1997A&A...325...81P


Query : 1997A&A...325...81P

1997A&A...325...81P - Astronomy and Astrophysics, volume 325, 81-97 (1997/9-1)

Circumnuclear molecular gas and star formation in starburst galaxies.

PLANESAS P., COLINA L. and PEREZ-OLEA D.

Abstract (from CDS):

The molecular gas properties and circumnuclear star formation in the nearby nuclear starburst galaxies NGC 2903, NGC 3351 and NGC 3504 are investigated in detail. The circumnuclear HII regions in the star-forming rings of these galaxies are characterised by an ionized gas mass in the 104-105M range, and by an ionizing flux in the 1051-1052ph/s range, typical of giant HII regions in external galaxies. The CO 2->1 emission in NGC 3504 indicates the presence of two emitting regions separated by 115km/s in velocity and 5" (500pc) spatially, what approximately corresponds to the location of the the inner inner Lindblad resonance. The measured (CO 2->1)/(CO 1->0) integrated intensity ratio for the inner kpc of NGC 3351 is 0.8, in agreement with the empirical average value found for spiral galaxies with a normal metallicity regardless of the presence or the absence of a starburst. Molecular gas masses in the range of MH2≃108-109M are measured in regions of a few hundred parsecs in size. On average, the circumnuclear region of the three galaxies is characterised by an average molecular gas surface density {SIGMA}H2=280M/pc2, and average LIR/MH2=21L/M. The LIR/MH2-{SIGMA}H2 relationship covering the {SIGMA}H2 range from normal spiral galaxies and giant molecular clouds in the Milky Way with {SIGMA}H2∼101-102M/pc2, to nearby starbursts, AGNs with starbursts, and luminous IRAS galaxies with {SIGMA}H2∼2x102-105M/pc2, is investigated. Nearby starburst galaxies have an average molecular gas surface density {SIGMA}H2 of 400M/pc2 and an average LIR/MH2 of 23L/M. These two properties are explained by the existence of giant molecular clouds with associated HII regions where the star formation process is characterised by being short lived (≤3x107years), biased towards a high lower mass limit Ml∼3M, and with an overall gas to stars conversion fraction of ≤10% of the gas mass. The star formation efficiency (SFE) in nearby starbursts and luminous IRAS galaxies (as measured by the LIR/MH2 ratio) does not show any indication of a linear correlation with increasing {SIGMA}H2. On the contrary, the star formation efficiency is restricted to the 10<LIR/MH2<100L/M range, and reaches a maximum value of LIR/MH2=100L/M for {SIGMA}H2 larger than 103M/pc2. The upper limit found for the LIR/MH2 ratio, independent of {SIGMA}H2, implies the existence of an upper limit in the fraction of gas converted into stars independent of the density. The SFE range observed in nearby starbursts, Seyferts with starbursts, and luminous IRAS galaxies is explained as a combination of massive star formation in the circumnuclear regions of these galaxies plus the additional contribution of an AGN at the center of the galaxy. Under the starburst+AGN scenario, most of the molecular gas mass is directly involved in the star forming process while the AGN contribution to the global IR luminosity is in the 10% to 75% range, depending on the galaxy. In this scenario, the infrared luminosity of galaxies with observed LIR/MH2 ratio in the 10 to 30L/M range is dominated by the circumnuclear star formation alone. The infrared luminosity in those galaxies with LIR/MH2 in the 30-100L/M range is increasingly dominated by the central AGN. Examples of this situation are NGC 1068, NGC 7469 and Mrk 231.

Abstract Copyright:

Journal keyword(s): galaxies: general - galaxies: ISM - galaxies: Seyfert - galaxies: starburst

Nomenclature: Fig.7, Table 3a: [PCP97] NGC 2903 RN (Nos R1-R8). Fig.8, Table 3b: [PCP97] NGC 3351 RN (Nos R1-R8). Fig.9, Table 3c: [PCP97] NGC 3504 RN (Nos R1-R4).

Status at CDS : All or part of tables of objects will not be ingested in SIMBAD.

