CON-quest: II. Spatially and spectrally resolved HCN/HCO+ line ratios in local luminous and ultraluminous infrared galaxies
Artikel i vetenskaplig tidskrift, 2024

Context. Nuclear regions of ultraluminous and luminous infrared galaxies (U/LIRGs) are powered by starbursts and/or active galactic nuclei (AGNs). These regions are often obscured by extremely high columns of gas and dust. Molecular lines in the submillimeter windows have the potential to determine the physical conditions of these compact obscured nuclei (CONs).
Aims. We aim to reveal the distributions of HCN and HCO+ emission in local U/LIRGs and investigate whether and how they are related to galaxy properties. Methods. Using the Atacama Large Millimeter/submillimeter Array (ALMA), we have conducted sensitive observations of the HCN J = 3-2 and HCO+J = 3-2 lines toward 23 U/LIRGs in the local Universe (z < 0.07) with a spatial resolution of ~0.3″ ( ~50-400 pc).
Results. We detected both HCN and HCO+ in 21 galaxies, only HCN in one galaxy, and neither in one galaxy. The global HCN/HCO+ line ratios, averaged over scales of ~0.5-4 kpc, range from 0.4 to 2.3, with an unweighted mean of 1.1. These line ratios appear to have no systematic trend with bolometric AGN luminosity or star formation rate. The line ratio varies with position and velocity within each galaxy, with an average interquartile range of 0.38 on a spaxel-by-spaxel basis. In eight out of ten galaxies known to have outflows and/or inflows, we found spatially and kinematically symmetric structures of high line ratios. These structures appear as a collimated bicone in two galaxies and as a thin spherical shell in six galaxies.
Conclusions. Non-LTE analysis suggests that the high HCN/HCO+ line ratio in outflows is predominantly influenced by the abundance ratio. Chemical model calculations indicate that the enhancement of HCN abundance in outflows is likely due to high-temperature chemistry triggered by shock heating. These results imply that the HCN/HCO+ line ratio can aid in identifying the outflow geometry when the shock velocity of the outflows is sufficiently high to heat the gas.

ISM: molecules

Galaxies: ISM

Galaxies: nuclei

ISM: jets and outflows

Galaxies: evolution


Y. Nishimura

University of Tokyo

National Astronomical Observatory of Japan

Susanne Aalto

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik

Mark Gorski

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik

Sabine König

Chalmers, Rymd-, geo- och miljövetenskap, Onsala rymdobservatorium

Kyoko Onishi

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik

Clare Wethers

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik

Chentao Yang

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik

Loreto Barcos-Munoz

National Radio Astronomy Observatory

F. Combes

Observatoire de Paris

T. Diaz-Santos

European University Cyprus

Foundation for Research and Technology-Hellas (FORTH)

J. S. Gallagher III

University of Wisconsin Madison

Macalester College

S. G. Burillo

Observatorio Astronómico Nacional (OAN)

E. Gonzalez-Alfonso

Universidad de Alcala

T. R. Greve

Danmarks Tekniske Universitet (DTU)

Niels Bohr Institute

N. Harada

The Graduate University for Advanced Studies (SOKENDAI)

National Astronomical Observatory of Japan

C. Henkel


King Abdulaziz University

M. Imanishi

National Astronomical Observatory of Japan

K. Kohno

University of Tokyo

S. T. Linden

University of Arizona

J. G. Mangum

National Radio Astronomy Observatory

S. Martin

European Southern Observatory Santiago

Atacama Large Millimeter-submillimeter Array (ALMA)

Sebastien Muller

Chalmers, Rymd-, geo- och miljövetenskap, Onsala rymdobservatorium

G. Privon

University of Virginia

National Radio Astronomy Observatory

College of Liberal Arts and Sciences

C. Ricci

Beijing University of Technology

Universidad Diego Portales

F. Stanley

Institut de Radioastronomie Millimétrique (IRAM)

P. van der Werf

Universiteit Leiden

Serena Viti

Universiteit Leiden

University College London (UCL)

Astronomy and Astrophysics

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

Vol. 686 A48

Exploring the Hidden Dusty Nuclei of Galaxies (HIDDeN)

Europeiska forskningsrådet (ERC) (789410), 2018-10-01 -- 2023-09-30.

Molekyler som Diagnostiska Redskap för Aktiva och Skymda Galaxer

Vetenskapsrådet (VR) (2011-4143), 2012-01-01 -- 2014-12-31.


Astronomi, astrofysik och kosmologi

Atom- och molekylfysik och optik



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