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PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only
ID: 5960
Version: 8
Check-in Date: **********
1.Proposal Title:
Identifying the Polarized Seyfert 1 Mirror in Markarian 463
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2. Scientific Category 3. Proposal For 4. Cycle
AGN GO 5
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5. Investigators
Contact?
PI: Alan Uomoto Johns Hopkins University
CoI: Holland Ford Johns Hopkins University N
CoI: Gerard Kriss Johns Hopkins University N
CoI: Zlatan Tsvetanov Johns Hopkins University N
CoI: Robert Antonucci University of California Santa Barbara N
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6. Abstract
Markarian 463 is a Seyfert 2 galaxy that shows a Seyfert 1 spectrum when viewed in
polarized light (Miller & Goodrich 1990). One explanation is that light from an
obscured Seyfert 1 is scattered into our line of sight (and polarized in the
process) by material with a clear view of the nucleus. The nucleus of Mkn 463 is
unresolved from the ground but HST/PC images (Uomoto et al. 1993) reveal a bright,
subarcsec optical jet extending south of the nucleus. This jet is composed of a
string of unresolved knots, some of which are likely to be the reflecting material.
We propose using the FOC to obtain near UV images in polarized light to locate the
scattering site. By combining this UV polarization information with existing ground
based data we will determine the physical nature of the mirror by distinguishing
between dust or electron scattering as the reflection mechanism. This proposal was
awarded time in Cycle 3, but only an early acquisition image was taken.
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Observations Description
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Three images of the nuclear region of Mkn 463 using the POL0, POL60, and POL120
polarizing prisms in conjunction with F342W will be obtained with the FOC. The
nuclear complex consisting of the east nucleus and the optical jet extending 1
arcsec south fits neatly into the 7x7 arcsec FOC field of view and is clear of
other strong nearby sources. An early acquisition image with the f/96 FOC will
be used to precisely locate the target and update coordinates. The F342W filter
was chosen to maximize the polarized S/N. Because the POL60 polarizer cuts off
at a redder wavelength than the other two (2250 vs 1750 Angstroms) we felt it
prudent to use a filter that strictly defines a spectral bandpass regardless of
polarizer. The F342W filter does this well. (We originally chose F320W, but
this filter is not now available.) The F342W bandpass is also blueward of the
Balmer jump for the redshift of Mkn 463, which greatly reduces dilution by the
light of old stellar populations, again enhancing polarized S/N. Finally, dust
absorption is high in the UV, limiting potential contamination by polarized
starlight. The observed count rate for the nucleus+jet complex in the near UV
is 7.6* 10^-5 phot/cm^2/s/Angstrom (based on Miller & Goodrich 1990; these
count rates assume we use F320W, which has 9% greater QT than F342W. This
should not affect our results at all.). The jet accounts for about 1/3 of this
flux (2.5* 10^-5) and this flux is distributed amongst at least 4 or 5
individual knots based on our PC images. Thus, an average knot has a flux of
about 5* 10^-6 phot/cm^2/s/Angstrom. For unpolarized objects, this results in a
count rate of about 4 Hz through the polarizers (equation 2 in the FOC Handbook
Version 5.0). A previous version of this proposal, with identical science
goals, was accepted for Cycle 3 and assigned the requested 10 hours of
spacecraft time. Only the early acquisition image was obtained before the HST
repair mission, however. This image shows the measured count rate for the
brightest knot is 6 Hz, in agreement with our estimate (note that the post-
COSTAR FOC is less sensitive than the pre-COSTAR version). The background due
to the galaxy is higher than expected, however (the equivalent of about half
the flux of the brightest knot per resolution element or 2 Hz). If we consider
the case of 10% polarization, then the signal is 0.4 Hz in the brightest knot
complex (more or less, depending on roll angle). For a desired S/N ratio of 10,
t=100*{0.4+2(3.6+2)}/0.4^2 = 2 hr (equation 1 in the FOC Handbook Version 5.0)
ignoring the small amount of instrument and non-galaxy background noise.
Exposing a factor of two or three longer to measure the fainter components
would seem appropriate but is probably not needed. Because the entire nuclear
complex shows 10% polarization we expect individual knots to show higher
values. Extending the exposure time to 2.5 hours per polarizer should be
adequate and this comfortably fills four orbits. For three polarizing prisms,
that's 12 orbits of long exposures plus one orbit of early acquisition, giving
a total of 13 orbits.
Real Time Justification
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Calibration Justification
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Additional Comments
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Data Distribution
Media: 8MM
Blocking Factor: 10
Ship To: PI_Address
Ship Via: UPS
Email: ,
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TARGET LIST a) Fixed Targets
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Tar| Target | Target | Target |Coord | Radial | Flux data
No | Name | Description | Position |Eqnx | Vel. |
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1 MKN463 GALAXY,SPIRAL,SEYFERT,U RA=13H 56M 2.823S +/- J2000.0 Z=0.0506 V=20.0+/-1.0
LTRALUMINOUS IR 0.005S,DEC=18D 22' 19.81" +/-
GAL,INTERACTING GALAXY 0.05", PLATE-ID=019M
2 MKN463-UPD GALAXY,SPIRAL,SEYFERT,U RA=13H 56M 2.936S +/- J2000.0 Z=0.0506 V=20.0+/-1.0
LTRALUMINOUS IR 0.005S,DEC=18D 22' 17.68" +/-
GAL,INTERACTING GALAXY 0.05", PLATE-ID=019M
Comments: Target coordinates updated based on early acq images
from Visit 1.
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Visit: 01
Visit Requirements: <none>
On Hold Comments: <none>
Additional Comments: Early acquisition
Exposures
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Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special
Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements
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1 MKN463 FOC/96 IMAGE 512x512 F342W 1 2100S
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Visit: 02
Visit Requirements: ORIENT 133D TO 133D
On Hold Comments: <none>
Additional Comments: COORDS HAVE NOW BEEN UPDATED
Exposures
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Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special
Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements
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2 MKN463-UPD FOC/96 IMAGE 512x512 F342W,POL 1 2100S
0
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3 MKN463-UPD FOC/96 IMAGE 512x512 F342W,POL 1 2700S
0
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4 MKN463-UPD FOC/96 IMAGE 512x512 F342W,POL 2 2700S
120
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6 MKN463-UPD FOC/96 IMAGE 512x512 F342W,POL 2 2700S
60
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Visit: 03
Visit Requirements: ORIENT 133D TO 133D
On Hold Comments: <none>
Additional Comments: COORDS HAVE NOW BEEN UPDATED
Exposures
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Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special
Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements
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8 MKN463-UPD FOC/96 IMAGE 512x512 F342W,POL 1 2100S
120
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9 MKN463-UPD FOC/96 IMAGE 512x512 F342W,POL 1 2700S
120
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10 MKN463-UPD FOC/96 IMAGE 512x512 F342W,POL 2 2700S
0
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12 MKN463-UPD FOC/96 IMAGE 512x512 F342W,POL 2 2700S
60
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Summary Form for Proposal 5960
Item Used in this proposal
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Configurations FOC/96
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Opmodes IMAGE
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Proposal Category GO
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Scientific Category AGN
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Special Requirements ORIENT 133D TO 133D
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Spectral Elements F342W F342W,POL0 F342W,POL120 F342W,POL60
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Target Names MKN463 MKN463-UPD
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