Cannot find file /Users/hos/Dropbox/Cycle25/VirgoUDG/VirgoUDG_Cyc25.pdf0Assigned ID: 763
----- Attempting Submission 1 (Fri Apr 07 19:11:24 GMT 2017) -----We have fit in a 4 point DITHER BOX for Visit 05 using POS-TARGS, and unequal exposures. Made small changes to version 1 updating ACS exposures,
and finding we (conservatively!) might need FLASH=1.0 e-. (Or is 19e- OK for ACS? might not need FLASH? 1/5/2018 - no, not needed)
When scheduled, can we 'fill in' the F814W orbits to maximize exposure time?
Many thanks to all at STScI who helped with this. (incl. Aparna, Susana, Tony) Greatly appreciated!
NOTE: these comments still apply 7/20/2017
1/5/2017 - removed FLASH from the short (365s) F475W exposures in Visit 5.1730535647----- Attempting Submission 1 (Thu Jul 20 01:38:43 GMT 2017) -----
HST Phase II Proposal 15258 (HST_15258_PHASE2_4pt.apt) successfully submitted.
Receipt: # 15258-1
----- Attempting Submission 2 (Thu Jul 20 02:05:43 GMT 2017) -----
HST Phase II Proposal 15258 (HST_15258_PHASE2_4pt.apt) successfully submitted.
Receipt: # 15258-2
----- Attempting Submission 3 (Thu Jul 20 15:16:36 GMT 2017) -----
Your proposal could not be saved.
Submission aborted.
----- Attempting Submission 4 (Fri Jan 05 20:23:42 GMT 2018) -----Galaxies at the Extremes: Ultradiffuse Galaxies in the Virgo ClusterThe "ultradiffuse galaxies" (UDGs) recently discovered in massive galaxy clusters presents both challenges and opportunities for our understanding of galaxy evolution in dense clusters. Such large, low density galaxies should be most vulnerable to gravitational destruction within the cluster environment. Thus their presence in cluster cores argues either that they must be stabilized by massive dark halos or else be short-lived objects undergoing rapid transformation, perhaps leading to the formation of ultracompact dwarf galaxies (UCDs) if their destruction leaves only a compact nucleus behind.
We propose deep imaging of four Virgo Cluster UDGs to probe their local environment within Virgo via accurate tip of the red giant branch (TRGB) distances. With a distance precision of 1 Mpc, we will accurately place the objects in the Virgo core, cluster outskirts, or intervening field. When coupled with our extant kinematic data, we can determine whether they are infalling objects or instead have already passed through the cluster core. We will also compare their compact nuclei to Virgo UCDs, and study their globular cluster (GC) populations in detail. Probing three magnitudes beyond the turnover in the GC luminosity function, we will construct larger and cleaner GC samples than possible with ground-based imaging, using the total mass and radial extent of the globular cluster systems to estimate the dark halo mass and tidal radius for each UDG. The new information provided by HST about the local environment and intrinsic properties of these Virgo UDGs will be used in conjunction with simulation data to study cluster-driven evolution and transformation of low density galaxies.The program is to obtain very deep F814W images of a single ultra-diffuse galaxy in the Virgo cluster, and to obtain photometry of very faint point sources over the entire FOV. We are using ACS as primary to get the larger FOV on the target galaxy, and using WFC3 in parallel to obtain a 'background' field necessary for our science goals. LOW-SKY is required due to the higher-than-average sky background for targets near the ecliptic plane, and our need to get high enough S/N for very faint point sources.
Visit locations: For each of the three 2-orbit visits, we are using a small 4 pt ACS-WFC-DITHER-BOX pattern to properly sample the PSF. Between visits, we are using POS-TARGs to create a larger BOX pattern such that we cover the chip gap. The 4th part of this larger box (location 4) is a single orbit (2 exposures only), so I have made a custom DITHER-LINE to match the first two points of the small, subpixel DITHER-BOX pattern.
Exposure times: All of our F814W observations are 2 images per orbit -- there will be 14 individual F814W images, so CR removal should be fine. We have left a few x10s of orbit visibilty open for schedulability. The single orbit in F475W will employ 4 primary+parallel images, but with unequal exposure times.
Roll Angles: We are limited by the target availability for this object, as well as the need for all observations to be made at the same roll angle as the first Visit. We have chosen a rather restricted roll angle range so that we avoid (a) a bright star that lies to the E of VCC 615, and (b) such that the WFC3 parallel fields do not land on a region of bright stars. (the roll angle we used was chosen to co-incide with surprisingly small target visibility).
FLASH: Due to the length of the exposures, we do not need post-FLASH for any of the F814W exposures in either camera. However, some of the shorter F475W exposures in Visit 05 will require some post-FLASH. To conservative determine the appropriate backgrounds, we used the ETC and assumed the faintest possible sky background (MU_V=22.6 for target at 13 degrees ecliptic latitude), and no Earthshine or airglow. For 410S exposures in F475W this becomes 9 e-/pixel (http://etc.stsci.edu/etc/results/WFC3UVIS.im.1012759/). Thus we will need a post-FLASH of 3 e- for the shorter WFC3 F475W exposures. For the ACS, using these same (rather optimistic) conditions, we find a minimum of 19 e-/pixel in the 365s exposures (http://etc.stsci.edu/etc/results/ACS.im.1012739/), requiring a post-FLASH of 1.0 e- for the shorter ACS exposuresGalaxies and the IGM6falsefalsefalsefalsefalsefalsefalseSUPPORTEDGALAXYLSBJ2000J2000ACS/WFCImagingNoNoF814WWFC3/UVISImagingNoNoF814WACS/WFCImagingNoNoF814WWFC3/UVISImagingNoNoF814WACS/WFCImagingNoNoF814WWFC3/UVISImagingNoNoF814WACS/WFCImagingNoNoF814WWFC3/UVISImagingNoNoF814WACS/WFCImagingNoNoF475WWFC3/UVISImagingNoNoF475WACS/WFCImagingNoNoF475WWFC3/UVISImagingNoNoF475WACS/WFCImagingNoNoF475WWFC3/UVISImagingNoNoF475WACS/WFCImagingNoNoF475WWFC3/UVISImagingNoNoF475WPOS-TARGDITHER0.265LINE0.187falsefalse69.05420.67ACS-WFC-DITHER-BOX1falsePOS-TARGDITHER0.262LINEfalsefalse220.67ACS-WFC-DITHER-LINE2falseHst Same orient constraint links visits (01 02 03 04 05)The scheduling data was generated by CASM 25.2.CASM was run in Phase II mode.F814W images, 2 exposures per orbit in DITHER-BOX pattern. Location 1 of 4 different POST TARGS for each of the 4 F814W-related visits. Small ORIENT range dictated by limited target visibility and need to avoid a few bright stars both E and S of the galaxy(Tic-Visit
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