PoS(Bash11)023 , d http://pos.sissa.it/ , ]. 1 , Steven R. Majewski c , color of the stream’s is consistent with , R. Jay Gabany R b − B [email protected] , g [email protected] [email protected] , f , , † , David Martínez-Delgado ∗ a , ‡ satellite in the last few Gyr. The

M , Ignacio Trujillo 8 e 10 ∼ [email protected] dwarfs and is alsoour similar measurement to uncertainties. the Additionally, we outer identify regions several of othertures low M63’s that surface disk may brightness and be fea- stellar related to halo the within with ’s complex the spiral disruption structure of or the may be galaxy’sdeep, tidal outer panoramic debris stellar optical associated disk view as of a M63 with resultthe additional possible of existing effects the multiwavelength of accretion data, such event. we an describe Using accretion our event in the larger picture of the parent galaxy. Speaker. This contribution includes data taken atFollowing The its McDonald presentation Observatory at of this The symposium, University this of research Texas at was Austin. published unabridged [ We present surface photometry ofnearby a spiral giant, galaxy low M63 surface (NGCresulting brightness from 5055) stellar the that arc disruption is in of the consistentphology a and halo with dwarf its satellite of being photometric galaxy. the properties, a we Using partof estimate the a that of stream’s the a “great-circle” stream mor- stellar originates from stream the accretion ‡ ∗ † Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. c

Frank N. Bash Symposium 2011: NewOctober Horizons 9-11, in 2011 Astronomy Austin, Texas, USA [email protected] [email protected] Taylor S. Chonis Photometry of the Stellar Tidal StreamMessier in 63 the Halo of Department of Astronomy, University of Virginia McDonald Observatory, University of Texas atInstituto Austin de Astrofísica de Canarias Departmento de Astrofísica, Universidad de LaE-mail: Laguna Gary J. Hill Department of Astronomy, The University ofMax-Planck Texas at Institut Austin für Astronomie BlackBird Observatory f e c g a b d PoS(Bash11)023 R − color ]. An B 2 R − B Taylor S. Chonis ) for features with c 1 0 has an uncertainty of . ). A detailed description 1 measurement uncertainty. 26 − ). The arc is reminiscent of 1 σ = px R 00 µ ]. We aim to determine the basic 1 ) filters with the McDonald Obser- R ( ]. It is also consistent with the 8 color index map ( B R − FOV at 1.354 ]. Several Local Volume spirals display sig- 0 3 B 6 , . tilt with respect to the inner disk isophotes. The 2 ◦ -band image. Also shown are our final data prod- 2 42 )[ 8 R 5 isophote within the 1 . 2 . × − 0 ) and a 2 , is 3.3 kpc (in projection). The stream has an average 23 b . w 1 40 kpc, displays a pronounced HI warp, and hosts a Type = ]. Standard data reduction methods were employed. We R < 1 2 within the FWHM, the latter of which is consistent with . µ 0 at ±

]. 5 M . 6 shows the final 30 mag arcsec 1 , 10 a 5 1 ∼ = 10 V R × µ ] and redder Local Group dwarfs [ − 8 7 B ∼ . Figure 2 ) or UV flux associated with the stellar stream. Along with the red − 01 mag. Through an extensive estimation of uncertainties, we find that random 2 . − 1 and 0 . 0 pc CDM paradigm, the merging of halos drives the evolution of . In 29 kpc (in projection) from the center of M63 (see Figure < 27. , it can be seen that existing multiwavelength data shows that there is little to no HI gas Λ ±

-band surface brightness map ( ≈ ]. Here, we present deep follow-up surface photometry of the outer regions of M63, a 2 1 R 4 . M . R R 26 µ 10 The most striking low surface brightness feature we observe is the coherent arc structure that We obtained 6.5 (5.33) hrs of total exposure through In the . 1 mag arcsec 0 = . . 0 R < µ noise is insignificant for asystematic typical uncertainty. measurement A while measurement the of a background diffuse subtraction feature is with the limiting reaches utilize a row-by-row and column-by-column backgroundals fitting to routine adaptively with low-order fit polynomi- were and used subtract for the photometric background. calibration.the We FOV “Tertiary” correct to SDSS for standards Galactic extinction, in which the is target uniform field over ± 23 3. The Stellar Stream ellipse fit to the light distributionFWHM displays of a the 14 stream’s light distribution, ( measured in this work, these data suggest that the stream is composed of an old stellar population. ucts: an an average S0 galaxy [ natures of recent minormodels mergers [ and show striking qualitative agreement with the cosmological 2. Observations vatory 0.8 m telescope and PFCof imager (46 the data analysis can be found in [ a “great-circle” stellar tidal stream that would result from a tidally disrupted satellite galaxy [ color of the outer disk of M63 at the the present epoch, minor mergers,the which often inside-out, alter are stellar expected disks todisks, and warps, be help and common. build stellar stellar tidal The halos debris)lations from signatures should predict be of that visible these for most interactions several large Gyr.to (such spiral Recent sufficient galaxies as cosmological depth should heated simu- (e.g., show signs of minor interactions if observed galaxy that displays clear evidence of a recent minor merger [ Photometry of the Stellar Tidal Stream in the Halo of Messier 63 1. Introduction properties of what remains ofevent the on progenitor the satellite galaxy parent and system.has study a M63 the stellar effects is mass of an of the isolated,1 accretion flocculent extended SA(rs)bc UV (XUV) spiral. disk [ It is 7.2 Mpc distant, In Figure PoS(Bash11)023 ). is 1 R µ 7 that CDM Λ < z measured is measured. < w -band surface w R - dimmer than the Taylor S. Chonis . This is similar and b 2

