0 Assigned ID: 1254 ----- Attempting Submission 1 (Fri Jan 29 18:30:24 GMT 2016) ----- 0 ----- Attempting Submission 1 (Fri Apr 08 04:33:10 GMT 2016) ----- Resolving the Stellar Populations, Structure, and Kinematics of the NIR-Brightest Lensed Galaxy at z=2 We have recently discovered and spectroscopically confirmed a remarkably bright galaxy at z=1.95, dubbed RG2M0138, that is strongly lensed by the cluster MACSJ0138.0-2155. At near-infrared wavelengths, our target appears to be the brightest distant lensed galaxy known by almost an order of magnitude. Furthermore, whereas the majority of lensed galaxies are lower-mass star-forming systems, RG2M0138 is instead a rare example of a lensed compact quiescent galaxy. The high magnification of this exciting source will enable unique insights into the spatially-resolved stellar populations and kinematics of a compact quiescent galaxy. Such galaxies comprise about half of the massive (>10^11 Msol) galaxy population at z~2, but without lensing can only be marginally resolved even with HST. The proposed observations will address several key questions concerning the formation of early quiescent galaxies using high-resolution imaging from ACS and WFC3-IR, resolved rest-optical spectroscopy from Keck, and IRAC imaging recently approved via a DDT request. With these data, we will: (1) Resolve the central stellar density of RG2M0138 to ~1/10 of its effective radius, thereby stringently testing the hypothesized "inside out" growth paradigm; (2) Constrain the formation history of RG2M0138 by probing the homogeneity of its stellar population, breaking parameter degeneracies using our unique resolved data spanning rest-UV to NIR wavelengths; and (3) Create an accurate lens model and source plane reconstruction, which in concert with our existing Keck spectroscopy are needed to quantify rotation and measure a robust Jeans-based dynamical mass. Two orbits of WFC3-IR imaging are divided amongst F160W and F105W exposures, each executed with a 4 point dither pattern enlarged to maintain sub-pixel sampling while dithering over areas of poor flat fielding. The brightest cluster galaxy (BCG) placed at the detector center. Two orbits of ACS imaging are devoted to F555W imaging with 4 exposures. The 4-point dither pattern includes a large step to cover the chip gap coupled with a small step for redundancy and sub-pixel sampling. The BCG is placed at the center of WFC1. UNRESOLVED STELLAR POPULATIONS AND GALAXY STRUCTURE 3 false false false false false false SUPPORTED CLUSTER OF GALAXIES GRAVITATIONAL LENS J2000 J2000 WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F105W ACS/WFC Imaging No No F555W POS-TARG DITHER 5.148 Scaled point and line spacing by 9x to better avoid bad areas of flat field while maintaining half pixel sampling. LINE 3.285 false true 74.653 4 18.528 WFC3-IR-DITHER-BOX-MIN 1 false POS-TARG DITHER DITHER 2 3.011 2-point wide dither to cover chip gap with a 2-point subpixel pattern at each position. ACS-WFC-DITHER-LINE false true 0.149 2 85.28 POS-TARG ACS-WFC-DITHER-LINE 34.25 2 true /Users/anewman/Documents/Proposals/hst_cycle23mid/OP-cache/Cycle23MidPhaseII-v01.xml The scheduling data was generated by CASM 24.0. CASM was run in Phase II mode. 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