Journal Article

EVN observations of the farthest and brightest ULIRGs in the local Universe: the case of IRAS 23365+3604

Cristina Romero-Cañizales, Miguel Ángel Pérez-Torres and Antxon Alberdi

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 422, issue 1, pages 510-520
Published in print May 2012 | ISSN: 0035-8711
Published online April 2012 | e-ISSN: 1365-2966 | DOI:
EVN observations of the farthest and brightest ULIRGs in the local Universe: the case of IRAS 23365+3604

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We present high-resolution, high-sensitivity radio images of the ultra-luminous infrared galaxy (ULIRG) IRAS 23365+3604. We performed contemporaneous observations at 1.7 and 5.0 GHz, in three epochs separated by 1 year from each other, with the European Very Long Baseline Interferometry (VLBI) Network (EVN). We also present complementary Multi-Element Radio Linked Interferometry Network (MERLIN) at 1.6 and 5.0 GHz, and archival Very Large Array data, taken at 1.4 and 4.9 GHz. We find that the emission at ∼5.0 GHz remains quite compact as seen at different resolutions, whereas at ∼1.7 GHz, high-resolution imaging reveals some extended structure. The nuclear region has an approximate linear size of 200 pc and shows the presence of two main emission components: (i) one with a composite spectrum due to ongoing non-thermal activity (probably due to recently exploded supernovae and the presence of an active galactic nucleus), and (ii) the other with a steep spectrum, likely dominated by an old population of radio emitters, such as supernova remnants. Radiative losses are important, so re-acceleration or replenishment of new electrons is necessary. We estimate a magnetic field strength of ∼ 18 μG at galactic and ∼ 175 μG at nuclear scales, which are typical for galaxies in advanced mergers.

Keywords: galaxies: individual: IRAS 23365+3604; galaxies: starburst; radio continuum: general

Journal Article.  8244 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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