− R M colors that could be 8 ]. The stream’s 26. R 2 Panel 10 ≈ color index map overlayed ]. − × R 1 R B µ 5 . − 3 B 1 mag arcsec ≈ - ∼ c - We estimate the current stream m Panel 1). Several other faint features have red . 1 27. < . R ]. The time since disruption depends linearly R 3 − µ ], we find that ], which suggests a very recent disruption of the , from the stream’s morphological characteristics t 5 2 2 mag for a feature with 3 is not conclusive from our data. We thus use the B [ . . 0 1 Ψ ± − - We have presented data that make a strong case for for 23 are -band image of M63. The directional arrows in the lower-right a R R - Our data do not provide the current position or fate of a − B 180 km s ]. Assuming a near circular orbit and using 9 ≈ ] and is consistent with the prominent satellites from 1 ) CDM simulations [ 8 R - The final Λ ( a circ v ; all such features have b 2 Panel . A tri-color overlay of the M63 stellar disk is also shown [ R ]. “Great-circle” streams that are still-bound result from recent accretion events µ 3 , 2 (12.6 kpc) long. The blue arrows indicate the location along the stream where 0 Optical data: , and the time since the initial disruption, -band image. Typical errors in Origin of the Faint Light Features Estimation of the Stream’s Basic Dynamical Properties Fate of the Progenitor Dwarf colors that are similar to the outer disk isophotes and stellar stream and appear asymmetric R m , the stream’s angular length; however, • • In addition to the coherent arc, we detect other low surface brightness features (see Figure • R 6 Gyr) where the progenitor is on an orbit with only mild eccentricity [ Ψ − < among the brightest of those in the simulations [ on viable candidates, it issince more the likely core that surface brightness any decreases remaining monotonically bound after the core initial is disruption. indiscerniblemass, in the stream from our data along with to several Local Group dSphs [ assemble stellar halos in the remaining bound core of the progenitorM63’s dwarf stellar galaxy. disk. It could While be there hidden are behind or several superposed faint on features with redder using the analytic framework of [ ( The red box indicates thestream’s location average of a dim break in the stream that is Some of these correspond toXUV bright disk knots (see Figure of UV flux associated with recent formation in the progenitor satellite. Figure 1: in an azimuthal manner about the inner stellar disk. 4. Discussion Photometry of the Stellar Tidal Stream in the Halo of Messier 63 corner are 6 brightness contour map derived from panel on the B the faint features aroundsatellite M63 galaxy. being the The stream’s result morphology of resembles an the ongoing “great-circle” minor stellar accretion streams event in involving a simulations [ PoS(Bash11)023 , ≈ A ) R color m CDM L ( GALEX Λ R A ]. In both R − 6 Σ B 5). The dim . = 1, and the two 0 Taylor S. Chonis m ≈ - Archival & η isophote [ b η 2 − Panel . 2 − , we find that A pc , from the stream’s R

m L M 25 AB mag arcsec . 27 = FUV 4 µ ]. This could homogenize the integrated color of ). The knots of star formation at large radii within a 11 , we measure the stream’s surface luminosity density ) as well as the color distribution about M63 (which 2 a m 1 parameterization within η - Comparison of the optical image (grayscale) with the distribution ). is the number of wraps the stream makes around M63) so that a b - The data hints at the inside-out formation of the stellar halo. 2 η ]. The detection limit is 0.10 5 ] (see Figure 5 Panel ). Using the (where ejected disk stars [ 2 ) and estimate a mass-to-light ratio, 2 πη − resolution [ 2 and ] (see Figure pc 00 6 = . Our data only clearly show a single coherent arc (i.e.,

