An emerging population of stripped, but isolated, stellar systems in the Virgo Cluster

0 Assigned ID: 556 ----- Attempting Submission 1 (Fri Apr 07 15:04:12 GMT 2017) ----- HST Phase I Proposal 556 (blueblobs.apt) successfully submitted. Receipt: # 556-1 ----- Attempting Submission 2 (Fri Apr 07 21:51:10 GMT 2017) ----- Slight adjustment to Visit 4 as requested. -454165058 ----- Attempting Submission 1 (Thu Jul 13 18:37:37 GMT 2017) ----- HST Phase II Proposal 15183 (blueblobs.apt) successfully submitted. Receipt: # 15183-1 ----- Attempting Submission 2 (Tue Aug 01 18:03:22 GMT 2017) ----- ----- Attempting Submission 3 (Wed Aug 02 23:12:00 GMT 2017) ----- ----- Attempting Submission 4 (Thu Dec 06 20:08:02 GMT 2018) ----- ----- Attempting Submission 5 (Fri Dec 07 00:03:49 GMT 2018) ----- An emerging population of stripped, but isolated, stellar systems in the Virgo Cluster We have recently uncovered a unique dwarf-like galaxy in the Virgo Cluster: a diffuse, low mass system with solely young stellar populations located at least 350 kpc from the nearest massive galaxy. We hypothesize that this galaxy may be formed from ram pressure stripped gas, making it distinct from other, similar systems such as tidal dwarfs. We request 10 orbits of HST/ACS to image a well-defined sample of five similar objects in Virgo which we postulate may also be ``ram pressure dwarfs." This data will allow us to measure the basic physical properties of this emerging class of objects, including their structure, luminosity, and star formation history. HST data is also needed to constrain any old stellar population; if present, it would be indicative of a standard dwarf galaxy origin rather than newly formed stars from stripped gas. With these observations we will better understand the fate of stripped gas in the cluster environment, and test whether we have uncovered a new class of isolated stellar systems formed through cluster interactions. Our primary science goal is to determine the basic physical properties -- luminosity, structure, and star formation history -- of a newly discovered sample of isolated blue star-forming regions (which we have dubbed "ram pressure dwarfs") projected onto the Virgo Cluster. Aside from a relatively standard star formation history analysis, we also wish to constrain any old stellar population, for which we have two separate approaches -- both a direct search for resolved red giant branch stars and an inventory of all of the diffuse stellar light associated with each object. We aim for comparable data to that of AGC 226067 (Sand et al. 2017), the prototype of the stellar systems we are investigating. We thus will request a single orbit of ACS imaging in both the F606W and F814W bands for each of our five targets (S/N~5 at 26.7-26.8 mag in both bands, according to the ETC). Optical magnitudes and colors (F606W, F814W) will allow us to measure the structure of the stellar systems, and to constrain their star formation history (see Fig 1; Sand et al. 2017). Additionally, we will use the resulting color magnitude diagrams and diffuse light component of each object to constrain any old stellar component. Stellar Populations 6 false false false false false false false SUPPORTED GALAXY AMORPHOUS IRREGULAR YES J2000 J2000 GALAXY AMORPHOUS IRREGULAR YES J2000 J2000 GALAXY AMORPHOUS IRREGULAR YES J2000 J2000 GALAXY AMORPHOUS IRREGULAR YES J2000 J2000 GALAXY AMORPHOUS IRREGULAR YES J2000 J2000 ACS/WFC Imaging No No F814W ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F814W ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F814W ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F814W ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F814W ACS/WFC Imaging No No F606W POS-TARG DITHER 0.262 LINE 0.192 false false 68.14 4 18.39 ACS-WFC-DITHER-BOX 2

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