2004ApJ...606..271G


C.D.S. - SIMBAD4 rel 1.7 - 2019.12.10CET08:35:05

2004ApJ...606..271G - Astrophys. J., 606, 271-290 (2004/May-1)

The star formation rate and dense molecular gas in galaxies.

GAO Y. and SOLOMON P.M.

Abstract (from CDS):

HCN luminosity is a tracer of dense molecular gas, n(H2)≳3x104/cm3, associated with star-forming giant molecular cloud (GMC) cores. We present the results and analysis of our survey of HCN emission from 65 infrared galaxies, including nine ultraluminous infrared galaxies (ULIGs, LIR≳1012L), 22 luminous infrared galaxies (LIGs, 1011L<LIR≲1012L), and 34 normal spiral galaxies with lower IR luminosity (most are large spiral galaxies). We have measured the global HCN line luminosity, and the observations are reported in Paper I. This paper analyzes the relationships between the total far-IR luminosity (a tracer of the star formation rate), the global HCN line luminosity (a measure of the total dense molecular gas content), and the CO luminosity (a measure of the total molecular content). We find a tight linear correlation between the IR and HCN luminosities LIRand LHCN(in the log-log plot) with a correlation coefficient R=0.94, and an almost constant average ratio LIR/LHCN=900L(Kkm/s/pc2)–1. The IR-HCN linear correlation is valid over 3 orders of magnitude including ULIGs, the most luminous objects in the local universe. The direct consequence of the linear IR-HCN correlation is that the star formation law in terms of dense molecular gas content has a power-law index of 1.0. The global star formation rate is linearly proportional to the mass of dense molecular gas in normal spiral galaxies, LIGs, and ULIGs. This is strong evidence in favor of star formation as the power source in ultraluminous galaxies since the star formation in these galaxies appears to be normal and expected given their high mass of dense star-forming molecular gas.

The HCN-CO correlation is also much tighter than the IR-CO correlation. We suggest that the nonlinear correlation between LIRand LCOmay be a consequence of the stronger and perhaps more physical correlations between LIRand LHCNand between LHCNand LCO. Thus, the star formation rate indicated by LIR depends on the amount of dense molecular gas traced by HCN emission, not the total molecular gas traced by CO emission. One of the main arguments in favor of an active galactic nucleus (AGN) as the power source in ULIGs is the anomalously high ratio LIR/LCOor LIR/M(H2) or high star formation rate per Mof gas, compared with that from normal spiral galaxies. This has been interpreted as indicating that a dust-enshrouded AGN is required to produce the very high luminosity. Viewed in terms of the dense gas mass the situation is completely different. The ratio LIR/LHCNor LIR/Mdense, a measure of the star formation rate per solar mass of dense gas, is essentially the same in all galaxies including ULIGs. The ratio LIR/Mdenseis virtually independent of galaxy luminosity and on average LIR/Mdense~90L/M, about the same as in GMC cores but much higher than in GMCs. We find that ULIGs simply have a large quantity of dense molecular gas and thus produce a prodigious starburst that heats the dust, produces the IR, and blocks all or most optical radiation. The HCN global luminosity may be used as an indicator of the star formation rate in high-redshift objects including hyperluminous galaxies.

The HCN/CO ratio is an indicator of the dense molecular gas fraction and gauges the globally averaged molecular gas density. We find that the HCN/CO ratio is a powerful starburst indicator. All galaxies in our sample with a high dense gas mass fraction indicated by LHCN/LCO>0.06 are LIGs or ULIGs. Normal spirals all have similar and low dense gas fractions LHCN/LCO=0.02-0.05. The global star formation efficiency depends on the fraction of the molecular gas in a dense phase.


Abstract Copyright:

Journal keyword(s): Galaxies: ISM - Galaxies: Starburst - Infrared: Galaxies - ISM: Molecules - Radio Lines: Galaxies

