9450( 3) - 03/14/02 12:02 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9450 Version: 3 Check-in Date: 14-Mar-2002 12:01:14 1.Proposal Title: The lensing galaxy of JVAS B0218+357: determination of H_0 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 11 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Neal Jackson University of Manchester CoI: Ms Jessica Skelton University of Manchester, Jodrell Bank N Observatory CoI: Mr Olaf Wucknitz Hamburger Sternwarte N CoI: Dr Ian Browne University of Manchester, Jodrell Bank N Observatory CoI: Prof Peter Wilkinson University of Manchester, Jodrell Bank N Observatory CoI: Dr Andy Biggs University of Manchester, Jodrell Bank N Observatory CoI: Dr Leon Koopmans California Institute of Technology N CoI: Prof Roger Blandford California Institute of Technology N CoI: Dr Chris Fassnacht Space Telescope Science Institute N ------------------------------------------------------------------------------------ 5. Abstract Much effort has been devoted to estimating Hubble's constant H_0 using observations of very nearby objects. Gravitational lensing time delays offer potentially the most accurate method for determining H_0 using observations on cosmological scales; it is a very clean method in that little complicated astrophysics is involved, and it is a single--step method compared to the traditional multi--step distance ladder. The major problem with most such determinations in the past has been systematic errors due to uncertainties in the lens mass model, leading to 20 Einstein-ring lens system, is the one system for which these systematic uncertainties can be reduced very substantially, and in particular is unique in that the modelling systematics can be reduced to the level of the uncertainties in the measurement of the time delay. The only requirement left is to be able accurately to locate the centre of the lensing galaxy. We propose an extremely deep ACS image in I-band of this system for this purpose; the prize is a robust 5 (lens mass model). We have conducted simulations to estimate the necessary S:N ratio in an ACS observation in order to be able to achieve a successful deconvolution of the lens galaxy and lensed images with the required accuracy. ------------------------------------------------------------------------------------ 9450( 3) - 03/14/02 12:02 - [ 2] Observations Description ------------------------ The simulations which lead to the exposure time estimate have been described in some detail in the scientific case. Essentially, 50ks is the minimum, and 80ks gives good deconvolution of the lensed images to allow for a sufficiently accurate (10mas) positional fix on the lensing galaxy to reduce the errors on H_0 below 10 simulations have erred on the side of pessimism, as we have done the deconvolution trials with an artificial PSF and used an empirical one for the simulation. However, any further reduction in the error below 10mas will reduce the error correspondingly in H_0, since the time delay error and the systematic errors introduced by the model are both in the region of 3-5 Why the HRC rather than the WFC? The V+AB_Nu value for the brighter point source is 19.7. Using the ACS handbook and assuming 6-minute integration times, the WFC is just outside saturation. However, the point sources are variable, and any brightening or above-nominal sensitivity in the WFC will cause saturation at this exposure time, and irrevocably damage the program which requires accurate deconvolution of the brighter image and its PSF. Below 6- minute exposures we incur the buffer-dump overhead in the WFC, which makes this instrument less efficient than the HRC despite its 2* greater sensitivity. The HRC also allows uncomplicated achievement of full resolution at 814nm For the HRC we expect about 2500s of useful integration per orbit, allowing for 6 min of acquisition and the remainder of the orbit for exposure setup time, and hence need 32 orbits for the primary target. 4 orbits will be spent on building up a PSF of a standard star. Here we propose to use the same principle as McLure et al. (2000), and take a range of different exposure times to gain good signal-to- noise in the PSF wing with the long exposures and information on the PSF centre with the short ones. The four orbits will both allow us to obtain good S:N and check for any temporal variation in the instrumental PSF. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9450( 3) - 03/14/02 12:02 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 CLASS0218+35 GALAXY, Gravitational RA=02H 21M 5.48S +/- 0.01S, J2000 Z=0.96 V = 21.0+/-0.5 7 Lens, Einstein Ring DEC=35D 56' 13.7" +/- 0.1" B-V = 1.0+/-0.3 V-I = 1.8+/-0.2 Coordinate Source: OTHER_SOURCE 2 PSF1-CALIB STAR, M V-IV RA=00H 54M 16.06S +/- 0.1S, J2000 V = 13.82+/-0.1 DEC=00D 39' 54.3" +/- 1.0" V-I = 1.84+/-0.1 Coordinate Source: GUIDE_STAR_CATALOG 3 PSF2-CALIB STAR, M V-IV RA=02H 33M 45.53S +/- 0.1S, J2000 V = 14.74+/-0.1 DEC=05D 17' 33.6" +/- 1.0", V-I = 1.95+/-0.1 PLATE-ID=04YH Coordinate Source: GUIDE_STAR_CATALOG 9450( 3) - 03/14/02 12:02 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.265 Coordinate_Frame POS-TARG Pattern_Orient 20.67 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.265 Coordinate_Frame POS-TARG Pattern_Orient 20.67 Center_Pattern YES ------------------------------------------------------------------------------------------------------------------------------------ 9450( 3) - 03/14/02 12:02 - [ 5] Visit: 01 Visit Priority: 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 PSF1-CALIB ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 0.5 S PATTERN 1 1 C ------------------------------------------------------------------------------------------------------------------------------------ 