15106( 4) - 12-Dec-2018 16:27:10 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15106 Version: 4 Check-in Time: 12-Dec-2018 16:27:10 STScI Edit Number: 2 Title The UV attenuation in JWST target VV 191 ------------------------------------------------------------------------------------ Type Cycle GO 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Benne Willem Holwerda University of Louisville Research Y Foundation, Inc. CoI: Dr. William Clifford Keel University of Alabama N CoI: Dr. Rolf A. Jansen Arizona State University N CoI: Prof. Rogier A. Windhorst Arizona State University N ------------------------------------------------------------------------------------ Abstract We aim to map the UV--near--IR attenuation curve along many sightlines within nearby disk galaxies to resolve a large fundamental uncertainty in galaxy evolution studies: the variance in the attenuation curve within an indivual galaxy disk on linear scales <50pc, and the prevalence of the 2175 Angstrom "bump" specifically. We developed a technique to obtain spatially-resolved attenuation measurements using overlapping ("occulting") galaxy pairs. The GalaxyZoo citizen science project and our STARSMOG HST/ACS F606W snapshot survey have only recently identified and validated overlapping pairs with a geometry that lends itself particularly well for such analysis. The most promising pair, VV 191, will be observed as JWST/NIRCam GTO targets to cover the near-IR part of the attenuation curves. To complement the JWST NIR observations with UV, we request WFC3/UVIS observations in the F225W and F336W filters. These cover (together with the existing F606W ACS images) the UV--visible portion of the UV--near-IR attenuation curves for each <50pc resolution element in the region of overlap in the non-interacting galaxy pair VV191 (MCG+04-33-005), in which a relatively blue elliptical beautifully backlights the outer disk of a foreground face-on spiral galaxy. Dither strategy: We opt for a 2-point dither in the case of the F336W observations (1 orbit) and a 3pt dither strategy for the F225W observations. The 9 orbits for the F225W observations are broken into three groupings of 3 orbits in the 3 dither pattern. This is to ensure correction of cosmics and detector artifacts. Our secondary aim is an HST/JWST image with good public outreach potential and our aim is to maximize image quality for this reason as well. ------------------------------------------------------------------------------------ Observations Description ------------------------ HST/WFC3 Observations 15106( 4) - 12-Dec-2018 16:27:10 - [ 2] We ask for HST/WFC3 UVIS observations for ten orbits, distributed over the F225W and F336W filters to ensure coverage of the attenuation "bump" observed by Calzetti & Heckman (1999). Exposures are to be dithered to remove cosmics and mitigate detector effects. Roll angle is not particularly constrained as the pair fits comfortably in the WFC3 field-of-view. The STARSMOG program already obtained F606W observations and we ask only for the UV filters. The planned JWST/NIRcam GTO observations cover the near-infrared through K-band. Filter Choices Our choice of filters reflects the need to sample the attenuation curve in the ultra-violet (see Fig. 4). The F225W maximizes leverage on the attenuation in the ultraviolet combined with excellent throughput and sensitivity for short exposures. Combined with the F336W filter, it traces the strength of the 2175 Angstrom "bump" in the attenuation curve. We will only use one side of WRC3/UVIS to ensure homogeneity among the observations and include a 10-14e- of post-flash for each exposure. With seven filters, the attenuation curve is sufficiently sampled to distinguish between the different ones observed in local galaxies, e.g., Milky Way (Cardelli et al., 1989), Magellanic Clouds (Gordon & Clayton, 1998; Misselt et al., 1999) or star-forming (Calzetti et al., 1994). Exposure time A single orbit exposure with F606W results in s/n > 7 in the outer parts of both galaxies, evident by the image in Figure 5, ensuring a wide overlap region for attenuation measurements. In the UV, the observation is more challenging