2012AJ....143..138S


C.D.S. - SIMBAD4 rel 1.7 - 2019.12.14CET15:37:23

2012AJ....143..138S - Astron. J., 143, 138 (2012/June-0)

Low CO luminosities in dwarf galaxies.

SCHRUBA A., LEROY A.K., WALTER F., BIGIEL F., BRINKS E., DE BLOK W.J.G., KRAMER C., ROSOLOWSKY E., SANDSTROM K., SCHUSTER K., USERO A., WEISS A. and WIESEMEYER H.

Abstract (from CDS):

We present maps of 12COJ = 2-1 emission covering the entire star-forming disks of 16 nearby dwarf galaxies observed by the IRAM HERACLES survey. The data have 13'' angular resolution, ∼250 pc at our average distance of D = 4 Mpc, and sample the galaxies by 10-1000 resolution elements. We apply stacking techniques to perform the first sensitive search for CO emission in dwarf galaxies outside the Local Group ranging from individual lines of sight, stacking over IR-bright regions of embedded star formation, and stacking over the entire galaxy. We detect five galaxies in CO with total CO luminosities of L_ CO 2-1_= (3-28)x106 K.km/s.pc2. The other 11 galaxies remain undetected in CO even in the stacked images and have L_ CO 2-1_ ≲ (0.4-8) x106 K.km/s.pc2. We combine our sample of dwarf galaxies with a large sample of spiral galaxies from the literature to study scaling relations of LCO with MBand metallicity. We find that dwarf galaxies with metallicities of Z ~ 1/2-1/10 Z have LCOof 2-4 orders of magnitude smaller than massive spiral galaxies and that their LCO per unit LB is 1-2 orders of magnitude smaller. A comparison with tracers of star formation (FUV and 24 µm) shows that LCO per unit star formation rate (SFR) is 1-2 orders of magnitude smaller in dwarf galaxies. One possible interpretation is that dwarf galaxies form stars much more efficiently: we argue that the low LCO/SFR ratio is due to the fact that the CO-to-H2 conversion factor, αCO, changes significantly in low-metallicity environments. Assuming that a constant H2 depletion time of τdep= 1.8 Gyr holds in dwarf galaxies (as found for a large sample of nearby spirals) implies αCO values for dwarf galaxies with Z ~ 1/2-1/10 Z that are more than one order of magnitude higher than those found in solar metallicity spiral galaxies. Such a significant increase of αCO at low metallicity is consistent with previous studies, in particular those of Local Group dwarf galaxies that model dust emission to constrain H2masses. Even though it is difficult to parameterize the dependence of αCO on metallicity given the currently available data, the results suggest that CO is increasingly difficult to detect at lower metallicities. This has direct consequences for the detectability of star-forming galaxies at high redshift, which presumably have on average sub-solar metallicity.

Abstract Copyright:

