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NGC 5291: Implications for the Formation of Dwarf GalaxiesThe possible formation and evolution of dwarf irregular galaxies from material derived from perturbed evolved galaxies is addressed via an H I study of a likely example, the peculiar system NGC 5291. This system, located in the western outskirts of the cluster Abell 3574, contains the lenticular galaxy NGC 5291 which is in close proximity to a disturbed companion and is flanked by an extensive complex of numerous knots extending roughly 4 min north and 4 min south of the galaxy. In an initial optical and radio study, Longmore et al. (1979, MNRAS, 188, 285) showed that these knots have the spectra of vigorous star-forming regions, and suggested that some may in fact be young dwarf irregular galaxies. High resolution 21-cm line observations taken with the VLA are presented here and reveal that the H I distribution associated with this system encompasses not only the entire N-S complex of optical knots, but also forms an incomplete ring or tail that extends approximately 3 min to the west. The H I associated with NGC 5291 itself shows a high velocity range; the Seashell is not detected. The formation mechanism for this unusual system is unclear and two models - a large, low-luminosity ram-swept disk, and a ram-swept interaction-are discussed. The H I in the system contains numerous concentrations, mostly along the N-S arc of the star-forming complexes, which generally coincide with one or more optical knots; the larger H I features contain several x 10(exp 9) solar mass of gas. Each of the knots is compared to a set of criteria designed to determine if these objects are bound against their own internal kinetic energy and are tidally stable relative to the host galaxy. An analysis of the properties of the H I concentrations surrounding the optical star-forming complexes indicates that at least the largest of these is a bound system; it also possesses a stellar component. It is suggested that this object is a genuinely young dwarf irregular galaxy that has evolved from the material associated with the system and that this entire complex contains several proto- or young dwarf irregular galaxies in various stages of development. We are therefore witnessing the early evolution of a number of genuinely young galaxies. Given the evident importance of the NGC 5291 system as a 'nursery' for young galaxies, careful modeling is required if we are to understand this remarkable galaxy.
Document ID
19980038070
Acquisition Source
Headquarters
Document Type
Contractor Report (CR)
External Source(s)
Authors
Malphrus, Benjamin K.
(Morehead State Univ. KY United States)
Simpson, Caroline E.
(Florida International Univ. Miami, FL United States)
Gottesman, S. T.
(Florida Univ. Gainesville, FL United States)
Hawarden, Timothy G.
(Joint Astronomy Centre Hilo, HI United States)
Date Acquired
September 6, 2013
Publication Date
October 1, 1997
Publication Information
Publication: The Astronomical Journal
Publisher: American Astronomical Society
Volume: 114
Issue: 4
ISSN: 0004-6256
Subject Category
Astrophysics
Report/Patent Number
NAS 1.26:207124
NASA/CR-97-207124
Funding Number(s)
CONTRACT_GRANT: NAGw-2166
Distribution Limits
Public
Copyright
Public Use Permitted.
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