0 Assigned ID: 682 ----- Attempting Submission 1 (Wed Jan 30 23:27:56 GMT 2019) ----- HST Phase I Proposal 682 (cosmos_bright.apt) successfully submitted. Receipt: # 682-1 ----- Attempting Submission 2 (Wed Jan 30 23:31:22 GMT 2019) ----- This target is not used in this proposal. 0 ----- Attempting Submission 1 (Wed Apr 17 20:55:02 GMT 2019) ----- The unused source is the actual position of our source of interest. We centered our pointing slightly offset, to avoid a bright star. We left this object in APT to allow the reviewer to see where it is. We request two orbits of WFC3 imaging with the F098M filter to confirm the Lyman break and constrain the redshift of a remarkably bright H=24.5 galaxy in the CANDELS COSMOS field. Photometric redshift analyses including previous HST (V, I, J and H-band) and ground-based imaging overwhelmingly prefer a redshift of z ~ 9.5. A galaxy this luminous (in the searched volume) so early in the universe sets tight constraints on the onset of star formation and AGN growth, thus even this single source would be a game changer (regardless of its ionizing source). However, the inclusion of Spitzer/IRAC photometry complicates the picture. Two different deblending methods both successfully subtract bright neighboring galaxies, measuring significant flux at the position of this exceptional source at both 3.6 and 4.5 um. However, the [3.6]-[4.5] color is slightly different between these two methods, with one method measuring a slightly red color, consistent with z~9.5, and the other measuring a slightly blue color, preferring z~2. This systematic uncertainty in the deblending process prevents a concrete determination of the nature of this source. An efficient two orbits of F098M imaging will break this redshift degeneracy. At this depth, if the galaxy is truly at z~2 we will detect it at 5-sigma significance, while a non-detection will rule out all low-redshift solutions, regardless of the IRAC photometry used, at >99.5% confidence. These observations are urgent, as once the nature of this source is known, deep spectroscopy can be pursued to measure the precise redshift, allowing detailed investigations with JWST Cycle 1 spectroscopy. We are observing one source of interest in the F098M filter. We have selected a center position ~40" away from the source, and allowable PAs, to try to exclude a nearby bright star from the image. This submitted APT has one observing window in May-June. We have worked with the contact scientist to create a separate APT for an ORIENT (300) which is observable at the end of the year, should this proposal not be scheduled earlier. We have designed a set of four exposures per orbit, using the "DITHER-BLOB" dither pattern, with a larger dither of two points (one per orbit), with four sub-dithers per orbit. We selected exposures with SPARS25 and NSAMP=13, based on recommendations of previous users, and to allow exposure times to fill our orbits. We have verified a wide schedulability window for our program. I note that we have centered our pointing on the target called "COSMOS-Z910-14822". Our actual target is known by "COSMOS-SOURCE", which we used to ensure it would fall on the detector across the allowable ORIENT range in Aladin. Galaxies and the IGM 3 false false false false false false false SUPPORTED GALAXY HIGH REDSHIFT GALAXY NO J2000 J2000 GALAXY HIGH REDSHIFT GALAXY J2000 WFC3/IR Imaging No No F098M POS-TARG DITHER DITHER 4 5.183 WFC3-IR-DITHER-BOX-MIN false 74.653 true 0.365 0.572 2 41.859 POS-TARG WFC3-IR-DITHER-BLOB 18.528 1 true 1555534442494 The scheduling data was generated by CASM 27.0. CASM was run in Phase II mode. (Tic-Visit :proposal-id 15697 :visit-id "01" :proposal-version -1 :trans-version "20181130" :date "17-Apr-2019 13:54:01.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 3899632 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15697 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 15697 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2736 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3142 :pcs-gap 0 ) (Tic-Orbit :proposal-id 15697 :visit-id "01" :orbit-number 2 :pcs-time 302 :si-vis-utilization 2736 :al-overhead-at-end 0 :internal-dur-at-end 614 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3142 :pcs-gap 0 ) true 2 0