Tek P. Adhikari

SALT long-slit spectroscopy of CTS C30.10: two-component Mg II line

Context. Quasars can be used as a complementary tool to SN Ia to probe the distribution of dark energy in the Universe by measuring the time delay of the emission line with respect to the continuum. The understanding of the Mg II emission line structure is important for cosmological application and for the black hole mass measurements of intermediate redshift quasars. Aims. Knowing the shape of Mg II line and its variability allows for identifying which part of the line should be used to measure the time delay and the black hole mass. We thus aim at determining the structure and the variability of the Mg II line, as well as the underlying Fe II pseudo-continuum. Methods. We performed five spectroscopic observations of a quasar CTS C30.10 (z = 0.9000) with the SALT telescope between December 2012 and March 2014, and we studied the variations in the spectral shape in the 2700 A−2900 A rest frame. Results. We show that the Mg II line in this source consists of two kinematic components, which makes the source representative of type B quasars. Both components were modeled well with a Lorentzian shape, and they vary in a similar way. The Fe II contribution seems to be related only to the first (blue) Mg II component. Broad band spectral fitting instead favor the use of the whole line profile. The contribution of the narrow line region to Mg II is very low, below 2%. The Mg II variability is lower than the variability of the continuum, which is consistent with the simple reprocessing scenario. The variability level of CTS C30.10 and the measurement accuracy of the line and continuum is high enough to expect that further monitoring will allow the time delay between the Mg II line and continuum to be measured.

Absorption Measure Distribution in Mrk 509

In this paper we model the observed absorption measure distribution (AMD) in Mrk 509, which spans three orders of magnitude in ionization level with a single-zone absorber in pressure equilibrium. AMD is usually constructed from observations of narrow absorption lines in radio-quiet active galaxies with warm absorbers. We study the properties of the warm absorber in Mrk~509 using recently published broad-band spectral energy distribution observed with different instruments. This spectrum is an input in radiative transfer computations with full photoionisation treatment using {\sc titan} code. We show that the simplest way to fully reproduce the shape of AMD is to assume that the warm absorber is a single zone under constant total pressure. With this assumption we found theoretical AMD which matches the observed one determined on the basis of 600 ks RGS XMM-Newton spectrum of Mrk~509. The softness of the source spectrum and the important role of the free-free emission breaks the usual degeneracy in the ionization state calculations, and the explicit dependence of the depths of AMD dips on density open a new path to density diagnostic for the warm absorber. In Mrk 509 the implied density is of the order of

The Intermediate-Line Region in Active Galactic Nuclei

10^8

X-ray observations of the hot phase in Sagittarius A*

cm

Intermediate-line Emission in AGNs: The Effect of Prescription of the Gas Density

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Multiphase environment of compact galactic nuclei: the role of the nuclear star cluster

.

SALT long-slit spectroscopy of quasar HE 0435-4312: fast displacement of the Mg II emission line

We show that the recently observed suppression of the gap between the broad line region (BLR) and the narrow line region (NLR) in some AGN can be fully explained by an increase of the gas density in the emitting region. Our model predicts the formation of the intermediate line region (ILR) that is observed in some Seyfert galaxies by the detection of emission lines with intermediate velocity full width half maximum (FWHM)

Modeling of the Quasar Main Sequence in the Optical Plane

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Ultraluminous X-ray sources: new distance indicators?

700 - 1200 km s

On the Intermediate Line Region in AGNs

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