arXiv:2010.03041v1 [astro-ph.GA] 6 Oct 2020 2 [email protected] orsodn uhr yn yo Lee Gyoon Myung author: Corresponding u egr nteheacia aayfrainmodel formation galaxy hierarchical ( the in mergers ous n etrs eas fteemre enn fea- remnant merger these of merg- Because interesting show features. that ing galaxies remnant merger (e.g. mergers past dur- produced ing structures fine have reported ellipticals nearby studies Many that galaxies. be- elliptical stages and evolutionary disk of tween snapshot a show galaxies nant srnm rga,Dprmn fPyisadAtooy Se Astronomy, and Physics of Department Program, Astronomy ome&Tor 1972 Toomre & Toomre asv litclglxe aefre i continu- via formed have galaxies elliptical Massive 8 NC48,VC78 soeo h nearby the of one is 798) VCC 4382, (NGC M85 yee sn L using 2020 Typeset 8, October version Draft okugKo, Youkyung eutn ntepcla ieaiso h Csystem. Keywords: GC the of kinematics peculiar the in resulting h akmte xeto 8.Uigtevlct iprino the of dispersion velocity 3 the be Using to M85 M85. of of mass dynamical extent matter dark the fterdhl fM5 h Gshv a eoiydseso profile dispersion velocity flat syst a BGC have the BGCs of The that M85. than of lower halo much red subpopulations. is the GC system of ax other RGC the major the from the of different along dispersion origin aligned syste an being subpop have and BGC stro GC GGCs RGCs The a the and the exhibits BGCs among system. the system distinct RGC than clearly GC the velocities properties of inner kinematic rotation the show disk-like that GGCs a find to We due entirely between. in are GGCs Csbouain aema gso 0Gr u hwn difference ([Z/H] showing metal-poor but most Gyr, the 10 are of RGCs ages mean have subpopulations GC aayM5 eoti pia pcr f8 C t8kpc 8 at GCs 89 of spectra optical obtain We M85. galaxy edvd hmit he rus legenrdGs(B/G/RGCs) GCs blue/green/red groups, three into them divide We epeetasuyo tla ouainadknmtc fgoua clu globular of kinematics and population stellar on study a present We 1 oe srnm n pc cec nttt,76Daedeok-d 776 Institute, Science Space and Astronomy Korea A T ytrosGoua lse ytmo h euirMassive Peculiar the of System Cluster Globular Mysterious 1. E X niiul(8)—glxe:sa lses eea lblrcluste globular — general clusters: star galaxies: — (M85) individual aais litcladlniua,c aais lses niiul(V individual clusters: galaxies: — cD lenticular, and elliptical galaxies: ,2 1, INTRODUCTION twocolumn 3 yn yo Lee, Gyoon Myung cwie 1982 Schweizer mtsna srpyia bevtr,6 adnStreet, Garden 60 Observatory, Astrophysical Smithsonian .I hsseai,mre rem- merger scenario, this In ). 4 nvriyo ap,41Ws end olvr,Tma L3 FL Tampa, Boulevard, Kennedy West 401 Tampa, of University tl nAASTeX63 in style ; u ta.2015 al. et Duc . 8 × 2 10 ogSoPark, Soo Hong Acpe etme 9 2020) 29, September (Accepted 12 − ∼ M yogGnPark Byeong-Gon umte oApJ to Submitted ⊙ 1 eifrta 8 a negn egn vnslately, events merging undergone has M85 that infer We . . ABSTRACT 9 n ea-ih([Z/H] metal-rich and 49) ). u ainlUiest,1Gaa-o wnkg,Sol088 Seoul Gwanak-gu, Gwanak-ro, 1 University, National oul 1 79Mc( Mpc 17.9 − itre spoe,rrl oae n aemsl old mostly have and rotate, rarely isophotes, distorted tutrsi diint t rmnn ug.However, bulge. prominent its to addition in structures rl alda EEdcooy ( dichotomy’ ‘E-E as called eral, appears. profile brightness surface the in the because S0, an not E2, an is type ical al. et Kormendy uncer- been has ( M85 of type tain. morphological the tures, n eeecsteen:()gatelpias( ellipticals giant (1) therein): references and pnigt kpc 2 to sponding tutr tterda ag f26 disky of any range radial indicate the not at does structure fitting ellipse from derived ue Sohn, Jubee 1991 21 litclglxe r iie notogop ngen- in groups two into divided are galaxies Elliptical . < R < a)wihgnrlyhv up oe n boxy- and cores cuspy have generally which mag) 5 1 eo uen-u ajo 45,Korea 34055, Daejeon Yuseong-Gu, aero, lsie 8 sa 0e eas fisdisk-like its of because S0pec an as M85 classified ) igeie al. et Binggeli lkse ta.2009 al. et Blakeslee 6 p sn h MMT/Hectospec. the using kpc 160 abig,018 USA 02138, Cambridge, 3 ugonLim, Sungsoon nmtliiis h Gsand BGCs The metallicities. in s ihter( their with , h oaincretdvelocity rotation-corrected The − ∼ G ytm eetmt the estimate we system, BGC ( m niaigtetruncation the indicating em, 2009 ltos aighge mean higher having ulations, < R < u to out hw itertto.The rotation. little shows m so 8.Ti mle that implies This M85. of is tr Gs ntepeculiar the in (GCs) sters 66 USA 3606, 0 goealrtto htis that rotation overall ng . ( 5,rsetvl,adthe and respectively, 45), ugse htismorpholog- its that suggested ) 1985 aayM85 Galaxy R 9kca itnet 8 of M85 to distance a at kpc 19 s general rs: and ) 7kc reflecting kpc, 67 = g 4 ro galaxies: — irgo) − aa Hwang, Narae ,weetelgtexcess light the where ), omnye l 2009 al. et Kormendy i ) ′′ eVuoluse al. et Vaucouleurs de 0 < R < oos All colors. 221 a 1 6 Korea 26, 4 ′′ and corre- , M profile V < , 2 Ko et al. stars, and (2) normal and dwarf ellipticals (MV > −21.5 Gemini/GMOS. We found that 55% of the GCs have mag) that lack cores, but have extra light at the cen- mean ages of about 4 Gyr, much younger than typical ter, strongly rotate with disky-distorted isophotes, and GCs. In addition, we detected a strong disk-like rota- have younger stars. Interestingly, M85 is an excep- tion of the GC system with a rotation amplitude of 148 tional case in this dichotomy. M85 is classified as km s−1. However, these results are needed to be supple- a giant elliptical galaxy according to its brightness, mented with a larger sample because this spectroscopic T − ′ MV = 22.52 mag (Kormendy et al. 2009). It has a survey covers only the small central region at R < 3 core and boxy isophotes within 1′′ from the galaxy cen- (16 kpc) although the M85 GC system is extended to ter (Ferrarese et al. 2006). These are all general prop- R = 20′ according to the photometric survey (Paper I). erties of giant ellipticals. However, M85 also shows In this study, we present a wide-field spectroscopic unusual properties that giant ellipticals rarely have. survey of the GCs in M85 to investigate the physical Several studies found that the nucleus of M85 is as properties of the GCs in the outskirts of M85. We cover young as a few Gyrs based on the spectroscopic analysis R < 30′ (156 kpc) using the Hectospec on the 6.5 m (Fisher et al. 1996; Terlevich & Forbes 2002; Ko et al. MMT. To date this GC survey covers the widest area 2018). In addition, Emsellem et al. (2007) classified around M85. This paper is organized as follows. We M85 as a fast rotator with a projected specific angu- briefly describe the spectroscopic target selection, ob- lar momentum of λR = 0.155 at one effective radius servation, and data reduction in Section 2. In Section ′′ (Re = 67 ). These properties are related to post merger 3, we identify genuine GCs, and investigate the stellar events. population and kinematic properties of GC subpopula- All these studies about the stellar light of M85 focused tions of M85. We discuss the peculiarity of the M85 GC on the central region within one effective radius. There system, and investigate the dark matter extent of M85 have been several studies that investigated a wider re- as well as dynamical mass estimation in Section 4. We gion of M85 using globular clusters (GCs) that are a summarize the results in Section 5. useful tool to study galaxy halo structures (Peng et al. 2006; Chies-Santos et al. 2011; Trancho et al. 2014). 2. OBSERVATION AND DATA REDUCTION These studies found that the GCs in M85 also show 2.1. Target selection and Spectroscopic Observation peculiar properties like the central stars in M85. In gen- We selected the spectroscopic targets from the photo- eral, GCs in massive early-type galaxies show a bimodal metric sample of GC candidates around M85 in Paper I. optical color distribution, which indicates the existence The GC candidates were identified as point-like sources of two GC subpopulations: old metal-poor (blue) and ′ in the ugi band images taken with the MegaCam at the old metal-rich (red) GCs. However, the GCs at R < 2 3.8 m Canada-France-Hawaii Telescope. We used the (10 kpc) in M85 do not clearly show a bimodal color (u − g) and (g − i) color combination to select the GC distribution (Peng et al. 2006). This implies the pres- 0 0 candidates. The magnitude range for the target selec- ence of intermediate-age GCs, indicating that their host tion was set to be 18
Table 1. Observation Log for the MMT/Hectospec Run
Mask Name α (J2000) δ (J2000) Na Exp. time Seeing Date(UT) M85-B1 12:25:24.74 +18:10:21.3 256 5 × 1440 s 1′′. 3 Mar 7, 2016 ′′ M85-B2 12:25:20.08 +18:05:08.9 260 5 × 1440 s 0. 9 Mar 16, 2016 ′′ M85-F1 12:25:26.52 +18:07:07.6 250 5 × 1800 s 1. 2 Mar 17, 2016 Note—a Number of object fibers among 300 fibers in each field. The remaining fibers are assigned to sky regions.
1(c)-(e)). We found that the completeness is almost con- (a) Photometric sample (b) Spectroscopic targets stant (∼ 30%) over entire radial and azimuthal ranges, 20 indicating that there is no bias on the target allocation along the location. The completeness is constant for the 0 bright sources with i0 < 21 mag, but decreases for the fainter sources. Dec. (arcmin) ∆ -20 In addition, we compared the color distribution of the
B1 photometric samples with that of the targets on which B2 F1 -40 fibers are assigned. The fiber allocation rate is constant 20 0 -20 20 0 -20 (∼ 30%) in the color range of 0.55 < (g − i)0 < 1.2 that ∆R.A. (arcmin) ∆R.A. (arcmin) corresponds to the GC color, indicating that there is no 1.0 (c) (d) (e) bias on the target selection. 0.8 0.6 2.2. Data Reduction and Radial Velocity Measurements 0.4 We used version 2.0 of the HSRED reduction pipeline1 0.2
Number fraction for data reduction. It includes bias and dark correction, 0.0 N(target)/N(phot) N(success)/N(target) N(success)/N(phot) flat-fielding, aperture extraction of spectra, and wave- 0 10 20 30 0 90 180 270 360 19 20 21 22 length calibration. Flux calibration was done following R (arcmin) PA (deg) i (mag) 0 the methods described by Fabricant et al. (2008). Most of the faint targets with i > 21.0 mag have low signal- Figure 1. (a) Spatial distribution of GC candidates with to-noise ratios (S/N < 5). The median signal-to-noise 18 < i0 < 22 identified by Paper I. (0, 0) indicates the center of M85. (b) Same as (a), but for spectroscopic targets. Each ratio of the spectra of GC candidates with i< 21.0 mag large circle represents a field of view of MMT/Hectospec with at 5000 A˚ is S/N ∼ 10. ◦ a 1 diameter. The solid-line, dashed-line, and dotted-line We estimated heliocentric radial velocities of spec- circles represent the M85-B1, M85-B2, and M85-F1 field con- troscopic targets using the xcsao task in the IRAF figurations. (c) Number fractions of the targets with velocity RVSAO package (Kurtz & Mink 1998). The prominent measurements to the photometric sample (solid line) and to absorption lines in the wavelength range of 3800 – 5400 the spectroscopic targets (dashed line) as a function of galac- A˚ were used to apply the cross-correlation method tocentric distance from M85. (d) Same as (c), but for as a function of position angle. (Tonry & Davis 1979). The RVSAO package presents several radial velocity templates such as spectra of an A star, M31 GCs, elliptical and spiral galaxies. We used time of 9000 s (five times of 1800 s) for one configu- 10 templates, and matched the targets with v > 3000 ration (M85-F1) to cover fainter targets. The seeing r km s−1 and v < 3000 km s−1 with galaxy and GC tem- ranged from 0′′. 9 to 1′′. 3 during the observations. The r plates, respectively. For 115 of the 645 targets, we could field coordinates and exposure times are given in Table not derive reliable radial velocities because of low signal- 1. to-noise ratios (S/N < 5). In addition, we excluded 21 We calculated the completeness of the mask de- targets fainter than the luminosity of the galaxy light sign, defined as the ratio between the targets on which fibers are allocated and photometric samples (N(target)/N(phot)), as functions of galactocentric dis- 1 This is an updated reduction pipeline originally devel- tance, position angle, and i-band magnitude (Figure oped by Richard Cool; more details can be found at http://www.mmto.org/node/536. 4 Ko et al. within the fiber, using the surface brightness profile of M85 from Kormendy et al. (2009). 140 GCs We also measured radial velocities of the M85 nucleus Stars and the M85-HCC1, and compared the measurements 120 Galaxies ) with the results in previous studies. The radial veloc- -1 100 ity of the M85 nucleus is derived to be v = 695 ± 16 r 80 km s−1, which is smaller than those in several previ- −1 ous studies, vr = 729 – 760 km s (Smith et al. 2000; 60 error (km s r
