12487( 2) - 11-Jul-2011 13:57:33 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 12487 Version: 2 Check-in Time: 11-Jul-2011 13:57:33 STScI Edit Number: 0 Title Probing Population III Star Formation in a z=7 Galaxy ------------------------------------------------------------------------------------ Type Cycle GO 19 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Xiaohui Fan University of Arizona CoI: Mr. Zheng Cai University of Arizona N CoI: Prof. Ann Zabludoff University of Arizona N CoI: Dr. Yujin Yang Max-Planck-Institut fur Astronomie, N Heidelberg CoI: Dr. Romeel Dave University of Arizona N CoI: Dr. Siang Peng Oh University of California - Santa Barbara N CoI: Dr. Linhua Jiang Arizona State University N ------------------------------------------------------------------------------------ Abstract We propose to carry out deep WFC-3/F132N narrow-band imaging of the galaxy BDF-521 (z = 7.008+/-0.002) to measure the strength of He II 1640 emission line in this young galaxy at the end of reionization epoch. He II 1640 emission, if detected, will provide the first direct evidence of massive Population III (metal free) star formation in the early Universe. In a pilot program in Cycle-17, we obtained narrow-band imaging centered on HeII for the galaxy IOK-1 at z=6.96, and found the He II flux to be 1.2+/-1.0 x 10^-18 ergs s^-1 cm^-2, corresponding to a 1-sigma upper limit of 2 M_sun/yr in Pop-III star formation rate (SFR) assuming a top-heavy IMF. This sensitivity is 2.5x deeper than for the best previous ground-based measurement, and illustrates the power of HST narrow-band imaging in probing the earliest star formation. In this cycle, we will continue this effort by targeting galaxy BDF-521 at z=7.01 using F132N which covers the HeII emission at the galaxy redshift. The ground based photometry implies that BDF-521 has an extremely blue continuum slope with f_lambda ~ lambda^-4, the bluest among all confirmed galaxies at z>6, suggestive of either extremely low metallicity and/or a complete lack of dust. Therefore, BDF-521 is the most promising candidate for Pop-III detection. This new HST observations will be able to detect or place the most stringent upper limit of 0.6 M_sun/yr on the Pop-III SFR (1 sigma). We will also use short F125W and F160W broad-band observations to measure the rest-frame UV flux of BDF-521 in order to estimate its overall SFR, confirm the blue UV slope, and quantify the morphology, as well as provide continuum subtraction for narrow-band imaging. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will image in three filters with WFC3/IR: (1) 11-orbit exposure in F132N. (2) 2-orbit exposure in F125W. (3). 2-orbit exposure in F160W. We will divide the program into four visits. In the first visit, we will observe: (1). Two orbits F125W. (2). Two orbits F160W. We will do the same 4-point dither sequence with ~1450sec exposures to populate the 2-orbit F125W and F160W observations. In the second and third visits, we will observe: Four 12487( 2) - 11-Jul-2011 13:57:33 - [ 2] orbits in F132N. We will carry out a 4-point dither sequence with orbit-long (~2800sec) exposures in the narrow F132N band. This will bring the images to being background-limited. In the fourth visit, we will do: three orbits in F132N. We will carry out a 3-point dither sequence with orbit-long(~2800sec) exposures in the narrow F132N band. We will do a small POS-TARG offset for the third and the fourth visits and repeat the same sequence. