Jump to main content Jump to site navigation Jump to section navigation
Jodrell Bank Centre for Astrophysics

Our Research

Active Galaxies Newsletter

An electronic publication dedicated to the observations and theory of active galaxies
Edited by Melanie Gendre

The Active Galaxies Newsletter is an electronic publication dedicated to the observation and theory of active galaxies. It is intended to be used to notify others in the field of recently accepted papers, conference proceedings and dissertations, and also contains announcements of jobs and conferences. It is produced monthly and sent to over 600 subscribers.

The Latex macros for submitting contributions of all sorts is available here and are also appended to each issue of the newsletter.

Information and web-links for upcoming meetings, conferences, jobs and special announcements, as well as recent thesis abstracts can now be directly linked to on the left hand side bar. These pages are updated throughout the month as soon as adverts and announcements are received. To advertise forthcoming job opportunities and meetings please email the editor with the relevant information. These adverts are also run in newsletter itself.

If you wish to be sent the newsletter, please send an email to agnews@manchester.ac.uk entitled `subscribe'. Available below are the latest editions and archives of the active galaxies newsletter.

Further information on the Active Galaxies Newsletter and submitting contributions or subscribing is available here.

While astro-ph is a valuable resource, the Active Galaxies Newsletter directly targets researchers in this field and in this sense is a complementary resource.

Latest Issue:

Active An electronic publication dedicated to
Galaxies the observation and theory of
Newsletter active galaxies
No. 192 -- MARCH 2013 Editor: Melanie Gendre (agnews@manchester.ac.uk)

Accepted Abstracts - Submitted Abstracts - Thesis Abstracts
Jobs Adverts - Meetings Adverts - Special Announcements

From the Editor

The Active Galaxies Newsletter is produced monthly. The deadline for contributions is the last day of the month. The Latex macros for submitting abstracts and dissertation abstracts are appended to each issue of the newsletter and are also available on the web page.

As always as editor of the newsletter I am very interested to hear any suggestions or feedback regarding the newsletter. So do not hesitate in emailing me your suggestions.

Many thanks for your continued subscription.

Melanie Gendre



Abstracts of recently accepted papers


Polarized extended Lyα emission from a z=2.3 radio galaxy

A. Humphrey1, J. Vernet2, M. Villar-Martín3, S. di Serego Alighieri4, R.A.E. Fosbury2, A. Cimatti5

1Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762, Porto, Portugal
2European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany
3Centro de Astrobiología (INTA-CSIC), Carretera de Ajalvir, km 4, 28850 Torrejón de Ardoz, Madrid, Spain
4INAF-Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, 50125 Firenze, Italy
5Dipartimento di Astronomia, Università di Bologna, Via Ranzani 1, I-40127 Bologna, Italy

We present spatially resolved spectropolarimetic measurements of the 100-kpc scale gaseous environment of the z=2.34 radio galaxy TXS 0211-122. The polarization level of the narrow Lyα emission is low centrally (P<5 %), but rises to P=16.4±4.6 % in the Eastern part of the nebula, indicating that the nebula is at least partly powered by the scattering of Lyα photons by HI. Not only is this the first detection of polarized Lyα around a radio-loud active galaxy, it is also the second detection to date for any kind of Lyα nebula. We also detect a pair of diametrically opposed UV continuum sources along the slit, at the outer edges of the Lyα nebula, which we suggest may be the limb of a dusty shell, related to the large-scale HI absorbers often associated with high-z radio galaxies.

Accepted by Astrophysical Journal Letters.