Gavazzi et al. 2004, Paper II). In the case of M85-HCC1, v 40 the radial velocity is measured to be vr = 655 ± 7 km s−1, which is consistent with the result from the SDSS 20 DR15 (Aguado et al. 2019), vr = 664 ± 5, within uncer- 0 tainties. We did not add any offset value to the radial 18 19 20 21 22 velocities we measured because the velocity measure- i0 ments for the point source M85-HCC1 agree well. We calculated the spectroscopic success rate defined Figure 2. Radial velocity errors vs. dereddened i-band as the number ratio between the targets of which radial magnitudes for the spectroscopic targets. The red filled cir- velocities are well derived and the parent photometric cles, blue open triangles, and black crosses represent the GCs, foreground stars, and background galaxies confirmed sample (N(success)/N(phot)) as a function of galac- in this study. tocentric distance from M85 (Figure 1(c)). We found that the success rates are almost constant as ∼ 30% for 3. RESULTS the whole radial ranges. For comparison, we also cal- culated the number fraction of the targets with veloc- 3.1. GC Selection and Subpopulations ity measurements to the spectroscopic targets on which We classified the observed targets into GCs, fore- fibers were allocated (N(success)/N(target)). This frac- ground stars, and background galaxies. First, there are −1 tion does not vary significantly with distance from M85. 110 background galaxies with vr > 3000 km s . The The azimuthal variations of N(success)/N(phot) and radial velocity distribution of the galaxies in the Virgo N(success)/N(target) are similar to their radial varia- Cluster field shows a clear separation at vr = 3000 km tions (Figure 1(d)). Therefore, we conclude that there is s−1 (Kim et al. 2014). We adopted this criterion to di- no bias in the velocity measurements along the target lo- vide the targets into the objects bound to the Virgo cation. In addition, we checked the N(success)/N(phot) Cluster and background galaxies. The radial velocities and N(success)/N(target) as a function of i-band mag- of the background galaxies in this sample range from nitude (Figure 1(e)). We found that the radial velocities 16883 km s−1 to 151120 km s−1, which are much higher of all the bright targets with i0 < 21 mag are success- than the mean velocity of the Virgo Cluster galaxies in −1 fully measured with the mean spectroscopic success rate the survey region, vr ∼ 1056 km s (Kim et al. 2014). −1 of 40%. The targets with vr < 3000 km s are either M85 Figure 2 shows radial velocity uncertainties versus GCs or foreground stars. The radial velocity distribu- dereddened i-band magnitudes for the spectroscopic tar- tion of these targets shows two peaks clearly at vr ∼ gets classified into GCs, foreground stars, and back- 0 km s−1 and 700 km s−1 (Figure 3(a)) correspond- ground galaxies (see Section 3.1). On average, brighter ing to foreground stars and M85 GCs, respectively. To sources have smaller velocity uncertainties than fainter decompose these two populations, we performed the sources. The mean radial velocity uncertainty of the Gaussian Mixture Modeling (GMM; Muratov & Gnedin sources with i0 < 19.5 mag, which are mostly foreground 2010), assuming bimodal distribution with different vari- −1 stars, is 11 km s . Most of the GCs have i-band mag- ances. The p and D values derived from the GMM indi- nitudes of 19.5 Table 2. Spectroscopic and photometric properties of the GCs confirmed in this study a a b c ID α (J2000) δ (J2000) i (g − i) C vr Class (deg) (deg) (mag) (mag) (mag) (km s−1) GC01 185.892609 18.149979 19.429 ± 0.002 0.822 ± 0.003 0.02 395 ± 14 GGC GC02 185.961578 18.098152 21.175 ± 0.005 0.792 ± 0.009 0.12 884 ± 74 GGC GC03 185.973221 17.820648 20.941 ± 0.005 0.840 ± 0.008 0.14 960 ± 69 GGC GC04 186.040955 18.078588 20.691 ± 0.004 0.754 ± 0.006 0.08 734 ± 55 GGC GC05 186.095642 18.139322 20.314 ± 0.003 0.734 ± 0.005 0.07 997 ± 39 BGC Note—Table 2 is published in its entirety in the electronic edition. The five sample GCs are shown here as guidance for the table’s form and content. aCFHT/MegaCam AB magnitudes. b The inverse concentration index C defined as the i-band magnitude differences between 4- and 8-pixel-diameter aperture pho- tometry. c Classifications are BGC (blue GC with (g − i)0 < 0.7), GGC (green GC with 0.7 < (g − i)0 < 0.8), and RGC (red GC with (g − i)0 > 0.8. Table 3. Spectroscopic and photometric properties of foreground stars and background galaxies in the Hectospec field of M85 a a b ID α (J2000) δ (J2000) i (g − i) C vr (deg) (deg) (mag) (mag) (mag) (km s−1) Star001 185.835114 18.226645 20.423 ± 0.004 0.689 ± 0.006 –0.02 –146 ± 40 Star002 185.835785 18.116449 20.406 ± 0.004 0.849 ± 0.006 –0.02 0 ± 22 Star003 185.839340 18.155159 20.080 ± 0.002 1.005 ± 0.004 0.00 105 ± 20 Star004 185.846497 18.014795 20.407 ± 0.003 0.629 ± 0.005 0.00 340 ± 37 Star005 185.849579 18.077505 20.706 ± 0.004 0.789 ± 0.006 0.02 169 ± 64 Galx001 185.882706 18.143103 21.300 ± 0.006 0.554 ± 0.009 0.32 46086 ± 6 Galx002 185.896484 17.997314 21.896 ± 0.011 0.618 ± 0.015 0.25 31115 ± 10 Galx003 185.900116 17.980145 21.834 ± 0.010 0.489 ± 0.013 0.31 46201 ± 11 Galx004 185.904617 18.043806 19.892 ± 0.002 0.955 ± 0.004 0.38 34970 ± 9 Galx005 185.906403 18.110588 21.971 ± 0.011 0.832 ± 0.017 0.22 46142 ± 11 Note—Table 3 is published in its entirety in the electronic edition. The five sample stars and galaxies are shown here as guidance for the table’s form and content. aCFHT/MegaCam AB magnitudes. b The inverse concentration index C defined as the difference between 4- and 8-pixel-diameter i-band aperture-corrected magnitudes. −1 −1 sian widths are 111 ± 4 km s and 174 ± 15 km s , Figure 3(b) shows the (g −i)0 colors and radial veloci- respectively. According to the GMM results, we adopted ties of GCs and foreground stars confirmed in this study. −1 the point where two Gaussians cross (vr = 350 km s ) The magnitudes are based on the CFHT/MegaCam as the radial velocity criterion for dividing the targets AB system. We used a foreground extinction value into GCs and foreground stars. We