14630( 4) - 29-Sep-2016 15:53:04 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14630 Version: 4 Check-in Time: 29-Sep-2016 15:53:04 STScI Edit Number: 0 Title A unique probe of the dark matter distribution in a halo at z=1: A strong lens with a bright central image ------------------------------------------------------------------------------------ Type Cycle GO 24 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Thomas E. Collett University of Portsmouth Y CoI: Prof. Tommaso L. Treu University of California - Los Angeles Y CoI: Dr. David Bacon University of Portsmouth N CoI: Dr. Anupreeta More Institute for Physics and Mathematics of N the Universe CoI: Dr. Elizabeth Buckley-Geer Fermi National Accelerator Laboratory N (FNAL) CoI: Dr. Adam Amara Eidgenossiche Technische Hochschule (ETH) N CoI: Dr. Brian D. Nord Fermi National Accelerator Laboratory N (FNAL) CoI: Mr. Simon Birrer Eidgenossische Technische Hochschule N Zurich (ETHZ) CoI: Prof. Bob Nichol University of Portsmouth N ------------------------------------------------------------------------------------ Abstract Cosmological dark matter simulations predict that the central regions of halos have 1/r density cusps. Baryonic processes and dark matter microphysics may resculpt these dark matter cusps, but these process are poorly understood and only weakly constrained by observations of a few low redshift halos. We have discovered a strong lensing cluster at redshift 1 that includes a bright central image like no other: the central image is resolved! This makes for a uniquely powerful probe of the central regions of a dark matter halo without the need for additional dynamical constraints. An NFW halo cannot reconstruct the data: modelling of our DECam imaging with a double powerlaw density profile shows that the central slope must be much shallower than 1/r over at least the central 35 kpc. We propose to obtain high resolution imaging of this lens with WFC3. This data will be able to conclusively distinguish between a large core and an even larger shallow cusp. It will be the first such measurement at z = 1 and the most precise measurement of the central DM profile of a cluster ever made. The data will also allow for an investigation of dark matter substructures at z=1. When combined with cosmological hydrodynamical simulations these results will place new constraints on the range of baryonic processes and DM microphysics that can flatten the central density profiles of cluster DM halos over kiloparsec scales. ------------------------------------------------------------------------------------ Observations Description ------------------------ We require high resolution imaging of the target in F475W, F606W, F125W and F140W. 14630( 4) - 29-Sep-2016 15:53:04 - [ 2] The required signal-to-noise is achieved with 3 orbits of 606, 2 orbits of 475 and 1 orbit split between 125 and 140. Since resolution is key to our project, we will use 4 dithers in each band to optimally sample the psf. Our target is ~30 arcseconds in diameter and signal-to-noise across the whole target is important. We therefore centre the target on the center of a single UVIS chip: this avoids the target falling on the chip gap. We centre the IR chip on the center of our target. In order to maximise the field of view around the target, we centre the UVIS exposures on chip 1 for the first visit, and chip 2 for the second visit. We offset the second visit by 2 arcseconds so that the full dataset covers the chip gap. Our proposed observations are therefore: Two visits of 3 orbits. First visit: Apperture = UVIS1, and IR Orbit 1: WFC3-UVIS: Dither 1 (F606 then F475), Dither 2 (F606, F475) Orbit 2: WFC3-UVIS: Dither 3 (F606, F475), Dither 4 (F606, F475) Orbit 3: WFC3-IR: Dither 1 (F125, F140), Dither 2 (F125, F140), Dither 3 (F125, F140), Dither 4 (F125, F140) Second visit (alligned with first visit): Apperture = UVIS2, with a small offset to cover the chip gap. Orbit 1: WFC3-UVIS: Dither 1 (F606), Dither 2 (F606), Dither 3 (F606), Dither 4 (F606) Orbit 2: WFC3-UVIS: Dither 1 (F606, F475), Dither 2 (F606, F475) Orbit 3: WFC3-UVIS: Dither 3 (F606, F475), Dither 4 (F606, F475) ------------------------------------------------------------------------------------ 14630( 4) - 29-Sep-2016 15:53:04 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 DESJ2011-522 CLUSTER OF GALAXIES, RA=20H11M7.0000S, J2000 V = 24 8 EINSTEIN RING, DEC=-52D28'16.00" GRAVITATIONAL LENS, HIGH REDSHIFT CLUSTER Reference Frame: Other: DES ------------------------------------------------------------------------------------------------------------------------------------ 