2015A&A...583A.114H


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.03CEST22:01:57

2015A&A...583A.114H - Astronomy and Astrophysics, volume 583A, 114-114 (2015/11-1)

Molecular depletion times and the CO-to-H2 conversion factor in metal-poor galaxies.

HUNT L.K., GARCIA-BURILLO S., CASASOLA V., CASELLI P., COMBES F., HENKEL C., LUNDGREN A., MAIOLINO R., MENTEN K.M., TESTI L. and WEISS A.

Abstract (from CDS):

Tracing molecular hydrogen content with carbon monoxide in low-metallicity galaxies has been exceedingly difficult. Here we present a new effort, with IRAM 30-m observations of 12CO(1-0) of a sample of 8 dwarf galaxies having oxygen abundances ranging from 12+log(O/H)∼7.7 to 8.4. CO emission is detected in all galaxies, including the most metal-poor galaxy of our sample (0.1Z); to our knowledge this is the largest number of 12CO(1-0) detections ever reported for galaxies with 12+log(O/H)≲8 (0.2Z) outside the Local Group. We calculate stellar masses, Mstar, and star-formation rates (SFRs), and analyze our results in conjunction with galaxy samples from the literature. Extending previous results for a correlation of the molecular gas depletion time, τdep, with Mstar and specific SFR (sSFR), we find a variation in τdep of a factor of 200 or more (from ≲50Myr to ∼10Gyr) over a spread of ∼103 in sSFR and Mstar. We exploit the variation of τdep to constrain the CO-to-H2 mass conversion factor αCO at low metallicity, and assuming a power-law variation find αCO ∝ Z/Z–2, similar to results based on dust continuum measurements compared with gas mass. By including H I measurements, we show that the fraction of total gas mass relative to the baryonic mass is higher in galaxies that are metal poor, of low mass, and with high sSFR. Finally, comparisons of the data with star-formation models of the molecular gas phases show that the models are generally quite successful, but at metallicities Z/Z≲0.2, there are some discrepancies.

Abstract Copyright:

Journal keyword(s): galaxies: dwarf - galaxies: starburst - galaxies: star formation - galaxies: ISM - ISM: general

Simbad objects: 20

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Number of rows : 20

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 4C 34.01 Rad 00 13 44.10 +34 41 40.0     18     ~ 23 1
2 QSO B0125-0635 QSO 01 27 35.5241670251 -06 19 35.428005150 14.75 15.05 14.48 14.06 13.70 ~ 89 0
3 4C 28.07 QSO 02 37 52.40567732 +28 48 08.9900231     18.5 16.99   ~ 499 1
4 NGC 1140 EmG 02 54 33.5258827369 -10 01 43.135585379 12.41 12.84 12.49 13.6 13.5 ~ 260 1
5 NGC 1156 rG 02 59 42.8526900556 +25 14 28.350265697 12.13 12.32 11.74     ~ 277 1
6 SBSG 0335-052B G 03 37 44.04 -05 02 40.2   16.77 16.65   16.79 ~ 148 1
7 NGC 1569 IG 04 30 49.186 +64 50 52.52 11.72 11.86 11.03     ~ 1147 3
8 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 14826 1
9 RMC 136 Cl* 05 38 42.396 -69 06 03.36           ~ 1734 1
10 UGCA 116 H2G 05 55 42.645 +03 23 32.23 10.74 11.68 11.46   11.82 ~ 500 0
11 NAME Zwicky's Flare HII 09 34 00.0 +55 14 25           ~ 21 0
12 Mrk 116 PaG 09 34 02.1 +55 14 25           ~ 996 1
13 MCG+00-25-010 Sy1 09 44 01.8782156203 -00 38 32.011388330   15.5       ~ 47 0
14 NGC 3353 AGN 10 45 22.390 +55 57 37.36 12.90 13.25 12.79     ~ 319 1
15 Mrk 1304 IG 11 42 12.253 +00 20 03.68   14.16 13.67 13.41 13.03 ~ 150 0
16 LEDA 37102 Sy1 11 51 33.3534243441 -02 22 21.893770899   17       ~ 143 0
17 Mrk 1307 Sy1 11 52 37.19 -02 28 09.9   14.79   14.09 14.9 ~ 157 0
18 NGC 5253 AGN 13 39 55.990 -31 38 24.11 11.48 10.94 10.49 10.33   ~ 1269 4
19 NGC 7077 G 21 29 59.634 +02 24 51.75 14.05 14.25 13.67 13.23 12.86 ~ 94 0
20 NAME Local Group GrG ~ ~           ~ 6970 0

    Equat.    Gal    SGal    Ecl

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2020.07.03-22:01:57

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