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 12487( 2) - 11-Jul-2011 13:57:33 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 BDF-521 GALAXY, HIGH REDSHIFT RA=22H27M46.6560S +/- 0.1", J2000 Z = Y_AB=25.86; J_AB>26.5; K_AB>26.0 GALAXY DEC=-35D07'7.68" +/- 0.1" 7.008 Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 12487( 2) - 11-Jul-2011 13:57:33 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-IR-DITHER-BOX-MIN Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.572 Line_Spacing 0.365 Coordinate_Frame POS-TARG Pattern_Orient 18.528 Angle_Between_Sides 74.653 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 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 ------------------------------------------------------------------------------------------------------------------------------------ 12487( 2) - 11-Jul-2011 13:57:33 - [ 5] Visit: 01 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 BDF-521 WFC3/IR MULTIAC IR F125W NSAMP=15, SAMP-SEQ=SPARS100 1 DEF PATTERN 1 1 CUM ------------------------------------------------------------------------------------------------------------------------------------ 2 BDF-521 WFC3/IR MULTIAC IR F160W NSAMP=15, SAMP-SEQ=SPARS100 1 DEF PATTERN 1 2 CUM ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ BDF-521 1 WFC3/IR MULTIAC IR F125W 1 none none none 1 N/A CUM BDF-521 1 WFC3/IR MULTIAC IR F125W 2 none none none 1 N/A CUM BDF-521 1 WFC3/IR MULTIAC IR F125W 3 none none none 2 N/A CUM BDF-521 1 WFC3/IR MULTIAC IR F125W 4 none none none 2 N/A CUM BDF-521 2 WFC3/IR MULTIAC IR F160W 1 none none none 3 N/A CUM BDF-521 2 WFC3/IR MULTIAC IR F160W 2 none none none 3 N/A CUM BDF-521 2 WFC3/IR MULTIAC IR F160W 3 none none none 4 N/A CUM BDF-521 2 WFC3/IR MULTIAC IR F160W 4 none none none 4 N/A CUM 12487( 2) - 11-Jul-2011 13:57:33 - [ 6] Visit: 02 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 BDF-521 WFC3/IR MULTIAC IR F132N SAMP-SEQ=SPARS200, NSAMP=15 1 DEF PATTERN 1 1 CUM ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ BDF-521 1 WFC3/IR MULTIAC IR F132N 1 none none none 1 N/A CUM BDF-521 1 WFC3/IR MULTIAC IR F132N 2 none none none 2 N/A CUM BDF-521 1 WFC3/IR MULTIAC IR F132N 3 none none none 3 N/A CUM BDF-521 1 WFC3/IR MULTIAC IR F132N 4 none none none 4 N/A CUM 12487( 2) - 11-Jul-2011 13:57:33 - [ 7] Visit: 03 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 BDF-521 WFC3/IR MULTIAC IR F132N SAMP-SEQ=SPARS200, NSAMP=15 1 DEF POS TARG 2.3374, 2.0890; CUM PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ BDF-521 1 WFC3/IR MULTIAC IR F132N 1 none none none 1 N/A CUM BDF-521 1 WFC3/IR MULTIAC IR F132N 2 none none none 2 N/A CUM BDF-521 1 WFC3/IR MULTIAC IR F132N 3 none none none 3 N/A CUM BDF-521 1 WFC3/IR MULTIAC IR F132N 4 none none none 4 N/A CUM 12487( 2) - 11-Jul-2011 13:57:33 - [ 8] Visit: 04 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 BDF-521 WFC3/IR MULTIAC IR F132N NSAMP=15, SAMP-SEQ=SPARS200 1 DEF POS TARG -2.3374, CUM 2.0890; PATTERN 2 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ BDF-521 1 WFC3/IR MULTIAC IR F132N 1 none none none 1 N/A CUM BDF-521 1 WFC3/IR MULTIAC IR F132N 2 none none none 2 N/A CUM BDF-521 1 WFC3/IR MULTIAC IR F132N 3 none none none 3 N/A CUM 12487( 2) - 11-Jul-2011 13:57:33 - [ 9] Summary Form for Proposal 12487 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/IR ------------------------------------------------------------------------------------------------------------------------------------ Opmodes MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters NSAMP=15, SAMP-SEQ=SPARS100, SAMP-SEQ=SPARS200 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1, PATTERN 1 2, PATTERN 2 1, POS TARG -2.3374, 2.0890, POS TARG 2.3374, 2.0890 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F125W, F132N, F160W ------------------------------------------------------------------------------------------------------------------------------------ Target Names BDF-521 ------------------------------------------------------------------------------------------------------------------------------------