Issue |
A&A
Volume 562, February 2014
|
|
---|---|---|
Article Number | A96 | |
Number of page(s) | 15 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/201322780 | |
Published online | 13 February 2014 |
The molecular circumnuclear disk (CND) in Centaurus A
A multi-transition CO and [CI] survey with Herschel, APEX, JCMT, and SEST
1
Sterrewacht Leiden, Leiden University,
PO Box 9513,
2300 RA
Leiden,
The Netherlands
e-mail:
israel@strw.leidenuniv.nl
2
Max-Planck-Institut für Radioastronomie,
Auf dem Hügel 69, 53121
Bonn,
Germany
3
Kapteyn Astronomical Institute, Postbus 800, 9700 AV
Groningen, The
Netherlands
4
I. Physikalisches Institut der Universität zu Köln,
Zülpicher Strasse 77,
50937
Köln,
Germany
5
Department of Astronomy, University of Maryland,
College Park, MD
20742,
USA
6
IRAM, Avenida Divina Pastora, 7, Núcleo Central,
18012
Granada,
Spain
7
CSIC/INTA, Ctra de Torrejón a Ajalvir, km 4, 28850 Torrejón de
Ardoz, Madrid,
Spain
Received: 2 October 2013
Accepted: 16 December 2013
This paper presents emission line intensities of CO and C° from the compact circumnuclear disk in the center of NGC 5128 (Centaurus A) obtained with the Herschel Space Observatory in the 400–1000 GHz range as well as previously unpublished measurements obtained with the ground-based observatories SEST, JCMT and APEX in the 90–800 GHz range. The results show that the Cen A center has an emission ladder of CO transitions quite different from those of either star-burst galaxies or (Seyfert) AGNs. In addition, the neutral carbon ([CI]) emission lines from the Cen A center are much stronger relative to the adjacent CO lines than in any other galaxy. The CO surface brightness of the compact circumnuclear disk (CND) is significantly higher than that of the much more extended thin disk (ETD) in the same line of sight. LVG analysis of the CO line profiles decomposed into the constituent contributions show that the ETD is relatively cool and of low excitation, wheres the brighter CND is hotter and more highly excited. Our PDR/XDR models suggest that most of the CND gas is relatively cool (temperatures 25 K–80 K) and not very dense (≈300 cm-3) if it is primarily heated by UV photons. A small fraction of the gas in both the CND and the ETD has a much higher density (typically 30 000 cm-3). A more highly excited, high-density phase is present in the CND, either in the form of an extreme PDR or more likely in the form of an XDR. Such a phase does not occur in the part of the ETD sampled. We have determined, for the first time, the molecular mass parameters of the CND. The total gas mass of the CND is MCND = 8.4 × 107 M⊙, uncertain by a factor of two. The CO-H2 conversion factor (XCND) is 4 × 1020 (K km s-1)-1 also within a factor of two.
Key words: ISM: molecules / galaxies: active / galaxies: elliptical and lenticular, cD / galaxies: individual: Centaurus A / galaxies: ISM / galaxies: nuclei
© ESO, 2014
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.