2008ApJ...686.1030O

Query : 2008ApJ...686.1030O

2008ApJ...686.1030O - Astrophys. J., 686, 1030-1044 (2008/October-3)

Delving deeper into the tumultuous lives of galactic dwarfs: modeling star formation histories.

ORBAN C., GNEDIN O.Y., WEISZ D.R., SKILLMAN E.D., DOLPHIN A.E. and HOLTZMAN J.A.

Abstract (from CDS):

The paucity of observed dwarf galaxies in the Local Group relative to the abundance of predicted dark matter halos remains one of the greatest puzzles of the ΛCDM paradigm. Solving this puzzle now requires not only matching the numbers of objects but also understanding the details of their star formation histories. We present a summary of such histories derived from the HST data using the color-magnitude diagram fitting method. To reduce observational uncertainties, we condense the data into five cumulative parameters: the fractions of stellar mass formed in the last 1, 2, 5, and 10 Gyr, and the mean stellar age. We interpret the new data with a phenomenological model based on the mass assembly histories of dark matter halos and the Schmidt law of star formation. The model correctly predicts the radial distribution of the dwarfs and the fractions of stars formed in the last 5 and 10 Gyr. However, in order to be consistent with the observations, the model requires a significant amount of recent star formation in the last 2 Gyr. Within the framework of our model, this prolonged star formation can be achieved by adding a stochastic variation in the density threshold of the star formation law. The model results are not sensitive to late gas accretion, the slope of the Schmidt law, or the details of cosmic reionization. A few discrepancies still remain: our model typically predicts too large stellar masses, only a modest population of ultrafaint dwarfs, and a small number of dwarfs with anomalously young stellar populations. Nevertheless, the observed star formation histories of Local Group dwarfs are generally consistent the expected star formation in cold dark matter halos.

