2001/04/18 by J. Cui, Jun Cui, X. -Y. Xia +7 · 7 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.1086/321127
38 pages, 21 figures, to be published in AJ
arxiv created 2001/04/18 · openalex publication_date 2001/07/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We perform photometric measurements on a large HST snapshot imaging survey sample of 97 ultraluminous infrared galaxies (ULIRGs). We select putative nuclei from bright clumps in all the sample targets, mainly based on a quantitative criterion of I -band luminosity as well as the global and local morphological information. All the sources are then classified into three categories with multiple, double, and single nucleus/nuclei. 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 AGN fraction increases from multiple (36%) to double (65%) and then to single (80%) 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 indicates that active galactic nuclei tend to appear at final merging stage. For multiple/double nuclei galaxies, we also find a high fraction of very close nucleus pairs (e.g., 3/4 for those separated by less than 5 kpc). This strengthens the conclusion that systems at late merging phase preferentially host ULIRGs.