14210( 3) - 19-May-2016 09:58:04 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14210 Version: 3 Check-in Time: 19-May-2016 09:58:04 STScI Edit Number: 0 Title Improved masses for two new low-redshift strong lens galaxies: Do giant ellipticals really have a heavy IMF? ------------------------------------------------------------------------------------ Type Cycle GO 23 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Russell Smith Durham Univ. Y CoI: Dr. John Lucey Durham Univ. N CoI: Prof. Charlie Conroy Harvard University N ------------------------------------------------------------------------------------ Abstract We propose WFC3/UVIS imaging of newly-identified strong gravitational lenses from SNELLS, the "SINFONI Nearby Elliptical Lens Locator Survey", at the ESO VLT. Our novel approach uses IFU observations to search for lensed background line emitters behind very low redshift (z<0.06) massive ellipticals. The key characteristic of such nearby lenses is that the gravitional deflections are dominated by stellar mass, with only very small contributions from dark matter. As such, they provide uniquely robust constraints on the stellar mass-to-light ratio (M/L), and hence the initial mass function (IMF). To date, SNELLS has discovered two new lenses, SNL-1 at z=0.031 and SNL-2 at z=0.052. Analysing these systems, as well as the previously-known low-z lens ESO325-G004, we found that all three have M/L consistent with a standard MW-like IMF. This result is very surprising in the context of recent works which favour Salpeter or bottom-heavy IMFs in massive ellipticals. A major limitation of our present analysis is that SNL-1 and SNL-2 are two-image systems, and the arcs are unresolved in our ground-based observations. As a result, the lensing mass is degenerate with the component of external shear along the image separation axis. This degeneracy can be broken by measuring the tangential extent of the arcs (or more generally, the detailed structure of the lensed images). In this application, we propose HST observations which will spatially resolve the arcs, and greatly improve the robustness of our lensing mass estimates. The data will reduce the error on M/L by a factor ~5 and, combined with ongoing deep spectroscopy from the VLT, lead to tighter derived constraints on the IMF. ------------------------------------------------------------------------------------ Observations Description ------------------------ The targets are two nearby (z=0.03, 0.05) early-type galaxies behind which we have discovered multiply-imaged background line emitters. The aim of the observations is to measure accurate position, flux and size of the lensed images, for improved modelling of the lens system, narrowing the constraints on the stellar mass of the foreground galaxy. We observe each target in a blue bandpass (F336W or F390W, depending on 14210( 3) - 19-May-2016 09:58:04 - [ 2] target), to improve contrast between the star-forming background galaxy and the very red foreground galaxy. We also aquire imaging in a red bandpass (F814W), to help model the stellar mass distribution in the lens. The observation should be fairly straightforward, with a simple three-point offset pattern in each band for cosmic ray and detector defect rejection. We elected to use post-flash to mitigate CTE losses in the F336W observations (also for F814W where the exposures are short). This might not be strictly necessary for the primary science, because the "targets", i.e. the lensed sources, will sit on a substantial background (actually foreground!) of light from the lens galaxy. This also means that post-flash will not add significant extra noise for our purposes, and using it should improve the archival value of the data. ====================== Summary of changes since original Phase II submission: Added a roll-range restriction for SNL-1. Changed to C1K1C-CTE aperture to keep target close to the amplifier. Switched to the standard small 3-point line dither, instead of the large 1-arcsec dither as before. ------------------------------------------------------------------------------------ 14210( 3) - 19-May-2016 09:58:04 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 ESO286-G022 GALAXY, ELLIPTICAL, RA=21H00M28.7380S, J2000 Z = lens J=11.8, source U=25 GRAVITATIONAL LENS DEC=-42D25'23.27" 0.031 Reference Frame: ICRS Comments: Redshift is given for the lens galaxy; source redshfift is z=0.9 ------------------------------------------------------------------------------------------------------------------------------------ 2 2MASXJ014142 GALAXY, GRAVITATIONAL RA=01H41M42.3000S, J2000 Z = lens J=11.9, source U=25 32-0735281 LENS, LENTICULAR DEC=-07D35'28.00" 0.052 Reference Frame: ICRS Comments: Redshift is given for the lens galaxy; source redshfift is z=2.0 ------------------------------------------------------------------------------------------------------------------------------------ 14210( 3) - 19-May-2016 09:58:04 - [ 4] Visit: 03 (SNL-1) Visit Requirements: ORIENT 0D TO 300 D; ORIENT 330D TO 359 D On Hold Comments: Additional Comments: Roll range restriction to avoid the brightest star (although would be on opposite corner of the field w.r.t the target). In practice, the orbit planner shows that for late 2016 this target can only be observed near 80 deg. Now using C1K1C-CTE window to place closer to amplifier and using small 3-point line-dither. 