13696( 2) - 24-Jul-2014 14:17:00 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 13696 Version: 2 Check-in Time: 24-Jul-2014 14:17:00 STScI Edit Number: 0 Title The Anemic Stellar Halo of M101 ------------------------------------------------------------------------------------ Type Cycle GO 22 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Benne W. Holwerda Sterrewacht Leiden Y CoI: Dr. Eric F. Bell University of Michigan N CoI: Dr. Antonela Monachesi University of Michigan N CoI: Dr. David J. Radburn-Smith University of Washington N CoI: Dr. Jeremy Bailin University of Alabama N CoI: Dr. Roelof S. de Jong Leibniz-Institut fur Astrophysik Potsdam N CoI: Mr. David Streich Leibniz-Institut fur Astrophysik Potsdam N ------------------------------------------------------------------------------------ Abstract Models of galaxy formation in a cosmological context predict that massive disk galaxies should have richly-structured extended stellar halos, containing ~10% of a galaxy's stars, originating in large part from the tidal disruption of dwarf galaxies. Observations of a number of nearby disk galaxies have generally agreed with these expectations. Recent new observations in integrated light with a novel array of low scattered-light telephoto lenses have failed to convincingly detect a stellar halo in the nearby massive face-on disk galaxy M101 (van Dokkum et al. 2014). They argue that any halo has to have <0.3% of the mass of the galaxy. This halo would be the least massive of any massive disk galaxy in the local Universe (by factors of several) -- such a halo is not predicted or naturally interpreted by the models, and would present a critical challenge to the picture of ubiquitous stellar halos formed from the debris of disrupting dwarf galaxies. We propose to resolve the stellar populations of this uniquely anemic stellar halo for 6 orbits with HST (ACS and WFC3), allowing us to reach surface brightness limits sufficient to clearly detect and characterize M101's stellar halo if it carries more than 0.1% of M101's mass. With resolved stellar populations, we can use the gradient of stellar populations as a function of radius to separate stellar halo from disk, which is impossible using integrated light observations. The resolved stellar populations will reveal the halo mass to much greater accuracy, measure the halo radial profile, constrain any halo lopsidedness, estimate the halo's stellar metallicity, and permit an analysis of outer disk stellar populations. ------------------------------------------------------------------------------------ Observations Description ------------------------ The observations are designed to probe the anemic halo of M101. We have placed three pointings at 40, 55 and 75 kpc away from the center with ACS parallel observations aligned with the major axis of M101. We alternate between East-West along this axis. 13696( 2) - 24-Jul-2014 14:17:00 - [ 2] We have checked to the best of our abilities against accidental overlaps with the other Cycle 22 M101 programs: 13682, 13701 and 13691 Orientation is chosen such that the ACS field is away from M101. However, the reciprocal angle would be acceptable (ACS field on the inside) if it aids with scheduling. ------------------------------------------------------------------------------------ 13696( 2) - 24-Jul-2014 14:17:00 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 M101-40KPC GALAXY, DISK, HALO, RA=14H05M30.6800S, J2000 V = 7.86 SPIRAL DEC=+54D20'57.40" Reference Frame: Other: SIMBAD Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 2 M101-55KPC GALAXY, DISK, HALO, RA=14H00M23.1211S, J2000 V = 7.86 SPIRAL DEC=+54D20'29.70" Reference Frame: Other: SIMBAD ------------------------------------------------------------------------------------------------------------------------------------ 