HST FUV Observations of Brightest Cluster Galaxies: The Role of Star
  Formation in Cooling Flows and BCG Evolution
  Quillen et al. and O'Dea et al. carried out a Spitzer study of a sample of 62
brightest cluster galaxies (BCGs) from the ROSAT Brightest Cluster Sample
chosen based on their elevated H-alpha flux. We present Hubble Space Telescope
Advanced Camera for Surveys (ACS) far ultraviolet (FUV) images of the Ly-alpha
and continuum emission of the luminous emission-line nebulae in 7 BCGs found to
have an infrared excess. We confirm that the BCGs are actively forming stars
suggesting that the IR excess seen in these BCGs is indeed associated with star
formation. The FUV continuum emission extends over a region of ~7-28 kpc
(largest linear size) and even larger in Ly-alpha. The young stellar population
required by the FUV observations would produce a significant fraction of the
ionizing photons required to power the emission line nebulae. Star formation
rates estimated from the FUV continuum range from ~3 to ~14 times lower than
those estimated from the IR, however both the Balmer decrement in the central
few arcseconds and detection of CO in most of these galaxies imply that there
are regions of high extinction that could have absorbed much of the FUV
continuum. Analysis of archival VLA observations reveals compact radio sources
in all 7 BCGs and kpc scale jets in Abell 1835 and RXJ 2129+00. The four
galaxies with archival deep Chandra observations exhibit asymmetric X-ray
emission, the peaks of which are offset from the center of the BCGs by ~10 kpc
on average. A low feedback state for the AGN could allow increased condensation
of the hot gas into the center of the galaxy and the feeding of star formation.
