6156( 0) - 07/18/95 20:18 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6156 Version: ********** Check-in Date: ********** 1.Proposal Title: Is the intergalactic HeII absorption in PKS 1935-692 and Q0302-003 truly different? ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Quasars GO/DD 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Peter Jakobsen Astrophysics Division, ESA/ESTEC CoI: David Tytler University of California, San Diego N ------------------------------------------------------------------------------------ 6. Abstract Follow-up FOC far-UV objective prism observations of the second example of a ``clear'' high redshift quasar ever to be discovered, the z=3.18 object PKS 1935- 692 will be made. An earlier FOS observation of this object suggests that PKS 1935- 692 displays considerably less intense intergalactic helium foreground absorption than that previously detected in the FOC prism spectrum of Q0302-003 at z=3.29. This implies that the helium opacity may be patchy at z~3 and that universe was in the process of becoming re- ionized in helium at that late epoch. The objective of the proposed observation is to verify this important finding by exploiting the superior background monitoring and subtraction afforded by the two dimensional FOC detector and enable a clean and unambiguous comparison of the HeII absorption in PKS 1935-692 and Q0302-003 to be made. ------------------------------------------------------------------------------------ 6156( 0) - 07/18/95 20:18 - [ 2] Observations Description ------------------------ Based on our considerable experience with the FOC far-UV prism, we have developed a simple, but effective, observing strategy that involves limiting individual FOC prism exposures of faint targets to about 20 minute duration and co-adding the individually reduced exposures. Aside from enabling variations in the the particle and sky background to be dealt with in an optimal manner, this technique also has the important benefit of allowing the individual sub- spectra to be shifted slightly on the FOC detector through offset pointing (by a few tenths of an arcsecond) in order to eliminate residual flat-field effects in the resulting combined spectrum. Assuming a visibility of 59 minutes for PKS 1935-692, it follows that two 20-25 minute sub- exposures are achievable per orbit and that a total of 5 orbits are required to reach the desired total exposure time of 1.5 * 10^4 s. All exposures are blind ``point and shoot'' (Mode III) and no special calibration exposures are required beyond routine Cycle 5 calibrations. Real Time Justification ----------------------- None None Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6156( 0) - 07/18/95 20:18 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 Q1935-692 GALAXY, QUASAR RA = 19H 40M 25.56S +/- 0.1S, J2000 Z=3.152 V = 18.8 +/- 0.5 DEC = -69D 07' 56.5" +/- 1", PLATE-ID=01CB 6156( 0) - 07/18/95 20:18 - [ 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 Q1935-692 FOC/96 IMAGE 512x512 PRISM1 1150- 1 1100S POS TARG +0.0,-4.9 6000 ------------------------------------------------------------------------------------------------------------------------------------ 2 Q1935-692 FOC/96 IMAGE 512x512 PRISM1 1150- 1 1100S POS TARG -0.2,-4.9 6000 ------------------------------------------------------------------------------------------------------------------------------------ 3 Q1935-692 FOC/96 IMAGE 512x512 PRISM1 1150- 1 1400S POS TARG +0.2,-4.9 6000 ------------------------------------------------------------------------------------------------------------------------------------ 4 Q1935-692 FOC/96 IMAGE 512x512 PRISM1 1150- 1 1400S POS TARG +0.2,-4.7 6000 ------------------------------------------------------------------------------------------------------------------------------------ 5 Q1935-692 FOC/96 IMAGE 512x512 PRISM1 1150- 1 1400S POS TARG +0.0,-4.7 6000 ------------------------------------------------------------------------------------------------------------------------------------ 6 Q1935-692 FOC/96 IMAGE 512x512 PRISM1 1150- 1 1400S POS TARG -0.2,-4.7 6000 ------------------------------------------------------------------------------------------------------------------------------------ 7 Q1935-692 FOC/96 IMAGE 512x512 PRISM1 1150- 1 1400S POS TARG -0.2,-5.1 6000 ------------------------------------------------------------------------------------------------------------------------------------ 8 Q1935-692 FOC/96 IMAGE 512x512 PRISM1 1150- 1 1400S POS TARG +0.0,-5.1 6000 ------------------------------------------------------------------------------------------------------------------------------------ 9 Q1935-692 FOC/96 IMAGE 512x512 PRISM1 1150- 1 1400S POS TARG +0.2,-5.1 6000 ------------------------------------------------------------------------------------------------------------------------------------ 10 Q1935-692 FOC/96 IMAGE 512x512 PRISM1 1150- 1 1400S POS TARG +0.1,-4.9 6000 ------------------------------------------------------------------------------------------------------------------------------------ 6156( 0) - 07/18/95 20:18 - [ 5] Summary Form for Proposal 6156 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOC/96 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO/DD ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Quasars ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements POS TARG +0.0,-4.9 POS TARG -0.2,-4.9 POS TARG +0.2,-4.9 POS TARG +0.2,-4.7 POS TARG +0.0,-4.7 POS TARG -0.2,-4.7 POS TARG -0.2,-5.1 POS TARG +0.0,-5.1 POS TARG +0.2,-5.1 POS TARG +0.1,-4.9 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements PRISM1 ------------------------------------------------------------------------------------------------------------------------------------ Target Names Q1935-692 ------------------------------------------------------------------------------------------------------------------------------------