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Title: CATCHING QUENCHING GALAXIES: THE NATURE OF THE WISE INFRARED TRANSITION ZONE

We present the discovery of a prominent bifurcation between early-type galaxies and late-type galaxies, in [4.6]-[12] μm colors from the Wide Field Infrared Survey Explorer (WISE). We then use an emission-line diagnostic comparison sample to explore the nature of objects found both within and near the edges of this WISE infrared transition zone (IRTZ). We hypothesize that this bifurcation might be due to the presence of hot dust and polyaromatic hydrocarbon (PAH) emission features in late-type galaxies. Using a sample of galaxies selected through the Shocked Poststarburst Galaxy Survey (SPOGS), we are able to identify galaxies with strong Balmer absorption (EW(Hδ) > 5 Å) as well as emission lines inconsistent with star formation (deemed SPOG candidates, or SPOGs*) that lie within the optical green valley. Seyferts and low-ionization nuclear emission line regions, whose u – r colors tend to be red, are strongly represented within IRTZ, whereas SPOGs* tend to sit near the star-forming edge. Although active galactic nuclei are well represented in the IRTZ, we argue that the dominant IRTZ population is composed of galaxies that are in late stages of transitioning across the optical green valley, shedding the last of their remnant interstellar media.
Authors:
; ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6]
  1. Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States)
  2. Department of Astronomy, Faculty of Physical and Mathematical Sciences, Universidad de Concepción, Casilla 160-C, Concepción (Chile)
  3. Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston, ACT 2611 (Australia)
  4. National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States)
  5. Departamento de Física Teórica y del Cosmos, Universidad de Granada, Granada (Spain)
  6. Physics Department, New Mexico Tech, Socorro, NM 87801 (United States)
Publication Date:
OSTI Identifier:
22364935
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 794; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; COLOR; COMPARATIVE EVALUATIONS; COSMIC DUST; EMISSION; GALACTIC EVOLUTION; GALAXIES; GALAXY NUCLEI; INFRARED SURVEYS; POLYCYCLIC AROMATIC HYDROCARBONS; QUENCHING; STARS