Journal keyword(s): galaxies: ISM - ISM: molecules - radio lines: galaxies

Simbad objects: 78

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Number of rows : 78

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 IC 10 G 00 20 23.16 +59 17 34.7   13.6 9.5     ~ 984 0
2 [LBW2006] B11a MoC 00 20 27.20 +59 16 53.8           ~ 3 0
3 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 10616 1
4 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 9141 1
5 LHA 115-N 84 HII 01 14 27.7 -73 12 51           ~ 60 0
6 M 33 GiG 01 33 50.904 +30 39 35.79 6.17 6.27 5.72     ~ 5038 1
7 [EPR2003] 1 MoC 01 34 09.3 +30 49 06           ~ 13 0
8 M 74 G 01 36 41.772 +15 47 00.46 10.52 10.00 9.46 9.16   ~ 1345 1
9 NGC 925 H2G 02 27 16.913 +33 34 43.97   10.69 10.12 9.55   ~ 681 1
10 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 5410 1
11 NGC 1482 GiP 03 54 38.928 -20 30 08.82 13.15 13.14 12.15 11.29   ~ 247 2
12 NGC 1569 IG 04 30 49.186 +64 50 52.52 11.72 11.86 11.03     ~ 1139 3
13 NAME Taurus Dark Cloud SFR 04 41.0 +25 52           ~ 3338 0
14 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 14392 1
15 NAME Ori A MoC 05 38 -07.1           ~ 2620 0
16 [FKM2008] LMC N J0540-7008 MoC 05 40 07.2 -70 08 20           ~ 9 0
17 UGCA 116 H2G 05 55 42.645 +03 23 32.23 10.74 11.68 11.46   11.82 ~ 492 0
18 NGC 2146 SBG 06 18 37.710 +78 21 25.27 11.67 11.38 10.59     ~ 606 2
19 NGC 2366 H2G 07 28 51.85 +69 12 31.1 12.25 11.86 11.39 11.33   ~ 687 0
20 NGC 2403 AGN 07 36 51.396 +65 36 09.17 9.31 8.84 8.38 8.19   ~ 1575 1
21 NGC 2537 IG 08 13 14.643 +45 59 23.25 12.18 12.50 11.69 11.66   ~ 264 1
22 UGC 4305 IG 08 19 04.9878269182 +70 43 13.025604473 12.06 11.72 11.39 11.11   ~ 673 2
23 NAME M 81 Dwarf A G 08 23 55.1 +71 01 56   16.5       ~ 184 1
24 UGC 4459 GiG 08 34 07.29 +66 10 54.6 15.39 15.03 14.70 14.49   ~ 285 2
25 NGC 2782 Sy2 09 14 05.120 +40 06 49.68 12.29 12.30 11.63     ~ 429 3
26 NGC 2798 GiP 09 17 22.954 +41 59 58.96 13.03 13.04 12.32     ~ 284 3
27 NGC 2841 LIN 09 22 02.655 +50 58 35.32 10.43 10.09 9.22     ~ 967 1
28 NGC 2905 H2G 09 32 10.111 +21 30 02.99 10.44 9.75 9.07 8.68   ~ 969 3
29 Mrk 116 PaG 09 34 02.1 +55 14 25           ~ 978 1
30 UGC 5139 LSB 09 40 32.33 +71 10 56.0 14.53 14.00 13.66 13.41   ~ 311 1
31 NGC 2976 GiP 09 47 15.458 +67 54 58.97 11.77 11.03 10.16 9.51   ~ 569 1
32 M 81 Sy2 09 55 33.17306143 +69 03 55.0609270   7.89 6.94     ~ 3901 5
33 M 82 IG 09 55 52.430 +69 40 46.93 9.61 9.30 8.41     ~ 5239 6
34 NGC 3079 Sy2 10 01 57.80342 +55 40 47.2428 11.57 11.54 10.86     ~ 1221 3
35 NGC 3077 GiP 10 03 19.0965510921 +68 44 01.556166166 11.23 10.85 10.14 9.74   ~ 672 0
36 NAME M81 dwB G 10 05 30.44 +70 21 53.9 15.95 15.56 15.09 14.87   ~ 173 1
37 NGC 3180 GiG 10 18 16.985 +41 25 27.77   10.4       ~ 611 0
38 NGC 3198 EmG 10 19 54.990 +45 32 58.88 10.83 10.87 10.33     ~ 800 1
39 IC 2574 G 10 28 23.6204574649 +68 24 43.441365350 11.70 11.07 10.87 10.74   ~ 592 1
