15183( 7) - 05-Mar-2019 15:46:09 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15183 Version: 7 Check-in Time: 05-Mar-2019 15:46:09 STScI Edit Number: 1 Title An emerging population of stripped, but isolated, stellar systems in the Virgo Cluster ------------------------------------------------------------------------------------ Type Cycle GO 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. David J. Sand University of Arizona Y CoI: Prof. Jay Strader Michigan State University N CoI: Kyle Artkop Texas Tech University N CoI: Prof. Anil C. Seth University of Utah N CoI: Dr. Denija Crnojevic Texas Tech University N CoI: Prof. Puragra Guhathakurta University of California - Santa Cruz N CoI: Dr. Elisa Toloba University of the Pacific N CoI: Dr. Nelson Caldwell Smithsonian Institution Astrophysical N Observatory CoI: Dr. Kristine Spekkens Royal Military College of Canada N ------------------------------------------------------------------------------------ Abstract 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. ------------------------------------------------------------------------------------ Observations Description ------------------------ 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 15183( 7) - 05-Mar-2019 15:46:09 - [ 2] 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. ------------------------------------------------------------------------------------ 15183( 7) - 05-Mar-2019 15:46:09 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 BLUECAND1 GALAXY, AMORPHOUS RA=12H39M1.5700S, J2000 V = 20.0 +/- 0.5 IRREGULAR DEC=+12D12'18.02" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 2 BLUECAND2 GALAXY, AMORPHOUS RA=12H44M27.5400S, J2000 V = 20.0 +/- 0.5 IRREGULAR DEC=+12D37'5.67" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 4 BLUECAND3 GALAXY, AMORPHOUS RA=12H46M42.4500S, J2000 V = 20.0 +/- 0.5 IRREGULAR DEC=+10D22'7.60" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 5 BLUECAND4 GALAXY, AMORPHOUS RA=12H26M23.5532S, J2000 V = 20.0 +/- 0.5 IRREGULAR DEC=+14D23'24.50" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 6 BLUECAND5 GALAXY, AMORPHOUS RA=12H26M31.1300S, J2000 V = 20.0 +/- 0.5 IRREGULAR DEC=+15D10'26.70" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 15183( 7) - 05-Mar-2019 15:46:09 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.262 Line_Spacing 0.192 Coordinate_Frame POS-TARG Pattern_Orient 18.39 Angle_Between_Sides 68.14 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 15183( 7) - 05-Mar-2019 15:46:09 - [ 5] Visit: 01 (Bluecand1_visit) Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 BLUECAND1 ACS/WFC ACCUM WFC1 F606W 1 520 S PATTERN 2 1 see below (2120 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 BLUECAND1 ACS/WFC ACCUM WFC1 F814W 1 520 S PATTERN 2 2 see below (2180 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ BLUECAND1 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 530.0 S BLUECAND1 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 530.0 S BLUECAND1 1 ACS/WFC ACCUM WFC1 F606W 3 none none none 1 530.0 S BLUECAND1 1 ACS/WFC ACCUM WFC1 F606W 4 none none none 1 530.0 S BLUECAND1 2 ACS/WFC ACCUM WFC1 F814W 1 none none none 2 545.0 S BLUECAND1 2 ACS/WFC ACCUM WFC1 F814W 2 none none none 2 545.0 S BLUECAND1 2 ACS/WFC ACCUM WFC1 F814W 3 none none none 2 545.0 S BLUECAND1 2 ACS/WFC ACCUM WFC1 F814W 4 none none none 2 545.0 S 15183( 7) - 05-Mar-2019 15:46:09 - [ 6] Visit: 02 (Bluecand2_visit) Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 BLUECAND2 ACS/WFC ACCUM WFC1 F606W 1 520 S PATTERN 2 1 see below (2120 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 BLUECAND2 ACS/WFC ACCUM WFC1 F814W 1 520 S PATTERN 2 2 see below (2180 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ BLUECAND2 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 530.0 S BLUECAND2 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 530.0 S BLUECAND2 1 ACS/WFC ACCUM WFC1 F606W 3 none none none 1 530.0 S BLUECAND2 1 ACS/WFC ACCUM WFC1 F606W 4 none none none 1 530.0 S BLUECAND2 2 ACS/WFC ACCUM WFC1 F814W 1 none none none 2 545.0 S BLUECAND2 2 ACS/WFC ACCUM WFC1 F814W 2 none none none 2 545.0 S BLUECAND2 2 ACS/WFC ACCUM WFC1 F814W 3 none none none 2 545.0 S BLUECAND2 2 ACS/WFC ACCUM WFC1 F814W 4 none none none 2 545.0 S 15183( 7) - 05-Mar-2019 15:46:09 - [ 7] Visit: 03 (Bluecand3_visit) Visit Requirements: ORIENT 55.8D TO 100.0 D; ORIENT 232.0D TO 274. D On Hold Comments: Additional Comments: We have added relatively loose ORIENT constraints on this visit in order to simultaneously image a nearby Virgo dwarf galaxy that may be interacting with our blue blob. