0 Your proposal could not be saved. Submission aborted. Assigned ID: 2612 ----- Attempting Submission 1 (Thu Sep 30 23:04:14 GMT 2021) ----- HST Phase I Proposal 2612 successfully submitted. Receipt: # 2612-1 ----- Attempting Submission 2 (Fri Oct 01 01:46:57 GMT 2021) ----- HST Phase I Proposal 2612 successfully submitted. Receipt: # 2612-2 ----- Attempting Submission 3 (Fri Oct 01 02:14:17 GMT 2021) ----- 0 ----- Attempting Submission 1 (Fri Nov 26 17:55:30 GMT 2021) ----- A Spatially Resolved View of Star Formation in Two Luminous z>=8 Galaxies showing Prominent Dust-Continuum Emission The discovery of some impressively luminous galaxies in the early universe has prompted questions about how such galaxies can build up so quickly. Remarkably, luminous galaxies appear to have built up a significant amount of dust content and shine brightly in the infrared, as early as 600 Myr after the Big Bang. Yet, despite keen interest from the astronomical community, only two particularly luminous galaxies are known showing prominent dust emission at z>=8, only one of which shows a bright ISM cooling line. Clearly, a larger number of IR luminous galaxies need to be identified and characterized in detail. Fortunately, thanks to on-going observations from an ALMA large program, far-IR observations have revealed prominent dust-continuum emission in two additional UV-bright galaxies at z>~8, effectively doubling the number of such sources known in the first 650 Myr. Given the existence of only low spatial resolution imaging data of these sources from the ground, we propose for the necessary HST imaging to obtain a high spatial-resolution view of the unobscured star formation in the sources to match the far-IR view provided by ALMA, allowing for a more integration view of star formation. For better sensitivity and to provide for a resolved view of dust obscuration, two-band F125W+F160W observations are requested. One significant benefit of the proposed observations -- and a key rationale for mid-cycle time -- is this program's significantly improving prospects for detecting ISM-cooling lines in the sources thanks to the improved photometric redshift constraints. We observe 2 candidate ultrabright (mH~24.8 AB) star-forming galaxies at z>8 with dust emission detection from ALMA. These observations provide key information for an ongoing large ALMA program targeting these same sources. In particular, these observations will dramatically improve our ability to detect bright ISM cooling lines in the sources. This point was explicitly recognised and emphasised by the TAC as part of the HST Mid-cycle review, so it would be highly desirable if the observations could be executed before March 2022, when ALMA data on the sources will be collected. To optimize the ease of scheduling, the observations for each source are split into two independent 1-orbit visits (DUSTY-z8-1_visit_1 and DUSTY-z8-1_visit_2, and DUSTY-z8-2_visit_1 and DUSTY-z8-2_visit_2, respectively). Acquisitions in each visit are shared between imaging in the F125W (~0.37 orbit) and F160W (~0.63 orbit) bands (per-source total of ~0.7orbits in the F125W, and ~1.3orbits in the F160W band). We adopt a 4-point dither strategy in both bands, similar to the WFC3-IR-DITHER-BOX-MIN pattern, to improve spatial sampling and limit systematics from potential cosmetic defects and residual cosmic ray hits. We minimized the sampling time of each integration to pursue optimal cosmic ray rejection. It would be highly advantageous if the DUSTY-z8-1_visit_1 and DUSTY-z8-1_visit_2 could be executed during the November 2021 - Feb 01, 2022 window, and DUSTY-z8-2_visit_1 and DUSTY-z8-2_visit_2 during the November 2021 - Feb 26, 2022 window. Execution prior to Feb 15, 2022 would be especially ideal to allow for time to request and implement changes to the ALMA scan strategy. We note that the execution of even one visit per target before March 2022 would greatly improve our ability to scan for the [CII] cooling line in the forthcoming ALMA observations. In the event of Reduced Gyro Mode, given the current short (39sec) unused time in each orbit, our observing strategy would need minor revision to accommodate the additional ~2minutes required for the initial target acquisition. R. Bouwens, M. Stefanon, P. Oesch, R. Bowler, D. Stark and V. Gonzalez are leading experts in the study of high-z galaxy formation and evolution, including identifying candidates from deep multi-wavelength data from HST, Spitzer and major ground-based observatories and in estimating physical properties from those data (e.g., UV slopes, stellar mass, SFR, nebular line emission). H. Inami, S. Schouws, R. Smit, and Y. Fudamoto lead the analysis of the ALMA data that unveiled the dust continuum emission. J. Hodge, H. Inami and P. van der Werf are experts in the field of submillimiter/star-burst galaxies and related data-analysis. All members of the collaboration share expertise in different aspects of the study of high-z galaxy formation and evolution and have contributed to the development of this project. R. Schneider and L. Graziani are experts in modeling dust production. Galaxies 3 false false false false false false true false SUPPORTED GALAXY HIGH REDSHIFT GALAXY J2000 J2000 H~24.8 GALAXY HIGH REDSHIFT GALAXY J2000 J2000 H~24.8 WFC3/IR Imaging No No F125W WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F125W WFC3/IR Imaging No No F160W /Users/mauro/Work/Proposal/HST/hst_C29_MC1_photoz/REBELS_photo-z/OP-cache/REBELS_offset_photoz_mc1_phase2-v11.xml The scheduling data was generated by CASM 29.2. CASM was run in Phase II mode. 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