High-resolution HNC 3-2 SMA observations of Arp 220
Artikel i vetenskaplig tidskrift, 2009

Aims. We study the properties of the nuclear molecular gas of the ultra luminous merger Arp 220 and effects of the nuclear source on gas excitation and chemistry. Specifically, our aim is to investigate the spatial location of the luminous HNC 3-2 line emission and address the underlying cause of its unusual brightness. Methods. We present high resolution observations of HNC J=3-2 with the submillimeter array (SMA). Results. We find luminous HNC 3-2 line emission in the western part of Arp 220, centred on the western nucleus, while the eastern side of the merger shows relatively faint emission. A bright (36 K at $0\hbox{$.\!\!^{\prime\prime}$ }4$ resolution), narrow (60 ${\rm km~s}^$) emission feature emerges from the western nucleus, superposed on a broader spectral component. A possible explanation is weak maser emission through line-of-sight amplification of the background continuum source. There is also a more extended HNC 3-2 emission feature north and south of the nucleus. This feature resembles the bipolar OH maser morphology around the western nucleus. Substantial HNC abundances are required to explain the bright line emission from this warm environment - even when the high gas column density towards the western nucleus is taken into account. We discuss this briefly in the context of an X-ray affected chemistry and radiative excitation. Conclusions. The luminous and possibly amplified HNC emission of the western nucleus of the Arp 220 merger reflects the unusual, and perhaps transient environment of the starburst/AGN activity there. The faint HNC line emission towards Arp 220-east reveals a real difference in physical conditions between the two merger nuclei.

radio lines: ISM

galaxies: evolution

ISM: molecules

galaxies: active

galaxies: individual: Arp 220

galaxies: starburst


Susanne Aalto

Chalmers, Institutionen för radio- och rymdvetenskap, Radioastronomi och astrofysik

D.J. Wilner

Harvard-Smithsonian Center for Astrophysics

M. Spaans

Kapteyn Astronomical Institute

M.C. Wiedner

Universität zu Köln

K. Sakamoto

National Astronomical Observatory of Japan

Academia Sinica

Harvard-Smithsonian Center for Astrophysics

John H Black

Chalmers, Institutionen för radio- och rymdvetenskap, Radioastronomi och astrofysik

M. Caldas

Chalmers, Institutionen för radio- och rymdvetenskap

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 493 2 481-487


Astronomi, astrofysik och kosmologi



Mer information

Senast uppdaterat