15666( 4) - 05-Jul-2019 14:39:24 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15666 Version: 4 Check-in Time: 05-Jul-2019 14:39:24 STScI Edit Number: 0 Title Probing Infall of Cold Gas in an Interacting Galaxy ------------------------------------------------------------------------------------ Type Cycle GO 26 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Sanchayeeta Borthakur Arizona State University Y ------------------------------------------------------------------------------------ Abstract The inflow of massive amounts of gas towards the centers of galaxies is commonly seen in simulations of galaxy interactions and mergers. Such inflows are associated with strong starbursts in interacting galaxies as well as their enhanced nuclear activity. While the importance of inflow of gas is clear, there is little observational data to strengthen our understanding of the physics of gas inflow. This program aims to study a rare case where our previous D- and C- configuration VLA imaging detected blue-shifted HI 21cm emission tracing infall of atomic gas into a spiral galaxy. We request for 27.5 hours of high-resolution VLA B-configuration imaging to identify the location of the inflowing gas and to characterize its nature and origin. We also request for 3 orbits of ultraviolet spectroscopy with HST COS to establish the origin of the gas as inflow and rule out outflow with high confidence. This system is truly unique and provides unprecedented opportunity to study infall of gas into galaxies that have so far been studied only in simulations. Therefore, we believe that our modest request of 27.5 hours of the VLA and 3 orbits of the HST will yield significant scientific results. ------------------------------------------------------------------------------------ Observations Description ------------------------ The main goals of this project are to (1) confirm if there in ongoing infall of gas into the target galaxy and (2) if so, reveal the physical process responsible for it. The program aims to obtain UV spectrum with G130M. The spectrum will be analyzed to estimate outflow signatures (at 200 km/s centroid) and to verify inflow. In addition to the standard target acquisition image, we will obtain deeper NUV images with MIRRORA along with the spectroscopic observations. These images will provide important guidance for the interpretation of the spectra. The high-angular resolution of COS NUV imaging (47.1 mas/resel) is a factor of > 120 higher resolution than existing GALEX NUV imaging (where the source is unresolved). The data will be complemented by ground-based imagery and would link the connection between location of gas inflow and recent star-formation. A detailed study of the COS UV spectra and comparison of Starburst99 models will be used to predict the stellar populations (age, burst type etc.). The nature of the ISM combined with morphology of star forming region will provide vital clues about the triggering mechanism of star-formation in an interacting system. We will interpret our data and measurements in terms of results from simulations. 15666( 4) - 05-Jul-2019 14:39:24 - [ 2] We require 3 orbits to get a COS spectrum with G130M granting in the 1327 setting. The galaxy has a FUV GALEX magnitude of 18.3. Based on the u-band size in the SDSS image, we expect the UV magnitude within the COS aperture to be from 18.3 -19.0 mag. Based on that we request for 3 orbits to get a S/N of 10 at 1251A so that we can cover Lyman-alpha, Si II 1260, 1190, 1193, OI 1302 and multiple other species at a S/N ~10. The ETC IDs for these calculations are COS.sp.1178547 and COS.sp.1178545. ------------------------------------------------------------------------------------ 15666( 4) - 05-Jul-2019 14:39:24 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 J151225.15+0 GALAXY, INTERACTING RA=15H12M25.1500S +/- 0.4", J2000 Z = V = 16.55 +/- 0.1 GALEX FUV=18.3 & 12954.20 GALAXY DEC=+01D29'54.20" +/- 0.4" 0.0289 NUV=17.9 Reference Frame: ICRS Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 15666( 4) - 05-Jul-2019 14:39:24 - [ 4] Visit: 01 (Visit 01) Visit Requirements: On Hold Comments: Additional Comments: 3 orbits 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 J151225.15+ COS/NUV ACQ/SEA PSA MIRRORA CENTER=BRIGHTEST, 1 24 S (24 012954.20 RCH STEP-SIZE=1.7, SCAN-SIZE=3 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 J151225.15+ COS/NUV ACQ/IMA PSA MIRRORA 1 900 S (900 012954.20 