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 BLUECAND3 ACS/WFC ACCUM WFC1 F606W 1 520 S PATTERN 2 1 see below (2120 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 BLUECAND3 ACS/WFC ACCUM WFC1 F814W 1 520 S PATTERN 2 2 see below (2180 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ BLUECAND3 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 530.0 S BLUECAND3 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 530.0 S BLUECAND3 1 ACS/WFC ACCUM WFC1 F606W 3 none none none 1 530.0 S BLUECAND3 1 ACS/WFC ACCUM WFC1 F606W 4 none none none 1 530.0 S BLUECAND3 2 ACS/WFC ACCUM WFC1 F814W 1 none none none 2 545.0 S BLUECAND3 2 ACS/WFC ACCUM WFC1 F814W 2 none none none 2 545.0 S BLUECAND3 2 ACS/WFC ACCUM WFC1 F814W 3 none none none 2 545.0 S BLUECAND3 2 ACS/WFC ACCUM WFC1 F814W 4 none none none 2 545.0 S 15183( 7) - 05-Mar-2019 15:46:09 - [ 8] Visit: 04 (Bluecand4_visit) Visit Requirements: ORIENT 355D TO 50 D; ORIENT 170D TO 230 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 BLUECAND4 ACS/WFC ACCUM WFC1 F606W 1 500 S PATTERN 2 1 (2000 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 BLUECAND4 ACS/WFC ACCUM WFC1 F814W 1 500 S PATTERN 2 2 (2000 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ BLUECAND4 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 N/A BLUECAND4 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 N/A BLUECAND4 1 ACS/WFC ACCUM WFC1 F606W 3 none none none 1 N/A BLUECAND4 1 ACS/WFC ACCUM WFC1 F606W 4 none none none 1 N/A BLUECAND4 2 ACS/WFC ACCUM WFC1 F814W 1 none none none 2 N/A BLUECAND4 2 ACS/WFC ACCUM WFC1 F814W 2 none none none 2 N/A BLUECAND4 2 ACS/WFC ACCUM WFC1 F814W 3 none none none 2 N/A BLUECAND4 2 ACS/WFC ACCUM WFC1 F814W 4 none none none 2 N/A 15183( 7) - 05-Mar-2019 15:46:09 - [ 9] Visit: 05 (Bluecand5_visit) Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 BLUECAND5 ACS/WFC ACCUM WFC1 F606W 1 520 S PATTERN 2 1 see below (2128 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 BLUECAND5 ACS/WFC ACCUM WFC1 F814W 1 520 S PATTERN 2 2 see below (2184 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ BLUECAND5 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 532.0 S BLUECAND5 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 532.0 S BLUECAND5 1 ACS/WFC ACCUM WFC1 F606W 3 none none none 1 532.0 S BLUECAND5 1 ACS/WFC ACCUM WFC1 F606W 4 none none none 1 532.0 S BLUECAND5 2 ACS/WFC ACCUM WFC1 F814W 1 none none none 2 546.0 S BLUECAND5 2 ACS/WFC ACCUM WFC1 F814W 2 none none none 2 546.0 S BLUECAND5 2 ACS/WFC ACCUM WFC1 F814W 3 none none none 2 546.0 S BLUECAND5 2 ACS/WFC ACCUM WFC1 F814W 4 none none none 2 546.0 S 15183( 7) - 05-Mar-2019 15:46:09 - [ 10] Visit: 54 (Bluecand4_visit) Visit Requirements: ORIENT 355D TO 50 D; ORIENT 170D TO 230 D On Hold Comments: Additional Comments: Repeat of Visit 04 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 BLUECAND4 ACS/WFC ACCUM WFC1 F606W 1 500 S PATTERN 2 1 (2000 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 BLUECAND4 ACS/WFC ACCUM WFC1 F814W 1 500 S PATTERN 2 2 (2000 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ BLUECAND4 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 N/A BLUECAND4 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 N/A BLUECAND4 1 ACS/WFC ACCUM WFC1 F606W 3 none none none 1 N/A BLUECAND4 1 ACS/WFC ACCUM WFC1 F606W 4 none none none 1 N/A BLUECAND4 2 ACS/WFC ACCUM WFC1 F814W 1 none none none 2 N/A BLUECAND4 2 ACS/WFC ACCUM WFC1 F814W 2 none none none 2 N/A BLUECAND4 2 ACS/WFC ACCUM WFC1 F814W 3 none none none 2 N/A BLUECAND4 2 ACS/WFC ACCUM WFC1 F814W 4 none none none 2 N/A 15183( 7) - 05-Mar-2019 15:46:09 - [ 11] Summary Form for Proposal 15183 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 170D TO 230 D, ORIENT 232.0D TO 274. D, ORIENT 355D TO 50 D, ORIENT 55.8D TO 100.0 D, PATTERN 2 1, PATTERN 2 2 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names BLUECAND1, BLUECAND2, BLUECAND3, BLUECAND4, BLUECAND5 ------------------------------------------------------------------------------------------------------------------------------------