16845( 2) - 12-Oct-2021 18:49:41 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16845 Version: 2 Check-in Time: 12-Oct-2021 18:49:41 STScI Edit Number: 0 Title A BCG in the making from wet major mergers ------------------------------------------------------------------------------------ Type Cycle GO 29 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Ming Sun University of Alabama in Huntsville Y CoI: Chong Ge University of Alabama in Huntsville N CoI: Wenhao Liu University of Alabama in Huntsville N CoI: Dr. William R. Forman Smithsonian Institution Astrophysical N Observatory CoI: Dr. Craig L. Sarazin The University of Virginia N CoI: Dr. Andrew Guillory University of Alabama in Huntsville N ------------------------------------------------------------------------------------ Abstract The brightest central galaxies (BCGs) are the largest and the most massive galaxies in the universe. Their origin is still under debate but major mergers should play a key role. While there have been several dramatic examples of local BCGs forming via dry mergers, BCGs are believed to mainly form with wet major mergers at high z and there has not been a local analog of such systems. We have searched for BCGs forming via wet major mergers in the local universe and have found a spectacular example of a trio of star forming galaxies with comparable luminosities and within 15 kpc from each other. We propose joint Chandra/HST observations to study AGN, ULXs, diffuse X-ray emission and mergers in this rare system. The results will shed light on the important early stage of BCG formation. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will observe IRAS 15205+5021 with three filters F275W, F475W and F814W in two orbits to study their central AGN, the merger signature between three central galaxies (like the tidal features) and the young stellar population. F475W and F814W observations will be done in one orbit with ACS/WFC, while the F275W observation will be done in another orbit with WFC3/UVIS. The ACS data in two high-throughput filters allow detections of faint features (e.g., individual star cluster associations, dust) and a detailed color map of the three galaxies. The F275W data will add important information on the SF in the last several 10^7 years and the F275W - F475W color is a very good age indicator. ------------------------------------------------------------------------------------ 16845( 2) - 12-Oct-2021 18:49:41 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SBS1520+503 GALAXY, INTERACTING RA=15H22M2.0700S, J2000 V = 15 GALAXY, MULTIPLE DEC=+50D10'23.45" NUCLEI, STARBURST Reference Frame: Other: SIMBAD Extended: YES Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 16845( 2) - 12-Oct-2021 18:49:41 - [ 3] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 3.034 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 85.29 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-MOS-DITH-LINE Pattern_Purpose MOSAIC Number_Of_Points 3 Point_Spacing 2.4 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 85.754 Angle_Between_Sides Center_Pattern YES ------------------------------------------------------------------------------------------------------------------------------------ 16845( 2) - 12-Oct-2021 18:49:41 - [ 4] Visit: 01 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 SBS1520+503 ACS/WFC ACCUM WFC1 F814W 1 370 S (740 PATTERN 1 1-2 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SBS1520+503 ACS/WFC ACCUM WFC1 F475W 1 716 S (1432 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 | ------------------------------------------------------------------------------------------------------------------------------------ SBS1520+503 1 ACS/WFC ACCUM WFC1 F814W 1 none none none 1 N/A SBS1520+503 1 ACS/WFC ACCUM WFC1 F814W 2 none none none 1 N/A SBS1520+503 2 ACS/WFC ACCUM WFC1 F475W 1 none none none 1 N/A SBS1520+503 2 ACS/WFC ACCUM WFC1 F475W 2 none none none 1 N/A 16845( 2) - 12-Oct-2021 18:49:41 - [ 5] Visit: 02 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 SBS1520+503 WFC3/UVI ACCUM UVIS1 F275W FLASH=20 1 888 S PATTERN 2 1 S (2664 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 | ------------------------------------------------------------------------------------------------------------------------------------ SBS1520+503 1 WFC3/UVI ACCUM UVIS1 F275W 1 none none none 1 N/A S SBS1520+503 1 WFC3/UVI ACCUM UVIS1 F275W 2 none none none 1 N/A S SBS1520+503 1 WFC3/UVI ACCUM UVIS1 F275W 3 none none none 1 N/A S 16845( 2) - 12-Oct-2021 18:49:41 - [ 6] Summary Form for Proposal 16845 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS1, WFC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=20 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1-2, PATTERN 2 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F275W, F475W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names SBS1520+503 ------------------------------------------------------------------------------------------------------------------------------------