18023( 4) - 13-Nov-2025 17:52:50 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18023 Version: 4 Check-in Time: 13-Nov-2025 17:52:50 STScI Edit Number: 1 Title Revealing the Iceberg: Mapping out the Emission Line Nebula in MS1455.0+2232 ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Michael A. McDonald Massachusetts Institute of Technology Y CoI: Michael S. Calzadilla Smithsonian Institution Astrophysical N Observatory CoI: Prof. Massimo Gaspari Universita degli Studi di Modena e Reggio N Emilia ------------------------------------------------------------------------------------ Abstract In low-redshift clusters, such as Perseus and Abell 1795, the warm (10^4K), ionized phase is of critical importance to understanding thermal instabilities in the hot intracluster gas. Maps of Halpha and [O II] have been used for decades to understand how (and how not) cooling proceeds in the intracluster medium. This intermediate-temperature gas, which we think condenses out of the hot phase in areas that are locally out of thermodynamic equilibrium, retains a kinematic imprint of the hot gas, allowing us to probe the turbulence and bulk motion of the 10^8K gas by observing the "fluttering" of cool filaments in the same way that the motion of a flag provides insights into the wind speed and direction. To date there are only a small number (~4) of clusters in which we detect cool multi-phase gas on large enough scales (>50 kpc) that it can be used to provide insights into the details of cooling/feedback physics in the intracluster medium. We have recently discovered what may be the most extreme such system, MS1455.0+2232, which has a network of cool filaments that may extend on scales of ~100kpc, a factor of ~2 larger than the archetype system: the central galaxy in the Perseus cluster. Using a conveniently-located narrow band filter on WFC3-UVIS, we propose to obtain deep narrow-band imagine centered on the [O II] emission line, to make the first deep map of cool 10^4K gas in this system. This system will immediately join a small number of ~4 other clusters with extended emission line nebulae which each have proved critical in understanding cooling, feedback, turbulence in the intracluster medium. ------------------------------------------------------------------------------------ Observations Description ------------------------ The goal of this observing program is to image the central galaxy in MS1455 in three filters: a narrow band centered on redshifted [O II]3727 (F469N), and two broad bands centered on a line-free part of the blue continuum (F390W) and red continuum (F547M). In all cases, our goal is to optimize sensitivity to low surface brightnesses and fine details. I have split the 4-orbit observation in F469N into 8 exposures, with a 2-point dither pattern during each orbit -- I am assuming that the re-acquisition is equivalent to an additional pixel-level dither and so this is really an 8-point pattern that will optimize PSF reconstruction and allow for robust cosmic ray rejection. 18023( 4) - 13-Nov-2025 17:52:50 - [ 2] I have split the broadband observations into 3 exposures each, with ~1.5 orbits per band. This leads to a 2-point pattern for each, along with an orbit for which we just take a fixed-position observation in two bands. In all cases, I have selected the FLASH level such that I do not receive warnings/errors from APT. Everything of interest is located within 0.5' of the target location, and so we can handle any orientation. ------------------------------------------------------------------------------------ 18023( 4) - 13-Nov-2025 17:52:50 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 MS1455.0+223 GALAXY, COOLING FLOW, RA=14H57M15.0826S, J2000 V = 14 2 ELLIPTICAL, EMISSION DEC=+22D20'34.61" LINE NEBULA Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 18023( 4) - 13-Nov-2025 17:52:50 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.145 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 3 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE-3PT Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.135 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 18023( 4) - 13-Nov-2025 17:52:50 - [ 5] Visit: 01 (NarrowBand12) 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 MS1455.0+22 WFC3/UVI ACCUM UVIS1 F469N CR-SPLIT=NO, FLASH=20 1 500 S GS ACQ SCENARIO ONEB1OR; 32 S see below PATTERN 2 1 (2452 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 | ------------------------------------------------------------------------------------------------------------------------------------ MS1455.0+2232 1 WFC3/UVI ACCUM UVIS1 F469N 1 none none none 1 1226.0 S S MS1455.0+2232 1 WFC3/UVI ACCUM