18209( 3) - 22-Oct-2025 19:09:38 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18209 Version: 3 Check-in Time: 22-Oct-2025 19:09:38 STScI Edit Number: 0 Title Narrowband observations of protostellar outflows in M20 ------------------------------------------------------------------------------------ Type Cycle GO/DD 32 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Christopher Britt Space Telescope Science Institute Y CoI: Max Mutchler Space Telescope Science Institute Y CoI: John Maple Space Telescope Science Institute Y CoI: Joseph DePasquale Space Telescope Science Institute N CoI: Alyssa Pagan Space Telescope Science Institute N CoI: Varun Bajaj Space Telescope Science Institute Y CoI: Christine Pulliam Space Telescope Science Institute N CoI: Ray Villard Space Telescope Science Institute N CoI: Miranda Brugman Space Telescope Science Institute N ------------------------------------------------------------------------------------ Abstract We propose to image dense pillars within the star forming nebula, M20. Imaging in F502N, F656N, and F673N will identify variations of density and ionization in the atomic gas surrounding this active area of star formation and highlight protostellar outflows emerging from the pillar, the proper motion of which will be measured in comparison to archival observations of the region. Broadband imaging in F475W and F814W will enable accurate measurement of stellar colors in the field. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will obtain high signal-to-noise imaging of the M20 "Snail" (HH 399) in narrowband filters F502N, F656N, and F673N, as well as broadband filters F475W and F814W. The B and I filters will provide a balanced color profile to the stars in the image, while the [O III], H-alpha, and [SII] narrowband filters will highlight regions of differing density and ionization state through the nebula. Additionally, the F656N filter will enable a direct comparison to archival WFPC2 H-alpha images in order to highlight the proper motion of the jet. We propose a single WFC3 pointing which will adequately cover the entire object at the Position Angles available in Reduced Gyro Mode. We will employ a dither pattern which fills the chip gaps and enables cosmic ray rejection. We calculate exposure times from archival observations of this object with WFPC2. Using the WFC3 ETC, we estimate that we can achieve the high signal-to-noise needed for imaging with 6 orbits, with approximately 5 ks for F656N, 6 ks for F502N, and 7 ks for F673N. The broadband filter exposures can be placed as short bookends to the narrowband observations. Proper motion was measurable as early as 5 years after the initial observations in 1997 taken under HST program ID 6857 (PI Trauger), in data taken in 2002 under HST program ID 11121 (PI Yusef-Zadeh) (Yusef-Zadeh, Biretta, & Wardle, 2005). ------------------------------------------------------------------------------------ 18209( 3) - 22-Oct-2025 19:09:38 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HH-399 ISM, HERBIG-HARO OBJECT RA=18H02M28.5950S, J2000 V = 18 +/- 6 DEC=-23D04'26.07" Reference Frame: ICRS Extended: YES Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. 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 ------------------------------------------------------------------------------------------------------------------------------------ 18209( 3) - 22-Oct-2025 19:09:38 - [ 3] Visit: 11 (M20 snail) Visit Requirements: ORIENT 265D TO 275 D; BEFORE 16-MAR-2026:00:00:00 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 HH-399 WFC3/UVI ACCUM UVIS-CENT F475W FLASH=15 1 90 S (90 POS TARG -0.2, -3.0; PAR S ER S) 5 WITH 1-4 ------------------------------------------------------------------------------------------------------------------------------------ 2 HH-399 WFC3/UVI ACCUM UVIS-CENT F502N FLASH=20 1 600 S (600 POS TARG -0.2, -3.0 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HH-399 WFC3/UVI ACCUM UVIS-CENT F656N FLASH=20 1 500 S (500 POS TARG -0.2, -3.0 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HH-399 WFC3/UVI ACCUM UVIS-CENT F673N FLASH=20 1 800 S (800 POS TARG -0.2, -3.0 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 5 ANY ACS/WFC ACCUM WFCENTER F658N 2 1080 S (2160 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 | ------------------------------------------------------------------------------------------------------------------------------------ HH-399 1 WFC3/UVI ACCUM UVIS-CEN F475W none none none none 1 N/A S TER HH-399 2 WFC3/UVI ACCUM UVIS-CEN F502N none none none none 1 N/A S TER HH-399 3 WFC3/UVI ACCUM UVIS-CEN F656N none none none none 1 N/A S TER HH-399 4 WFC3/UVI ACCUM UVIS-CEN F673N none none none none 1 N/A S TER ANY 5 ACS/WFC ACCUM WFCENTER F658N none none 1 none 1 N/A ANY 5 ACS/WFC ACCUM WFCENTER F658N none none 2 none 1 N/A 18209( 3) - 22-Oct-2025 19:09:38 - [ 4] Visit: 12 (M20 snail) Visit Requirements: SAME ORIENT AS 11; BEFORE 16-MAR-2026:00:00:00 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 HH-399 WFC3/UVI ACCUM UVIS-CENT F814W FLASH=15 1 90 S (90 POS TARG -0.2, -3.0; PAR S ER S) 5 WITH 1-4 ------------------------------------------------------------------------------------------------------------------------------------ 2 HH-399 WFC3/UVI ACCUM UVIS-CENT F502N FLASH=20 1 600 S (600 POS TARG -0.2, -3.0 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HH-399 WFC3/UVI ACCUM UVIS-CENT F656N FLASH=20 1 500 S (500 POS TARG -0.2, -3.0 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HH-399 WFC3/UVI ACCUM UVIS-CENT F673N FLASH=20 1 800 S (800 POS TARG -0.2, -3.0 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 5 ANY ACS/WFC ACCUM WFCENTER F658N 2 1080 S (2160 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 | ------------------------------------------------------------------------------------------------------------------------------------ HH-399 1 WFC3/UVI ACCUM UVIS-CEN F814W none none none none 1 N/A S TER HH-399 2 WFC3/UVI ACCUM UVIS-CEN F502N none none none none 1 N/A S TER HH-399 3 WFC3/UVI ACCUM UVIS-CEN F656N none none none none 1 N/A S TER HH-399 4 WFC3/UVI ACCUM UVIS-CEN F673N none none none none 1 N/A S TER ANY 5 ACS/WFC ACCUM WFCENTER F658N none none 1 none 1 N/A ANY 5 ACS/WFC ACCUM WFCENTER F658N none none 2 none 1 N/A 18209( 3) - 22-Oct-2025 19:09:38 - [ 5] Visit: 13 (M20 snail) Visit Requirements: SAME ORIENT AS 11; BEFORE 16-MAR-2026:00:00:00 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 HH-399 WFC3/UVI ACCUM UVIS-CENT F475W FLASH=15 1 90 S (90 PAR 5 WITH 1-4 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 2 HH-399 WFC3/UVI ACCUM UVIS-CENT F502N FLASH=20 1 600 S (600 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HH-399 WFC3/UVI ACCUM UVIS-CENT F656N FLASH=20 1 500 S (500 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HH-399 WFC3/UVI ACCUM UVIS-CENT F673N FLASH=20 1 800 S (800 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 5 ANY ACS/WFC ACCUM WFCENTER F658N 2 1080 S (2160 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 | ------------------------------------------------------------------------------------------------------------------------------------ HH-399 1 WFC3/UVI ACCUM UVIS-CEN F475W none none none none 1 N/A S TER HH-399 2 WFC3/UVI ACCUM UVIS-CEN F502N none none none none 1 N/A S TER HH-399 3 WFC3/UVI ACCUM UVIS-CEN F656N none none none none 1 N/A S TER HH-399 4 WFC3/UVI ACCUM UVIS-CEN F673N none none none none 1 N/A S TER ANY 5 ACS/WFC ACCUM WFCENTER F658N none none 1 none 1 N/A ANY 5 ACS/WFC ACCUM WFCENTER F658N none none 2 none 1 N/A 18209( 3) - 22-Oct-2025 19:09:38 - [ 6] Visit: 14 (M20 snail) Visit Requirements: SAME ORIENT AS 11; BEFORE 16-MAR-2026:00:00:00 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 HH-399 WFC3/UVI ACCUM UVIS-CENT F814W FLASH=15 1 90 S (90 PAR 5 WITH 1-4 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 2 HH-399 WFC3/UVI ACCUM UVIS-CENT F502N FLASH=20 1 600 S (600 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HH-399 WFC3/UVI ACCUM UVIS-CENT F656N FLASH=20 1 500 S (500 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HH-399 WFC3/UVI ACCUM UVIS-CENT F673N FLASH=20 1 800 S (800 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 5 ANY ACS/WFC ACCUM WFCENTER F658N 2 1080 S (2160 