17484( 3) - 19-Sep-2023 14:37:24 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17484 Version: 3 Check-in Time: 19-Sep-2023 14:37:24 STScI Edit Number: 0 Title Beyond PAndAS: Two Extremely Faint Candidate Satellites of M33 Identified in Diffuse Light ------------------------------------------------------------------------------------ Type Cycle GO 31 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Ekta Patel University of Utah Y CoI: Dr. Shany Danieli Princeton University Y CoI: Prof. Roberto G. Abraham University of Toronto N CoI: Prof. Pieter van Dokkum Yale University N CoI: Mr. Qing Liu University of Toronto N CoI: Ms. Rebecca Ceppas de Castro McGill University N CoI: Dr. Kristen B W McQuinn Rutgers the State University of New Jersey N CoI: Dr. Jeffrey L Carlin NOIRLab - Vera C. Rubin Operations (AZ) N CoI: Rachael L Beaton Space Telescope Science Institute N CoI: Dr. Andrew Eugene Dolphin Raytheon Technologies N ------------------------------------------------------------------------------------ Abstract M33 is predicted to host more than ten satellites galaxies, but only two potential companions (And XXII, Pisces VII) have been discovered to date. Is this a failure of galaxy formation models, or simply a by-product of how difficult it is to find low surface brightness galaxies in the nearby Universe? In this proposal, we request deep HST observations of two candidate dwarf satellite galaxies identified around M33 using the Dragonfly Telephoto Array. We have undertaken ground-based follow-up which strongly suggests these candidates are dwarf galaxies in the Local Group, but definitive confirmation requires high-resolution space-based imaging. With high-quality HST data, we will (1) confirm the nature of these candidates as galaxies by detecting an adequate number of red giants associated with these galaxies; (2) measure the precise distance to these dwarf candidates to confirm whether they are indeed M33 satellites; (3) measure their physical properties -- geometry and structural parameters, total luminosities, stellar masses, and preliminary star formation histories. If these candidates are indeed dwarfs around M33, this small HST program would quickly double the known population of M33 satellite galaxies and provide a new avenue for carrying out a rigorous search for all potential M33 satellites. This data set will also enable follow-up studies of the dynamics of the M33-M31 system, including new constraints on the orbit of M33, and a direct test for the hierarchical nature of the LCDM paradigm in the regime of low mass galaxies. ------------------------------------------------------------------------------------ Observations Description ------------------------ This proposal aims to obtain two-band photometry for two candidate dwarf satellite galaxies identified around M33, identified using ground-based data. This HST/ACS data will be used to constract deep color-magnitude diagrams with ACS and parallel WFC3 pointings. Each target will be observed with a asingle orbit split between two F606W and two F814W sub-exposures, to effectively 17484( 3) - 19-Sep-2023 14:37:24 - [ 2] eliminate hot pixels and cosmic rays. A single parallel exposure per filter will be obtained with WFC3 and will be used to estimate the background contamination from the MW and M31 stellar halos. ------------------------------------------------------------------------------------ 17484( 3) - 19-Sep-2023 14:37:24 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 CANDIDATE-1 GALAXY, DWARF RA=01H41M20.5136S, J2000 V = 20.0 +/- 1.0 SPHEROIDAL, LSB DEC=+24D54'12.99" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 2 CANDIDATE-2 GALAXY, DWARF RA=01H41M42.1900S, J2000 V = 20.0 +/- 1.0 SPHEROIDAL, LSB DEC=+25D06'54.72" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 17484( 3) - 19-Sep-2023 14:37:24 - [ 4] Visit: 01 (CANDIDATE-1) Visit Requirements: ORIENT 0D TO 90 D; ORIENT 230D TO 359.9 D 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 CANDIDATE-1 ACS/WFC ACCUM WFC1 F606W 1 500 S (500 PAR 3 WITH 1-2 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 CANDIDATE-1 ACS/WFC ACCUM WFC1 F814W 1 500 S (500 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 ANY WFC3/UVI ACCUM UVIS-CENT F606W 1 1200 S S ER (1200 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 CANDIDATE-1 ACS/WFC ACCUM WFC1 F814W 1 496 S (496 POS TARG 0.246, 0.267; S) PAR 6 WITH 4-5 ------------------------------------------------------------------------------------------------------------------------------------ 5 CANDIDATE-1 ACS/WFC ACCUM WFC1 F606W 1 496 S (496 POS TARG 0.246, 0.267 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 ANY WFC3/UVI ACCUM UVIS-CENT F814W 1 1200 S S ER (1200 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 | ------------------------------------------------------------------------------------------------------------------------------------ CANDIDATE-1 1 ACS/WFC ACCUM WFC1 F606W none none none none 1 N/A CANDIDATE-1 2 ACS/WFC ACCUM WFC1 F814W none none none none 1 N/A ANY 3 WFC3/UVI ACCUM UVIS-CEN F606W none none none none 1 N/A S TER CANDIDATE-1 4 ACS/WFC ACCUM WFC1 F814W none none none none 1 N/A CANDIDATE-1 5 ACS/WFC ACCUM WFC1 F606W none none none none 1 N/A ANY 6 WFC3/UVI ACCUM UVIS-CEN F814W none none none none 1 N/A S TER 17484( 3) - 19-Sep-2023 14:37:24 - [ 5] Visit: 02 (CANDIDATE-2) 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 CANDIDATE-2 ACS/WFC ACCUM WFC1 F606W 1 500 S (500 POS TARG 0, 0; PAR 3 S) WITH 1-2 ------------------------------------------------------------------------------------------------------------------------------------ 2 CANDIDATE-2 ACS/WFC ACCUM WFC1 F814W 1 500 S (500 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 ANY WFC3/UVI ACCUM UVIS-CENT F606W 1 1200 S S ER (1200 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 CANDIDATE-2 ACS/WFC ACCUM WFC1 F814W 1 498 S (498 POS TARG 0.246, 0.267; S) PAR 6 WITH 4-5 ------------------------------------------------------------------------------------------------------------------------------------ 5 CANDIDATE-2 ACS/WFC ACCUM WFC1 F606W 1 498 S (498 POS TARG 0.246, 0.267 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 ANY WFC3/UVI ACCUM UVIS-CENT F814W 1 1200 S S ER (1200 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 | ------------------------------------------------------------------------------------------------------------------------------------ CANDIDATE-2 1 ACS/WFC ACCUM WFC1 F606W none none none none 1 N/A CANDIDATE-2 2 ACS/WFC ACCUM WFC1 F814W none none none none 1 N/A ANY 3 WFC3/UVI ACCUM UVIS-CEN F606W none none none none 1 N/A S TER CANDIDATE-2 4 ACS/WFC ACCUM WFC1 F814W none none none none 1 N/A CANDIDATE-2 5 ACS/WFC ACCUM WFC1 F606W none none none none 1 N/A ANY 6 WFC3/UVI ACCUM UVIS-CEN F814W none none none none 1 N/A S TER 17484( 3) - 19-Sep-2023 14:37:24 - [ 6] Summary Form for Proposal 17484 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS-CENTER, WFC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 0D TO 90 D, ORIENT 230D TO 359.9 D, PAR 3 WITH 1-2, PAR 6 WITH 4-5, POS TARG 0, 0, POS TARG 0.246, 0.267 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names ANY, CANDIDATE-1, CANDIDATE-2 ------------------------------------------------------------------------------------------------------------------------------------