Simbad objects: 54

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Number of rows : 54
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 IC 1623 IG 01 07 47.2 -17 30 25   15       ~ 269 1
2 NGC 520 IG 01 24 35.071 +03 47 32.68 12.41 12.24 11.42     ~ 498 3
3 M 33 GiG 01 33 50.904 +30 39 35.79 6.17 6.27 5.72     ~ 5320 1
4 Mrk 1014 Sy1 01 59 50.2529351498 +00 23 40.874250335   16.08 15.87     ~ 524 0
5 NGC 828 rG 02 10 09.5458704337 +39 11 25.220114583   13.0       ~ 153 1
6 M 77 GiP 02 42 40.771 -00 00 47.84 9.70 9.61 8.87 10.1 9.9 ~ 4225 2
7 NGC 1097 LIN 02 46 19.059 -30 16 29.68 10.46 9.97 9.48 8.72 9.8 ~ 1215 3
8 NGC 1614 AGN 04 34 00.027 -08 34 44.57   14.66 13.99     ~ 620 0
9 ZW VII 31 G 05 16 46.384 +79 40 12.63   15.8       ~ 139 0
10 NGC 2146 SBG 06 18 37.710 +78 21 25.27 11.67 11.38 10.59     ~ 648 2
11 UGC 4881 IG 09 15 55.5 +44 19 58   14.9       ~ 161 0
12 [PCP97] NGC 2903 R2 HII 09 32 09.9 +21 30 07           ~ 4 0
13 [PCP97] NGC 2903 R3 HII 09 32 10.0 +21 30 04           ~ 2 0
14 [PCP97] NGC 2903 R1 HII 09 32 10.0 +21 30 08           ~ 4 0
15 [PCP97] NGC 2903 R4 HII 09 32 10.1 +21 30 01           ~ 4 0
16 [PCP97] NGC 2903 R7 HII 09 32 10.1 +21 30 08           ~ 3 0
17 [PCP97] NGC 2903 R8 HII 09 32 10.1 +21 30 10           ~ 1 0
18 NGC 2905 H2G 09 32 10.111 +21 30 02.99 10.44 9.75 9.07 8.68   ~ 1024 3
19 [PCP97] NGC 2903 R5 HII 09 32 10.2 +21 30 04           ~ 1 0
20 [PCP97] NGC 2903 R6 HII 09 32 10.3 +21 30 06           ~ 2 0
21 NGC 3079 Sy2 10 01 57.80342 +55 40 47.2428 11.57 11.54 10.86     ~ 1292 3
22 NVSS J102000+081335 rG 10 20 00.204 +08 13 33.78   17.5       ~ 146 1
23 NGC 3227 GiP 10 23 30.57 +19 51 54.3   12.61 11.79     ~ 1575 2
24 [PCP97] NGC 3351 R4 HII 10 43 57.320 +11 42 00.92           ~ 5 0
25 [PCP97] NGC 3351 R5 HII 10 43 57.550 +11 42 02.50           ~ 6 0
26 [PCP97] NGC 3351 R6 HII 10 43 57.600 +11 42 05.21           ~ 5 0
27 M 95 GiP 10 43 57.69173 +11 42 13.6274 10.71 10.51 9.73 9.48   M0 986 2
28 [PCP97] NGC 3351 R2 HII 10 43 57.8 +11 42 17           ~ 8 0
29 [PCP97] NGC 3351 R3 HII 10 43 57.9 +11 42 07           ~ 6 0
30 [PCP97] NGC 3351 R1 HII 10 43 58.0 +11 42 21           ~ 3 0
31 [PCP97] NGC 3351 R7 HII 10 43 58.3 +11 42 18           ~ 3 0
32 [PCP97] NGC 3351 R8 HII 10 43 58.3 +11 42 20           ~ 1 0
33 [PCP97] NGC 3504 R3 HII 11 03 11.1 +27 58 20           ~ 3 0
34 [PCP97] NGC 3504 R2 HII 11 03 11.1 +27 58 22           ~ 1 0
35 [PCP97] NGC 3504 R1 HII 11 03 11.1 +27 58 23           ~ 1 0
36 NGC 3504 LIN 11 03 11.191 +27 58 20.77   13.48 12.93     ~ 495 2
37 [PCP97] NGC 3504 R4 HII 11 03 11.2 +27 58 20           ~ 2 0
38 IC 694 G 11 28 27.312 +58 34 42.29   18.2       ~ 242 2
39 NAME NGC 3690 West GiP 11 28 30.69 +58 33 33.4   11.8       ~ 614 4
40 NGC 3690 IG 11 28 31.326 +58 33 41.80   13.19 12.86     ~ 911 4
41 NAME NGC 3690 East AGN 11 28 33.07 +58 33 54.2   11.8       ~ 618 4
42 NGC 4038 GiP 12 01 53.002 -18 52 03.32   10.91   9.74 11.0 ~ 1289 1
43 NAME Antennae IG 12 01 53.170 -18 52 37.92           ~ 1590 0
44 NGC 4039 GiP 12 01 53.8 -18 53 06   11.08   9.77   ~ 1138 1
45 M 100 AGN 12 22 54.9318850854 +15 49 20.294302163 10.04 10.05 9.35     ~ 1703 2
46 Mrk 231 Sy1 12 56 14.2340989340 +56 52 25.238555193   14.68 13.84     ~ 1843 3
47 M 51 GiP 13 29 52.698 +47 11 42.93   9.26 8.36 8.40   ~ 3948 4
48 Z 49-57 GiC 15 13 13.1 +07 13 32   15.5       ~ 216 1
49 IC 4553 SyG 15 34 57.22396 +23 30 11.6084   14.76 13.88     ~ 2758 4
50 NGC 6240 Sy2 16 52 58.861 +02 24 03.55   14.31 13.37     ~ 1525 2
51 6dFGS gJ172322.0-001701 LIN 17 23 21.943 -00 17 00.96   15.1       ~ 381 0
52 NGC 7469 Sy1 23 03 15.674 +08 52 25.28 12.60 13.00 12.34     ~ 1939 3
53 NGC 7714 GiP 23 36 14.099 +02 09 18.07   14.91 14.36     ~ 739 1
54 APG 284 PaG 23 36 19 +02 09.3   12.6       ~ 605 0

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2021.08.03-21:55:31

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