are subsequently in agreement. From our data, there is no evidence supporting Ψ R M L m 8 ) possibly suggests only a single loop. If this situation is the case, c 10 color similarity between the outer disk and the stream is consistent with recent 1 Multiwavelength data: × Gyr. As an alternate estimation of R η η Effect on the Parent System − ) 8 . 2 This research is a useful step in studying these elusive, yet important pieces of the galactic evo- • B 1 (in units of ]. Using the results of the ellipse fit to the stream’s light distribution, a sky projected area, ± R ≈ 4 10 break in the otherwise coherentleading stellar and stream trailing (which tidal may arms; indicate see the Figure location of the ends of the lutionary and cosmological puzzles. Similar observations in statistically significant samples will is estimated (in units of pc ( estimations of The is redder on the easternsee half Figure of the galaxy where possibly the streamadditional is stream above wraps. M63’s disk plane; the stars in the twowe structures. detect could Several be of starscomponent. the ejected faint, from The the redder, accretion disk. event and could azimuthally Thesespiral also asymmetric stars structure be in may features responsible the eventually for HI settle the disk intothese large [ spiral a HI arms thick warp that disk and make the uping extended the accretion XUV event disk [ could also be caused by instabilities due to the ongo- of HI gas (blue) at 67 panels, the red dashed curve representsexamples a of segment features of in the the stream XUV ellipse disk fit. that The can black be curve associated segments outline with HI spiral structure. parameterization Σ [ simulations that show that aaccreted stellar stream halo stars after a typical minor merger can consist of a mixture of Figure 2: Photometry of the Stellar Tidal Stream in the Halo of Messier 63 FUV+NUV image. The blue contour represents the t PoS(Bash11)023 , , , 550, ApJ MNRAS MNRAS , 689, 936 Taylor S. Chonis CDM paradigm , 2001, ApJ , 2010, Λ , 2010, , 2008, , 140, 962 AJ , 142, 166 AJ , 2010, , 36, 435 , 2011, Multicolor Surface Photometry of Lenticular Stellar Tidal Streams in Spiral Galaxies of the HI Study of the Warped NGC A Petal of the Sunflower: Photometry of the ARA&A , 447, 49 5 A&A , 1998, Tracing Galaxy Formation with Stellar Halos. II. Heated Disc Stars in the Stellar Halo Interpreting Debris from Satellite Disruption in External , 173, 538 A Search for Extended Ultraviolet Disk (XUV-Disk) , 2006, Galactic Stellar Haloes in the CDM Model ApJS , 129, 630 , 2007, AJ Stellar Mass-to-Light Ratios and the Tully-Fisher Relation , 2005, , 557, 137 ApJ Dwarf Galaxies of the Local Group , 2001, Relating Substructure in Phase and Abundance Space to Accretion Histories Local Volume: A Pilot Survey with Modest Aperture Telescopes Stellar Tidal Stream in the Halo of Messier 63 (NGC 5055) 406, 744 Galaxies. I. The Data Galaxies 212 5055: a Disk/Dark Matter Halo Offset? Galaxies in the Local Universe 404, 1711 This work is partially supported by the Texas Norman Hackerman Advanced Research Pro- ]. However, this work can only bring limited results, as sky projected stream morphologies and [1] T.S. Chonis, D. Martínez-Delgado, R.J. Gabany, et al. [2] K.V. Johnston, J.S. Bullock, S. Sharma, et al. [3] A.P. Cooper, S. Cole, C.S. Frenk, et al. [4] D. Martínez-Delgado, R.J. Gabany, K. Crawford, et al. [8] M. Mateo. [5] G. Battaglia, F. Fraternali, T. Oosterloo, & R. Sancisi. [7] S. Barway, Y.D. Mayya, A.K. Kebhavi, & S.K. Pandey. [9] K.V. Johnston, P.D. Sackett, & J.S. Bullock. [6] D.A. Thilker, L. Bianchi, G. Meurer, et al. 4 [10] E.F. Bell & R.S. de Jong. [11] C.W. Purcell, J.S. Bullock, & S. Kazantzidis. gram under grant 003658-0295-2007. Weporting thank The the McDonald photometric Observatory and observations.project, its but staff whose We for data acknowledge sup- could Ray not be Gralak included for in this his abbreviated contribution proceeding. References to the broad-band colors are not sufficient toof fully the constrain stellar the debris dynamical left andobservational compositional techniques over properties and from instrumentation the will hierarchicalfaint be evolutionary structures needed process. spectroscopically. to This reasonably Future will probe advancementgalaxies better these as in allow extremely probes the of use dark of matterevolution, halos, stellar as and streams tools around as for external studying a thetions. means effect of of Nevertheless, minor placing deep mergers on imaging more galaxy ofthat stringent relatively their constraints isolated, stellar on Local halos future Volume spiralpresents still cosmological a galaxies contain simula- unique has the opportunity shown to relics be from witnesses of their one hierarchical, of the inside-out latestAcknowledgments formation. stages of This galaxy evolution. Photometry of the Stellar Tidal Stream in the Halo of Messier 63 provide an important test of[ the cosmological simulations that are based on the