Simbad objects: 75

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Number of rows : 75

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 NGC 253 SyG 00 47 33.134 -25 17 19.68   8.03   6.94 8.1 ~ 2868 2
2 IC 1623 IG 01 07 47.2 -17 30 25   15       ~ 254 1
3 NGC 520 IG 01 24 35.071 +03 47 32.68 12.41 12.24 11.42     ~ 480 3
4 NGC 660 LIN 01 43 02.350 +13 38 44.45   12.02 11.16     ~ 501 2
5 NGC 695 G 01 51 14.3476899804 +22 34 55.956806358   13.7       ~ 166 1
6 NGC 828 rG 02 10 09.5458704337 +39 11 25.220114583   13.0       ~ 149 1
7 IC 214 G 02 14 05.586 +05 10 23.37   14.4       ~ 136 0
8 NGC 891 H2G 02 22 32.907 +42 20 53.95 11.08 10.81 9.93 7.86   ~ 1493 2
9 NGC 1022 GiG 02 38 32.703 -06 40 38.60 12.33 12.09 11.34     ~ 183 1
10 NGC 1055 GiP 02 41 45.233 +00 26 35.45 11.59 11.40 10.59 10.5 10.7 ~ 253 2
11 M 77 GiP 02 42 40.771 -00 00 47.84 9.70 9.61 8.87 10.1 9.9 ~ 3998 2
12 NGC 1097 LIN 02 46 19.059 -30 16 29.68 10.46 9.97 9.48 8.72 9.8 ~ 1151 3
13 NGC 1142 Sy2 02 55 12.229 -00 11 00.77   15.42 14.41     ~ 292 1
14 NGC 1365 Sy1 03 33 36.458 -36 08 26.37 10.48 10.08 9.63 8.79 9.7 ~ 1480 2
15 IC 342 SBG 03 46 48.514 +68 05 45.98   10.5       ~ 1364 1
16 NGC 1530 G 04 23 27.102 +75 17 44.05   13.40       ~ 250 1
17 NGC 1614 AGN 04 34 00.027 -08 34 44.57   14.66 13.99     ~ 594 0
18 ZW VII 31 G 05 16 46.384 +79 40 12.63   15.8       ~ 134 0
19 2MASX J05210136-2521450 Sy2 05 21 01.3987198411 -25 21 45.269338983   15.47 14.75     ~ 420 0
20 NGC 2146 SBG 06 18 37.710 +78 21 25.27 11.67 11.38 10.59     ~ 604 2
21 NGC 2276 IG 07 27 14.485 +85 45 16.20   12.3       ~ 337 0
22 UGC 4881 IG 09 15 55.5 +44 19 58   14.9       ~ 155 0
23 NGC 2905 H2G 09 32 10.111 +21 30 02.99 10.44 9.75 9.07 8.68   ~ 969 3
24 UGC 5101 Sy1 09 35 51.694 +61 21 10.52   15.20 15.50     ~ 500 4
25 M 82 IG 09 55 52.430 +69 40 46.93 9.61 9.30 8.41     ~ 5236 6
26 NGC 3079 Sy2 10 01 57.80342 +55 40 47.2428 11.57 11.54 10.86     ~ 1221 3
27 NGC 3147 Sy2 10 16 53.632 +73 24 02.34   11.43 10.61     ~ 414 2
28 NGC 3256 IG 10 27 51.284 -43 54 13.55   11.83 11.33 10.62 11.9 ~ 735 2
29 2XMM J105918.1+243234 LIN 10 59 18.128 +24 32 34.74   15.7       ~ 234 1
30 APG 148 IG 11 03 53.892 +40 50 59.89   14.29       ~ 157 1
31 M 108 SBG 11 11 30.967 +55 40 26.84   10.70       ~ 402 1
32 M 66 GiP 11 20 15.026 +12 59 28.64 9.85 9.65 8.92     ~ 1124 4
33 NGC 3628 GiP 11 20 17.018 +13 35 22.16   10.42 9.48 9.22   ~ 736 3
34 NAME NGC 3690 West GiP 11 28 30.69 +58 33 33.4   11.8       ~ 604 4
35 UGC 6472 C G 11 28 30.70 +58 33 48.4           ~ 351 0
36 NGC 3690 IG 11 28 31.326 +58 33 41.80   13.19 12.86     ~ 870 4
37 NAME NGC 3690 East AGN 11 28 33.07 +58 33 54.2   11.8       ~ 609 4
38 NGC 3893 GiP 11 48 38.207 +48 42 38.84   11.23 10.67     ~ 324 1
