14147( 2) - 20-Jul-2015 14:48:19 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14147 Version: 2 Check-in Time: 20-Jul-2015 14:48:19 STScI Edit Number: 0 Title Opening a New Window towards the Nuclear Star Cluster in the Milky Way ------------------------------------------------------------------------------------ Type Cycle GO 23 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Hui Dong Instituto de Astrofisica de Andalucia Y (IAA) CoI: Dr. Rainer Schodel Instituto de Astrofisica de Andalucia N (IAA) CoI: Prof. Q. Daniel Wang University of Massachusetts - Amherst N ------------------------------------------------------------------------------------ Abstract The nuclear star cluster in the Galactic Centre is the only place where we can study star formation near a massive black hole in great detail. However, due to the strong foreground extinction, previous studies have been limited to the J-band and longer wavelengths. The short wavelength coverage, from J to K, hampers attempts to accurately determine the extinction curve, to map the extinction distribution, to distinguish between massive and low-mass stars and finally, to disentangle different stellar populations through the colour magnitude diagram. Deep F105W observations with HST WFC3/IR would result in great progress toward overcoming these problems. This program can help us to make significant progress in addressing the following important astrophysics questions: 1) what are the properties of the extinction law toward the Galactic Centre environment? 2) what was the assembly history of the nuclear star cluster in the Galactic Centre? ------------------------------------------------------------------------------------ Observations Description ------------------------ We use five HST orbits to observe the nuclear star cluster in the Milky Way at F105W band with one WFC3/IR pointing. In order to achieve our scientific goals, i.e. extinction law, extinction map and disentangling different stellar populations from the color-magnitude diagram, we need high photometry precision, especially in this extreme crowding region. We fine-tune the dithering pattern to overcome the undersample problem of the WFC3/IR detector, the main obstacle affecting the photometry accuracy. We use sub-pixel offset among dithering exposures to better sample the point spread function. Meanwhile, we also employ integer-pixel diterhng exposures to recover the information lost due to the bad pixels. Due to the huge number of visits with non-stop 5 orbits, as suggested by the Contact Scientist, we divide our 5 orbits into two visits, one with two orbits and the other one with three orbits. In these two visits, we choose 1/3 and 1/4 pixel sub-pixel offset, respectively. Meanwhile, four and three dithering exposures with integer-pixel offset are used too. In order to use each orbit efficiently, we slightly change the parameters of 14147( 2) - 20-Jul-2015 14:48:19 - [ 2] MULTIACCUM for different dithering exposures. As a result, we have only ~10 second left in each orbit, although the exposure time among different exposures change from 350 to 450 seconds. The total effective exposure time of the five orbits is 12.6 ks. For each dithering exposure, we employ the STEP sequence, instead of the SPARS sequence, considering the wide range of stellar magnitudes of stars in the Galactic Center. In order to compare with previous WFC3/IR observations in the F127M, F139M, F153M, we use the same coordinate and rotation angale as those used in Program 11671. ------------------------------------------------------------------------------------ 14147( 2) - 20-Jul-2015 14:48:19 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SGRA-NC STELLAR CLUSTER, DUST RA=17H45M40.0400S +/- 0.1", J2000 V = 14 +/- 0.1 J-12.2, H=9.26, K=6.5 LANE, NUCLEUS, OPEN DEC=-29D00'28.10" +/- 0.1" CLUSTER, STAR FORMING REGION Reference Frame: ICRS Comments: The magnitude are for the brightese star in the field-of-view. ------------------------------------------------------------------------------------------------------------------------------------ 14147( 2) - 20-Jul-2015 14:48:19 - [ 4] Visit: 01 Visit Requirements: ORIENT 90D TO 100 D; ORIENT 270D TO 280 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 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=12, SAMP-SEQ=STEP50 1 DEF CUM (349.233 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=12, SAMP-SEQ=STEP50 1 DEF POS TARG 0, 0.39357500 CUM (349.233 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=12, SAMP-SEQ=STEP50 1 DEF POS TARG 0.47425000, 0 CUM (349.233 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=12, SAMP-SEQ=STEP50 1 DEF POS TARG 0.47425000 , CUM (349.233 0.45412500 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=12, SAMP-SEQ=STEP50 1 DEF POS TARG 0, 3.4513500 CUM (349.233 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=12, SAMP-SEQ=STEP50 1 DEF POS TARG 0, 3.8449250 CUM (349.233 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=12, SAMP-SEQ=STEP50 1 DEF POS TARG 0.47425000 , CUM (349.233 3.4513500 