! Proposal 5960, submission 2 ! PI: Alan Uomoto ! Received Mon Aug 7 15:54:24 EDT 1995 ! From: uomoto@stsci.edu Proposal_Information ! Section 4 Title: Identifying the Polarized Seyfert 1 Mirror in Markarian 463 Proposal_Category: GO Scientific_Category: AGN Cycle: 5 Investigators PI_name: Alan Uomoto PI_Institution: Johns Hopkins University CoI_Name: Holland Ford CoI_Institution: Johns Hopkins University CoI_Name: Gerard Kriss CoI_Institution: Johns Hopkins University CoI_Name: Zlatan Tsvetanov CoI_Institution: Johns Hopkins University CoI_Name: Robert Antonucci CoI_Institution: University of California Santa Barbara 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. Questions Observing_Description: 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. Additional_Comments: Fixed_Targets Target_Number: 1 Target_Name: MKN463 Alternate_Names: MRK463 Description: GALAXY,SPIRAL,SEYFERT,ULTRALUMINOUS IR GAL,INTERACTING GALAXY Position: RA=13H 56M 2.823S +/- 0.005S,DEC=18D 22' 19.81" +/- 0.05", PLATE-ID=019M Equinox: J2000.0 RV_or_Z: Z=0.0506 Flux: V=20.0+/-1.0 Comments: Target_Number: 2 Target_Name: MKN463-UPD Alternate_Names: MRK463 Description: GALAXY,SPIRAL,SEYFERT,ULTRALUMINOUS IR GAL,INTERACTING GALAXY Position: RA=13H 56M 2.936S +/- 0.005S,DEC=18D 22' 17.68" +/- 0.05", PLATE-ID=019M Equinox: J2000.0 RV_or_Z: Z=0.0506 Flux: V=20.0+/-1.0 Comments: Target coordinates updated based on early acq images from Visit 1. Visits ! Visit_Number: 1 Visit_Requirements: Visit_Comments: Early acquisition Exposure_Number: 1 Target_Name: MKN463 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F342W Number_of_Iterations: 1 Time_Per_Exposure: 35M Comments: Visit_Number: 2 Visit_Requirements: ORIENT 133D TO 133D On_Hold_Comments: Visit_Comments: COORDS HAVE NOW BEEN UPDATED Exposure_Number: 2 Target_Name: MKN463-UPD Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F342W,POL0 Number_of_Iterations: 1 Time_Per_Exposure: 35M Special_Requirements: Comments: Exposure_Number: 3 Target_Name: MKN463-UPD Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F342W,POL0 Number_of_Iterations: 1 Time_Per_Exposure: 45M Comments: Exposure_Number: 4 Target_Name: MKN463-UPD Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F342W,POL120 Number_of_Iterations: 2 Time_Per_Exposure: 45M Comments: Exposure_Number: 6 Target_Name: MKN463-UPD Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F342W,POL60 Number_of_Iterations: 2 Time_Per_Exposure: 45M Comments: Visit_Number: 3 Visit_Requirements: ORIENT 133D TO 133D On_Hold_Comments: Visit_Comments: COORDS HAVE NOW BEEN UPDATED Exposure_Number: 8 Target_Name: MKN463-UPD Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F342W,POL120 Number_of_Iterations: 1 Time_Per_Exposure: 35M Comments: Exposure_Number: 9 Target_Name: MKN463-UPD Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F342W,POL120 Number_of_Iterations: 1 Time_Per_Exposure: 45M Comments: Exposure_Number: 10 Target_Name: MKN463-UPD Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F342W,POL0 Number_of_Iterations: 2 Time_Per_Exposure: 45M Comments: Exposure_Number: 12 Target_Name: MKN463-UPD Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F342W,POL60 Number_of_Iterations: 2 Time_Per_Exposure: 45M Comments: Data_Distribution Medium: 8MM ! 8MM or 6250BPI or 1600BPI Blocking_Factor: 10 ! 10 or 1 ! 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