17114( 3) - 15-Nov-2022 13:44:39 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17114 Version: 3 Check-in Time: 15-Nov-2022 13:44:39 STScI Edit Number: 0 Title Four New Dissociative Merging Clusters ------------------------------------------------------------------------------------ Type Cycle GO 30 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. David Wittman University of California - Davis Y CoI: Dr. Kyle Finner California Institute of Technology N CoI: Prof. Myungkook J. Jee Yonsei University N CoI: Faik Bouhrik University of California - Davis N CoI: Rodrigo Alves Stancioli University of California - Davis N ------------------------------------------------------------------------------------ Abstract We propose ACS imaging of four exciting new merging clusters with ``dissociative'' morphology---two galaxy subclusters on either side of a central gas concentration, indicative of a recent head-on collision. The imaging will enable a weak lensing analysis that will (i) determine the dark matter halo locations relative to the galaxy subcluster locations; (ii) measure the subcluster masses; and (iii) place limits on the presence of any additional substructures. In conjunction with existing X-ray data and a scheduled spectroscopic survey, the dark matter halo locations and masses will enable accurate modeling of the merger scenario. Upper limits on galaxy-dark matter offsets will be translated to upper limits on the momentum exchanged between the dark matter halos. Together with accurate modeling of the merger scenario, this will place upper limits on the dark matter scattering cross section. These four systems are promising in that respect because their modest separations suggest that they are seen not long after first pericenter. ------------------------------------------------------------------------------------ Observations Description ------------------------ For each target, we request two-band ACS imaging, one orbit per band, to provide color selection of background galaxies. The total request is thus 8 orbits for four clusters. Filter selection: The best color selection is obtained when filters straddle the 4000 A break. We thus treat separately the three targets at redshifts 0.24-0.31, where the break is observed at 4960-5240 A, and the target at z = 0.55 where the break is observed at 6200 A. In both cases we use the F606W filter because it is generally the most sensitive filter, but it plays a different role at different redshifts. For three targets, F606W is longward of the break and is complemented by F475W shortward of the break. For the z = 0.55 target, the 4000 A break occurs in the middle of the F606W filter, hence reducing the F606W flux for early-type cluster members: F606W can play the role of the shorter filter. We propose to use F814W as the long filter. Depth: the source densities and convergence map angular resolutions cited in the scientific justification correspond to a single orbit of F606W and/or F814W at these redshifts (eg, Dawson et al. 2012). An angular resolution of 10 arcsec positional uncertainty on the dark matter halos is an appropriate goal because it corresponds to 38-65 kpc for these clusters; for comparison, the separation 17114( 3) - 15-Nov-2022 13:44:39 - [ 2] between BCGs ranges from 335-544 kpc, and the smallest separation between X-ray peak and BCG is 16 arcsec or 74 kpc. We can rely on previous results mapping exposure time to dark matter positional uncertainty because our targets have masses similar to those in the above-cited works. Simet et al. (2017) calibrated the relation between weak lensing mass and redMaPPer richness; using that relation and the known target richness we find M200 ranging from 4.6-14x10^14 h^-1 solar masses. Footprint: the targets are compact enough to fit in the ACS field without any constraints on the roll angle or any need to mosaic. We request small dithers to fill gaps. ------------------------------------------------------------------------------------ 17114( 3) - 15-Nov-2022 13:44:39 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 WHL-J121917. CLUSTER OF GALAXIES, RA=12H19M9.3455S +/- 1", J2000 V = 22 +/- 1 6+505432 RICH CLUSTER DEC=+50D54'43.31" +/- 1" Reference Frame: Other: NED Comments: This object was generated by the targetselector and retrieved from the NED database. ------------------------------------------------------------------------------------------------------------------------------------ 2 WHL-J130558. CLUSTER OF GALAXIES, RA=13H06M0.1358S +/- 1", J2000 V = 18.6 +/- 1 9+263048 RICH CLUSTER DEC=+26D30'56.28" +/- 1" Reference Frame: Other: NED Comments: This object was generated by the targetselector and retrieved from the NED database. ------------------------------------------------------------------------------------------------------------------------------------ 3 WHL-J001938. CLUSTER OF