S) ------------------------------------------------------------------------------------------------------------------------------------ 8 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=14, SAMP-SEQ=STEP50 1 DEF POS TARG 0.47425000, CUM (449.234 3.7843750 S) ------------------------------------------------------------------------------------------------------------------------------------ 9 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=14, SAMP-SEQ=STEP50 1 DEF POS TARG 3.8278750, CUM (449.234 0.0000000 S) ------------------------------------------------------------------------------------------------------------------------------------ 10 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=14, SAMP-SEQ=STEP50 1 DEF POS TARG 3.8278750, CUM (449.234 0.39357500 S) ------------------------------------------------------------------------------------------------------------------------------------ 14147( 2) - 20-Jul-2015 14:48:19 - [ 5] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 11 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=14, SAMP-SEQ=STEP50 1 DEF POS TARG 4.3021250, 0 CUM (449.234 S) ------------------------------------------------------------------------------------------------------------------------------------ 12 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=14, SAMP-SEQ=STEP50 1 DEF POS TARG 4.3021250, CUM (449.234 0.42385000 S) ------------------------------------------------------------------------------------------------------------------------------------ 13 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=13, SAMP-SEQ=STEP50 1 DEF POS TARG 3.8278750, CUM (399.233 3.4513500 S) ------------------------------------------------------------------------------------------------------------------------------------ 14 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=14, SAMP-SEQ=STEP50 1 DEF POS TARG 3.8278750 , CUM (449.234 3.8449250 S) ------------------------------------------------------------------------------------------------------------------------------------ 15 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=14, SAMP-SEQ=STEP50 1 DEF POS TARG 4.3021250 , CUM (449.234 3.4210750 S) ------------------------------------------------------------------------------------------------------------------------------------ 16 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=14, SAMP-SEQ=STEP50 1 DEF POS TARG 4.3021250, CUM (449.234 3.8449250 S) ------------------------------------------------------------------------------------------------------------------------------------ 17 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=14, SAMP-SEQ=STEP50 1 DEF POS TARG 1.3550000 , CUM (449.234 2.4220000 S) ------------------------------------------------------------------------------------------------------------------------------------ 18 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=14, SAMP-SEQ=STEP50 1 DEF POS TARG 2.7100000 , CUM (449.234 1.2110000 S) ------------------------------------------------------------------------------------------------------------------------------------ 19 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=13, SAMP-SEQ=STEP50 1 DEF POS TARG 2.7100000, CUM (399.233 2.4220000 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 | ------------------------------------------------------------------------------------------------------------------------------------ SGRA-NC 1 WFC3/IR MULTIAC IR-FIX F105W none none none none 1 N/A CUM SGRA-NC 2 WFC3/IR MULTIAC IR-FIX F105W none none none none 1 N/A CUM 14147( 2) - 20-Jul-2015 14:48:19 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ SGRA-NC 3 WFC3/IR MULTIAC IR-FIX F105W none none none none 1 N/A CUM SGRA-NC 4 WFC3/IR MULTIAC IR-FIX F105W none none none none 1 N/A CUM SGRA-NC 5 WFC3/IR MULTIAC IR-FIX F105W none none none none 1 N/A CUM SGRA-NC 6 WFC3/IR MULTIAC IR-FIX F105W none none none none 1 N/A CUM SGRA-NC 7 WFC3/IR MULTIAC IR-FIX F105W none none none none 1 N/A CUM SGRA-NC 8 WFC3/IR MULTIAC IR-FIX F105W none none none none 2 N/A CUM SGRA-NC 9 WFC3/IR MULTIAC IR-FIX F105W none none none none 2 N/A CUM SGRA-NC 10 WFC3/IR MULTIAC IR-FIX F105W none none none none 2 N/A CUM SGRA-NC 11 WFC3/IR MULTIAC IR-FIX F105W none none none none 2 N/A CUM SGRA-NC 12 WFC3/IR MULTIAC IR-FIX F105W none none none none 2 N/A CUM SGRA-NC 13 WFC3/IR MULTIAC IR-FIX F105W none none none none 2 N/A CUM SGRA-NC 14 WFC3/IR MULTIAC IR-FIX F105W none none none none 3 N/A CUM SGRA-NC 15 WFC3/IR MULTIAC IR-FIX F105W none none none none 3 N/A CUM SGRA-NC 16 WFC3/IR MULTIAC IR-FIX F105W none none none none 3 N/A CUM SGRA-NC 17 WFC3/IR MULTIAC IR-FIX F105W none none none none 3 N/A CUM SGRA-NC 18 WFC3/IR MULTIAC IR-FIX F105W none none none none 3 N/A CUM SGRA-NC 19 WFC3/IR MULTIAC IR-FIX F105W none none none none 3 N/A CUM 14147( 2) - 20-Jul-2015 14:48:19 - [ 7] Visit: 02 Visit Requirements: ORIENT 90D TO 100 D; ORIENT 270D TO 280 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 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=12, SAMP-SEQ=STEP50 1 DEF CUM (349.233 