Bibcode
DOI
de Diego, J. A.; Kidger, M. R.; Perez, E.; Takalo, L. O.
Bibliographical reference
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 424, no. 1, p. 76-83
Advertised on:
3
1994
Journal
Citations
6
Refereed citations
5
Description
We present spectropolarimetric observations of a sample of three quasars
selected because of their very different broad-band polarization
properties. All of the objects in the sample show frequency-dependent
polarization degree (FDP), and two of them also show frequency-dependent
polarization position angle (FDPA). We have not detected polarization in
the spectral emission lines in any object of the sample, although the
possibility exists that the iron blends in CTA 102 may be polarized. Our
observations show important differences between the three objects. While
3C 273 has been previously discussed in terms of a multiple synchrotron
source model, a conclusion supported by our results, this seems not to
be the case for 3C 345. We examine a number of processes capable of
generating the observed FDP and FDPA of this object. A combination of a
nonthermal source and scattering from dust or gas in the local
interstellar medium can explain our observations, although some
restrictions must be imposed to avoid polarization of the spectral
emission lines. The quasar CTA 102 shows a very complex
wavelength-dependent polarization, which may be related to the iron
blends in the spectrum. We also present a statistical test developed by
us to examine the possible polarization of the lines.