14630( 4) - 29-Sep-2016 15:53:04 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.173 Line_Spacing 0.112 Coordinate_Frame POS-TARG Pattern_Orient 23.884 Angle_Between_Sides 81.785 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-IR-DITHER-BOX-MIN Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.572 Line_Spacing 0.365 Coordinate_Frame POS-TARG Pattern_Orient 18.528 Angle_Between_Sides 74.653 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 14630( 4) - 29-Sep-2016 15:53:04 - [ 5] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 DESJ2011-52 WFC3/UVI ACCUM UVIS1 F475W 1 600 S POS TARG null, -1; 28 S see below PATTERN 1 1-2 (2690 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 DESJ2011-52 WFC3/UVI ACCUM UVIS1 F606W 1 600 S POS TARG null, -1 28 S see below (2690 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 DESJ2011-52 WFC3/IR MULTIAC IR F125W NSAMP=12, SAMP-SEQ=STEP50 1 DEF PATTERN 2 3-4 28 CUM (1396.932 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 DESJ2011-52 WFC3/IR MULTIAC IR F140W NSAMP=12, SAMP-SEQ=STEP50 1 DEF 28 CUM (1396.932 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ DESJ2011-5228 1 WFC3/UVI ACCUM UVIS1 F475W 1 none none none 1 659.0 S S DESJ2011-5228 1 WFC3/UVI ACCUM UVIS1 F475W 2 none none none 1 659.0 S S DESJ2011-5228 1 WFC3/UVI ACCUM UVIS1 F475W 3 none none none 2 686.0 S S DESJ2011-5228 1 WFC3/UVI ACCUM UVIS1 F475W 4 none none none 2 686.0 S S DESJ2011-5228 2 WFC3/UVI ACCUM UVIS1 F606W 1 none none none 1 659.0 S S DESJ2011-5228 2 WFC3/UVI ACCUM UVIS1 F606W 2 none none none 1 659.0 S S DESJ2011-5228 2 WFC3/UVI ACCUM UVIS1 F606W 3 none none none 2 686.0 S S DESJ2011-5228 2 WFC3/UVI ACCUM UVIS1 F606W 4 none none none 2 686.0 S S DESJ2011-5228 3 WFC3/IR MULTIAC IR F125W 1 none none none 3 N/A CUM DESJ2011-5228 3 WFC3/IR MULTIAC IR F125W 2 none none none 3 N/A CUM 14630( 4) - 29-Sep-2016 15:53:04 - [ 6] Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ DESJ2011-5228 3 WFC3/IR MULTIAC IR F125W 3 none none none 3 N/A CUM DESJ2011-5228 3 WFC3/IR MULTIAC IR F125W 4 none none none 3 N/A CUM DESJ2011-5228 4 WFC3/IR MULTIAC IR F140W 1 none none none 3 N/A CUM DESJ2011-5228 4 WFC3/IR MULTIAC IR F140W 2 none none none 3 N/A CUM DESJ2011-5228 4 WFC3/IR MULTIAC IR F140W 3 none none none 3 N/A CUM DESJ2011-5228 4 WFC3/IR MULTIAC IR F140W 4 none none none 3 N/A CUM 14630( 4) - 29-Sep-2016 15:53:04 - [ 7] Visit: 02 Visit Requirements: SAME ORIENT AS 01 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 DESJ2011-52 WFC3/UVI ACCUM UVIS2 F606W 1 600 S POS TARG null, 1; 28 S see below PATTERN 1 1 (2676 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 DESJ2011-52 WFC3/UVI ACCUM UVIS2 F475W 1 600 S POS TARG null, 1; 28 S see below PATTERN 1 2-3 (2744 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 DESJ2011-52 WFC3/UVI ACCUM UVIS2 F606W 1 600 S POS TARG null, 1 28 S see below (2744 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ DESJ2011-5228 1 WFC3/UVI ACCUM UVIS2 F606W 1 none none none 1 669.0 S S DESJ2011-5228 1 WFC3/UVI ACCUM UVIS2 F606W 2 none none none 1 669.0 S S DESJ2011-5228 1 WFC3/UVI ACCUM UVIS2 F606W 3 none none none 1 669.0 S S DESJ2011-5228 1 WFC3/UVI ACCUM UVIS2 F606W 4 none none none 1 669.0 S S DESJ2011-5228 2 WFC3/UVI ACCUM UVIS2 F475W 1 none none none 2 686.0 S S DESJ2011-5228 2 WFC3/UVI ACCUM UVIS2 F475W 2 none none none 2 686.0 S S DESJ2011-5228 2 WFC3/UVI ACCUM UVIS2 F475W 3 none none none 3 686.0 S S DESJ2011-5228 2 WFC3/UVI ACCUM UVIS2 F475W 4 none none none 3 686.0 S S DESJ2011-5228 3 WFC3/UVI ACCUM UVIS2 F606W 1 none none none 2 686.0 S S DESJ2011-5228 3 WFC3/UVI ACCUM UVIS2 F606W 2 none none none 2 686.0 S S DESJ2011-5228 3 WFC3/UVI ACCUM UVIS2 F606W 3 none none none 3 686.0 S S DESJ2011-5228 3 WFC3/UVI ACCUM UVIS2 F606W 4 none none none 3 686.0 S S 14630( 4) - 29-Sep-2016 15:53:04 - [ 8] Summary Form for Proposal 14630 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR, UVIS1, UVIS2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/IR, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters NSAMP=12, SAMP-SEQ=STEP50 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1, PATTERN 1 1-2, PATTERN 1 2-3, PATTERN 2 3-4, POS TARG null, -1, POS TARG null, 1, SAME ORIENT AS 01 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F125W, F140W, F475W, F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names DESJ2011-5228 ------------------------------------------------------------------------------------------------------------------------------------