2 PSF1-CALIB ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 0.5 S PATTERN 2 2 C ------------------------------------------------------------------------------------------------------------------------------------ 3 PSF1-CALIB ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 8.0 S PATTERN 1 3 C ------------------------------------------------------------------------------------------------------------------------------------ 4 PSF1-CALIB ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 8.0 S PATTERN 2 4 C ------------------------------------------------------------------------------------------------------------------------------------ 6 PSF1-CALIB ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S C ------------------------------------------------------------------------------------------------------------------------------------ 9450( 3) - 03/14/02 12:02 - [ 6] Visit: 02 Visit Priority: 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 PSF2-CALIB ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 0.5 S PATTERN 1 10 C ------------------------------------------------------------------------------------------------------------------------------------ 11 PSF2-CALIB ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 0.5 S PATTERN 2 11 C ------------------------------------------------------------------------------------------------------------------------------------ 12 PSF2-CALIB ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 8.0 S PATTERN 1 12 C ------------------------------------------------------------------------------------------------------------------------------------ 13 PSF2-CALIB ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 8.0 S PATTERN 2 13 C ------------------------------------------------------------------------------------------------------------------------------------ 14 PSF2-CALIB ACS/WF ACCUM WFC F814W CR-SPLIT=2 1 100.0 S PATTERN 1 14 C ------------------------------------------------------------------------------------------------------------------------------------ 9450( 3) - 03/14/02 12:02 - [ 7] Visit: 10 Visit Priority: 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 ------------------------------------------------------------------------------------------------------------------------------------ 50 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 1 50 57 C ------------------------------------------------------------------------------------------------------------------------------------ 51 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 2 51 57 C ------------------------------------------------------------------------------------------------------------------------------------ 52 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 1 52 57 C ------------------------------------------------------------------------------------------------------------------------------------ 53 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 2 53 57 C ------------------------------------------------------------------------------------------------------------------------------------ 54 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 1 54 57 C ------------------------------------------------------------------------------------------------------------------------------------ 9450( 3) - 03/14/02 12:02 - [ 8] Visit: 11 Visit Priority: 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 ------------------------------------------------------------------------------------------------------------------------------------ 55 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 2 55 57 C ------------------------------------------------------------------------------------------------------------------------------------ 56 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 1 56 57 C ------------------------------------------------------------------------------------------------------------------------------------ 57 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 2 57 57 C ------------------------------------------------------------------------------------------------------------------------------------ 58 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 1 58 57 C ------------------------------------------------------------------------------------------------------------------------------------ 59 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 2 59 57 C ------------------------------------------------------------------------------------------------------------------------------------ 9450( 3) - 03/14/02 12:02 - [ 9] Visit: 12 Visit Priority: 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 ------------------------------------------------------------------------------------------------------------------------------------ 60 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 1 60 57 C ------------------------------------------------------------------------------------------------------------------------------------ 61 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 2 61 57 C ------------------------------------------------------------------------------------------------------------------------------------ 62 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 1 62 57 C ------------------------------------------------------------------------------------------------------------------------------------ 63 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 2 63 57 C ------------------------------------------------------------------------------------------------------------------------------------ 64 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 1 64 57 C ------------------------------------------------------------------------------------------------------------------------------------ 