17101( 5) - 13-Jan-2023 18:42:43 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17101 Version: 5 Check-in Time: 13-Jan-2023 18:42:43 STScI Edit Number: 0 Title Clash of Titans: Characterizing SPT-CLJ0307-6225, a major merger in the plane of the sky ------------------------------------------------------------------------------------ Type Cycle GO 30 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Alfredo Zenteno NOIRLab - CTIO (Chile) Y CoI: Dr. Rogerio Monteiro-Oliveira Academia Sinica, Institute of Astronomy N and Astrophysics CoI: Dr. Armin Rest Space Telescope Science Institute N CoI: Dr. Eleazar Rodrigo Carrasco NOIRLab - Gemini South (Chile) N Damele CoI: Dr. Guillaume Mahler Durham Univ. N CoI: Dr. Hector Cuevas Universidad de La Serena N CoI: Dr. Matthew Bayliss University of Cincinnati Main Campus N CoI: Dr. Annalisa Calamida Space Telescope Science Institute N CoI: Mr. Daniel Hernandez-Lang Ludwig Maximilian Universitat of Munich N CoI: Hugo Antonio Prado Plaza Universidad de La Serena N CoI: Dr. Alexandro Saro Universita degli Studi di Trieste N ------------------------------------------------------------------------------------ Abstract Mergers of galaxy clusters are natural dark matter (DM) colliders. If DM particles self interact, signatures of the interaction can be found in merging clusters as an spatial offset among the collisionless cluster galaxies, the intracluster gas, and the cluster potential, dominated by the DM. Typically, to place constraints on the value of the DM particle self-interacting cross section, ensembles ($\sim 40$) of merging clusters are used. Nevertheless, most of the constraining power comes from a special type of mergers: oriented in the plane of the sky, with (relatively) similar cluster masses, and showing a large displacement between the collisional and the collisionless components. Finding those special mergers would significantly improve the current constraints on the DM particle self-interacting cross section. SPT-CLJ0307-6225 is a merging cluster in the plane of the sky, with {\it Chandra} X--ray showing a comet like gas distribution, Gemini/GMOS and VLT/MUSE spectroscopy that confirms a plane-of-the-sky orientation of the merger, and ground based imaging confirming both, a large gas galaxy offsets ($\sim 790$ and $\sim 360$ kpc) and the need for space base observations, for a robust weak lensing analysis. The superb imaging of HST will allow us to map the dark matter mass density distribution of SPT-CLJ0307-6225, and to use it to place constraints on the self-interacting DM cross section. ------------------------------------------------------------------------------------ Observations Description ------------------------ Our observing plan covers the primary cluster mass with two pointings of ACS (WFC), with 3 orbits covering the most concentrated southern region and 2 orbits in the north. Both pointings use a 4-step dither patter for optimal PSF sampling, with an additional F606W exposure and dither over the chip gap in the southern pointing. The restricted orient rages are intended to align the mosaic 17101( 5) - 13-Jan-2023 18:42:43 - [ 2] with the cluster mass distribution. NOTE that for scheduling purposes, we have included orient ranges that are 180 degrees rotated as it keeps the same coverage of the field. However, if the orient falls in the 280-300deg range then the tiles need to be swapped, ensuring that the pointing with 3 orbits covers the BCG-SOUTH targets regardless of orientation. Overall coverage of the BCG targets 2-4 is critical, so in the scheduling process once the final orientation is set we would like to review the final detector placement to ensure it gives optimal coverage. ------------------------------------------------------------------------------------ 17101( 5) - 13-Jan-2023 18:42:43 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SPT-CL-J0307 CLUSTER OF GALAXIES, RA=03H07M19.0000S, J2000 V = 25 -6226 HIGH REDSHIFT CLUSTER DEC=-62D26'22.00" Reference Frame: Other: SIMBAD Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2015.5 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 2 BCG-NORTH GALAXY, GRAVITATIONAL RA=03H07M20.8500S, J2000 V = 23 LENS DEC=-62D24'32.12" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 3 BCG-SOUTH-1 GALAXY, GRAVITATIONAL RA=03H07M12.7500S, J2000 V = 23 LENS