15228( 6) - 18-Dec-2018 13:44:29 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15228 Version: 6 Check-in Time: 18-Dec-2018 13:44:29 STScI Edit Number: 1 Title Testing Galaxy Evolution in Unexplored Environments: the First Faint Dwarf Satellites of Local Volume LMC Analogs ------------------------------------------------------------------------------------ Type Cycle GO 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Jeffrey L Carlin LSST Y CoI: Dr. Denija Crnojevic Texas Tech University N CoI: Dr. Jonathan Hargis Space Telescope Science Institute N CoI: Prof. David J. Sand University of Arizona N CoI: Dr. Beth Willman LSST N ------------------------------------------------------------------------------------ Abstract We propose to use four HST/ACS orbits to obtain follow-up imaging and resolved photometry of two candidate dwarf galaxies in the halos of Local Volume LMC analogs, which have been discovered as part of our ground-based MADCASH survey: MADCASH-1, which is a satellite of NGC 2403 (D = 3.2 Mpc), and MADCASH-2, near NGC 4214 (D = 2.9 Mpc). These are the faintest dwarf satellites known around host galaxies of Large Magellanic Cloud stellar mass outside the Local Group. We will measure accurate TRGB distances to confirm their associations with their host galaxies, derive their structural parameters, and assess their stellar populations. These two dwarf galaxies, the first of their kind around LMC analogs, are vital probes of dwarf evolution in different environments. Both of these MADCASH dwarfs are at luminosities intermediate between the "classical" Milky Way dwarf galaxies and the "ultra-faint" dwarfs. The proposed observations will resolve individual stars in these systems of small angular size, allowing us to quantify the relative presence of ancient stellar populations and younger, more metal-enriched stars, and to measure their physical properties. We will compare these to the Milky Way classical and ultra-faint dwarfs to place these systems in a broader context and assess similarities or differences between these "dwarfs around dwarfs" and Local Group satellites. ------------------------------------------------------------------------------------ Observations Description ------------------------ Our observing strategy is to obtain deep imaging in two filters (ACS/WFC F606W and F814W) in order to (a) confirm the association of two new dwarf galaxies (MADCASH-1 and MADCASH-2) with their putative LMC-analog hosts via accurate TRGB distances, (b) assess their stellar populations and star formation histories, and (c) derive their structural parameters (size, luminosity, ellipticity, and position angle) via resolved photometry. To accomplish these goals, we require deep, precise photometry with S/N~5 at least 2 magnitudes below the RGB tip in the target galaxies. Our choices of filters and exposure times are motivated by numerous studies and HST programs similar to ours (e.g., Williams et al. 2013, Dalcanton et al. 2009, Radburn-Smith et al. 2011). For low metallicity systems, the TRGB can be easily distinguished (using, e.g., a Sobel edge detection filter) due to the quick cutoff at M_I = -4.0 mag if the imaging in the I band (F814W) is sufficiently deep. The use of the V band 15228( 6) - 18-Dec-2018 13:44:29 - [ 2] (F606W) allows us to minimize galaxy contamination using photometric colors, and to use the detected member stars of each galaxy to assess their stellar populations and derive their structural parameters. We will use one orbit per filter per target galaxy, splitting the observing time into exposures of 1415/1272 sec (for MADCASH-1/MADCASH-2) in F606W and 1484/1341 sec in F814W, requiring a total of 4 HST orbits. Each exposure will be split into a two-line dither pattern to cover the ACS/WFC chip gap and facilitate cosmic ray removal. Each of the two galaxy candidates is small enough to fit onto one of the ACS/WFC chips, and given the lack of nearby bright stars, any HST orientation angle is sufficient for observing these targets. However, for MADCASH-1, we have placed limitations on the orientation in order to avoid placing nearby very bright stars onto the WFC3/UVIS chip during parallel observations. Our requested parallel observations with WFC3/UVIS will obtain neighboring fields from which we will assess the contribution of background sources. We note that these filters are similar to the g- and i-band filters we are using for our Subaru/HSC survey. These proposed parallel observations will thus provide an ancillary benefit by allowing us to use the deeper, higher-resolution HST data in regions of the WFC3/UVIS field of view well beyond our dwarf galaxy targets to assess the veracity of our star/galaxy classification in the ground-based MADCASH imaging, and improve our techniques in order to reduce the contamination from unresolved background galaxies. ------------------------------------------------------------------------------------ 15228( 6) - 18-Dec-2018 13:44:29 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 MADCASH-1 GALAXY, DWARF RA=07H42M38.8870S +/- 2.6", J2000 V = 20.0 +/- 0.7 SPHEROIDAL DEC=+65D25'1.89" +/- 3.2" Reference Frame: ICRS Comments: Note: V~20 is the total integrated magnitude of the dwarf galaxy. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.0 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 2 MADCASH-2 GALAXY, DWARF RA=12H10M6.7230S +/- 3.5", J2000 V = 19 +/- 1 SPHEROIDAL DEC=+35D26'36.29" +/- 3.5" Reference Frame: ICRS Comments: Note: V~19 is the total integrated magnitude of the dwarf galaxy. ------------------------------------------------------------------------------------------------------------------------------------ 15228( 6) - 18-Dec-2018 13:44:29 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 3.034 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 85.29 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 15228( 6) - 18-Dec-2018 13:44:29 - [ 5] Visit: 01 (MADCASH-1) Visit Requirements: ORIENT 140D TO 360 D; ORIENT 60D TO 85 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 MADCASH-1 ACS/WFC ACCUM WFC1 F606W 1 453 S PATTERN 1 1-2; PAR 2 see below WITH 1 (2475 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFC3/UVI ACCUM UVIS F606W 1 500 S S see below (2630 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 MADCASH-1 ACS/WFC ACCUM WFC1 F814W 1 500 S PATTERN 1 3-4; PAR 4 see below WITH 3 (2645 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFC3/UVI ACCUM UVIS F814W 1 510 S S see below (2720 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 | ------------------------------------------------------------------------------------------------------------------------------------ MADCASH-1 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 500.0 S MADCASH-1 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 650.0 S MADCASH-1 1 ACS/WFC ACCUM WFC1 F606W 3 none none none 1 650.0 S MADCASH-1 1 ACS/WFC ACCUM WFC1 F606W 4 none none none 1 675.0 S ANY 2 WFC3/UVI ACCUM UVIS F606W 1 none none none 1 580.0 S S ANY 2 WFC3/UVI ACCUM UVIS F606W 2 none none none 1 700.0 S S ANY 2 WFC3/UVI ACCUM UVIS F606W 3 none none none 1 700.0 S S ANY 2 WFC3/UVI ACCUM UVIS F606W 4 none none none 1 650.0 S S MADCASH-1 3 ACS/WFC ACCUM WFC1 F814W 1 none none none 2 470.0 S MADCASH-1 3 ACS/WFC ACCUM WFC1 F814W 2 none none none 2 725.0 S MADCASH-1 3 ACS/WFC ACCUM WFC1 F814W 3 none none none 2 725.0 S MADCASH-1 3 ACS/WFC ACCUM WFC1 F814W 4 none none none 2 725.0 S ANY 4 WFC3/UVI ACCUM UVIS F814W 1 none none none 2 530.0 S S ANY 4 WFC3/UVI ACCUM UVIS F814W 2 none none none 2 730.0 S S 15228( 6) - 18-Dec-2018 13:44:29 - [ 6] 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 | ------------------------------------------------------------------------------------------------------------------------------------ ANY 4 WFC3/UVI ACCUM UVIS F814W 3 none none none 2 730.0 S S ANY 4 WFC3/UVI ACCUM UVIS F814W 4 none none none 2 730.0 S S 15228( 6) - 18-Dec-2018 13:44:29 - [ 7] Visit: 02 (MADCASH-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 MADCASH-2 ACS/WFC ACCUM WFC1 F606W 1 394 S PATTERN 1 1-2; PAR 2 see below WITH 1 (2160 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFC3/UVI ACCUM UVIS F606W 1 405 S S see below (2390 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 MADCASH-2 ACS/WFC ACCUM WFC1 F814W 1 428 S PATTERN 1 3-4; PAR 4 see below WITH 3 (2200 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFC3/UVI ACCUM UVIS F814W 1 446 S S see below (2478 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 | ------------------------------------------------------------------------------------------------------------------------------------ MADCASH-2 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 390.0 S MADCASH-2 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 690.0 S MADCASH-2 1 ACS/WFC ACCUM WFC1 F606W 3 none none none 1 690.0 S MADCASH-2 1 ACS/WFC ACCUM WFC1 F606W 4 none none none 1 390.0 S ANY 2 WFC3/UVI ACCUM UVIS F606W 1 none none none 1 450.0 S S ANY 2 WFC3/UVI ACCUM UVIS F606W 2 none none none 1 720.0 S S ANY 2 WFC3/UVI ACCUM UVIS F606W 3 none none none 1 720.0 S S ANY 2 WFC3/UVI ACCUM UVIS F606W 4 none none none 1 500.0 S S MADCASH-2 3 ACS/WFC ACCUM WFC1 F814W 1 none none none 2 435.0 S MADCASH-2 3 ACS/WFC ACCUM WFC1 F814W 2 none none none 2 665.0 S MADCASH-2 3 ACS/WFC ACCUM WFC1 F814W 3 none none none 2 665.0 S MADCASH-2 3 ACS/WFC ACCUM WFC1 F814W 4 none none none 2 435.0 S ANY 4 WFC3/UVI ACCUM UVIS F814W 1 none none none 2 500.0 S S ANY 4 WFC3/UVI ACCUM UVIS F814W 2 none none none 2 700.0 S S 15228( 6) - 18-Dec-2018 13:44:29 - [ 8] 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 | ------------------------------------------------------------------------------------------------------------------------------------ ANY 4 WFC3/UVI ACCUM UVIS F814W 3 none none none 2 700.0 S S ANY 4 WFC3/UVI ACCUM UVIS F814W 4 none none none 2 578.0 S S 15228( 6) - 18-Dec-2018 13:44:29 - [ 9] Summary Form for Proposal 15228 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS, WFC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 140D TO 360 D, ORIENT 60D TO 85 D, PAR 2 WITH 1, PAR 4 WITH 3, PATTERN 1 1-2, PATTERN 1 3-4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names ANY, MADCASH-1, MADCASH-2 ------------------------------------------------------------------------------------------------------------------------------------