3 M101-75KPC GALAXY, DISK, HALO, RA=14H07M4.8683S, J2000 V = 7.86 SPIRAL DEC=+54D20'26.22" Reference Frame: Other: SIMBAD ------------------------------------------------------------------------------------------------------------------------------------ 13696( 2) - 24-Jul-2014 14:17:00 - [ 4] Visit: 01 Visit Requirements: ORIENT 210D TO 240 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 M101-40KPC ACS/WFC ACCUM WFCENTER F606W CR-SPLIT=NO 1 848 S (848 POS TARG -149.2263, S) 124.8626; PAR 2 WITH 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 M101-40KPC WFC3/UVI ACCUM UVIS-CENT F606W CR-SPLIT=NO 1 928 S S ER see below (928 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 M101-40KPC ACS/WFC ACCUM WFCENTER F606W CR-SPLIT=NO 1 846 S (846 POS TARG -149.0120, S) 124.9873; PAR 4 WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 M101-40KPC WFC3/UVI ACCUM UVIS-CENT F606W CR-SPLIT=NO 1 876 S S ER see below (876 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 M101-40KPC ACS/WFC ACCUM WFCENTER F606W CR-SPLIT=NO 1 846 S (846 POS TARG -148.7977, S) 125.1120; PAR 6 WITH 5 ------------------------------------------------------------------------------------------------------------------------------------ 6 M101-40KPC WFC3/UVI ACCUM UVIS-CENT F606W CR-SPLIT=NO 1 972 S (972 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 7 M101-40KPC ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO 1 894 S (894 SAME POS AS 1; PAR 8 S) WITH 7 ------------------------------------------------------------------------------------------------------------------------------------ 8 M101-40KPC WFC3/UVI ACCUM UVIS-CENT F814W CR-SPLIT=NO 1 956 S S ER see below (956 S) ------------------------------------------------------------------------------------------------------------------------------------ 9 M101-40KPC ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO 1 892 S (892 SAME POS AS 3; PAR 10 S) WITH 9 ------------------------------------------------------------------------------------------------------------------------------------ 10 M101-40KPC WFC3/UVI ACCUM UVIS-CENT F814W CR-SPLIT=NO 1 922 S S ER see below (922 S) ------------------------------------------------------------------------------------------------------------------------------------ 11 M101-40KPC ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO 1 892 S (892 SAME POS AS 5; PAR 12 S) WITH 11 ------------------------------------------------------------------------------------------------------------------------------------ 12 M101-40KPC WFC3/UVI ACCUM UVIS-CENT F814W CR-SPLIT=NO 1 1018 S S ER (1018 S) ------------------------------------------------------------------------------------------------------------------------------------ 13696( 2) - 24-Jul-2014 14:17:00 - [ 5] 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 | ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ M101-40KPC 1 ACS/WFC ACCUM WFCENTER F606W none none none none 1 N/A M101-40KPC 2 WFC3/UVI ACCUM UVIS-CEN F606W none none none none 1 928.0 S S TER M101-40KPC 3 ACS/WFC ACCUM WFCENTER F606W none none none none 1 N/A M101-40KPC 4 WFC3/UVI ACCUM UVIS-CEN F606W none none none none 1 876.0 S S TER M101-40KPC 5 ACS/WFC ACCUM WFCENTER F606W none none none none 1 N/A M101-40KPC 6 WFC3/UVI ACCUM UVIS-CEN F606W none none none none 1 N/A S TER M101-40KPC 7 ACS/WFC ACCUM WFCENTER F814W none none none none 2 N/A M101-40KPC 8 WFC3/UVI ACCUM UVIS-CEN F814W none none none none 2 956.0 S S TER M101-40KPC 9 ACS/WFC ACCUM WFCENTER F814W none none none none 2 N/A M101-40KPC 10 WFC3/UVI ACCUM UVIS-CEN F814W none none none none 2 922.0 S S TER M101-40KPC 11 ACS/WFC ACCUM WFCENTER F814W none none none none 2 N/A M101-40KPC 12 WFC3/UVI