Related papers: An automated activity classification tool for opti…
We present a sample of 252 broad-line Active Galactic Nuclei (BLAGNs), incorporating 171 newly identified sources, spanning a redshift interval from $z$ = 0.8 to 7.2. We have analyzed spectroscopic data from the NIRSpec instrument aboard…
We use 317,000 emission-line galaxies from the Sloan Digital Sky Survey to investigate line-ratio selection of active galactic nuclei (AGNs). In particular, we demonstrate that "star formation dilution" by HII regions causes a significant…
A large fraction of active galactic nuclei (AGN) are "invisible" in extant optical surveys due to either distance or dust-obscuration. The existence of this large population of dust-obscured, infrared-bright AGN is predicted by models of…
Low-luminosity active galactic nuclei (LLAGN; $L_{\rm bol} < 10^{42}$~erg~s$^{-1}$) may comprise a significant fraction of the local AGN population, yet their weak emission makes them difficult to detect. In this paper, we analyse 38 LLAGN…
We present a method to identify type-1 active galactic nuclei (AGN) in the central 3 arcsec integrated spectra of galaxies in the MaNGA DR15 sample. It is based on flux ratios estimates in spectral bands flanking the expected H$\alpha$…
The discovery of the M-sigma relation, the local galaxy bimodality, and the link between black-hole and host-galaxy properties, have raised the question whether AGN play a role in galaxy evolution. Several theoretical models implement AGN…
We present an analysis of the host properties of 85224 emission-line galaxies from the Sloan Digital Sky Survey. We show that Seyferts and LINERs form clearly separated branches on the standard optical diagnostic diagrams. We derive a new…
Using the Gemini Near-InfraRed Spectrograph (GNIRS), we have assembled a complete sample of 20 K-selected galaxies at 2.0<z<2.7 with high quality near-infrared spectra. As described in a previous paper, 9 of these 20 galaxies have strongly…
Under the unified model for active galactic nuclei (AGNs), narrow-line (Type 2) AGNs are, in fact, broad-line (Type 1) AGNs but each with a heavily obscured accretion disk. We would therefore expect the optical continuum emission from Type…
Context.- This paper is part of a series involving the AMIGA project (Analysis of the Interstellar Medium of Isolated GAlaxies), which identifies and studies a statistically-significant sample of the most isolated galaxies in the northern…
We propose near-infrared colour selection criteria to extract Active Galactic Nuclei (AGNs) using the near-infrared Colour-Colour Diagram (CCD) and predict near-infrared colour evolution with respect to redshift. First, we cross-identify…
This study explores the space density and properties of active galaxies to z=0.8. We have investigated the frequency and nature of unresolved nuclei in galaxies at moderate redshift as indicators of nuclear activity such as Active Galactic…
The incidence and properties of Active Galactic Nuclei (AGN) in the field, groups, and clusters can provide new information about how these objects are triggered and fueled, similar to how these environments have been employed to study…
Optical emission-line diagnostic diagrams, such as the classical BPT, are widely used to identify ionisation mechanisms in galaxies but often suffer from degeneracies, especially when multiple sources coexist. We critically evaluate the…
Classifying Active Galactic Nuclei (AGN) is a challenge, especially for BL Lac Objects (BLLs), which are identified by their weak emission line spectra. To address the problem of classification, we use data from the 4th Fermi Catalog, Data…
Context. Galactic halos host faint substructures, such as stellar streams and shells, which provide insights into the hierarchical assembly history of galaxies. To date, such features have been identified in external galaxies by visual…
Reliably identifying active galactic nuclei (AGNs) in dwarf galaxies is key to understanding black hole demographics at low masses and constraining models for black hole seed formation. Here we present Chandra X-ray Observatory observations…
In this paper we present a classification of emission-line galaxies at intermediate and high redshifts (0.52.5 for near-infrared spectra), using the Dn(4000) index as a supplementary diagnostic. Our goal is to complement the diagnostic…
A review of the spectroscopic tools needed to characterize AGNs is presented. This review focusses on ultraviolet, optical and infrared emission-line diagnostics specifically designed to help differentiate AGNs from starburst-dominated…
This work presents the first results of the Deep IFS View of Nuclei of Galaxies (DIVING$^\mathrm{3D}$) survey. We analysed the nuclear emission-line spectra of a sub-sample we call mini-DIVING$^\mathrm{3D}$, which includes all Southern…