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Active Galaxies Newsletter

An electronic publication dedicated to the observations and theory of active galaxies
Edited by Megan Argo

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. The editor may reject submissions which do not use the template.

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. 218 -- December 2015 Editor: Megan Argo (agnews@manchester.ac.uk)

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

From the Editor

Welcome to all the new subscribers, thanks to everyone who contributed to this issue of the Active Galaxies Newsletter, and apologies for the slight delay in the publication of this month's issue.

This newsletter is intended to disseminate paper abstracts, meeting announcements, job adverts and other information which may be of interest to the active galaxies community. It is produced monthly and, whilst the deadline for contributions is the last day of the month, contributions may be submitted at any time.

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. Please note that the editor may reject submissions which do not use the template. As always, any suggestions or feedback regarding the newsletter are welcome.

Thanks for your continued subscription.

Megan Argo



Abstracts of recently accepted papers



Monitoring of GAmma-ray Bright AGN: The Multi-frequency Polarization of the Flaring Blazar 3C 279 *

Sincheol Kang1,2, Sang-Sung Lee1,2 and Do-Young Byun1,2

1. Korea Astronomy and Space Science Institute, 776 Daedeok-daero, Yuseong, Daejeon 34055, Republic of Korea
2. University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea
* Part of a special issue on the Korean VLBI Network (KVN)

We present results of long-term multi-wavelength polarization observations of the powerful blazar 3C 279 after its γ-ray flare on 2013 December 20. We followed up this flare with single-dish polarization observations using two 21-m telescopes of the Korean VLBI Network. Observations carried out weekly from 2013 December 25 to 2015 January 11, at 22 GHz, 43 GHz, 86 GHz simultaneously, as part of the Monitoring Of GAmma-ray Bright AGN (MOGABA) program. We measured 3C 279 total flux densities of 22-34 Jy at 22 GHz, 15-28 Jy (43 GHz), and 10-21 Jy (86 GHz), showing mild variability of ≤ 50% over the period of our observations. The spectral index between 22 GHz and 86 GHz ranged from -0.13 to -0.36. Linear polarization angles were 27°-38°, 30°-42°, and 33°-50° at 22 GHz, 43 GHz, and 86 GHz, respectively. The degree of linear polarization was in the range of 6-12%, and slightly decreased with time at all frequencies. We investigated Faraday rotation and depolarization of the polarized emission at 22-86 GHz, and found Faraday rotation measures (RM) of -300 to -1200 rad m-2 between 22 GHz and 43 GHz, and -800 to -5100 rad m-2 between 43 GHz and 86 GHz. The RM values follow a power law with a mean power law index a of 2.2, implying that the polarized emission at these frequencies travels through a Faraday screen in or near the jet. We conclude that the regions emitting polarized radio emission may be different from the region responsible for the 2013 December γ-ray flare and are maintained by the dominant magnetic field perpendicular to the direction of the radio jet at milliarcsecond scales.

Accepted by J. Korean Astron. Soc.

E-mail contact: sslee@kasi.re.kr
Preprint available at http://arxiv.org/abs/1511.01621


On the relation of optical obscuration and X-ray absorption in Seyfert galaxies

L. Burtscher1, R. I. Davies1, J. Graciá-Carpio1, M. J. Koss2, M.-Y. Lin1, D. Lutz1, P. Nandra1, H. Netzer3, G. Orban de Xivry1, C. Ricci4, D. J. Rosario1, S. Veilleux5,6, A. Contursi1, R. Genzel1, A. Schnorr-Müller1, A. Sternberg7, E. Sturm1 and L. J. Tacconi1

1. Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, Gießenbachstr., 85741 Garching, Germany
2. Institute for Astronomy, Department of Physics, ETH Zürich, Wolfgang-Pauli-Strasse 27, CH-8093 Zürich, Switzerland
3. School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel
4. Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, 306, Santiago 22, Chile
5. Department of Astronomy, University of Maryland, College Park, MD 20742, USA
6. Joint Space-Science Institute, University of Maryland, College Park, MD 20742, USA
7. Raymond and Beverly Sackler School of Physics & Astronomy, Tel Aviv University, Ramat Aviv 69978, Israel

The optical classification of a Seyfert galaxy and whether it is considered X-ray absorbed are often used interchangeably. But there are many borderline cases and also numerous examples where the optical and X-ray classifications appear to be in conflict. In this article we re-visit the relation between optical obscuration and X-ray absorption in AGNs. We make use of our "dust color" method (Burtscher et al. 2015a) to derive the optical obscuration AV and consistently estimated X-ray absorbing columns using 0.3-150 keV spectral energy distributions. We also take into account the variable nature of the neutral gas column NH and derive the Seyfert sub-classes of all our objects in a consistent way.

We show in a sample of 25 local, hard-X-ray detected Seyfert galaxies (log LX / (erg/s) ≈ 41.5 - 43.5) that there can actually be a good agreement between optical and X-ray classification. If Seyfert types 1.8 and 1.9 are considered unobscured, the threshold between X-ray unabsorbed and absorbed should be chosen at a column NH = 1022.3 cm-2 to be consistent with the optical classification.

We find that NH is related to AV and that the NH / AV ratio is approximately Galactic or higher in all sources, as indicated previously. But in several objects we also see that deviations from the Galactic ratio are only due to a variable X-ray column, showing that (1) deviations from the Galactic NH / AV can simply be explained by dust-free neutral gas within the broad line region in some sources, that (2) the dust properties in AGNs can be similar to Galactic dust and that (3) the dust color method is a robust way to estimate the optical extinction towards the sublimation radius in all but the most obscured AGNs.

