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Please specify your scheduling constraints or 'No Constraints' on all Observation forms.0Assigned ID: 1034
----- Attempting Submission 1 (Wed Jun 26 12:09:26 GMT 2019) -----Joint NRAO/HSTFLASH 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 browserAdded in FLASH for WFC3/UVIS exposures.885719753----- Attempting Submission 1 (Tue Jul 23 18:38:15 GMT 2019) -----
----- Attempting Submission 2 (Sun Sep 22 20:43:48 GMT 2019) -----Added in FLASH for WFC3/UVIS exposures.Ultra-Diffuse Galaxy Formation through InteractionsWe request D-configuration HI observations as well as HST data to image two ultra-diffuse galaxies (UDGs) which are associated with tidal material connected to a larger galaxy halo. These dwarfs provide evidence that UDGs can form via galaxy interactions, although it is not clear whether they are normal dwarf galaxies that have been `puffed up' during the interaction or if they are tidal dwarf galaxies, the dark matter-free stellar aggregations that can result from gas-rich major galaxy encounters. Alternatively, these galaxies may have formed as UDGs through some other mechanism, and are now being stripped by a larger galaxy halo. The deep VLA observations are essential for spatially correlating HI emission with each dwarf and its stream, which would bolster the tidal dwarf galaxy hypothesis. The HST observations will allow for a detailed morphological analysis of each interacting dwarf and its stellar stream, and will also measure their globular cluster content -- a powerful discriminant between these formation scenarios. The proposed observations will point to one of the formation mechanisms of the mysterious class of UDGs.The observations are going to be performed with the ACS/WFC (primary) and WFC3/UVIS (parallel). We request imaging in F555W and F814W filters for both instruments in order to both measure the detailed morphology of each ultra-diffuse dwarf (along with its stellar stream) and their globular cluster (GC) content. The parallel WFC3 pointings will allows us to observe a field region next to our ultra-diffuse galaxy targets and will be invaluable to characterize the 'background' of points sources with consistent magnitudes and colors as the GCs we wish to identify.
Each target/visit is two orbits, with the first orbit devoted to F555W and the second to F814W. We use a standard four-point dither box for each orbit, with sub-pixel dithers in order to get closer to the native resolution of ACS. This is vital, as one method we will use to identify globular clusters is to measure slight deviations from a true point source. Most globular clusters at the distance to our targets will be very slightly resolved, and we will use a standard 'concentration index' to identify them (basically, the difference in magnitude between two apertures).
We have implemented some loose ORIENTs in order to include some portion of the stream associated with each dwarf, and its connection to the main parent galaxy.
This program is relatively resilient to two-gyro mode, we believe. Our visits are 2-orbits, and we have loose ORIENT constraints. 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.
Note that this dataset was requested through the joint NRAO program. We will also be acquiring VLA HI observations of the two ultradiffuse galaxy targets in this proposal to get a more complete picture and narrow down the formation scenarios of these two remarkable galaxies. We do not require concurrent VLA and HST imaging.6falsefalsefalsefalsefalsefalsefalseSUPPORTEDGALAXYDWARF SPHEROIDALYESJ2000J2000GALAXYDWARF SPHEROIDALYESJ2000J2000ACS/WFCImagingNoNoF555WACS/WFCImagingNoNoF814WWFC3/UVISImagingNoNoF555WWFC3/UVISImagingNoNoF814WACS/WFCImagingNoNoF555WACS/WFCImagingNoNoF814WWFC3/UVISImagingNoNoF555WWFC3/UVISImagingNoNoF814WPOS-TARGDITHER0.262LINE0.192falsefalse68.14418.39ACS-WFC-DITHER-BOX1falseThe scheduling data was generated by CASM 27.2.CASM was run in Phase II mode./private/var/folders/lk/kgyb23rx78z9r8t653drxmfw0000gn/T/OPVisit10417605223458880627.xml(Tic-Visit
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