Related papers: The Luminosity function of Narrow-Line Seyfert gal…
This is the first paper in a series dedicated to the study of the emission-line and continuum properties of narrow line Seyfert 1 galaxies (NLS1s). We carried out a systematic search for NLS1s from objects assigned as ``QSOs'' or…
Aims. We present results of a comprehensive spectral study on the large-scale environment of AGNs based on Sloan Spectroscopic Survey data. Methods. We analyzed the spectra of galaxies in the environment of AGN and other activity classes up…
We present a sample of 150 narrow-line Seyfert 1s (NLS1s) found within the Sloan Digital Sky Survey Early Data Release (EDR), only two of which were previously identified as such. This substantially increases the known number of NLS1s, and…
We present Chandra observations of 17 optically-selected, X-ray weak narrow-line Seyfert 1 (NLS1) galaxies. These objects were optically identified by Williams et al. (2002) in the Sloan Digital Sky Survey Early Data Release, but were not…
It is not yet well known whether narrow line Seyfert 1 (NLS1) galaxies follow the $M_{BH} - \sigma_{\star}$ relation found for normal galaxies. Emission lines, such as [SII] or [OIII]$\lambda$5007, have been used as a surrogate of the…
(abridged) A detailed comparison is performed of the LFs compiled at infrared, radio and optical wavelengths and converted into XLFs using available relations with the XLF directly estimated in the 0.5--2 keV energy band from X-ray surveys…
Several studies indicate that radio-loud (RL) Active Galactic Nuclei (AGN) are produced only by the most massive black holes (BH), $M_{\rm BH} \sim 10^8$-$10^{10} M_\odot$. This idea has been challenged by the discovery of RL Narrow Line…
Narrow-line Seyfert 1 galaxies (NLS1s) are active galactic nuclei (AGN) recently identified as a new class of $\gamma$-ray sources. The high energy emission is explained by the presence of a relativistic jet observed at small angles, just…
Narrow-line Seyfert 1 galaxies are identified by their uniform optical spectral properties. Studies of samples of NLS1s reveal, however, a range of X-ray spectral and variability behavior, and UV spectral behavior. We describe the range of…
In this letter we present clear evidence that Mrk 573 is an obscured Narrow-Line Seyfert 1 (NLSy1) and not an archetypal Seyfert 2, as it has been classified until now. Only three galaxies have been proposed as members of this class, prior…
The Zwicky Transient Facility (ZTF), with its extensive optical monitoring capabilities, has provided an unprecedented opportunity to study the long-term variability of active galactic nuclei (AGNs). In this work, we present a comparative…
We have selected a sample of 292 SDSS Narrow-Emission-Line galaxies known to have formed and evolved in relative isolation to study the nature and origin of the AGN phenomenon. The galaxies in our sample have line fluxes with S/N>3 and were…
We present a comprehensive spectroscopic and variability-based characterisation of a sample of low-luminosity active galactic nuclei (AGNs) hosting low mass black holes, identified by $H\beta$ full width at half maximum (FWHM) $< 2200$ km…
We present the X-ray luminosity function (XLF) for clusters of galaxies derived from the RASS1 Bright Sample. The sample, selected from the ROSAT All-Sky Survey in a region of 2.5 sr within the southern Galactic cap, contains 130 clusters…
We present the first X-ray Luminosity Function (XLF) for an optically-selected sample of 49 nearby poor clusters of galaxies and a sample of 67 Abell clusters with z < 0.15. We have extended the measured cluster XLF by more than a factor of…
As the third paper of our serial studies that are aim at examining the AGN-host coevolution by using partially obscured AGNs, we extend the broad-line composite galaxies (composite AGNs) into ROSAT-selected Seyfert 1.8/1.9 galaxies basing…
We present a new accurate catalog of narrow-line Seyfert 1 galaxies (NLS1s) in the southern hemisphere from the Six-degree Field Galaxy Survey (6dFGS) final data release, which is currently the most extensive spectroscopic survey available…
We analyzed a large sample of SDSS spectra of Seyfert galaxies, subdividing Seyfert 1s based on their narrow-to-broad Halpha components. Comparing their narrow-lines (NL) to Seyfert2s in line-ratio diagrams, most of the NL of strong Sy 1.0…
The Sloan Digital Sky Survey [SDSS] has measured an optical luminosity function for galaxies in 5 bands, finding 1.5 to 2.1 times more luminosity density than previous work. This note compares the SDSS luminosity density to two recent…
We compare optical and hard X-ray identifications of AGNs using a uniformly selected (above a flux limit of f_2-8 keV = 3.5e-15 erg/cm2/s) and highly optically spectroscopically complete ( > 80% for f_2-8 keV > 1e-14 erg/cm2/s and > 60%…