An infrared survey of brightest cluster galaxies. I

We report on an imaging survey with the Spitzer Space Telescope of 62 brightest cluster galaxies with optical line emission. These galaxies are located in the cores of X-ray luminous clusters selected from the ROSAT All-Sky Survey. We find that about half of these sources have a sign of excess infrared emission; 22 objects out of 62 are detected at 70 mu m, 18 have 8/ 5.8 mu m flux ratios above 1.0 and 28 have 24/8 mu m flux ratios above 1.0. Altogether 35 of 62 objects in our survey exhibit at least one of these signs of infrared excess. Four galaxies with infrared excesses have a 4.5/ 3.6 mu mflux ratio indicating the presence of hot dust, and/ or an unresolved nucleus at 8 mu m. Three of these have high measured [O-III](5007 angstrom)/H beta flux ratios suggesting that these four, Abell 1068, Abell 2146, Zwicky 2089, and R0821+ 07, host dusty active galactic nuclei (AGNs). Nine objects (including the four hosting dusty AGNs) have infrared luminosities greater than 10(11) L (circle dot) and so can be classified as luminous infrared galaxies (LIRGs). Excluding the four systems hosting dusty AGNs, the excess mid-infrared emission in the remaining brightest cluster galaxies is likely related to star formation.