14748( 2) - 01-Aug-2016 14:40:57 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14748 Version: 2 Check-in Time: 01-Aug-2016 14:40:57 STScI Edit Number: 0 Title A close-up view of the star formation history of a young ultracompact dwarf ------------------------------------------------------------------------------------ Type Cycle GO 24 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Aaron Romanowsky San Jose State University Y CoI: Dr. Soeren S. Larsen Radboud Universiteit Nijmegen Y CoI: Prof. Jean P. Brodie University of California - Santa Cruz N CoI: Dr. Jeffrey L Carlin Rensselaer Polytechnic Institute N CoI: Prof. David J. Sand Texas Tech University N CoI: Dr. Duncan A. Forbes Swinburne University of Technology N CoI: Dr. Knut Anders Grova Olsen National Optical Astronomy Observatory, N AURA CoI: Dr. Beth Willman Haverford College N CoI: Prof. Jay Strader Michigan State University N CoI: Dr. Joachim Janz Swinburne University of Technology N CoI: Dr. Ignacio Martin-Navarro University of California - Santa Cruz N CoI: Ms. Vakini Santhanakrishnan San Jose State University N CoI: Dr. Kristine Spekkens Royal Military College of Canada N CoI: Prof. Sukanya Chakrabarti Rochester Institute of Technology N CoI: Dr. Denija Crnojevic Texas Tech University N ------------------------------------------------------------------------------------ Abstract We have recently discovered a young ultracompact dwarf (UCD) in the dwarf spiral galaxy NGC 247. This is by far the nearest known UCD (3.6 Mpc), providing a unique opportunity to study the stellar populations of a UCD in detail. There are indications that this object originated as the nucleus of a smaller dwarf, stripped in a recent merger, and that it harbors multiple stellar populations. We propose to use WFC3-UVIS imaging to map out the internal color gradient of the UCD and to construct a color-magnitude diagram of its stars. We will be able to detect age spreads down to 100 Myr, which would provide an important point of reference for the mystery of multiple stellar populations in star clusters. ------------------------------------------------------------------------------------ Observations Description ------------------------ The technical goals of the observations are: (1) to obtain high spatial resolution imaging of the UCD integrated light, to measure a radial color profile on scales of ~0.05-0.4 arcsec; (2) to construct a color-magnitude diagram (CMD) of individual stars (magnitude range ~24.5-28.5) at the periphery of the UCD, at radii of ~0.4-3.5 arcsec (trying in particular to measure magnitude spreads of post-main-sequence blue loop stars); (3) to construct a CMD of surrounding stream stars, out to radii of ~20 arcsec. We will observe the UCD with three orbits for each of two filters (WFC3/UVIS 14748( 2) - 01-Aug-2016 14:40:57 - [ 2] F475W and F606W, similar to g and V). The same orientation is used for both filters. We will use a three-point subpixel dither pattern (one point per orbit) with a two-point line sub-pattern (each orbit split into two exposures), equivalent to the pattern WFC3-UVIS-MOS-DITH-LINE. We will place the target close to a read-out amplifier (~30 arcsec) in order to reduce CTE loss, using the UVIS2-C1K1C-CTE aperture. Our total exposure times per filter are 2 hours, split into 6 exposures each. The CMD photometry will be done on individual rather than combined frames. Additional short exposures (1-5 min) are obtained in 6 filters (F225W, F275W, F390W, F475W, F606W, F814W) for increased wavelength coverage on the UCD