16293 (Stsci Edit Number: 1, Created: Thursday, July 16, 2020 at 5:01:03 PM Eastern Standard Time) - Overview

Proposal 16293 (STScI Edit Number: 1, Created: Thursday, July 16, 2020 at 5:01:03 PM Eastern Standard Time) - Overview

16293 - Near Field Cosmology with Ultra-faint Dwarfs: Patchy Reionization and Sub-Solar Initial Mass Function Cycle: 28, Proposal Category: GO (Availability Mode: SUPPORTED)

INVESTIGATORS Name Institution E-Mail Dr. Yumi Choi (PI) (Contact) Space Telescope Science Institute [email protected] Dr. Gurtina Besla (CoI) University of Arizona [email protected] Dr. Nitya Kallivayalil (CoI) The University of Virginia [email protected] Dr. Myoungwon Jeon (CoI) Kyung Hee University [email protected] Dr. David Nidever (CoI) Montana State University - Bozeman [email protected] Dr. Ekta Patel (CoI) University of California - Berkeley [email protected] Dr. Daniel R. Weisz (CoI) University of California - Berkeley [email protected] Dr. Benjamin F. Williams (CoI) University of Washington [email protected] Dr. Julianne Dalcanton (CoI) University of Washington [email protected] Dr. Andrew Pace (CoI) Carnegie Mellon University [email protected] Dr. Ting Li (CoI) Carnegie Institution of Washington [email protected] Dr. Joshua D. Simon (CoI) Carnegie Institution of Washington [email protected] Prof. Andrew Wetzel (CoI) University of California - Davis [email protected] Dr. Elena Sacchi (CoI) Space Telescope Science Institute [email protected] Dr. Roeland P. van der Marel (CoI) Space Telescope Science Institute [email protected] Dr. Sangmo Tony Sohn (CoI) Space Telescope Science Institute [email protected] Ms. Hannah Richstein (CoI) The University of Virginia [email protected] Mr. Paul Zivick (CoI) The University of Virginia [email protected]

1 Proposal 16293 (STScI Edit Number: 1, Created: Thursday, July 16, 2020 at 5:01:03 PM Eastern Standard Time) - Overview VISITS Visit Targets used in Visit Configurations used in Visit Orbits Used Last Orbit Planner Run OP Current with Visit? 01 (1) CARINA2-1 ACS/WFC 1 16-Jul-2020 18:00:58.0 yes ANY WFC3/UVIS 02 (2) CARINA2-2 ACS/WFC 1 16-Jul-2020 18:00:59.0 yes ANY WFC3/UVIS 03 (3) CARINA2-3 ACS/WFC 1 16-Jul-2020 18:01:00.0 yes ANY WFC3/UVIS 04 (5) HYDRUS1-1 ACS/WFC 1 16-Jul-2020 18:01:02.0 yes ANY WFC3/UVIS 05 (6) HYDRUS1-2 ACS/WFC 1 16-Jul-2020 18:01:03.0 yes ANY WFC3/UVIS 5 Total Orbits Used

ABSTRACT Observations of the ultra-faint dwarfs (UFDs), as relics of the epoch of reionization, allow us to probe the earliest epochs of star formation (SF). In particular, the UFDs in low density environments for most of their lifetimes provide unique tools to probe the effects of early environmental conditions on the SF histories (SFHs) of the UFDs and their sub-solar initial mass function (IMF) because they likely maintain the best `fossil' record of early local environments.

We propose to obtain deep ACS and UVIS imaging in F606W and F814W for 2 LMC satellite UFDs that are on their first approach to our Galaxy, and thus resided in the outskirts of the Local Group at high redshift. This program is designed to identify systematic differences in the stellar populations of recently captured UFDs vs. long-term MW satellites (data available from previous programs) by using high-fidelity color-magnitude diagrams constructed from deep HST imaging as well as spectroscopically measured metallicity distribution functions. We will: (1) Establish whether SF is quenched at different times with different rate in UFDs in low density environment at early times, probing the patchiness of reionization by directly comparing with theoretical predictions; (2) Identify variations in the sub-Solar IMF across UFDs born in different environments; (3) Pave the way for a more accurate constraint on the MW halo mass.

