J/ApJS/250/17 NGVS. XXXIV. Ultracompact dwarf galaxies in Virgo (Liu+, 2020)
The Next Generation Virgo Cluster Survey.
XXXIV. Ultracompact dwarf galaxies in the Virgo cluster.
Liu C., Cote P., Peng E.W., Roediger J., Zhang H., Ferrarese L.,
Sanchez-Janssen R., Guhathakurta P., Yang X., Jing Y., Alamo-Martinez K.,
Blakeslee J.P., Boselli A., Cuilandre J.-C., Duc P.-A., Durrell P., Gwyn S.,
Jordan A., Ko Y., Lancon A., Lim S., Longobardi A., Mei S., Mihos J.C.,
Munoz R., Powalka M., Puzia T., Spengler C., Toloba E.
<Astrophys. J. Suppl. Ser., 250, 17 (2020)>
=2020ApJS..250...17L 2020ApJS..250...17L
ADC_Keywords: Clusters, galaxy; Photometry, ugriz ; Photometry, infrared ;
Magnitudes, absolute ; Radial velocities
Keywords: Ultracompact dwarf galaxies ; Globular star clusters ; Galaxy nuclei ;
Dwarf elliptical galaxies ; Virgo Cluster ; Galaxy formation
Abstract:
We present a study of ultracompact dwarf (UCD) galaxies in the Virgo
cluster based mainly on imaging from the Next Generation Virgo Cluster
Survey (NGVS). Using ∼100deg2 of u*giz imaging, we have identified
more than 600 candidate UCDs, from the core of Virgo out to its virial
radius. Candidates have been selected through a combination of
magnitudes, ellipticities, colors, surface brightnesses, half-light
radii, and, when available, radial velocities. Candidates were also
visually validated from deep NGVS images. Subsamples of varying
completeness and purity have been defined to explore the properties of
UCDs and compare to those of globular clusters and the nuclei of dwarf
galaxies with the aim of delineating the nature and origins of UCDs.
From a surface density map, we find the UCDs to be mostly concentrated
within Virgo's main subclusters, around its brightest galaxies. We
identify several subsamples of UCDs-i.e., the brightest, largest, and
those with the most pronounced and/or asymmetric envelopes-that could
hold clues to the origin of UCDs and possible evolutionary links with
dwarf nuclei. We find some evidence for such a connection from the
existence of diffuse envelopes around some UCDs and comparisons of
radial distributions of UCDs and nucleated galaxies within the cluster.
Description:
The primary source of data used in this study is the Next Generation
Virgo cluster Survey (NGVS; Ferrarese+ 2012ApJS..200....4F 2012ApJS..200....4F). The
survey footprint covers the two main subclusters of Virgo (A and B,
centered on M87 and M49, respectively) out to their virial radii
(i.e., R200=5.38° for Virgo A and 3.33° for Virgo B).
The NGVS imaging consists of short and long exposures, where the
former can be used to find ultracompact dwarf (UCD) galaxies brighter
than g∼18.5mag. All the NGVS fluxes are obtained with the
MegaCam/WirCam instruments on the CFHT (Canada France Hawaii
Telescope).
In addition to the imaging that forms the basis of this study, there
are many past spectroscopic programs targeting the Virgo cluster that
we can draw upon. Ferrarese+ 2012ApJS..200....4F 2012ApJS..200....4F summarized the
relevant programs for Virgo compact stellar systems (i.e., GCs, UCDs,
and dE, Ns) as of 2012; these include radial velocity measurements
from various Multiple Mirror Telescope (MMT)/Hectospec,
Magellan/IMACS, Very Large Telescope/VIMOS, and Anglo-Australian
Telescope (AAT)/AAOmega programs (see the paper for details). Since
then, a number of NGVS-motivated spectroscopic programs have been
undertaken (see Section 2.1).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 145 828 Photometric properties of ultracompact dwarf
(UCD) candidates
table4.dat 108 828 Structural properties and other information
for UCD candidates
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See also:
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
J/AJ/90/1681 : The Virgo Cluster Catalog (VCC) (Binggeli+, 1985)
J/A+AS/134/75 : Central Fornax Cluster. II. Galaxy spectrosc. (Hilker+ 1999)
