Star formation activities in early-type brightest cluster galaxies

Abstract

We identify a total of 120 early-type Brightest Cluster Galaxies (BCGs) at 0.1<z<0.4 in two recent large cluster catalogues selected from the Sloan Digital Sky Survey (SDSS). They are selected with strong emission lines in their optical spectra, with both H{\alpha} and [O II]{\lambda}3727 line emission, which indicates significant ongoing star formation. They constitute about ~ 0.5% of the largest, optically-selected, low-redshift BCG sample, and the fraction is a strong function of cluster richness. Their star formation history can be well described by a recent minor and short starburst superimposed on an old stellar component, with the recent episode of star formation contributing on average only less than 1 percent of the total stellar mass. We show that the more massive star-forming BCGs in richer clusters tend to have higher star formation rate (SFR) and specific SFR (SFR per unit galaxy stellar mass). We also compare their statistical properties with a control sample selected from X-ray luminous clusters, and show that the fraction of star-forming BCGs in X-ray luminous clusters is almost one order of magnitude larger than that in optically-selected clusters. BCGs with star formation in cooling flow clusters usually have very flat optical spectra and show the most active star formation, which may be connected with cooling flows.Comment: 15 pages, 10 figures and 2 tables, accepted for publication in MNRA

The accretion histories of brightest cluster galaxies from their stellar population gradients

“…Furthermore, some BCGs show low levels of star formation in the local Universe (e.g. Liu et al 2012;Oliva-Altamirano et al 2014;Fraser-McKelvie et al 2014). This is consistent with the hypothesis that BCGs have complex accretion scenarios.…”

Rhapsody-G simulations I: the cool cores, hot gas and stellar content of massive galaxy clusters

“…In addition, we show the star formation rates determined by Liu et al (2012) for a sample of central cluster galaxies from SDSS, and those of McDonald et al (2015) for BCGs of SPT clusters. When comparing with the limit below Figure 11.…”

“…Galaxies with no detectable star formation in the previous 500 Myr have been assigned random values between 10 −3 and 10 −2 M /yr. For comparison, the main sequence of star forming galaxies in SDSS from Woo et al (2013) (solid black line) and the division between star-forming and quenched galaxies (black dotted) along with the OII-derived star formation rates for the BCG samples of Liu et al (2012) and the UV estimates of McDonald et al (2015) are shown (note that for the latter, data points with only long lower error bars are upper limits).…”

Red but not dead: unveiling the star-forming far-infrared spectral energy distribution of SpARCS brightest cluster galaxies at 0 < z < 1.8

“…This simple parameter has been shown to robustly identify AGN-driven radio activity as being characterised by a q24 value of less than −0.16 (e.g., Norris et al 2006;Middelberg et al 2008;Mao et al 2012), and therefore relative radioloudness, largely independent of the redshift of the emission or the host galaxy contribution (Appleton et al 2004;Wilkes et al 2009;Sargent et al 2010;Mao et al 2011;Hales et al 2014). While a single-band radio analysis does not afford a complete characterisation of the radio properties of the BCGs in our sample -e.g., to determine the number, character, physical size, or age of the distinct radio components which may be associated with the BCGs (Hogan et al 2012) -the q24 parameter offers an additional, reliable means by which to determine the fraction of BCGs in our sample with a dominant AGN.…”