2 Proposal 16293 (STScI Edit Number: 1, Created: Thursday, July 16, 2020 at 5:01:03 PM Eastern Standard Time) - Overview

OBSERVING DESCRIPTION Our basic observing strategy is to reach S/N of > 100 at the oMSTO in F606W and F814W filters in ACS/WFC, allowing us to measure the detailed ancient SFHs and to explore the sub-Solar (down to a half solar) stellar IMF. Both Carina 2 and Hydrus 1 have half-light radii greater than the ACS FOV, and thus we add an extra one pointing for Hydrus 1 and two pointings for Carina 2 with parallel observations with WFC3/UVIS to observe sufficient number of member stars in each galaxy.

Each pointing is made up of 2 dithered F606W exposures, and 2 dithered F814W exposures to eliminate hot pixels and CR hits in the combined images. We need two filter data to make CMDs to measure SFHs and to separate target stars from foreground/background contaminants. Our choice of filters (F606W and F814W) is the same as previous SFH programs of MW satellites, enabling us to use stellar population templates observed in these same filters to minimize systematic errors for relative ages when comparing populations and thus facilitating direct comparison with other MW satellites from previous programs. The depth of our data will be comparable to ohter HST observations used for MW satellites' sub-solar IMF studies.

3 Proposal 16293-CARINA2-1(01)NearFieldCosmologywithUltra-faintDwarfs:Patchy ReionizationandSub-SolarInitialMassFun... Exposures Fixed Targets Diagnostics Visit 8 7 6 5 4 3 2 1 # Extended=NO Description=[DWARF SPHEROIDAL] Category=GALAXY Comments: (1) # (Parallel Exposure8(Prime+ParallelGroup7-8inCARINA2-1(01)))Warning (Form):FLASHlevelmaybetoohighforthisexposureoralongsubexposure.Seeextendedexplanationinthediagnosticbrowser (Parallel Exposure2(Prime+ParallelGroup1-2inCARINA2-1(01)))Warning(Form):FLASHlevelmaybetoohighforthisexposureoralong subexposure.Seeextendedexplanationinthediagnosticbrowser Special Requirements:ORIENT0DTO65D;140D245320D359.999D Scientific Instruments:WFC3/UVIS,ACS/WFC Diagnostic Status:Warning Proposal 16293,CARINA2-1(01),implementation Label CARINA2-1 Name (1) CARINA2-1 ANY (1) CARINA2-1 Target ANY (1) CARINA2-1 ANY (1) CARINA2-1 ANY Equinox: J2000 Dec: -580044.15(-58.01226d) RA: 073639.5502(114.1647925d) Target Coordinates WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC Config,Mode,Aperture F814W F606W F606W F606W F606W Spectral Els. F814W F814W F814W Targ. Coord.Corrections CR-SPLIT=NO CR-SPLIT=NO CR-SPLIT=NO FLASH=2 CR-SPLIT=NO; CR-SPLIT=NO Opt. Params. FLASH=13 CR-SPLIT=NO; CR-SPLIT=NO CR-SPLIT=NO 4 984 POS TARG0.247,2. 