E-mail contact: andrew.humphrey@astro.up.pt,
preprint available at arXiv:1302.2813


An HST/WFC3-UVIS View of the Starburst in the Cool Core of the Phoenix Cluster

Michael McDonald1, Bradford Benson2, Sylvain Veilleux3, Marshall W. Bautz1, and Christian L. Reichardt4

1 Kavli Institute for Astrophysics and Space Research, MIT, Cambridge, MA 02139, USA
2 Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
3 Department of Astronomy, University of Maryland, College Park, MD 20742, USA
4 Department of Physics, University of California, Berkeley, CA 94720, USA

We present Hubble Space Telescope Wide Field Camera 3 observations of the core of the Phoenix Cluster (SPT-CLJ2344-4243) in five broadband filters spanning rest-frame 1000-5500Å. These observations reveal complex, filamentary blue emission, extending for >40 kpc from the brightest cluster galaxy. We observe an underlying, diffuse population of old stars, following an r1/4 distribution, confirming that this system is somewhat relaxed. The spectral energy distribution in the inner part of the galaxy, as well as along the extended filaments, is a smooth continuum and is consistent with that of a star-forming galaxy, suggesting that the extended, filamentary emission is not due to the central AGN, either from a large-scale ionized outflow or scattered polarized UV emission, but rather a massive population of young stars. We estimate an extinction-corrected star formation rate of 798 ± 42 M☉ yr-1, consistent with our earlier work based on low spatial resolution ultraviolet, optical, and infrared imaging. The lack of tidal features and multiple bulges, combine with the need for an exceptionally massive (>1011 M☉) cold gas reservoir, suggest that this star formation is not the result of a merger of gas-rich galaxies. Instead, we propose that the high X-ray cooling rate of ∼2700 M☉ yr-1 is the origin of the cold gas reservoir. The combination of such a high cooling rate and the relatively weak radio source in the cluster core suggests that feedback has been unable to halt cooling in this system, leading to this tremendous burst of star formation.

Accepted by ApJ Letters

E-mail contact: mcdonald@space.mit.edu,
preprint available at arXiv:1211.7058


Luminosity-dependent unification of Active Galactic Nuclei and the X-ray Baldwin effect

C. Ricci1,2,3, S. Paltani1,2, H. Awaki4, P.-O. Petrucci5, Y. Ueda3, and M. Brightman6

1 ISDC Data Centre for Astrophysics, Université de Genève, ch. d'Ecogia 16, 1290 Versoix, Switzerland
2 Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290 Versoix, Switzerland
3 Department of Astronomy, Kyoto University, Oiwake-cho, Sakyo-ku, Kyoto 606-8502
4 Department of Physics, Ehime University, Matsuyama, 790-8577, Japan
5 UJF-Grenoble 1 / CNRS-INSU, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG) UMR 5274, Grenoble, F-38041, France
6 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748, Garching bei München, Germany

The existence of an anti-correlation between the equivalent width (EW) of the narrow core of the iron Kα line and the luminosity of the continuum (i.e. the X-ray Baldwin effect) in type-I active galactic nuclei has been confirmed over the last years by several studies carried out with XMM-Newton, Chandra and Suzaku. However, so far no general consensus on the origin of this trend has been reached. Several works have proposed the decrease of the covering factor of the molecular torus with the luminosity (in the framework of the luminosity-dependent unification models) as a possible explanation for the X-ray Baldwin effect. Using the fraction of obscured sources measured by recent X-ray and IR surveys as a proxy of the half-opening angle of the torus, and the recent Monte-Carlo simulations of the X-ray radiation reprocessed by a structure with a spherical-toroidal geometry by Ikeda et al. (2009) and Brightman & Nandra (2011), we test the hypothesis that the X-ray Baldwin effect is related to the decrease of the half-opening angle of the torus with the luminosity. Simulating the spectra of an unabsorbed population with a luminosity-dependent covering factor of the torus as predicted by recent X-ray surveys, we find that this mechanism is able to explain the observed X-ray Baldwin effect. Fitting the simulated data with a log-linear L2-10keV-EW relation, we found that in the Seyfert regime (L2-10keV≤ 1044.2erg s-1) luminosity-dependent unification produces a slope consistent with the observations for average values of the equatorial column densities of the torus of log NHT≥ 23.1, and can reproduce both the slope and the intercept for log NHT≃ 23.2. Lower values of NHT are obtained considering the decrease of the covering factor of the torus with the luminosity extrapolated from IR observations (22.9 ≤ log NHT≤ 23). In the quasar regime (L2-10keV> 1044.2 erg s-1) a decrease of the covering factor of the torus with the luminosity slower than that observed in the Seyfert regime (as found by recent hard X-ray surveys) is able to reproduce the observations for 23.2≤ log NHT≤24.2.

