2012AJ....143...47Z

Query : 2012AJ....143...47Z

2012AJ....143...47Z - Astron. J., 143, 47 (2012/February-0)

Outside-in shrinking of the star-forming disk of dwarf irregular galaxies.

ZHANG H.-X., HUNTER D.A., ELMEGREEN B.G., GAO Y. and SCHRUBA A.

Abstract (from CDS):

We have studied multi-band surface brightness profiles of a representative sample of 34 nearby dwarf irregular galaxies. Our data include Galaxy Evolution Explorer (GALEX) FUV/NUV, UBV, and Hα and Spitzer 3.6 µm images. These galaxies constitute the majority of the LITTLE THINGS survey (Local Irregulars That Trace Luminosity Extremes–The H I Nearby Galaxy Survey). By modeling the azimuthal averages of the spectral energy distributions with a complete library of star formation histories, we derived the stellar mass surface density distributions and the star formation rate averaged over three different timescales: the recent 0.1 Gyr, 1 Gyr, and a Hubble time. We find that, for ∼80% (27 galaxies) of our sample galaxies, radial profiles (at least in the outer part) at shorter wavelengths, corresponding to younger stellar populations, have shorter disk scale lengths than those at longer wavelengths, corresponding to older stellar populations. This indicates that the star-forming disk has been shrinking. In addition, the radial distributions of the stellar mass surface density are well described as piece-wise exponential profiles, and ∼80% of the galaxies have steeper mass profiles in the outer disk than in the inner region. The steep radial decline of the star formation rate in the outer parts compared to that in the inner disks gives a natural explanation for the down-bending stellar mass surface density profiles. Within the inner disks, our sample galaxies on average have constant ratios of recent star formation rate to stellar mass with radius. Nevertheless, ∼35% (12 galaxies, among which 7 have baryonic mass ≲ 108 M☉) of the sample exhibit negative slopes across the observed disk, which is in contrast with the so-called inside-out disk growth scenario suggested for luminous spiral galaxies. The tendency of star formation to become concentrated toward the inner disks in low-mass dwarf irregular galaxies is interpreted as a result of their susceptibility to environmental effects and regulation through stellar feedback.

Abstract Copyright: ∼

Journal keyword(s): galaxies: dwarf - galaxies: evolution - galaxies: irregular - galaxies: stellar content

CDS comments: In Table 1, IIZw 499 is a misprint for VIIZw 499.

