Hidden or missing outflows in highly obscured galaxy nuclei?
Artikel i vetenskaplig tidskrift, 2019
Understanding the nuclear growth and feedback processes in galaxies requires investigating their often obscured central regions. One way to do this is to use (sub)millimeter line emission from vibrationally excited HCN (HCN-vib), which is thought to trace warm and highly enshrouded galaxy nuclei. It has been suggested that the most intense HCN-vib emission from a galaxy is connected to a phase of nuclear growth that occurs before the nuclear feedback processes have been fully developed. Aims. We aim to investigate if there is a connection between the presence of strong HCN-vib emission and the development of feedback in (ultra)luminous infrared galaxies ((U)LIRGs). Methods. We collected literature and archival data to compare the luminosities of rotational lines of HCN-vib, normalized to the total infrared luminosity, to the median velocities of 119 μm OH absorption lines, potentially indicating outflows, in a total of 17 (U)LIRGs. Results. The most HCN-vib luminous systems all lack signatures of significant molecular outflows in the far-infrared OH absorption lines. However, at least some of the systems with bright HCN-vib emission have fast and collimated outflows that can be seen in spectral lines at longer wavelengths, including in millimeter emission lines of CO and HCN (in its vibrational ground state) and in radio absorption lines of OH. Conclusions. We conclude that the galaxy nuclei with the highest L HCN-vib /L IR do not drive wide-angle outflows that are detectable using the median velocities of far-infrared OH absorption lines. This is possibly because of an orientation effect in which sources oriented in such a way that their outflows are not along our line of sight also radiate a smaller proportion of their infrared luminosity in our direction. It could also be that massive wide-angle outflows destroy the deeply embedded regions responsible for bright HCN-vib emission, so that the two phenomena cannot coexist. This would strengthen the idea that vibrationally excited HCN traces a heavily obscured stage of evolution before nuclear feedback mechanisms are fully developed.
Galaxies: ISM
Galaxies: evolution
ISM: jets and outflows
ISM: molecules
Galaxies: nuclei
Författare
Niklas Falstad
Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik
F. Hallqvist
Chalmers, Rymd-, geo- och miljövetenskap
Susanne Aalto
Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik
Sabine König
Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik
Sebastien Muller
Chalmers, Rymd-, geo- och miljövetenskap, Onsala rymdobservatorium
Rebeca Aladro
Max-Planck-Gesellschaft
F. Combes
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
A. S. Evans
University of Virginia
National Radio Astronomy Observatory
G. A. Fuller
University of Manchester
J. S. Gallagher III
University of Wisconsin Madison
S. G. Burillo
Observatorio Astronómico Nacional (OAN)
E. Gonzalez-Alfonso
Universidad de Alcala
T. R. Greve
Danmarks Tekniske Universitet (DTU)
University College London (UCL)
C. Henkel
Max-Planck-Gesellschaft
King Abdulaziz University
M. Imanishi
National Astronomical Observatory of Japan
T. Izumi
National Astronomical Observatory of Japan
J. G. Mangum
National Radio Astronomy Observatory
S. Martin
European Southern Observatory Santiago
Atacama Large Millimeter-submillimeter Array (ALMA)
G. Privon
University of Florida
K. Sakamoto
Academia Sinica
S. Veilleux
University of Maryland
P. van der Werf
Universiteit Leiden
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 623 A29Ämneskategorier
Astronomi, astrofysik och kosmologi
Atom- och molekylfysik och optik
Miljövetenskap
DOI
10.1051/0004-6361/201834586