2006/02/08 by K. Brand, Kate Brand, Arjun Dey +20 · 94 citations
Physics and Astronomy · #Active galactic nucleus #Astronomy #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Astrophysics #Flux (metallurgy) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Infrared #Luminous infrared galaxy #Physics #astro-ph
paper · pdf · doi:10.1086/503416
published in The Astrophysical Journal 644(1), 143-147 (IOP Publishing) · 6 pages, accepted for publication in ApJ
arxiv created 2006/02/08 · openalex publication_date 2006/06/10 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
We determine the contribution of AGN to the mid-IR emission of luminous infrared galaxies (LIRGs) at z > 0.6 by measuring the mid-IR dust continuum slope of 20,039 mid-IR sources. The 24 μm sources are selected from a Spitzer MIPS survey of the NOAO Deep Wide-Field Survey Boötes field and have corresponding 8 μm data from the IRAC Shallow Survey. There is a clear bimodal distribution in the 24 to 8 μm flux ratio. The X-ray-detected sources fall within the peak corresponding to a flat spectrum in ν f ν , implying that it is populated by AGN-dominated LIRGs, whereas the peak corresponding to a higher 24 to 8 μm flux ratio is likely due to LIRGs whose IR emission is powered by starbursts. The 24 μm emission is increasingly dominated by AGN at higher 24 μm flux densities ( f 24 ): the AGN fraction of the z > 0.6 sources increases from 9% at f 24 ≈ 0.35 mJy to 74% ± 20% at f 24 ≈ 3 mJy, in good agreement with model predictions. Deep 24 μm, small-area surveys, like GOODS, will be strongly dominated by starburst galaxies. AGN are responsible for ~3%-7% of the total 24 μm background.