0Assigned ID: 4544
----- Attempting Submission 1 (Wed May 24 19:48:24 GMT 2023) -----
HST Phase I Proposal 4544 successfully submitted.
Receipt: # 4544-1
----- Attempting Submission 2 (Wed May 24 22:44:41 GMT 2023) -----
HST Phase I Proposal 4544 successfully submitted.
Receipt: # 4544-2
----- Attempting Submission 3 (Wed May 24 23:48:13 GMT 2023) -----No Parallel Exposures Specified in Parallel Exposure Group
No Parallel Exposures Specified in Parallel Exposure Group
No Parallel Exposures Specified in Parallel Exposure Group
No Parallel Exposures Specified in Parallel Exposure GroupWith the permission from Patricia Royle, I removed the coordinated parallels, and made the required cuts to avoid overrunning the orbit.-419812473----- Attempting Submission 1 (Mon Sep 11 19:22:16 GMT 2023) -----
HST Phase II Proposal 17514 successfully submitted.
Receipt: # 17514-1
----- Attempting Submission 2 (Tue Oct 03 03:01:55 GMT 2023) -----
----- Attempting Submission 3 (Tue Feb 20 15:07:03 GMT 2024) -----
----- Attempting Submission 4 (Mon Mar 04 16:15:24 GMT 2024) -----
----- Attempting Submission 6 (Mon Jun 17 15:25:41 GMT 2024) -----With the permission from Patricia Royle, I removed the coordinated parallels because of the additional complexity the parallels present to updating your Phase 2 for visit 52Three new isolated, faint and star-forming dwarf galaxies beyond the Local GroupThe Local Group satellite dwarf galaxies are frequently used as benchmarks for testing galaxy formation and evolution theories on the smallest scales because they are the lowest-mass galaxies for which we have detailed observations. However, the vast majority of these dwarfs have been affected by the Local Group environment. If we want to understand the physical mechanisms driving the evolution of low-mass galaxies, it is essential to study pristine isolated dwarf galaxies beyond the Local Group as a control sample. Unfortunately, identifying such galaxies in the field is extremely challenging due to their extreme faintness. To date, Leo P is the only known isolated, star-forming galaxy that is independent of group dynamics in an extremely low-mass regime (<10^6 Msun) but close enough at 1.6 Mpc to be studied with resolved stars. With only one system, it is challenging to draw broad conclusions about low-mass star-forming galaxies evolving in isolation.
We request three orbits of HST/ACS imaging (F606W+F814W) to follow up three new nearby isolated, faint, star-forming dwarf galaxies discovered in ground-based surveys. The galaxies are likely just beyond the edge of the Local Group, with apparent morphologies and colors strikingly similar to Leo P. HST imaging is essential to the determination of secure distances, measurement of basic physical properties, and measurement of star formation histories of these three newly discovered dwarfs. The requested observations will put these three galaxies into context with other dwarf galaxies in and beyond the Local Group, providing a rare opportunity to assess the impact of environment on low-mass systems.The observations are going to be performed with ACS/WFC (primary) and WFC3/UVIS (parallel) to match previous observations of faint dwarfs beyond the Local Group (e.g. Weisz et al. 2014, Hargis et al. 2020, Danieli et al. 2017, Bennet et al. 2019, Crnojevic et al. 2019, Mutlu-Pakdil et al 2022). 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, 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.
Given the small size of each target (<1 arcmin), one pointing is sufficient to cover the entire spatial extent of each galaxy. Each dwarf will be placed on one of the ACS/WFC chips, and small dithers between exposures will remove detector defects and improve the PSF sampling. Given that the possible distance range for our targets is ~1-3 Mpc, we use existing HST ACS data of Local Volume dwarfs at <3 Mpc (NGC253 dwarfs [GO-14259, GO-15938], CenA dwarfs [GO-13856], MADCASH dwarfs [GO-15228]) to guide our observational request and ensure that the depth is sufficient for the science goals of this proposal.
The archival ACS data for similar limiting magnitudes were obtained with 2 CR-SPLIT exposures of 1200 sec in F606W and 900 sec in F814W. The required exposure times nicely fit into one orbit per object after taking into account realistic overheads. With these exposures, the achieved SNR given by the ACS ETC is ~10 at 1 mag below the TRGB for both bands (assuming a distance of 3~Mpc), with a limiting magnitude of ~27 in F814W, thus fulfilling our requirements. This translates into only a total of three orbits for our three dwarfs. We have checked that the charge transfer efficiency losses of ACS do not significantly affect our observations (at most 10% loss of flux). 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.Dr. Burcin Mutlu-Pakdil has led (and participated in) several previous HST campaigns related to resolved stellar populations of dwarf galaxies that have led to published results. Some we highlight below. She 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. Most recently, she has completed an HST study of five faint and ultra-faint dwarf galaxies around NGC253 at 3.5 Mpc (Mutlu-Pakdil et al. 2022).
Dr. David Sand has been PI and co-PI of over 10 successful HST proposals, and is an expert in near field cosmology. He has extensive experience with HST imaging and has published numerous papers on faint and diffuse dwarf galaxies. He is the one who discovered CorvusI in visual search.
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).
Dr. Alex Drlica-Wagner is a world expert in near field cosmology, finding dwarf galaxies in the Local Group, and survey leader of a large DECam program (DELVE). He played a critical role in discovery of Kamino.
Dr. Jones, Dr. Spekkens and Dr. Karunakaran are experts in low surface brightness galaxies in both visible light as well as in their gas content. They will pursue further HI observations of our targets.
Recently Dr. Jones published an HST study of two nearby ultra-diffuse galaxies (Jones et al. 2021), and also led an HST study of two dwarf-like objects in the direction of the Virgo cluster (Jones et al. 2022).
Dr. Paul Bennet is a postdoctoral researcher who has led two previous M101-focused HST dwarf galaxy campaigns leading to two papers (Bennet et al. 2019, 2020), along with a recently completed study of two isolated dwarf galaxies in the Local Volume (Bennet et al. 2021).
Dr. Annika Peter is a dark matter astrophysicist with expertise in theoretical, simulation, and observational aspects of dark matter physics and dwarf galaxy evolution.
Dr. Catherine Fielder is an expert in the spectral energy distribution of Milky Way-like galaxies. She is currently leading an HST program studying the globular cluster populations of ultra-diffuse galaxies.
Dr. Dennis Zaritsky is an expert on low-mass galaxies and ultra-diffuse galaxies, and Richard Donnerstein is an expert on low-surface brightness galaxy detection algorithms.Stellar Populations and the Interstellar MediumGalaxies6falsefalsefalsefalsefalsefalsefalsefalseSUPPORTEDGALAXYDWARF SPHEROIDALYESJ2000J2000GALAXYDWARF SPHEROIDALYESJ2000J2000GALAXYDWARF SPHEROIDALYESJ2000J2000ACS/WFCImagingNoNoF606WACS/WFCImagingNoNoF814WACS/WFCImagingNoNoF606WACS/WFCImagingNoNoF814WWFC3/UVISImagingNoNoF606WWFC3/UVISImagingNoNoF814WWFC3/UVISImagingNoNoF606WWFC3/UVISImagingNoNoF814WACS/WFCImagingNoNoF606WACS/WFCImagingNoNoF814WWFC3/UVISImagingNoNoF606WWFC3/UVISImagingNoNoF814WThe scheduling data was generated by CASM 32.1.CASM was run in Phase II mode.171350197500080.10391181974092(Tic-Visit
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