J/ApJ/737/86 UCD galaxies in the Coma cluster (Chiboucas+, 2011)
Ultra-compact dwarfs in the Coma cluster.
Chiboucas K., Tully R.B., Marzke R.O., Phillipps S., Price J., Peng E.W.,
Trentham N., Carter D., Hammer D.
<Astrophys. J., 737, 86 (2011)>
=2011ApJ...737...86C 2011ApJ...737...86C
ADC_Keywords: Clusters, galaxy ; Galaxies, spectra ; Radial velocities ;
Photometry, HST
Keywords: galaxies: clusters: individual (Coma) - galaxies: dwarf -
galaxies: star clusters: general - globular clusters: general
Abstract:
We have undertaken a spectroscopic search for ultra-compact dwarf
galaxies (UCDs) in the dense core of the dynamically evolved, massive
Coma cluster as part of the Hubble Space Telescope/Advanced Camera for
Surveys (HST/ACS) Coma Cluster Treasury Survey. UCD candidates were
initially chosen based on color, magnitude, degree of resolution
within the ACS images, and the known properties of Fornax and Virgo
UCDs. Follow-up spectroscopy with Keck/Low-Resolution Imaging
Spectrometer confirmed 27 candidates as members of the Coma cluster, a
success rate >60% for targeted objects brighter than MR=-12. Another
14 candidates may also prove to be Coma members, but low
signal-to-noise spectra prevent definitive conclusions.
Description:
This work is part of the larger Hubble Space Telescope (HST)/ACS Coma
Cluster Treasury Survey (Carter et al. 2008ApJS..176..424C 2008ApJS..176..424C), a
two-passband imaging survey designed to cover 740arcmin2 in the Coma
cluster to a depth of IC∼26.6mag for point sources.
To choose a sample of potential UCDs, we first identified point
sources in the catalog of Adami et al. (2006, Cat. J/A+A/451/1159)
based on their large ground-based Coma cluster CFHT/CFH12K survey.
We use the Keck/LRIS in multi-object spectroscopy mode. Four masks
were observed over two nights, 2008 April 2-3. Another two masks were
observed 2009 March 28-30. Observations and data reduction are further
described in Chiboucas et al. (2010, Cat. J/ApJ/723/251).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 123 49 Targeted ultra-compact dwarf galaxies (UCD)
candidates
table3.dat 123 29 *UCD sample 2
table4.dat 58 27 Effective radii
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Note on table3.dat: The second round of observations based on our expanded
candidate sample (93 lower surface brightness galaxies observed concurrently
with the 2008 four masks).
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See also:
J/MNRAS/411/2439 : Coma Treasury Survey. Structural parameters (Hoyos+, 2011)
J/ApJ/723/251 : Keck/LRIS confirmation of Coma membership (Chiboucas+, 2010)
J/ApJS/191/143 : HST/ACS Coma cluster survey. II. (Hammer+, 2010)
J/MNRAS/404/1745 : Dwarf galaxies in Coma supercluster (Mahajan+, 2010)
J/MNRAS/392/1265 : Faint red galaxies in Coma cluster (Smith+, 2009)
J/A+A/451/1159 : BVRI imaging of the Coma cluster (Adami+, 2006)
J/ApJS/137/279 : Spectroscopic Survey in Coma (Mobasher+, 2001)
J/A+A/296/643 : Low Surface Brightness galaxies in Coma (Karachentsev+ 1995)
Byte-by-byte Description of file: table[23].dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Mmb Membership status (1)
8- 14 I7 --- ID [10355/8039100] Identification number (as in
Chiboucas et al. 2010, Cat. J/ApJ/723/251),
<[CTM2010] NNNNNNN> in Simbad
15 A1 --- f_ID [f] f: object was observed in two masks
17- 21 F5.2 mag Rmag [21.06/23.99]? R-band magnitude
23- 27 F5.2 mag Imag.c ? F814W magnitude corrected (2)
29- 33 F5.2 mag Imag [21.27/24.27]? HST/ACS F814W magnitude
35- 38 F4.2 mag B-V ? B-V color index within a 3" aperture
40- 43 F4.2 mag g-i ? g-i color index within a 2.25" aperture
45- 49 F5.2 mag/arcsec2 mu0 [20/24]? Central surface brightness, R
51- 55 F5.2 mag/arcsec2 e ? Mean effective surface brightness, F814W
57- 67 F11.7 deg RAdeg Right ascension in decimal degrees (J2000)
69- 78 F10.7 deg DEdeg Declination in decimal degrees (J2000)
80- 81 I2 --- Field [1/25]? ACS field
83- 86 I4 --- xpos [181/4085]? x position in ACS field
88- 91 I4 --- ypos [89/4102]? y position in ACS field
93- 97 I5 km/s czabs [-200/81397]? Absorption radial velocity
99-101 I3 km/s e_czabs [25/154]? czabs uncertainty (3)
103-107 F5.2 aW/m2/nm Rfx [2.1/16.5]? Relative flux
(in 10-16erg/s/cm2/Å)
109-112 F4.1 --- S/N [1.6/23.6]? Signal to noise ratio per Å
around 5000Å
114-119 I6 km/s czem [44454/161089]? Emission radial velocity
121-123 I3 km/s e_czem [6/112]? czem uncertainty
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Note (1): Membership type as follows:
Mem = member. We assume that objects with radial velocities between
4000km/s<Vr<10000km/s, within 3σ of the cluster mean, and
with S/N>5 are cluster members. The spectra for the 19 confirmed
UCDs in table2 are shown in figures 2-4. The spectra for the 8
members in sample 2 (table 3) are shown in Figure 5.
Uncert = highly uncertain member
Bckgrd = Background galaxy
Stars = Foreground star
Failed = Spectra with too low S/N to even attempt redshift measurements
Note (2): Kron magnitudes corrected for light loss due to the finite size of the
Kron aperture as compared to the ACS PSF (Hammer et al.
2010ApJS..191..143H 2010ApJS..191..143H).
Note (3): Includes measurement uncertainty and uncertainty in wavelength
calibration shifts based on sky lines.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 7 I7 --- ID [81669/2000005] Identification number
8 A1 --- f_ID [b] flags a source outside ACS coverage (1)
10- 14 F5.1 pc ReGAL [4.8/125.5]? GALFIT effective radius
16- 19 F4.1 pc e_ReGAL [2.3/18.8]? ReGAL uncertainty
21- 23 F3.1 --- n [1.7/7.9]? Sersic index
25- 29 F5.2 mag Imag [21.29/23.17]? HST/ACS F814W magnitude
31- 34 F4.2 --- b/a [0.64/1]? GALFIT minor to major axis ratio (2)
36- 39 A4 --- --- [King ] ISHAPE profile
41- 43 I3 --- Mod [30/100]? ISHAPE fitting King number
45- 48 F4.1 pc ReISH [6/68.1]? ISHAPE effective radius
50- 53 F4.1 pc e_ReISH [2.4/12.2]? ReISH uncertainty
55- 58 F4.2 --- b/aISH [0.68/1]? ISHAPE minor to major axis ratio (2)
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Note (1): This object is outside of our ACS coverage. Although this object has
been observed in archival WFPC2 images, the larger pixel scale makes
size measurements for such small objects impossible.
Note (2): Typical uncertainties in b/a were 0.07 and 0.05 for Galfit and Ishape,
respectively. However, for such small objects, we don't consider the
axial ratio measurements to be very reliable.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 09-Jan-2013