ACCUM UVIS-CEN F814W none none none none 2 N/A S TER 13696( 2) - 24-Jul-2014 14:17:00 - [ 6] Visit: 02 Visit Requirements: ORIENT 30D TO 60 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 M101-55KPC ACS/WFC ACCUM WFCENTER F606W CR-SPLIT=NO 1 848 S (848 POS TARG -149.2263, S) 124.8626; PAR 2 WITH 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 M101-55KPC WFC3/UVI ACCUM UVIS-CENT F606W CR-SPLIT=NO 1 928 S (928 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 3 M101-55KPC ACS/WFC ACCUM WFCENTER F606W CR-SPLIT=NO 1 846 S (846 POS TARG -149.0120, S) 124.9873; PAR 4 WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 M101-55KPC WFC3/UVI ACCUM UVIS-CENT F606W CR-SPLIT=NO 1 876 S (876 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 5 M101-55KPC ACS/WFC ACCUM WFCENTER F606W CR-SPLIT=NO 1 846 S (846 POS TARG -148.7977, S) 125.1120; PAR 6 WITH 5 ------------------------------------------------------------------------------------------------------------------------------------ 6 M101-55KPC WFC3/UVI ACCUM UVIS-CENT F606W CR-SPLIT=NO 1 972 S (972 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 7 M101-55KPC ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO 1 894 S (894 SAME POS AS 1; PAR 8 S) WITH 7 ------------------------------------------------------------------------------------------------------------------------------------ 8 M101-55KPC WFC3/UVI ACCUM UVIS-CENT F814W CR-SPLIT=NO 1 956 S (956 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 9 M101-55KPC ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO 1 892 S (892 SAME POS AS 3; PAR 10 S) WITH 9 ------------------------------------------------------------------------------------------------------------------------------------ 10 M101-55KPC WFC3/UVI ACCUM UVIS-CENT F814W CR-SPLIT=NO 1 922 S (922 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 11 M101-55KPC ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO 1 892 S (892 SAME POS AS 5; PAR 12 S) WITH 11 ------------------------------------------------------------------------------------------------------------------------------------ 12 M101-55KPC WFC3/UVI ACCUM UVIS-CENT F814W CR-SPLIT=NO 1 1018 S S ER (1018 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 | ------------------------------------------------------------------------------------------------------------------------------------ 13696( 2) - 24-Jul-2014 14:17:00 - [ 7] 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 | ------------------------------------------------------------------------------------------------------------------------------------ M101-55KPC 1 ACS/WFC ACCUM WFCENTER F606W none none none none 1 N/A M101-55KPC 2 WFC3/UVI ACCUM UVIS-CEN F606W none none none none 1 N/A S TER M101-55KPC 3 ACS/WFC ACCUM WFCENTER F606W none none none none 1 N/A M101-55KPC 4 WFC3/UVI ACCUM UVIS-CEN F606W none none none none 1 N/A S TER M101-55KPC 5 ACS/WFC ACCUM WFCENTER F606W none none none none 1 N/A M101-55KPC 6 WFC3/UVI ACCUM UVIS-CEN F606W none none none none 1 N/A S TER M101-55KPC 7 ACS/WFC ACCUM WFCENTER F814W none none none none 2 N/A M101-55KPC 8 WFC3/UVI ACCUM UVIS-CEN F814W none none none none 2 N/A S TER M101-55KPC 9 ACS/WFC ACCUM WFCENTER F814W none none none none 2 N/A M101-55KPC 10 WFC3/UVI ACCUM UVIS-CEN F814W none none none none 2 N/A S TER M101-55KPC 11 ACS/WFC ACCUM WFCENTER F814W none none none none 2 N/A M101-55KPC 12 WFC3/UVI ACCUM UVIS-CEN F814W none none none none 2 N/A S TER 13696( 2) - 24-Jul-2014 14:17:00 - [ 8] Visit: 03 Visit Requirements: ORIENT 210D TO 240 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 M101-75KPC ACS/WFC ACCUM WFCENTER F606W CR-SPLIT=NO 1 848 S (848 POS TARG -149.2263, S) 124.8626; PAR 2 WITH 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 M101-75KPC