Shocked POststarburst Galaxy Survey. II. The Molecular Gas Content and Properties of a Subset of SPOGs

August 2016 • 2016ApJ...827..106A

Authors • Alatalo, Katherine • Lisenfeld, Ute • Lanz, Lauranne • Appleton, Philip N. • Ardila, Felipe • Cales, Sabrina L. • Kewley, Lisa J. • Lacy, Mark • Medling, Anne M. • Nyland, Kristina • Rich, Jeffrey A. • Urry, C. Meg

Abstract • We present CO(1-0) observations of objects within the Shocked POststarburst Galaxy Survey taken with the Institut de Radioastronomie Millimétrique 30 m single dish and the Combined Array for Research for Millimeter Astronomy interferometer. Shocked poststarburst galaxies (SPOGs) represent a transitioning population of galaxies, with deep Balmer absorption ({{EW}}_{{H}δ }\gt 5 {\mathring{{A}}} ), consistent with an intermediate-age (A-star) stellar population, and ionized gas line ratios inconsistent with pure star formation. The CO(1-0) subsample was selected from SPOGs detected by the Wide-field Infrared Survey Explorer with 22 μm flux detected at a signal-to-noise ratio (S/N) > 3. Of the 52 objects observed in CO(1-0), 47 are detected with S/N > 3. A large fraction (37%-46% ± 7%) of our CO-SPOG sample were visually classified as morphologically disrupted. The H₂ masses detected were between {10}^8.7-10.8 {M}_⊙, consistent with the gas masses found in normal galaxies, though approximately an order of magnitude larger than the range seen in poststarburst galaxies. When comparing the 22 μm and CO(1-0) fluxes, SPOGs diverge from the normal star-forming relation, having 22 μm fluxes in excess of the relation by a factor of < {ɛ }_{{MIR}}> ={4.91}_-0.39^+0.42, suggestive of the presence of active galactic nuclei (AGNs). The Na I D characteristics of CO-SPOGs show that it is likely that many of these objects host interstellar winds. Objects with large Na I D enhancements also tend to emit in the radio, suggesting possible AGN driving of neutral winds.

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Phil Appleton

Senior Scientist