2011MNRAS.412.1627C

Query : 2011MNRAS.412.1627C

2011MNRAS.412.1627C - Mon. Not. R. Astron. Soc., 412, 1627-1638 (2011/April-2)

Dynamical versus stellar masses of ultracompact dwarf galaxies in the Fornax cluster.

CHILINGARIAN I.V., MIESKE S., HILKER M. and INFANTE L.

Abstract (from CDS):

The origin of ultracompact dwarf (UCD) galaxies, compact extragalactic stellar systems, is still a puzzle for present galaxy formation models. We present the comprehensive analysis of high-resolution multi-object spectroscopic data for a sample of 24 Fornax cluster UCDs obtained with VLT with Fibre Large Array Multi Element Spectrograph (FLAMES). It comprises previously published data for 19 objects which we re-analysed, including 13 with available Hubble Space Telescope (HST) photometric data. Using Virtual Observatory technologies we found archival HST images for two more UCDs and then determined their structural properties. For all objects we derived internal velocity dispersions, stellar population parameters and stellar mass-to-light ratios (M/L)* by fitting individual simple stellar population (SSP) synthetic spectra convolved with a Gaussian against the observed spectra using the NBURSTS full spectral fitting technique. For 14 objects we estimated dynamical masses suggesting no dark matter (DM) in 12 of them and no more than 40 per cent DM mass fraction in the remaining two, in contrast to findings for several UCDs in the Virgo cluster. Some Fornax UCDs even have too high values of (M/L)* estimated using the Kroupa stellar initial mass function (IMF) resulting in negative formally computed DM mass fractions. The objects with too high (M/L)* ratios compared to the dynamical ones have relatively short dynamical relaxation time-scales, close to the Hubble time or below. We therefore suggest that their lower dynamical ratios (M/L)dyn are caused by low-mass star depletion due to dynamical evolution. Overall, the observed UCD characteristics suggest at least two formation channels: tidal threshing of nucleated dwarf galaxies for massive UCDs ( ≃ 108 M☉), and a classical scenario of red globular cluster formation for lower-mass UCDs ( ≲ 107 M☉).

Based on the archival ESO VLT with Fibre Large Array Multi Element Spectrograph (FLAMES) (programme 078.B-0496) available through and Hubble Space Telescope archival data (programmes 8090 and 10129) available through


Abstract Copyright: 2011 The Authors Monthly Notices of the Royal Astronomical Society2011 RAS

Journal keyword(s): galaxies: dwarf - galaxies: elliptical and lenticular, cD - galaxies: evolution - galaxies: kinematics and dynamics - galaxies: stellar content

Nomenclature: table 2: [MHJ2008] F-NN N=6 among (Nos 13-62) added.

Simbad objects: 38

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Number of rows : 38
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 M 31 AGN 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 13622 1
2 FCOS 2-2100 GlC 03 38 00.168 -35 30 08.21     20.94 20.57   ~ 12 0
3 NAME UCD-FORS 81 GlC 03 38 06.3040671264 -35 28 58.550357136   18.85 19.31 18.80 18.18 ~ 39 1
4 NAME UCD-FORS 36 G 03 38 06.5041040184 -35 23 03.708523500     20.00   19 ~ 13 0
5 [DJG2000] UCO 27 GlC 03 38 10.3468630320 -35 24 05.798717532     19.66 19.17   ~ 12 0
6 NAME UCD28 G 03 38 10.7378772816 -35 25 46.019689176     19.97   18.68 ~ 18 0
7 [DRG2004] 92:39 GlC 03 38 12.700 -35 28 57.41     20.66 20.27   ~ 23 0
8 NAME UCD31 GlC 03 38 16.5027178944 -35 26 19.561859520     20.60   19.65 ~ 23 0
9 [JPB2015] 054.5711568-35.4418764 GlC 03 38 17.0873774160 -35 26 30.920222868     20.83 20.44   ~ 20 0
10 [MHJ2008] F-7 GlC 03 38 17.5987243392 -35 33 02.482681212     20.49     ~ 20 0
11 [MHJ2008] F-31 G 03 38 19.7994926568 -35 23 39.214416192           ~ 2 0
12 [MHJ2008] F-8 GlC 03 38 23.2407296424 -35 20 00.607683768     20.09 19.59   ~ 14 0
13 FCOS 2-2106 GlC 03 38 25.0480862136 -35 29 25.149415668     20.51     ~ 9 0
14 FCOS 1-2024 GlC 03 38 25.5469146744 -35 37 42.618471816     20.06 19.50   ~ 18 0
15 [JPB2015] 054.6176396-35.4272815 GlC 03 38 28.3572375336 -35 25 38.311964472     20.371   19.332 ~ 18 0
16 [MHJ2008] F-12 G 03 38 28.9789910448 -35 22 56.105739516     19.87     ~ 17 0
17 NGC 1399 rG 03 38 29.083 -35 27 02.67 11.05 9.74 9.59 8.12   ~ 1636 1
18 [MHJ2008] F-13 G 03 38 29.2186568304 -35 27 19.839607524           ~ 2 0
19 ACO S 373 ClG 03 38 29.4 -35 27 08           ~ 2029 0
20 FCOS 0-2032 GlC 03 38 30.22 -35 21 30.9     20.78     ~ 8 0
21 NAME UCD-FORS 50 GlC 03 38 33.8218893216 -35 25 57.067738032     20.61   19.380 ~ 25 0
22 [MHJ2008] F-53 GlC 03 38 40.550 -35 29 09.70     20.93 20.35   ~ 20 0
23 FCOS 1-2080 Gl? 03 38 41.343 -35 28 46.39     20.96     ~ 7 0
24 [MHJ2008] F-18 G 03 38 41.9519250336 -35 33 12.952421316     19.70     ~ 14 1
25 [MHJ2008] F-59 GlC 03 38 48.86 -35 27 43.9     20.94     ~ 13 0
26 [BAL2007] gc319.1 GlC 03 38 49.848 -35 23 35.88     20.96 20.31   ~ 8 0
27 CGF 1-4 GlC 03 38 54.0545340024 -35 33 33.320376180   18.5 18.06     ~ 81 1
28 NAME UCD-FORS 1 GlC 03 38 56.1843430272 -35 24 48.907687176     20.31   19.29 ~ 9 0
29 FCOS 1-60 GlC 03 39 17.6834039208 -35 25 30.066435228   21.15 20.19 19.57   ~ 25 0
30 [MHJ2008] F-23 G 03 39 20.50 -36 19 14.2           ~ 3 0
31 LEDA 2793608 GiC 03 39 35.9209845336 -35 28 24.441828204   18.82 19.12     ~ 44 1
32 NAME Virgo Cluster ClG 12 30 47.8 +12 23 07           ~ 7107 0
33 M 87 AGN 12 30 49.42338414 +12 23 28.0436859 10.16 9.59 8.63   7.49 ~ 7815 3
34 SDSS J124155.33+114003.7 G 12 41 55.3338419712 +11 40 03.790134948           ~ 56 0
35 ACO 1656 ClG 12 59 44.40 +27 54 44.9           ~ 5141 2
36 NAME Centaurus A BLL 13 25 27.61521044 -43 01 08.8050291   8.18 6.84 6.66   ~ 4774 3
37 NGC 5139 GlC 13 26 47.28 -47 28 46.1           ~ 3677 0
38 NAME Local Group GrG ~ ~           ~ 9325 0

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