Science Keywords: Select from 2 to 5 items. Science Keywords is a required field. Please specify your scheduling constraints or 'No Constraints' on all Observation forms. 0 Assigned ID: 1132 ----- Attempting Submission 1 (Wed Aug 19 13:46:46 GMT 2020) ----- Joint Chandra/HST 0 ----- Attempting Submission 1 (Mon Aug 24 00:07:05 GMT 2020) ----- Major mergers are pivotal events in the formation of large-scale structure that mark the creation of the most massive galaxy clusters of their epoch. At z>0.5, they are signposts of the first such systems to have formed in the Universe. We propose an exploratory Chandra/HST study of two massive mergers at z>0.5, discovered by the eMACS project and carefully selected to feature a simple, two-body geometry, in order to determine the merger phase (pre- or post-collision), global X-ray properties, and strong-lensing power, thereby assessing their potential for future, in-depth lensing and structure evolution studies. Our target already has partial coverage with HST, obtained as part of a longstanding SNAPshot program on eMACS clusters (PI: Ebeling). To complete the required 4-filter coverage (from the near-UV to 1 micron in the cluster restframe) eMACSJ0502 still needs critically important imaging with ACS in the F814W passband. A single orbit will suffice to allow the secure confirmation and further identification of multiple-image lensing features based on their matching morphology and matching colors. The F814W passband lies fully redward of the D4000A break at the cluster redshift, thus providing critical color information to distinguish between cluster members and lensed background galaxies. The requested one-orbit F814W observation of eMACSJ0502 (dithered to allow the removal of cosmic rays and to fill in the ACS chip gap) matches the depth of the F606W data already in hand for our target. The full 4-filter data set will not only facilitate the identification of lensing features, but will also provide valuable information on the galaxy population of the cluster, highlighting ram-pressure stripping events as well as star formation and dust in the BCGs. n/a Large Scale Structure of the Universe 6 false false false false false false false SUPPORTED CLUSTER OF GALAXIES GRAVITATIONAL LENS RICH CLUSTER J2000 J2000 ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F814W POS-TARG DITHER DITHER 2 3.034 ACS-WFC-DITHER-LINE false false 0.262 2 85.29 POS-TARG ACS-WFC-DITHER-LINE 18.39 1 true 1598227006591 The scheduling data was generated by CASM 28.2. CASM was run in Phase II mode. /private/var/folders/bf/0pxwhb748xlfn8001s6vx6y00000gp/T/OPVisit2946314509464208977.xml (Tic-Visit :proposal-id 16428 :visit-id "01" :proposal-version -1 :trans-version "20200619" :date "23-Aug-2020 13:56:46.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 1136896 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16428 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16428 :visit-id "01" :orbit-number 1 :pcs-time 383 :si-vis-utilization 2778 :al-overhead-at-end 0 :internal-dur-at-end 347 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3165 :pcs-gap 0 ) true 1 0