parable to the upper limit found by Walter et al. (2012b) as in the case of Arp 220. using PdBI observations. As we can see in Fig. 5, the effect of the CMB decreases Using the SED of NGC 6946 as a template, we estimate the observable flux density at 2 mm by up to a factor of the IR luminosity given the upper limit flux densities, 5× (in the case of M51) for the galaxy at z ∼ 11, when similar to the approach shown by Walter et al. (2012b). the temperature of the CMB is higher, as expected. Also, We scale the SED of NGC 6946 to the 3 sigma upper the effect is higher for galaxies with a lower temperature limits of the mm observations and integrate from 8 µm of the cold dust. Galaxies with temperature of order of to 1 mm (rest frame) to compute the IR luminosity. 25-30 K are more affected than those with temperature The IR luminosity corresponding to this intrinsic SED of 40-50 K. The CMB effects will be important for esti- and the SFR associated (Kennicutt 1998) are given in mations of the flux densities of these type of galaxies in Tab. 1 for the LAEs and in Table 2 for MACS0647-JD . the continuum and for the correct interpretation of the We note that estimating the IR luminosity using NGC observations. 6946 without taking into account the CMB result in a The CMB effects on the [C II] line observations are sim- significant underestimation of the luminosity upper lim- ilar to those on the continuum. The flux of an emission its. The IR luminosity limit corrected by the CMB of line observed against the CMB is: the LAEs at z ∼ 6.6 is 35% higher than without correct- ing by the CMB. For IOK-1 at z ∼ 7, the IR luminosity Sobs B (T (z)) limit is a 50% higher than the estimation without cor- ν/(1+z) − ν CMB ∼ int = 1 , (9) recting by the CMB. For MACS0647-JD at z 10.7, the Sν/(1+z) Bν (Texc) IR luminosity limit corrected for the CMB is ∼ 3.5 times the IR luminosity limit not corrected by the CMB. For with Texc being the excitation temperature of the tran- galaxies with cold dust temperature of ∼ 25 K, the ef- sition. For the case of local thermal equilibrium (LTE), fect of the CMB on the observations is very important at when collisions dominate the excitation of the [C II] line, high redshift, and it will significantly limit the feasibility the excitation temperature of the transition is equal of detecting not extremely starbursting galaxies in the to the kinetic temperature of the gas (Tkin). The ki- IR continuum, it will not greatly affect the detectability netic temperature varies for the different [C II] emission of [C II] emission. regions. Gas temperatures within PDRs are typically ∼ − T 100 500 K (Stacey et al. 2010), for the CNM 4.4. Ratio L[CII]/LFIR T ≈ 250 K, for the WNM T ≈ 5000 K and for the ion- ized medium T ≈ 8000 K(Vallini et al. 2013). Since the Figure 6 presents our upper limits to L[CII]/LFIR and CMB temperature at z =6.5−11 is much lower than the LFIR together with detections of [C II] in other galax- gas temperature of the [C II] emitting region, it will not ies. The arrows represent the region of possible val- contribute significantly to the [C II] excitation, but must ues for L[CII]/LFIR and LFIR (integrated from 42.5µm be taken into account as the background against which to 122.5µm rest frame). If we used UV-based SFR the line flux is measured. In most of the [C II] emission estimates to infer LFIR, our data points would move regions, the temperatures are so high that the observed across the diagonal arrows towards the region where lo- flux of the line against the CMB is similar to the intrin- cal galaxies are, putting our L[CII]/LFIR upper limits obs int ≈ sic flux (Sν/(1+z)/Sν/(1+z) 1). For the extreme case close to the average value found for the local galax- where all the [C II] emission is being produced in PDRs ies. The ratio L[CII]/LFIR is a measure of how effi- with temperature of 100 K in a galaxy at z = 11, the cient the [C II] emission is in cooling the gas. The values observed flux (using Eq. 9) would be 90% of the intrin- presented for our targets, log(L[CII]/LFIR) ∼ −2.9, do sic flux. We found this case very unlikely, since in low not necessarily imply that [C II] is not efficient in cool- redshift galaxies the [C II] emission produced in PDRs is ing the gas in these galaxies, it is most likely a conse- 50-70% of the total [C II] luminosity and the gas tempera- quence of the galaxies having much lower FIR luminosi- tures associated to the PDRs are higher (Crawford et al. ties than our conservative upper limits. Different pro- 1985; Carral et al. 1994; Lord et al. 1996; Colbert et al. cesses can affect the ratio L[CII]/LFIR. In galaxies with 8 Gonzalez-L´ opez´ et. al. low extinction and low metallicity, like in Haro 11, about -1.5 Local Galaxies SDF J132415.7+273058 50% of the [C II] emission arises from the diffuse ionized z > 2 ULIRGs/QSOs SDF J132408.3+271543 medium (Cormier et al. 2012). Variations on the fraction 1 < z < 2 Galaxies MACS0647-JD of [C II] emission associated with the ionized medium will z < 0.1 LIRGs Himiko also affect the ratio L[CII]/LFIR. In some galaxies, the -2.0 IOK-1 HFLS3 internal dust extinction can affect the ratio L[CII]/LFIR. In Arp 220, the dust is optically thick at 158 µm and can absorb part of the [C II] emission, decreasing the ra- ) -2.5 tio L[CII]/LFIR (Rangwala et al. 2011). FIR