DEC=-62D27'40.43" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 4 BCG-SOUTH-2 GALAXY, GRAVITATIONAL RA=03H07M16.5700S, J2000 V = 23 LENS DEC=-62D26'41.39" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 17101( 5) - 13-Jan-2023 18:42:43 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.262 Line_Spacing 0.192 Coordinate_Frame POS-TARG Pattern_Orient 18.39 Angle_Between_Sides 68.14 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 17101( 5) - 13-Jan-2023 18:42:43 - [ 5] Visit: 03 (BCG-NORTH) Visit Requirements: ORIENT 89D TO 105 D On Hold Comments: Additional Comments: Orient ranges are inteded to follow the cluster mass distribution, but this tile MUST comfortably cover target BCG-NORTH. 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 BCG-NORTH ACS/WFC ACCUM WFCENTER F606W 1 600 S PATTERN 1 1-2 (2412 S) Comments: Part of a ACS WFC Dither Box pattern, which alternates with the F814W filter over the course of 2 orbits. A deeper F606W exposure is preferred for the science case. ------------------------------------------------------------------------------------------------------------------------------------ 2 BCG-NORTH ACS/WFC ACCUM WFCENTER F814W 1 500 S (2012 S) Comments: Part of a ACS WFC Dither Box pattern, which alternates with the F606W filter over the course of 2 orbits. ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ BCG-NORTH 1 ACS/WFC ACCUM WFCENTER F606W 1 none none none 1 N/A BCG-NORTH 1 ACS/WFC ACCUM WFCENTER F606W 2 none none none 1 N/A BCG-NORTH 1 ACS/WFC ACCUM WFCENTER F606W 3 none none none 2 606.0 S BCG-NORTH 1 ACS/WFC ACCUM WFCENTER F606W 4 none none none 2 606.0 S BCG-NORTH 2 ACS/WFC ACCUM WFCENTER F814W 1 none none none 1 N/A BCG-NORTH 2 ACS/WFC ACCUM WFCENTER F814W 2 none none none 1 N/A BCG-NORTH 2 ACS/WFC ACCUM WFCENTER F814W 3 none none none 2 506.0 S BCG-NORTH 2 ACS/WFC ACCUM WFCENTER F814W 4 none none none 2 506.0 S 17101( 5) - 13-Jan-2023 18:42:43 - [ 6] Visit: 04 (BCG-SOUTH) Visit Requirements: SAME ORIENT AS 03 On Hold Comments: Additional Comments: Orient ranges are inteded to follow the cluster mass distribution, but this tile MUST comfortably cover target BCG-SOUTH-1 and 2. 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 BCG-SOUTH-1 ACS/WFC ACCUM WFCENTER F606W 1 800 S PATTERN 1 1-2 (3211 S) Comments: Part of a ACS WFC Dither Box pattern, which alternates with the F814W filter over the course of 2 orbits.This is the deeper of the two pointings, and the extra exposure is in F606W as a deeper F606W exposure is preferred for the science case. ------------------------------------------------------------------------------------------------------------------------------------ 2 BCG-SOUTH-1 ACS/WFC ACCUM WFCENTER F814W 1 800 S (3217 S) Comments: Part of a ACS WFC Dither Box pattern, which alternates with the F606W filter over the course of 2 orbits. This is the deeper of the two pointings. ------------------------------------------------------------------------------------------------------------------------------------ 3 BCG-SOUTH-1 ACS/WFC ACCUM WFCENTER F606W 1 800 S POS TARG .247, 2.984 see below (805 S) Comments: The 5th exposure in F606W for this pointing, which brings the total F606W exposure to 3200s. We add a final dither after the box to step over the chip gap. ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ BCG-SOUTH-1 1 ACS/WFC ACCUM WFCENTER F606W 1 none none none 1 N/A BCG-SOUTH-1 1 ACS/WFC ACCUM WFCENTER F606W 2 none none none 1 N/A BCG-SOUTH-1 1 ACS/WFC ACCUM WFCENTER F606W 3 none none none 2 806.0 S BCG-SOUTH-1 1 ACS/WFC ACCUM WFCENTER F606W 4 none none none 3 805.0 S BCG-SOUTH-1 2 ACS/WFC ACCUM WFCENTER F814W 1 none none none 1 N/A BCG-SOUTH-1 2 ACS/WFC ACCUM WFCENTER F814W 2 none none none 2 806.0 S BCG-SOUTH-1 2 ACS/WFC ACCUM WFCENTER F814W 3 none none none 2 806.0 S BCG-SOUTH-1 2 ACS/WFC ACCUM WFCENTER F814W 4 none none none 3 805.0 S BCG-SOUTH-1 3 ACS/WFC ACCUM WFCENTER F606W none none none none 3 805.0 S 17101( 5) - 13-Jan-2023 18:42:43 - [ 7] Summary Form for Proposal 17101 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFCENTER ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 89D TO 105 D, PATTERN 1 1-2, POS TARG .247, 2.984, SAME ORIENT AS 03 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names BCG-NORTH, BCG-SOUTH-1 ------------------------------------------------------------------------------------------------------------------------------------