14093( 3) - 09-Sep-2015 18:10:32 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14093 Version: 3 Check-in Time: 09-Sep-2015 18:10:32 STScI Edit Number: 1 Title Stellar Populations and Physical Conditions at ~100 pc Resolution in a Lensed Galaxy at z ~ 4 ------------------------------------------------------------------------------------ Type Cycle GO 23 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Danielle Berg University of Wisconsin - Milwaukee Y CoI: Prof. Dawn K. Erb University of Wisconsin - Milwaukee N CoI: Prof. Max Pettini University of Cambridge N CoI: Dr. Matthew Auger University of Cambridge N ------------------------------------------------------------------------------------ Abstract Large surveys of star-forming galaxies at high redshift (z > 1.5) have provided us with a broad understanding of how galaxies assemble and evolve, but the spatial and spectral limitations inherent in observing faint, distant objects mean that many of the physical processes regulating this dynamic evolution are poorly constrained. Much of our most detailed knowledge of the physical conditions in distant galaxies comes from careful studies of gravitationally lensed sources, few of which are at z>3.5. FOR J0332-3557 is a gravitationally lensed galaxy at z ~ 4 for which we and other groups have obtained a total of 37.3 hours of VLT spectroscopy. The rest-frame UV spectrum is notable for its unusual combination of both strong emission lines in the rest-frame UV and strong Lya and interstellar absorption, and for the unusual spatial variation seen in the nebular emission lines, which are less extended than the underlying stellar continuum. We propose high spatial resolution imaging of FOR J0332-3557 with four broadband filters on WFC3, taking advantage of both the HST resolution and the lensing magnification to study star formation and extinction on ~100 pc scales. Because the interpretation of our unusual rest-frame UV and optical spectra requires an accurate reddening estimate, combining these observations with ground-based spectroscopy will give the most complete picture to date of chemical evolution in a distant galaxy. ------------------------------------------------------------------------------------ Observations Description ------------------------ The observational goal of our program is to use the Wide Field Camera 3 to obtain unprecedented high spatial resolution multi-wavelength imaging of the strongly-lensed star-forming galaxy, FOR J0332-3557, at redshift z ~ 4. In order to reliably model the wavelength dependence of spatial variations of FOR J0332-3557 we will obtain high resolution WFC3/F160W, F125W, F814W, and F606W imaging, tracing the rest-frame SED at 3228 AA, 2610 AA, 1740 AA, and 1238 AA respectively. This combination of filters samples the rest-frame SED at the ideal wavelengths to constrain the UV slope, and subsequently, the dust extinction, model the stellar populations, and constrain the current SED-derived SFR. FOR J0332-3557 will be observed in four filters over 2 orbits. Each filter will be observed in three sub exposures using the standard WFC3 3PT line dithers in order to fill the chip gap and remove cosmic rays, bad pixels, and other 14093( 3) - 09-Sep-2015 18:10:32 - [ 2] artifacts. In the first orbit we observe FOR J0332-3557 in the F125W and F160W filters in the IR configuration. For each subexposure, we select (NSAMP=) 9 and 10 nondestructuve readouts of the SAMP-SEQ=SPARS50 sequence respectively for the F125W and F160W filters. We select the maximum number of readouts possible that fit with in the orbit visibility in order to drive down the read noise. We choose to designate the extra readout to the F160W filter in which our target has lower S/N. This combination of readout parameters results in 3 exposures of 403 seconds for F125W, or a total exposure time of 1209 seconds, and 3 exposures of 453 seconds for F160W, or a total exposure time of 1359 seconds. In the second orbit we observe FOR J0332-3557 in the F606W and F814W filters in the UVIS