11701( 4) - 18-Feb-2010 14:38:04 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11701 Version: 4 Check-in Time: 18-Feb-2010 14:38:04 STScI Edit Number: 1 Title The jackpot in technicolor: photometric redshift and mass to light decomposition of a double Einstein Ring ------------------------------------------------------------------------------------ Type Cycle GO 17 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Tommaso L. Treu University of California - Santa Barbara CoI: Dr. Raphael Gavazzi CNRS, Institut d'Astrophysique de Paris N CoI: Dr. Philip J. Marshall University of California - Santa Barbara N CoI: Dr. Adam S. Bolton University of Hawaii N CoI: Prof. Leon Koopmans Kapteyn Astronomical Institute N CoI: Dr. Leonidas Moustakas Jet Propulsion Laboratory N ------------------------------------------------------------------------------------ Abstract The structure, formation and evolution of early-type galaxies is still largely an open problem in cosmology: how does the Universe evolve from large linear scales dominated by dark matter to the non-linear scales of galaxies, where baryons and dark matter both play important, interacting, roles? To understand the complex physical processes involved in their formation scenario, it is critically important to understand the relative distribution of luminous and dark matter at galactic scales. Over the last four years, using HST, the SLACS collaboration has discovered some 100 new gravitational lenses and developed a toolbox to tackle these issues by combining new non-parametric strong lensing techniques, stellar dynamics, and weak gravitational lensing. Among the 100 new lenses, we discovered the first double Einstein Ring, the so-called "jackpot". The presence of two rings at different radii provides qualitatively new insights into the distribution of luminous and dark matter at 10 kpc scales. Via a joint lensing and dynamical analysis, this system has the potential to deliver the most precise measurements on galactic scales of the inner slope of dark matter halos, of the total mass profile, and of the stellar mass to light ratio. Unfortunately, the precision is currently limited by the lack of a redshift for the outer ring, in spite of ultradeep spectroscopy at the 10m Keck Telescope. We propose to otbain F336W and F438W WFC3 images of the system, which in combination with our existing F606W, F814W and F160W images will allow us to obtain a photo-z for the outer ring, precise enough to fully realize the potential of this system. The multicolor HST images will also be used to derive a stellar mass-to-light and constrain the initial mass function by comparison with the lens and dynamical measurement. ------------------------------------------------------------------------------------ Observations Description ------------------------ The immediate goal of the HST observations is to obtain multicolor photometry to pinpoint the photometric redshift of the outer ring. The redshift is predicted by the gravitational lens model to be z=2.6+1.0-0.7, a range where UV and NIR colors are essential to obtain unbiased and precise photo-z (e.g., Abdalla et al.\ 11701( 4) - 18-Feb-2010 14:38:04 - [ 2] 2007). The main reason is that the UV filter helps constraining the redshift via the Lyman-alpha forest absorption a z>2, while the optical to NIR colors help constrain the redshift via the detection of a possible 4000 \AA\, break at 1 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SLACSJ0946+ WFC3/UVI ACCUM UVIS1 F438W CR-SPLIT=NO 1 500 S PATTERN 1 1 1006 S see below ------------------------------------------------------------------------------------------------------------------------------------ 2 SLACSJ0946+ WFC3/UVI ACCUM UVIS1 F336W CR-SPLIT=NO 1 1100 S PATTERN 1 2 1006 S see below ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ SLACSJ0946+1006 1 WFC3/UVI ACCUM UVIS1 F438W 1 none none none 1 630.0 S S SLACSJ0946+1006 1 WFC3/UVI ACCUM UVIS1 F438W 2 none none none 1 630.0 S S SLACSJ0946+1006 1 WFC3/UVI ACCUM UVIS1 F438W 3 none none none 1 630.0 S S SLACSJ0946+1006 1 WFC3/UVI ACCUM UVIS1 F438W 4 none none none 1 630.0 S S SLACSJ0946+1006 2 WFC3/UVI ACCUM UVIS1 F336W 1 none none none 2 1443.0 S S SLACSJ0946+1006 2 WFC3/UVI ACCUM UVIS1 F336W 2 none none none 2 1443.0 S S SLACSJ0946+1006 2 WFC3/UVI ACCUM UVIS1 F336W 3 none none none 3 1443.0 S S SLACSJ0946+1006 2 WFC3/UVI ACCUM UVIS1 F336W 4 none none none 3 1443.0 S S 11701( 4) - 18-Feb-2010 14:38:04 - [ 6] Summary Form for Proposal 11701 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1, PATTERN 1 2 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F336W, F438W ------------------------------------------------------------------------------------------------------------------------------------ Target Names SLACSJ0946+1006 ------------------------------------------------------------------------------------------------------------------------------------