HST Imaging Polarimetry of the Seyfert 2 Galaxy NGC 5728

Details HST Imaging Polarimetry of the Seyfert 2 Galaxy NGC 5728 HST Imaging Polarimetry of the Seyfert 2 Galaxy NGC 5728

Jul 1996

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996apj...466..169c&link_type=abstract

Astrophysical Journal v.466, p.169

Astronomy and Astrophysics

Astronomy

17

Galaxies: Seyfert, Galaxies: Individual Ngc Number: Ngc 5728, Polarization, Galaxies: Nuclei

Scientific paper

We present the results of HST imaging polarimetry of NGC 5728 taken with the COSTAR corrected Faint Object Camera in the ultraviolet (3000- 3700 A) and covering the region interior to its well-known nuclear ring. The total intensity image is dominated by a bright extended core, 1" x 0.7" in size, which is resolved into a large number of compact knots which are coincident with the bright inner region of the Eastern emission-line cone found by previous observers. A barlike structure extends from this core for over 3" toward the east along P.A. + 75^deg^ to the star formation ring. On the large scale the polarization vectors are predominantly aligned with the major axis of the kpc scale bar of NGC 5728 and the polarization is dominated by dichroic transmission through dust grains. Significant deviations from this uniform polarization pattern are observed in the innermost regions. Subtraction of the dichroic polarization reveals a centro-symmetric polarization pattern, due to scattering of nuclear light, except in the region of the inner bar. As in the large-scale bar, the polarization vectors in the inner bar are parallel with its major axis, and imply the presence of a magnetic field which is similarly aligned. The associated polarized flux distribution appears as an approximately double-lobed structure, extending for at least 1.2 kpc in a sector from P.A. ~53^deg^ to ~147^deg^ in which the bright core stands out prominently, even in the knots, showing it is a region of enhanced scattering. The angular distribution of the polarized flux is substantially wider than the emission lines cones which have an opening angle between 55^deg^-65^deg^. A similar result has been found previously in NGC 1068. This can be explained by the presence in the obscuring torus of a transition region which is transparent to the UV light while still blocking the ionizing flux. Alternatively, the line emitting material does not fill the region illuminated by the nucleus. In each case, the scattered light is a better tracer of the geometry of the nuclear radiation field. We have used the center of symmetry of the centro-symmetric polarization pattern to determine the location of the nucleus, which we find to be at R.A. 14^h^42^m^23.91^s^, decl. -17^deg^42'10.9", and which lies in the dust lane dividing the emission line bi-cone. As expected from the unified schemes, this result confirms that the nucleus of NGC 5728 is hidden from our direct view. A conservative upper limit of 1.9% to the FOC/COSTAR instrumental polarization can be set comparing these results with ground based observations.

Affiliated with

Also associated with

No associations

Rating

HST Imaging Polarimetry of the Seyfert 2 Galaxy NGC 5728 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with HST Imaging Polarimetry of the Seyfert 2 Galaxy NGC 5728, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and HST Imaging Polarimetry of the Seyfert 2 Galaxy NGC 5728 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1116675