* Astronomy

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UGC 7166

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RE: NGC 4151

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PGC 38739

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RE: NGC 4151

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Title: The First Spectroscopically Resolved Sub-parsec Orbit of a Supermassive Binary Black Hole
Authors: E. Bon, P. Jovanovic, P. Marziani, A. I. Shapovalova, N. Bon, V. Borka Jovanovic, D. Borka, J. Sulentic, L. C. Popovic

One of the most intriguing scenarios proposed to explain how active galactic nuclei are triggered involves the existence of a supermassive binary black hole system in their cores. Here we present an observational evidence for the first spectroscopically resolved sub-parsec orbit of a such system in the core of Seyfert galaxy NGC 4151. Using a method similar to those typically applied for spectroscopic binary stars we obtained radial velocity curves of the supermassive binary system, from which we calculated orbital elements and made estimates about the masses of components. Our analysis shows that periodic variations in the light and radial velocity curves can be accounted for an eccentric, sub-parsec Keplerian orbit of a 15.9-year period. The flux maximum in the lightcurve correspond to the approaching phase of a secondary component towards the observer. According to the obtained results we speculate that the periodic variations in the observed H{\alpha} line shape and flux are due to shock waves generated by the supersonic motion of the components through the surrounding medium. Given the large observational effort needed to reveal this spectroscopically resolved binary orbital motion we suggest that many such systems may exist in similar objects even if they are hard to find. Detecting more of them will provide us with insight into black hole mass growth process.

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X-ray 'Echoes' Map a Supermassive Black Hole's Extreme Neighbourhood

An international team of astronomers, led by the University of Maryland, has identified a long-sought X-ray "echo" at the center of the active galaxy NGC 4151. This finding promises to give scientists an unprecedented window into what happens at the fringes of such monster black holes.
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Title: A Deep Chandra ACIS Study of NGC 4151. III. the Line Emission and Spectral Analysis of the Ionisation Cone
Authors: Junfeng Wang, Giuseppina Fabbiano, Martin Elvis, Guido Risaliti, Margarita Karovska, Andreas Zezas, Carole G. Mundell, Gaelle Dumas, Eva Schinnerer

This paper is the third in a series in which we present deep Chandra ACIS-S imaging spectroscopy of the Seyfert 1 galaxy NGC 4151, devoted to study its complex circum-nuclear X-ray emission. Emission features in the soft X-ray spectrum of the bright extended emission (L[0.3-2keV]~10^40 erg/s) at r>130 pc (2") are consistent with the brighter OVII, OVIII, and NeIX lines seen in the Chandra HETGS and XMM-Newton RGS spectra below 2 keV. We construct emission line images of these features and find good morphological correlations with the narrow line region clouds mapped in [OIII]5007A. Self-consistent photoionisation models provide good descriptions of the spectra of the large scale emission, as well as resolved structures, supporting the dominant role of nuclear photoionisation, although displacement of optical and X-ray features implies a more complex medium. Collisionally ionised emission is estimated to be <12% of the extended emission. Presence of both low and high ionisation spectral components and extended emission in the X-ray image perpendicular to the bicone indicates leakage of nuclear ionisation, likely filtered through warm absorbers, instead of being blocked by a continuous obscuring torus. The ratios of [OIII]/soft X-ray flux are approximately constant (~15) for the 1.5 kpc radius spanned by these measurements, indicating a relatively constant ionisation parameter, consistent with the photoionise outflow of a wind-like density profile. Using spatially resolved features, we estimate that the mass outflow rate in NGC 4151 is ~2Msun/yr at 130 pc and the kinematic power of the ionised outflow is 1.7x10^41 erg/s, approximately 0.3% of the bolometric luminosity of NGC 4151.

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NGC 4151: An Active Black Hole in the "Eye of Sauron"

Credit: X-ray: NASA/CXC/CfA/J.Wang et al.; Optical: Isaac Newton Group of Telescopes, La Palma/Jacobus Kapteyn Telescope, Radio: NSF/NRAO/VLA

This composite image shows the central region of the spiral galaxy NGC 4151, dubbed the "Eye of Sauron" by astronomers for its similarity to the eye of the malevolent character in "The Lord of the Rings". In the "pupil" of the eye, X-rays (blue) from the Chandra X-ray Observatory are combined with optical data (yellow) showing positively charged hydrogen ("H II") from observations with the 1-meter Jacobus Kapteyn Telescope on La Palma. The red around the pupil shows neutral hydrogen detected by radio observations with the NSF's Very Large Array. This neutral hydrogen is part of a structure near the centre of NGC 4151 that has been distorted by gravitational interactions with the rest of the galaxy, and includes material falling towards the centre of the galaxy. The yellow blobs around the red ellipse are regions where star formation has recently occurred.

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An international team of scientists has observed four super-massive black holes at the center of galaxies, which may provide new information on how these central black hole systems operate. Their findings are published in Decembers first issue of the journal Astronomy and Astrophysics.
These super-massive black holes at the center of galaxies are called active galactic nuclei. For the first time, the team observed a quasar with an active galactic nucleus, as part of the group of four, which is located more than a billion light years from Earth. The scientists used the two Keck telescopes on top of Mauna Kea in Hawaii. These are the largest optical/infrared telescopes in the world.

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An international research team has taken a deep look into the shape and geometry of the accreting material around the black hole in nearby Active Galactic Nuclei (AGN).
The team, led by Makoto Kishimoto from the Max Planck Institute for Radio Astronomy in Bonn, combined infrared imaging from the United Kingdom Infrared Telescope (UKIRT) and some of the first ever infrared long-baseline interferometric measurements from the Keck Observatory to observe the nearby AGN.
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