984 POS TARG0.247,2. POS TARG0,0 Special Reqs. POS TARG0,0 V=-4.5+/-0.1 Fluxes 1 (01) up 7-8inCARINA2- Prime +ParallelGro 1 (01) up 7-8inCARINA2- Prime +ParallelGro 1 (01) up 5-6inCARINA2- Prime +ParallelGro 1 (01) up 5-6inCARINA2- Prime +ParallelGro 1 (01) up 3-4inCARINA2- Prime +ParallelGro 1 (01) up 3-4inCARINA2- Prime +ParallelGro 1 (01) up 1-2inCARINA2- Prime +ParallelGro 1 (01) up 1-2inCARINA2- Prime +ParallelGro Groups [==>] 345 Secs(345Secs) [==>351.0 Secs] 345 Secs(351Secs) [==>792.0 Secs] 750 Secs(792Secs) [==>756.0 Secs] 750 Secs(756Secs) [==>766.0 Secs] 750 Secs(766Secs) [==>756.0 Secs] 750 Secs(756Secs) [==>456.0 Secs] 400 Secs(456Secs) [==>406.0 Secs] 400 Secs(406Secs) Exp. Time(Total)/[ActualDur.] Reference Frame:ICRS Miscellaneous Thu Jul1622:01:03GMT2020 Orbit [1] [1] [1] [1] [1] [1] [1] [1] Proposal 16293-CARINA2-1(01)NearFieldCosmologywithUltra-faintDwarfs:Patchy ReionizationandSub-SolarInitialMassFun... Orbit Structure 5 Proposal 16293-CARINA2-2(02)NearFieldCosmologywithUltra-faintDwarfs:Patchy ReionizationandSub-SolarInitialMassFun... Exposures Fixed Targets Diagnostics Visit 8 7 6 5 4 3 2 1 # Description=[DWARF SPHEROIDAL] Category=GALAXY Comments: (2) # (Parallel Exposure8(Prime+ParallelGroup7-8inCARINA2-2(02)))Warning (Form):FLASHlevelmaybetoohighforthisexposureoralongsubexposure.Seeextendedexplanationinthediagnosticbrowser (Parallel Exposure2(Prime+ParallelGroup1-2inCARINA2-2(02)))Warning(Form):FLASHlevelmaybetoohighforthisexposureoralong subexposure.Seeextendedexplanationinthediagnosticbrowser Special Requirements:SAMEORIENTAS01 Scientific Instruments:WFC3/UVIS,ACS/WFC Diagnostic Status:Warning Proposal 16293,CARINA2-2(02),implementation Label CARINA2-2 Name (2) CARINA2-2 ANY (2) CARINA2-2 Target ANY (2) CARINA2-2 ANY (2) CARINA2-2 ANY Equinox: J2000 Dec: -575742.12(-57.96170d) RA: 073624.9822(114.1040925d) Target Coordinates WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC Config,Mode,Aperture F814W F606W F606W F606W F606W Spectral Els. F814W F814W F814W Targ. Coord.Corrections CR-SPLIT=NO CR-SPLIT=NO CR-SPLIT=NO FLASH=2 CR-SPLIT=NO; CR-SPLIT=NO Opt. Params. FLASH=13 CR-SPLIT=NO; CR-SPLIT=NO CR-SPLIT=NO 6 984 POS TARG0.247,2. 984 POS TARG0.247,2. POS TARG0,0 Special Reqs. POS TARG0,0 V=-4.5+/-0.1 Fluxes 2 (02) up 7-8inCARINA2- Prime +ParallelGro 2 (02) up 7-8inCARINA2- Prime +ParallelGro 2 (02) up 5-6inCARINA2- Prime +ParallelGro 2 (02) up 5-6inCARINA2- Prime +ParallelGro 2 (02) up 3-4inCARINA2- Prime +ParallelGro 2 (02) up 3-4inCARINA2- Prime +ParallelGro 2 (02) up 1-2inCARINA2- Prime +ParallelGro 2 (02) up 1-2inCARINA2- Prime +ParallelGro Groups [==>] 345 Secs(345Secs) [==>351.0 Secs] 345 Secs(351Secs) [==>792.0 Secs] 750 Secs(792Secs) [==>756.0 Secs] 750 Secs(756Secs) [==>766.0 Secs] 750 Secs(766Secs) [==>756.0 Secs] 750 Secs(756Secs) [==>456.0 Secs] 400 Secs(456Secs) [==>406.0 Secs] 400 Secs(406Secs) Exp. Time(Total)/[ActualDur.] Reference Frame:ICRS Miscellaneous Thu Jul1622:01:04GMT2020 Orbit [1] [1] [1] [1] [1] [1] [1] [1] Proposal 16293-CARINA2-2(02)NearFieldCosmologywithUltra-faintDwarfs:Patchy ReionizationandSub-SolarInitialMassFun... Orbit Structure 7 Proposal 16293-CARINA2-3(03)NearFieldCosmologywithUltra-faintDwarfs:Patchy ReionizationandSub-SolarInitialMassFun... Exposures Fixed Targets Diagnostics Visit 8 7 6 5 4 3 2 1 # Description=[DWARF SPHEROIDAL] Category=GALAXY Comments: (3) # (Parallel Exposure8(Prime+ParallelGroup7-8inCARINA2-3(03)))Warning (Form):FLASHlevelmaybetoohighforthisexposureoralongsubexposure.Seeextendedexplanationinthediagnosticbrowser (Parallel Exposure2(Prime+ParallelGroup1-2inCARINA2-3(03)))Warning(Form):FLASHlevelmaybetoohighforthisexposureoralong subexposure.Seeextendedexplanationinthediagnosticbrowser Special Requirements:SAMEORIENTAS01 Scientific Instruments:WFC3/UVIS,ACS/WFC Diagnostic Status:Warning Proposal 16293,CARINA2-3(03),implementation Label CARINA2-3 Name (3) CARINA2-3 ANY (3) CARINA2-3 Target ANY (3) CARINA2-3 ANY (3) CARINA2-3 ANY Equinox: J2000 Dec: -575456.26(-57.91563d) RA: 073613.9799(114.0582496d) Target Coordinates WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC Config,Mode,Aperture F814W F606W F606W F606W F606W Spectral Els. F814W F814W F814W Targ. Coord.Corrections CR-SPLIT=NO CR-SPLIT=NO CR-SPLIT=NO FLASH=2 CR-SPLIT=NO; CR-SPLIT=NO Opt. Params. FLASH=13 CR-SPLIT=NO; CR-SPLIT=NO CR-SPLIT=NO 8 984 POS TARG0.247,2. 984 POS TARG0.247,2. POS TARG0,0 Special Reqs. POS TARG0,0 V=-4.5+/-0.1 Fluxes 3 (03) up 7-8inCARINA2- Prime +ParallelGro 3 (03) up 7-8inCARINA2- Prime +ParallelGro 3 (03) up 5-6inCARINA2- Prime +ParallelGro 3 (03) up 5-6inCARINA2- Prime +ParallelGro 3 (03) up 3-4inCARINA2- Prime +ParallelGro 3 (03) up 3-4inCARINA2- Prime +ParallelGro 3 (03) up 1-2inCARINA2- Prime +ParallelGro 3 (03) up 1-2inCARINA2- Prime +ParallelGro Groups [==>] 345 Secs(345Secs) [==>351.0 Secs] 345 Secs(351Secs) [==>792.0 Secs] 750 Secs(792Secs) [==>756.0 Secs] 750 Secs(756Secs) [==>766.0 Secs] 750 Secs(766Secs) [==>756.0 Secs] 750 Secs(756Secs) [==>456.0 Secs] 400 Secs(456Secs) [==>406.0 Secs] 400 Secs(406Secs) Exp. Time(Total)/[ActualDur.] Reference Frame:ICRS Miscellaneous Thu Jul1622:01:04GMT2020 Orbit [1] [1] [1] [1] [1] [1] [1] [1] Proposal 16293-CARINA2-3(03)NearFieldCosmologywithUltra-faintDwarfs:Patchy ReionizationandSub-SolarInitialMassFun... Orbit Structure 9 Proposal 16293-Hydrus1-1(04)NearFieldCosmologywithUltra-faintDwarfs:Patchy ReionizationandSub-SolarInitialMassFunc... Exposures Fixed Targets Diagnostics Visit 8 7 6 5 4 3 2 1 # Description=[DWARF SPHEROIDAL] Category=GALAXY Comments: (5) # (Parallel Exposure8(Prime+ParallelGroup7-8inHydrus1-1(04)))Warning (Form):FLASHlevelmaybetoohighforthisexposureoralongsubexposure.Seeextendedexplanationinthediagnosticbrowser (Parallel Exposure2(Prime+ParallelGroup1-2inHydrus1-1(04)))Warning(Form):FLASHlevelmaybetoohighforthisexposureoralong subexposure. Seeextendedexplanationinthediagnosticbrowser Special Requirements:(none) Scientific Instruments:WFC3/UVIS,ACS/WFC Diagnostic Status:Warning Proposal 16293,Hydrus1-1(04),implementation Label HYDRUS1-1 Name (5) HYDRUS1-1 ANY (5) HYDRUS1-1 Target ANY (5) HYDRUS1-1 ANY (5) HYDRUS1-1 ANY Equinox: J2000 Dec: -791814.99(-79.30416d) RA: 02307.7856(37.5324400d) Target Coordinates WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC Config,Mode,Aperture F814W F606W F606W F606W F606W Spectral Els. F814W F814W F814W Targ. Coord.Corrections FLASH=6 Opt. Params. FLASH=9 10 984 POS TARG0.247,2. 