Publications (2)0 Total impact
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ABSTRACT: In this paper we study the properties of the optical spectra of Type 1 active
galactic nuclei (AGNs) by using the unobscured hard X-ray emission as a
diagnostic. We develop the `Correlation Spectrum Technique' (CST) and use this
to show the strength of correlation between the hard X-ray luminosity and each
wavelength of the optical spectrum. This shows that for Broad Line Seyfert 1s
all the strong emission lines (broad component of H\alpha and H\beta, [NeIII]
\lambda\lambda 3869/3967, [OI] \lambda\lambda 6300/6364, [OII] \lambda\lambda
3726/3729, [OIII] \lambda\lambda 4959/5007) and the optical underlying
continuum all strongly correlate with the hard X-ray emission. But the NLS1s
appear to be somewhat different. Among the various Balmer line components and
the broadband SED components, the best correlation exists between the hard
X-ray component and broad component (BC) of the Balmer lines, which supports
the view that broad line region (BLR) has the closest link with the AGN's
compact X-ray emission. The equivalent widths of Balmer line IC and BC are
found to correlate with L$_{2-10keV}$, $\kappa_{2-10keV}^{-1} =
L_{bol}/L_{2-10keV}$, Balmer line FWHM and black hole mass. There is a
non-linear dependence of the Balmer line IC and BC luminosities with
L$_{2-10keV}$ and L$_{5100}$, which suggests that a second-order factor such as
the ILR and BLR covering factors affect the Balmer line component luminosities.
The Balmer decrement is found to decrease from ~5 in the line core to ~2 in the
extended wings, with mean decrements of 2.1 in BLR and 4.8 in ILR. This
suggests different physical conditions in these regions. The [OIII] line is
composed of a narrow core together with a blue-shifted component with average
outflow velocity of $130^{+230}_{-80} km s^{-1}$. The total luminosity of
[OIII] \lambda 5007 well correlates with the hard X-ray luminosity.
03/2012;
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ABSTRACT: We present modeling and interpretation of the continuum and emission lines
for a sample of 51 unobscured Type 1 active galactic nuclei (AGN). All of these
AGNs have high quality spectra from both XMM-Newton and Sloan Digital Sky
Survey (SDSS). We extend the wavelength coverage where possible by adding
simultaneous UV data from the OM onboard XMM-Newton. Our sample is selected
based on low reddening in the optical and low gas columns implied by their
X-ray spectra. They also lack clear signatures for the presence of a warm
absorber. Therefore the observed characteristics of this sample are likely to
be directly related to the intrinsic properties of the central engine.
We perform multi-component spectral fitting for strong optical emission lines
and the whole optical spectra. We fit the combined optical, UV and X-ray data
by applying a new broadband SED model which comprises the accretion disc
emission, low temperature optically thick Comptonisation and a hard X-ray tail
by introducing the a corona radius (Done et al. 2011). We find that in order to
fit the data, the model often requires an additional long wavelength optical
continuum component, whose origin is discussed in this paper. We also find that
the Photo-recombination edge of Balmer continuum shifts and broadens beyond the
standard limit of 3646{\AA}, implying an electron number density which is far
higher than that in the broad line region clouds.
Our results indicate that the Narrow Line Seyfert 1s in this sample tend to
have lower black hole masses, higher Eddington ratios, softer 2-10 keV band
spectra, lower 2-10 keV luminosities and higher \alpha_{ox}, compared with
typical broad line Seyfert 1s (BLS1), although their bolometric luminosities
are similar. We illustrate these differences in properties by forming an
average SED for three subsamples, based on the FWHM velocity width of the
H{\beta} emission line.
09/2011;
