15931( 2) - 22-Jul-2019 16:31:20 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15931 Version: 2 Check-in Time: 22-Jul-2019 16:31:20 STScI Edit Number: 0 Title Do ultra-luminous star-forming galaxies exist at z ~ 9? ------------------------------------------------------------------------------------ Type Cycle GO 27 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Rebecca A A Bowler University of Oxford Y CoI: Prof. Matt Jarvis University of Oxford N CoI: Prof. James S. Dunlop University of Edinburgh, Institute for N Astronomy CoI: Dr. Ross McLure Royal Observatory Edinburgh N CoI: Dr. Derek McLeod Royal Observatory Edinburgh N ------------------------------------------------------------------------------------ Abstract The study of the most luminous star-forming galaxies at z > 7 has the potential to reveal key properties of reionization, as these sources likely occupy highly ionised regions within a predominantly neutral Universe. The number of bright sources however remains uncertain, due primarily to their rarity over the small area deep surveys typically used to detect them. We have expanded the search for bright z ~ 9 Lyman-break galaxies using the full 2 deg2 of deep ground-based optical/NIR photometry in the COSMOS and UDS fields, resulting in the selection of two extremely luminous galaxy candidates with best-fitting photometric redshifts at z ~ 9 and mAB < 24.5. Despite being the most robust z > 8 objects in our full SED fitting analysis, unfortunately current and future ground-based Y-band data in these two fields is insufficient to exclude the possibility that these objects are galactic brown dwarf interlopers. Due to the atmospheric transmission, the ground-based Y-bands peak too far to the blue, meaning the sharp expected Lyman-break cannot be confirmed. With a single orbit of HST/WFC3 imaging in the F105W (wide YJ) band it is possible to determine the high-redshift nature of these sources, as this filter efficiently targets below the expected Lyman-break where interloper objects will be detected. If confirmed, the existence of these ultra-luminous galaxies provides a clear challenge to current simulations. Furthermore, these galaxies will provide a unique insight into the EoR due to their accessibility for follow-up both with JWST and ALMA, where HST/WFC3 F105W data is essential for FIR line measurements that require precise photometric redshifts. ------------------------------------------------------------------------------------ Observations Description ------------------------ The 2 objects we will imaging with HST/WFC3 are widely separated, hence we require 2 separate pointings. Each object is imaged for one orbit and in a single visit. The F105W filter is used with a simple 4 point dither pattern to enable improved PSF reconstruction, splitting each orbit into four separate exposures of ~ 600s each. We use the SPARS50 sampling rate with NSAMP = 14 to ensure a high number of non-destructive reads for cosmic ray rejection. Impact of reduced-gyro operations: 15931( 2) - 22-Jul-2019 16:31:20 - [ 2] In the event of reduced gyro mode (RGM) on these observations, the UDS -603 target would be out of the field of regard (reference slide 5 of J. Mackenty's slides, 6/6/16). For target UVISTA-1307 however we envision little impact of RGM on obtaining the proposed data. As we are only interested in the photometry of this source, the orientation of the observations is not set. Furthermore, the increased aquision time of approx. 120 seconds would not affect our integration time, as we currently have 169 seconds "free" in the orbit plan for this object (filling the orbit with more shorter integrations to reduce this did not increase the exposure time, or SN, hence this spare time). We have no coordinated observations, and only one visit of one orbit is required. ------------------------------------------------------------------------------------ 15931( 2) - 22-Jul-2019 16:31:20 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 UVISTA-1307 GALAXY, HIGH REDSHIFT RA=10H02M31.8100S, J2000 Total H-band magnitude of 24.4 GALAXY DEC=+02D31'17.10" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 2 UDS-603 GALAXY, HIGH REDSHIFT RA=02H17M42.4700S, J2000 Total H-band magnitude of 24.8 GALAXY DEC=-04D58'57.80" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 15931( 2) - 22-Jul-2019 16:31:20 - [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 15931( 2) - 22-Jul-2019 16:31:20 - [ 5] Visit: 01 (First visit) 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 UVISTA-1307 WFC3/IR MULTIAC IR F105W NSAMP=13, SAMP-SEQ=SPARS50 1 DEF PATTERN 1 1 CUM (2411.751 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 | ------------------------------------------------------------------------------------------------------------------------------------ UVISTA-1307 1 WFC3/IR MULTIAC IR F105W 1 none none none 1 N/A CUM UVISTA-1307 1 WFC3/IR MULTIAC IR F105W 2 none none none 1 N/A CUM UVISTA-1307 1 WFC3/IR MULTIAC IR F105W 3 none none none 1 N/A CUM UVISTA-1307 1 WFC3/IR MULTIAC IR F105W 4 none none none 1 N/A CUM 15931( 2) - 22-Jul-2019 16:31:20 - [ 6] Visit: 02 (Second visit) 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 UDS-603 WFC3/IR MULTIAC IR F105W NSAMP=13, SAMP-SEQ=SPARS50 1 DEF PATTERN 1 1 CUM (2411.751 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 | ------------------------------------------------------------------------------------------------------------------------------------ UDS-603 1 WFC3/IR MULTIAC IR F105W 1 none none none 1 N/A CUM UDS-603 1 WFC3/IR MULTIAC IR F105W 2 none none none 1 N/A CUM UDS-603 1 WFC3/IR MULTIAC IR F105W 3 none none none 1 N/A CUM UDS-603 1 WFC3/IR MULTIAC IR F105W 4 none none none 1 N/A CUM 15931( 2) - 22-Jul-2019 16:31:20 - [ 7] Summary Form for Proposal 15931 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/IR ------------------------------------------------------------------------------------------------------------------------------------ Opmodes MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters NSAMP=13, SAMP-SEQ=SPARS50 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F105W ------------------------------------------------------------------------------------------------------------------------------------ Target Names UDS-603, UVISTA-1307 ------------------------------------------------------------------------------------------------------------------------------------