Related papers: NGC 4151 - A unified active galactic nucleus
Active Galactic Nuclei (AGN) are promising candidate sources of high-energy astrophysical neutrinos since they provide environments rich in matter and photon targets where cosmic ray interactions may lead to the production of gamma rays and…
NGC 4151, a nearby Seyfert galaxy, has recently been reported to emit gamma rays in the GeV range, posing an intriguing astrophysical mystery. The star formation rate of NGC 4151 is too low to explain the observed GeV flux, but the galaxy…
In Unification Models, Active Galactic Nuclei (AGN) are believed to be surrounded by an axisymmetric structure of dust and gas, which greatly influences their observed properties according to the direction from which they are observed. The…
NGC 4151 is the brightest Seyfert-1 active galaxy in the pass band of the Resolve calorimeter spectrometer aboard XRISM. It has been observed on 14 occasions, resulting in a total exposure of 893 ks. Herein, we report on an analysis of the…
We use X-ray observations of three galaxies hosting LINERs (NGC 404, NGC 4736, NGC 4579) with Chandra to study their power sources. We find very diverse properties within this small group: NGC 404 has an X-ray-faint nucleus with a soft,…
We present {\it Gemini} longslit optical spectroscopy and VLA radio observations of the nuclear region of NGC 4178, a late-type bulgeless disk galaxy recently confirmed to host an AGN through infrared and X-ray observations. Our…
We draw attention to some intriguing coincident patterns in the optical light curves of NGC 4151 and NGC 5548. Inspecting the light curves of these two classic Seyferts, we find evidence for at least five occurrences of a similar sequence…
We probe the dusty environment of the archetypical type-1 AGN in NGC 4151 with comprehensive IR reverberation mapping over several decades, in J ($\sim1.22\mu$m), H ($\sim1.63\mu$m), K ($\sim2.19\mu$m), L ($\sim3.45\mu$m) and N-band…
How do active galactic nuclei with low optical luminosities produce powerful radio emission? Recent studies of active galactic nuclei with moderate radio and low optical luminosities (Fanaroff & Riley class I, FR I) searching for broad…
We have used the Wide Field Planetary Camera 2 aboard the Hubble Space Telescope to image the compact star cluster nuclei of the nearby, late-type, low-luminosity spiral galaxies NGC 4395, NGC 4242, and ESO 359-029. We also analyze archival…
The sub-parsec masing disk recently found to be orbiting a central mass of $\sim3.6\times10^7$~\msun\ in the Seyfert/LINER galaxy NGC~4258 provides the most compelling evidence to date for the existence of a massive black hole in the…
NGC 6337 is a member of the rare group of planetary nebulae where a close binary nucleus has been identified. The nebula's morphology and emission line profiles are both unusual, particularly the latter. We present a thorough mapping of…
We present the detection of nuclear stellar discs in the low-luminosity elliptical galaxies NGC 4458 and NGC 4478, which are known to host a kinematically-decoupled core. Using archival HST imaging, and available absorption line-strength…
We studied the physical parameters of a sample comprising of all Spitzer/IRS public spectra of Seyfert galaxies in the mid-infrared (5.2-38$\mu$m range) under the active galactic nuclei (AGN) unified model. We compare the observed spectra…
We present a spectroscopic and imaging study of an abnormal active galactic nucleus (AGN), 2MASX J00423991+3017515. This AGN is newly identified in the hard X-rays by the Swift BAT All-Sky survey and found in an edge-on disk galaxy…
We show that the sharp cutoff in the hard X-ray spectrum of NGC 4151, unusual for Seyfert 1 galaxies, can be reconciled with the average Seyfert 1 spectrum if we assume that the central source is completely hidden from our line of sight by…
Recent astronomical observations reveal that Active Galactic Nuclei (AGN) are sources of high-energy radiation. For example, the Fermi-LAT and Hess telescopes have detected gamma-ray emissions from the cores of several types of AGN's. Even…
We utilize the complimentary capabilities of XMM-Newton and Chandra, to conduct a detailed imaging and spectral study of the nearby galaxy NGC 4945 focussing on its nucleus and immediate surroundings (within ~1 kpc of the nucleus). A…
A hot, dusty torus located around the outer edge of the broad-line region of AGNs is a fundamental ingredient in unified AGN models. While the existence of circumnuclear dust around AGNs at pc-scale radii is now widely accepted, questions…
We report high resolution imaging of the nucleus of the Seyfert 1 galaxy NGC 4151 obtained with a 50 ks Chandra HRC observation. The HRC image resolves the emission on spatial scales of 0.5", ~30 pc, showing an extended X-ray morphology…