Data from : The SAMI Galaxy Survey: Quenching of Star Formation in Clusters I. Transition Galaxies

Full description

We use integral-field spectroscopy from the SAMI Galaxy Survey to identify galaxies that show evidence of recent quenching of star formation. The galaxies exhibit strong Balmer absorption in the absence of ongoing star formation in more than 10% of their spectra within the SAMI field of view. These {{H}}δ -strong (HDS) galaxies (HDSGs) are rare, making up only ∼2% (25/1220) of galaxies with stellar mass {log}({M}* /{M}⊙ ) > 10. The HDSGs make up a significant fraction of nonpassive cluster galaxies (15%; 17/115) and a smaller fraction (2.0%; 8/387) of the nonpassive population in low-density environments. The majority (9/17) of cluster HDSGs show evidence of star formation at their centers, with the HDS regions found in the outer parts of the galaxy. Conversely, the HDS signal is more evenly spread across the galaxy for the majority (6/8) of HDSGs in low-density environments and is often associated with emission lines that are not due to star formation. We investigate the location of the HDSGs in the clusters, finding that they are exclusively within 0.6R 200 of the cluster center and have a significantly higher velocity dispersion relative to the cluster population. Comparing their distribution in projected phase space to those derived from cosmological simulations indicates that the cluster HDSGs are consistent with an infalling population that has entered the central 0.5r 200,3D cluster region within the last ∼1 Gyr. In the eight of nine cluster HDSGs with central star formation, the extent of star formation is consistent with that expected of outside-in quenching by ram pressure stripping. Our results indicate that the cluster HDSGs are currently being quenched by ram pressure stripping on their first passage through the cluster.

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External Organisations
University of Waterloo; Australian Astronomical Observatory; Macquarie University; Christ University, Bangalore; Durham University; University of Sydney; Western Sydney University; ARC Centre of Excellence for All-sky Astrophysics; ARC Centre of Excellence for Astrophysics in Three Dimensions (ASTRO3D); University of California Berkeley; University of New South Wales; Swinburne University of Technology; University of Bristol; ARC Australian Research Council; Australian National University; Sydney Institute for Astronomy; Australian Astronomical Optics; California Institute of Technology; University of Toledo; NASA, National Aeronautics & Space Administration (NASA), Armstrong Flight Res Ctr, SOFIA Operat Ctr, USRA; NASA Ames Research Center

Associated Persons
Dan Taranu (Creator)Matt S. Owers (Creator); Michael J. Hudson (Creator); Kyle A. Oman (Creator); Joss Bland-Hawthorn (Creator); Sarah Brough (Creator); Julia J. Bryant (Creator); Warrick J. Couch (Creator); Scott M. Croom (Creator); Jesse Van De Sande (Creator); Christoph Federrath (Creator); Andrew M. Hopkins (Creator); Jon S. Lawrence (Creator); Nuria P F Lorente (Creator); Richard M. McDermid (Creator); Anne M. Medling (Creator); Samuel N. Richards (Creator); Nicholas Scott (Creator)