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 3 J151225.15+ COS/FUV TIME-TA PSA G130M 1222 BUFFER-TIME=140, FP-POS=1, 1 140 S (140 012954.20 G FLASH=YES, SEGMENT=BOTH S) ------------------------------------------------------------------------------------------------------------------------------------ 4 J151225.15+ COS/FUV TIME-TA PSA G130M 1222 BUFFER-TIME=1200, FP-POS=1, 1 1310 S 012954.20 G FLASH=YES, SEGMENT=BOTH (1310 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 J151225.15+ COS/FUV TIME-TA PSA G130M 1222 BUFFER-TIME=1361, FP-POS=2, 1 1361 S 012954.20 G FLASH=YES, SEGMENT=BOTH (1361 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 J151225.15+ COS/FUV TIME-TA PSA G130M 1222 BUFFER-TIME=1230, FP-POS=3, 1 1340 S 012954.20 G FLASH=YES, SEGMENT=BOTH (1340 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 J151225.15+ COS/FUV TIME-TA PSA G130M 1222 BUFFER-TIME=1221, FP-POS=4, 1 1331 S 012954.20 G FLASH=YES, SEGMENT=BOTH (1331 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 | ------------------------------------------------------------------------------------------------------------------------------------ J151225.15+012954.2 1 COS/NUV ACQ/SEA PSA MIRRORA none none none none 1 N/A 0 RCH J151225.15+012954.2 2 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A 0 GE J151225.15+012954.2 3 COS/FUV TIME-TA PSA G130M 1222 none none none none 1 N/A 0 G J151225.15+012954.2 4 COS/FUV TIME-TA PSA G130M 1222 none none none none 2 N/A 0 G J151225.15+012954.2 5 COS/FUV TIME-TA PSA G130M 1222 none none none none 2 N/A 0 G J151225.15+012954.2 6 COS/FUV TIME-TA PSA G130M 1222 none none none none 3 N/A 0 G J151225.15+012954.2 7 COS/FUV TIME-TA PSA G130M 1222 none none none none 3 N/A 0 G 15666( 4) - 05-Jul-2019 14:39:24 - [ 5] Visit: 02 (Visit 02) Visit Requirements: On Hold Comments: Additional Comments: 2 orbits 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 J151225.15+ COS/NUV ACQ/SEA PSA MIRRORA CENTER=BRIGHTEST, 1 24 S (24 012954.20 RCH STEP-SIZE=1.7, SCAN-SIZE=3 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 J151225.15+ COS/NUV ACQ/IMA PSA MIRRORA 1 90 S (90 012954.20 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 3 J151225.15+ COS/FUV TIME-TA PSA G130M 1222 BUFFER-TIME=656, FP-POS=1, 1 766 S (766 012954.20 G FLASH=YES, SEGMENT=BOTH S) ------------------------------------------------------------------------------------------------------------------------------------ 4 J151225.15+ COS/FUV TIME-TA PSA G130M 1222 BUFFER-TIME=709, FP-POS=2, 1 819 S (819 012954.20 G FLASH=YES, SEGMENT=BOTH S) ------------------------------------------------------------------------------------------------------------------------------------ 5 J151225.15+ COS/FUV TIME-TA PSA G130M 1222 BUFFER-TIME=1230, FP-POS=3, 1 1340 S 012954.20 G FLASH=YES, SEGMENT=BOTH (1340 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 J151225.15+ COS/FUV TIME-TA PSA G130M 1222 BUFFER-TIME=1221, FP-POS=4, 1 1331 S 012954.20 G FLASH=YES, SEGMENT=BOTH (1331 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 | ------------------------------------------------------------------------------------------------------------------------------------ J151225.15+012954.2 1 COS/NUV ACQ/SEA PSA MIRRORA none none none none 1 N/A 0 RCH J151225.15+012954.2 2 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A 0 GE J151225.15+012954.2 3 COS/FUV TIME-TA PSA G130M 1222 none none none none 1 N/A 0 G J151225.15+012954.2 4 COS/FUV TIME-TA PSA G130M 1222 none none none none 1 N/A 0 G J151225.15+012954.2 5 COS/FUV TIME-TA PSA G130M 1222 none none none none 2 N/A 0 G J151225.15+012954.2 6 COS/FUV TIME-TA PSA G130M 1222 none none none none 2 N/A 0 G 15666( 4) - 05-Jul-2019 14:39:24 - [ 6] Summary Form for Proposal 15666 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/IMAGE, ACQ/SEARCH, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=1200, BUFFER-TIME=1221, BUFFER-TIME=1230, BUFFER-TIME=1361, BUFFER-TIME=140, BUFFER-TIME=656, BUFFER-TIME=709, CENTER=BRIGHTEST, FLASH=YES, FP-POS=1, FP-POS=2, FP-POS=3, FP-POS=4, SCAN-SIZE=3, SEGMENT=BOTH, STEP-SIZE=1.7 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G130M, MIRRORA ------------------------------------------------------------------------------------------------------------------------------------ Target Names J151225.15+012954.20 ------------------------------------------------------------------------------------------------------------------------------------