Related papers: What controls the Fe II strength in active galacti…
We present a sample of 2865 emission line galaxies with strong nebular He II 4686 emissions in Sloan Digital Sky Survey Data Release 7 and use this sample to investigate the origin of this line in star-forming galaxies. We show that…
Eigenvector 1 (EV1) was found to be the dominant component behind the significant correlations for the measured parameters in quasar spectra (Boroson & Green, 1992). The parameter R$_{\mathrm{FeII}}$, which strongly correlates to the EV1,…
In order to examine how narrow emission-line flux ratios depend on the Seyfert type, we compiled various narrow emission-line flux ratios of 355 Seyfert galaxies from the literature. We present in this paper that the intensity of the…
We present high-resolution mid-infrared (MIR) imaging, nuclear spectral energy distributions (SEDs) and archival Spitzer spectra for 22 low-luminosity active galactic nuclei (LLAGN; Lbol \lesssim 10^42 erg/sec). Infrared (IR) observations…
X-ray observations of several active galactic nuclei show prominent iron K-shell fluorescence lines that are sculpted due to special and general relativistic effects. These observations are important because they probe the space-time…
We study the relation of optical/UV and X-ray emission in the low luminosity active galactic nuclei (LLAGNs), using a sample of 49 sources including 28 local Seyfert galaxies and 21 low-ionization nuclear emission-line regions (LINERs) with…
We use near-infrared spectroscopic data from the inner few hundred parsecs of a sample of 47 active galaxies to investigate possible correlations between the stellar velocity dispersion (sigma_star), obtained from the fit of the K-band CO…
To investigate the chemical abundance of broad-line region clouds in quasars at high redshifts, we performed near-infrared spectroscopy of six luminous quasars at z ~ 2.7 with the WINERED spectrograph mounted on the New Technology Telescope…
Recently growing evidence has been accumulated that the NLS1s are viewed from nearly pole-on viewing angles. However, there has been no theoretical model which explains the following important correlations; 1) weaker optical Fe II emitters…
In this study, a refined approach for multicomponent fitting of active galactic nuclei (AGN) spectra is presented utilizing the newly developed Python code $fantasy$ (fully automated python tool for AGN spectra analysis). AGN spectra are…
We investigate the relation between the X-ray nuclear emission, optical emission line, radio luminosity and black hole mass for a sample of nearby Seyfert galaxies. Strong linear correlations between the 2-10 keV and [OIII], radio…
By means of the data sets of the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), we investigate the relationship between the variability amplitude and luminosity at 5100 \AA, black hole mass, Eddington ratio, $ R_{\rm Fe…
We introduce a new physical parameter, the optical variability amplitude, to the well-established Eigenvector 1 space of quasars and test a sample of long-term B-band light curves of 42 PG quasars monitored by Giveon et al. (1999). We find…
The origin of He II emission in galaxies remains a debated topic, requiring ionizing photons with energies exceeding 54 eV. While massive stars, such as Wolf-Rayet stars, have been considered potential sources, their UV flux often fails to…
Quasar emission lines are sensitive to both the luminosity and shape of the quasars' high energy continuum - primarily in the soft X-ray and the (obscured) extreme ultraviolet. We initiate the first large-scale, multi-line investigation of…
We investigate the variation of the ratio of the equivalent widths of the FeII$\lambda$2600 line to the MgII$\lambda\lambda$2796,2803 doublet as a function of redshift in a large sample of absorption lines drawn from the JHU-SDSS Absorption…
The great power offered by photoionization models of Active Galactic Nuclei (AGN) emission-line regions has long been mitigated by the fact that very little is known about the spectral energy distribution (SED) between the Lyman limit,…
Here we discuss the physical conditions in the emission line regions (ELR) of active galactic nuclei (AGN), with the special emphasize on the unresolved problems, e.g. the stratification of the Broad Line Region (BLR) or the failure of the…
We present an analysis of historical multi-wavelength emission of the Changing Look (CL) Active Galactic Nucleus (AGN) in NGC 2992, covering epochs ranging from 1978 to 2021, as well as new X-ray and optical spectra. The galaxy presents…
I provide a short review of the properties of Narrow-line Seyfert 1 (NLS1) galaxies across the electromagnetic spectrum and of the models to explain them. Their continuum and emission-line properties manifest one extreme form of Seyfert…