Skip to main content

Research Repository

Advanced Search

The frequency of anomalously red galaxies in SDSS clusters

Shearman, O.; Pimbblet, K. A.


O. Shearman


We present a systematic photometric search for spectroscopically confirmed anomalously red galaxies members of 748 low redshift clusters between 0.03 < z < 0.17 from the SDSS-C4 cluster catalogue (Miller et al. 2005). For each cluster we spectroscopically determine cluster membership, construct a colour-magnitude diagram and fit the red sequence using a robust bi-weight fit.We define an “anomalously red galaxy” as having a (g− r) colour of greater than 3σ redward of the fitted cluster colour-magnitude relation.We find that of 7485 galaxies at r ≤ 17.77 in (g− r), 7 galaxies are anomalously red – 0.0935 per cent of all galaxies in our sample. We show that two of the red outliers are caused by red contamination from nearby sources and are therefore not intrinsically anomalous red. However, 5 have no underlying cause to be so red and we speculate that they may have a high internal dust content. These intrinsically red galaxies are rare – comprising no more than 0.0668 per cent of all cluster galaxies. Most are morphologically early type galaxies, with a few probable late type galaxies that are viewed edge-on and one low surface brightness late type. One of our anomalously red galaxies appears to be a dust-shrouded starburst and we speculate that this may be a unique galaxy amoungst this galaxy set.


Shearman, O., & Pimbblet, K. A. (2014). The frequency of anomalously red galaxies in SDSS clusters. Publications / Astronomical Society of Australia, 31, Article ARTN e038.

Journal Article Type Article
Acceptance Date Aug 30, 2014
Online Publication Date Sep 30, 2014
Publication Date Sep 30, 2014
Deposit Date Aug 28, 2015
Journal Publications of the Astronomical Society of Australia
Print ISSN 1323-3580
Electronic ISSN 1448-6083
Publisher Cambridge University Press
Peer Reviewed Peer Reviewed
Volume 31
Article Number ARTN e038
Keywords Galaxies -- clusters -- general, Galaxies -- elliptical and lenticular, cD, Galaxies -- photometry, Galaxies -- stellar content, Hertzsprung-Russell and C-M diagrams
Public URL
Publisher URL
Additional Information This is a description of an article which has been published in: Publications of the Astronomical Society of Australia, 2014, v.31.