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=12, SAMP-SEQ=STEP50 1 DEF POS TARG 0, 0.44443701 CUM (349.233 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=12, SAMP-SEQ=STEP50 1 DEF POS TARG 0.45121499, CUM (349.233 0.0000000 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=12, SAMP-SEQ=STEP50 1 DEF POS TARG 0.0000000 , CUM (349.233 3.4307630 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=12, SAMP-SEQ=STEP50 1 DEF POS TARG 0.45121499 , CUM (349.233 3.4307630 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=12, SAMP-SEQ=STEP50 1 DEF POS TARG 0.45121499, CUM (349.233 3.4719370 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=12, SAMP-SEQ=STEP50 1 DEF POS TARG 3.8847850 , CUM (349.233 3.3908000 S) ------------------------------------------------------------------------------------------------------------------------------------ 8 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=14, SAMP-SEQ=STEP50 1 DEF POS TARG 3.8847850, CUM (449.234 3.4307630 S) ------------------------------------------------------------------------------------------------------------------------------------ 9 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=14, SAMP-SEQ=STEP50 1 DEF POS TARG 3.8847850 , CUM (449.234 3.4719370 S) ------------------------------------------------------------------------------------------------------------------------------------ 10 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=14, SAMP-SEQ=STEP50 1 DEF POS TARG 1.3550000 , CUM (449.234 1.2110000 S) ------------------------------------------------------------------------------------------------------------------------------------ 14147( 2) - 20-Jul-2015 14:48:19 - [ 8] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 11 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=14, SAMP-SEQ=STEP50 1 DEF POS TARG 1.3550000, CUM (449.234 2.4220000 S) ------------------------------------------------------------------------------------------------------------------------------------ 12 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=13, SAMP-SEQ=STEP50 1 DEF POS TARG 2.7100000 , CUM (399.233 1.2110000 S) ------------------------------------------------------------------------------------------------------------------------------------ 13 SGRA-NC WFC3/IR MULTIAC IR-FIX F105W NSAMP=14, SAMP-SEQ=STEP50 1 DEF POS TARG 2.7100000, CUM (449.234 2.4220000 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 | ------------------------------------------------------------------------------------------------------------------------------------ SGRA-NC 1 WFC3/IR MULTIAC IR-FIX F105W none none none none 1 N/A CUM SGRA-NC 2 WFC3/IR MULTIAC IR-FIX F105W none none none none 1 N/A CUM SGRA-NC 3 WFC3/IR MULTIAC IR-FIX F105W none none none none 1 N/A CUM SGRA-NC 4 WFC3/IR MULTIAC IR-FIX F105W none none none none 1 N/A CUM SGRA-NC 5 WFC3/IR MULTIAC IR-FIX F105W none none none none 1 N/A CUM SGRA-NC 6 WFC3/IR MULTIAC IR-FIX F105W none none none none 1 N/A CUM SGRA-NC 7 WFC3/IR MULTIAC IR-FIX F105W none none none none 1 N/A CUM SGRA-NC 8 WFC3/IR MULTIAC IR-FIX F105W none none none none 2 N/A CUM SGRA-NC 9 WFC3/IR MULTIAC IR-FIX F105W none none none none 2 N/A CUM SGRA-NC 10 WFC3/IR MULTIAC IR-FIX F105W none none none none 2 N/A CUM SGRA-NC 11 WFC3/IR MULTIAC IR-FIX F105W none none none none 2 N/A CUM SGRA-NC 12 WFC3/IR MULTIAC IR-FIX F105W none none none none 2 N/A CUM SGRA-NC 13 WFC3/IR MULTIAC IR-FIX F105W none none none none 2 N/A CUM 14147( 2) - 20-Jul-2015 14:48:19 - [ 9] Summary Form for Proposal 14147 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/IR ------------------------------------------------------------------------------------------------------------------------------------ Opmodes MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters NSAMP=12, NSAMP=13, NSAMP=14, SAMP-SEQ=STEP50 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 270D TO 280 D, ORIENT 90D TO 100 D, POS TARG 0, 0.39357500, POS TARG 0, 0.44443701, POS TARG 0, 3.4513500, POS TARG 0, 3.8449250, POS TARG 0.0000000 , 3.4307630, POS TARG 0.45121499 , 3.4307630, POS TARG 0.45121499, 0.0000000, POS TARG 0.45121499, 3.4719370, POS TARG 0.47425000 , 0.45412500, POS TARG 0.47425000 , 3.4513500, POS TARG 0.47425000, 0, POS TARG 0.47425000, 3.7843750, POS TARG 1.3550000 , 1.2110000, POS TARG 1.3550000 , 2.4220000, POS TARG 1.3550000, 2.4220000, POS TARG 2.7100000 , 1.2110000, POS TARG 2.7100000, 2.4220000, POS TARG 3.8278750 , 3.8449250, POS TARG 3.8278750, 0.0000000, POS TARG 3.8278750, 0.39357500, POS TARG 3.8278750, 3.4513500, POS TARG 3.8847850 , 3.3908000, POS TARG 3.8847850 , 3.4719370, POS TARG 3.8847850, 3.4307630, POS TARG 4.3021250 , 3.4210750, POS TARG 4.3021250, 0, POS TARG 4.3021250, 0.42385000, POS TARG 4.3021250, 3.8449250 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F105W ------------------------------------------------------------------------------------------------------------------------------------ Target Names SGRA-NC ------------------------------------------------------------------------------------------------------------------------------------