This is a resubmission of Cycle 24 proposal 1012, where we now address the comments from the panel. 38639784 Assigned ID: 573 ----- Attempting Submission 1 (Fri Apr 07 15:33:20 GMT 2017) ----- 0 ----- Attempting Submission 1 (Thu Jul 20 11:36:34 GMT 2017) ----- We have identified a nearby pair of closely interacting dwarf galaxies that host a population of candidate young massive clusters (YMCs). The strong interaction has triggered nearly coeval galaxy-scale starbursts, with a delay time of only ~100 Myr from one galaxy to the other. It has also altered their stellar structure and content, as indicated by the presence of prominent tidal features, some of which host YMCs. Here we propose to carry out a UV-to-optical imaging survey of the system with WFC3/UVIS. We will take advantage of HST's unrivalled resolution and sensitivity to detect and characterize the star cluster population in each of the two interacting dwarf galaxies. The proposed multiband photometry will be instrumental to determine ages, masses and sizes of the YMCs, as well as to provide a robust characterization of the underlying host galaxy--thus allowing for an investigation of the cluster formation efficiency in a gas-rich, high-density, metal-poor environment very reminiscent of the existing conditions at high redshift. This is a relatively simple imaging proposal of a pair of interacting dwarf galaxies hosting young star cluster candidates. We will observe the pair of galaxies with WFC3/UVIS in six filters: F275W, F336W, F438W, F606W, F657N, F814W. The two objects fit within a single WFC3 pointing provided the orientation is limited to a narrow range of angles (55-63deg), which we have specified. To improve the scheduling of the observations are split in two visits using blue and (mostly) red filters. We also ask for the second visit to be observed at exactly the same orient angle as the first one. Because in addition to the clusters we're looking for extended emission we use a gap-line dithering pattern for most filters (or individual offset exposures). Galaxies and the IGM Stellar Populations 6 false true false false false false SUPPORTED GALAXY INTERACTING GALAXY This object was generated by the targetselector and retrieved from the NED database. J2000 J2000 WFC3/UVIS Imaging No No F275W WFC3/UVIS Imaging No No F336W WFC3/UVIS Imaging No No F438W WFC3/UVIS Imaging No No F606W WFC3/UVIS Imaging No No F657N WFC3/UVIS Imaging No No F814W POS-TARG MOSAIC DITHER 4 2.414 WFC3-UVIS-DITHER-BOX false 81.785 true 0.112 0.173 2 85.759 POS-TARG WFC3-UVIS-GAP-LINE 23.884 4 false 1500549017730 /Users/rsj/Dropbox/work/proposals/2017B/hst_ugc5205/phase2/OP-cache/ugc5205_wfc3_p2-v01.xml The scheduling data was generated by CASM 25.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 15114 :visit-id "01" :proposal-version -1 :trans-version "20170613" :date "20-Jul-2017 12:10:17.0" :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 2309984 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15114 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 15114 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2856 :al-overhead-at-end 122 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3202 :pcs-gap 0 ) (Tic-Orbit :proposal-id 15114 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2975 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3202 :pcs-gap 0 ) true 2 0 1500549054577 /Users/rsj/Dropbox/work/proposals/2017B/hst_ugc5205/phase2/OP-cache/ugc5205_wfc3_p2-v02.xml The scheduling data was generated by CASM 25.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 15114 :visit-id "02" :proposal-version -1 :trans-version "20170613" :date "20-Jul-2017 12:10:53.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 2887456 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15114 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 15114 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2856 :al-overhead-at-end 122 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3202 :pcs-gap 0 ) (Tic-Orbit :proposal-id 15114 :visit-id "02" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2976 :al-overhead-at-end 122 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3202 :pcs-gap 0 ) (Tic-Orbit :proposal-id 15114 :visit-id "02" :orbit-number 3 :pcs-time 222 :si-vis-utilization 2973 :al-overhead-at-end 122 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3202 :pcs-gap 0 ) true 3 0