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Tidal Remnants and Intergalactic H II Regions

Published online by Cambridge University Press:  26 May 2016

Tom Oosterloo ,
Raffaella Morganti ,
Elaine M. Sadler ,
Annette Ferguson ,
Thijs van der Hulst  and
Helmut Jerjen
Tom Oosterloo
Affiliation:
Netherlands Foundation for Research in Astronomy, Dwingeloo, The Netherlands
Raffaella Morganti
Affiliation:
Netherlands Foundation for Research in Astronomy, Dwingeloo, The Netherlands
Elaine M. Sadler
Affiliation:
School of Physics, University of Sydney, NSW 2006, Australia
Annette Ferguson
Affiliation:
Max-Planck Institute für Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching, Germany
Thijs van der Hulst
Affiliation:
Kapteyn Astronomical Institute, RuG, Landleven 12, 9747 AD, Groningen, The Netherlands
Helmut Jerjen
Affiliation:
Research School of Astronomy & Astrophysics, Australian National University, ACT 2611, Canberra, Australia

Abstract

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We report the discovery of two small intergalactic H II regions in the loose group of galaxies around the field elliptical NGC 1490. The H II regions are located at least 100 kpc from any optical galaxy but are associated with a number of large H I clouds that are lying along an arc 500 kpc in length and that have no optical counterpart on the Digital Sky Survey. The sum of the H I masses of the clouds is almost 1010M⊙ and the largest H I cloud is about 100 kpc in size. Deep optical imaging reveals a very low surface brightness counterpart to this largest H I cloud, making this one of the H I richest optical galaxies known (MHI/LV ~ 200). Spectroscopy of the H II regions indicates that the abundance in these H II regions is only slightly sub-solar, excluding a primordial origin of the H I clouds. The H I clouds are perhaps remnants resulting from the tidal disruption of a reasonably sized galaxy, probably quite some time ago, by the loose group to which NGC 1490 belongs. Alternatively, they are remnants of the merger that created the field elliptical NGC 1490. The isolated H II regions show that star formation on a very small scale can occur in intergalactic space in gas drawn from galaxies by tidal interactions. Many such intergalactic small star formation regions may exist near tidally interacting galaxies.

Type
Part 4. Recycling
Information
Symposium - International Astronomical Union , Volume 217: Recycling Intergalactic and Interslettar Matter , 2004 , pp. 486 - 491
Copyright
Copyright © Astronomical Society of the Pacific 2004 

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