An Origin of the Huge Far-Infrared Luminosity of Starburst Mergers

Open Access
Publisher Website
Google Scholar
Abstract
Recently Taniguchi and Ohyama found that the higher 12CO to 13CO integrated intensity ratios at a transition J=1-0, R=I(12CO)/I(13CO) 20, in a sample of starburst merging galaxies such as Arp 220 are mainly attributed to the depression of 13CO emission with respect to 12CO. Investigating the same sample of galaxies analyzed by Taniguchi and Ohyama, we find that there is a tight, almost linear correlation between the dust mass and 13CO luminosity. This implies that dust grains are also depressed in the high-R starburst mergers, leading to the higher dust temperature (Td) in them because of the relative increase in the radiation density. Nevertheless, the average dust mass (Md) of the high-R starburst mergers is significantly higher than that of non-high-R galaxies. This is naturally understood because the galaxy mergers could accumulate a lot of dust grains from their progenitor galaxies together with the supply of dust grains formed newly in the star-forming regions. Since L(FIR) ∝ MdT5d given the dust emissivity law Sν ∝ λ−1, the increases in both Md and Td explain well why the starburst mergers are so bright in the far-infrared. We discuss the important role that the superwind activity plays in destroying dust grains as well as dense gas clouds in the central region of mergers.
All Related Versions