6109( 6) - 02/29/96 09:54 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6109 Version: 6 Check-in Date: 29-Feb-1996 09:51:36 1.Proposal Title: Spectropolarimetry of Low Red-Shift Quasars - Test of the Emission Mechanism ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Quasars GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Anuradha Koratkar Space Telescope Science Institute CoI: Robert Antonucci University of California, Santa Barbara N CoI: Anne Kinney Space Telescope Science Institute N CoI: Bob Goodrich Space Telescope Science Institute N ------------------------------------------------------------------------------------ 6. Abstract The Lyman limit region may be the most important part of the quasar spectrum. Models of accretion disks make predictions about the polarization and the discontinuity at the Lyman limit. Scattering of UV emission in the disk atmospheres results in strong polarization and the polarization vector should be perpendicular to the radio jets. According to Laor, Netzer and Piran, the disk radiation is significantly polarized for Lambda > 912 Angstrom and polarization is quenched for Lambda <912 Angstrom, even if the Lyman edges are weak or absent in the total flux. We have a list of candidates whose IUE spectra seem to show signatures of simple thin disks, i.e. broad partial Lyman absorption edges at the systemic redshifts. Previous observations of 3 quasars from this list show the opposite behaviour. The polarization magnitude is upto 20 percent below the edge. Therefore, we propose to use the FOS to observe 2 low red-shift ~1.5 quasars from below the Lyman limit to LyAlpha with moderate resolution and signal-to-noise ratio of ~90 to determine the amount of polarization. These observations will be used to investigate the nature of the Lyman edges and any associated Lyman absorption lines. The results will provide critical constraints and help in the development of thermal models. ------------------------------------------------------------------------------------ 6109( 6) - 02/29/96 09:54 - [ 2] Observations Description ------------------------ To achieve our goal we will observe the objects to cover the spectral region from ~ 200Angstrom (observed frame) below the Lyman limit to slightly above the LyAlpha line with the 1.0" aperture. We wish to compare the polarization above and below the Lyman edge. We are quite likely to succeed if we require polarization errors of 1 percent in 200 Angstom bins; much larger errors would produce results which are not very strong. For exposure time calculations the input fluxes for both the short wavelength and the long wavelength side of the Lyman edge are from the IUE spectra. The exposure time calculations have been calculated with the STScI FOS simulator. To adapt the simulator to the case of polarimetry, three factors must be considered: 1) The fractional error in polarization (here, 0.01 per 200Angstrom bin) must include the standard factor of root 2 because Q and U are measured separately. 2) The expected count rate for spectroscopy must be multiplied by 0.5 because one ray is discarded by the analyzer, and by the wavelength dependent transmission (T= 0.35 - 0.8). 3) The error is boosted by a factor of modulation efficiency (eta^- 1). Eta is moderately wavelength dependent and must be considered separately for each object. Typical values for this program are 0.8 - 0.9. Therefore, we require that the simulator produce a minimum of (.01)^-2*2*(1/T)* (1/.5)timesEta^-1 counts per 200Angstrom bin, and that is the basis of our table. \\medskip begintabularllllllll Object & Redshift & Lambda & ave flux & ave flux & grating & time & , & & of edge &>912 Angstrom & <912 Angstrom & & (sec) & , 0117+213 & 1.493 & 2274 & 3e-15 & 1e- 15 &RED G190H & 9000 & , & & & & &RED G270H & 3960& , 0743- 673 & 1.512 & 2291 & 6e-15 & 3e-15 &RED G190H & 4500 & , & & & & &RED G270H & 1800& , endtabular \\medskip We will acquire the targets using ACQ/BINARY and the FOS/RED detector. The above exposure times and the target acquisition strategy will require a total of 10 orbits. These orbits will be distributed as follows: 0117+213 will require 7 orbits (5 orbits for the G190H, and 2 orbits for the G270H) and 0743-67 will require 3 orbits (2 orbits for the G190H and 1 orbit for the G270H). Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- The standard Institute RSDP reduction of FOS data is quite sufficient for our purposes. We will analyze the reduced data at the Institute and UC Santa Barbara using IDL and STSDAS programs, and the spectropolarimetry routines we have developed in the course of our optical and HST work. The reduction and measurement are more complicated than for spectroscopy, but are still straightforward. We use sum and difference spectra from the four waveplate positions to get the Stokes spectra Q and U. These can then be combined for magnitude and position angle of polarization. As explained in the Description of Observations, the first thing we will do is determine these parameters for 200 Angstrom bins above and below the Lyman edge. A little care is needed with the non-Gaussian error distributions of the latter parameters. ------------------------------------------------------------------------------------ 6109( 6) - 02/29/96 09:54 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6109( 6) - 02/29/96 09:54 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 0117+213 GALAXY, QUASAR RA=01H 20M 17.26S +/- 1S, J2000 Z=1.493 F(2000)=1+/-0.5e-15 DEC=+21D 33' 46.4" +/- 1", PLATE F(2500)=3+/-1e-15 -ID=021K Comments: Lyman edge at 2274 angstrom Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1982.890 0.0 0.0 0.0 2 0743-673 GALAXY, QUASAR RA=07H 43M 31.69S +/- 1S, DEC=- J2000 Z=1.512 F(2000)=3+/-0.5e-15 67D 26' 25.1" +/- 1", PLATE- F(2500)=6+/-1e-15 ID=01YR Comments: Lyman edge at 2291 angstrom Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1978.105 0.0 0.0 0.0 6109( 6) - 02/29/96 09:54 - [ 5] 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 0117+213 FOS/BL ACQ/BIN 4.3 MIRROR 1 20S ONBOARD ACQ FOR 2-8 ARY ------------------------------------------------------------------------------------------------------------------------------------ 2 0117+213 FOS/BL ACCUM 1.0 G270H POLSCAN=4B 1 1100S MAX DUR 200% END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 3 0117+213 FOS/BL ACCUM 1.0 G270H POLSCAN=4B 1 2000S MAX DUR 200% END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 4 0117+213 FOS/BL ACCUM 1.0 G190H POLSCAN=4B 1 2100S MAX DUR 200% END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 5 0117+213 FOS/BL ACCUM 1.0 G190H POLSCAN=4B 1 2120S MAX DUR 200% END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 6 0117+213 FOS/BL ACCUM 1.0 G190H POLSCAN=4B 1 2100S MAX DUR 200% END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 7 0117+213 FOS/BL ACCUM 1.0 G190H POLSCAN=4B 1 2120S MAX DUR 200% END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 8 0117+213 FOS/BL ACCUM 1.0 G190H POLSCAN=4B 1 2060S MAX DUR 200% END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 6109( 6) - 02/29/96 09:54 - [ 6] Visit: 02 Visit Requirements: CVZ 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 0743-673 FOS/BL ACQ/BIN 4.3 MIRROR 1 20S ONBOARD ACQ FOR 2-3 ARY ------------------------------------------------------------------------------------------------------------------------------------ 2 0743-673 FOS/BL ACCUM 1.0 G190H POLSCAN=8B 1 8693S ------------------------------------------------------------------------------------------------------------------------------------ 3 0743-673 FOS/BL ACCUM 1.0 G270H POLSCAN=8B 1 4420S ------------------------------------------------------------------------------------------------------------------------------------ 6109( 6) - 02/29/96 09:54 - [ 7] Summary Form for Proposal 6109 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/BINARY ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters POLSCAN=4B POLSCAN=8B ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Quasars ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2-8 MAX DUR 200% END ORBIT CVZ ONBOARD ACQ FOR 2-3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G270H G190H ------------------------------------------------------------------------------------------------------------------------------------ Target Names 0117+213 0743-673 ------------------------------------------------------------------------------------------------------------------------------------