because the background elliptical lower surface brightness in the UV. The central region of the elliptical has the highest surface brightness, enough for UV comparisons. To ensure enough overlap, we require a s=n 1 at the effective radius of the elliptical in both filters. Starting from our F606W image and according to the WFC3 ETC this can be achieved with 9 orbits (23000s, including post-flash) in F225W and 1 orbit (2700s) in F336W, resulting in a total of 10 orbits. The 10 orbits requested can be broken into two visits (0.5+4.5 orbits F336W+F225W). Flash Flas options for the F336W and F225W were chosen to be 10. NB: can we check 15106( 4) - 12-Dec-2018 16:27:10 - [ 3] this is enough? ------------------------------------------------------------------------------------ 15106( 4) - 12-Dec-2018 16:27:10 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 VV191 GALAXY, DUST LANE, RA=13H48M21.9168S, J2000 V = 15.5 +/- 0.4 ELLIPTICAL, SPIRAL DEC=+25D40'38.68" Reference Frame: Other: SIMBAD Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 15106( 4) - 12-Dec-2018 16:27:10 - [ 5] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 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: 2 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 ------------------------------------------------------------------------------------------------------------------------------------ 15106( 4) - 12-Dec-2018 16:27:10 - [ 6] Visit: 01 (F336W) 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 VV191 WFC3/UVI ACCUM UVIS1 F336W FLASH=10 1 1300 S PATTERN 1 1 S see below (2749 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 | ------------------------------------------------------------------------------------------------------------------------------------ VV191 1 WFC3/UVI ACCUM UVIS1 F336W 1 none none none 1 1319.0 S S VV191 1 WFC3/UVI ACCUM UVIS1 F336W 2 none none none 1 1430.0 S S 15106( 4) - 12-Dec-2018 16:27:10 - [ 7] Visit: 02 (F225W) 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 VV191 WFC3/UVI ACCUM UVIS1 F225W FLASH=5 1 1300 S PATTERN 2 1 S see below (8874 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 | ------------------------------------------------------------------------------------------------------------------------------------ VV191 1 WFC3/UVI ACCUM UVIS1 F225W 1 none none none 1 2884.0 S S VV191 1 WFC3/UVI ACCUM UVIS1 F225W 2 none none none 2 2995.0 S S VV191 1 WFC3/UVI ACCUM UVIS1 F225W 3 none none none 3 2995.0 S S 15106( 4) - 12-Dec-2018 16:27:10 - [ 8] Visit: 03 (F225W) 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 VV191 WFC3/UVI ACCUM UVIS1 F225W FLASH=5 1 2700 S PATTERN 2 1 S see below (8874 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 | ------------------------------------------------------------------------------------------------------------------------------------ VV191 1 WFC3/UVI ACCUM UVIS1 F225W 1 none none none 1 2884.0 S S VV191 1 WFC3/UVI ACCUM UVIS1 F225W 2 none none none 2 2995.0 S S VV191 1 WFC3/UVI ACCUM UVIS1 F225W 3 none none none 3 2995.0 S S 15106( 4) - 12-Dec-2018 16:27:10 - [ 9] Visit: 04 (F225W) 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 VV191 WFC3/UVI ACCUM UVIS1 F225W FLASH=5 1 2700 S PATTERN 2 1 S see below (8874 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 | ------------------------------------------------------------------------------------------------------------------------------------ VV191 1 WFC3/UVI ACCUM UVIS1 F225W 1 none none none 1 2884.0 S S VV191 1 WFC3/UVI ACCUM UVIS1 F225W 2 none none none 2 2995.0 S S VV191 1 WFC3/UVI ACCUM UVIS1 F225W 3 none none none 3 2995.0 S S 15106( 4) - 12-Dec-2018 16:27:10 - [ 10] Summary Form for Proposal 15106 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=10, FLASH=5 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1, PATTERN 2 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F225W, F336W ------------------------------------------------------------------------------------------------------------------------------------ Target Names VV191 ------------------------------------------------------------------------------------------------------------------------------------