Accepted by Astronomy & Astrophysics

E-mail contact: ricci@kusastro.kyoto-u.ac.jp,
preprint available at arXiv:1302.1070


The Chandra-COSMOS survey IV: X-ray spectra of the bright sample

G. Lanzuisi1,2,3, F. Civano2, M. Elvis2, M. Salvato1, G. Hasinger4, C. Vignali5,6, G. Zamorani6, T. Aldcroft2, M. Brusa5,6,1, A. Comastri6, F. Fiore7, A. Fruscione2, R. Gilli6, L. C. Ho8, V. Mainieri9, A. Merloni1, A. Siemiginowska2

1Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 85748 Garching, Germany
2Harvard-Smithsonian Center for Astrophysics, 60 Garden St. Cambridge, MA 02138.
3Technische Universität München, Fakultät für Physik, James-Franck-Str. 1 85748 Garching, Germany
4Institute for Astronomy, 2680 Woodlawn Drive Honolulu, HI 96822-1839 USA
5Dipartimento di Astronomia, Università degli Studi di Bologna, Via Ranzani 1, I-40127 Bologna, Italy
6INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna, Italy
7Osservatorio Astronomico di Roma (INAF), Via Frascati 33, I-00040 Monteporzio Catone, Italy
8The Observatories of the Carnegie Institute for Science, Santa Barbara Street, Pasadena, CA 91101, USA
9ESO Headquarters Karl-Schwarzschild-Str. 2 85748 Garching bei Mnchen Germany

We present the X-ray spectral analysis of the 390 brightest extragalactic sources in the Chandra-COSMOS catalog, showing at least 70 net counts in the 0.5-7 keV band. This sample has a 100% completeness in optical-IR identification, with ∼75% of the sample having a spectroscopic redshift and ∼25% a photometric redshift. Our analysis allows us to accurately determine the intrinsic absorption, the broad band continuum shape (Γ) and intrinsic L2-10 keV distributions, with an accuracy better than 30% on the spectral parameters for 95% of the sample. The sample is equally divided in type-1 (49.7%) and type-2 AGN (48.7%) plus few passive galaxies at low z. We found a significant difference in the distribution of Γ of type-1 and type-2, with small intrinsic dispersion, a weak correlation of Γ with L2-10 keV and a large population (15% of the sample) of high luminosity, highly obscured (QSO2) sources. The distribution of the X-ray/Optical flux ratio (Log(FX/Fi)) for type-1 is narrow (0<X/O<1), while type-2 are spread up to X/O=2. The X/O correlates well with the amount of X-ray obscuration. Finally, a small sample of Compton thick candidates and peculiar sources is presented. In the appendix we discuss the comparison between Chandra and XMM-Newton spectra for 280 sources in common. We found a small systematic difference, with XMM-Newton spectra that tend to have softer power-laws and lower obscuration.

Accepted by MNRAS, February 5, 2013.

E-mail contact: giolanzu@mpe.mpg.de,
preprint available at arXiv:1302.1062


The Origin of Dust in Early-Type Galaxies and Implications for Accretion onto Supermassive Black Holes

Paul Martini1,2, Daniel Dicken3, Thaisa Storchi-Bergmann4

1 Department of Astronomy and Center for Cosmology and Astroparticle Physics, The Ohio State University, Columbus, OH, USA
2 Visiting Astronomer, North American ALMA Science Center and University of Virginia, Charlottesville, VA, USA
3 Institut de Astrophysique Spatiale, Paris, France
4 Instituto de Física, Universidade Federal do Rio Grande do Sul, Brazil

