We present UV broadband photometry and optical emission-line measurements for a sample of 32 Brightest Cluster Galaxies ( BCGs ) in clusters of the Representative XMM-Newton Cluster Structure Survey ( REXCESS ) with z = 0.06 - 0.18 .
The REXCESS clusters , chosen to study scaling relations in clusters of galaxies , have X-ray measurements of high quality .
The trends of star formation and BCG colors with BCG and host properties can be investigated with this sample .
The UV photometry comes from the XMM Optical Monitor , supplemented by existing archival GALEX photometry .
We detected H \alpha and forbidden line emission in 7 ( 22 % ) of these BCGs , in optical spectra obtained using the SOAR Goodman Spectrograph .
All of these emission-line BCGs occupy clusters classified as cool cores based on the central cooling time in the cluster core , for an emission-line incidence rate of 70 % for BCGs in REXCESS cool core clusters .
Significant correlations between the H \alpha equivalent widths , excess UV production in the BCG , and the presence of dense , X-ray bright intracluster gas with a short cooling time are seen , including the fact that all of the H \alpha emitters inhabit systems with short central cooling times and high central ICM densities .
Estimates of the star formation rates based on H \alpha and UV excesses are consistent with each other in these 7 systems , ranging from 0.1 - 8 solar masses per year .
The incidence of emission-line BCGs in the REXCESS sample is intermediate , somewhat lower than in other X-ray selected samples ( \sim 35 \% ) , and somewhat higher than but statistically consistent with optically selected , slightly lower redshift BCG samples ( \sim 10 - 15 \% ) .
The UV-optical colors ( UVW1-R \sim 4.7 \pm 0.3 ) of REXCESS BCGs without strong optical emission lines are consistent with those predicted from templates and observations of ellipticals dominated by old stellar populations .
We see no trend in UV-optical colors with optical luminosity , R - K color , X-ray temperature , redshift , or offset between X-ray centroid and X-ray peak ( \langle w \rangle ) .
The lack of such trends in these massive galaxies , particularly the ones lacking emission lines , suggests that the proportion of UV-emitting ( 200-300 nm ) stars is insensitive to galaxy mass , cluster mass , cluster relaxation , and recent evolution , over the range of this sample .