Simbad objects: 47

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Number of rows : 47
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 NGC 300 GiG 00 54 53.4465638304 -37 41 03.168402396 8.83 8.69 8.13 7.46   ~ 1614 2
3 NAME Sculptor Dwarf Galaxy G 01 00 09.4 -33 42 32   9.79 8.6 8.81   ~ 1498 4
4 NAME Pisces I G 01 03 55.0 +21 53 06   16.18 14.3     ~ 404 0
5 IC 1613 GiC 01 04 48.4071 +02 07 10.185   10.42 10.01 9.77   ~ 1316 2
6 M 33 GiG 01 33 50.8965749232 +30 39 36.630403128 6.17 6.27 5.72     ~ 6226 1
7 NAME Phoenix Dwarf Galaxy Sy1 01 51 06.3 -44 26 41   13.48 13.2 12.69   ~ 575 2
8 MCG-06-07-001 G 02 39 59.3 -34 26 57   9.02 7.4     ~ 1894 1
9 NGC 1156 GiG 02 59 42.8528847264 +25 14 28.352017320 12.13 12.32 11.74     ~ 323 1
10 ACO S 373 ClG 03 38 29.4 -35 27 08           ~ 2029 0
11 NGC 1569 rG 04 30 49.186 +64 50 52.52 11.72 11.86 11.03     ~ 1297 3
12 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 19090 0
13 NGC 2363 AG? 07 28 29.59 +69 11 34.3   15.5       ~ 262 1
14 NGC 2366 H2G 07 28 52.4529 +69 12 38.859 12.25 11.86 11.39 11.33   ~ 801 0
15 UGC 4305 IG 08 19 04.9864630512 +70 43 13.086910452 12.06 11.72 11.39 11.11   ~ 812 2
16 NAME M 81 Dwarf A G 08 23 55.1 +71 01 56   16.5       ~ 209 1
17 MCG+07-18-004 LSB 08 28 28.560 +41 51 27.13   18       ~ 175 0
18 Z 311-8 GiG 08 34 07.20 +66 10 54.0 15.39 15.03 14.70 14.49   ~ 357 2
19 Z 332-57 LSB 09 40 32.33 +71 10 56.0 14.53 14.00 13.66 13.41   ~ 372 1
20 NGC 2976 GiG 09 47 15.458 +67 54 58.97 11.77 11.03 10.16 9.51   ~ 712 1
21 NAME M 81-82 Group GrG 09 55 +69.1           ~ 758 0
22 Z 153-10 G 09 59 26.46 +30 44 47.0 14.08 13.54 13.26 13.33   ~ 652 0
23 Z 36-12 H2G 10 00 00.8217342072 +05 20 09.533389560 12.77 12.25 11.89 11.71   ~ 569 0
24 MCG-01-26-030 H2G 10 11 00.5 -04 41 30 12.48 12.13 11.93 11.78   ~ 789 2
25 MCG+11-13-039 GiG 10 49 36.412 +65 32 01.07 15.55 15.27 14.79 14.55   ~ 170 0
26 Z 351-62 bCG 11 27 59.90 +78 59 39.0   14.50       ~ 346 1
27 Z 242-46 bCG 11 33 29.12 +49 14 17.4 14.69 14.61 14.25 14.17   ~ 242 1
28 NGC 3738 AGN 11 35 48.982 +54 31 24.70   12.12 12.04 11.56   ~ 303 0
29 Z 157-55 AG? 11 55 39.7060218792 +31 31 06.535928784   15.7       ~ 138 0
30 NGC 4163 LSB 12 12 09.34 +36 10 08.1 14.33 13.70 13.2 12.98   ~ 238 0
31 NGC 4228 SBG 12 15 39.174 +36 19 36.80 10.63 10.30 9.93 9.74   ~ 1017 1
32 Z 244-18 bCG 12 26 15.69 +48 29 38.3   15.3       ~ 364 0
33 Z 187-44 GiP 12 27 05.566 +37 08 30.39   14.19   13.55   ~ 217 0
34 NAME Virgo Cluster ClG 12 30 47.8 +12 23 07           ~ 7107 0
35 Z 159-13 GiC 12 32 54.5 +31 32 30   13.50   13.03   ~ 180 0
36 NAME CVn I dwA GiC 12 38 40.06 +32 46 00.5 16.91 16.66 16.73 16.62   ~ 242 0
37 NGC 4789A GiC 12 54 05.248 +27 08 58.67 14.37 14.23 13.95 13.84   ~ 614 1
38 Z 71-87 H2G 12 58 40.1930636208 +14 13 00.739589628 15.24 15.16 14.98 14.81   ~ 475 0
39 Z 316-9 AG? 13 06 24.85 +67 42 25.0 14.08 13.61 13.08 12.98   ~ 268 1
40 Z 245-36 AG? 13 14 27.997 +45 55 11.14 13.63 13.26 13.02 12.81   ~ 297 0
41 Z 271-48 EmG 13 30 44.8682655624 +54 54 38.522749824 14.72 14.25 13.90 13.75   ~ 218 0
42 Z 133-19 AG? 14 15 57.0834 +23 03 29.871 15.40 14.77 14.41 14.32   ~ 296 0
43 NAME Ursa Major Cluster ClG 15 08.8 +67 07           ~ 424 1
44 NGC 6822 G 19 44 56.199 -14 47 51.29   18 8.1     ~ 1661 0
45 MCG-02-53-003 G 20 46 51.7 -12 50 54 15.75 15.18 14.83 14.46   ~ 470 1
46 Z 431-72 G 23 28 35.2 +14 44 35 13.85 13.16 12.52     ~ 499 1
47 NAME Peg dSph GiG 23 51 46.3 +24 34 57   14.5 13.2     ~ 250 2

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