consider 89 targets of E(B − V ) =0.024 mag (E(g − i) =0.049 mag) −1 with vr > 350 km s and 310 targets with vr < 350 km for M85 (Schlafly & Finkbeiner 2011). The foreground −1 −1 s to be GCs and foreground stars, respectively. Table stars show a clear sequence at vr = 0 km s with a 2 and Table 3 list photometric properties and radial ve- broad color range of (g − i)0 =0.5 − 1.15, while the GCs locities of GCs and the contaminants (foreground stars have a narrower color range of (g − i)0 = 0.55 − 1.0 −1 and background galaxies), respectively. at vr = 750 km s . Figure 3(c) displays that the 6 Ko et al. 100 (a) 5 N 50 0 Dec. (arcmin) -5 1.2 ∆ M85 (b) GCs (c) (a) stellar light (b) BGC Stars 5 1.0 0 0 0.8 Dec. (arcmin) -5 ∆ (g-i) (c) GGC (d) RGC 10 5 0 -5 -10 10 5 0 -5 -10 ∆ ∆ 0.6 R.A. (arcmin) R.A. (arcmin) ′ ′ Figure 4. (a) g-band image of a 25 × 15 field around M85 0.4 taken with CFHT/MegaCam (Paper I), including NGC 4394 -500 0 500 1000 0 20 40 60 (east) and IC 3292 (west). (b) Spatial distribution of BGCs -1 vr (km s ) N overlaid on the g-band image. (c)-(d) Same as (b), but for GGCs and RGCs. Figure 3. (a) Radial velocity distribution of the spectro- −1 scopic targets with vr < 3000 km s . The dashed line indi- possibility that M85 has an intermediate-color GC pop- cates the GMM result for their radial velocity distribution. ulation with a mean color of (g − i)0 ∼ 0.78 based on − (b) (g i)0 colors vs. radial velocities of the foreground stars the GMM tests despite a high uncertainty of its num- (blue open triangles) and GCs (red filled circles) confirmed ber fraction. Because we identified a velocity peculiarity in this study. The thick solid line indicates rolling averages of these green GCs (GGCs) with 0.7 < (g − i)0 < 0.8, of velocities as a function of (g − i) color with moving bins 0 we consider them as a separate population in addition of N = 12. The thin solid lines at either side show the − standard deviation from the mean values. (c) (g − i) color to blue GCs (BGCs) with (g i)0 < 0.7 and red GCs 0 − distribution of the foreground stars (dashed line) and GCs (RGCs) with (g i)0 > 0.8. The numbers of the BGCs, (solid line). The horizontal arrows indicate three peaks in the GGCs, and RGCs in M85 are 41, 32, and 16. The sub- (g − i)0 color distribution of the parent photometric sample population information of the GCs is also listed in Table derived from the GMM test (Paper I). The two dotted ver- 2. tical lines indicate the radial velocity criterion for dividing Figure 4 shows spatial distributions of the GC v −1 the targets into GCs and foreground stars ( r = 350 km s ) subpopulations within a 25′ × 15′ field, focusing on and the radial velocity of the M85 nucleus derived in this −1 three galaxies: M85, NGC 4394 (east), and IC 3292 study (vr = 696 km s ). The two horizontal lines are the color criteria for dividing the GCs into blue, green, and red (west). Panel (a) displays the g-band image taken with ((g − i)0 = 0.7 and 0.8). CFHT/MegaCam (Paper I), showing fine structures of M85 such as shells and ripples, reaching galaxies on either side. Especially, prominent shells are extended (g − i)0 color distribution of the GCs shows a domi- along the NE-SW direction. In addition, we detect a nant peak at (g − i)0 = 0.675 and a much weaker peak warped faint stellar halo of IC 3292. The spatial distri- at (g − i)0 = 0.925, which is consistent with those of the parent sample (Paper I). The foreground stars have bution of the BGCs is more extended than that of the RGCs. Interestingly, the GGCs are lined up in the di- a strong blue peak at (g − i)0 =0.575 and a red tail in rection of NE-SW. We will investigate and discuss the the (g − i)0 color distribution. We calculated rolling averages of velocities as a func- spatial and kinematic peculiarities of the GC subpopu- lations in the following sections. tion of (g − i)0 color with moving bins of N = 12, and Figure 5 shows i0 − (g − i)0 color magnitude di- note that intermediate-color GCs with 0.7 . (g − i)0 . 0.8 have radial velocities higher than the other GCs (Fig- agrams for point-like sources (gray dots) detected in ure 3(b)). It has been known that the GCs in M85 show the CFHT/MegaCam images (Paper I) as well as the a trimodal color distribution, while the GCs in mas- GCs (red filled squares) and foreground stars (open dia- sive early-type galaxies often show a bimodal color dis- monds) confirmed in this study. We divided the objects tribution (Peng et al. 2006). Paper I also suggested a into two groups according to their inverse concentra- tion indices. The inverse concentration index C is de- Kinematics of M85 GCs 7 (a) (b) (a) -0.10 < C < 0.05 (b) 0.05 < C < 0.40 1.0 18 0.5 Normalized flux 20 BGC (co−added) GGC (co−added) 0 0.0 i (c) (d) 1.0 CaII HK Hα 22 NaD 0.5 Hβ Mgb GCs Stars Normalized flux G band RGC (co−added) M85 nucleus 0.0 4000 5000 6000 4000 5000 6000 7000 0.2 0.4 0.6 0.8 1.0 1.2 0.2 0.4 0.6 0.8 1.0 1.2 1.4 λ λ 0 [Å] 0 [Å] (g-i)0 (g-i)0 Figure 5. i0 −(g−i)0 CMDs for the point-like sources (dots) Figure 6. Co-added spectra of (a) 41 BGCs, (b) 32 GGCs, from Paper I with (a) −0.10 R (kpc) Table 4. Mean ages, [Z/H], and [α/Fe] values of the M85 0 50 100 150 nucleus and GC subpopulations (a) All (b) ) 1500 -1 Target Age [Z/H] [α/Fe] S/N 1000 (km s r v 500 (Gyr) (dex) (dex) at 5000 A˚ +<0.1 +0.28 +0.13 BGC 14.0− −1.49− 0.24− 38 (c) BGC (d) 5.5 0.04 0.37 ) 1500 GGC 11.1+3.4 −0.91+0.20 0.15+0.09 45 -1 −3.2 −0.12 −0.09 1000 +2.1 − +0.22 +0.06 RGC 9.9− 0.45− 0.19− 28 (km s 3.7 0.11 0.16 r +<0.1 +<0.01 +<0.01 v 500 M85 nucleus 2.9−<0.1 0.26−0.01 0.24−0.01 304 (e) GGC (f) ) 1500 -1 1000 (km s r v 500 +3.4 +2.1 11.1−3.2, and 9.9−3.7 Gyr, respectively, which are con- (g) RGC (h) sistent within uncertainties. On the other hand, the ) 1500 -1 GC subpopulations show differences in their metallici- 1000 (km s GCs ties. The BGCs and RGCs have mean metallicities of r v 500 Virgo dwarfs − +0.28 − +0.22 [Z/H] = 1.49−0.04 and 0.45−0.11, respectively, show- ing that they are the most metal-poor and the most 0 5 10 15 20 25 30 0 5 10 15 20 R (arcmin) N metal-rich populations. They are consistent with those in other galaxies with the same luminosity of M85 Figure 7. (a) Radial velocity vs. galactocentric distance (MB = −21.28 mag; Binggeli et al. 1985), according from