0 Assigned ID: 783 ----- Attempting Submission 1 (Fri Apr 08 20:22:21 GMT 2016) ----- Orient constraints have been added to maximize legacy value of the dataset by maximizing overlap with archived HST data, but can be relaxed if needed to increase schedulability. For the observations, it will be critical to verify that the faint science target will not fall on top of one of the WFC3 blobs. A preliminary analysis from the WFC3 blob map indicates that this is unlikely to happen with the proposed configuration, but a slight shift of pointing might be advised depending on availability of more accurate information on the orient actually scheduled. -751330702 ----- Attempting Submission 1 (Tue Jul 19 00:50:43 GMT 2016) ----- How bright can galaxies be during the epoch of reionization? Recent Hubble observations challenged prior expectations and led to the identification of two surprisingly luminous galaxies with spectroscopic confirmation within 600 Myr from the Big Bang: A source with m_AB=25.3 at z=8.7 and another with m_AB=26.0 at z=11.1. Such galaxies hint a tension with the assumption of a luminosity function (LF) with a Schechter (exponential) profile at the bright end, otherwise well established after reionization is complete. A clear excess of L>L* galaxies, if confirmed, would be a strong indication of a different physics of galaxy formation at play during the epoch of reionization. Leveraging upon the large-area pure-parallel BoRG survey, we identified a yet more luminous galaxy candidate at z>8, a source with m_AB=24.5, corresponding to M_AB=-22.8, almost ten times brighter than the Milky Way! The F105W dropout is detected at very high S/N in the IR, has no optical flux and a compact size (r_e=0."17) leading to a most likely redshift of z~8.4. However, a secondary peak in the redshift distribution is present at z~1.8 (p~10%). To exclude this solution and confirm the high-z nature of BoRG_0116+1425, we propose observations in the medium-band F098M filter. If the galaxy is an interloper, it will have m_AB~26.4 in F098M, while it will be undetected if at z>7.8. Since a Schechter-like LF predicts less than 0.002 galaxies as bright as BoRG_0116+1425 in the survey area, this single orbit proposal has the potential to unequivocally establish departure from a Schechter LF at confidence greater than 99.8%, supporting theoretical predictions of decreasing efficiency of AGN feedback at high-z The observation consists of one 1-orbit visit of F098M imaging (4 exposures). We selected 4 13-NSAMP SPARS50 exposures to fill the orbit, using a 4-point minimum box with optimal half-pixel sampling in both x and y. Timing requirements are requested to coordinate ground-based follow-up observations of targets selected by these HST observations using the MOSFIRE spectrograph on Keck. Intergalactic Medium and Cosmology Galaxies 3 false false false false false false SUPPORTED GALAXY HIGH REDSHIFT GALAXY Dropout coordinates are: 01 16 8.3280 +14 24 9.36 Field of view has been centered to increase overlap with original BoRG field J2000 J2000 24.5 in F160W WFC3/IR Imaging No No F098M POS-TARG DITHER 0.572 LINE 0.365 false false 74.653 4 18.528 WFC3-IR-DITHER-BOX-MIN 1 false 1468799144559 The scheduling data was generated by CASM 24.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 14701 :visit-id "01" :proposal-version -1 :trans-version "20160601" :date "18-Jul-2016 09:45:44.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 1044528 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14701 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14701 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2840 :al-overhead-at-end 0 :internal-dur-at-end 519 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3218 :pcs-gap 0 ) true 1 0