J/ApJ/559/812 : Globular cluster system in M87 (Hanes+, 2001)
J/A+A/383/823 : Radial velocities of UCOs in Fornax (Mieske+, 2002)
J/ApJ/591/850 : Radial velocities of M49 globular clusters (Cote+, 2003)
J/ApJS/153/223 : ACS Virgo Cluster Survey. I. (Cote+, 2004)
J/A+A/418/445 : FCOS UCD galaxies radial velocities (Mieske+, 2004)
J/ApJS/164/334 : ACS Virgo Cluster Survey. VI (Ferrarese+, 2006)
J/ApJS/171/101 : GCs in the ACS Virgo cluster survey (Jordan+, 2007)
J/ApJ/655/144 : ACS Virgo Cluster Survey. XIII. (Mei+, 2007)
J/A+A/472/111 : Centaurus Compact Object Survey (Mieske+, 2007)
J/AJ/136/2295 : Ultra-compact dwarf cand. in Abell S0740 (Blakeslee+, 2008)
J/A+A/485/657 : Physical param. of Wolf-Rayet galaxies (Brinchmann+, 2008)
J/AJ/135/1567 : Bright star clusters in M51 (Hwang+, 2008)
J/ApJS/180/54 : GC candidates in ACS Virgo survey. (Jordan+, 2009)
J/AJ/142/199 : Sizes and luminosities of stellar systems (Brodie+, 2011)
J/ApJ/737/86 : UCD galaxies in the Coma cluster (Chiboucas+, 2011)
J/ApJS/197/33 : The M87 globular cluster system (Strader+, 2011)
J/MNRAS/422/885 : Ultracompact dwarf galaxies in Perseus (Penny+, 2012)
J/ApJ/760/87 : Globular clusters of M60 with HST (Strader+, 2012)
J/MNRAS/428/389 : SLUGGS GCs in early-type galaxies (Pota+, 2013)
J/A+A/570/A69 : GALEX Ultraviolet Virgo Cluster Survey. IV. (Boselli+, 2014)
J/AJ/148/32 : Globular cluster candidates in NGC 3115 (Jennings+, 2014)
J/MNRAS/443/1151 : AIMSS Project. I. Compact Stellar Systems (Norris+, 2014)
J/ApJ/806/133 : Virgo cluster ETGs: GC and galaxy diffuse light (Li+, 2015)
J/ApJ/812/34 : Properties of UCD cand. in M87/M49/M60 regions (Liu+, 2015)
J/MNRAS/450/1962 : M60 SLUGGS and Gemini/GMOS combined study (Pota+, 2015)
J/ApJ/802/30 : NGVS VI. Ultra-compact dwarfs in M87 (Zhang+, 2015)
J/ApJS/227/12 : NGVS XXV. Virgo GCs photometry (Powalka+, 2016)
J/A+A/586/A102 : UCDs in the halo of NGC1399 (Voggel+, 2016)
J/AJ/153/114 : GCs in 27 nearby ETGs from the SLUGGS survey (Forbes+, 2017)
J/ApJ/835/212 : Wide-field spectrosc. survey of GCs in Virgo (Ko+, 2017)
J/ApJ/858/102 : Gemini/NIFS and HST obs. of the galaxy M59-UCD3 (Ahn+, 2018)
J/A+A/625/A50 : Ultra compact dwarf galaxies catalog (Fahrion+, 2019)
http://astrowww.phys.uvic.ca/~lff/NGVS/ : NGVS home page
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [1/828] Sequential identification number
5- 15 A11 --- Name Ultracompact dwarf (UCD) galaxy name
17- 21 A5 --- --- [NGVS-]
22- 40 A19 --- NGVS Object name in NGVS catalog
(JHHMMSS.ss+DDMMSS.s)
42- 42 A1 --- Tobs Exposure time (l=long exposure data;
s=short exposure data)
44- 54 F11.7 deg RAdeg [181.71/193.37] Right Ascension (J2000)
56- 65 F10.7 deg DEdeg [4.84/18.19] Declination (J2000)
67- 71 F5.3 mag E(B-V) [0.016/0.07] Galactic extinction according to
Schlegel+ 1998ApJ...500..525S 1998ApJ...500..525S
73- 78 F6.3 mag g0mag [15.3/21.5] Galactic extinction-corrected,
aperture-corrected CFHT g-band magnitude (1)
80- 84 F5.3 mag e_g0mag [0/0.014] Uncertainty in g0mag
86- 91 F6.3 mag Kmag [11.99/19.03]? UKIDSS K-band magnitude (2)
93- 97 F5.3 mag e_Kmag [0.001/0.35]? Uncertainty in Kmag
99-104 F6.3 mag (u*-g)0 [-0.16/1.76]? u*-g color index (3)
106-110 F5.3 mag e_(u*-g)0 [0.001/0.03]? Uncertainty in (u*-g)0
112-117 F6.3 mag (g-i)0 [-1.23/1.35]? g-i color index (3)
119-123 F5.3 mag e_(g-i)0 [0.001/0.017]? Uncertainty in (g-i)0
125-130 F6.3 mag (g-z)0 [-1.18/1.67] g-z color index (3)
132-136 F5.3 mag e_(g-z)0 [0.001/0.05] Uncertainty in (g-z)0
138-143 F6.3 mag Denv [-2.11/0.69] Envelop parameter Δenv (4)
145-145 I1 --- UCD? [0/1] Object flag (1=confirmed or possible UCD;
0=contaminant)
--------------------------------------------------------------------------------
Note (1): Galactic extinction-corrected, aperture-corrected g-band magnitude
found within a 16 pixels (∼3") diameter aperture.
