! Cycle 5 HST proposal 6109 Proposal_Information Title: Spectropolarimetry of Low Red-Shift Quasars - Test of the Emission Mechanism Proposal_Category: GO Scientific_Category: Quasars Cycle: 5 Investigators PI_name: Anuradha Koratkar PI_Institution: Space Telescope Science Institute CoI_Name: Robert Antonucci CoI_Institution: University of California, Santa Barbara Contact: ! Y or N (designate at most one contact) CoI_Name: Anne Kinney CoI_Institution: Space Telescope Science Institute Contact: ! Y or N (designate at most one contact) CoI_Name: Bob Goodrich CoI_Institution: Space Telescope Science Institute Contact: Abstract: ! Free format text (please update) 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. Questions ! Free format text (please update) Observing_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. Fixed_Targets ! Section 5.1 Target_Number: 1 Target_Name: 0117+213 Alternate_Names: Description: GALAXY, QUASAR Position: RA=01H 20M 17.26S +/- 1S, DEC=+21D 33' 46.4" +/- 1", PLATE-ID=021K Equinox: J2000 Epoch: 1982.890 RV_or_Z: Z=1.493 Flux: F(2000)= 1+/-0.5 e-15 F(2500)= 3+/-1 e-15 Comments: Lyman edge at 2274 angstrom Target_Number: 2 Target_Name: 0743-673 Alternate_Names: Description: GALAXY, QUASAR Position: RA=07H 43M 31.69S +/- 1S, DEC=-67D 26' 25.1" +/- 1", PLATE-ID=01YR Equinox: J2000 Epoch: 1978.105 RV_or_Z: Z=1.512 Flux: F(2000)= 3+/-0.5 e-15 F(2500)= 6+/-1 e-15 Comments: Lyman edge at 2291 angstrom Visits ! Section 6 Visit_Number: 1 Visit_Requirements: On_Hold_Comments: Visit_Comments: Exposure_Number: 1 ! Section 6.5 Target_Name: 0117+213 Config: FOS/BL Opmode: ACQ/BINARY Aperture: 4.3 Sp_Element: MIRROR Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 20S Special_Requirements: ONBOARD ACQ FOR 2-8 Exposure_Number: 2 Target_Name: 0117+213 Config: FOS/BL Opmode: ACCUM Aperture: 1.0 Sp_Element: G270H Wavelength: Optional_Parameters: POLSCAN=4B Number_of_Iterations: 1 Time_Per_Exposure: 1100S Special_Requirements: MAX DUR 200% END ORBIT Exposure_Number: 3 Target_Name: 0117+213 Config: FOS/BL Opmode: ACCUM Aperture: 1.0 Sp_Element: G270H Wavelength: Optional_Parameters: POLSCAN=4B Number_of_Iterations: 1 Time_Per_Exposure: 2000S Special_Requirements: MAX DUR 200% END ORBIT Exposure_Number: 4 Target_Name: 0117+213 Config: FOS/BL Opmode: ACCUM Aperture: 1.0 Sp_Element: G190H Wavelength: Optional_Parameters: POLSCAN=4B Number_of_Iterations: 1 Time_Per_Exposure: 2100S Special_Requirements: MAX DUR 200% END ORBIT Exposure_Number: 5 Target_Name: 0117+213 Config: FOS/BL Opmode: ACCUM Aperture: 1.0 Sp_Element: G190H Wavelength: Optional_Parameters: POLSCAN=4B Number_of_Iterations: 1 Time_Per_Exposure: 2120S Special_Requirements: MAX DUR 200% END ORBIT Exposure_Number: 6 Target_Name: 0117+213 Config: FOS/BL Opmode: ACCUM Aperture: 1.0 Sp_Element: G190H Wavelength: Optional_Parameters: POLSCAN=4B Number_of_Iterations: 1 Time_Per_Exposure: 2100S Special_Requirements: MAX DUR 200% END ORBIT Exposure_Number: 7 Target_Name: 0117+213 Config: FOS/BL Opmode: ACCUM Aperture: 1.0 Sp_Element: G190H Wavelength: Optional_Parameters: POLSCAN=4B Number_of_Iterations: 1 Time_Per_Exposure: 2120S Special_Requirements: MAX DUR 200% END ORBIT Exposure_Number: 8 Target_Name: 0117+213 Config: FOS/BL Opmode: ACCUM Aperture: 1.0 Sp_Element: G190H Wavelength: Optional_Parameters: POLSCAN=4B Number_of_Iterations: 1 Time_Per_Exposure: 2060S Special_Requirements: MAX DUR 200% END ORBIT Visit_Number: 2 Visit_Requirements: CVZ On_Hold_Comments: Visit_Comments: Exposure_Number: 1 ! Section 6.5 Target_Name: 0743-673 Config: FOS/BL Opmode: ACQ/BINARY Aperture: 4.3 Sp_Element: MIRROR Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 20S Special_Requirements: ONBOARD ACQ FOR 2-3 Exposure_Number: 2 ! Section 6.5 Target_Name: 0743-673 Config: FOS/BL Opmode: ACCUM Aperture: 1.0 Sp_Element: G190H Wavelength: Optional_Parameters: POLSCAN=8B Number_of_Iterations: 1 Time_Per_Exposure: 8693S Special_Requirements: Exposure_Number: 3 ! Section 6.5 Target_Name: 0743-673 Config: FOS/BL Opmode: ACCUM Aperture: 1.0 Sp_Element: G270H Wavelength: Optional_Parameters: POLSCAN=8B Number_of_Iterations: 1 Time_Per_Exposure: 4420S Special_Requirements: Comments: Data_Distribution ! Defaults indicated; change if desired Medium: 8MM ! 8MM or 6250BPI or 1600BPI Blocking_Factor: 10 ! 10 or 1 ! Only astronomers with very old 9- ! track tape drives should consider ! a blocking factor of 1 Ship_To: PI_Address ! STSCI or PI_Address or ! PI Address from Phase I is: ! ! 3700, San Martin Drive, ! Baltimore,MD 21218 ! ! Ship_Via: UPS ! UPS (2-day) or OVERNIGHT ! Overnight shipping done at PI expense Recipient_Email: ! Needed if Ship_To: is not PI_Address !