arXiv subjects

Jelena Kovacevic-Dojcinovic

Publications and source records attributed to Jelena Kovacevic-Dojcinovic.

4 recordsLinked to original sources

arXiv2022

The LSST era of supermassive black holes accretion-disk reverberation mapping

The Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will detect an unprecedentedly large sample of actively accreting supermassive black holes with typical accretion disk (AD) sizes of a few light days. This brings us to face challenges in the reverberation mapping (RM) measurement of AD sizes in active galactic nuclei (AGNs) using interband continuum delays. We examine the effect of LSST cadence strategies on AD RM using our metric AGNTimeLagMetric. It accounts for redshift, cadence, the magnitude limit, and magnitude corrections for dust extinction. Running our metric on different LSST cadence strategies, we produce an atlas of the performance estimations for LSST photometric RM measurements. We provide an upper limit on the estimated number of quasars for which the AD time lag can be computed within 0 1000 sources in each Deep Drilling field (DDF, 10 sq. deg) in any filter, with the redshift distribution of these sources peaking at z~1. We find the LSST observation strategies with a good cadence (~ 5 days) and a long cumulative season (~9 yr), as proposed for LSST DDF, are favored for the AD size measurement. We create synthetic LSST light curves for the most suitable DDF cadences and determine RM time lags to demonstrate the impact of the best cadences based on the proposed metric.

astro-ph.IM↗

arXiv2021

Tracing the outflow kinematics in Type 2 Active Galactic Nuclei

We have used the sample of 577 active galactic nuclei Type 1.8-2 spectra (z < 0.25), taken from Sloan Digital Sky Survey, to trace the influence of the outflow kinematics to the profiles of different emission lines (Hbeta, [O III], Halpha, [N II], [S II]). All considered lines were fitted with two Gaussian components: one which fits the core of the line, and another which fits the wings. We gave the procedure for decomposition of Halpha+[N II] wavelength band, for the spectra where these lines overlap. The influence of the gravitational/non-gravitational kinematics to the line components is investigated by comparing the dispersions of the line components with stellar velocity dispersion. We found that wing components of all considered emission lines have pure non-gravitational kinematics, the core components are consistent with gravitational kinematics for the Halpha, [N II] and [S II] lines, while in the [O III] there is evidence for contribution from non-gravitational kinematics. We adopted the wing components as proxy of the outflow contribution and we investigated the outflow kinematics by analysing the correlations between widths and between shifts of the wing components of different lines. We found the strong correlations between shifts and between wing component widths of all considered lines, with exception of the Hbeta wing component width. These correlations indicate that outflow dynamics systemically affects all emission lines in spectrum. However, it reflects with different strength in their profiles, which is observed as different widths of the wing components. The strongest outflow signature is observed in the [O III] lines, which have the broadest wing components, weaker in Halpha and [N II], and the weakest in [S II]. These results imply that considered lines arise in different parts of an outflowing region.

astro-ph.GA↗

arXiv2016

Virilization of the Broad Line Region in Active Galactic Nuclei - connection between shifts and widths of broad emission lines

We investigate the virilization of the emission lines Hbeta and Mg II in the sample of 287 Type 1 Active Galactic Nuclei taken from the Sloan Digital Sky Survey database. We explore the connections between the intrinsic line shifts and full widths at different levels of maximal intensity. We found that: (i) Hbeta seems to be a good virial estimator of black hole masses, and an intrinsic redshift of Hbeta is dominantly caused by the gravitational effect, (ii) there is an anti-correlation between the redshift and width of the wings of the Mg II line, (iii) the broad Mg II line can be used as virial estimator only at 50% of the maximal intensity, while the widths and intrinsic shifts of the line wings can not be used for this purpose.

astro-ph.GA↗

arXiv2016

The UV and optical Fe II emission lines in type 1 AGNs

We investigate the spectral properties of the UV ($λλ$2650-3050 Å) and optical ($λλ$4000-5500 Å) Fe II emission features in a sample of 293 type 1 active galactic nuclei (AGNs) from Sloan Digital Sky Survey (SDSS) database. We explore different correlations between their emission line properties, as well as the correlations with the other emission lines from the spectral range. We find several interesting correlations and we can outline the most interesting results as follows. (i) There is a kinematical connection between the UV and optical Fe II lines, indicating that the UV and optical Fe II lines originate from the outer part of the broad line region, so-called intermediate line region; (ii) The unexplained anticorrelations of the optical Fe II (EW Fe II$_{opt}$) versus EW [O III] 5007 Å and EW Fe II$_{opt}$ versus FWHM Hbeta have not been detected for the UV Fe II lines; (iii) The significant averaged redshift in the UV Fe II lines, which is not present in optical Fe II, indicates an inflow in the UV Fe II emitting clouds, and probably their asymmetric distribution. (iv) Also, we confirm the anticorrelation between the intensity ratio of the optical and UV Fe II lines and FWHM of Hbeta, and we find the anticorrelations of this ratio with the widths of Mg II 2800 Å, optical Fe II and UV Fe II. This indicates a very important role for the column density and microturbulence in the emitting gas. We discuss the starburst activity in high-density regions of young AGNs as a possible explanation of the detected optical Fe II correlations and intensity line ratios of the UV and optical Fe II lines.

astro-ph.GA↗