2017/10/16 by Guinevere Kauffmann · 4 citations
Medicine · Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Astrophysics #Galaxies: Formation, Evolution, Phenomena #Galaxy #Luminosity #Luminous infrared galaxy #Medicine #Photometric redshift #Physics #Population #Radio galaxy #Redshift #Star formation #Stellar mass #Stellar population #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stx2703
published in Monthly Notices of the Royal Astronomical Society 473(4), 5210-5220 (Oxford University Press) · 12 pages, 15 figures, accepted in MNRAS
openalex publication_date 2017/10/16 · arxiv created 2017/11/02 · arxiv updated 2017/12/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The goal of this paper is to investigate the physical nature of galaxies in the redshift range 0.02 < z < 0.15 that have strong excess emission at mid-infrared wavelengths and to determine whether they host a population of accreting black holes that cannot be identified using optical emission lines. We show that at fixed stellar mass M* and Dn(4000), the distribution of [3.4]–[4.6] μm (Wide-field Infrared Survey Explorer, W1 − W2 band) colours is sharply peaked, with a long tail to much redder W1 − W2 colours. We introduce a procedure to pull out the red outlier population based on a combination of three stellar population diagnostics. When compared with optically selected active galactic nucleus (AGN), red outliers are more likely to be found in massive galaxies, and they tend to have lower stellar mass densities, younger stellar ages and higher dust content than optically selected AGN hosts. They are twice as likely to be detected at radio wavelengths. We examine W1 − W2 colour profiles for a subset of the nearest, reddest outliers and find that most are not centrally peaked, indicating that the hot dust emission is spread throughout the galaxy. We find that radio luminosity is the quantity that is most predictive of a redder central W1 − W2 colour. Radio-loud galaxies with centrally concentrated hot dust emission are almost always morphologically disturbed, with compact, unresolved emission at 1.4 GHz. The 80 per cent of such systems are identifiable as AGN using optical emission line diagnostics.