We have conducted an archival Spitzer study of 38 early-type galaxies in order to determine the origin of the dust in approximately half of this population. Our sample galaxies generally have good wavelength coverage from 3.6μm to 160μm, as well as visible-wavelength HST images. We use the Spitzer data to estimate dust masses, or establish upper limits, and find that all of the early-type galaxies with dust lanes in the HST data are detected in all of the Spitzer bands and have dust masses of ∼ 105-6.5 M☉, while galaxies without dust lanes are not detected at 70μm and 160μm and typically have <105 M☉ of dust. The apparently dust-free galaxies do have 24μm emission that scales with the shorter wavelength flux, yet substantially exceeds the expectations of photospheric emission by approximately a factor of three. We conclude this emission is dominated by hot, circumstellar dust around evolved stars that does not survive to form a substantial interstellar component. The order of magnitude variations in dust masses between galaxies with similar stellar populations rules out a subtantial contribution from continual, internal production in spite of the clear evidence for circumstellar dust. We demonstrate that the interstellar dust is not due to purely external accretion, unless the product of the merger rate of dusty satellites and the dust lifetime is at least an order of magnitude higher than expected. We propose that dust in early-type galaxies is seeded by external accretion, yet the accreted dust is maintained by continued growth in externally-accreted cold gas beyond the nominal lifetime of individual grains. The several Gyr depletion time of the cold gas is long enough to reconcile the fraction of dusty early-type galaxies with the merger rate of gas-rich satellites. As the majority of dusty early-type galaxies are also low-luminosity Active Galactic Nuclei and likely fueled by this cold gas, their lifetime should similarly be several Gyr.

Accepted by The Astrophysical Journal

E-mail contact: martini@astronomy.ohio-state.edu
preprint available at arxiv:1302.5124


The Black Hole and Central Stellar Population of MCG-6-30-15

S. I. Raimundo1, R. I. Davies2, P. Gandhi3, A. C. Fabian4, R. E. A Canning4, and V. D. Ivanov5

1SISSA - International School for Advanced Studies, via Bonomea, 265, 34136 Trieste, Italy
2Max-Planck-Institut für extraterrestrische Physik, 85741 Garching, Germany
3Institute of Space and Astronautical Science (ISAS), JAXA, 3-1-1 Yoshinodai, chuo-ku, Sagamihara, Kanagawa 229-8510, Japan
4Institute of Astronomy, Madingley Road, Cambridge CB3 0HA
5European Southern Observatory, Ave. Alonso de Cordova 3107, Vitacura, Santiago 19001, Chile

We present the first near-infrared integral field spectroscopy observations of the galaxy MCG-6-30-15. The H-band data studied in this paper cover the central 500pc of the galaxy at the best resolution (0''.1) so far. The spectra of the innermost regions are dominated by broad brackett series emission lines and non-stellar continuum, under which we are able to trace the distribution and kinematics of the stars and also the [FeII] line emission. We find that there is a counter-rotating stellar core extending out to 125pc, which appears to be associated with the [FeII] emission. Based on the mass-to-light ratio, and the presence of this emission line, we estimate the age of the central stellar population to be of order of 65Myr. We show that the gas needed to fuel the black hole is, at most, only 1 per cent of that needed to form these stars. We derive independent constraints on the black hole mass using the dynamical information and determine an upper limit for the black hole mass, MBH < 6× 107M☉, that is consistent with other estimates.

Accepted by MNRAS

E-mail contact: sandra.raimundo@sissa.it,
preprint available at arxiv:1302.5116


Meetings


The restless nature of AGNs: variability as a probe of the central engine
Naples, Italy, 20-23 May 2013



*Scientific rationale: *
It is widely accepted that variability provides important information on the nature of the emission mechanisms and the geometry of the central source in Active Galactic Nuclei. This is an exciting time in the field of AGN variability, due to the wealth of new results produced in the last few years. This conference intends to focus on *radio-quiet* sources, discussing our current understanding of the central source variability across the IR, optical, and UV regimes up to hard X-rays, and the clues that variability provides about the physics and structure of the AGN phenomena. The contributions are intended to address the problem of AGN variability both from the observational and theoretical point of view, on short and long time scales, presenting results and expectations from wide-field/deep surveys, pointed observations, ground-based and space observatories.

The *topics* will include:

More information, including instructions for registration and abstract submission, are available at the website: http://astrofisica.na.infn.it/restlessAGN

IMPORTANT DATES
January 16 2013: Registration Opens
March 24 2013: Registration Closes
April 7 2013: Schedule announced
May 20-23 2013: Conference