5965( 0) - 07/18/95 18:56 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5965 Version: ********** Check-in Date: ********** 1.Proposal Title: Towards H_o: relative astrometry of the lensing galaxy and the gravitationally lensed images in 0218+357 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Quasars GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Ian Browne NRAL Jodrell Bank CoI: Alok Patnaik MPIfR Bonn N CoI: Peter Wilkinson NRAL Jodrell Bank N CoI: Sunita Nair NRAL Jodrell Bank N CoI: Neal Jackson NRAL Jodrell Bank Y CoI: Elizabeth Corbett NRAL Jodrell Bank N ------------------------------------------------------------------------------------ 6. Abstract We propose an imaging observation of the smallest known gravitational lensed system 0218+357. This system is unique in having a well determined time delay between the two lensed images and a simple lensing geometry. The redshift of the lensing galaxy is known although the redshift of the lensed object has yet to be determined. Almost all the ingredients necessary for an accurate determination of the Hubble Constant are therefore available for this object. To achieve this it is important to eliminate as many sources of uncertainty as possible; a major source of error can be removed by better constraints on the position and orientation of the lensing galaxy relative to the lensed images. This is impossible to do from the ground due to the 0.335 arcsec separation of the lensed images and consequent difficulty in disentangling the emission from the images from that of the lensing galaxy. We propose a brief HST imaging observation which will allow us to do this. ------------------------------------------------------------------------------------ 5965( 0) - 07/18/95 18:56 - [ 2] Observations Description ------------------------ The observations are aimed at detecting and imaging an extended galaxy with integrated magnitudes in V down to about 20 to 21. In the 555 filter this will produce about 2 electrons per second in the central pixel assuming a redshift of 0.6847 and using the curve of figure 6.1. in the WFPC2 handbook. The figures for the 814 filter are roughly similar. We propose to take two exposures in each filter: one short (so as not to saturate on the point sources) and one long in order to search for any lensing galaxy. The available observing time per orbit is 42 minutes, taking into account occultation and guide star acquisition. Allowing 16 minutes for exposure overheads (one CR-SPLIT and one NO-CR-SPLIT in each filter) this gives 26 minutes for science exposures. In the deeper exposure in each filter we will therefore obtain about 12-15 minutes integration. This will be enough to collect 1400 electrons in the central pixel of the lensing galaxy. The point sources will be easily detected in the short (~1 min) exposures. Real Time Justification ----------------------- We are actively trying to obtain a redshift for the lensed object in 0218+357 using observations with the WHT. Another group has Palomar 5m data and is aiming to obtain Keck data. VLBI images of the source have been obtained at two frequencies (Patnaik et al, 1994, Compact Extragalactic Radio Sources, eds Kellermann & Zensus). Meanwhile more radio monitoring data have been collected and the delay determination is being refined. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: __Diagnostic-Sum-Section__ Software-Version (Contro, ------------------------------------------------------------------------------------ 5965( 0) - 07/18/95 18:56 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 QSO- GALAXY RA=2H 21M 5.47S +/- 0.01S, J2000 R=19.5 022105+35561 DEC=35D 56' 13.7" +/- 0.1" 3 5965( 0) - 07/18/95 18:56 - [ 4] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 QSO- WFPC2 IMAGE PC1 F555W 1 60S SEQ 1-3 NON-INT 022105+3556 13 ------------------------------------------------------------------------------------------------------------------------------------ 2 QSO- WFPC2 IMAGE PC1 F555W 1 1000S 022105+3556 13 ------------------------------------------------------------------------------------------------------------------------------------ 3 QSO- WFPC2 IMAGE PC1 F814W 1 1000S 022105+3556 13 ------------------------------------------------------------------------------------------------------------------------------------ 5965( 0) - 07/18/95 18:56 - [ 5] Summary Form for Proposal 5965 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Quasars ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SEQ 1-3 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names QSO-022105+355613 ------------------------------------------------------------------------------------------------------------------------------------