In this resubmission I fixed an error that I had overlooked. I substituted the F300W filter for the F336W filter. The former filter is what we originally proposed and is better suited to the science since it has a broader band-pass. ----- Attempting Submission 1 (Thu May 10 16:05:15 GMT 2007) ----- Phase II Proposal 11112 (ngc922_wfpc2_cy16_p2) successfully submitted. ----- Attempting Submission 2 (Thu May 10 19:51:39 GMT 2007) ----- Original ACS proposal number 448 Assigned ID: 1408 ----- Attempting Submission 1 (Fri Feb 09 22:06:19 GMT 2007) ----- Phase I Proposal 1408 (ngc922_wfpc2_cy16) successfully submitted. The Collisional Ring Galaxy NGC922 We request WFPC2 images of the newly recognized collisional ring galaxy NGC922 which will become the nearest such system observed by HST. These will be used to get a clear understanding of the geometry of the interaction and the induced star formation in this system. Quantitive modeling of the colors of the star clusters and stellar populations will be used to constrain the star formation history of the system. They will also be used to test the "infant mortality" scenario for star cluster evolution. The derived population ages will test predictions of how star formation evolves in the various components (ring, core, spokes) of collisional rings, and will improve our own simulations of this system. These will be used to determine the final fate of the stars formed in the present burst - some will end up in a central bar or bulge while others will become part of a thickened disk. By analogy this will tell us how similar collisions enrich stellar populations in the early universe. This is especially relevant since the number density of collisional rings increases rapidly with redshift.
We will observe NGC922 in F300W (3 orbits), F439W, (2 orbits), F547M (2orbits) and F814W (2 orbits). The observations will be split between two mosaic positions offset by 40" in order to observe the entire 104" diameter ring with WF2 and WF3. Three exposures will be taken at each mosaic position, with each exposure being shifted by a small dither offset. Both the mosaic and dither offsets are achieved through POS-TARG commands. The position of NGC922 has been adjusted from that given in the phase I proposal in order to conform better with the geometric center of the ring. This allows the pos-targ commands to be robust to the roll-angle that is employed. The observations are split into two visits which are constrained to have the same orient. Ideally they should be scheduled back to back. UNRESOLVED STELLAR POPULATIONS 12 false 0.0 false false false false false false SUPPORTED GALAXY DISK INTERACTING GALAXY RING STARBURST Distance = 43 Mpc from the radial velocity using the Mould (2000, ApJ, 529, 786) multi-attractor model. R = 11.94 +/- 0.05 ABmag HIPASSJ0224-24S1 J2000 02 25 3.7000 -24 47 20.00 J2000 WFPC2 Imaging No F300W WFPC2 Imaging No F439W WFPC2 Imaging No F547M WFPC2 Imaging No F814W /tmp/OPVisit6378.xml All F300W and F439W observations will be taken in this visit. (Tic-Visit :proposal-id 11112 :visit-id "01" :proposal-version -1 :trans-version "20070325" :date "10-May-2007 15:43:20.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "26" :si-bright-earth-limb-angle 20.0 :data-volume 537792 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11112 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11112 :visit-id "01" :orbit-number 1 :pcs-time 355 :si-vis-utilization 2725 :al-overhead-at-end 155 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3147 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11112 :visit-id "01" :orbit-number 2 :pcs-time 355 :si-vis-utilization 2725 :al-overhead-at-end 155 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3147 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11112 :visit-id "01" :orbit-number 3 :pcs-time 355 :si-vis-utilization 2746 :al-overhead-at-end 134 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3147 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11112 :visit-id "01" :orbit-number 4 :pcs-time 355 :si-vis-utilization 2746 :al-overhead-at-end 134 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3147 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11112 :visit-id "01" :orbit-number 5 :pcs-time 355 :si-vis-utilization 2700 :al-overhead-at-end 180 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3147 :pcs-gap 0 ) true 5 0 /tmp/OPVisit37779.xml /tmp/OPVisit6379.xml All F547M, and F814W observations are obtained in this visit. (Tic-Visit :proposal-id 11112 :visit-id "02" :proposal-version -1 :trans-version "20070325" :date "10-May-2007 15:43:33.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 4 :saa-model "26" :si-bright-earth-limb-angle 20.0 :data-volume 537792 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11112 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11112 :visit-id "02" :orbit-number 1 :pcs-time 355 :si-vis-utilization 2746 :al-overhead-at-end 134 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3147 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11112 :visit-id "02" :orbit-number 2 :pcs-time 355 :si-vis-utilization 2729 :al-overhead-at-end 151 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3147 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11112 :visit-id "02" :orbit-number 3 :pcs-time 355 :si-vis-utilization 2746 :al-overhead-at-end 134 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3147 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11112 :visit-id "02" :orbit-number 4 :pcs-time 355 :si-vis-utilization 2700 :al-overhead-at-end 180 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3147 :pcs-gap 0 ) true 4 0 /tmp/OPVisit37780.xml