0Assigned ID: 336
----- Attempting Submission 1 (Fri Apr 05 05:01:25 GMT 2019) -----
HST Phase I Proposal 336 (M101_HST.apt) successfully submitted.
Receipt: # 336-1
----- Attempting Submission 2 (Fri Apr 05 21:46:53 GMT 2019) -----
HST Phase I Proposal 336 (M101_HST.apt) successfully submitted.
Receipt: # 336-2
----- Attempting Submission 3 (Fri Apr 05 21:57:04 GMT 2019) -----
HST Phase I Proposal 336 (M101_HST.apt) successfully submitted.
Receipt: # 336-3
----- Attempting Submission 4 (Fri Apr 05 22:21:47 GMT 2019) -----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 browserWe have added flash to some WFC3 exposures. Please check to see if things are correct.-68023854----- Attempting Submission 1 (Mon Jul 22 20:44:01 GMT 2019) -----
----- Attempting Submission 2 (Sun Sep 22 16:47:50 GMT 2019) -----I believe I have discussed this in my 'Submission Comments'. Please let me know if you still think corrections should be made.The Satellite Luminosity Function of M101 into the Ultra-Faint Dwarf Galaxy RegimeWe request 4 orbits of HST/ACS to image, in resolved stellar light, four diffuse dwarf candidates that recent tentative distance measurements (using the surface brightness fluctuation technique) indicate may be associated with M101, a Milky Way analog at D=7 Mpc. These four dwarfs are the only remaining viable satellites of M101 down to M_V ~ -7 mag, out of a complete sample drawn from a semi-automated ground-based search which conducted extensive simulations to assess the efficiency in their detection. This dataset will allow us to measure tip of the red giant branch (TRGB) distances, luminosities and structural parameters for these dwarfs, and will result in a complete satellite luminosity function for M101 out to a galacocentric radius of 150 kpc and down to the ultra-faint dwarf galaxy regime (M_V ~ -7 mag). Such a complete luminosity function has been only obtained for the Local Group to date. The current M101 satellite system is very sparse in comparison to the Milky Way, M31 and cosmological simulations, and a confirmation of its properties will provide additional constraints on Cold Dark Matter predictions at these small galaxy scales.The observations are going to be performed with ACS/WFC (primary) and WFC3/UVIS (parallel). We request imaging in F606W and F814W filters (broad V and I) for both instruments, in order to compute accurate TRGB distances for our targets and characterize their stellar content (star formation histories and metallicities), while optimizing the exposure times. The parallel pointings will allow us to observe a field region next to our targets. We will thus be able to estimate more precisely the number of background/foreground contaminants present in our ACS fields.
Our goal is to obtain a SNR of ~5 at ~1 mag below the TRGB in I band, assuming that the TRGB is found at M_I = ~-4.0 and M_V = ~-2.5, in order to derive precise distance measurements, structural properties and average metallicities. With the requested SNR, we will obtain distance uncertainties as low as ~0.2 mag, corresponding to ~200 kpc at the distance of M101. We stress that, even for the faintest of our targets we expect ~25 stars in the upper 1 mag below the TRGB.
Since the exact distances for our targets are unknown, the candidate M101 satellites are assumed to be at the distance of M101 (~7 Mpc). Given their low masses, these are expected to be metal-poor objects, thus having average colours of V - I ~ 1.5. At this distance, the TRGB is found at a magnitude of I ~ 25.2 and V ~ 25.9. The exposures to obtain the required SNR at 1 mag below the TRGB for both bands are ~ 1200 sec in F606W and ~ 900 sec in F814W (as computed with the latest version of the ACS ETC), which result in one orbit per target. Each exposure will be split in two with a dither pattern in order to subsequently remove detector defects and improve the PSF sampling. We have checked that the charge transfer efficiency losses of ACS do not significantly affect our observations (at most 10% loss of flux).
This program is resilient to two-gyro mode, we believe. Our visits are 1-orbit, and we have no ORIENT requirements. Nor does this program have time constraints (other than the baseline excitement of the science!). We can also achieve our science goals with a longer acquisition time, if necessary.Mr. Paul Bennet is a Graduate Student working with Prof. David Sand and is the principle devloper of the semi automated detection algorithm that intially detected the dwarfs in this proposal. Prof. David Sand is an expert in near field cosmology and has expertise in HST data reduction for ACS and WFC3 which are the primary and parallel instruments used in this proposal. Dr. Denija Crnojevic is an expert in near field cosmology and has led several previous HST observing campaigns leading to 5 papers published over the past decade based on HST data (e.g., Crnojevic et al. 2010, 2013, 2014, 2016, 2019; Sand et al. 2014, 2015). Dr. Spekkens, Prof. Zaritsky and Mr. Karunakaran have been involved in this M101 project, and they are experts in low surface brightness galaxies in both visible light as well as in their gas content.Stellar Populations6falsefalsefalsefalsefalsefalsefalseSUPPORTEDGALAXYDWARF SPHEROIDALYESJ2000J2000GALAXYDWARF SPHEROIDALYESJ2000J2000GALAXYDWARF SPHEROIDALYESJ2000J2000GALAXYDWARF SPHEROIDALJ2000J2000ACS/WFCImagingNoNoF606WACS/WFCImagingNoNoF814WWFC3/UVISImagingNoNoF606WWFC3/UVISImagingNoNoF814WACS/WFCImagingNoNoF606WACS/WFCImagingNoNoF814WWFC3/UVISImagingNoNoF606WWFC3/UVISImagingNoNoF814WACS/WFCImagingNoNoF606WACS/WFCImagingNoNoF814WWFC3/UVISImagingNoNoF606WWFC3/UVISImagingNoNoF814WACS/WFCImagingNoNoF606WACS/WFCImagingNoNoF814WWFC3/UVISImagingNoNoF606WWFC3/UVISImagingNoNoF814WPOS-TARGDITHER0.364Two-point dither. No need to fill chip gap.LINEfalsefalse247.23ACS-WFC-DITHER-LINE1false/Users/dsand/Dropbox/cycle27_apt/15858/OP-cache/15858_phaseII_Sep182019-v01.xmlThe scheduling data was generated by CASM 27.2.CASM was run in Phase II mode.(Tic-Visit
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