2001A&A...367..457C


C.D.S. - SIMBAD4 rel 1.7 - 2020.08.07CEST12:16:08

2001A&A...367..457C - Astronomy and Astrophysics, volume 367, 457-469 (2001/2-4)

Molecular gas conditions in NGC 4945 and the Circinus galaxy.

CURRAN S.J., JOHANSSON L.E.B., BERGMAN P., HEIKKILAE A. and AALTO S.

Abstract (from CDS):

We present results of a multi-transition study of the dense molecular gas in the central part of the hybrid star-burst/Seyfert galaxies NGC 4945 and the Circinus galaxy. From the results of radiative transfer calculations, we estimate in NGC 4945 nH2=3x103-104cm–3 and Tkin≃100K and in Circinus nH2=2x103-105cm–3 and Tkin≃50-80K for the molecular hydrogen density and kinetic temperature, respectively. As well as density/temperature tracing molecules, we have observed C17O and C18O in each galaxy and the value of C18O/C17O≃6 for the isotopic column density ratio suggests that both have relatively high populations of massive stars. Finally, although star formation is present, the radiative transfer results combined with the high HCN/CO and (possibly) HCN/FIR, radio/FIR ratios may suggest that, in comparison with Circinus, a higher proportion of the dense gas emission in NGC 4945 may be located in the hypothesised central nuclear disk as opposed to dense star forming cloud cores. Contrary to the literature, which assumes that all of the far-infrared emission arises from star formation, our results suggest that in NGC 4945 some of this emission could arise from an additional source, and so we believe that a revision of the star formation rate estimates may be required for these two galaxies.

Abstract Copyright:

Journal keyword(s): galaxies: abundances - galaxies: individual: NGC 4945, Circinus - galaxies: nuclei - galaxies: Seyfert - galaxies: star-burst

Simbad objects: 4

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Number of rows : 4

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 ~ 2936 2
2 M 82 IG 09 55 52.430 +69 40 46.93 9.61 9.30 8.41     ~ 5342 6
3 NGC 4945 Sy2 13 05 27.279 -49 28 04.44   9.31 14.40 7.55   ~ 1267 2
4 NAME Circinus Galaxy Sy2 14 13 09.906 -65 20 20.47   10.89 9.84 10.6 10.0 ~ 1009 2

    Equat.    Gal    SGal    Ecl

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2020.08.07-12:16:08

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