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Merging Galaxies with Multiple Nuclei from HST ULIRGs Snapshot Survey

Published online by Cambridge University Press:  13 May 2016

J. Cui
Affiliation:
Beijing Astronomical Observatory and Beijing Astronomical Center of the National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, Beijing 100012, China
X.-Y. Xia
Affiliation:
Beijing Astronomical Observatory and Beijing Astronomical Center of the National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, Beijing 100012, China Dept. of Physics, Tianjin Normal University, Tianjin 300074, China
Z.-G. Deng
Affiliation:
Beijing Astronomical Observatory and Beijing Astronomical Center of the National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, Beijing 100012, China Dept. of Physics, Graduate School, Chinese Academy of Sciences, Beijing 100039, China
S. Mao
Affiliation:
Jodrell Bank Observatory, University of Manchester, Macclesfield, Cheshire SK11 9DL, UK
Z.-L. Zou
Affiliation:
Beijing Astronomical Observatory and Beijing Astronomical Center of the National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, Beijing 100012, China

Abstract

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We perform photometric measurements on a large HST snapshot imaging survey sample of 97 ultraluminous infrared galaxies (ULIRGs). We classify all the sources into three categories with multiple, double and single nucleus/nuclei, mainly based on a quantitative criterion of I-band luminosity. The resultant fractions of multiple, double and single nucleus/nuclei ULIRGs are 18%, 39% and 43%, respectively. This supports the multiple merger scenario as a possible origin of ULIRGs, in addition to the commonly-accepted pair merger model. Further statistical studies indicate that the fraction of AGN increases from multiple (18%) to double (39%) and then to single (43%) nucleus/nuclei ULIRGs. For the single nucleus category, there is a high luminosity tail in the luminosity distribution, which corresponds to a Seyfert 1/QSO excess. This supports the statement that active galactic nuclei tend to appear at final merging stage. For multiple and double mergers, we also find a considerably high fraction of very close nucleus pairs (e.g., 2/3 for those separated by less than 5 kpc). This strengthens the conclusion that systems at late merging phase preferentially host ULIRGs.

Type
The Inner Regions of Galaxies
Copyright
Copyright © Astronomical Society of the Pacific 2001 

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