2007ApJ...669L...9D

Query : 2007ApJ...669L...9D

2007ApJ...669L...9D - Astrophys. J., 669, L9-L12 (2007/November-1)

A dense gas trigger for OH megamasers.

DARLING J.

Abstract (from CDS):

HCN and CO line diagnostics provide new insight into the OH megamaser (OHM) phenomenon, suggesting a dense gas trigger for OHMs. We identify three physical properties that differentiate OHM hosts from other starburst galaxies: (1) OHMs have the highest mean molecular gas densities among starburst galaxies; nearly all OHM hosts have n{d1}(H2)=103-104/cm3 (OH line-emitting clouds likely have n(H2)>104/cm3). (2) OHM hosts are a distinct population in the nonlinear part of the IR-CO relation. (3) OHM hosts have exceptionally high dense molecular gas fractions, LHCN/LCO>0.07, and comprise roughly half of this unusual population. OH absorbers and kilomasers generally follow the linear IR-CO relation and are uniformly distributed in dense gas fraction and LHCN, demonstrating that OHMs are independent of OH abundance. The fraction of non-OHMs with high mean densities and high dense gas fractions constrains beaming to be a minor effect: OHM emission solid angle must exceed 2π steradians. Contrary to conventional wisdom, IR luminosity does not dictate OHM formation; both star formation and OHM activity are consequences of tidal density enhancements accompanying galaxy interactions. The OHM fraction in starbursts is likely due to the fraction of mergers experiencing a temporal spike in tidally driven density enhancement. OHMs are thus signposts marking the most intense, compact, and unusual modes of star formation in the local universe. Future high-redshift OHM surveys can now be interpreted in a star formation and galaxy evolution context, indicating both the merging rate of galaxies and the burst contribution to star formation.

Abstract Copyright: ∼

Journal keyword(s): Galaxies: Interactions - Galaxies: Nuclei - Galaxies: Starburst - Masers - Radio Lines: Galaxies