WFC3/UVI ACCUM UVIS-CENT F606W CR-SPLIT=NO 1 928 S (928 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 3 M101-75KPC ACS/WFC ACCUM WFCENTER F606W CR-SPLIT=NO 1 846 S (846 POS TARG -149.0120, S) 124.9873; PAR 4 WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 M101-75KPC WFC3/UVI ACCUM UVIS-CENT F606W CR-SPLIT=NO 1 876 S (876 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 5 M101-75KPC ACS/WFC ACCUM WFCENTER F606W CR-SPLIT=NO 1 846 S (846 POS TARG -148.7977, S) 125.1120; PAR 6 WITH 5 ------------------------------------------------------------------------------------------------------------------------------------ 6 M101-75KPC WFC3/UVI ACCUM UVIS-CENT F606W CR-SPLIT=NO 1 972 S (972 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 7 M101-75KPC ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO 1 894 S (894 SAME POS AS 1; PAR 8 S) WITH 7 ------------------------------------------------------------------------------------------------------------------------------------ 8 M101-75KPC WFC3/UVI ACCUM UVIS-CENT F814W CR-SPLIT=NO 1 956 S (956 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 9 M101-75KPC ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO 1 892 S (892 SAME POS AS 3; PAR 10 S) WITH 9 ------------------------------------------------------------------------------------------------------------------------------------ 10 M101-75KPC WFC3/UVI ACCUM UVIS-CENT F814W CR-SPLIT=NO 1 922 S (922 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 11 M101-75KPC ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO 1 892 S (892 SAME POS AS 5; PAR 12 S) WITH 11 ------------------------------------------------------------------------------------------------------------------------------------ 12 M101-75KPC WFC3/UVI ACCUM UVIS-CENT F814W CR-SPLIT=NO 1 1018 S S ER (1018 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 | ------------------------------------------------------------------------------------------------------------------------------------ 13696( 2) - 24-Jul-2014 14:17:00 - [ 9] 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 | ------------------------------------------------------------------------------------------------------------------------------------ M101-75KPC 1 ACS/WFC ACCUM WFCENTER F606W none none none none 1 N/A M101-75KPC 2 WFC3/UVI ACCUM UVIS-CEN F606W none none none none 1 N/A S TER M101-75KPC 3 ACS/WFC ACCUM WFCENTER F606W none none none none 1 N/A M101-75KPC 4 WFC3/UVI ACCUM UVIS-CEN F606W none none none none 1 N/A S TER M101-75KPC 5 ACS/WFC ACCUM WFCENTER F606W none none none none 1 N/A M101-75KPC 6 WFC3/UVI ACCUM UVIS-CEN F606W none none none none 1 N/A S TER M101-75KPC 7 ACS/WFC ACCUM WFCENTER F814W none none none none 2 N/A M101-75KPC 8 WFC3/UVI ACCUM UVIS-CEN F814W none none none none 2 N/A S TER M101-75KPC 9 ACS/WFC ACCUM WFCENTER F814W none none none none 2 N/A M101-75KPC 10 WFC3/UVI ACCUM UVIS-CEN F814W none none none none 2 N/A S TER M101-75KPC 11 ACS/WFC ACCUM WFCENTER F814W none none none none 2 N/A M101-75KPC 12 WFC3/UVI ACCUM UVIS-CEN F814W none none none none 2 N/A S TER 13696( 2) - 24-Jul-2014 14:17:00 - [ 10] Summary Form for Proposal 13696 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS-CENTER, WFCENTER ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 210D TO 240 D, ORIENT 30D TO 60 D, PAR 10 WITH 9, PAR 12 WITH 11, PAR 2 WITH 1, PAR 4 WITH 3, PAR 6 WITH 5, PAR 8 WITH 7, POS TARG -148.7977, 125.1120, POS TARG -149.0120, 124.9873, POS TARG -149.2263, 124.8626, SAME POS AS 1, SAME POS AS 3, SAME POS AS 5 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names M101-40KPC, M101-55KPC, M101-75KPC ------------------------------------------------------------------------------------------------------------------------------------