0Assigned ID: 853
----- Attempting Submission 1 (Fri Mar 06 22:22:32 GMT 2020) -----
HST Phase I Proposal 853 successfully submitted.
Receipt: # 853-1
----- Attempting Submission 2 (Fri Mar 06 22:36:17 GMT 2020) -----Be very careful mixing POS TARG and Center_Pattern = Yes
Be very careful mixing POS TARG and Center_Pattern = Yes0----- Attempting Submission 1 (Tue Jun 30 10:41:44 GMT 2020) -----We move the galaxy center slightly from the center of UVIS2 such that the galaxy itself does not fall on the chip gap but more area around the galaxy is covered within the WFC3/UVIS FOV. This will allow us to potentially image more compact sources that might end up being associated globular clusters.Imaging of an apparent ''globular cluster galaxy''Recently a remarkable low surface brightness galaxy, NGC5846-UDG1, was discovered in archival ground-based CFHT data. The galaxy has a low stellar mass (~10^8 solar masses), a large size (r_e=1.8 kpc), and an unprecedented number of compact sources that resemble globular clusters. Keck spectroscopy confirms the association of the globular clusters and the diffuse light: they are at a common radial velocity of ~2000 km/s, close to the group velocity of ~1900 km/s. Based on the current ground-based imaging and spectroscopic data the galaxy might have up to 30% of its light in the form of globular clusters, significantly higher than any other galaxy known to date. Taking diffusion of low mass clusters into account, it is possible that the galaxy consisted solely of ~100 globular clusters when it formed. Here we request 2 WFC3/UVIS orbits to study this extreme galaxy along with its unusual globular cluster system. With WFC3/UVIS we will measure the sizes, colors, ellipticities and luminosity function of the clusters. These properties will be compared to the globular cluster systems of other galaxies (and in particular other Ultra Diffuse Galaxies), to determine whether NGC5846-UDG1's globular clusters have similarities to those in other galaxies or represent something entirely new. We will also use the data to better determine the structure and morphology of this enigmatic galaxy in order to put further constraints on its dynamical state.The program is ought to obtain F606W and F475W imaging of a single ultra-diffuse galaxy which seems to host an outstanding number of bright globular clusters. The goal is to obtain photometry of these compact point sources over the entire WFC3/UVIS field of view.
Instrumental setup: We will use WFC3/UVIS, and the F606W and F475W filters. The F606W filter is the primary filter for selecting globular clusters, with the F475W - F606W colors of compact objects helping (in conjunction with their sizes and the Keck spectroscopy) to distinguish them from background galaxies. A single pointing is sufficient as the candidate fits well inside the UVIS field of view.
Total orbits and observing strategy: the target is observed for two orbits in a single visit, with one orbit per filter in two filters (F606W and F475W). We have no ORIENT constraints.
We will be using the WFC3-UVIS-MOS-DITH-LINE pattern with 2 primarty points and 2 sub-pattern points. This allows both dithering over the chip gap and includes a secondary pattern which adds a sub-pixel dither to each of the primary steps.
Apertures and POSTARGs: the galaxy is observed near UVIS2 with a slight shift from the chip center.Shany Danieli who lead this proposal is an expert in detecting and studying low surface brightness galaxies such as ultra diffuse galaxies (UDGs) and dwarf galaxies. Pieter van Dokkum, Johnny Greco and Shany Danieli have extensive experience in carrying out detailed studies of UDGs, their globular cluster systems and kinematics, including studies that used HST data (van Dokkum et al. 2015, 2016, 2017, 2018, 2019, Danieli et al. 2018, 2019, Greco et al. 2018, Cohen et al. 2018). Jean Brodie is an expert in globular clusters and galaxy formation. Charlie Conroy is an expert on stellar populations and developed the models. Aaron Romanowsky is an expert in UDGs and their properties. Pieter van Dokkum and Roberto Abraham are experts in the low surface brightness universe and the general area of galaxy formation. Johnny Greco is an expert on low surface brightness galaxies, SBF measurement and stellar populations of dwarf galaxies. Zili Shen is an expert in LRIS spectroscopy and Jonah Gannon is an expert in stellar kinematics of low surface brightness galaxies with KCWI.Galaxies6falsefalsefalsefalsefalsefalsefalseSUPPORTEDGALAXYLSBJ2000J2000WFC3/UVISImagingNoNoF475WWFC3/UVISImagingNoNoF606WPOS-TARGDITHERDITHER22.4WFC3-UVIS-MOS-DITH-LINEfalsetrue0.119285.754POS-TARGWFC3-UVIS-MOS-DITH-LINE33.6061true/Users/shanydanieli/Drive/2020/proposals/hst_cycle28/ngc5846-udg1/phase2/OP-cache/16284_phase2-v01.xmlThe scheduling data was generated by CASM 28.2.CASM was run in Phase II mode.(Tic-Visit
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