M85 for all GCs. The filled circles and crosses repre- to the GC mean metallicity and host galaxy luminos- sent the GCs and Virgo dwarf galaxies in the survey region ity (Peng et al. 2006). The GGCs in M85 have a mean (Kim et al. 2014), respectively. The dashed and dotted lines +0.20 indicate the radial velocity of M85 nucleus and the criteria metallicity of [Z/H] = −0.91− , which is between 0.12 used to divide the targets into GCs and foreground stars those of the BGCs and RGCs. The α-element abun- −1 (vr = 350 km s ), respectively. (b) Radial velocity distri- dances of the GC subpopulations range from 0.15 to bution of all GCs. Panels (c)-(d), (e)-(f), and (g)-(h) are the 0.24, but it is hard to tell any significant difference be- same as (a)-(b), but for BGCs, GGCs, and RGCs, respec- cause of large uncertainties. tively. We derived the age and metallicity of the M85 nucleus to be about 2.9 Gyr and [Z/H] = +0.26, which are sim- vals. We adopted the differences between these values ilar to those derived using the Gemini/GMOS optical and the parameters measured from the actual parent spectrum in Paper II. This shows that the stellar pop- data as uncertainties. ulation in the M85 nucleus is much younger and more We compare the mean radial velocities, rotation prop- metal-rich than any GC subpopulation identified in this erties, and velocity dispersions of the GC subpopula- study. We could not find any GC population that were tions in the following sections. Table 5 lists the kine- formed when the central star formation occurred in the matic parameters derived for the entire GC, BGC, GGC, nucleus of M85, while Paper II found an intermediate- and RGC systems. age GC population within R = 3′. This implies either that the intermediate-age GCs rarely exist in the outer 3.3.1. Mean radial velocities region of M85. Figure 7 shows radial velocity distributions of all GCs and GC subpopulations confirmed in this study as a 3.3. Kinematics of the GC System in M85 function of galactocentric distance from M85. All GCs We investigate kinematic properties of the GC system are located in the radial range of 1.′5 Table 5. Kinematics of GC Systems in M85 R R N vr σr ΩR Θ0 σr,cor ΩR/σr(,cor) (arcmin) (arcmin) (km s−1) (km s−1) (km s−1) (deg) (km s−1) All GCs: 89 GCs with 0.6 < (g − i)0 < 1.0 +19 +9 +52 +26 +11 +0.33 1.5–31.0 8.6 89 754−19 165−14 80−12 156−46 163−11 0.49−0.07 +23 +10 +35 +7 +10 +0.33 1.5–5.9 3.9 48 740−25 152−17 150−37 188−13 132−17 1.13−0.27 +30 +17 +100 +45 ··· +0.59 6.0–31.0 14.1 41 769−30 177−25 198−78 78−13 1.12−0.43 BGCs: 41 GCs with 0.6 < (g − i)0 < 0.7 +30 +14 +68 +22 ··· +0.38 1.5–23.9 9.4 41 727−29 168−23 50−64 162−116 0.30−0.28 +39 +18 +86 +98 ··· +0.64 1.5–5.9 4.4 17 706−40 144−34 59−95 44−11 0.41−0.71 +38 +17 +64 +19 ··· +0.32 6.0–23.9 12.9 24 742−40 181−31 136−66 175−49 0.75−0.27 GGCs: 32 GCs with 0.7 < (g − i)0 < 0.8 +30 +15 ············ 1.9–31.0 9.5 32 812−27 156−24 +39 +13 ············ 1.9–5.9 3.6 16 818−34 139−28 +48 +21 ············ 6.6–31.0 15.5 16 805−44 170−45 RGCs: 16 GCs with 0.8 < (g − i)0 < 1.0 +37 +14 +41 +5 +20 +1.65 1.7–20.3 4.8 16 704−37 141−26 203−42 197−7 95−36 2.15−0.49 +43 +16 +41 +5 +16 +2.37 1.7–5.3 3.7 15 695−38 142−31 208−42 196−7 66−25 3.16−0.53 GGCs that have a much higher mean radial velocity +30 −1 1.0 of vr = 812−27 km s . If the GGCs are excluded, the +23 BGCs mean radial velocity of the GCs drops to vr = 721−21 km GGCs s−1. In addition, the BGCs and RGCs have the mean RGCs +30 −1 ± 0.8 radial velocities of vr = 727−29 km s and 704 37 km s−1, respectively. These mean radial velocities measured without the GGC population are consistent with the radial velocity of the M85 nucleus within uncertainties. 0.6 We performed two-sided Kolmogorov-Smirnov (K-S) tests to compare the radial velocity distributions of GC subpopulations. Figure 8 shows the cumulative radial 0.4 velocity distributions of BGCs, GGCs, and RGCs in Cumulative Fraction M85. The p-value for the BGCs and RGCs is 0.46, from pKS, B-G = 0.07 which we cannot tell a clear difference between their 0.2 pKS, B-R = 0.46 velocity distributions. However, the p-values for the p = 0.07 B/RGCs and GGCs are 0.07, meaning that the GGCs KS, G-R have a radial velocity distribution clearly distinct from 0.0 those of both BGCs and RGCs. 400 600 800 1000 1200 v (km s-1) In Figure 7 we also plot the radial velocities of dwarf r galaxies in the Virgo Cluster for comparison with the M85 GC kinematics. We adopted the radial velocities Figure 8. Cumulative radial velocity distributions of BGCs (dashed line), GGCs (solid line), and RGCs (dotted line). of Virgo galaxies from the Extended Virgo Cluster Cata- log (EVCC; Kim et al. 2014). There are only four dwarf galaxies in our survey region: VCC 797 (EVCC 556) at whether these dwarf galaxies constitute a distinguish- R =3.′1, VCC 751 (EVCC 529) at R =8.′5, EVCC 671 able group associated with M85 or they are governed at R = 18.′7, and EVCC 629 at R = 24.′6. Two of them by the gravitational potential of the Virgo Cluster. We have radial velocities similar to the M85 velocity (vr = will discuss the kinematic differences between M85 GCs 696 km s−1 for VCC 751 and 703 km s−1 for EVCC 617), and Virgo dwarf galaxies with regard to the dark matter but the other two have much higher velocities (vr = 1228 extent of M85 in Section 4.2. km s−1 for VCC 797 and 1408 km s−1 for EVCC 629). 