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Published August 20, 2003 | Erratum + Accepted Version + Published
Journal Article Open

Nascent Starbursts in Synchrotron-deficient Galaxies with Hot Dust

Abstract

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.

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

Attached Files

Published - Roussel_2003_ApJ_593_733.pdf

Accepted Version - 0305046.pdf

Erratum - pdf

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Additional details

Created:
August 22, 2023
Modified:
October 23, 2023