0 Assigned ID: 811 ----- Attempting Submission 1 (Fri Apr 07 19:59:24 GMT 2017) ----- HST Phase I Proposal 811 (CYCLE25APT.apt) successfully submitted. Receipt: # 811-1 ----- Attempting Submission 2 (Fri Apr 07 20:52:15 GMT 2017) ----- Dithering sequences have been adjusted so that F105W observations are always in the middle of an orbit. All dithers are to unique positions for a given filter. 31558482 ----- Attempting Submission 1 (Tue Jul 11 19:59:27 GMT 2017) ----- ----- Attempting Submission 2 (Tue Jul 11 20:08:20 GMT 2017) ----- ----- Attempting Submission 3 (Thu Sep 21 14:02:13 GMT 2017) ----- The HST Frontier Field MACS 1159.5+2223: Flanking Observations for Intracluster Light We propose a 6 orbit WFC3/IR imaging program targeting the environs of the HST Frontier Field cluster MACS 1149.5+2223 to obtain a comprehensive view of the intracluster stellar population in a massive galaxy cluster. WFC3/IR enables a vast improvement over ground-based studies in mapping emission from diffuse stellar populations. Our proposed observations are designed to build upon the existing investment in the Frontier Fields to conduct a new, more complete census of the intracluster light (ICL) extending out to ~750 kpc. The requested observations are constructed to span the gap between the primary and parallel HFF pointings, detecting ICL to a surface brightness of 29.5 mag per square arcsec in F160W (equivalent to 31.5 mag per square arcsec in V-band). This depth is sufficient to trace the radial ICL profile out to ~750 kpc from the BCG. These data will also yield a high-fidelity calibration of the background sky level, enabling two-dimensional mapping of the distribution and color of intracluster light down to 27 mag per square arcsec in F160W. From these maps we will quantify spatial variation in the ratio of the stellar baryons to the ICM, establishing whether the observed low scatter in the global ratio masks underlying smaller scale inhomogeneities due to astrophysical processes in the cluster. The requested observations further serve as a pilot program, enabling future similar analyses with the full ensemble of HFF clusters, and developing techniques that will be required for such low surface brightness programs with upcoming facilities including Euclid and WFIRST. Our proposed observations are designed to build upon the existing investment in the Frontier Fields to conduct a new, more complete census of the intracluster light (ICL) extending out to ~750 kpc. The requested observations are constructed to span the gap between the primary and parallel HFF pointings, detecting ICL to a surface brightness of 29.5 mag per square arcsec in F160W (equivalent to 31.5 mag per square arcsec in V-band). Geometry: The basic geometry for the proposed observations is a linear series of overlapping WFC3/IR frames bridging the gap between the primary and parallel HFF fields (Figure 3). With proper overlap, the bridging fields can be used to correct for the temporal differences between the primary and parallel fields and enable continuous determination of the ICL brightness with radius. Three exposures is the minimum number required to have meaningful overlap between frames, as the separation between the edges of the primary and parallel HFF fields is approximately 235". Three exposures enables an overlap of 20% between adjacent frames. For 20% overlap, the residual systematic uncertainty will be mu > 31 mag/arcsec^2 in F160W. It is critical that the bridging fields all have the same orientation as one another, and the same orientation as the HFF pointings to within 5 degrees. Filters: The HST Frontier Fields program acquires data for each cluster in 3 ACS bands (F435W, F606W, F814W) and 4 WFC3/IR bands (F105W, F125W, F140W, F160W). For this program, the science is driven by the need to extend spatial coverage in the WFC3/IR bands, both because of the smaller field-of-view of WFC3/IR and because the IR bands are most sensitive to intracluster light. The F105W and F160W filters provide a maximal wavelength lever arm in the IR bands for mapping out color gradients. Depth: The two requirements for the depth are that the data yield sufficient fidelity for the sky level determination, and sufficient sensitivity to enable a radial measurement of the ICL extending to mu_160 = 29.5 mag/arcsec^2. For the sensitivity, the observations benefit from averaging in annular bins extending over the width of the detector. A single orbit in each filter is sufficient to reach SNR> 10 for the radial profile at mu_160 = 29.5 mag/arcsec^2. A 20% determination of the surface brightness at mu160 = 29.5 mag/arcsec^2 requires that the 1 sigma error in the background correspond to mu= 31 mag/arcsec^2, which is well-matched to the flatfielding described above. Special Requirements: All observations should be taken in LOW SKY (our depth calculations account for this). These conditions gain us 0.3 mag/arcsec^2 relative to the average sky, enabling us to increase the spatial extent over which we can resolve structure in the ICL. We request that the orientation of the WFC3/IR images be aligned with the Frontier Fields WFC3/IR parallel observations to within 5 degrees. This orientation is designed to maximize overlap for relative sky calibration during LOW SKY conditions. Parallel Fields: To maximize the legacy value of this program and enhance the Frontier Fields data sets, we are taking parallel observations with ACS, split between F814W and F606W. These data will enable an extension of weak lensing analyses into these flanking regions. Galaxies and the IGM 0 false false false false false false SUPPORTED CLUSTER OF GALAXIES RICH CLUSTER J2000 J2000 CLUSTER OF GALAXIES RICH CLUSTER J2000 J2000 CLUSTER OF GALAXIES RICH CLUSTER J2000 J2000 WFC3/IR Imaging No No F105W WFC3/IR Imaging No No F160W ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F814W /Users/anthonyhg/OP-cache/15308-v01.xml Hst Same orient constraint links visits (01 02 03) The scheduling data was generated by CASM 25.2. CASM was run in Phase II mode. 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CASM was run in Phase II mode. 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