2010A&A...517A..82R


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.12CEST09:20:52

2010A&A...517A..82R - Astronomy and Astrophysics, volume 517, A82-82 (2010/7-1)

Detection of the H92α recombination line from NGC 4945.

ROY A.L., OOSTERLOO T., GOSS W.M. and ANANTHARAMAIAH K.R.

Abstract (from CDS):

Hydrogen ionized by young, high-mass stars in starburst galaxies radiates radio recombination lines (RRLs), whose strength can be used as a diagnostic of the ionization rate, conditions and gas dynamics in the starburst region, without problems of dust obscuration. However, the lines are weak and only few extragalactic starburst systems have been detected. We aimed to increase the number of known starburst systems with detectable RRLs for detailed studies, and we used the line properties to study the gas properties and dynamics. We searched for the RRLs H91α and H92α with rest frequencies of 8.6GHz and 8.3GHz in the nearby southern Seyfert galaxy NGC 4945 using the Australia Telescope Compact Array with resolution of 3''. This yielded a detection from which we derived conditions in the starburst regions. We detected RRLs from the nucleus of NGC 4945 with a peak line strength integrated over the source of 17.8mJy, making it the strongest extragalactic RRL emitter known at this frequency. The line and continuum emission from NGC 4945 can be matched by a model consisting of a collection of 10 to 300 H II regions with temperatures of 5000K, densities of 103cm–3 to 104cm–3 and a total effective diameter of 2pc to 100pc. The Lyman continuum production rate required to maintain the ionization is 6x1052s–1 to 3x1053s–1, which requires 2000 to 10000 O5 stars to be produced in the starburst, inferring a star formation rate of 2M/yr to 8M/yr. We resolved the rotation curve within the central 70pc region and this is well described by a set of rotating rings that were coplanar and edge on. We found no reason to depart from a simple flat rotation curve. The rotation speed of 120km/s within the central 1'' (19pc) radius infers an enclosed mass of 3x107M, and an average surface density with the central 19pc of 25000pc–2, which exceeds the threshold gas surface density for star formation. We discovered RRLs from NGC 4945. It is the strongest known extragalactic RRL emitter and is suited to high-quality spectroscopic study. We resolved the dynamics of the ionized gas in the central 70pc and derived conditions and star formation rates in the ionized gas.

Abstract Copyright:

Journal keyword(s): galaxies: individual: NGC 4945 - galaxies: nuclei - radio lines: galaxies

Simbad objects: 8

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Number of rows : 8

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 M 42 HII 05 35 17.3 -05 23 28           ~ 3724 0
2 NGC 3256 IG 10 27 51.284 -43 54 13.55   11.83 11.33 10.62 11.9 ~ 755 2
3 3C 273 BLL 12 29 06.6996828061 +02 03 08.598846466   13.05 14.830 14.11   ~ 5320 1
4 NGC 4945 Sy2 13 05 27.279 -49 28 04.44   9.31 14.40 7.55   ~ 1265 2
5 [VV2006] J132304.3-445233 QSO 13 23 04.2505439851 -44 52 33.813892851     17.6     ~ 47 1
6 NAME Circinus Galaxy Sy2 14 13 09.906 -65 20 20.47   10.89 9.84 10.6 10.0 ~ 1008 2
7 ICRF J193925.0-634245 Sy2 19 39 25.02671 -63 42 45.6255   18.87 18.37 17.64   ~ 954 1
8 3C 454.3 QSO 22 53 57.74798 +16 08 53.5611   16.57 16.10 15.22   ~ 2506 2

    Equat.    Gal    SGal    Ecl

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2020.07.12-09:20:52

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