3.3.2. Rotation Properties Because of the small number statistics, it is not clear 10 Ko et al. ∆ -1 vr (km s ) ∆v > 0 -50 0 50 100 20 ∆ r vr < 0 30 Star (E04) 0 0 -30 -20 Dec. (arcsec) Dec. (arcmin) ∆ 30 0 -30 ∆ (a) All GCs (b) Isophotes (K09) ∆ -40 R.A. (arcsec) 20 0 -20 Dec. (arcmin) ∆ (c) BGCs (d) GGCs (e) RGCs -40 20 1 2 3 4 (arcmin-2) 0 -20 Dec. (arcmin) ∆ (f) Phot. BGCs (g) Phot. GGCs (h) Phot. RGCs -40 20 0 -20 20 0 -20 20 0 -20 ∆R.A. (arcmin) ∆R.A. (arcmin) ∆R.A. (arcmin) Figure 9. (a) Spatial distribution of all GCs confirmed in this study. The red filled circles and blue open squares represent the GCs with the radial velocities higher and lower than that of the M85 nucleus, respectively. The dashed and dotted lines ′ ′ represent the photometric major/minor axes of the isophotes derived at rmaj = 3 and 10 , respectively (Kormendy et al. 2009). ′ ′ (b) Stellar light isophotes at rmaj = 3 and 10 (Kormendy et al. 2009). (c)-(e) Same as (a), but for BGCs, GGCs, and RGCs. ′ The solid-line ellipses indicate the dispersion ellipses derived with the GC subgroups within R = 20 . (f)-(h) Smoothed surface number density map of the parent photometric sample of BGCs, GGCs, and RGCs, color-coded by the number density. The ′′ ′′ solid-line ellipses are the same as in panel (c)-(e). For comparison, the SAURON stellar velocity field for the 30 × 30 region is given in the upper right corner (Emsellem et al. 2004). Kinematics of M85 GCs 11 Figure 9(a) shows the spatial distribution of the GCs 1.0 along with their radial velocities. The GCs are strongly (a) (b) concentrated around the galaxy center and show an elon- gated spatial distribution. For comparison, we plot the 0.8 isophotes of the M85 stellar light in Figure 9(b). The position angles and ellipticities of the isophotes change from 16◦ to 66◦ and from 0.18 to 0.38 as the semi-major ′ ′ 0.6 axis Rmaj increases from 3 to 10 (Kormendy et al. 2009). The GCs show a spatial distribution elongated along the major axis of the isophote of M85 at R = maj 0.4 10′. We also investigate the spatial distributions of the GC Cumulative Fraction subpopulations separately (Figure 9(c)-(e)). The BGCs 0.2 are sparsely distributed without any trend in their ra- pKS, B-G = 0.79 pKS, B-G = 0.07 p = 0.02 p = 0.04 dial velocities. In contrast, the RGCs are strongly con- KS, B-R KS, B-R p = 0.01 p = 0.31 centrated around the galaxy center and show a clear KS, G-R KS, G-R 0.0 spatial segregation between high and low radial veloc- 1 10 1 10 ity GCs. We consider that this spatial segregation of the |R | (arcmin) |R | (arcmin) RGCs indicates a rotation signature of the RGC system. major minor Interestingly, the GGCs are strongly aligned along the photometric major axis of the outer stellar isophote of Figure 10. (a) Cumulative major axis distance distributions of BGCs (dashed line), GGCs (solid line), and RGCs (dotted M85, especially for the ones with higher relative veloc- line). (b) Same as (a), but for minor axis distance. ities. These features in the spatial distributions of the spectroscopic samples are similar to those of the photo- 1980; Burgett et al. 2004; Hwang & Lee 2007) or GCs metric samples with 18 12 Ko et al. −1 The position angle of the major axis is given by velocity dispersion of σr,cor = 163 ± 11 km s . This rotation parameter value is consistent with those of GC µ − Γ2 π θ = cot−1 − 02 A + , (3) systems of massive early-type galaxies with luminosity µ11 2 +0.25 +0.27 similar to M85 (e.g. 0.45−0.24 for M84 and 0.65−0.22 for and the ellipticity is M60; Alabi et al. 2016; Hwang et al. 2008). We found that the BGC and RGC systems show ro- Γ ǫ =1 − B . (4) tation properties significantly different from each other ΓA (Figure 11(d) and (j)). The RGC system shows a strik- Figure 9(a) shows the dispersion ellipse for the entire ingly strong rotation feature with a rotation amplitude +41 −1 GC sample confirmed in this study. Its position angle of ΩR = 203−42 km s , which is almost a disk-like +5◦ ± rotation. On the other hand, the rotation amplitude of and ellipticity are θ = 65−4 and e = 0.55 0.06. For comparison, we also derived the dispersion ellipses for the BGC system is close to zero with a large uncertainty +68 −1 GC subgroups, as shown in Figure 9(c)-(e). For the (ΩR = 50−64 km s ). The orientation of the rotation RGC system, we excluded a RGC with R > 20′ that axis of the BGC system has a large uncertainty because +22 ◦ is an outlier of the overall distribution of the RGCs. its rotation feature is negligible (Θ0 = 162−116 ), but for The position angles of the dispersion ellipses for BGCs, the RGC system, it is precisely measured with a small ◦ ◦ ◦ ◦ +12◦ uncertainty (Θ = 197+5◦). The rotation parameters of GGCs, and RGCs are θ = 65 ±8 , 65 ±6 , and 64− , 0 −7 9 +0.38 respectively. They are consistent with each other, and the BGC and RGC systems are ΩR/σr =0.30−0.28 and +1.65 similar to the photometric position angle of the isophote ΩR/σr,cor = 2.15−0.49, respectively. We did not apply ′ ◦ of M85 at Rmaj = 10 (∼ 66 ). On the other hand, the rotation correction to the velocity dispersion for the the ellipticity of the GGC system (e = 0.69 ± 0.04) is BGC system because of its negligible rotation feature. 2σ higher than those of both BGC and RGC systems We did not derive the rotation parameters for the +0.11 +0.12 GGC system because most of GGCs have radial veloci- (e = 0.42− and 0.44− ), which means that the 0.10 0.13 −1 spatial distribution of the GGCs is more elongated than ties higher than the systemic velocity (∆v > 0 km s ) ◦ those of the BGCs and RGCs. and are concentrated only at the position angle of 70 ◦ In addition to the differences in the spatial distribu- and 240 (Figure 11(g)). tions of the GC subsystem, we examine their differences We additionally divide the entire GC, BGC, GGC, in the rotation features. Figure 11 shows the radial ve- and RGC samples into two groups, inner and outer sys- ′ locities of GCs as a function of position angle with the tems, with a radial criterion of R = 6 , and investi- best-fit rotation curves. The GCs rotating along a given gate their kinematics. The inner GC system has a ro- +35 −1 axis in the plane of the sky have radial velocities as a tation amplitude of ΩR = 150−37 km s and a rota- +7 ◦ function of sinusoidal position angle. We measured the tion axis of Θ0 = 188−13 , which are marginally con- rotation amplitude and position angle of the rotation sistent with those derived from the small GC sample ′ axis for the GC system by fitting the data with the fol- within R = 3 (Figure 11(b); Paper II). The rotation- lowing function: corrected velocity dispersion for the inner GC system +10 −1 is σr,cor = 132−17 km s , resulting in the rotation pa- − +0.33 vr(Θ) = vsys + (ΩR) sin(Θ Θ0), (5) rameter of ΩR/σr,cor = 1.13−0.27. This rotation pa- rameter value is two times higher than that derived for where the v is the systemic velocity, ΩR is the rota- sys the entire GC sample. This strong rotation of the in- tion amplitude, and Θ is the orientation of the rotation 0 ner GC system is mainly contributed by the RGCs. All axis. We assumed the systemic velocity to be the radial ′ −1 RGCs are located within R =6 except for one, rotating velocity of the M85 