16990( 2) - 18-Jul-2022 15:00:29 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16990 Version: 2 Check-in Time: 18-Jul-2022 15:00:29 STScI Edit Number: 0 Title Advancing a decades long experiment at the Galactic center ------------------------------------------------------------------------------------ Type Cycle GO 30 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Tuan Do University of California - Los Angeles Y CoI: Dr. Matthew Hosek Jr. University of California - Los Angeles N CoI: Dr. Andrea M. Ghez University of California - Los Angeles N CoI: Dr. Mark R. Morris University of California - Los Angeles N CoI: Dr. Shoko Sakai University of California - Los Angeles N CoI: Dr. Eric E. Becklin University of California - Los Angeles N CoI: Ms. Zhuo Chen University of California - Los Angeles N CoI: Ms. Rebecca Lewis University of California - Los Angeles N CoI: Dr. Abhimat Krishna Gautam University of California - Los Angeles N CoI: Dr. Jessica Ryan Lu University of California - Berkeley N CoI: Dr. Aurelien Hees University of California - Los Angeles N CoI: Dr. Jay Anderson Space Telescope Science Institute N ------------------------------------------------------------------------------------ Abstract Observations of the orbits of stars around the supermassive black hole at the center of our Galaxy have brought us new and exciting insights into the physics and astrophysics of supermassive black holes. These observations have not only provided the best evidence so far for the existence of supermassive black holes, but they have also advanced our understanding of star formation and stellar dynamics in this region. With a time baseline of over 25 years, we can perform ever more powerful experiments, the latest of which are measurements of the effect of General Relativity on the orbit of the star S0-2/S2. As astrometry becomes more precise, the discovery of our Galaxy's dark cusp of compact objects is now within reach. However, there is a fundamental limitation: the stability of the reference frame. We propose to observe the Galactic center with WFC3-IR in the next three cycles, which when combined with Gaia data will create the most accurate reference frame to date. These measurements from 2022-2024 will (1) enable the detection of a dark cusp around the black hole (2) take advantage of the unique overlap in observations between HST, Gaia (ending in 2024), JWST (beginning in 2022), and the ground to cross-calibrate instrumental systematic uncertainties to build on the legacy of astrometry with HST; (3) use HST observations to double our yearly time baseline for monitoring the near-infrared activity of Sgr A* to determine the physical origins of its recent unprecedented increase in activity. ------------------------------------------------------------------------------------ Observations Description ------------------------ This program has two main goals: Measure precise astrometry for a sample of stars in common between HST and Gaia at the Galactic center in order to build a stable reference frame for the measurements of orbits around the supermassive black hole at the Galactic center. The stability of the reference frame is driven by the goal of measuring 16990( 2) - 18-Jul-2022 15:00:29 - [ 2] the precession of the orbit of the star S0-2 from General Relativity and extended mass. As such, this program requires very high astrometric precision and minimal systematic errors. We have designed the Phase II observations to achieve these goals. Monitor the flux variation from the supermassive black hole Sgr A* in the near-infrared. Sgr A* is ideally monitored early and late in the year, when the Galactic center is not visible from the ground, doubling the yearly monitoring baseline. Astrometry and photometry: We request that observations in the F153M filter with a spiral dither pattern to subsample the PSF. We request that observations be made at an ORIENT=270 early in the year (Feb. to May) and ORIENT=90 later in the year (Jul. to Oct.). These two ORIENTS have been used in past astrometry programs at the Galactic center and keeping this orientation will help to minimize the effect of residual optical distortions. Timing constraints: We request 3 orbits be allocated early in the year and 3 later in the year. This in part, comes from the constraints on the ORIENT and also driven scientifically to maximize the baseline during the year that we can use to monitor the behavior of the near-infrared emission from Sgr A*. ------------------------------------------------------------------------------------ 16990( 2) - 18-Jul-2022 15:00:29 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NAME-SGR-A STELLAR CLUSTER, RA=17H45M40.0360S, J2000 V = 14 NUCLEUS DEC=-29D00'28.17" Reference Frame: Other: SIMBAD Extended: NO Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2015.5 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 16990( 2) - 18-Jul-2022 15:00:29 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type SPIRAL Pattern_Purpose DITHER Number_Of_Points 21 Point_Spacing 0.42 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 11.0 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 16990( 2) - 18-Jul-2022 15:00:29 - [ 5] Visit: 01 Visit Requirements: ORIENT 270D TO 270 D; BETWEEN 01-FEB-2023:00:00:00 AND 31-MAY-2023:00:00:00 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 NAME-SGR-A WFC3/IR MULTIAC IR-FIX F153M SAMP-SEQ=STEP50, NSAMP=11 1 DEF PATTERN 1 1 CUM (6283.882 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 1 none none none 1 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 2 none none none 1 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 3 none none none 1 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 4 none none none 1 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 5 none none none 1 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 6 none none none 1 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 7 none none none 1 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 8 none none none 2 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 9 none none none 2 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 10 none none none 2 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 11 none none none 2 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 12 none none none 2 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 13 none none none 2 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 14 none none none 2 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 15 none none none 3 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 16 none none none 3 N/A CUM 16990( 2) - 18-Jul-2022 15:00:29 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 17 none none none 3 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 18 none none none 3 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 19 none none none 3 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 20 none none none 3 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 21 none none none 3 N/A CUM 16990( 2) - 18-Jul-2022 15:00:29 - [ 7] Visit: 02 Visit Requirements: ORIENT 90D TO 90 D; BETWEEN 01-JUL-2023:00:00:00 AND 30-NOV-2023:00:00:00 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 NAME-SGR-A WFC3/IR MULTIAC IR-FIX F153M SAMP-SEQ=STEP50, NSAMP=11 1 DEF PATTERN 1 1 CUM (6283.882 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 1 none none none 1 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 2 none none none 1 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 3 none none none 1 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 4 none none none 1 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 5 none none none 1 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 6 none none none 1 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 7 none none none 1 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 8 none none none 2 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 9 none none none 2 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 10 none none none 2 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 11 none none none 2 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 12 none none none 2 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 13 none none none 2 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 14 none none none 2 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 15 none none none 3 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 16 none none none 3 N/A CUM 16990( 2) - 18-Jul-2022 15:00:29 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 17 none none none 3 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 18 none none none 3 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 19 none none none 3 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 20 none none none 3 N/A CUM NAME-SGR-A 1 WFC3/IR MULTIAC IR-FIX F153M 21 none none none 3 N/A CUM 16990( 2) - 18-Jul-2022 15:00:29 - [ 9] Summary Form for Proposal 16990 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/IR ------------------------------------------------------------------------------------------------------------------------------------ Opmodes MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters NSAMP=11, SAMP-SEQ=STEP50 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 01-FEB-2023:00:00:00 AND 31-MAY-2023:00:00:00, BETWEEN 01-JUL-2023:00:00:00 AND 30-NOV-2023:00:00:00, ORIENT 270D TO 270 D, ORIENT 90D TO 90 D, PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F153M ------------------------------------------------------------------------------------------------------------------------------------ Target Names NAME-SGR-A ------------------------------------------------------------------------------------------------------------------------------------