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An optical study of the possible proto-starburst galaxy VII ZW 31

Djorgovski, S. and de Carvalho, R. R. and Thompson, D. J. (1990) An optical study of the possible proto-starburst galaxy VII ZW 31. Astronomical Journal, 99 (5). pp. 1414-1420. ISSN 0004-6256. doi:10.1086/115424.

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We present an optical imaging and spectroscopic study of an ultraluminous, gas-rich Infrared Astronomical Satellite (IRAS) galaxy, VII Zw 31. Sage and Solomon proposed earlier that this object may be interpreted as a protogalactic disk at low redshift, on account of its large mass fraction of molecular gas. Our data suggest that the object is a merger-induced starburst, and in that respect similar to many other ultraluminous IRAS galaxies. Asymmetries and distortions are seen in the visible light, and a prominent dust lane is detected near the nucleus. The spectra show strong, low-ionization line emission, consistent with photoionization by young stars, and substantial internal extinction. Absorption spectra suggest a presence of both young and old stellar populations. We interpret the object as an old galaxy, rejuvenated by a recent starburst. Since the large molecular gas content (~ 50% of the total mass) is the main distinguishing characteristic of this object, the starburst must be just in its initial stages. VII Zw 31 may thus be a low-redshift analog of at least some protogalaxies at large redshifts.

Item Type:Article
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URLURL TypeDescription
Djorgovski, S.0000-0002-0603-3087
de Carvalho, R. R.0000-0002-1283-3363
Additional Information:© 1990 American Astronomical Society. Provided by the NASA Astrophysics Data System. Received 15 November 1989; revised 19 January 1990. We would like to thank the staff of Palomar Observatory for their help during our observing runs, and in particular to Juan Carrasco, Dave Tennant, John Henning, and Skip Staples, and to Helen Johnston for assistance during the observations. We also thank Dr. Gustavo Bruzual for providing us with the latest version of his population synthesis code. We thank Nick Weir for his help in data reductions, and the careful reading of the manuscript. This work was supported in part by the Alfred P. Sloan Foundation and by California Institute of Technology (S.D.), and by a Caltech graduate fellowship (D.J.T.) R.R.dC. is on leave of absence from Observatorio Nacional, CNPq, Rio de Janeiro, Brazil.
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Alfred P. Sloan FoundationUNSPECIFIED
Issue or Number:5
Record Number:CaltechAUTHORS:20190822-082453577
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98094
Deposited By: Tony Diaz
Deposited On:22 Aug 2019 16:16
Last Modified:16 Nov 2021 17:36

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