HST FUV Observations of Brightest Cluster Galaxies: The Role of Star Formation in Cooling Flows and BCG Evolution

resubmitting after changing targets as per approved change request. added 51 repeat of visit 1 after HOPR approval ----- Attempting Submission 1 (Tue May 08 17:22:48 GMT 2007) ----- Phase II Proposal 11230 (hst-spitzerII) successfully submitted. ----- Attempting Submission 2 (Fri Oct 05 15:13:47 GMT 2007) ----- ----- Attempting Submission 3 (Mon Dec 15 13:35:12 GMT 2008) ----- Assigned ID: 650 ----- Attempting Submission 1 (Sat Jan 27 00:32:42 GMT 2007) ----- Phase I Proposal 650 (hst-spitzer) successfully submitted. ----- Attempting Submission 3 (Sat Jan 27 00:44:29 GMT 2007) ----- Phase I Proposal 650 (hst-spitzer) successfully submitted. ----- Attempting Submission 4 (Thu Feb 01 17:01:26 GMT 2007) ----- Phase I Proposal 650 (hst-spitzer) successfully submitted. HST FUV Observations of Brightest Cluster Galaxies: The Role of Star Formation in Cooling Flows and BCG Evolution The intracluster medium (ICM) now appears to be a very dynamic place where heating and cooling processes vie for dominance and an uneasy equilibrium is maintained. Since these same processes may operate during the process of galaxy formation, the centers of clusters of galaxies provide low redshift laboratories for studying the critical processes involved in galaxy formation and black hole growth. At the present time, the main questions are (1) How much gas is cooling out of the ICM? (2) How much star formation is ongoing? (3) What is the impact of the gas and star formation on the central BCG? In order to measure the current star formation in BCGs we have undertaken a program of Spitzer IRAC and MIPS observations. We are in process of obtaining observations of a sample of Brightest Cluster Galaxies in 70 clusters selected from the ROSAT all sky survey. In about 25% of the sources observed so far, we detect a mid-IR excess which we attribute to dust heated by star formation. We propose to obtain ACS/SBC observations of the Lyman Alpha emission line and the adjacent FUV continuum in 7 BCGs which are in cooling core clusters of galaxies and have a large mid-IR excess. We also propose WFPC2 F606W observations of the two clusters without high resolution imaging to allow us to image the dust on the same scale as the Far UV continuum. The FUV will allow us to confirm the presense of ongoing starformation in these BCGs and will allow us to rule out an AGN as the dominant contributer to the mid-IR. The morphology and spatial extent of the young stars and the heated dust and CO will constrain the spatial scale over which star formation occurs and thus where the cooling gas is deposited. The combination of our FUV and IR observations will allow us to estimate the star formation rates which must balance the rate at which cold gas is deposited in the BCG. Our proposed FUV observations will produce unique information about the cooling gas, the true mass accretion rates, and the star formation rates in BCGs and its effect on the galaxy.

We wil obtain ACS/SBC observations of the Lyman alpha emission line and the adjacent FUV continuum in 7 cooling core clusters of galaxies. We have chosen clusters from the ROSAT Brightest Cluster Sample (BCS) (Ebeling et al 1998). We have picked clusters with extreme H-alpha luminosities (1E42-43 ergs/s) which are about one order of magnitude higher than those of A1795 and A2597 (Crawford et al 1999). The high H-alpha luminosities place the strongest demands on models for heating and cooling in the ICM, and the ionization of the nebulae. We will observe each cluster in a filter which passes Lyman alpha and one which does not. The second filter will be used for the measurement of the FUV continuum and for continuum subtraction from the Lyman alpha image. The F125LP filter is ideal for the Lyman alpha image since it does not include geocoronal Lyman alpha but passes extragalactic Lyman alpha, for z>0.03. The continuum filter is F140LP for z < 0.11, F150LP for 0.11< z < 0.19, and F165LP for 0.19 < z < 0.31, The ACS/SBC is actually more sensitive than the STIS/FUV-MAMA that we used for A1795 and A2597. We have run a series of ETC calculations which show that our expected signal-to-noise ratio for the seven clusters is comparable to or better than the values we obtained for A1795 and A2597. In order to calculate the S/N we use the observed H-alpha flux for each cluster and estimate the expected Lyman-alpha flux and FUV continuum using the empirical relationships we found in A1795 and A2597 (O'Dea et al 2004). Our previous HST FUV observations detected all three central dominant galaxies (A426, A1795, and A2597 - Baum et al 2005; O'Dea eta l 2004). So we expect to detect the FUV emission in these clusters. We will also obtain an observation in WFPC2 F606W for the two galaxies without such data - R1532+30 and Z8193. This will allow us to image the dust on the same scale as the FUV. We have shifted the position of RXJ0821 ten arsec north to avoid a bright star to the south of the SBC FOV. All observations are done with a 3 point dither. ISM IN EXTERNAL GALAXIES 12 false 0.0 0.0 false false false false false SUPPORTED CLUSTER OF GALAXIES BCM J2000 10 23 39.6000 +04 11 12.00 J2000 CLUSTER OF GALAXIES BCM COOLING FLOW J2000 14 01 2.0000 +02 52 45.00 J2000 CLUSTER OF GALAXIES BCM J2000 17 17 19.1000 +42 26 57.20 J2000 CLUSTER OF GALAXIES BCM COOLING FLOW J2000 00 00 0.0000 +00 00 0.00 J2000 CLUSTER OF GALAXIES BCM COOLING FLOW J2000 00 00 0.0000 +00 00 0.00 J2000 CLUSTER OF GALAXIES BCM COOLING FLOW J2000 00 00 0.0000 +00 00 0.00 J2000 CLUSTER OF GALAXIES COOLING FLOW BCM J2000 00 00 0.0000 +00 00 0.00 J2000 ACS/SBC Imaging No No F140LP ACS/SBC Imaging No No F165LP ACS/SBC Imaging No No F140LP ACS/SBC Imaging No No F165LP ACS/SBC Imaging No No F125LP ACS/SBC Imaging No No F150LP ACS/SBC Imaging No No F140LP ACS/SBC Imaging No No F150LP WFPC2 Imaging No F606W ACS/SBC Imaging No No F140LP ACS/SBC Imaging No No F165LP ACS/SBC Imaging No No F125LP ACS/SBC Imaging No No F150LP ACS/SBC Imaging No No F140LP ACS/SBC Imaging No No F150LP WFPC2 Imaging No F606W POS-TARG DITHER 0.472 LINE false false 3 44.4 ACS-SBC-DITHER-LINE 1

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