6705( 6) - 03/08/96 09:58 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6705 Version: 6 Check-in Date: 08-Mar-1996 09:50:34 1.Proposal Title: Below the Lyman Edge: UV Polarimetry of Quasars ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle AGN GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Anuradha Koratkar Space Telescope Science Institute CoI: Robert Goodrich Space Telescope Science Institute N CoI: Robert Antonucci University of California, Santa Barbara N ------------------------------------------------------------------------------------ 6. Abstract The Lyman edge at 912 Angstrom is an important diagnostic region for studying quasi- stellar objects (QSOs). In particular, it reveals a great deal about the physical conditions within the atmospheres of accretion disks, a ubiquitous component of QSO theories. A fairly robust prediction of accretion disk theory is a high polarization just longward (in wavelength) of the edge. Observations of the Lyman edge regions of QSOs have shown scant evidence for the predicted features---few QSOs show the broad, partial Lyman edges expected to be common according to most theories, and none show the high polarizations expected longward of the Lyman edge. Still, polarization spectra of a small number of QSOs have shown a rising polarization (up to 20\%) at wavelengths shortward of the Lyman edge. The cause for this rise is not well understood, mostly because only one object, PG 1630+377, has been studied in enough detail to determine some characteristics of the polarization feature. We propose to observe four bright QSOs, chosen for having strong UV flux at rest wavelengths shorter than 800 Angstrom, to search for evidence of this highly polarized component and to better define its character. As a byproduct we will also accumulate more information on the polarization properties of QSOs longward of the Lyman edge. Cycle 6 will be the last chance for this type of study for the foreseeable future, with the impending removal of the FOS and HST's spectropolarimetric capability. ------------------------------------------------------------------------------------ 6705( 6) - 03/08/96 09:58 - [ 2] Observations Description ------------------------ We will use the FOS with the G190H and G270H gratings and the polarimetry optics. We have used archival spectra from both IUE and HST to estimate continuum fluxes of our targets at various wavelengths, and the tables in the FOS Instrument Handbook to calculate count rates for each target at those wavelengths. To account for the throughput of the polarimetry optics and the inefficiencies of the wave plate (caused by its retardance not being exactly 180degrees at all wavelengths) we multiply these count rates by ~ 0.35. Using the empirical formula for converting total counts to the polarization uncertainty (section 1.6 of the FOS Instrument Handbook), we calculated exposure times which would yield a polarization uncertainty of 1\\\\\\\\\\\\\\\\% or less in 100 Angstrom bins. def\\\\\\\\\\\\\\\\flamerg cm^ -2 s^-1 AA^-1 We use as an example PG 1522+101, which has continuum fluxes of 7 * 10^-15 \\\\\\\\\\\\\\\\flam in the G190H grating and 5 * 10^-15 \\\\\\\\\\\\\\\\flam in the G270H grating. The inverse sensitivities are roughly 4 * 10^-14 \\\\\\\\\\\\\\\\flam counts^-1 s diode in the G190H and 4 * 10^-15 \\\\\\\\\\\\\\\\flam counts^-1 s diode in the G270H. The count rates are hence 0.175 and 1.25 count s^-1 diode^-1 in G190H and G270H respectively. Note that dark count is not significant. Multiplying these by the polarimetry efficiency of 0.35 and also by the number of diodes per 100 Angstrom bin (68 for the G190H and 48 for the G270H) we get 4.16 and 21 count s^-1. The polarization uncertainty is given by Sigma(P) = 4.16% (1600/N)^1/2 where N is the total number of counts for an entire set of polarimetry observations. To achieve Sigma(P) = 1\\\\\\\\\\\\\\\\% we require 28,000 total counts, implying exposure times of 6700 s and 1400 s in G190H and G270H, respectively. We hence require 3 orbits for the G190H data and a single orbit for the G270H data. Using a binary acquisition with the FOS we can fit the G270H easily into the end of the first orbit. These targets are not known to vary, have well-measured V magnitudes, and are bright enough for the binary acquisition strategy. Real Time Justification ----------------------- None. Calibration Justification ------------------------- None. Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6705( 6) - 03/08/96 09:58 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 UM18 GALAXY,QSO,QUASAR, RA=00H 05M 20.22S +/- J2000 Z = V = 16.21 0.5",DEC=05D 24' 11.08" +/- 1.887 F(2200)=1.7+/-0.2e-15 0.5",PLATE-ID=026E F(3250)=1.85+/-0.2e-15 Comments: Lyman edge at 2633 angstrom. Coordinates determined from gasp images. The previous FOS observations have a failed ACQ/BIN. 2 1247+267 GALAXY,QSO,QUASAR, RA=12H 50M 05.727S +/- J2000 Z = V = 15.8 0.5",DEC=26D 31' 07.53" +/- 2.038 F(2300)=3.2+/-0.4e-15 0.5",PLATE-ID=01PM F(3100)=3.0+/-0.3e-15 Comments: Lyman edge at 2770 angstrom. Coordinates determined from gasp images and previous FOS observations. Pervious ACQ/BIN successful. 3 1522+101 GALAXY,QSO,QUASAR, RA=15H 24M 24.527S +/- J2000 Z = V = 15.74 0.6",DEC=09D 58' 29.406" +/- 1.321 F(1570)=5.5+/-0.4e-15 0.6",PLATE-ID=0291 F(1700)=6.2+/-0.5e-15 F(1800)=8.0+/-0.6e-15 F(2000)=6.6+/-0.6e-15 F(2300)=6.0+/-0.7e-15 F(2700)=5.0+/-0.4e-15 Comments: Lyman edge at 2120 angstrom. Coordinates determined from gasp images and previous FOS observations. ACQ/BIN previous was successful 4 1718+481 GALAXY,QSO,QUASAR, RA=17H 19M 38.23S +/- J2000 Z = V = 15.33 1.0",DEC=48D 04' 13.01" +/- 1.084 F(1600)=18.5+/-3e-15 1.0",PLATE-ID=02D4 F(2400)=15.2+/-3e-15 Comments: Lyman edge at 1900 angstrom, intervening edge at 1550. Coordinates determined from gasp images. Coordinates of previous FOS observations not used since ACQ/BIN unsucessful 6705( 6) - 03/08/96 09:58 - [ 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 UM18 FOS/BL ACQ/BIN 4.3 MIRROR 1 13S ONBOARD ACQ FOR 2-8 ARY ------------------------------------------------------------------------------------------------------------------------------------ 2 UM18 FOS/BL ACCUM 1.0 G270H POLSCAN=8B 1 1430S MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 3 UM18 FOS/BL ACCUM 1.0 G270H POLSCAN=8B 1 2210S MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 4 UM18 FOS/BL ACCUM 1.0 G190H POLSCAN=8B 1 2090S MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 5 UM18 FOS/BL ACCUM 1.0 G190H POLSCAN=8B 1 2210S MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 6 UM18 FOS/BL ACCUM 1.0 G190H POLSCAN=8B 1 2230S MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 7 UM18 FOS/BL ACCUM 1.0 G190H POLSCAN=8B 1 2220S MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 8 UM18 FOS/BL ACCUM 1.0 G190H POLSCAN=8B 1 2200S MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 6705( 6) - 03/08/96 09:58 - [ 5] Visit: 02 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 1247+267 FOS/BL ACQ/BIN 4.3 MIRROR 1 7S ONBOARD ACQ FOR 2-3 ARY ------------------------------------------------------------------------------------------------------------------------------------ 2 1247+267 FOS/BL ACCUM 1.0 G270H POLSCAN=8B 1 1420S MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 3 1247+267 FOS/BL ACCUM 1.0 G270H POLSCAN=8B 1 2220S MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 6705( 6) - 03/08/96 09:58 - [ 6] Visit: 03 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 1522+101 FOS/BL ACQ/BIN 4.3 MIRROR 1 6S ONBOARD ACQ FOR 2-5 ARY ------------------------------------------------------------------------------------------------------------------------------------ 2 1522+101 FOS/BL ACCUM 1.0 G270H POLSCAN=8B 1 1200S MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 3 1522+101 FOS/BL ACCUM 1.0 G190H POLSCAN=8B 1 2200S MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 4 1522+101 FOS/BL ACCUM 1.0 G190H POLSCAN=8B 1 2220S MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 5 1522+101 FOS/BL ACCUM 1.0 G190H POLSCAN=8B 1 2210S MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 6705( 6) - 03/08/96 09:58 - [ 7] Visit: 04 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 1718+481 FOS/BL ACQ/BIN 4.3 MIRROR 1 2S ONBOARD ACQ FOR 2-4 ARY ------------------------------------------------------------------------------------------------------------------------------------ 2 1718+481 FOS/BL ACCUM 1.0 G270H POLSCAN=8B 1 1640S MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 3 1718+481 FOS/BL ACCUM 1.0 G190H POLSCAN=8B 1 2320S MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 4 1718+481 FOS/BL ACCUM 1.0 G190H POLSCAN=8B 1 2340S MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 6705( 6) - 03/08/96 09:58 - [ 8] Summary Form for Proposal 6705 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/BINARY ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters POLSCAN=8B ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category AGN ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2-8 MAX DUR 200% ONBOARD ACQ FOR 2-3 ONBOARD ACQ FOR 2-5 ONBOARD ACQ FOR 2-4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G270H G190H ------------------------------------------------------------------------------------------------------------------------------------ Target Names UM18 1247+267 1522+101 1718+481 ------------------------------------------------------------------------------------------------------------------------------------