configuration. Each subexposure in the F606W filter is 360 seconds, for a total exposure of 1080 seconds. The WFC3 ETC predicts a stronger S/N for F606W over the F814W filter for our target. In order to ensure strong signal in the F814W filter, each subexposure is 390 seconds, for a total exposure of 1170 seconds. To mitigate CTE losses, we utilize a post-flash of 3e (FLASH=3) with the F814W filter. ------------------------------------------------------------------------------------ 14093( 3) - 09-Sep-2015 18:10:32 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 FOR-J0332-35 GALAXY, GRAVITATIONAL RA=03H32M59.9400S, J2000 Z = R_c=22.6 57 LENS, HIGH REDSHIFT DEC=-35D57'51.70" 3.773 GALAXY Reference Frame: Other: NED Extended: YES Comments: This object was generated by the targetselector and retrieved from the NED database. ------------------------------------------------------------------------------------------------------------------------------------ 14093( 3) - 09-Sep-2015 18:10:32 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-IR-DITHER-LINE-3PT Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.605 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 41.788 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 ------------------------------------------------------------------------------------------------------------------------------------ 14093( 3) - 09-Sep-2015 18:10:32 - [ 5] Visit: 01 Visit Requirements: PCS MODE FINE 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 FOR-J0332-3 WFC3/IR MULTIAC IR F160W SAMP-SEQ=SPARS50, NSAMP=10 1 DEF GS ACQ SCENARIO BASE1B3; 557 CUM (1358.809 PATTERN 1 1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 FOR-J0332-3 WFC3/IR MULTIAC IR F125W NSAMP=9, SAMP-SEQ=SPARS50 1 DEF PATTERN 1 2 557 CUM (1208.808 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 | ------------------------------------------------------------------------------------------------------------------------------------ FOR-J0332-3557 1 WFC3/IR MULTIAC IR F160W 1 none none none 1 N/A CUM FOR-J0332-3557 1 WFC3/IR MULTIAC IR F160W 2 none none none 1 N/A CUM FOR-J0332-3557 1 WFC3/IR MULTIAC IR F160W 3 none none none 1 N/A CUM FOR-J0332-3557 2 WFC3/IR MULTIAC IR F125W 1 none none none 1 N/A CUM FOR-J0332-3557 2 WFC3/IR MULTIAC IR F125W 2 none none none 1 N/A CUM FOR-J0332-3557 2 WFC3/IR MULTIAC IR F125W 3 none none none 1 N/A CUM 14093( 3) - 09-Sep-2015 18:10:32 - [ 6] Visit: 02 Visit Requirements: PCS MODE FINE 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 FOR-J0332-3 WFC3/UVI ACCUM UVIS F606W 1 360 S GS ACQ SCENARIO BASE1B3; 557 S (1080 S) PATTERN 2 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 FOR-J0332-3 WFC3/UVI ACCUM UVIS F814W FLASH=3 1 390 S PATTERN 2 2 557 S (1170 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 | ------------------------------------------------------------------------------------------------------------------------------------ FOR-J0332-3557 1 WFC3/UVI ACCUM UVIS F606W 1 none none none 1 N/A S FOR-J0332-3557 1 WFC3/UVI ACCUM UVIS F606W 2 none none none 1 N/A S FOR-J0332-3557 1 WFC3/UVI ACCUM UVIS F606W 3 none none none 1 N/A S FOR-J0332-3557 2 WFC3/UVI ACCUM UVIS F814W 1 none none none 1 N/A S FOR-J0332-3557 2 WFC3/UVI ACCUM UVIS F814W 2 none none none 1 N/A S FOR-J0332-3557 2 WFC3/UVI ACCUM UVIS F814W 3 none none none 1 N/A S 14093( 3) - 09-Sep-2015 18:10:32 - [ 7] Summary Form for Proposal 14093 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR, UVIS ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/IR, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=3, NSAMP=10, NSAMP=9, SAMP-SEQ=SPARS50 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GS ACQ SCENARIO BASE1B3, PATTERN 1 1, PATTERN 1 2, PATTERN 2 1, PATTERN 2 2, PCS MODE FINE ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F125W, F160W, F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names FOR-J0332-3557 ------------------------------------------------------------------------------------------------------------------------------------