Journal Article

Classical radio source propagating into outer H <span class="smallCaps">i</span> disc in NGC 3801

B. H. C. Emonts, C. Burnett, R. Morganti and C. Struve

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 421, issue 2, pages 1421-1430
Published in print April 2012 | ISSN: 0035-8711
Published online March 2012 | e-ISSN: 1365-2966 | DOI:
Classical radio source propagating into outer H i disc in NGC 3801

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We present observations of a large-scale disc of neutral hydrogen (H i) in the nearby Fanaroff–Riley type I (FR I) radio galaxy NGC 3801 with the Westerbork Synthesis Radio Telescope. The H i disc (34 kpc in diameter and with ) is aligned with the radio jet axis. This makes NGC 3801 an ideal system for investigating the evolution of a small radio source through its host galaxy’s cold interstellar medium (ISM). The large-scale H i disc is perpendicular to a known inner CO disc and dust lane. We argue that the formation history of the large-scale H i disc is in agreement with earlier speculation that NGC 3801 was involved in a past gas-rich galaxy–galaxy merger (although other formation histories are discussed). The fact that NGC 3801 is located in an environment of several H i-rich companions, and shows indications of ongoing interaction with the nearby companion NGC 3802, strengthens this possibility. The large amounts of ambient cold ISM, combined with X-ray results by Croston, Kraft & Hardcastle on the presence of overpressured radio jets and evidence for an obscuring torus, are properties that are generally not, or no longer, associated with more evolved FR I radio sources. We do show, however, that the H i properties of NGC 3801 are comparable to those of a significant fraction of nearby low-power compact radio sources, suggesting that studies of NGC 3801 may reveal important insight into a more general phase in the evolution of at least a significant fraction of nearby radio galaxies.

Keywords: galaxies: active; galaxies: evolution; galaxies: individual: NGC 3801; galaxies: interactions; galaxies: ISM; galaxies: jets

Journal Article.  6597 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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