6618( 11) - 08/19/97 16:11 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6618 Version: 11 Check-in Date: 19-Aug-1997 14:00:18 1.Proposal Title: A Hidden Power Source in the QSO PG 1630+377 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle AGN GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: ROBERT GOODRICH THE W.M. KECK OBSERVATORY CoI: Anuradha Koratkar Space Telescope Science Institute N CoI: Robert Antonucci University of California, Santa Barbara N ------------------------------------------------------------------------------------ 6. Abstract Previous (Cycle 3) FOS polarimetry of the QSO PG 1630+377 has shown a steep rise in polarization well shortward of the redshifted Lyman edge (912 Angstrom). The high polarizations seen at the shortest wavelengths, P ~ 20\%, (.) probably indicate that we are seeing scattering of some hidden source. Any direct light from the source would dilute the polarization from the scattering region to much lower levels. For this hidden source to be so bright as seen only through scattering indicates that it may be intrinsically the most significant power source shortward of the Lyman edge. In order to confirm and follow-up the FOS observations we will use the FOC to study three wavelength regions in PG 1630+377, including the important region below the short wavelength limit of the FOS data. The FOC is the only instrument capable of performing these measurements, since the G130H grating in the FOS will not be calibrated for polarimetry observations. ------------------------------------------------------------------------------------ 6618( 11) - 08/19/97 16:11 - [ 2] Observations Description ------------------------ The UV polarimetry necessary to confirm and extend our earlier FOS observations of PG 1630+377 is available only with HST, and only with the FOC. We will use three passbands, F140W, F170M, and F231M+F130LP. The F140W band will probe the UV at wavelengths shorter than the existing FOS observations. Note that the post-COSTAR FOS will not be calibrated for polarimetry with the G130H grating, so we cannot use the FOS to probe these wavelengths without a prohibitive calibration overhead. This wavelength region is critical for testing the theories proposed for the high polarization in PG 1630+377. The F170M filter will probe the wavelengths which were observed to have high polarization with the FOS. This is important to confirm the FOS polarimetry. Several QSOs have shown a rise in P at short wavelengths with the FOS (Impey et al. 1995; Koratkar et al. 1995), so this confirmation will help to interpret those data as well. The F231M filter will probe wavelengths longer than the rise in P seen in the FOS. The calculated count rate from the F231M filter is 1.2 count pixel^ -1 s^-1, above the 1 count pixel^-1 s^-1 limit to the linear regime of the FOC, so we will use the F130LP as a weak ND filter to keep the count rate within the linear range (0.8 count pixel^-1 s^-1 with the F130LP filter). Important caveat. One of the three polarizers in the FOC, POL60, does not transmit shortward of 2000 Angstrom. Hence we will require a slightly different technique to measure the polarization using only two of the polarizers. Ideally we would roll the telescope -30degrees from the nominal roll angle, and take a set of POL0 and POL120 exposures. Then we would roll the telescope +30degrees and use the POL0 polarizer to reproduce the POL60 position angle. Unfortunately, RPS2 testing using a mockup of a proposal file shows that we cannot reach +/- 30degrees roll angles from nominal for PG1630+377. The maximum we can get is +/- 26degrees. This will make the data reduction slightly different than the usual reduction using polarizers at angles of 0degrees, 60degrees, and 120degrees, but since we will know the actual roll angles accurately it will not compromise our results. One of us (RWG) already has experience in reducing polarimetry using non-optimal polarizer angles using WFPC2. The exposure times and signal-to-noise ratios (S/N) were calculated with FOCSIM, using the observed total flux spectrum of PG 1630+377, based on FOS, IUE, and ground-based spectra, as the input spectrum. The ground-based spectra are important for quantifying the red leaks of the filters, the fraction of recorded photons which are actually leaking through from wavelength longward of the nominal passband. The red leaks are small (6\\\\\\\\% for F140M, 2\\\\\\\\% for F170M, and 0.7\\\\\\\\% for F231M and for photons with wavelengths above 3000 Angstrom). The FOCSIM results will allow us to correct for the red leaks if necessary. Single-orbit exposures per polarizer are adequate for polarization uncertainties of <= 3\\\\\\\\% in the shorter passbands. Half- orbit exposures suffice for the F231M+F130LP combination. With three filter combinations and three polarizer angles each, we require 8 orbits total. Real Time Justification ----------------------- We will require specific spacecraft rolls, as described in the Description of the Observations. We have used RPS2 and a mockup of a Cycle 5 proposal to see what roll angles are available, and have found that we can get -26degrees and +26degrees from the nominal roll angle during a short interval in July. Of course, the time period of optimum schedulability will change somewhat with Cycle 6, but our mockup shows that these roll angles are feasible. None. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6618( 11) - 08/19/97 16:11 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 6618( 11) - 08/19/97 16:11 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PG1630+377 GALAXY, QSO RA=16H 32M 1.16S +/- 1",DEC=37D J2000 Z=1.466 V = 16.1+/-0.2 37' 49.7" +/- 1" F-CONT(1700)=1.3+/-0.13e-15 F-CONT(1900)=1.5+/-0.15e-15 F-CONT(2000)=1.9+/-0.2e-15 F-CONT(2200)=2.5+/-0.3e-15 F-CONT(2500)=3.1+/-0.3e-15 F-CONT(3000)=2.7+/-0.3e-15 6618( 11) - 08/19/97 16:11 - [ 5] Visit: 51 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 PG1630+377 FOC/96 IMAGE 512X512 POL0, PIXEL=25X25 1 1110 S F170M ------------------------------------------------------------------------------------------------------------------------------------ 2 PG1630+377 FOC/96 IMAGE 512X512 POL120, PIXEL=25X25 1 1110 S F170M Comments: POL0 and POL120 in exposures 1 and 2 displace the image nearly the same amount, so we won't use a POS TARG to make sure the images are in the same spot. ------------------------------------------------------------------------------------------------------------------------------------ 3 INTFLAT FOC/96 RESEAU 512X512 CLEAR PIXEL=25X25,LED=BLUE,LED-STEP=3 1 600 S ------------------------------------------------------------------------------------------------------------------------------------ 4 INTFLAT FOC/96 RESEAU 512X512 CLEAR PIXEL=25X25,LED=BLUE,LED-STEP=4 1 600 S ------------------------------------------------------------------------------------------------------------------------------------ 5 PG1630+377 FOC/96 IMAGE 512X512 POL0, PIXEL=25X25 1 1256 S POS TARG 0.2,0.2 F170M Comments: We use a POS TARG here to sample a different region of the FOC detector, to get an idea of flat field uncertainties. ------------------------------------------------------------------------------------------------------------------------------------ 6 PG1630+377 FOC/96 IMAGE 512X512 POL120, PIXEL=25X25 1 1256 S POS TARG 0.2,0.2 F170M ------------------------------------------------------------------------------------------------------------------------------------ 7 INTFLAT FOC/96 RESEAU 512X512 CLEAR PIXEL=25X25,LED=BLUE,LED-STEP=5 1 600 S ------------------------------------------------------------------------------------------------------------------------------------ 8 INTFLAT FOC/96 RESEAU 512X512 CLEAR PIXEL=25X25,LED=BLUE,LED-STEP=6 1 600 S ------------------------------------------------------------------------------------------------------------------------------------ 9 PG1630+377 FOC/96 IMAGE 512X512 POL0, PIXEL=25X25 1 1256 S F231M, F130LP ------------------------------------------------------------------------------------------------------------------------------------ 10 PG1630+377 FOC/96 IMAGE 512X512 POL120, PIXEL=25X25 1 1256 S F231M, F130LP ------------------------------------------------------------------------------------------------------------------------------------ 6618( 11) - 08/19/97 16:11 - [ 6] Visit: 52 Visit Requirements: ORIENT 54D TO 60D FROM 51 AFTER 51 BY 0 D TO 5 D 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 PG1630+377 FOC/96 IMAGE 512X512 POL0, PIXEL=25X25 1 1110 S F170M ------------------------------------------------------------------------------------------------------------------------------------ 2 PG1630+377 FOC/96 IMAGE 512X512 POL120, PIXEL=25X25 1 1110 S F170M Comments: POL0 and POL120 displace the image nearly the same amount, so we won't use a POS TARG to make sure the images are in the same spot. ------------------------------------------------------------------------------------------------------------------------------------ 3 INTFLAT FOC/96 RESEAU 512X512 CLEAR PIXEL=25X25,LED=BLUE,LED-STEP=7 1 600 S ------------------------------------------------------------------------------------------------------------------------------------ 4 INTFLAT FOC/96 RESEAU 512X512 CLEAR PIXEL=25X25,LED=BLUE,LED-STEP=8 1 600 S ------------------------------------------------------------------------------------------------------------------------------------ 5 PG1630+377 FOC/96 IMAGE 512X512 POL0, PIXEL=25X25 1 1256 S F231M, F130LP ------------------------------------------------------------------------------------------------------------------------------------ 6 PG1630+377 FOC/96 IMAGE 512X512 POL120, PIXEL=25X25 1 1256 S F231M, F130LP ------------------------------------------------------------------------------------------------------------------------------------ 6618( 11) - 08/19/97 16:11 - [ 7] Summary Form for Proposal 6618 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOC/96 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE RESEAU ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters PIXEL=25X25 LED-STEP=3 LED-STEP=4 LED-STEP=5 LED-STEP=6 LED-STEP=7 LED-STEP=8 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category AGN ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements POS TARG 0.2,0.2 ORIENT 54D TO 60D FROM 51 AFTER 51 BY 0 D TO 5 D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements POL0,F170M POL120,F170M CLEAR POL0,F231M,F130LP POL120,F231M,F130LP ------------------------------------------------------------------------------------------------------------------------------------ Target Names PG1630+377 INTFLAT ------------------------------------------------------------------------------------------------------------------------------------