40 NGC 3310 AGN 10 38 45.857 +53 30 11.89   12.45 12.15     ~ 721 1
41 M 95 GiP 10 43 57.733 +11 42 13.00 10.71 10.51 9.73 9.48   ~ 909 2
42 M 96 GiP 10 46 45.744 +11 49 11.78 10.42 10.15 9.25 8.99   ~ 728 1
43 NGC 3521 LSB 11 05 48.5676206040 -00 02 09.228156576 10.06 9.83 9.02 10.1 9.6 ~ 676 2
44 M 66 GiP 11 20 15.026 +12 59 28.64 9.85 9.65 8.92     ~ 1124 4
45 NGC 3628 GiP 11 20 17.018 +13 35 22.16   10.42 9.48 9.22   ~ 736 3
46 NGC 3938 GiG 11 52 49.453 +44 07 14.63 10.80 10.90 10.38     ~ 455 1
47 NGC 4194 AGN 12 14 09.615 +54 31 35.93   13.79 13.30     ~ 405 2
48 NGC 4228 SBG 12 15 39.174 +36 19 36.80 10.63 10.30 9.93 9.74   ~ 847 1
49 NGC 4236 GiG 12 16 42.118 +69 27 45.25 10.97 10.58 10.08 9.90   ~ 358 1
50 M 99 H2G 12 18 49.625 +14 24 59.36 10.45 10.44 9.87     ~ 740 2
51 M 100 AGN 12 22 54.9318850854 +15 49 20.294302163 10.04 10.05 9.35     ~ 1620 2
52 NGC 4449 EmG 12 28 11.118 +44 05 36.81 10.11 9.98 9.64 9.45   ~ 994 1
53 NGC 4450 LIN 12 28 29.634 +17 05 05.82   10.90 10.08     ~ 502 1
54 NGC 4536 GiP 12 34 27.129 +02 11 16.37 11.14 11.16 10.55 17.393   ~ 733 3
55 M 90 Sy2 12 36 49.816 +13 09 46.33 10.56 10.26 9.54     ~ 777 1
56 M 58 SyG 12 37 43.597 +11 49 05.12 10.80 10.48 9.66     ~ 956 2
57 NGC 4625 GiP 12 41 52.701 +41 16 25.39 12.74 12.92 12.35     ~ 301 2
58 NGC 4631 GiP 12 42 08.009 +32 32 29.44   9.78 9.19 9.10   ~ 944 2
59 NGC 4626 GiP 12 42 25.543 -07 02 36.47   14   13.38   ~ 29 0
60 NGC 4725 Sy2 12 50 26.5692916552 +25 30 02.737610391   13.45 12.44     ~ 608 2
61 M 94 SyG 12 50 53.148 +41 07 12.55 9.15 8.96 8.24 7.78   ~ 1184 3
62 UGC 8024 GiC 12 54 05.248 +27 08 58.67 14.37 14.23 13.95 13.84   ~ 522 1
63 M 64 SyG 12 56 43.696 +21 40 57.57   9.36 8.52     ~ 791 2
64 UGC 8201 G 13 06 24.85 +67 42 25.0 14.08 13.61 13.08 12.98   ~ 217 1
65 NGC 5033 Sy1 13 13 27.535 +36 35 37.14   11.01 12.03 9.73   ~ 784 3
66 M 63 LIN 13 15 49.2738527699 +42 01 45.726078017   9.34 8.59 8.35   ~ 1026 2
67 M 51 GiP 13 29 52.698 +47 11 42.93   9.26 8.36 8.40   ~ 3697 4
68 M 83 SBG 13 37 00.919 -29 51 56.74 8.85 8.11 7.52 7.21   ~ 2171 2
69 NGC 5253 AGN 13 39 55.990 -31 38 24.11 11.48 10.94 10.49 10.33   ~ 1247 4
70 NGC 5474 GiP 14 05 01.608 +53 39 43.95   11.28 10.79     ~ 371 1
71 NGC 5713 GiP 14 40 11.528 -00 17 21.16 11.88 11.84 11.20     ~ 338 2
72 M 102 SyG 15 06 29.561 +55 45 47.91 11.12 10.74 9.89     ~ 488 3
73 NGC 5953 GiP 15 34 32.402 +15 11 37.80   13.23 12.45     ~ 331 1
74 NGC 6822 G 19 44 56.199 -14 47 51.29   18 8.1     ~ 1408 0
75 NGC 6946 H2G 20 34 52.332 +60 09 13.24   10.5       ~ 2190 2
76 NGC 7331 LIN 22 37 04.102 +34 24 57.31 10.65 10.35 9.48     ~ 1086 2
77 NAME Local Group GrG ~ ~           ~ 6701 0
78 NAME Ori Mon Complex Cld ~ ~           ~ 18 0

    Equat.    Gal    SGal    Ecl

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2019.12.14-15:37:23

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