For details, see Liu+ 2015, Cat. J/ApJ/812/34
Note (2): Lawrence+ (2007MNRAS.379.1599L 2007MNRAS.379.1599L -- see II/319) UKIDSS K-band magnitude
within a 3-arcsec diameter aperture.
Note (3): Color indices measured in an 8-pixel (∼1.5") diameter aperture,
Galactic extinction corrected.
Note (4): Envelop parameter, Δenv≡g16-g32, where g16 and g32
are magnitudes in 16- and 32-pixel diameter apertures;
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Name Ultracompact dwarf (UCD) galaxy name
13- 18 F6.2 mag BMAG [-15.3/-9.2]? Absolute B band magnitude (5)
20- 25 F6.2 mag VMAG [-14.6/-8.6]? Absolute V band magnitude (5)
27- 31 F5.2 pc rh [11/96.7] Weighted mean half-light radius (6)
33- 36 F4.2 pc e_rh [0.01/9.1] Uncertainty in rh
38- 40 F3.1 [Msun] Mstar [5.3/8.9] log of stellar mass
42- 47 I6 km/s HRV [-420/222826]? Heliocentric radial velocity (7)
49- 81 A33 --- r_HRV Source for HRV (8)
83- 83 I1 --- Cl [1/6] Class parameter (9)
85- 85 I1 --- Env [0/1] Envelope (1=has obvious envelope)
87- 88 A2 --- Meth Selection method (10)
90-108 A19 --- OName Altenative names, if available
--------------------------------------------------------------------------------
Note (5): Absolute magnitudes calculated using the transformation equations,
B=u*-0.8116(u*-g)+0.1313, and V=g-0.2906(u*-g)+0.0885
(Lupton 2005;
http://www.sdss3.org/dr10/algorithms/sdssUBVRITransform.php#Lupton2005)
and a distance modulus of 31.1mag from Mei+ 2007ApJ..655...144M 2007ApJ..655...144M and
Blakeslee+ 2009ApJ..694...556B 2009ApJ..694...556B
Note (6): Weighted mean half-light radius in the g and i bands, or rh=rh,g
if an i-band measurement is not available.
Note (7): Heliocentric radial velocity or weighted mean value if multiple
measurements are available.
Note (8): The source of our adopted HRV measurement as follows:
SDSS = Abolfathi+ 2018ApJS..235...42A 2018ApJS..235...42A
NED = NASA/IPAC Extragalactic Database;
SIMBAD = SIMBAD Astronomical Database (Wenger+ 2000A&AS..143....9W 2000A&AS..143....9W)
VCC = The Virgo Cluster Catalog; Binggeli+ 1985, J/AJ/90/1681
NTT17 = NTT 2017 program;
AAT12 = Anglo-Australian Telescope (AAT)/AAOmega 2012 program;
MMT09 = Multiple Mirror Telescope (MMT)/Hectospec 2009 program;
Toloba2018 = Toloba et al. 2018ApJ...856L..31T 2018ApJ...856L..31T
Ko2017 = Ko et al. 2017, J/ApJ/835/212
MMT14 = Multiple Mirror Telescope (MMT)/Hectospec 2014 program;
Keck = Keck program;
C03 = Cote et al. 2003, J/ApJ/591/850
IMACS16 = Megallan/IMACS 2016 program;
S11 = Strader et al. 2011ApJS..197...33S 2011ApJS..197...33S
Note (9): Class parameter as follows:
1 = probable UCD (612 occurrences);
2 = dwarf nucleus (41 occurrences);
3 = background galaxy (132 occurrences);
4 = blended object (12 occurrences);
5 = star (14 occurrences);
6 = star-forming region (17 occurrences).
Note (10): Selection method (See Table 2) as follows:
m1 = Radial velocity cut (HRV<3500km/s) + half-light radius (rh) cut;
m2 = gz color selection + surface brightness (muge) cut +
g band half-light radius (rhg) cut;
m3 = gzK color selection + surface brightness (muge) cut +
half-light radius (rh) cut;
m4 = gzK color selection + surface brightness (muge) cut +
g band half-light radius (rhg) cut;
m5 = u*gz color selection + surface brightness (muge) cut +
half-light radius (rh) cut;
m6 = u*gz color selection + surface brightness (muge) cut +
g band half-light radius (rhg) cut;
m7 = u*gzK color selection + surface brightness (muge) cut +
half-light radius (rh) cut;
m8 = u*gzK color selection + surface brightness (muge) cut +
g band half-light radius (rhg) cut.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
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Liu et al. Paper XXXIV. 2020ApJS..250...17L 2020ApJS..250...17L This catalog
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 02-Nov-2020