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Published October 10, 2014 | Published + Submitted
Journal Article Open

Catching Quenching Galaxies: The Nature of the WISE Infrared Transition Zone

Abstract

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.

Additional Information

© 2014 The American Astronomical Society. Received 2014 August 7; accepted 2014 September 6; published 2014 September 30. K.A. thanks Kevin Schawinski for giving full access to his early- and late-type galaxy sample, as well as Theodoros Bitsakis and Patrick Ogle for insightful discussions, Michelle Cluver and Roc Cutri for WISE advice, and finally the referee for an informative and insightful report that improved the Letter. K.A. is supported by funding through Herschel, a European Space Agency Cornerstone Mission with significant participation by NASA, through an award issued by JPL/Caltech. K.N. is supported by NSF grant 1109803. S.L.C. was supported by ALMA-CONICYT program 31110020. U.L. acknowledges support by the research projects AYA2011-24728 from the Spanish Ministerio de Ciencia y Educación and the Junta de Andalucía (Spain) grants FQM108. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. This research has made use of the Sloan Digital Sky Survey.

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Published - Alatalo_2014_ApJL_794_L13.pdf

Submitted - 1409.2489v1.pdf

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August 20, 2023
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