0Assigned ID: 419
----- Attempting Submission 1 (Fri Mar 06 08:28:29 GMT 2020) -----
HST Phase I Proposal 419 successfully submitted.
Receipt: # 419-1
----- Attempting Submission 2 (Fri Mar 06 17:05:42 GMT 2020) -----
HST Phase I Proposal 419 successfully submitted.
Receipt: # 419-2
----- Attempting Submission 3 (Fri Mar 06 18:42:40 GMT 2020) -----
HST Phase I Proposal 419 successfully submitted.
Receipt: # 419-3
----- Attempting Submission 4 (Fri Mar 06 19:07:36 GMT 2020) -----FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser
FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser
FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser
FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser
FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser
FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser
FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser
FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser
FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser
FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browserresubmission after the approval for my Major Change Request on the roll angle restriction for Carina II
(from no restriction to 0-65 deg, 140-245 deg, 320-359.999 deg)2113045233----- Attempting Submission 1 (Mon Jun 29 19:53:06 GMT 2020) -----
----- Attempting Submission 2 (Thu Jul 16 19:59:43 GMT 2020) -----These warnings are coming from making the UVIS image background at least 20 e-/pix for each exposure.Near Field Cosmology with Ultra-faint Dwarfs: Patchy Reionization and Sub-Solar Initial Mass FunctionObservations of the ultra-faint dwarfs (UFDs), as relics of the epoch of reionization, allow us to probe the earliest epochs of star formation (SF). In particular, the UFDs in low density environments for most of their lifetimes provide unique tools to probe the effects of early environmental conditions on the SF histories (SFHs) of the UFDs and their sub-solar initial mass function (IMF) because they likely maintain the best `fossil' record of early local environments.
We propose to obtain deep ACS and UVIS imaging in F606W and F814W for 2 LMC satellite UFDs that are on their first approach to our Galaxy, and thus resided in the outskirts of the Local Group at high redshift. This program is designed to identify systematic differences in the stellar populations of recently captured UFDs vs. long-term MW satellites (data available from previous programs) by using high-fidelity color-magnitude diagrams constructed from deep HST imaging as well as spectroscopically measured metallicity distribution functions. We will: (1) Establish whether SF is quenched at different times with different rate in UFDs in low density environment at early times, probing the patchiness of reionization by directly comparing with theoretical predictions; (2) Identify variations in the sub-Solar IMF across UFDs born in different environments; (3) Pave the way for a more accurate constraint on the MW halo mass.Our basic observing strategy is to reach S/N of > 100 at the oMSTO in F606W and F814W filters in ACS/WFC, allowing us to measure the detailed ancient SFHs and to explore the sub-Solar (down to a half solar) stellar IMF. Both Carina 2 and Hydrus 1 have half-light radii greater than the ACS FOV, and thus we add an extra one pointing for Hydrus 1 and two pointings for Carina 2 with parallel observations with WFC3/UVIS to observe sufficient number of member stars in each galaxy.
Each pointing is made up of 2 dithered F606W exposures, and 2 dithered F814W exposures to eliminate hot pixels and CR hits in the combined images. We need two filter data to make CMDs to measure SFHs and to separate target stars from foreground/background contaminants. Our choice of filters (F606W and F814W) is the same as previous SFH programs of MW satellites, enabling us to use stellar population templates observed in these same filters to minimize systematic errors for relative ages when comparing populations and thus facilitating direct comparison with other MW satellites from previous programs. The depth of our data will be comparable to ohter HST observations used for MW satellites' sub-solar IMF studies.Our team has extensive experience with measuring SFHs from CMDs constructed from HST imaging (Choi, Dalcanton, Sacchi, Weisz, Williams), studying reionization using local analogs of high-z dwarfs (Choi, Simon, Weisz), and dynamical modeling of MW satellites (Besla, Kallivayalil, Li, Pace, Patel, Richstein, Sohn, Zivick). Dr. Weisz is an expert in the stellar initial mass function. Drs. Jeon and Wetzel are experts in modeling the SFHs of ultra-faint dwarfs using high-resolution cosmological simulations that include reionization. Drs. Choi, Nidever, and van der Marel are experts in the Magellanic system. Drs. Nidever and Simon are experts in stellar chemistry. This project will be led by Dr. Choi.Galaxies6falsefalsefalsefalsefalsefalsefalseSUPPORTEDGALAXYDWARF SPHEROIDALNOJ2000J2000GALAXYDWARF SPHEROIDALJ2000J2000GALAXYDWARF SPHEROIDALJ2000J2000GALAXYDWARF SPHEROIDALJ2000J2000GALAXYDWARF SPHEROIDALJ2000J2000ACS/WFCImagingNoNoF606WACS/WFCImagingNoNoF814WWFC3/UVISImagingNoNoF606WWFC3/UVISImagingNoNoF814WACS/WFCImagingNoNoF606WACS/WFCImagingNoNoF814WWFC3/UVISImagingNoNoF606WWFC3/UVISImagingNoNoF814WACS/WFCImagingNoNoF606WACS/WFCImagingNoNoF814WWFC3/UVISImagingNoNoF606WWFC3/UVISImagingNoNoF814WACS/WFCImagingNoNoF606WACS/WFCImagingNoNoF814WWFC3/UVISImagingNoNoF606WWFC3/UVISImagingNoNoF814WACS/WFCImagingNoNoF606WACS/WFCImagingNoNoF814WWFC3/UVISImagingNoNoF606WWFC3/UVISImagingNoNoF814W/private/var/folders/k6/2mtypjnd4gscsrvl5hwx1hhr0002dc/T/OPVisit3199502284752157000.xmlHst Same orient constraint links visits (01 02 03)The scheduling data was generated by CASM 28.2.CASM was run in Phase II mode.(Tic-Visit
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