Diaz-Santos et al. (2013) present the results of a sur- /L vey of [C II] in luminous infrared galaxies (LIRGs) ob- served with the PACS instrument on board the Her- [CII] schel Space Observatory. They found a tight corre- (L -3.0 lation between the ratio L[CII]/LFIR and the far-IR log Sν (63µm)/Sν(158µm) continuum color, independently of their LIR. They found that the ratio decreases as the average temperature of dust increases, suggest- -3.5 ing that the main observable linked to the variation of L[CII]/LFIR is the average dust temperature. For the galaxies with dust temperatures ∼ 20K the average ratio ∼ −2 -4.0 is log(L[CII]/LFIR) 10 , suggesting that for galaxies 8 9 10 11 12 13 14 15 like NGC 6946 with a dust temperature of ≈ 26 K, the log(L )[L ] ratio L[CII]/LFIR should be on the same order of mag- FIR ⊙ nitude. Diaz-Santos et al. (2013) also found a correla- Figure 6. Ratio of the [C II] luminosity to the FIR luminosity tion between L[CII]/LFIR and luminosity surface density vs the FIR luminosity (integrated from 42.5µm to 122.5µm rest of the mid-IR emitting region (Σ = L /πr2 ). frame) for galaxies at different redshifts. The green symbols cor- IR IR mid−IR respond to the upper limits of the LAEs presented here. The blue LIRGs with lower L[CII]/LFIR ratios are warmer and hexagon corresponds to the upper limit of MACS0647-JD using more compact. We can use this relation to find a rough the most sensitive setup. The FIR luminosities for the galaxies are estimation for L /L of our targets. As r − upper limits estimated from the observations including the CMB [CII] FIR mid IR effects. The black diamond corresponds to the upper limit for we use the size found in the UV observations of the Himiko with ALMA observations (Ouchi et al. 2013). The hori- ≈ targets. The half-light radius of IOK-1 is 0.62 kpc zontal dashed line is the average value for L[CII]/LFIR on the local (Cai et al. 2011). The full width at half maximum size of galaxies. (Malhotra et al. 2001; Negishi et al. 2001; Luhman et al. SDF J132415.7+273058 and SDF J132408.3+271543 are 2003; Iono et al. 2006; Maiolino et al. 2009; Walter et al. 2009; ≈ 4.0 and 3.2 kpc respectively (Taniguchi et al. 2005). Stacey et al. 2010; Ivison et al. 2010; Wagg et al. 2010; Cox et al. 2011; De Breuck et al. 2011; Swinbank et al. 2012; Venemans et al. For MACS0647-JD the delensed half-light radius is . 0.1 2012; Walter et al. 2012a; Wang et al. 2013; Riechers et al. 2013; kpc (Coe et al. 2013). Using our LIR upper limits as Ouchi et al. 2013) an approach to LIR we can estimate ΣIR. For IOK-1 the estimated ratio is log(L /L ) ∼ −2.9, for SDF ence between the LAEs at z ∼ 4.5 with the higher red- [CII] FIR shift population. The high magnification of MACS0647- J132415.7+273058 is log(L /L ) ∼ −2.5 and for [CII] FIR JD allows us to explore an UV-SFR one order of mag- ∼ − SDF J132408.3+271543 is log(L[CII]/LFIR) 2.6. For nitude lower than the ones of the LAEs, showing the the LAEs the average of L[CII]/LFIR is similar to the aver- advantage of observing lensed galaxies to cover the in- age value for the local galaxies (Fig. 6). For MACS0647- trinsically faint population at high redshift. JD the estimated ratio is log(L[CII]/LFIR) ∼−3.2. 4.6. IOK-1 Models 4.5. SFR-L[CII] Relation Using the same procedure presented in Vallini et al. In Fig. 7 we present our L[CII] upper limits with the (2013) for the [C II] emission of Himiko, we estimate the UV-SFR estimated for the targets together with upper emission of [C II]for IOK-1 at z ∼ 7. For this simu- −1 limits detections for published LAEs (Carilli et al. 2013; lation, the star formation rate was set to 20 M⊙yr Kanekar et al. 2013; Ouchi et al. 2013). The black solid and a stellar population age of 10 Myr. The metallic- lines corresponds to the relation found by de Looze et al. ity was set to solar to have a conservative estimation (2011), with the gray area corresponding to 2σ scatter in of the [C II] emission. The simulation does not include the relation. Our upper limits for the [C II] luminosity fall the emission from PDRs and should be seen as a lower within the scatter of the SFR-L[CII], with the exception limit. In Fig. 8, we show the [C II] emission produced by of SDF J132408.3+271543 , where the upper limit falls the three modeled phases, cold neutral medium (CNM), above the relation due to the moderate depth of its ob- warm neutral medium (WNM) and the ionized medium. servations. The detection of the LAE at z=4.7 (Lyα -1) Most of the [C II]emission comes from the CNM (∼ 50%), agree very well with the relation found by de Looze et al. the rest is coming from the WNM (∼ 20%) and from the (2011) using the UV-SFR estimated by Ohyama et al. ionized medium (∼ 30%). For comparison, in Himiko, (2004). The upper limits for the lensed LAE at z =6.56 95% of the emission is produced in the CNM and the HCM 6A and Himiko suggest that LAEs at z > 6 could rest in the WNM. No emission from the ionized medium fall below the relation found at low redshift. More obser- was modeled in the simulation of Himiko (Vallini et al. vations are needed to clarify if there is an intrinsic differ- 2013). We can also see in the emission that the FWHM Search for [CII] emission in z =6.5 − 11 star-forming galaxies. 9
1044 Local Galaxies IOK-1 SDF J132415.7+273058 1043 SDF J132408.3+271543 MACS0647-JD Himiko HCM 6A ] 42 Lyα-1 z=4.7 -1 10 [erg s 1041 [CII] L
40 10