Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996aas...189.9810v&link_type=abstract
American Astronomical Society, 189th AAS Meeting, #98.10; Bulletin of the American Astronomical Society, Vol. 28, p.1405
Astronomy and Astrophysics
Astronomy
Scientific paper
A small fraction of Quasars (QSO) emit powerful radio emission. Whether this is due to favourable conditions in the radio-loud QSO or is due to more fundamental differences in the central engine is currently unknown. The UV Broad Emission Lines (BEL) trace conditions close to the QSO core (~pc) where the radio emission also emerges and so are important tools to address the questions of possible fundamental differences between radio-loud (RL) and radio-quiet (RQ) QSOs. Our investigation is based on a sample of 110 QSOs, equally divided between RL and RQ objects, which are carefully matched with respect to luminosity and redshift in pairs of a RL and RQ QSO. The RL QSOs span a range of radio spectral steepness and luminosity. The aim of the study is partly to compare the Ultra-Violet BEL profile morphologies in the two QSO types and study the possible (subtle) effects of the powerful radio emission on the line profiles, and partly to study these profiles with respect to (the radio) source orientation. Given our improved sample selection our study is expected to reveal the luminosity-dependent correlations amongst previous results. We will compare measurements such as full widths at various fractions of the flux maximum, equivalent widths and Interpercentile Velocity Widths between our subsamples and with previously reported findings. Some of the preliminary results based on a subset of the sample, which we present here, are that contrary to previous findings for CIVlambda 1549 and CIII]lambda 1909 only CIII] shows a significant width difference between the RL and RQ QSOs measured anywhere between 40--80% of the peak flux. This may be attributed to fainter AlIII]lambda 1858 emission in RL QSOs. Also FWHM(CIV) correlates with the radio spectral index and anticorrelates with the radio core dominance displaying an avoidance of very broad profiles in core-dominated objects, similar to the Hβ line width (Wills & Browne, 1986, Ap.J. 302, 56).
Barthel Petra
Vestergaard Marianne
Wilkes Belinda J.
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