2011ApJ...743..179B

Query : 2011ApJ...743..179B

2011ApJ...743..179B - Astrophys. J., 743, 179 (2011/December-3)

What sets the sizes of the faintest galaxies?

BRASSEUR C.M., MARTIN N.F., MACCIO A.V., RIX H.-W. and KANG X.

Abstract (from CDS):

We provide a comprehensive description and offer an explanation for the sizes of the faintest known galaxies in the universe, the dwarf spheroidal (dSph) satellites of the Milky Way and Andromeda. After compiling a consistent data set of half-light radii (r1/2) and luminosities, we describe the size-luminosity relation of dSphs by a log-normal distribution in r1/2 with a mean size that varies as a function of luminosity. Accounting for modest number statistics, measurement uncertainties, and surface brightness limitations, we find that the size-luminosity relations of the Milky Way and Andromeda dSph populations are statistically indistinguishable and also very similar: their mean sizes at a given stellar luminosity differ by no more than 30%. In addition, we find that the mean size, slope, and scatter of this log-normal size description of Local Group dSphs match onto the relation of more massive low-concentration galaxies. This suggests that the stellar sizes of dSphs are ultimately related to their overall initial baryonic angular momentum. To test this hypothesis, we perform a series of high-resolution N-body simulations that we couple with a semi-analytic model of galaxy formation. These predict the same mean size and slope as observed in dSph satellites. At the same time, these models predict that the size-luminosity distributions for satellite galaxies around similar host halos must be similar providing a natural explanation as to why the size distributions of Milky Way and Andromeda satellites are similar. Although strong rotation is currently not observed in dSphs, this may well be consistent with our angular-momentum-based explanation for their sizes if the disks of these galaxies have become sufficiently stirred through tidal interaction.

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Journal keyword(s): galaxies: dwarf - galaxies: structure - Local Group

Simbad objects: 50

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Number of rows : 50
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 NAME Andromeda XVIII G 00 02 14.5 +45 05 20     16.0     ~ 129 0
2 NAME Andromeda XX G 00 07 30.70 +35 07 56.4     18.2     ~ 77 0
3 ESO 349-31 AG? 00 08 13.1536 -34 34 47.836   15.54   14.99   ~ 156 3
4 And XIX G 00 19 32.10 +35 02 37.1     15.6     ~ 168 0
5 NAME Andromeda XXVI G 00 23 45.6 +47 54 58     17.3     ~ 76 0
6 NAME Cetus Dwarf Galaxy G 00 26 10.8 -11 03 14     13.2     ~ 257 0
7 NAME Andromeda XXV G 00 30 08.9 +46 51 07     14.8     ~ 120 0
8 NAME Andromeda III G 00 35 33.8 +36 29 52     14.4     ~ 309 0
9 NAME Andromeda XVII G 00 37 07.0 +44 19 20     15.8     ~ 101 0
10 NAME Andromeda XXVII G 00 37 27.1 +45 23 13     16.7     ~ 82 0
11 M 31 AGN 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 13622 1
12 NAME Andromeda I G 00 45 39.8 +38 02 28   13.9 12.7     ~ 355 0
13 NAME Andromeda XI G 00 46 20.0 +33 48 05     17.5     ~ 130 0
14 NAME Andromeda XII G 00 47 27.0 +34 22 29     18.3     ~ 124 0
15 NAME Andromeda XIV G 00 51 35.0 +29 41 49     15.9     ~ 132 0
16 NAME Andromeda XIII G 00 51 51.0 +33 00 16     18.1     ~ 128 0
17 NAME Andromeda IX G 00 52 53.0 +43 11 45     16.3     ~ 176 1
18 NAME Pisces V G 00 59 29.8 +32 22 36     14.4     ~ 149 0
19 NAME Sculptor Dwarf Galaxy G 01 00 09.4 -33 42 32   9.79 8.6 8.81   ~ 1498 4
20 NAME Andromeda X G 01 06 33.70 +44 48 15.8     16.6     ~ 125 1
21 NAME Andromeda V G 01 10 17.1 +47 37 41     15.3     ~ 215 0
22 NAME Andromeda XV G 01 14 18.7 +38 07 03     14.6     ~ 123 0
23 NAME Andromeda II G 01 16 29.8 +33 25 09     11.7     ~ 402 0
24 NAME Andromeda XXIV G 01 18 30.0 +46 21 58     16.3     ~ 64 0
25 NAME Andromeda XXII G 01 27 40.0 +28 05 25     18.0     ~ 95 0
26 NAME Andromeda XXIII G 01 29 21.8 +38 43 08     14.2     ~ 88 0
27 NAME Segue 2 G 02 19 16.0 +20 10 31     15.2     ~ 299 0
28 MCG-06-07-001 G 02 39 59.3 -34 26 57   9.02 7.4     ~ 1894 1
29 ESO 206-20A G 06 41 36.7 -50 57 58   22.14 11.0 19.47   ~ 1190 0
30 NAME UMa II Galaxy G 08 51 30.0 +63 07 48     13.3     ~ 410 0
31 NAME Leo T G 09 34 53.4 +17 03 05     15.1     ~ 434 0
32 NAME Segue 1 G 10 07 03.2 +16 04 25     15.3     ~ 517 1
33 Z 64-73 G 10 08 28.12 +12 18 23.4   11.3 10.0     ~ 1284 1
34 NAME Sextans dSph LSB 10 13 02.9 -01 36 53   12 10.4     ~ 921 0
35 NAME UMa I Galaxy G 10 34 52.80 +51 55 12.0     14.4     ~ 355 1
36 Z 126-111 G 11 13 28.13 +22 09 10.1   12.9 12.0     ~ 899 0
37 NAME Leo V LSB 11 31 09.60 +02 13 12.0     16.0     ~ 234 0
38 NAME Leo IV LSB 11 32 57.0 -00 32 00     15.1     ~ 419 1
39 NAME Coma Dwarf Galaxy G 12 26 59.0 +23 54 15     14.1     ~ 482 1
40 NAME CVn II dSph G 12 57 09.6 +34 19 12     16.1     ~ 287 2
41 NAME CVn I dSph G 13 28 03.5 +33 33 21     13.1     ~ 352 1
42 NAME Bootes II G 13 58 00.0 +12 51 00     15.4     ~ 269 0
43 NAME Bootes Dwarf Spheroidal Galaxy G 14 00 00.0 +14 30 00     12.8     ~ 491 0
44 Z 318-18 G 15 09 08.0 +67 13 21   13.60 10.6     ~ 1459 0
45 NAME Hercules Dwarf Galaxy G 16 31 02.0 +12 47 30     14.0     ~ 379 1
46 Z 300-12 G 17 20 14.335 +57 55 16.39   12.40 10.6     ~ 1428 1
47 NAME Andromeda VII GiG 23 26 31.0 +50 40 33   13.6 11.8     ~ 222 1
48 NAME Peg dSph GiG 23 51 46.3 +24 34 57   14.5 13.2     ~ 250 2
49 NAME Andromeda XXI G 23 54 47.7 +42 28 15     14.8     ~ 117 0
50 NAME Local Group GrG ~ ~           ~ 9325 0

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