imaging. ------------------------------------------------------------------------------------ 14748( 2) - 01-Aug-2016 14:40:57 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC-247-UCD1 STELLAR CLUSTER, RA=00H46M50.7198S +/- 0.29", J2000 Z = V = 18.5 +/- 0.1 GLOBULAR CLUSTER DEC=-20D39'4.97" +/- 0.28" 0.0005 Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 14748( 2) - 01-Aug-2016 14:40:57 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-MOS-DITH-LINE WFC3-UVIS-MOS-DITH-LINE Pattern_Purpose MOSAIC DITHER Number_Of_Points 3 2 Point_Spacing 2.4 0.119 Line_Spacing Coordinate_Frame POS-TARG POS-TARG Pattern_Orient 85.754 33.606 Angle_Between_Sides Center_Pattern YES NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.145 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 14748( 2) - 01-Aug-2016 14:40:57 - [ 5] Visit: 01 (F475W visit) Visit Requirements: On Hold Comments: Additional Comments: Long exposures in F475W + short exposures in F475W, F225W, F275W. 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 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F475W FLASH=12 1 30 S (30 POS TARG -0.178, -2.393 1 S 1C-CTE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F475W 1 1208 S POS TARG -0.178, -2.393 1 S 1C-CTE (1208 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F475W FLASH=12 1 30 S (30 POS TARG -0.079, -2.328 1 S 1C-CTE S) ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F475W 1 1208 S POS TARG -0.079, -2.328 1 S 1C-CTE (1208 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F225W FLASH=12 1 147 S (147 POS TARG 0.000, 0.000 1 S 1C-CTE S) ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F475W 1 1111 S POS TARG 0.000, 0.000 1 S 1C-CTE (1111 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F225W FLASH=12 1 147 S (147 POS TARG 0.099, 0.066 1 S 1C-CTE S) ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F475W 1 1111 S POS TARG 0.099, 0.066 1 S 1C-CTE (1111 S) ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F275W FLASH=12 1 130 S (130 POS TARG 0.178, 2.393 1 S 1C-CTE S) ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F475W 1 1129 S POS TARG 0.178, 2.393 1 S 1C-CTE (1129 S) ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F275W FLASH=12 1 130 S (130 POS TARG 0.277, 2.459 1 S 1C-CTE S) ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F475W 1 1129 S POS TARG 0.277, 2.459 1 S 1C-CTE (1129 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 | ------------------------------------------------------------------------------------------------------------------------------------ 14748( 2) - 01-Aug-2016 14:40:57 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-247-UCD1 1 WFC3/UVI ACCUM UVIS2-C1 F475W none none none none 1 N/A S K1C-CTE NGC-247-UCD1 2 WFC3/UVI ACCUM UVIS2-C1 F475W none none none none 1 N/A S K1C-CTE NGC-247-UCD1 3 WFC3/UVI ACCUM UVIS2-C1 F475W none none none none 1 N/A S K1C-CTE NGC-247-UCD1 4 WFC3/UVI ACCUM UVIS2-C1 F475W none none none none 1 N/A S K1C-CTE NGC-247-UCD1 5 WFC3/UVI ACCUM UVIS2-C1 F225W none none none none 2 N/A S K1C-CTE NGC-247-UCD1 6 WFC3/UVI ACCUM UVIS2-C1 F475W none none none none 2 N/A S K1C-CTE NGC-247-UCD1 7 WFC3/UVI ACCUM UVIS2-C1 F225W none none none none 2 N/A S K1C-CTE NGC-247-UCD1 8 WFC3/UVI ACCUM UVIS2-C1 F475W none none none none 2 N/A S K1C-CTE NGC-247-UCD1 9 WFC3/UVI ACCUM UVIS2-C1 F275W none none none none 3 N/A S K1C-CTE NGC-247-UCD1 10 WFC3/UVI ACCUM UVIS2-C1 F475W none none none none 3 N/A S K1C-CTE NGC-247-UCD1 11 WFC3/UVI ACCUM UVIS2-C1 F275W none none none none 3 N/A S K1C-CTE NGC-247-UCD1 12 WFC3/UVI ACCUM UVIS2-C1 F475W none none none none 3 N/A S K1C-CTE 14748( 2) - 01-Aug-2016 14:40:57 - [ 7] Visit: 02 (F606W visit) Visit Requirements: SAME ORIENT AS 01 On Hold Comments: Additional Comments: Long exposures in F606W + short exposures in F606W, F390W, F814W, using the same Orient as the F475W visit. 