0Assigned ID: 4697
----- Attempting Submission 1 (Wed May 24 21:57:29 GMT 2023) -----
HST Phase I Proposal 4697 successfully submitted.
Receipt: # 4697-1
----- Attempting Submission 2 (Wed May 24 23:23:02 GMT 2023) -----
HST Phase I Proposal 4697 successfully submitted.
Receipt: # 4697-2
----- Attempting Submission 3 (Wed May 24 23:56:29 GMT 2023) -----0----- Attempting Submission 1 (Thu Sep 14 17:37:30 GMT 2023) -----Moving beyond the Milky Way: Enabling Cross-Observatory Proper Motion Determinations with HST and JWSTHST has made unique contributions to our understanding of the dynamical evolution of the Milky Way and its constituent satellites, globular clusters, halo stars and tidal streams. Proper motions enabled by multi-epoch HST observations have been used to probe the nature of dark matter, the epoch of reionization, and correlated satellite infall. While Gaia now, too, provides unparalleled astrometric precision for the Milky Way, at outer halo distances this is only for intrinsically bright stars. Moving beyond the Milky Way halo will only be possible by utilizing long baselines with HST or by extending these baselines using another facility, such as JWST or Roman, in tandem with a first epoch from HST. Thus, it is imperative that we calibrate cross-observatory techniques to measure absolute proper motions. Here, we request 8 orbits with ACS/WFC and 3.27 hours with JWST's NIRCam for Draco II, an ultra-faint dwarf galaxy, and WLM, a star-forming galaxy. Both objects already have an epoch of ACS/WFC data, as well as publicly available NIRCam data from the Resolved Stellar Populations Early Release Science program. We will use the newly requested data to measure an HST-HST proper motion for each dwarf. This proper motion will be used as a "ground truth" to investigate and calibrate (i) detector-based systematics and (ii) reference frame-based systematics, in combining HST and JWST data. We stress the urgency of getting these observations now while HST is operating well. Such cross-observatory calibrations will be extremely difficult if the astrometric capabilities of HST degrade.We will observe Draco II - an ultra-faint dwarf galaxy - and WLM - a star-forming, isolated dwarf galaxy - with ACS/WFC, using 4 orbits for each target. Both objects already have an epoch of ACS/WFC data, as well as deep NIRCam data in two SW filters. This new data can be used to measure an HST-HST proper motion for each dwarf galaxy, which can serve as a "ground truth" to investigate and calibrate (i) detector-based systematics and (ii) refrence frame-based systematics in combining HST and JWST data. In this program, each target field will be observed using the same telescope pointings and orientations as the first-epoch images to maximize the overlaps of the observed fields between first- and second-epoch data. This will also minimize position-dependent uncertainties originating from imperfect CTE and geometric distortion corrections. These observations will be made in the F814W filter, which has proven to give the best astrometric handle on background galaxies, and which is also one of the filters used for the first-epoch observations of both targets. Two exposures per orbit will be taken in order to complete and eight-point dither, allowing for deep single-exposure images that together allow for a well-sampled PSF.PI Jack Warfield is a third-year graduate student at the University of Virginia (UVA) working with Dr. Nitya Kallivayalil (admin PI) on the HST Treasury Program of M31 satellites as well as the JWST ERS program 1334 on resolved stellar populations (including Draco II and WLM). PI Warfield has been developing techniques to measure proper motions from first-epoch HST and second-epoch JWST images, as well as a technique that uses Gaia foreground stars as references for proper motion measurements. He will lead the calibration process for the cross-observatory proper motion measurements. Dr. Nitya Kallivayalil and Dr. Tony Sohn are experts in astrometry and of measuring proper motions from HST imaging. Dr. Kallivayalil is a leading expert in HST astrometry and proper motions and is the PI of the HST Treasury program of MW satellites. Dr. Sohn is an expert at creating galaxy spread functions to locate the centers of background galaxies for use as proper motion reference frames. Drs. Kallivayalil and Sohn will aid in the astrometric calibration. Dr. Garling has experience comparing observations of Local Group dwarfs to cosmological simulations and semi-analytic models allowing him to advise on interpretation of Local Group dynamics.
Dr. Andrew Dolphin is an expert on resolved stellar populations and is the author of DOLPHOT, the most widely used PSF photometry reduction routine for HST. Dr. Dolphin has also been developing modules of DOLPHOT to work with JWST data from NIRCam and NIRISS. Dr. Jay Anderson creates PSF models for HST and JWST and is the author of ePSF, another stellar PSF photometry package we will use in this program.
Dr. Martha Boyer is an expert on stellar populations in nearby dwarf galaxies and has PI'd several HST and JWST programs on this topic. She is also the lead of the NIRCam branch at STSCI.
Dr. McQuinn has deep expertise with resolved star photometry with both HST and JWST NIRCam imaging and is part of the photometry team on the ERS program for Draco II and WLM.
Dr. Correnti is an expert on resolved stellar populations in the near-IR, having led multiple previous HST GO programs, and photometric data reduction of crowded fields using different space telescope instruments. He was an instrument scientist for NIRcam, and is also a member of the JWST Stellar Populations ERS team, with extensive and unique expertise on NIRcam data acquisition and reduction.
Dr. Cohen is an expert in precision photometry of resolved stellar populations in the Local Volume, and has led multiple previous HST GO programs.
Dr. Evan Skillman is a leader in resolved stellar populations of Local Group galaxies and is PI of the largest HST survey of the M31 dSphs to date.
Dr. Geha is an expert observer of resolved stars in the Local Group and has performed extensive analysis on their stellar populations.
Dr. Daniel Weisz is an expert on observations of resolved stellar populations with HST, the Local Group, and the formation and evolution of dwarf galaxies. He has worked on over 1500 orbits of HST data of resolved stellar populations and has been the first author of more than 10 papers using HST observations of nearby galaxies over the past decade.
Dr. Savino is an expert in photometric reduction processes and SFHs in the Local Volume.
Dr. Sandstrom is an expert in the SFHs and interstellar medium in nearby galaxies. Dr. Cole is an expert in stellar evolution and SFHs of dwarf galaxies.
Co-I Max Newman has experience working with HST data, has worked extensively with tools to measure photometry in JWST images as part of the program (JWST-DD-1334), and is leading the work on the JWST program (JWST-GO-1638) to calibrate the TRGB in NIRCam filters. Ms. Hannah Richstein is a fifth-year graduate student leading the creation of photometric catalogs from the dwarf galaxies in the HST MW Treasury Program. Drs. Boyer, McQuinn, Correnti, Cohen, Skillman, Geha, and Weisz, Savino, Sandstrom, Cole, and co-Is Newman and Richstein will lend their expertise in the photometric reduction and analysis.Galaxies6falsefalsefalsefalsefalsefalsefalse3.26875trueSUPPORTEDGALAXYDWARF SPHEROIDALThis object was generated by the targetselector and retrieved from the SIMBAD database.J2000J2000M_V=-2.9GALAXYDWARF ELLIPTICALJ2000J2000ACS/WFCImagingNoNoF814WACS/WFCImagingNoNoF814WThe scheduling data was generated by CASM 31.1.CASM was run in Phase II mode.1709695322000243.42690149999999(Tic-Visit
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