9450( 3) - 03/14/02 12:02 - [ 10] Visit: 13 Visit Priority: 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 ------------------------------------------------------------------------------------------------------------------------------------ 65 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 2 65 57 C ------------------------------------------------------------------------------------------------------------------------------------ 66 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 1 66 57 C ------------------------------------------------------------------------------------------------------------------------------------ 67 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 2 67 57 C ------------------------------------------------------------------------------------------------------------------------------------ 68 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 1 68 57 C ------------------------------------------------------------------------------------------------------------------------------------ 69 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 2 69 57 C ------------------------------------------------------------------------------------------------------------------------------------ 9450( 3) - 03/14/02 12:02 - [ 11] Visit: 14 Visit Priority: 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 ------------------------------------------------------------------------------------------------------------------------------------ 70 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 1 70 57 C ------------------------------------------------------------------------------------------------------------------------------------ 71 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 2 71 57 C ------------------------------------------------------------------------------------------------------------------------------------ 72 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 1 72 57 C ------------------------------------------------------------------------------------------------------------------------------------ 73 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 2 73 57 C ------------------------------------------------------------------------------------------------------------------------------------ 74 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 1 74 57 C ------------------------------------------------------------------------------------------------------------------------------------ 9450( 3) - 03/14/02 12:02 - [ 12] Visit: 15 Visit Priority: 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 ------------------------------------------------------------------------------------------------------------------------------------ 75 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 2 75 57 C ------------------------------------------------------------------------------------------------------------------------------------ 76 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 1 76 57 C ------------------------------------------------------------------------------------------------------------------------------------ 77 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 2 77 57 C ------------------------------------------------------------------------------------------------------------------------------------ 78 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 1 78 57 C ------------------------------------------------------------------------------------------------------------------------------------ 79 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 2 79 57 C ------------------------------------------------------------------------------------------------------------------------------------ 9450( 3) - 03/14/02 12:02 - [ 13] Visit: 16 Visit Priority: 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 ------------------------------------------------------------------------------------------------------------------------------------ 80 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 1 80 57 C ------------------------------------------------------------------------------------------------------------------------------------ 81 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 2 81 57 C ------------------------------------------------------------------------------------------------------------------------------------ 82 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=NO 1 360 S PATTERN 1 82 57 C ------------------------------------------------------------------------------------------------------------------------------------ 83 CLASS0218+3 ACS/WF ACCUM WFC F814W CR-SPLIT=2 1 150 S PATTERN 1 83 57 C ------------------------------------------------------------------------------------------------------------------------------------ 9450( 3) - 03/14/02 12:02 - [ 14] Summary Form for Proposal 9450 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO CR-SPLIT=2 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1 PATTERN 2 2 PATTERN 1 3 PATTERN 2 4 PATTERN 1 10 PATTERN 2 11 PATTERN 1 12 PATTERN 2 13 PATTERN 1 14 PATTERN 1 50 PATTERN 2 51 PATTERN 1 52 PATTERN 2 53 PATTERN 1 54 PATTERN 2 55 PATTERN 1 56 PATTERN 2 57 PATTERN 1 58 PATTERN 2 59 PATTERN 1 60 PATTERN 2 61 PATTERN 1 62 PATTERN 2 63 PATTERN 1 64 PATTERN 2 65 PATTERN 1 66 PATTERN 2 67 PATTERN 1 68 PATTERN 2 69 PATTERN 1 70 PATTERN 2 71 PATTERN 1 72 PATTERN 2 73 PATTERN 1 74 PATTERN 2 75 PATTERN 1 76 PATTERN 2 77 PATTERN 1 78 PATTERN 2 79 PATTERN 1 80 PATTERN 2 81 PATTERN 1 82 PATTERN 1 83 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names PSF1-CALIB PSF2-CALIB CLASS0218+357 ------------------------------------------------------------------------------------------------------------------------------------