0 Assigned ID: 1219 ----- Attempting Submission 1 (Fri Oct 02 03:57:20 GMT 2015) ----- HST Phase I Proposal 1219 (newz9.apt) successfully submitted. Receipt: # 1219-1 ----- Attempting Submission 2 (Fri Oct 02 04:01:02 GMT 2015) ----- HST Phase I Proposal 1219 (newz9.apt) successfully submitted. Receipt: # 1219-2 ----- Attempting Submission 3 (Fri Oct 02 04:10:29 GMT 2015) ----- HST Phase I Proposal 1219 (newz9.apt) successfully submitted. Receipt: # 1219-3 ----- Attempting Submission 4 (Fri Oct 02 04:20:39 GMT 2015) ----- HST Phase I Proposal 1219 (newz9.apt) successfully submitted. Receipt: # 1219-4 ----- Attempting Submission 5 (Fri Oct 02 04:24:24 GMT 2015) ----- HST Phase I Proposal 1219 (newz9.apt) successfully submitted. Receipt: # 1219-5 ----- Attempting Submission 6 (Fri Oct 02 04:33:26 GMT 2015) ----- HST Phase I Proposal 1219 (newz9.apt) successfully submitted. Receipt: # 1219-6 ----- Attempting Submission 7 (Fri Oct 02 05:48:08 GMT 2015) ----- HST Phase I Proposal 1219 (newz9.apt) successfully submitted. Receipt: # 1219-7 ----- Attempting Submission 8 (Fri Oct 02 05:57:14 GMT 2015) ----- HST Phase I Proposal 1219 (newz9.apt) successfully submitted. Receipt: # 1219-8 0 ----- Attempting Submission 1 (Thu Dec 10 22:42:36 GMT 2015) ----- At present, little is known about the spectral properties, stellar masses, or even just volume densities of the brightest, most massive galaxies in the early universe. The extreme rarity of such galaxies makes it very difficult to collect sizable samples and make progress in our understanding these sources. In one recent effort, we made use of a 750 arcmin**2 search over all 5 CANDELS fields with follow-up observations from an HST program to increase present samples of bright (H<27), z>~9-11 galaxies from 6 to 16. Yet, no credible z>~9 galaxies were identified that were brighter than 25.9 mag, consistent with the low volume density of such galaxies expected in even 1000 arcmin**2 surveys. To make further progress we are forced to search for especially bright galaxies at slightly lower redshift, z=8-9. By exploiting the wide-area CANDELS HST+Spitzer survey, we recently identified 3 tantalizing sources. While the first of these galaxies was spectroscopically confirmed (z=8.683), the nature of the other 2 candidates is uncertain, but they are consistent with being z~8.5 galaxies. If confirmed, this would imply a higher than expected number density of bright z~8-10 galaxies and signify a departure from a Schechter luminosity function. If these sources are at z~2 instead, this would imply more of an exponential cut-off at the bright end for z>8 LFs. Here we propose to answer this question with a small request for HST follow-up imaging. This will not only give us insight into feedback and dust extinction in early massive galaxy evolution, but will provide crucial input to optimize current searches for bright z>8 galaxies in preparation for JWST. The proposed observations are to test the nature of two plausible z>8 galaxies, for which we do not have deep HST observations at 1 micron to determine if the apparent Lyman-break is robust. These sources are of interest because they would both be ~2x brighter than any apparently reliable z~9 galaxies identified over the 5 CANDELS fields. The most powerful way of determining whether these candidates are likely at z~9 is by obtaining deep observation just blueward of the apparent Lyman-break at a wavelength of ~1 micron in the F098M filter which lies just blueward of the break for z>8 galaxies. All expected contaminants would show a modest amount of flux at this wavelength, while bona-fide z>8 galaxies would not. We can obtain tight constraints on the nature of these sources if we reach 3 magnitudes fainter than the near-IR continuum at 1 micron. This requires that we reach ~28 mag in the F098M-band at 1 sigma. We can accomplish this for each candidate with just a 1 orbit observation. Each of the 2 visits in our program is split into 4 ~640-second exposures oriented around a 1"-arcsec square dither pattern. SPARS100 or SPARS50 is adopted as the acquisition mode, given its overall efficiency and broad use in other HST programs. COSMOLOGY 3 false false false false 0 0 0 0 0 SUPPORTED GALAXY HIGH REDSHIFT GALAXY J2000 J2000 GALAXY HIGH REDSHIFT GALAXY NO J2000 J2000 WFC3/IR Imaging No No F098M WFC3/IR Imaging No No F098M 1449787291633 /Users/bouwens/OP-cache/newz9-v01.xml The scheduling data was generated by CASM 23.2. CASM was run in Phase II mode. 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