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 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F606W FLASH=12 1 30 S (30 POS TARG -0.178, -2.393 1 S 1C-CTE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F606W 1 1208 S POS TARG -0.178, -2.393 1 S 1C-CTE (1208 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F606W FLASH=12 1 30 S (30 POS TARG -0.079, -2.328 1 S 1C-CTE S) ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F606W 1 1208 S POS TARG -0.079, -2.328 1 S 1C-CTE (1208 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F390W FLASH=12 1 41 S (41 POS TARG 0.000, 0.000 1 S 1C-CTE S) ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F606W 1 1220 S POS TARG 0.000, 0.000 1 S 1C-CTE (1220 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F390W FLASH=12 1 41 S (41 POS TARG 0.099, 0.066 1 S 1C-CTE S) ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F606W 1 1220 S POS TARG 0.099, 0.066 1 S 1C-CTE (1220 S) ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F814W FLASH=12 1 80 S (80 POS TARG 0.178, 2.393 1 S 1C-CTE S) ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F606W 1 1179 S POS TARG 0.178, 2.393 1 S 1C-CTE (1179 S) ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F814W FLASH=12 1 80 S (80 POS TARG 0.277, 2.459 1 S 1C-CTE S) ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC-247-UCD WFC3/UVI ACCUM UVIS2-C1K F606W 1 1179 S POS TARG 0.277, 2.459 1 S 1C-CTE (1179 S) ------------------------------------------------------------------------------------------------------------------------------------ 14748( 2) - 01-Aug-2016 14:40:57 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-247-UCD1 1 WFC3/UVI ACCUM UVIS2-C1 F606W none none none none 1 N/A S K1C-CTE NGC-247-UCD1 2 WFC3/UVI ACCUM UVIS2-C1 F606W none none none none 1 N/A S K1C-CTE NGC-247-UCD1 3 WFC3/UVI ACCUM UVIS2-C1 F606W none none none none 1 N/A S K1C-CTE NGC-247-UCD1 4 WFC3/UVI ACCUM UVIS2-C1 F606W none none none none 1 N/A S K1C-CTE NGC-247-UCD1 5 WFC3/UVI ACCUM UVIS2-C1 F390W none none none none 2 N/A S K1C-CTE NGC-247-UCD1 6 WFC3/UVI ACCUM UVIS2-C1 F606W none none none none 2 N/A S K1C-CTE NGC-247-UCD1 7 WFC3/UVI ACCUM UVIS2-C1 F390W none none none none 2 N/A S K1C-CTE NGC-247-UCD1 8 WFC3/UVI ACCUM UVIS2-C1 F606W none none none none 2 N/A S K1C-CTE NGC-247-UCD1 9 WFC3/UVI ACCUM UVIS2-C1 F814W none none none none 3 N/A S K1C-CTE NGC-247-UCD1 10 WFC3/UVI ACCUM UVIS2-C1 F606W none none none none 3 N/A S K1C-CTE NGC-247-UCD1 11 WFC3/UVI ACCUM UVIS2-C1 F814W none none none none 3 N/A S K1C-CTE NGC-247-UCD1 12 WFC3/UVI ACCUM UVIS2-C1 F606W none none none none 3 N/A S K1C-CTE 14748( 2) - 01-Aug-2016 14:40:57 - [ 9] Summary Form for Proposal 14748 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2-C1K1C-CTE ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=12 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements POS TARG -0.079, -2.328, POS TARG -0.178, -2.393, POS TARG 0.000, 0.000, POS TARG 0.099, 0.066, POS TARG 0.178, 2.393, POS TARG 0.277, 2.459, SAME ORIENT AS 01 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F225W, F275W, F390W, F475W, F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC-247-UCD1 ------------------------------------------------------------------------------------------------------------------------------------