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 ESO286-G022 WFC3/UVI ACCUM UVIS2-C1K F814W FLASH=5 1 350 S (350 POS TARG +0.185, +0.197 S 1C-CTE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ESO286-G022 WFC3/UVI ACCUM UVIS2-C1K F814W FLASH=5 1 350 S (350 POS TARG 0, 0 S 1C-CTE S) ------------------------------------------------------------------------------------------------------------------------------------ 3 ESO286-G022 WFC3/UVI ACCUM UVIS2-C1K F336W FLASH=8 1 1471 S POS TARG +0.185, +0.197 S 1C-CTE (1471 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 ESO286-G022 WFC3/UVI ACCUM UVIS2-C1K F814W FLASH=5 1 350 S (350 POS TARG +0.092, +0.098 S 1C-CTE S) ------------------------------------------------------------------------------------------------------------------------------------ 5 ESO286-G022 WFC3/UVI ACCUM UVIS2-C1K F336W FLASH=8 1 1471 S POS TARG 0, 0 S 1C-CTE (1471 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 ESO286-G022 WFC3/UVI ACCUM UVIS2-C1K F336W FLASH=8 1 1471 S POS TARG +0.092, +0.098 S 1C-CTE (1471 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 | ------------------------------------------------------------------------------------------------------------------------------------ ESO286-G022 1 WFC3/UVI ACCUM UVIS2-C1 F814W none none none none 1 N/A S K1C-CTE ESO286-G022 2 WFC3/UVI ACCUM UVIS2-C1 F814W none none none none 1 N/A S K1C-CTE ESO286-G022 3 WFC3/UVI ACCUM UVIS2-C1 F336W none none none none 1 N/A S K1C-CTE ESO286-G022 4 WFC3/UVI ACCUM UVIS2-C1 F814W none none none none 1 N/A S K1C-CTE ESO286-G022 5 WFC3/UVI ACCUM UVIS2-C1 F336W none none none none 2 N/A S K1C-CTE ESO286-G022 6 WFC3/UVI ACCUM UVIS2-C1 F336W none none none none 2 N/A S K1C-CTE 14210( 3) - 19-May-2016 09:58:04 - [ 5] Visit: 04 (SNL-2) Visit Requirements: On Hold Comments: Additional Comments: No roll-range restriction. Now using C1K1C-CTE window to place closer to amplifier and using small 3-point line-dither. 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 2MASXJ01414 WFC3/UVI ACCUM UVIS2-C1K F814W FLASH=5 1 334 S (334 POS TARG +0.185, +0.197 232-0735281 S 1C-CTE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 2MASXJ01414 WFC3/UVI ACCUM UVIS2-C1K F814W FLASH=5 1 334 S (334 POS TARG 0, 0 232-0735281 S 1C-CTE S) ------------------------------------------------------------------------------------------------------------------------------------ 3 2MASXJ01414 WFC3/UVI ACCUM UVIS2-C1K F390W 1 1424 S POS TARG +0.185, +0.197 232-0735281 S 1C-CTE (1424 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 2MASXJ01414 WFC3/UVI ACCUM UVIS2-C1K F814W FLASH=5 1 334 S (334 POS TARG +0.092, +0.098 232-0735281 S 1C-CTE S) ------------------------------------------------------------------------------------------------------------------------------------ 5 2MASXJ01414 WFC3/UVI ACCUM UVIS2-C1K F390W 1 1424 S POS TARG 0, 0 232-0735281 S 1C-CTE (1424 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 2MASXJ01414 WFC3/UVI ACCUM UVIS2-C1K F390W 1 1424 S POS TARG +0.092, +0.098 232-0735281 S 1C-CTE (1424 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 | ------------------------------------------------------------------------------------------------------------------------------------ 2MASXJ01414232-0735 1 WFC3/UVI ACCUM UVIS2-C1 F814W none none none none 1 N/A 281 S K1C-CTE 2MASXJ01414232-0735 2 WFC3/UVI ACCUM UVIS2-C1 F814W none none none none 1 N/A 281 S K1C-CTE 2MASXJ01414232-0735 3 WFC3/UVI ACCUM UVIS2-C1 F390W none none none none 1 N/A 281 S K1C-CTE 2MASXJ01414232-0735 4 WFC3/UVI ACCUM UVIS2-C1 F814W none none none none 1 N/A 281 S K1C-CTE 2MASXJ01414232-0735 5 WFC3/UVI ACCUM UVIS2-C1 F390W none none none none 2 N/A 281 S K1C-CTE 2MASXJ01414232-0735 6 WFC3/UVI ACCUM UVIS2-C1 F390W none none none none 2 N/A 281 S K1C-CTE 14210( 3) - 19-May-2016 09:58:04 - [ 6] Summary Form for Proposal 14210 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2-C1K1C-CTE ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=5, FLASH=8 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 0D TO 300 D, ORIENT 330D TO 359 D, POS TARG +0.092, +0.098, POS TARG +0.185, +0.197, POS TARG 0, 0 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F336W, F390W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names 2MASXJ01414232-0735281, ESO286-G022 ------------------------------------------------------------------------------------------------------------------------------------