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: <none>
On Hold Comments: <none>
Additional Comments: <none>
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: <none>
Additional Comments: <none>
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
------------------------------------------------------------------------------------------------------------------------------------