7342( 4) - 04/15/99 17:44 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7342 Version: 4 Check-in Date: 15-Apr-1999 17:43:35 1.Proposal Title: The most powerful gravitational lens ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Richard Saunders Cavendish Laboratory CoI: Dr Joanne C. Baker Mullard Radio Astronomy Observatory N CoI: Dr Malcolm N. Bremer Leiden Observatory / Institute N d'Astrophysique de Paris CoI: Dr Garret Cotter Royal Greenwich Observatory Y CoI: Dr Michael Jones Mullard Radio Astronomy Observatory N CoI: Dr Steve Rawlings Oxford University N ------------------------------------------------------------------------------------ 5. Abstract We have recently detected a cosmic microwave background decrement towards the quasar pair PC1643+4631 A, B (z =3.79, 3.83, separation 198"). Following deep ground-based observations of this field, we have determined the decrement is likely to be a Sunyaev-Zel'dovich (S-Z) fluctuation caused by a cluster with mass >~ 10^15 M_SUN at a redshift z >~ 1. This is the first high-redshift structure to be detected by observations of the microwave background. Given the presence of such a massive structure at a large redshift along this BOX of sight, the images of the quasar pair must be gravitationally lensed to some degree. It is very probable that these are in fact two images of the same quasar, making this system the most powerful gravitational lens known. We seek to observe the vicinity of the quasars with WFPC2 to detect evidence for lensing. This information will allow us to constrain the mass of the S-Z-producing cluster which in turn will allow the first insight into massive clusters at z >~ 1. ------------------------------------------------------------------------------------ 7342( 4) - 04/15/99 17:44 - [ 2] Observations Description ------------------------ We plan to observe the field towards the quasar pair with WFPC2 using three pointings, each in a separate vist. For two of the pointing positions we will observe for 4000s in F555W and 6000s in F814W. For the third we will observe for 6000s in both F555W and F814W. With four 500-s non cr-split exposures per orbit, this scheme fills the 16 orbit allocation. To gain extra spatial resolution we use the canned dithering procedures. Generally we use the four point dither type box, except for the first orbit of visit 3, where we use dither type line to ensure that four 500-s exposures may will fit into one orbit. The first two visits have quite tight ORIENT constraints. This is caused by the need to avoid two bright stars near an important region of the cluster field (containing one of the background quasars) to be imaged in visit 2. Since the field observed in visit 1 is to be contiguous with the visit 2 field, visit 1 has similarly tight ORIENT constraints. If these ORIENT constraints prove to make scheduling very difficult, we may be able to calculate different ones, but if this is done the field centers will also need to be changed to compensate. Real Time Justification ----------------------- None Calibration Justification ------------------------- None Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Paper Products: YES Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7342( 4) - 04/15/99 17:44 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 GAL-CLUS- CLUSTER OF GALAXIES, RA=16H 44M 59.5S +/- 1", DEC=46D J2000 SURF(I) = 24.0+/-1.0 164459+46252 HIGH REDSHIFT CLUSTER, 25' 26" +/- 1", PLATE-ID=00TA 6 GRAVITATIONAL LENS 2 GAL-CLUS- CLUSTER OF GALAXIES, RA=16H 45M 16.5S +/- 1", DEC=46D J2000 SURF(I) = 24.0+/-1.0 164516+46252 HIGH REDSHIFT CLUSTER, 25' 24" +/- 1", PLATE-ID=00TA 5 GRAVITATIONAL LENS 3 GAL-CLUS- CLUSTER OF GALAXIES, RA=16H 45M 7.5S +/- 1.0", J2000 SURF(I) = 24.0+/-1.0 164507+46225 HIGH REDSHIFT CLUSTER, DEC=46D 22' 50" +/- 1.0", PLATE- 0 GRAVITATIONAL LENS ID=00TA Comments: There is also a POSS E = 13.6 mag star in this field which we have positioned close to the corner of the WF3 chip. 7342( 4) - 04/15/99 17:44 - [ 4] Visit: 01 Visit Priority: Visit Requirements: ORIENT 72D TO 74D On Hold Comments: Additional Comments: See observation description for discussion of ORIENT constraint Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 GAL-CLUS-16 WFPC2 IMAGE WF3-FIX F555W DITHER-TYPE=BOX 2 500 S NO SPLIT 4459+462526 ------------------------------------------------------------------------------------------------------------------------------------ 20 GAL-CLUS-16 WFPC2 IMAGE WF3-FIX F814W DITHER-TYPE=BOX 3 500 S NO SPLIT 4459+462526 ------------------------------------------------------------------------------------------------------------------------------------ 7342( 4) - 04/15/99 17:44 - [ 5] Visit: 02 Visit Priority: Visit Requirements: ORIENT 252D TO 254D On Hold Comments: Additional Comments: See observation description for discussion of ORIENT constraint Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 GAL-CLUS-16 WFPC2 IMAGE WF3-FIX F555W DITHER-TYPE=BOX 2 500 S NO SPLIT 4516+462525 ------------------------------------------------------------------------------------------------------------------------------------ 20 GAL-CLUS-16 WFPC2 IMAGE WF3-FIX F814W DITHER-TYPE=BOX 3 500 S NO SPLIT 4516+462525 ------------------------------------------------------------------------------------------------------------------------------------ 7342( 4) - 04/15/99 17:44 - [ 6] Visit: 03 Visit Priority: Visit Requirements: ORIENT 5D TO 20D 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 GAL-CLUS-16 WFPC2 IMAGE WF3-FIX F555W DITHER-TYPE=LINE 2 500 S NO SPLIT 4507+462250 ------------------------------------------------------------------------------------------------------------------------------------ 20 GAL-CLUS-16 WFPC2 IMAGE WF3-FIX F555W DITHER-TYPE=BOX 2 500 S NO SPLIT 4507+462250 ------------------------------------------------------------------------------------------------------------------------------------ 30 GAL-CLUS-16 WFPC2 IMAGE WF3-FIX F814W DITHER-TYPE=BOX 3 500 S NO SPLIT 4507+462250 ------------------------------------------------------------------------------------------------------------------------------------ 7342( 4) - 04/15/99 17:44 - [ 7] Summary Form for Proposal 7342 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WF3-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters DITHER-TYPE=BOX DITHER-TYPE=LINE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 72D TO 74D NO SPLIT ORIENT 252D TO 254D ORIENT 5D TO 20D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names GAL-CLUS-164459+462526 GAL-CLUS-164516+462525 GAL-CLUS-164507+462250 ------------------------------------------------------------------------------------------------------------------------------------