2001A&A...371..433I


Query : 2001A&A...371..433I

2001A&A...371..433I - Astronomy and Astrophysics, volume 371, 433-444 (2001/5-4)

CI and CO in the spiral galaxies NGC 6946 and M 83.

ISRAEL F.P. and BAAS F.

Abstract (from CDS):

We present J=2-1, J=3-2, J=4-3 12CO and 492 GHz [CI] maps as well as J=2-1 and J=3-2 13CO measurements of the late type spiral galaxies NGC 6946 and M 83 (NGC 5236). Both galaxies contain a pronounced molecular gas concentration in rapid solid-body rotation within a few hundred parsec from their nucleus. NGC 6946 and M 83 have nearly identical relative intensities in the 12CO, 13CO and [CI] transitions, but very different [CII] intensities, illustrating the need for caution in interpreting CO observations alone. The slow decrease of velocity-integrated 12CO intensities with increasing rotational level implies the presence of significant amounts of warm and dense molecular gas in both galaxy centers. Detailed modelling of the observed line ratios indicates that the molecular medium in both galaxies consists of at least two separate components. These are a warm and dense component (Tkin=30-60K, n(H2)=3000-10000cm–3) and a much more tenuous hot component (Tkin=100-150K, n(H2)≤1000cm–3). Total atomic carbon column densities exceed CO column densities by a factor of about 1.5 in NGC 6946 and about 4 in M 83. Unlike NGC 6946, M 83 contains a significant amount of molecular hydrogen associated with ionized carbon rather than CO. The centers of NGC 6946 and M 83 contain nearly identical total (atomic and molecular) gas masses of about 3x107M. Despite their prominence, the central gas concentrations in these galaxies represent only a few per cent of the stellar mass in the same volume. The peak face-on gas mass density is much higher in M 83 (120M/pc2) than in NGC 6946 (45M/pc2). The more intense starburst in M 83 is associated with a more compact and somewhat hotter PDR zone than the milder starburst in NGC 6946.

Abstract Copyright:

Journal keyword(s): galaxies - individual: NGC 6946, M 83 - ISM - centers - radio lines - galaxies - ISM - molecules

CDS comments: in ref list: Crawford 1985ApJ...291..755C instead of 1985A&A.291, Stacey 1991ApJ...373..423S instead of 1985A&A

Simbad objects: 11

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Number of rows : 11
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 11880 1
2 NGC 253 SyG 00 47 33.134 -25 17 19.68   8.03   6.94 8.1 ~ 3149 2
3 M 82 IG 09 55 52.430 +69 40 46.93 9.61 9.30 8.41     ~ 5616 6
4 NGC 3628 GiP 11 20 17.018 +13 35 22.16   10.42 9.48 9.22   ~ 790 3
5 NGC 4945 Sy2 13 05 27.279 -49 28 04.44   9.31 14.40 7.55   ~ 1375 2
6 NAME Centaurus A Sy2 13 25 27.6039817176 -43 01 09.493008456   8.18 6.84 6.66   ~ 4263 3
7 M 83 SBG 13 37 00.91920 -29 51 56.7400 8.85 8.11 7.52 7.21   ~ 2410 2
8 NGC 5253 AGN 13 39 55.990 -31 38 24.11 11.48 10.94 10.49 10.33   ~ 1316 4
9 NGC 6643 G 18 19 46.370 +74 34 06.23   11.80       ~ 296 1
10 NGC 6946 H2G 20 34 52.332 +60 09 13.24   10.5       ~ 2384 2
11 NGC 7331 LIN 22 37 04.0506038088 +34 24 56.800076508 10.65 10.35 9.48     ~ 1174 2

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2022.08.10-08:05:42

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