Abstract Copyright: ∼

Journal keyword(s): Cosmology: Theory - Galaxies: Dwarf - Galaxies: Formation

Simbad objects: 61

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Number of rows : 61
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 MCG-03-01-015 G 00 01 57.9 -15 27 50   11.50 11.10 10.93   ~ 782 2
2 IC 10 rG 00 20 17.33520 +59 18 13.6480   13.6 9.5     ~ 1185 1
3 NAME Cetus Dwarf Galaxy G 00 26 10.8 -11 03 14     13.2     ~ 257 0
4 NGC 147 GiG 00 33 12.120 +48 30 31.46   12.0 9.5     ~ 720 1
5 NAME Andromeda III G 00 35 33.8 +36 29 52     14.4     ~ 309 0
6 NAME Andromeda XVII G 00 37 07.0 +44 19 20     15.8     ~ 101 0
7 NGC 185 Sy2 00 38 57.9400026024 +48 20 15.035874648   9.10 9.2     ~ 840 1
8 M 110 GiG 00 40 22.0572349992 +41 41 07.507220136   8.92 8.07     ~ 1370 1
9 M 32 GiG 00 42 41.82480 +40 51 54.6120 9.51 9.03 8.08     ~ 2236 2
10 M 31 AGN 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 13622 1
11 NAME Andromeda I G 00 45 39.8 +38 02 28   13.9 12.7     ~ 355 0
12 NAME Andromeda XI G 00 46 20.0 +33 48 05     17.5     ~ 130 0
13 NAME Andromeda XII G 00 47 27.0 +34 22 29     18.3     ~ 124 0
14 NAME Andromeda XIV G 00 51 35.0 +29 41 49     15.9     ~ 132 0
15 NAME Andromeda XIII G 00 51 51.0 +33 00 16     18.1     ~ 128 0
16 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 12317 1
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 Pisces I G 01 03 55.0 +21 53 06   16.18 14.3     ~ 404 0
21 IC 1613 GiC 01 04 48.4071 +02 07 10.185   10.42 10.01 9.77   ~ 1316 2
22 NAME Andromeda X G 01 06 33.70 +44 48 15.8     16.6     ~ 125 1
23 NAME Andromeda V G 01 10 17.1 +47 37 41     15.3     ~ 215 0
24 NAME Andromeda XV G 01 14 18.7 +38 07 03     14.6     ~ 123 0
25 NAME Andromeda II G 01 16 29.8 +33 25 09     11.7     ~ 402 0
26 M 33 GiG 01 33 50.8965749232 +30 39 36.630403128 6.17 6.27 5.72     ~ 6226 1
27 NAME Phoenix Dwarf Galaxy Sy1 01 51 06.3 -44 26 41   13.48 13.2 12.69   ~ 575 2
28 UGCA 92 AG? 04 32 03.8366 +63 36 51.243   16.15       ~ 128 0
29 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 19090 0
30 ESO 206-20A G 06 41 36.7 -50 57 58   22.14 11.0 19.47   ~ 1190 0
31 Z 264-88 AG? 09 16 02.0195908968 +52 50 42.051257412   14.0 13.2     ~ 141 0
32 NAME Leo T G 09 34 53.4 +17 03 05     15.1     ~ 434 0
33 Z 153-10 G 09 59 26.46 +30 44 47.0 14.08 13.54 13.26 13.33   ~ 652 0
34 NAME SDSS J1000+5730 Dwarf G G 10 00.0 +57 30           ~ 4 0
35 Z 36-12 H2G 10 00 00.8217342072 +05 20 09.533389560 12.77 12.25 11.89 11.71   ~ 569 0
36 NGC 3109 AG? 10 03 06.877 -26 09 34.46 11.10 10.42 10.04 9.91   ~ 825 2
37 NAME Antlia Dwarf Galaxy G 10 04 03.9 -27 20 01 16.73 15.69 15.17 15.00   ~ 221 1
38 Z 64-73 G 10 08 28.12 +12 18 23.4   11.3 10.0     ~ 1284 1
39 MCG-01-26-030 H2G 10 11 00.5 -04 41 30 12.48 12.13 11.93 11.78   ~ 789 2
40 NAME Sextans dSph LSB 10 13 02.9 -01 36 53   12 10.4     ~ 921 0
41 NAME UMa I Galaxy G 10 34 52.80 +51 55 12.0     14.4     ~ 355 1
42 NAME Willman 1 G 10 49 21.0 +51 03 00     15.2     ~ 345 0
43 Z 126-111 G 11 13 28.13 +22 09 10.1   12.9 12.0     ~ 899 0
44 NAME Leo IV LSB 11 32 57.0 -00 32 00     15.1     ~ 419 1
45 NAME Coma Dwarf Galaxy G 12 26 59.0 +23 54 15     14.1     ~ 482 1
46 NAME CVn I dSph G 13 28 03.5 +33 33 21     13.1     ~ 352 1
47 NAME SDSS J1329+2841 Dwarf G G 13 29 13.0 +28 41 27           ~ 4 0
48 NAME Bootes II G 13 58 00.0 +12 51 00     15.4     ~ 269 0
49 NAME Bootes Dwarf Spheroidal Galaxy G 14 00 00.0 +14 30 00     12.8     ~ 491 0
50 Z 318-18 G 15 09 08.0 +67 13 21   13.60 10.6     ~ 1459 0
51 NAME Hercules Dwarf Galaxy G 16 31 02.0 +12 47 30     14.0     ~ 379 1
52 Z 300-12 G 17 20 14.335 +57 55 16.39   12.40 10.6     ~ 1428 1
53 NAME Sgr dIG G 19 29 59.0 -17 40 41   15.5 13.6     ~ 323 1
54 NGC 6822 G 19 44 56.199 -14 47 51.29   18 8.1     ~ 1661 0
55 MCG-02-53-003 G 20 46 51.7 -12 50 54 15.75 15.18 14.83 14.46   ~ 470 1
56 NAME Tuc Galaxy G 22 41 49.6 -64 25 10   15.7 15.2     ~ 324 0
57 NAME Andromeda VII GiG 23 26 31.0 +50 40 33   13.6 11.8     ~ 222 1
58 Z 431-72 G 23 28 35.2 +14 44 35 13.85 13.16 12.52     ~ 499 1
59 NAME Peg dSph GiG 23 51 46.3 +24 34 57   14.5 13.2     ~ 250 2
60 NAME Local Group GrG ~ ~           ~ 9325 0
61 NAME Monoceros Stream St* ~ ~           ~ 374 1

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