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 | ------------------------------------------------------------------------------------------------------------------------------------ HH-399 1 WFC3/UVI ACCUM UVIS-CEN F814W none none none none 1 N/A S TER HH-399 2 WFC3/UVI ACCUM UVIS-CEN F502N none none none none 1 N/A S TER HH-399 3 WFC3/UVI ACCUM UVIS-CEN F656N none none none none 1 N/A S TER HH-399 4 WFC3/UVI ACCUM UVIS-CEN F673N none none none none 1 N/A S TER ANY 5 ACS/WFC ACCUM WFCENTER F658N none none 1 none 1 N/A ANY 5 ACS/WFC ACCUM WFCENTER F658N none none 2 none 1 N/A 18209( 3) - 22-Oct-2025 19:09:38 - [ 7] Visit: 15 (M20 snail) Visit Requirements: SAME ORIENT AS 11; BEFORE 16-MAR-2026:00:00:00 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 HH-399 WFC3/UVI ACCUM UVIS-CENT F475W FLASH=15 1 90 S (90 POS TARG 0.2, 3.0; PAR 5 S ER S) WITH 1-4 ------------------------------------------------------------------------------------------------------------------------------------ 2 HH-399 WFC3/UVI ACCUM UVIS-CENT F502N FLASH=20 1 600 S (600 POS TARG 0.2, 3.0 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HH-399 WFC3/UVI ACCUM UVIS-CENT F656N FLASH=20 1 500 S (500 POS TARG 0.2, 3.0 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HH-399 WFC3/UVI ACCUM UVIS-CENT F673N FLASH=20 1 800 S (800 POS TARG 0.2, 3.0 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 5 ANY ACS/WFC ACCUM WFCENTER F658N 2 1080 S (2160 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 | ------------------------------------------------------------------------------------------------------------------------------------ HH-399 1 WFC3/UVI ACCUM UVIS-CEN F475W none none none none 1 N/A S TER HH-399 2 WFC3/UVI ACCUM UVIS-CEN F502N none none none none 1 N/A S TER HH-399 3 WFC3/UVI ACCUM UVIS-CEN F656N none none none none 1 N/A S TER HH-399 4 WFC3/UVI ACCUM UVIS-CEN F673N none none none none 1 N/A S TER ANY 5 ACS/WFC ACCUM WFCENTER F658N none none 1 none 1 N/A ANY 5 ACS/WFC ACCUM WFCENTER F658N none none 2 none 1 N/A 18209( 3) - 22-Oct-2025 19:09:38 - [ 8] Visit: 16 (M20 snail) Visit Requirements: SAME ORIENT AS 11; BEFORE 16-MAR-2026:00:00:00 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 HH-399 WFC3/UVI ACCUM UVIS-CENT F475W FLASH=15 1 90 S (90 POS TARG 0.2, 3.0; PAR 5 S ER S) WITH 1-4 ------------------------------------------------------------------------------------------------------------------------------------ 2 HH-399 WFC3/UVI ACCUM UVIS-CENT F502N FLASH=20 1 600 S (600 POS TARG 0.2, 3.0 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HH-399 WFC3/UVI ACCUM UVIS-CENT F656N FLASH=20 1 500 S (500 POS TARG 0.2, 3.0 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HH-399 WFC3/UVI ACCUM UVIS-CENT F673N FLASH=20 1 800 S (800 POS TARG 0.2, 3.0 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 5 ANY ACS/WFC ACCUM WFCENTER F658N 2 1080 S (2160 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 | ------------------------------------------------------------------------------------------------------------------------------------ HH-399 1 WFC3/UVI ACCUM UVIS-CEN F475W none none none none 1 N/A S TER HH-399 2 WFC3/UVI ACCUM UVIS-CEN F502N none none none none 1 N/A S TER HH-399 3 WFC3/UVI ACCUM UVIS-CEN F656N none none none none 1 N/A S TER HH-399 4 WFC3/UVI ACCUM UVIS-CEN F673N none none none none 1 N/A S TER ANY 5 ACS/WFC ACCUM WFCENTER F658N none none 1 none 1 N/A ANY 5 ACS/WFC ACCUM WFCENTER F658N none none 2 none 1 N/A 18209( 3) - 22-Oct-2025 19:09:38 - [ 9] Summary Form for Proposal 18209 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS-CENTER, WFCENTER ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=15, FLASH=20 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BEFORE 16-MAR-2026:00:00:00, ORIENT 265D TO 275 D, PAR 5 WITH 1-4, POS TARG -0.2, -3.0, POS TARG 0.2, 3.0, SAME ORIENT AS 11 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F475W, F502N, F656N, F658N, F673N, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names ANY, HH-399 ------------------------------------------------------------------------------------------------------------------------------------