The opaque heart of the galaxy IC 860: Analogous protostellar, kinematics, morphology, and chemistry
Journal article, 2023

Compact Obscured Nuclei (CONs) account for a significant fraction of the population of luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs). These galaxy nuclei are compact, with radii of 10-100 pc, with large optical depths at submm and far-infrared wavelengths, and characterized by vibrationally excited HCN emission. It is not known what powers the large luminosities of the CON host galaxies because of the extreme optical depths towards their nuclei. CONs represent an extreme phase of nuclear growth, hiding either a rapidly accreting supermassive black hole or an abnormal mode of star formation. Regardless of their power source, the CONs allow us to investigate the processes of nuclear growth in galaxies. Here we apply principal component analysis (PCA) tomography to high-resolution (000:06) ALMA observations at frequencies 245 to 265 GHz of the nearby CON (59 Mpc) IC 860. PCA is a technique to unveil correlation in the data parameter space, and we apply it to explore the morphological and chemical properties of species in our dataset. The leading principal components reveal morphological features in molecular emission that suggest a rotating, infalling disk or envelope, and an outflow analogous to those seen in Galactic protostars. One particular molecule of astrochemical interest is methanimine (CH2NH), a precursor to glycine, three transitions of which have been detected towards IC 860.We estimate the average CH2NH column density towards the nucleus of IC 860 to be _1017cm2, with an abundance exceeding 108 relative to molecular hydrogen, using the rotation diagram method and non-LTE radiative transfer models. This CH2NH abundance is consistent with those found in hot cores of molecular clouds in the Milky Way. Our analysis suggests that CONs are an important stage of chemical evolution in galaxies, that are chemically and morphologically similar to Milky Way hot cores.

Galaxies: ISM

Galaxies: individual: IC860

Galaxies: evolution

Methods: statistical

ISM: molecules

ISM: jets and outflows

Author

Mark Gorski

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Susanne Aalto

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Sabine König

Chalmers, Space, Earth and Environment, Onsala Space Observatory

Clare Wethers

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Chentao Yang

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Sebastien Muller

Chalmers, Space, Earth and Environment, Onsala Space Observatory

Serena Viti

University College London (UCL)

Leiden University

John H Black

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Kyoko Onishi

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Mamiko Sato

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Astronomy and Astrophysics

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

Vol. 670 A70

Onsala space observatory infrastructure

Swedish Research Council (VR) (2017-00648), 2018-01-01 -- 2021-12-31.

Subject Categories

Astronomy, Astrophysics and Cosmology

Atom and Molecular Physics and Optics

Other Physics Topics

DOI

10.1051/0004-6361/202245166

More information

Latest update

2/20/2023