18017( 4) - 13-Sep-2025 03:44:16 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18017 Version: 4 Check-in Time: 13-Sep-2025 03:44:16 STScI Edit Number: 0 Title Investigating AGN Feedback in a z=0.8 Brightest Cluster Galaxy with a Remarkable 30 Kiloparsec Extended Dust Tail ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Allison Noble Arizona State University Y CoI: Dr. Tracy Webb McGill University N CoI: Prof. Gillian Wilson University of California - Merced N CoI: Dr. Adam Muzzin York University N CoI: Prof. Julie Hlavacek-Larrondo Universite de Montreal N CoI: Mr. Simon D. Mork Arizona State University N CoI: Dr. Esra Bulbul Max Planck Institute for Extraterrestrial N Physics CoI: Dr. Patrick S. Kamieneski Arizona State University N CoI: Alex Pigarelli Arizona State University N ------------------------------------------------------------------------------------ Abstract We have discovered a remarkable star-forming Brightest Cluster Galaxy (BCG) at spectroscopic redshift of z=0.81 that has asymmetric and extended dust emission over 30 kiloparsecs, embedded with a powerful radio source. BCGs are the most massive galaxies in the Universe, at any epoch, and reside at the centers of galaxy clusters. Besides their inherent interest as extreme systems, BCGs undergo an astrophysical balancing act between gas cooling and energy feedback within the dense intracluster medium. They thus offer a unique opportunity to study the physics of AGN feedback, as the energy imparted by the AGN leaves unique imprints on the surrounding gaseous medium. We propose joint HST UV and JVLA imaging to map out recent star formation and search for jetted AGN emission. We will complement this with high-resolution archival ALMA dust continuum and optical Euclid observations for a premiere case study of a star-forming and radio-bright BCG. The full suite of observations will allow us to connect the origin of the dust tail to the radio source and investigate the role of feedback in this cluster core at z=0.81. ------------------------------------------------------------------------------------ Observations Description ------------------------ The goal of this program is to obtain 3 orbits of WFC3/UVIS imaging over a galaxy cluster at z=0.8 in a single filter F475W. The cluster extends beyond the full FOV, so the full detector will provide useful ancillary data, but the primary target of interest is the brightest cluster galaxy (BCG). The BCG main lobe is 1.5 arcesc in diameter, but it also has a dust tail which extends over 6 arcsec to the east, and potential jetted radio emission over 16 arcsec, aligned along the dust tail. The primary aim of the F475W imaging is to trace clumpy and filamentary emission (rest-frame 260nm), roughly down to levels of ~4 Msol/yr, within the dust tail and in the vicinity of the BCG and radio emission. We aim to achieve this over 3 orbits in F475W. We are also getting joint VLA imaging at high-resolution with this program. We do not place orient constraints to maximize schedulability, but aim to place the BCG at the optimal 18017( 4) - 13-Sep-2025 03:44:16 - [ 2] detector position to maximize it's S/N and mitigate CTE losses, which could be especially important for fainter UV clumps along the dust tail. Orbit / visit / dithering strategy: ----------------- The single visit consists of 3 orbits, all with F475W. We will use a standard 2-point dither pattern within each orbit to facilitate PSF reconstruction and cosmic ray removal (WFC3-UVIS-DITHER-LINE-2PT). We will thus acquire two individual exposures per orbit, at ~1220 seconds each. Given the long exposures, we expect the background to be high enough that we will not require a postflash to help mitigate CTE losses. We have also included small pos targ offsets of +1.5, -1.5 pixels and -2.33, +1.5 pixels from the first orbit to help with cosmic ray removal over the 6 dithered exposures. Aperture: --------------- We will place the BCG at the reference position of aperture UVIS2-C1K1C-CTE. We will stil read out the full 2-chip frame to gain coverage of the surrounding cluster field, but will minimize CTE losses of the BCG and dust tail by placing them closer to the readout amplifier. Given the extent of the dust tail and radio emisison over 16 arcsec, there should be ample space to still cover these features in full for any orient. ------------------------------------------------------------------------------------ 18017( 4) - 13-Sep-2025 03:44:16 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SPARCS0333 GALAXY, COOLING FLOW, RA=03H33M16.7280S, J2000 Z = 0.8 V = 23.1 HIGH REDSHIFT GALAXY, DEC=-26D53'46.40" JET, TIDAL TAIL Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 18017( 4) - 13-Sep-2025 03:44:16 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.145 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 18017( 4) - 13-Sep-2025 03:44:16 - [ 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 SPARCS0333 WFC3/UVI ACCUM UVIS2-C1K F475W 1 1233 S PATTERN 1 1 S 1C-CTE (2466 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SPARCS0333 WFC3/UVI ACCUM UVIS2-C1K F475W 1 1223 S POS TARG +0.06, -0.07; S 1C-CTE (2446 S) PATTERN 1 2 ------------------------------------------------------------------------------------------------------------------------------------ 3 SPARCS0333 WFC3/UVI ACCUM UVIS2-C1K F475W 1 1223 S POS TARG -0.092, +0.098; S 1C-CTE (2446 S) PATTERN 1 3 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ SPARCS0333 1 WFC3/UVI ACCUM UVIS2-C1 F475W 1 none none none 1 N/A S K1C-CTE SPARCS0333 1 WFC3/UVI ACCUM UVIS2-C1 F475W 2 none none none 1 N/A S K1C-CTE SPARCS0333 2 WFC3/UVI ACCUM UVIS2-C1 F475W 1 none none none 2 N/A S K1C-CTE SPARCS0333 2 WFC3/UVI ACCUM UVIS2-C1 F475W 2 none none none 2 N/A S K1C-CTE SPARCS0333 3 WFC3/UVI ACCUM UVIS2-C1 F475W 1 none none none 3 N/A S K1C-CTE SPARCS0333 3 WFC3/UVI ACCUM UVIS2-C1 F475W 2 none none none 3 N/A S K1C-CTE 18017( 4) - 13-Sep-2025 03:44:16 - [ 6] Summary Form for Proposal 18017 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2-C1K1C-CTE ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1, PATTERN 1 2, PATTERN 1 3, POS TARG +0.06, -0.07, POS TARG -0.092, +0.098 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F475W ------------------------------------------------------------------------------------------------------------------------------------ Target Names SPARCS0333 ------------------------------------------------------------------------------------------------------------------------------------