nucleus, vsys = 696 km s , as de- +41 strongly with a rotation amplitude of ΩR = 208−42 km rived in this study. −1 +2.37 s and a rotation parameter of ΩR/σr,cor = 3.16 We fitted the data with this function for the entire −0.53 (Figure 11(k)). On the other hand, the inner BGC sys- GC system of M85 (Figure 11(a)). The rotation am- tem does not show any significant rotation features (Fig- plitude and the orientation of the rotation axis of the +52 −1 +26◦ ure 11(e)). The inner BGC system has a rotation pa- GC system are ΩR = 80−12 km s and Θ0 = 156−46 . +0.64 rameter of ΩR/σr = 0.41 , which is similar to the The rotation axis is close to the minor axis of the stellar −0.71 ′ entire BGC system. Most of the inner GGCs are con- isophote at R = 10 . We calculated a rotation pa- ◦ maj centrated at the position angle of 240 , indicating a bulk rameter, ΩR/σ , defined as the ratio between the ro- r,cor motion (Figure 11(h)). tation amplitude and the rotation-corrected velocity dis- The outer GC system has a rotation amplitude of persion. The entire GC system has the rotation parame- +100 −1 +0.33 ΩR = 198−78 km s , which is comparable with the ter of ΩR/σr,cor =0.49−0.07 with the rotation-corrected Kinematics of M85 GCs 13 600 (a) All GCs (b) Inner GCs (R < 6’) (c) Outer GCs (R > 6’) 300 0 -300 -600 600 (d) All BGCs (e) Inner BGCs (R < 6’) (f) Outer BGCs (R > 6’) 300 0 -300 ) -1 -600 600 ’ ’ (km s (g) All GGCs (h) Inner GGCs (R < 6 ) (i) Outer GGCs (R > 6 ) r v ∆ 300 0 -300 -600 600 (j) All RGCs (k) Inner RGCs (R < 6’) (l) Outer RGC (R > 6’) 300 0 -300 -600 0 90 180 270 360 90 180 270 360 90 180 270 360 PA (deg) Figure 11. Radial velocities relative to the systemic velocity as a function of position angle for (a) all GCs, (b) inner GCs ′ ′ (R < 6 ), and (c) outer GCs (R > 6 ). Panels (d)-(f), (g)-(i), and (j)-(l) are the same as panels (a)-(c), but for BGCs, GGCs, and RGCs, respectively. The thick solid and dotted lines indicate the best fit rotation curves and zero velocity line, respectively. The thin solid lines show the rotation curves derived with the rotation axis ratio of q = 0.625 (see texts). The dashed line in ′ panel (b) shows the best fit rotation curve derived with 20 M85 GCs within R = 3 (Paper II). The large and small vertical ′ ′ arrows mark the photometric minor axis of M85 at rmaj = 3 and 10 , respectively (Kormendy et al. 2009). 14 Ko et al. +17 −1 R (kpc) velocity dispersion of σr = 177−25 km s . The rota- +45◦ 1 10 100 tion axis of the outer GC system is Θ0 = 78−13 , which 1200 BGCs (this study) is totally different from that of the inner GC system GGCs (this study) ) RGCs (this study) (Figure 11(c)). This is because the fitting results are -1 1000 GCs (K18) sensitive to the outer GGCs only concentrated at the Stars (F97) ◦ ◦ Virgo Dwarfs (K14) position angle of 70 and 240 (Figure 11(i)). If we only (km s 800 r consider the outer BGC system, the rotation amplitude v +64 (a) and orientation of the rotation axis are ΩR = 136−66 km 600 −1 +19◦ s and Θ0 = 175−49 (Figure 11(f)). The rotation pa- 400 +0.32 rameter of the outer BGC system (ΩR/σr = 0.75 ) −0.27 ) is higher than that of the inner BGC system, but con- -1 300 sistent within uncertainties. 200 (km s Additionally, we checked a possibility that there are r σ 100 any significant changes in the kinematic parameter mea- (b) surements if the spatial elongations of the GC systems 0 are considered in the fitting. Proctor et al. (2009) sug- 0.1 1.0 10.0 gested a rotation model considering a rotation axis ratio: R (arcmin) vrot Figure 12. (a) Mean radial velocity profiles for vmod = vsys ± (6) 2 ′ tan(Θ − PAkin) the M85 GCs at R < 2.5 (diamonds; Paper II), 1+ q M85 BGCs/GGCs/RGCs confirmed in this study (cir- r cles/stars/triangles), and Virgo dwarfs in the survey region where PA is the kinematic position angle defined as kin (cross; Kim et al. 2014). The horizontal dotted line indicates the angle from the north to the maximum receding part the radial velocity of the M85 nucleus measured in this study. of the velocity map, and q is the rotation axis ratio. The (b) Same as (a), but for radial velocity dispersion profiles. kinematic position angle PAkin is, by definition, differ- The pluses represent the stars in the central region of M85 ent from the rotation axis orientation Θ0 in equation (Fisher 1997). The horizontal dotted line indicates the ve- ◦ locity dispersion of the central region of M85 measured from (5) by 90 . This equation corresponds to the sinusoidal ′′ function we used if the axis ratio q is equal to 1. the integrated stellar light spectrum within R = 1 (86.8 pc) (Paper II). The open and filled symbols for the M85 We adopted the photometric axis ratio of the isophotes ′ GCs represent the velocity dispersions about the systemic at Rmaj = 10 (q = 0.625), which is the most extreme velocity (σr) and the rotation-correction velocity dispersions case for the elongation. The fitting results are also plot- (σr,cor), respectively. ted in Figure 11 for comparison. The rotation ampli- tudes derived with the axis ratio of q = 0.625 is slightly the GCs studied in the previous study (Paper II), and higher than the previous measurements. However, the ′ the central stars at R < 0.6 (Fisher 1997). The veloc- mean difference is only 18 km s−1, which is much smaller ity dispersion of the inner BGCs is similar to that of the than the measurement uncertainties. The orientations central stars. The outer BGCs with mean galactocentric do not show any significant differences as well. There- ′ − distance of R = 12.9 have about 40 km s 1 higher veloc- fore, we conclude that our kinematic parameter mea- ity dispersion than the inner BGCs, but this difference surements are irrelevant to the elongated spatial distri- is within uncertainties. The RGCs tightly follow the butions of the GC systems. fitted rotation curve (Figure 11(j)), resulting in a dra- 3.3.3. Mean Radial Velocity And Velocity Dispersion matic change of the velocity dispersion after the rotation Profiles correction. The rotation-corrected velocity dispersion of ′ +16 −1 Figure 12(a) shows the mean radial velocities of GCs the RGCs at R = 3.7 (σr,cor = 66−25 km s ) is much and Virgo dwarf galaxies in the survey region as a func- lower than those of both the central stars and the BGCs. tion of galactocentric distance from M85. We confirmed This indicates that the BGCs and RGCs trace different that the GGCs have mean radial velocities higher than halo components of M85 (see Section 4.2). the other GC subpopulations regardless of distance, as 4. DISCUSSION shown in Section 3.3.1. The mean radial velocity of four Virgo dwarf galaxies in the survey region is much higher 4.1. Peculiar Motions of the M85 GC System than that of GCs. We confirm a strong rotation of the inner GC sys- In Figure 12(b), we display velocity dispersion profiles tem of M85 in this study. This rotation was previously of the GCs confirmed in this study at 1.