2013ApJ...775L...6S


C.D.S. - SIMBAD4 rel 1.7 - 2020.10.29CET21:56:13

2013ApJ...775L...6S - Astrophys. J., 775, L6 (2013/September-3)

The densest galaxy.

STRADER J., SETH A.C., FORBES D.A., FABBIANO G., ROMANOWSKY A.J., BRODIE J.P., CONROY C., CALDWELL N., POTA V., USHER C. and ARNOLD J.A.

Abstract (from CDS):

We report the discovery of a remarkable ultra-compact dwarf galaxy around the massive Virgo elliptical galaxy NGC 4649 (M60), which we call M60-UCD1. With a dynamical mass of 2.0x108 M but a half-light radius of only ∼24 pc, M60-UCD1 is more massive than any ultra-compact dwarfs of comparable size, and is arguably the densest galaxy known in the local universe. It has a two-component structure well fit by a sum of Sérsic functions, with an elliptical, compact (rh= 14 pc; n ∼ 3.3) inner component and a round, exponential, extended (rh= 49 pc) outer component. Chandra data reveal a variable central X-ray source with LX∼ 1038 erg/s that could be an active galactic nucleus associated with a massive black hole or a low-mass X-ray binary. Analysis of optical spectroscopy shows the object to be old ( ≳ 10 Gyr) and of solar metallicity, with elevated [Mg/Fe] and strongly enhanced [N/Fe] that indicates light-element self-enrichment; such self-enrichment may be generically present in dense stellar systems. The velocity dispersion (σ ∼ 70 km/s) and resulting dynamical mass-to-light ratio (M/LV = 4.9±0.7) are consistent with–but slightly higher than–expectations for an old, metal-rich stellar population with a Kroupa initial mass function. The presence of a massive black hole or a mild increase in low-mass stars or stellar remnants is therefore also consistent with this M/LV. The stellar density of the galaxy is so high that no dynamical signature of dark matter is expected. However, the properties of M60-UCD1 suggest an origin in the tidal stripping of a nucleated galaxy with MB∼ -18 to -19.

Abstract Copyright:

Journal keyword(s): galaxies: dwarf - galaxies: elliptical and lenticular, cD - galaxies: individual: M60 - galaxies: kinematics and dynamics - galaxies: star clusters: general

Nomenclature: [SSF2013b] M60-UCD1 N=1.

Simbad objects: 15

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Number of rows : 15

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NAME Mayall II GlC 00 32 46.53 +39 34 40.5   14.564 13.807 13.208 12.684 ~ 371 1
2 M 32 IG 00 42 41.825 +40 51 54.61 9.51 9.03 8.08     ~ 2022 2
3 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 11057 1
4 NGC 1389 GiP 03 37 11.7424496792 -35 44 45.871664087 12.80 12.39 11.50 10.99   ~ 175 1
5 ACO S 373 ClG 03 38 30 -35 27.3           ~ 1568 0
6 IC 2006 EmG 03 54 28.427 -35 58 01.75   12.39   10.94 11.9 ~ 196 0
7 NAME Hydra I Cluster ClG 10 36 36.0 -27 31 04           ~ 777 1
8 NGC 4379 GiG 12 25 14.7451190451 +15 36 26.750240178 13.05 12.63 11.72     ~ 210 1
9 NGC 4387 GiG 12 25 41.6768872639 +12 48 37.809497625 13.42 13.01 12.12   10.87 ~ 372 1
10 M 87 BiC 12 30 49.42338230 +12 23 28.0438581 10.16 9.59 8.63   7.49 ~ 6283 3
11 NAME M59cO G 12 41 55.3339496460 +11 40 03.789131845           ~ 44 0
12 NAME M60-UCD1 G 12 43 35.964 +11 32 04.69           ~ 74 0
13 [LFS2013] 144 X 12 43 35.98 +11 32 05.1           ~ 1 0
14 M 60 GiP 12 43 40.008 +11 33 09.40   10.3       ~ 1258 0
15 ACO 1656 ClG 12 59 48.7 +27 58 50           ~ 4269 2

    Equat.    Gal    SGal    Ecl

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2020.10.29-21:56:13

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