GALAXIES, RA=00H19M38.7675S +/- 1", J2000 V = 18.4 +/- 1 7+033557 RICH CLUSTER DEC=+03D36'47.17" +/- 1" Reference Frame: Other: NED Comments: This object was generated by the targetselector and retrieved from the NED database. ------------------------------------------------------------------------------------------------------------------------------------ 4 WHL-J024808. CLUSTER OF GALAXIES, RA=02H48M11.3678S +/- 1", J2000 V = 18.4 +/- 1 3-021637 RICH CLUSTER DEC=-02D16'26.68" +/- 1" Reference Frame: Other: NED Comments: This object was generated by the targetselector and retrieved from the NED database. ------------------------------------------------------------------------------------------------------------------------------------ 17114( 3) - 15-Nov-2022 13:44:39 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 3.034 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 85.29 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 17114( 3) - 15-Nov-2022 13:44:39 - [ 5] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 WHL-J024808 ACS/WFC ACCUM WFCENTER F606W 1 500 S PATTERN 1 1-2 .3-021637 see below (2193 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 WHL-J024808 ACS/WFC ACCUM WFCENTER F475W 1 500 S .3-021637 see below (2208 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ WHL-J024808.3-02163 1 ACS/WFC ACCUM WFCENTER F606W 1 none none none 1 726.0 S 7 WHL-J024808.3-02163 1 ACS/WFC ACCUM WFCENTER F606W 2 none none none 1 726.0 S 7 WHL-J024808.3-02163 1 ACS/WFC ACCUM WFCENTER F606W 3 none none none 2 741.0 S 7 WHL-J024808.3-02163 2 ACS/WFC ACCUM WFCENTER F475W 1 none none none 1 726.0 S 7 WHL-J024808.3-02163 2 ACS/WFC ACCUM WFCENTER F475W 2 none none none 2 741.0 S 7 WHL-J024808.3-02163 2 ACS/WFC ACCUM WFCENTER F475W 3 none none none 2 741.0 S 7 17114( 3) - 15-Nov-2022 13:44:39 - [ 6] Visit: 02 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 WHL-J121917 ACS/WFC ACCUM WFCENTER F606W 1 500 S PATTERN 1 1-2 .6+505432 see below (2325 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 WHL-J121917 ACS/WFC ACCUM WFCENTER F814W 1 500 S .6+505432 see below (2331 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ WHL-J121917.6+50543 1 ACS/WFC ACCUM WFCENTER F606W 1 none none none 1 773.0 S 2 WHL-J121917.6+50543 1 ACS/WFC ACCUM WFCENTER F606W 2 none none none 1 773.0 S 2 WHL-J121917.6+50543 1 ACS/WFC ACCUM WFCENTER F606W 3 none none none 2 779.0 S 2 WHL-J121917.6+50543 2 ACS/WFC ACCUM WFCENTER F814W 1 none none none 1 773.0 S 2 WHL-J121917.6+50543 2 ACS/WFC ACCUM WFCENTER F814W 2 none none none 2 779.0 S 2 WHL-J121917.6+50543 2 ACS/WFC ACCUM WFCENTER F814W 3 none none none 2 779.0 S 2 17114( 3) - 15-Nov-2022 13:44:39 - [ 7] Visit: 03 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 WHL-J130558 ACS/WFC ACCUM WFCENTER F606W 1 500 S PATTERN 1 1-2 .9+263048 see below (2216 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 WHL-J130558 ACS/WFC ACCUM WFCENTER F475W 1 500 S .9+263048 see below (2230 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ WHL-J130558.9+26304 1 ACS/WFC ACCUM WFCENTER F606W 1 none none none 1 734.0 S 8 WHL-J130558.9+26304 1 ACS/WFC ACCUM WFCENTER F606W 2 none none none 1 734.0 S 8 WHL-J130558.9+26304 1 ACS/WFC ACCUM WFCENTER F606W 3 none none none 2 748.0 S 8 WHL-J130558.9+26304 2 ACS/WFC ACCUM WFCENTER F475W 1 none none none 1 734.0 S 8 WHL-J130558.9+26304 2 ACS/WFC ACCUM WFCENTER F475W 2 none none none 2 748.0 S 8 WHL-J130558.9+26304 2 ACS/WFC ACCUM WFCENTER F475W 3 none none none 2 748.0 S 8 17114( 3) - 15-Nov-2022 13:44:39 - [ 8] Visit: 04 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 WHL-J001938 ACS/WFC ACCUM WFCENTER F606W 1 500 S PATTERN 1 1-2 .7+033557 see below (2193 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 WHL-J001938 ACS/WFC ACCUM WFCENTER F475W 1 500 S .7+033557 see below (2208 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ WHL-J001938.7+03355 1 ACS/WFC ACCUM WFCENTER F606W 1 none none none 1 726.0 S 7 WHL-J001938.7+03355 1 ACS/WFC ACCUM WFCENTER F606W 2 none none none 1 726.0 S 7 WHL-J001938.7+03355 1 ACS/WFC ACCUM WFCENTER F606W 3 none none none 2 741.0 S 7 WHL-J001938.7+03355 2 ACS/WFC ACCUM WFCENTER F475W 1 none none none 1 726.0 S 7 WHL-J001938.7+03355 2 ACS/WFC ACCUM WFCENTER F475W 2 none none none 2 741.0 S 7 WHL-J001938.7+03355 2 ACS/WFC ACCUM WFCENTER F475W 3 none none none 2 741.0 S 7 17114( 3) - 15-Nov-2022 13:44:39 - [ 9] Summary Form for Proposal 17114 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFCENTER ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1-2 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F475W, F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names WHL-J001938.7+033557, WHL-J024808.3-021637, WHL-J121917.6+505432, WHL-J130558.9+263048 ------------------------------------------------------------------------------------------------------------------------------------