39 NGC 4030 GiP 12 00 23.6122434029 -01 06 00.223672461   11.42   10.3 10.4 ~ 285 1
40 NGC 4041 SyG 12 02 12.2373728821 +62 08 14.095878409   11.6       ~ 223 1
41 NGC 4414 GiG 12 26 27.089 +31 13 24.76 11.12 10.96 10.12     ~ 507 2
42 NGC 4631 GiP 12 42 08.009 +32 32 29.44   9.78 9.19 9.10   ~ 944 2
43 Mrk 231 Sy1 12 56 14.2340989340 +56 52 25.238555193   14.68 13.84     ~ 1742 3
44 M 64 SyG 12 56 43.696 +21 40 57.57   9.36 8.52     ~ 791 2
45 NGC 4945 Sy2 13 05 27.279 -49 28 04.44   9.31 14.40 7.55   ~ 1231 2
46 NGC 5005 GiP 13 10 56.312 +37 03 32.19   14.67 13.67     ~ 489 2
47 M 63 LIN 13 15 49.2738527699 +42 01 45.726078017   9.34 8.59 8.35   ~ 1025 2
48 IC 883 SBG 13 20 35.380 +34 08 21.84   14.8       ~ 362 1
49 NGC 5135 Sy2 13 25 44.059 -29 50 01.24   12.58 13.35 11.53 12.2 ~ 415 1
50 M 51 GiP 13 29 52.698 +47 11 42.93   9.26 8.36 8.40   ~ 3696 4
51 M 83 SBG 13 37 00.919 -29 51 56.74 8.85 8.11 7.52 7.21   ~ 2168 2
52 Mrk 273 Sy2 13 44 42.070 +55 53 13.17   15.68 14.91     ~ 814 3
53 QSO J1415+1129 QSO 14 15 46.25 +11 29 43.4   17.63 17.23     ~ 581 1
54 NGC 5678 AGN 14 32 05.5716657614 +57 55 17.157051439   12.10       ~ 203 1
55 NGC 5713 GiP 14 40 11.528 -00 17 21.16 11.88 11.84 11.20     ~ 338 2
56 NGC 5775 GiP 14 53 57.653 +03 32 40.10   13.0 11.34     ~ 383 2
57 UGC 9618 IG 14 57 00.4 +24 36 44   14.3       ~ 109 1
58 IC 4553 SyG 15 34 57.22396 +23 30 11.6084   14.76 13.88     ~ 2629 4
59 NGC 6240 Sy2 16 52 58.861 +02 24 03.55   14.31 13.37     ~ 1450 2
60 6dFGS gJ172322.0-001701 LIN 17 23 21.943 -00 17 00.96   15.1       ~ 368 0
61 2MASX J18324117-3411274 EmG 18 32 41.177 -34 11 27.46   15.63   13.66   ~ 98 0
62 NGC 6670 PaG 18 33 35.40 +59 53 19.7           ~ 61 1
63 2MASX J18333768+5953227 IG 18 33 37.683 +59 53 22.76           ~ 62 0
64 NGC 6701 G 18 43 12.429 +60 39 12.13   12.9       ~ 115 1
65 NGC 6921 Sy2 20 28 28.843 +25 43 24.19   15.0       ~ 77 1
66 NGC 6946 H2G 20 34 52.332 +60 09 13.24   10.5       ~ 2188 2
67 NGC 6951 Sy2 20 37 14.1181441937 +66 06 20.078027288   11.64 10.65     ~ 490 2
68 NGC 7130 AGN 21 48 19.490 -34 57 04.73   12.86 13.87 11.57   ~ 375 0
69 IC 5179 EmG 22 16 09.1156883076 -36 50 37.102745221   12.29 11.89 11.38   ~ 171 1
70 NGC 7331 LIN 22 37 04.102 +34 24 57.31 10.65 10.35 9.48     ~ 1086 2
71 NGC 7469 Sy1 23 03 15.674 +08 52 25.28 12.60 13.00 12.34     ~ 1848 3
72 NGC 7479 Sy2 23 04 56.668 +12 19 22.36 11.74 11.60 10.85 10.47 9.66 ~ 653 2
73 2MASX J23390127+3621087 SyG 23 39 01.274 +36 21 08.77   16.17       ~ 193 1
74 NGC 7771 GiG 23 51 24.880 +20 06 42.57 13.42 13.08 12.25     ~ 307 4
75 Mrk 331 GiP 23 51 26.731 +20 35 10.22   14.9       ~ 210 0

    Equat.    Gal    SGal    Ecl

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2019.12.10-08:35:05

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