Star formation trends in the unrelaxed, post-merger cluster A2255

K. D. Tyler, L. Bai, G. H. Rieke

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


The effects of dense environments on normal field galaxies are still up for debate despite much study since Abell published his catalog of nearby clusters in 1958. There are changes in color, morphology, and star formation properties when galaxies fall into groups and clusters, but the specifics of how and where these modifications occur are not fully understood. To look for answers, we focused on star-forming galaxies in A2255, an unrelaxed cluster thought to have recently experienced a merger with another cluster or large group. We used Hα, MIPS 24 μm, and WISE 22 μm to estimate total star formation rates (SFRs) and Sloan Digital Sky Survey photometry to find stellar masses (M) for galaxies out to ∼5 r200. We compared the star-forming cluster galaxies with the field SFR-mass distribution and found no enhancement or suppression of star formation in currently star-forming galaxies of high mass (log (M/M) ≳ 10). This conclusion holds out to very large distances from the cluster center. However, the core (rproj< 3 Mpc) has a much lower fraction of star-forming galaxies than anywhere else in the cluster. These results indicate that for the mass range studied here, the majority of the star formation suppression occurs in the core on relatively short timescales, without any enhancement prior to entering the central region. If any significant enhancement or quenching of star formation occurs, it will be in galaxies of lower mass (log (M/M) < 10).

Original languageEnglish (US)
Article number31
JournalAstrophysical Journal
Issue number1
StatePublished - Oct 10 2014


  • galaxies: clusters: individual (A2255)
  • galaxies: evolution
  • galaxies: photometry
  • galaxies: star formation
  • infrared: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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