Numerous studies of the cores of galaxy clusters have revealed that the gas in central regions is not cooling at the rates predicted by the traditional cooling flow model. This discrepancy has inspired a search for heating models that can explain current observations. AGN feedback is considered an attractive solution to several connected problems, such as the high-mass end truncation of galaxy distribution and the absence of cooling-flows in centers of galaxy clusters. Amidst the emerging hypothesis of self-regulated AGN feedback, infrared, optical and FUV observations of clusters also indicate the presence of large amounts of cold gas in their brightest cluster galaxies (BCGs). There are over 30 BCGs that exhibit active star formation based on their mid-infrared and several of those have direct evidence based on FUV and/or optical imaging. In this proposal we aim to investigate a sample of 11 BCGs forming the basis of a Herschel Key Project, which has been awarded 130 hrs to study the detailed properties of the cold gas and dust in these clusters. We propose ACS/SBC FUV observations of five of the 11 BCGs lacking high resolution FUV data needed to probe the star forming regions. The remaining six already have archival ACS/SBC FUV data. We further propose ACS/WFC and WFC3/UVIS observations of two BCGs lacking HST optical data which will allow us to obtain FUV-optical colours to discriminate between young and old stellar populations. These observations are vital to understand the complex inter-relationship between the cooling of the intracluster-medium, cold gas and dust, star formation and AGN activity.

We will observe ACS/SBC observations of the FUV continuum in the brightest cluster galaxies (BCGs) of 5 cool-core clusters of galaxies, which constitute a subset of a Herschel Key Project sample. All but one of the proposed five BCGs have luminous line emission, L[H_alpha] > 1E+40 erg/s. The objects have a redshift range from 0.03 to 0.22 and so we propose the continuum filter F140LP for z<0.11, F150LP for 0.11 < z < 0.19 and F165LP for 0.19 < z < 0.31. We have run a series of ETC calculations using the signal-to-noise ratio (SNR) and the average source surface-brightness obtained for the seven clusters that formed the subject of an earlier accepted proposal (cycle 16). In order to reach comparable sensitivity to image the sites of recent star formation, we propose an orbit for each of the five BCGs. We have checked against the bright-object constraints for ACS/SBC and we are well under the safety limits. We will also obtain ACS/WFC F814W and WFC3/UVIS F689W line-free continuum observations of Hydra-A and RXJ1504.1-024, respectively, the only two galaxies in the Herschel sample without such data. This will allow us to obtain FUV-optical colour and determine the contribution from the old stellar population. All observations are done with a 3 point dither. ISM IN EXTERNAL GALAXIES 12 false 0.0 0.0 false false false false false false SUPPORTED CLUSTER OF GALAXIES COOLING FLOW HALO RICH CLUSTER STAR FORMING REGION This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 09 18 5.6700 -12 05 43.90 J2000 CLUSTER OF GALAXIES COOLING FLOW HALO RICH CLUSTER STAR FORMING REGION This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 16 28 38.2400 +39 33 4.30 J2000 CLUSTER OF GALAXIES COOLING FLOW HALO RICH CLUSTER STAR FORMING REGION This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 10 40 44.4000 +39 57 12.00 J2000 CLUSTER OF GALAXIES COOLING FLOW HALO RICH CLUSTER STAR FORMING REGION This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 07 47 31.3500 -19 17 39.70 J2000 CLUSTER OF GALAXIES COOLING FLOW HALO RICH CLUSTER STAR FORMING REGION This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 15 04 7.5000 -02 48 16.00 J2000 ACS/SBC Imaging No No F140LP ACS/SBC Imaging No No F140LP ACS/SBC Imaging No No F150LP ACS/SBC Imaging No No F140LP ACS/SBC Imaging No No F165LP ACS/WFC Imaging No No F814W WFC3/UVIS Imaging No No F689M POS-TARG DITHER 0.472 LINE false false 3 44.4 ACS-SBC-DITHER-LINE 1 false POS-TARG DITHER 3.011 LINE false false 3 85.28 ACS-WFC-DITHER-LINE 2 false POS-TARG DITHER 0.135 LINE false false 3 46.84 WFC3-UVIS-DITHER-LINE-3PT 3 false The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12220 :visit-id "01" :proposal-version -1 :trans-version "20100505" :date "23-Jun-2010 18:08:31.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 908224 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12220 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Obset :proposal-id 12220 :visit-id "01" :obset-id "A1" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12220 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2910 :al-overhead-at-end 0 :internal-dur-at-end 465 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3245 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12220 :visit-id "01" :orbit-number 2 :pcs-time 333 :si-vis-utilization 2911 :al-overhead-at-end 0 :internal-dur-at-end 349 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3245 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12220 :visit-id "02" :proposal-version -1 :trans-version "20100505" :date "21-Jun-2010 14:27:07.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "28" :si-bright-earth-limb-angle 20.0 :data-volume 55552 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12220 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12220 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2968 :al-overhead-at-end 0 :internal-dur-at-end 99 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3301 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12220 :visit-id "03" :proposal-version -1 :trans-version "20100505" :date "21-Jun-2010 14:27:08.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "28" :si-bright-earth-limb-angle 20.0 :data-volume 55552 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12220 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12220 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2967 :al-overhead-at-end 0 :internal-dur-at-end 99 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3301 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12220 :visit-id "04" :proposal-version -1 :trans-version "20100505" :date "21-Jun-2010 14:27:08.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "28" :si-bright-earth-limb-angle 20.0 :data-volume 55552 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12220 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12220 :visit-id "04" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2916 :al-overhead-at-end 0 :internal-dur-at-end 99 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3249 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12220 :visit-id "05" :proposal-version -1 :trans-version "20100505" :date "23-Jun-2010 18:21:42.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 921792 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12220 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Obset :proposal-id 12220 :visit-id "05" :obset-id "A5" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12220 :visit-id "05" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2901 :al-overhead-at-end 0 :internal-dur-at-end 99 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3234 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12220 :visit-id "05" :orbit-number 2 :pcs-time 333 :si-vis-utilization 2901 :al-overhead-at-end 116 :internal-dur-at-end 354 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3234 :pcs-gap 0 ) false 2 0