1999ApJ...519...55Y


C.D.S. - SIMBAD4 rel 1.7 - 2020.05.25CEST02:02:05

1999ApJ...519...55Y - Astrophys. J., 519, 55-68 (1999/July-1)

The luminosity functions and size distributions of H II regions in irregular galaxies.

YOUNGBLOOD A.J. and HUNTER D.A.

Abstract (from CDS):

CCD Hα images were used to study the properties of H II regions in 29 normal Im galaxies and six blue compact dwarf/starburst irregulars. The Hα emission line fluxes were measured and used to construct luminosity functions for each galaxy. For most galaxies, the luminosity function is well represented by a power law. Only two of the 29 Im galaxies have supergiant H II regions, which is probably a result of the small size and small total numbers of H II regions in irregular galaxies. BCDs and starburst galaxies, on the other hand, do not always have supergiant H II regions but may have them even if only a few regions are present. Comparison of the cumulative composite H II luminosity function with that of spiral galaxies shows that the irregulars in our sample do not have an unusually large population of supergiant H II regions relative to the galactic luminosity. Thus, these galaxies will not suffer a disproportionate amount of disruption by the concentration of massive stars within such regions. However, in BCD/starburst galaxies there is an excess of H II regions with luminosities greater than 1038 ergs.s–1 compared to Im and Sc galaxies relative to the luminosities of the host galaxies. Most of the H II region luminosity in normal Im galaxies comes from small regions and that in BCD/starburst galaxies from moderately large regions. Over 80% of the H II region luminosity in irregulars is found in complexes of H II regions typically with summed luminosities equivalent to ≤10 Orion nebulae. Two types of luminosity functions were observed: those that exhibit turnover and those that do not. Those that do exhibit turnover have an average slope of -1.5±0.1, and those that do not exhibit turnover tend to be complete to fainter levels, have lower upper luminosity cutoffs, have fewer H II regions, and have shallower slopes of -1.0±0.1. If the luminosity function is universal for a galaxy type, this difference suggests the possibility of a break in the luminosity function corresponding to H II regions ionized by single stars and H II regions ionized by clusters of stars. However, we cannot exclude the possibility that the two groups of galaxies are different in terms of their global star formation properties. Diameters of H II regions were also measured and diameter distributions were constructed for each of the galaxies. The diameter distribution was fitted with an exponential and the characteristic diameter D0 was measured for each galaxy, although this fit did not characterize the distribution very well in most galaxies. The weak correlation between D0 and the absolute blue magnitude of the galaxy suggested by others is confirmed to be very weak.

Abstract Copyright:

Journal keyword(s): Galaxies: Irregular - Galaxies: ISM - Galaxies: Starburst - ISM: H II Regions

Status at CDS:  

Simbad objects: 39

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Number of rows : 39

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 WLM Galaxy G 00 01 57.9 -15 27 50   11.50 11.10 10.93   ~ 567 2
2 IC 10 G 00 20 23.16 +59 17 34.7   13.6 9.5     ~ 1004 0
3 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 9377 1
4 NGC 1156 rG 02 59 42.8526900556 +25 14 28.350265697 12.13 12.32 11.74     ~ 275 1
5 NGC 1569 IG 04 30 49.186 +64 50 52.52 11.72 11.86 11.03     ~ 1145 3
6 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 14734 1
7 UGC 3860 G 07 28 17.724 +40 46 11.36   15.50       ~ 131 0
8 NGC 2363A HII 07 28 42.8 +69 11 21           ~ 540 3
9 NGC 2366 H2G 07 28 51.85 +69 12 31.1 12.25 11.86 11.39 11.33   ~ 698 0
10 UGC 3966 G 07 41 25.777 +40 06 46.05   16.0       ~ 99 0
11 UGC 3974 G 07 41 56.3061361330 +16 48 07.439323443   15.4       ~ 199 0
12 UGC 4305 IG 08 19 04.9878269182 +70 43 13.025604473 12.06 11.72 11.39 11.11   ~ 684 2
13 UGC 4459 GiG 08 34 07.29 +66 10 54.6 15.39 15.03 14.70 14.49   ~ 290 2
14 NAME Leo Dwarf Irregular Galaxy G 09 59 26.46 +30 44 47.0 14.08 13.54 13.26 13.33   ~ 545 0
15 NAME Sextans B H2G 10 00 00.8201300945 +05 20 09.572530884 12.77 12.25 11.89 11.71   ~ 464 0
16 NAME Sex A H2G 10 11 00.5 -04 41 30 12.48 12.13 11.93 11.78   ~ 649 2
17 UGC 5918 GiG 10 49 36.412 +65 32 01.07 15.55 15.27 14.79 14.55   ~ 122 0
18 UGC 6456 bCG 11 28 00.43 +78 59 38.4   14.50       ~ 305 1
19 Mrk 178 bCG 11 33 29.12 +49 14 17.4 14.69 14.61 14.25 14.17   ~ 211 1
20 NGC 3738 AGN 11 35 48.982 +54 31 24.70   12.12 12.04 11.56   ~ 246 0
21 UGC 6900 G 11 55 39.7065939676 +31 31 06.530347793   15.7       ~ 94 0
22 IC 3059 GiP 12 14 55.197 +13 27 41.01 14.78 14.70 14.19     ~ 83 1
23 NGC 4228 SBG 12 15 39.174 +36 19 36.80 10.63 10.30 9.93 9.74   ~ 861 1
24 Mrk 209 bCG 12 26 16.02 +48 29 36.6   15.3       ~ 299 0
25 UGC 7559 GiP 12 27 05.566 +37 08 30.39   14.19   13.55   ~ 165 0
26 UGC 7577 GiG 12 27 41.8803124881 +43 29 58.140216428 13.75 13.10 12.7 12.33   ~ 224 0
27 NGC 4449 EmG 12 28 11.118 +44 05 36.81 10.11 9.98 9.64 9.45   ~ 1019 1
28 UGC 7698 GiC 12 32 53.771 +31 32 50.56   13.50   13.03   ~ 132 0
29 UGC 8024 GiC 12 54 05.248 +27 08 58.67 14.37 14.23 13.95 13.84   ~ 528 1
30 UGC 8091 H2G 12 58 40.1930291852 +14 13 00.737117016 15.24 15.16 14.98 14.81   ~ 437 0
31 UGC 8201 G 13 06 24.85 +67 42 25.0 14.08 13.61 13.08 12.98   ~ 222 1
32 UGC 8308 G 13 13 22.839 +46 19 21.71   17       ~ 116 1
33 UGC 8320 G 13 14 27.997 +45 55 11.14 13.63 13.26 13.02 12.81   ~ 232 0
34 UGC 8331 G 13 15 29.753 +47 29 58.69   15.6       ~ 91 1
35 UGC 8508 G 13 30 44.8713405615 +54 54 38.531712530 14.72 14.25 13.90 13.75   ~ 161 0
36 UGC 8760 G 13 50 51.3121098935 +38 01 14.956142286 15.56 14.78   14.33   ~ 129 0
37 UGC 8837 G 13 54 45.602 +53 54 20.06   14.2       ~ 178 0
38 UGC 9128 G 14 15 56.70 +23 03 16.2 15.40 14.77 14.41 14.32   ~ 254 0
39 NAME Peg Dwarf Irregular Galaxy G 23 28 35.2 +14 44 35 13.85 13.16 12.52     ~ 417 1

    Equat.    Gal    SGal    Ecl

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2020.05.25-02:02:05

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