Mid-infrared images of luminous infrared galaxies in a merging sequence

Chorng Yuan Hwang, K. Y. Lo, Yu Gao, Robert A. Gruendl, Nanyao Y. Lu

Research output: Contribution to journalArticlepeer-review


We report mid-infrared observations of several luminous infrared galaxies (LIGs) carried out with the Infrared Space Observatory. Our sample was chosen to represent different phases of a merger sequence of galaxy-galaxy interaction with special emphasis on early/intermediate stages of merging. The mid-infrared emission of these LIGs shows extended structures for the early and intermediate mergers, indicating that most of the mid-infrared luminosities are not from a central active galactic nucleus. Both the infrared hardness (indicated by the IRAS 12, 25, and 60 μm flux density ratios) and the peak-to-total flux density ratios of these LIGs increase as projected separation of these interacting galaxies become smaller, consistent with increasing star formation activities that are concentrated to a smaller area as the merging process advances. These observations provide among the first observational constraint of largely theoretically based scenarios.

Original languageEnglish (US)
Pages (from-to)L17-L20
JournalAstrophysical Journal
Issue number1 PART 2
StatePublished - Jan 20 1999


  • Galaxies: individual (Arp 302, NGC 6670, UGC 2369, NGC 7592, NGC 5256, Markarian 848, NGC 6090)
  • Galaxies: interactions
  • Galaxies: starburst
  • Infrared: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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