Simbad objects: 69

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Number of rows : 69
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024 		#notes
1 NGC 253 SyG 00 47 33.134 -25 17 19.68   8.03   6.94 8.1 ~ 3336 2
2 IC 1623 IG 01 07 47.380 -17 30 24.51   15       ~ 310 2
3 NGC 520 AG? 01 24 34.90 +03 47 29.4 12.41 12.24 11.42     ~ 513 3
4 NGC 660 Sy2 01 43 02.350 +13 38 44.45   12.02 11.16     ~ 556 2
5 ZW III 35 Sy2 01 44 30.516 +17 06 09.18   15.24 14.81     ~ 249 0
6 NGC 828 rG 02 10 09.5469097104 +39 11 25.233638244   13.0       ~ 164 1
7 NGC 891 H2G 02 22 32.907 +42 20 53.95 11.08 10.81 9.93 7.86   ~ 1667 2
8 NGC 1022 GiG 02 38 32.703 -06 40 38.60 12.33 12.09 11.34     ~ 203 1
9 NGC 1055 GiP 02 41 45.233 +00 26 35.45 11.59 11.40 10.59 10.5 10.7 ~ 283 2
10 M 77 Sy2 02 42 40.7091669408 -00 00 47.859690204 9.70 9.61 8.87 10.1 9.9 ~ 4602 2
11 NGC 1142 Sy2 02 55 12.2311509144 -00 11 00.807149472   15.42 14.41     ~ 330 1
12 NGC 1365 Sy1 03 33 36.458 -36 08 26.37 10.48 10.08 9.63 8.79 9.7 ~ 1802 2
13 IC 342 SBG 03 46 48.514 +68 05 45.98   10.5       ~ 1517 1
14 IRAS 03521+0028 LIN 03 54 42.146 +00 37 03.33           ~ 93 0
15 NGC 1614 Sy1 04 34 00.027 -08 34 44.57   14.66 13.99     ~ 667 0
16 ZW VII 31 G 05 16 46.384 +79 40 12.63   15.8       ~ 150 0
17 LEDA 17155 Sy2 05 21 01.3994605776 -25 21 45.321827832   15.47 14.75     ~ 498 0
18 NGC 2146 SBG 06 18 37.710 +78 21 25.27 11.67 11.38 10.59     ~ 721 2
19 NGC 2276 AG? 07 27 14.485 +85 45 16.20   12.3       ~ 376 0
20 UGC 4881 IG 09 15 55.5 +44 19 58   14.9       ~ 169 0
21 NGC 2905 H2G 09 32 10.111 +21 30 02.99 10.44 9.75 9.07 8.68   ~ 1116 3
22 UGC 5101 Sy2 09 35 51.6045544584 +61 21 11.589382368   15.20 15.50     ~ 572 4
23 M 82 AGN 09 55 52.430 +69 40 46.93 9.61 9.30 8.41     ~ 5860 6
24 NGC 3079 Sy2 10 01 57.8789863992 +55 40 47.449758324 11.57 11.54 10.86     ~ 1391 3
25 LEDA 33083 LIN 10 59 18.128 +24 32 34.74   15.7       ~ 274 1
26 APG 148 IG 11 03 54.0 +40 51 00   14.29       ~ 177 1
27 M 108 SBG 11 11 30.967 +55 40 26.84   10.70       ~ 471 1
28 M 66 GiP 11 20 15.0 +12 59 29 9.85 9.65 8.92     ~ 1386 4
29 NGC 3628 GiP 11 20 17.018 +13 35 22.16   10.42 9.48 9.22   ~ 827 3
30 UGC 6472 C G 11 28 30.70 +58 33 48.4           ~ 351 0
31 NGC 3690 IG 11 28 31.0 +58 33 41   13.19 12.86     ~ 978 4
32 NAME NGC 3690 West GiP 11 28 31.02 +58 33 40.7   11.8       ~ 629 4
33 NAME NGC 3690 East AGN 11 28 33.07 +58 33 54.2   11.8       ~ 631 4
34 NGC 3893 GiP 11 48 38.207 +48 42 38.84   11.23 10.67     ~ 369 1
35 NGC 4030 GiP 12 00 23.6102390784 -01 06 00.197099136   11.42   10.3 10.4 ~ 340 1
36 NGC 4041 SyG 12 02 12.2376697152 +62 08 14.096124312   11.6       ~ 252 1
37 NGC 4414 GiG 12 26 27.1276893168 +31 13 24.626206488 11.12 10.96 10.12     ~ 567 2
38 NGC 4631 GiP 12 42 08.009 +32 32 29.44   9.78 9.19 9.10   ~ 1095 2
39 Mrk 231 Sy1 12 56 14.2341182928 +56 52 25.238373852   14.68 13.84     ~ 1988 3
40 M 64 SyG 12 56 43.696 +21 40 57.57   9.36 8.52     ~ 940 2
41 NGC 4945 Sy2 13 05 27.279 -49 28 04.44   9.31 14.40 7.55   ~ 1475 2
42 NGC 5005 GiP 13 10 56.312 +37 03 32.19   14.67 13.67     ~ 541 2
43 M 63 LIN 13 15 49.2741893928 +42 01 45.728076108   9.34 8.59 8.35   ~ 1224 2
44 IC 883 SBG 13 20 35.4 +34 08 22   14.8       ~ 400 1
45 NGC 5135 Sy2 13 25 44.059 -29 50 01.24   12.58 13.35 11.53 12.2 ~ 474 1
46 M 51 Sy2 13 29 52.698 +47 11 42.93   9.26 8.36 8.40   ~ 4330 4
47 M 83 SBG 13 37 00.91920 -29 51 56.7400 8.85 8.11 7.52 7.21   ~ 2573 2
48 Mrk 273 Sy2 13 44 42.1781 +55 53 12.819   15.68 14.91     ~ 913 3
49 LEDA 165630 Sy2 14 09 31.257 +05 11 31.31     17.00     ~ 73 0
50 NGC 5678 AGN 14 32 05.5700264952 +57 55 17.155392060   12.10       ~ 227 1
51 NGC 5713 GiP 14 40 11.528 -00 17 21.16 11.88 11.84 11.20     ~ 398 2
52 NGC 5775 GiP 14 53 57.653 +03 32 40.10   13.0 11.34     ~ 434 2
53 IC 4553 SyG 15 34 57.22396 +23 30 11.6084   14.76 13.88     ~ 2961 4
54 LEDA 90237 LIN 16 11 40.4280459768 -01 47 06.566246232   16.6       ~ 82 0
55 NGC 6240 Sy2 16 52 58.9 +02 24 03   14.31 13.37     ~ 1637 2
56 LEDA 60189 LIN 17 23 21.943 -00 17 00.96   15.1       ~ 424 0
57 LEDA 84885 Sy1 18 32 41.177 -34 11 27.46   15.63   13.66   ~ 130 0
58 PSCz Q18368+3549 Sy2 18 38 35.435 +35 52 19.75           ~ 36 0
59 NGC 6701 AG? 18 43 12.429 +60 39 12.13   12.9       ~ 133 1
60 NGC 6921 Sy2 20 28 28.8658027224 +25 43 24.094324884 15.41   12.897     ~ 95 1
61 NGC 6946 H2G 20 34 52.332 +60 09 13.24   10.5       ~ 2529 2
62 NGC 7130 Sy2 21 48 19.5412287192 -34 57 04.492024884   12.86 13.87 11.57   ~ 450 0
63 IC 5179 Sy1 22 16 09.1191653256 -36 50 37.117603752   12.29 11.89 11.38   ~ 204 1
64 NGC 7331 LIN 22 37 04.0506038088 +34 24 56.800076508 10.65 10.35 9.48     ~ 1228 2
65 NGC 7469 Sy1 23 03 15.6 +08 52 26 12.60 13.00 12.34     ~ 2095 3
66 NGC 7479 Sy2 23 04 56.6432243448 +12 19 22.357387020 11.74 11.60 10.85 10.47 9.66 ~ 743 2
67 LEDA 90429 SyG 23 39 01.274 +36 21 08.77   16.17       ~ 216 1
68 NGC 7771 GiG 23 51 24.880 +20 06 42.57 13.42 13.08 12.25     ~ 338 4
69 Mrk 331 GiP 23 51 26.731 +20 35 10.22   14.9       ~ 227 0

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