′5 − 2 2 To investigate the extent of M85 halo, we compare the eter (β = 1 σt /σr ), rout is the deprojected radius of kinematics of the GCs with that of the dwarf galaxies in the outermost tracer and the Virgo Cluster, using radial velocities of dwarf galax- π1/2Γ( α + 1) ies presented in the EVCC (Kim et al. 2014). There are 2 − Iα,β = α 5 [α +3 β(α + 2)]. (9) only four Virgo dwarf galaxies in our survey region, and 4Γ( 2 + 2 ) all of them have radial velocities higher than the M85 We adopted the γ parameter of 3.28 from the number nucleus (Figure 7). The mean radial velocity and radial density profile of BGCs based on a wide-field photomet- velocity dispersion of these dwarf galaxies are vr = 1113 − − ric survey given by Paper I. The α parameter is zero ± 158 km s 1 and σ = 316 ± 112 km s 1. for the isothermal dark matter halo which shows a flat The kinematics of the M85 GCs is totally different rotation curve and 0.55 for the NFW dark matter pro- from that of the Virgo dwarf galaxies in the survey re- file (Navarro et al. 1996; Watkins et al. 2010). The β gion in terms of both the mean velocity and velocity parameter is zero for isotropic orbits and one for purely dispersion. This indicates that the gravitational po- radial orbits. We estimated the dynamical mass uncer- tentials governing these two populations are different. tainty from the bootstrapping method. We randomly se- The mean radial velocity and velocity dispersion of the lected 41 objects from the BGCs allowing replacement, Virgo dwarf galaxies at the clustercentric distance same ◦ −1 and calculated the dynamical mass with their radial ve- as M85 (∼ 6 ) are derived to be vr = 1107 km s and −1 locities based on the TME method. In this process, σr = 327 km s , respectively (Kim et al. 2014). The the radial velocities and the slope of the number den- dwarf galaxies in our survey region have kinematics sim- sity profile of BGCs are also randomly chosen within ilar to other dwarf galaxies in the Virgo despite the small their uncertainties. We repeated this process 1000 times, sample. Therefore, we conclude that the dwarf galaxies and found the 16th and 84th percentiles of the measure- in our survey region follow the cluster potential, while ments. We adopted the differences between the mass de- the blue halo traced by the BGCs are controlled by the rived with the actual data and the 16th/84th percentiles distinguishable galaxy potential. as the uncertainty. 4.3. Dynamical Mass in M85 We estimate the dynamical mass of M85 enclosed ± × 12 We estimated the dynamical mass of M85 based on within R = 124 kpc to be MTME = (3.8 0.6) 10 M⊙, assuming the isothermal dark matter halo and the the kinematics of the GC system. The M85 GCs show clearly different kinematics according to their colors. We isotropic orbits. Previously, Sansom et al. (2006) de- only used the BGC system to derive the dynamical mass rived the mass of M85 enclosed within R = 10 kpc from × 11 of M85 because it is a pressure-supported system that X-ray hot gas observation, which is 2 10 M⊙. In ad- dition, Babyk et al. (2018) estimated the total mass of shows a negligible rotation feature. 11 M85 to be 4 × 10 M⊙ by extrapolating the total mass We estimate the pressure-supported mass of M85 using the tracer mass estimator (TME) from profiles out to 5 Re (37 kpc). These measurements are Watkins et al. (2010). The TME is a robust method 10-20 times smaller than the dynamical mass derived in to estimate the enclosed mass based on the projected this study. It is because M85 lacks hot gas, compared to other galaxies with similar luminosity (Sansom et al. positions and line-of-sight velocities of tracers. The enclosed mass based on the TME method is given by 2006), and our radial coverage is much larger than the previous studies. C N We compare the dynamical mass of M85 to those M = (v − v )2 Rα, (7) p GN los,i sys i of early-type galaxies with similar luminosity of M85. Xi Alabi et al. (2016) presented dynamical masses of 23 where N is the number of the tracers, vlos,i is the early-type galaxies derived with their GC kinematics. rotation-corrected radial velocity of a given tracer, vsys Among them, we selected 7 galaxies with K-band mag- is the systemic velocity, α is the power-law slope of the nitudes of –25.5 mag< MK < –24.5 mag, which are − underlying gravitational potential profile, and Ri is the similar to that of M85 (MK = 25.1 mag; Jarrett et al. projected galactocentric distance of the tracers. The 2003). These galaxies have pressure-supported masses 11 12 constant C is defined as ranging from 6.5×10 M⊙ to 3.26×10 M⊙ with radial coverage of R < 9 − 21 effective radii (Re). We derive α + γ − 2β − C = r1 α, (8) the enclosed mass of M85 within R = 14 R , compa- I out e α,β rable to the coverage for other galaxies, adopting the ′′ where γ is the power-law slope of the volume number effective radius of M85, Re = 102. 28 (Kormendy et al. density profile of the tracers, β is the anisotropy param- 2009). M85 has a larger dynamical mass, compared to Kinematics of M85 GCs 17 the other galaxies with similar luminosity, which indi- evolution histories. The BGCs in M85 have kinematic cates the existence of a large amount of dark matter in properties similar to those in other massive early-type M85 within R = 14 Re. galaxies, which are expected to be accreted from the dis- rupted dwarf galaxies. The metal-poor population of the 5. SUMMARY BGCs also supports this scenario. On the other hand, We present a spectroscopic study of GCs in the merger the GGCs and RGCs in M85 have peculiar kinematics remnant galaxy M85 using the MMT/Hectospec. 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