These observations are a relatively straightforward imaging program, consisting of two orbits, using the WFC3-UVIS camera. The first orbit will use the F475W filter, while the second will use the F775W filter. Each orbit is made up of 6 subexposures, a single short exposure (60s) at the beginning and the end of the vist, and the main part of each vist made up of four dithered subexposures of 500s each (total of 2000s). For the dithering strategy we chose the "dither-box" with 4 points to best sample the PSF, as the highest resolution possible is a key element of this program. We realize that the 'chip gap' will not be sampled, and we have centered our observations accordingly. We prefer that visit one be taken at Orient=315, and that visit 2 be taken at the same orientation as visit one. Alternatively, we can use Orient=135+-15, however, in that case we would need to re-center the iamges. The first and last exposures should be offset by 4.5 pixels to facilitate cosmic-ray removal and hot/warm pixel avoidance on targets. ----- Attempting Submission 2 (Fri Jun 19 13:12:28 CEST 2009) ----- Luminosity Profiles of Extremely Massive Clusters in NGC 7252 The galactic merger remnant NGC 7252 represents one of the most extreme post-starburst environments in the local universe. During the disk-disk merger (~400 Myr ago) this galaxy produced the largest young massive star cluster population known, including two clusters above 10^7 Msun, a factor of 100 more massive than typical globular clusters in the Milky Way. We propose ACS-HRC observations of 3 fields in NGC 7252 in order to explore the detailed properties, i.e. luminosity profiles, of these massive star clusters. These observations will be able to test massive cluster formation mechanisms (e.g. the cluster merger scenario) as well as the possible tidal erosion and truncation of the outer regions of the clusters by the galactic tidal field. These observations will compliment our large on-going study using archival HST data, of star cluster profiles outside the Local Group. The cluster population in NGC 7252 will extend our sample in cluster mass by an order of magnitude.
We propose ACS-HRC observations of 3 fields in NGC 7252 in order to explore the detailed properties, i.e. luminosity profiles, of these massive star clusters. Three fields will be observed, each in the F475W and F775W filters. The multiple filters will allow independent checks of the size/profile, and allow us to gain some colour information for a large number of clusters. UNRESOLVED STELLAR POPULATIONS AND GALAXY STRUCTURE 12 false 0.0 0.0 false false false false false SUPPORTED STELLAR CLUSTER GLOBULAR CLUSTER NUCLEUS OPEN CLUSTER STAR FORMING REGION This object was generated by the targetselector and retrieved from the NED database. J2000 22 20 44.8000 -24 40 42.00 J2000 ACS/HRC Imaging No No F475W ACS/HRC Imaging No No F775W ACS/HRC Imaging No No F475W ACS/HRC Imaging No No F775W ACS/HRC Imaging No No F475W ACS/HRC Imaging No No F775W POS-TARG DITHER 0.173 LINE 0.112 false false 81.785 4 23.884 WFC3-UVIS-DITHER-BOX 2 false The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. /private/tmp/OPVisit45285.xml In this visit we plan to have 6 subexposures, two short (60s) at the beginning and end (one at the start and one at the end) of the orbit (offset by 4.5 pixels, i.e. 0.18"). The main part of the orbit will consist of 4 * 500s subexposures, which will be dithered (small box 4 point dither) to improve PSF sampling. We prefer that the observations be taken a Orient=315. If the range of 'Orient' is insufficient for schedualing, then we can also use Orient=135 +- 15, but if this is the case we would like to re-center the observations by ~20" (please contact us if this is the case). We also prefer that Visit 02 be taken at the same orient as Visit 01. (Tic-Visit :proposal-id 11554 :visit-id "01" :proposal-version -1 :trans-version "20090130" :date "19-Jun-2009 13:03:56.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 1732496 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11554 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11554 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2772 :al-overhead-at-end 118 :internal-dur-at-end 670 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3258 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. /private/tmp/OPVisit45284.xml This 2nd visit, should be exactly the same as Visit 01, except images will be taken with the F775W filter instead of the F475W. Please see the comments in Visit 01 as to the goal and preferences of this observation. We prefer that Visit 02 be taken at the same orient as Visit 01. (Tic-Visit :proposal-id 11554 :visit-id "02" :proposal-version -1 :trans-version "20090130" :date "19-Jun-2009 13:03:47.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 1732496 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11554 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11554 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2772 :al-overhead-at-end 118 :internal-dur-at-end 670 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3258 :pcs-gap 0 ) true 1 0