! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6560,v 5.1 1996/06/10 17:41:10 pepsa Exp $ Proposal_Information Title: Mapping an optical Einstein ring Proposal_Category: GO Scientific_Category: COSMOLOGY Cycle: 6 Investigators PI_name: Dr. S. J. Warren PI_Institution: Imperial College of Science Technology and Medicine CoI_Name: Dr. P. C. Hewett CoI_Institution: Institute of Astronomy Contact: CoI_Name: Dr. P. Moller CoI_Institution: Space Telescope Science Institute Contact: CoI_Name: Dr. G. F. Lewis CoI_Institution: Institute of Astronomy Contact: Abstract: Observations of gravitationally lensed Einstein-ring images provide a dramatic improvement in our ability to constrain the properties of lensing mass distributions and the structure in the extended sources. The rings are so effective, relative to the more common multiply-imaged point sources, because of the constraints provided by the two-dimensional surface brightness maps obtained from high-resolution imaging. The first five known rings were discovered in radio surveys and are all very faint optically. The first optically bright ring, recently discovered spectroscopically and confirmed by imaging, is clearly a prime target for HST imaging. Here we propose a WFPC2 image through the F555W filter to provide a resolved surface-brightness map of the ring and the lensing galaxy. The lens is an early-type galaxy at z=0.485, and the source is an emission-line galaxy at z=3.591. The goal of these observations is twofold: a) to measure the radial profile of the mass-to-light ratio of the lensing galaxy, and b) to determine the structure of the background high-redshift galaxy, at a resolution of 0.2 arcsec. Questions Observing_Description: Four orbits broad band V imaging of the same target, comprising eight dithered images. Real_Time_Justification: Calibration_Justification: Additional_Comments: Our original request was for 16 orbits with the F547M filter, which is optimal for imaging the ring itself. Instead we were awarded only 4 orbits to obtain the surface brightness profile of the lensing galaxy. This is better achieved with the broader F555W filter, which we have therefore selected. Fixed_Targets Target_Number: 1 Target_Name: GAL-004942-275226 Alternate_Names: Description: GALAXY,ELLIPTICAL,GRAVITATIONAL LENS,EINSTEIN RING, Position: RA=0H 49M 41.80S +/- 0.10S,DEC=-27D 52' 26.0" +/- 1.0", PLATE-ID=025A Equinox: J2000 RV_or_Z: Z=0.485 RA_PM: 0.0 Dec_PM: 0.0 Epoch: Annual_Parallax: 0.0 Flux: V=20.4 B-V=1.5 Comments: Solar_System_Targets Generic_Targets Scan_Data Visits Visit_Number: 1 Visit_Requirements: ORIENT 45.0D TO 90.0D On_Hold_Comments: Visit_Comments: The purpose of the orientation requirement is to image a second galaxy in WF3. The position of this second galaxy relative to the target galaxy is distance 58 arcsec, and position angle 201 deg. With this range of orientation the second galaxy image should not be affected by charge bleeding or diffraction spikes from a bright star that will also lie in WF3. Exposure_Number: 1 Target_Name: GAL-004942-275226 Config: WFPC2 Opmode: IMAGE Aperture: WF4-FIX Sp_Element: F555W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 1200.00S Special_Requirements: Comments: Exposure_Number: 2 Target_Name: GAL-004942-275226 Config: WFPC2 Opmode: IMAGE Aperture: WF4-FIX Sp_Element: F555W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 1200.00S Special_Requirements: Comments: Exposure_Number: 3 Target_Name: GAL-004942-275226 Config: WFPC2 Opmode: IMAGE Aperture: WF4-FIX Sp_Element: F555W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 1200.00S Special_Requirements: POS TARG +0.5,+0.25 Comments: Exposure_Number: 4 Target_Name: GAL-004942-275226 Config: WFPC2 Opmode: IMAGE Aperture: WF4-FIX Sp_Element: F555W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 1200.00S Special_Requirements: POS TARG +0.5,+0.25 Comments: Exposure_Number: 5 Target_Name: GAL-004942-275226 Config: WFPC2 Opmode: IMAGE Aperture: WF4-FIX Sp_Element: F555W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 1200.00S Special_Requirements: POS TARG +0.75,+0.75 Comments: Exposure_Number: 6 Target_Name: GAL-004942-275226 Config: WFPC2 Opmode: IMAGE Aperture: WF4-FIX Sp_Element: F555W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 1200.00S Special_Requirements: POS TARG +0.75,+0.75 Comments: Exposure_Number: 7 Target_Name: GAL-004942-275226 Config: WFPC2 Opmode: IMAGE Aperture: WF4-FIX Sp_Element: F555W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 1200.00S Special_Requirements: POS TARG +0.25,+0.5 Comments: Exposure_Number: 8 Target_Name: GAL-004942-275226 Config: WFPC2 Opmode: IMAGE Aperture: WF4-FIX Sp_Element: F555W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 1200.00S Special_Requirements: POS TARG +0.25,+0.5 Comments: Data_Distribution Medium: 8MM Blocking_Factor: 10 Ship_To: PI_Address Ship_Via: UPS Recipient_Email: