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Nascent Starbursts in Synchrotron-deficient Galaxies with Hot Dust

Roussel, H. and Helou, G. and Beck, R. and Condon, J. J. and Bosma, A. and Matthews, K. and Jarrett, T. H. (2003) Nascent Starbursts in Synchrotron-deficient Galaxies with Hot Dust. Astrophysical Journal, 593 (2). pp. 733-759. ISSN 0004-637X.

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Three nearby galaxies that have abnormally high infrared-to-radio continuum ratios, NGC 1377, IC 1953, and NGC 4491, are investigated with a view to understanding the physical origin of their peculiarity. We review the existing data and present new radio continuum measurements along with near-infrared integral-field spectroscopy and molecular gas observations. The three galaxies have low luminosities but starburst-like infrared colors; in NGC 1377, no synchrotron emission is detected at any wavelength; in IC 1953, the observed synchrotron component is attributable to the spiral disk alone and is lacking in the central regions; and the radio spectrum of NGC 4491 is unusually flat. We also compare and contrast them with NGC 4418, a heavily extinguished galaxy that shares some attributes with them. After examining various scenarios, we conclude that these galaxies are most likely observed within a few megayears of the onset of an intense star formation episode after being quiescent for at least ≈100 Myr. This starburst, while heating the dust, has not produced optical signatures or a normal amount of cosmic rays yet. We briefly discuss the statistics of such galaxies and what they imply for star formation surveys.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Roussel, H.0000-0001-5617-7129
Helou, G.0000-0003-3367-3415
Condon, J. J.0000-0003-4724-1939
Jarrett, T. H.0000-0002-4939-734X
Additional Information:© 2003. The American Astronomical Society. Received 2002 December 17; accepted 2003 May 2. We are grateful to Antonio García-Barreto for providing us his H_α+[N II] and I-band maps of IC 1953, to Sangeeta Malhotra for mentioning the peculiar infrared properties of NGC 4418, thereby arousing our curiosity, to the persons who assisted us in the observations at Effelsberg, Palomar, and La Silla, and to James Brauher for communicating us some fluxes in advance of publication. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and IPAC/Caltech, funded by NASA and the National Science Foundation. The ISOCAM data presented in this paper were analyzed using and adapting the CIA package, a joint development by the ESA Astrophysics Division and the ISOCAM Consortium. This research also benefited from the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory of Caltech.
Errata:H. Roussel et al 2004 ApJ 601 1160
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Subject Keywords:galaxies: starburst; galaxies: individual (IC 1953 NGC 1377 NGC 4418 NGC 4491) ; infrared: galaxies; radio continuum: galaxies; supernova remnants
Issue or Number:2
Record Number:CaltechAUTHORS:20201016-145652458
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Official Citation:H. Roussel et al 2003 ApJ 593 733
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106122
Deposited By: George Porter
Deposited On:16 Oct 2020 22:44
Last Modified:16 Oct 2020 22:44

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