15858( 3) - 24-Sep-2019 13:48:15 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15858 Version: 3 Check-in Time: 24-Sep-2019 13:48:15 STScI Edit Number: 0 Title The Satellite Luminosity Function of M101 into the Ultra-Faint Dwarf Galaxy Regime ------------------------------------------------------------------------------------ Type Cycle GO 27 ------------------------------------------------------------------------------------ Investigators Contact? PI: Mr. Paul Bennet Texas Tech University Y CoI: Dr. Denija Crnojevic University of Tampa N CoI: Prof. David J. Sand University of Arizona N CoI: Dr. Kristine Spekkens Royal Military College of Canada N CoI: Prof. Dennis Zaritsky University of Arizona N CoI: Ananthan Karunakaran Queen's University N ------------------------------------------------------------------------------------ Abstract We request 4 orbits of HST/ACS to image, in resolved stellar light, four diffuse dwarf candidates that recent tentative distance measurements (using the surface brightness fluctuation technique) indicate may be associated with M101, a Milky Way analog at D=7 Mpc. These four dwarfs are the only remaining viable satellites of M101 down to M_V ~ -7 mag, out of a complete sample drawn from a semi-automated ground-based search which conducted extensive simulations to assess the efficiency in their detection. This dataset will allow us to measure tip of the red giant branch (TRGB) distances, luminosities and structural parameters for these dwarfs, and will result in a complete satellite luminosity function for M101 out to a galacocentric radius of 150 kpc and down to the ultra-faint dwarf galaxy regime (M_V ~ -7 mag). Such a complete luminosity function has been only obtained for the Local Group to date. The current M101 satellite system is very sparse in comparison to the Milky Way, M31 and cosmological simulations, and a confirmation of its properties will provide additional constraints on Cold Dark Matter predictions at these small galaxy scales. ------------------------------------------------------------------------------------ Observations Description ------------------------ The observations are going to be performed with ACS/WFC (primary) and WFC3/UVIS (parallel). We request imaging in F606W and F814W filters (broad V and I) for both instruments, in order to compute accurate TRGB distances for our targets and characterize their stellar content (star formation histories and metallicities), while optimizing the exposure times. The parallel pointings will allow us to observe a field region next to our targets. We will thus be able to estimate more precisely the number of background/foreground contaminants present in our ACS fields. Our goal is to obtain a SNR of ~5 at ~1 mag below the TRGB in I band, assuming that the TRGB is found at M_I = ~-4.0 and M_V = ~-2.5, in order to derive precise distance measurements, structural properties and average metallicities. With the requested SNR, we will obtain distance uncertainties as low as ~0.2 mag, corresponding to ~200 kpc at the distance of M101. We stress that, even for the faintest of our targets we expect ~25 stars in the upper 1 mag below 15858( 3) - 24-Sep-2019 13:48:15 - [ 2] the TRGB. Since the exact distances for our targets are unknown, the candidate M101 satellites are assumed to be at the distance of M101 (~7 Mpc). Given their low masses, these are expected to be metal-poor objects, thus having average colours of V - I ~ 1.5. At this distance, the TRGB is found at a magnitude of I ~ 25.2 and V ~ 25.9. The exposures to obtain the required SNR at 1 mag below the TRGB for both bands are ~ 1200 sec in F606W and ~ 900 sec in F814W (as computed with the latest version of the ACS ETC), which result in one orbit per target. Each exposure will be split in two with a dither pattern in order to subsequently remove detector defects and improve the PSF sampling. We have checked that the charge transfer efficiency losses of ACS do not significantly affect our observations (at most 10% loss of flux). This program is resilient to two-gyro mode, we believe. Our visits are 1-orbit, and we have no ORIENT requirements. Nor does this program have time constraints (other than the baseline excitement of the science!). We can also achieve our science goals with a longer acquisition time, if necessary. ------------------------------------------------------------------------------------ 15858( 3) - 24-Sep-2019 13:48:15 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 M101-DW21 GALAXY, DWARF RA=14H07M56.5000S, J2000 V = 21.3 +/- 0.2 SPHEROIDAL DEC=+54D56'3.00" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 2 M101-DW22 GALAXY, DWARF RA=14H03M3.3000S, J2000 V = 21.0 +/- 0.1 SPHEROIDAL DEC=+54D47'12.00" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 3 M101-DW23 GALAXY, DWARF RA=14H07M8.4000S, J2000 V = 21.2 +/- 0.5 SPHEROIDAL DEC=+54D33'49.00" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 4 M101-DW35 GALAXY, DWARF RA=14H05M36.2000S, J2000 V = 21.8 +/- 0.2 SPHEROIDAL DEC=+54D49'2.00" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 15858( 3) - 24-Sep-2019 13:48:15 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.364 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 47.23 Angle_Between_Sides Center_Pattern NO Pattern_Comments: Two-point dither. No need to fill chip gap. ------------------------------------------------------------------------------------------------------------------------------------ 15858( 3) - 24-Sep-2019 13:48:15 - [ 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 M101-DW21 ACS/WFC ACCUM WFC1 F606W 1 650 S PATTERN 1 1-2; PAR 2 see below WITH 1 (1200 