984 POS TARG0.247,2. POS TARG0,0 Special Reqs. POS TARG0,0 V=-4.71+/-0.08 Fluxes (04) up 7-8inHydrus1-1 Prime +ParallelGro (04) up 7-8inHydrus1-1 Prime +ParallelGro (04) up 5-6inHydrus1-1 Prime +ParallelGro (04) up 5-6inHydrus1-1 Prime +ParallelGro (04) up 3-4inHydrus1-1 Prime +ParallelGro (04) up 3-4inHydrus1-1 Prime +ParallelGro (04) up 1-2inHydrus1-1 Prime +ParallelGro (04) up 1-2inHydrus1-1 Prime +ParallelGro Groups [==>] 500 Secs(500Secs) [==>499.0 Secs] 500 Secs(499Secs) [==>841.0 Secs] 800 Secs(841Secs) [==>799.0 Secs] 800 Secs(799Secs) [==>] 800 Secs(800Secs) [==>799.0 Secs] 800 Secs(799Secs) [==>356.0 Secs] 303 Secs(356Secs) [==>302.0 Secs] 303 Secs(302Secs) Exp. Time(Total)/[ActualDur.] Reference Frame:ICRS Miscellaneous Thu Jul1622:01:04GMT2020 Orbit [1] [1] [1] [1] [1] [1] [1] [1] Proposal 16293-Hydrus1-1(04)NearFieldCosmologywithUltra-faintDwarfs:Patchy ReionizationandSub-SolarInitialMassFunc... Orbit Structure 11 Proposal 16293-Hydrus1-2(05)NearFieldCosmologywithUltra-faintDwarfs:Patchy ReionizationandSub-SolarInitialMassFunc... Exposures Fixed Targets Diagnostics Visit 8 7 6 5 4 3 2 1 # Description=[DWARF SPHEROIDAL] Category=GALAXY Comments: (6) # (Parallel Exposure8(Prime+ParallelGroup7-8inHydrus1-2(05)))Warning (Form):FLASHlevelmaybetoohighforthisexposureoralongsubexposure.Seeextendedexplanationinthediagnosticbrowser (Parallel Exposure2(Prime+ParallelGroup1-2inHydrus1-2(05)))Warning(Form):FLASHlevelmaybetoohighforthisexposureoralong subexposure. Seeextendedexplanationinthediagnosticbrowser Special Requirements:SAMEORIENTAS04 Scientific Instruments:WFC3/UVIS,ACS/WFC Diagnostic Status:Warning Proposal 16293,Hydrus1-2(05),implementation Label HYDRUS1-2 Name (6) HYDRUS1-2 ANY (6) HYDRUS1-2 Target ANY (6) HYDRUS1-2 ANY (6) HYDRUS1-2 ANY Equinox: J2000 Dec: -791652.07(-79.28113d) RA: 022856.2561(37.2344004d) Target Coordinates WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC WFC3/UVIS, ACCUM,UVIS ACS/WFC, ACCUM,WFC Config,Mode,Aperture F814W F606W F606W F606W F606W Spectral Els. F814W F814W F814W Targ. Coord.Corrections FLASH=9 Opt. Params. FLASH=9 12 984 POS TARG0.247,2. 984 POS TARG0.247,2. POS TARG0,0 Special Reqs. POS TARG0,0 V=-4.71+/-0.08 Fluxes (05) up 7-8inHydrus1-2 Prime +ParallelGro (05) up 7-8inHydrus1-2 Prime +ParallelGro (05) up 5-6inHydrus1-2 Prime +ParallelGro (05) up 5-6inHydrus1-2 Prime +ParallelGro (05) up 3-4inHydrus1-2 Prime +ParallelGro (05) up 3-4inHydrus1-2 Prime +ParallelGro (05) up 1-2inHydrus1-2 Prime +ParallelGro (05) up 1-2inHydrus1-2 Prime +ParallelGro Groups [==>] 499 Secs(499Secs) [==>] 499 Secs(499Secs) [==>842.0 Secs] 700 Secs(842Secs) [==>] 800 Secs(800Secs) [==>810.0 Secs] 700 Secs(810Secs) [==>] 800 Secs(800Secs) [==>354.0 Secs] 300 Secs(354Secs) [==>] 300 Secs(300Secs) Exp. Time(Total)/[ActualDur.] Reference Frame:ICRS Miscellaneous Thu Jul1622:01:04GMT2020 Orbit [1] [1] [1] [1] [1] [1] [1] [1] Proposal 16293-Hydrus1-2(05)NearFieldCosmologywithUltra-faintDwarfs:Patchy ReionizationandSub-SolarInitialMassFunc... Orbit Structure 13