UVIS1 F469N 2 none none none 1 1226.0 S S 18023( 4) - 13-Nov-2025 17:52:50 - [ 6] Visit: 02 (NarrowBand34) 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 MS1455.0+22 WFC3/UVI ACCUM UVIS1 F469N CR-SPLIT=NO, FLASH=20 1 500 S GS ACQ SCENARIO ONEB1OR; 32 S see below PATTERN 2 1 (2452 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 | ------------------------------------------------------------------------------------------------------------------------------------ MS1455.0+2232 1 WFC3/UVI ACCUM UVIS1 F469N 1 none none none 1 1226.0 S S MS1455.0+2232 1 WFC3/UVI ACCUM UVIS1 F469N 2 none none none 1 1226.0 S S 18023( 4) - 13-Nov-2025 17:52:50 - [ 7] Visit: 03 (NarrowBand56) 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 MS1455.0+22 WFC3/UVI ACCUM UVIS1 F469N CR-SPLIT=NO, FLASH=20 1 500 S GS ACQ SCENARIO ONEB1OR; 32 S see below PATTERN 2 1 (2452 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 | ------------------------------------------------------------------------------------------------------------------------------------ MS1455.0+2232 1 WFC3/UVI ACCUM UVIS1 F469N 1 none none none 1 1226.0 S S MS1455.0+2232 1 WFC3/UVI ACCUM UVIS1 F469N 2 none none none 1 1226.0 S S 18023( 4) - 13-Nov-2025 17:52:50 - [ 8] Visit: 04 (NarrowBand78) 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 MS1455.0+22 WFC3/UVI ACCUM UVIS1 F469N CR-SPLIT=NO, FLASH=20 1 500 S GS ACQ SCENARIO ONEB1OR; 32 S see below PATTERN 2 1 (2452 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 | ------------------------------------------------------------------------------------------------------------------------------------ MS1455.0+2232 1 WFC3/UVI ACCUM UVIS1 F469N 1 none none none 1 1226.0 S S MS1455.0+2232 1 WFC3/UVI ACCUM UVIS1 F469N 2 none none none 1 1226.0 S S 18023( 4) - 13-Nov-2025 17:52:50 - [ 9] Visit: 05 (Broadband-Blue-12) 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 MS1455.0+22 WFC3/UVI ACCUM UVIS1 F547M CR-SPLIT=NO, FLASH=8 1 500 S GS ACQ SCENARIO ONEB1OR; 32 S see below PATTERN 3 1 (2322 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 | ------------------------------------------------------------------------------------------------------------------------------------ MS1455.0+2232 1 WFC3/UVI ACCUM UVIS1 F547M 1 none none none 1 774.0 S S MS1455.0+2232 1 WFC3/UVI ACCUM UVIS1 F547M 2 none none none 1 774.0 S S MS1455.0+2232 1 WFC3/UVI ACCUM UVIS1 F547M 3 none none none 1 774.0 S S 18023( 4) - 13-Nov-2025 17:52:50 - [ 10] Visit: 06 (Broadband-Red-23) 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 MS1455.0+22 WFC3/UVI ACCUM UVIS1 F390W CR-SPLIT=NO, FLASH=10 1 500 S GS ACQ SCENARIO ONEB1OR; 32 S see below PATTERN 3 1 (2319 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 | ------------------------------------------------------------------------------------------------------------------------------------ MS1455.0+2232 1 WFC3/UVI ACCUM UVIS1 F390W 1 none none none 1 773.0 S S MS1455.0+2232 1 WFC3/UVI ACCUM UVIS1 F390W 2 none none none 1 773.0 S S MS1455.0+2232 1 WFC3/UVI ACCUM UVIS1 F390W 3 none none none 1 773.0 S S 18023( 4) - 13-Nov-2025 17:52:50 - [ 11] Visit: 07 (Broadband-Blue3-Red1) 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 MS1455.0+22 WFC3/UVI ACCUM UVIS1 F547M CR-SPLIT=NO, FLASH=8 1 100 S GS ACQ SCENARIO ONEB1OR 32 S see below (765 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 MS1455.0+22 WFC3/UVI ACCUM UVIS1 F547M CR-SPLIT=NO, FLASH=8 1 100 S POS TARG 0.135, null 32 S see below (765 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 MS1455.0+22 WFC3/UVI ACCUM UVIS1 F390W CR-SPLIT=NO, FLASH=15 1 100 S 32 S see below (765 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 | ------------------------------------------------------------------------------------------------------------------------------------ MS1455.0+2232 1 WFC3/UVI ACCUM UVIS1 F547M none none none none 1 765.0 S S MS1455.0+2232 2 WFC3/UVI ACCUM UVIS1 F547M none none none none 1 765.0 S S MS1455.0+2232 3 WFC3/UVI ACCUM UVIS1 F390W none none none none 1 765.0 S S 18023( 4) - 13-Nov-2025 17:52:50 - [ 12] Summary Form for Proposal 18023 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO, FLASH=10, FLASH=15, FLASH=20, FLASH=8 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GS ACQ SCENARIO ONEB1OR, PATTERN 2 1, PATTERN 3 1, POS TARG 0.135, null ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F390W, F469N, F547M ------------------------------------------------------------------------------------------------------------------------------------ Target Names MS1455.0+2232 ------------------------------------------------------------------------------------------------------------------------------------