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFC3/UVI ACCUM UVIS1 F606W 1 200 S S see below (1270 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 M101-DW21 ACS/WFC ACCUM WFC1 F814W 1 450 S PATTERN 1 3-4; PAR 4 see below WITH 3 (1050 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFC3/UVI ACCUM UVIS1 F814W FLASH=3.0 1 200 S S see below (1112 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 | ------------------------------------------------------------------------------------------------------------------------------------ M101-DW21 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 300.0 S M101-DW21 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 900.0 S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 1 none none none 1 360.0 S S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 2 none none none 1 910.0 S S M101-DW21 3 ACS/WFC ACCUM WFC1 F814W 1 none none none 1 700.0 S M101-DW21 3 ACS/WFC ACCUM WFC1 F814W 2 none none none 1 350.0 S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 1 none none none 1 752.0 S S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 2 none none none 1 360.0 S S 15858( 3) - 24-Sep-2019 13:48:15 - [ 6] Visit: 02 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 M101-DW22 ACS/WFC ACCUM WFC1 F606W 1 650 S PATTERN 1 1-2; PAR 2 see below WITH 1 (1200 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFC3/UVI ACCUM UVIS1 F606W 1 200 S S see below (1270 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 M101-DW22 ACS/WFC ACCUM WFC1 F814W 1 450 S PATTERN 1 3-4; PAR 4 see below WITH 3 (1050 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFC3/UVI ACCUM UVIS1 F814W FLASH=3.0 1 200 S S see below (1112 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 | ------------------------------------------------------------------------------------------------------------------------------------ M101-DW22 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 300.0 S M101-DW22 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 900.0 S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 1 none none none 1 360.0 S S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 2 none none none 1 910.0 S S M101-DW22 3 ACS/WFC ACCUM WFC1 F814W 1 none none none 1 700.0 S M101-DW22 3 ACS/WFC ACCUM WFC1 F814W 2 none none none 1 350.0 S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 1 none none none 1 752.0 S S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 2 none none none 1 360.0 S S 15858( 3) - 24-Sep-2019 13:48:15 - [ 7] Visit: 03 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 M101-DW23 ACS/WFC ACCUM WFC1 F606W 1 650 S PATTERN 1 1-2; PAR 2 see below WITH 1 (1200 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFC3/UVI ACCUM UVIS1 F606W 1 200 S S see below (1270 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 M101-DW23 ACS/WFC ACCUM WFC1 F814W 1 450 S PATTERN 1 3-4; PAR 4 see below WITH 3 (1050 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFC3/UVI ACCUM UVIS1 F814W FLASH=3.0 1 200 S S see below (1112 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 | ------------------------------------------------------------------------------------------------------------------------------------ M101-DW23 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 300.0 S M101-DW23 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 900.0 S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 1 none none none 1 360.0 S S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 2 none none none 1 910.0 S S M101-DW23 3 ACS/WFC ACCUM WFC1 F814W 1 none none none 1 700.0 S M101-DW23 3 ACS/WFC ACCUM WFC1 F814W 2 none none none 1 350.0 S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 1 none none none 1 752.0 S S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 2 none none none 1 360.0 S S 15858( 3) - 24-Sep-2019 13:48:15 - [ 8] Visit: 04 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 M101-DW35 ACS/WFC ACCUM WFC1 F606W 1 650 S PATTERN 1 1-2; PAR 2 see below WITH 1 (1200 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFC3/UVI ACCUM UVIS1 F606W 1 200 S S see below (1270 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 M101-DW35 ACS/WFC ACCUM WFC1 F814W 1 450 S PATTERN 1 3-4; PAR 4 see below WITH 3 (1050 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFC3/UVI ACCUM UVIS1 F814W FLASH=3.0 1 200 S S see below (1112 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 | ------------------------------------------------------------------------------------------------------------------------------------ M101-DW35 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 300.0 S M101-DW35 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 900.0 S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 1 none none none 1 360.0 S S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 2 none none none 1 910.0 S S M101-DW35 3 ACS/WFC ACCUM WFC1 F814W 1 none none none 1 700.0 S M101-DW35 3 ACS/WFC ACCUM WFC1 F814W 2 none none none 1 350.0 S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 1 none none none 1 752.0 S S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 2 none none none 1 360.0 S S 15858( 3) - 24-Sep-2019 13:48:15 - [ 9] Summary Form for Proposal 15858 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS1, WFC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=3.0 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PAR 2 WITH 1, PAR 4 WITH 3, PATTERN 1 1-2, PATTERN 1 3-4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names ANY, M101-DW21, M101-DW22, M101-DW23, M101-DW35 ------------------------------------------------------------------------------------------------------------------------------------