Accepted by A&A

E-mail contact: burtscher@mpe.mpg.de
Preprint available at http://arxiv.org/abs/1511.05566


Deep Chandra observations of Pictor A

M.J. Hardcastle1, E. Lenc2,3, M. Birkinshaw4, J.H. Croston5,6, J.L. Goodger1, H.L. Marshall7, E.S. Perlman8, A. Siemiginowska9, Ł. Stawarz10 and D.M. Worrall4

1. School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
2. Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006, Australia
3. ARC Centre of Excellence for All-Sky Astrophysics (CAASTRO), Redfern, NSW 2016, Australia
4. H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, UK
5. School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, UK
6. Institute of Continuing Education, University of Cambridge, Madingley Hall, Madingley, CB23 8AQ, UK
7. Kavli Inst. for Astrophysics and Space Research, Massachusetts Inst. of Technology, Cambridge, MA 02139, USA
8. Dept. of Physics and Space Sciences, Florida Institute of Technology, 150 W. University Blvd., Melbourne, FL 32901, USA
9. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
10. Astronomical Observatory, Jagiellonian University, ul. Orla 171, 30-244 Kraków, Poland

We report on deep Chandra observations of the nearby broad-line radio galaxy Pictor A, which we combine with new Australia Telescope Compact Array (ATCA) observations. The new X-ray data have a factor 4 more exposure than observations previously presented and span a 15-year time baseline, allowing a detailed study of the spatial, temporal and spectral properties of the AGN, jet, hotspot and lobes. We present evidence for further time variation of the jet, though the flare that we reported in previous work remains the most significantly detected time-varying feature. We also confirm previous tentative evidence for a faint counterjet. Based on the radio through X-ray spectrum of the jet and its detailed spatial structure, and on the properties of the counterjet, we argue that inverse-Compton models can be conclusively rejected, and propose that the X-ray emission from the jet is synchrotron emission from particles accelerated in the boundary layer of a relativistic jet. For the first time, we find evidence that the bright western hotspot is also time-varying in X-rays, and we connect this to the small-scale structure in the hotspot seen in high-resolution radio observations. The new data allow us to confirm that the spectrum of the lobes is in good agreement with the predictions of an inverse-Compton model and we show that the data favour models in which the filaments seen in the radio images are predominantly the result of spatial variation of magnetic fields in the presence of a relatively uniform electron distribution.

Accepted by MNRAS

E-mail contact: m.j.hardcastle@herts.ac.uk
Preprint available at http://arxiv.org/abs/1510.08392


A mid-infrared spectroscopic atlas of local active galactic nuclei on sub-arcsecond resolution using GTC/CanariCam

A. Alonso-Herrero1,2,3, P. Esquej4, P. F. Roche2, C. Ramos Almeida5,6,18, O. González-Martín7, C. Packham3, N. A. Levenson8, R. E. Mason9, A. Hernán-Caballero1, M. Pereira-Santaella10,11, C. Alvarez5,6, I. Aretxaga12, E. López-Rodríguez3, L. Colina10,11, T. Díaz-Santos13, M. Imanishi14,15,16, J. M. Rodríguez Espinosa5,6, E. Perlman17

1. Instituto de Física de Cantabria, CSIC-UC, E-39005 Santander, Spain
2. Department of Physics, University of Oxford, Oxford OX1 3RH, UK
3. Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX 78249, USA
4. Departamento de Astrofísica, Universidad Complutense de Madrid, E-28040 Madrid, Spain
5. Instituto de Astrofísica de Canarias (IAC), E-38205 La Laguna, Tenerife, Spain
6. Departamento de Astrofísica, Universidad de la Laguna (ULL), E-38206 La Laguna, Tenerife, Spain
7. Centro de Radioastronomía y Astrofísica (CRyA-UNAM), 3-72 (Xangari), 8701, Morelia, Mexico
8. Gemini Observatory, Casilla 603, La Serena, Chile
9. Gemini Observatory, Northern Operations Center, Hilo, HI 96720, USA
10. Centro de Astrobiología, CSIC-INTA, E-28850 Torrejón de Ardoz, Madrid, Spain
11. ASTRO-UAM, Universidad Autónoma de Madrid, Unidad Asociada CSIC, Madrid, Spain
12. Instituto Nacional de Astrofísica, Optica y Electrónica (INAOE), 72000 Puebla, Mexico
13. Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago, Chile
14. Subaru Telescope, 650 North A'ohoku Place, Hilo, Hawaii, 96720, USA
15. National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
16. Dept. of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), Mitaka, Tokyo 181-8588, Japan
17. Florida Institute of Technology, Melbourne, FL 32901, USA
18. Marie Curie Fellow

We present an atlas of mid-infrared (mid-IR) ∼ 7.5-13 μm spectra of 45 local active galactic nuclei (AGN) obtained with CanariCam on the 10.4m Gran Telescopio CANARIAS (GTC) as part of an ESO/GTC large program. The sample includes Seyferts and other low luminosity AGN (LLAGN) at a median distance of 35Mpc and luminous AGN, namely PG quasars, (U)LIRGs, and radio galaxies (RG) at a median distance of 254Mpc. To date, this is the largest mid-IR spectroscopic catalog of local AGN at sub-arcsecond resolution (median 0.3arcsec). The goal of this work is to give an overview of the spectroscopic properties of the sample. The nuclear 12 μm luminosities of the AGN span more than four orders of magnitude, ν L12μm ∼ 3×1041 - 1046 erg s-1. In a simple mid-IR spectral index vs. strength of the $9.7\,\mu$m silicate feature diagram most LLAGN, Seyfert nuclei, PG quasars, and RGs lie in the region occupied by clumpy torus model tracks. However, the mid-IR spectra of some might include contributions from other mechanisms. Most (U)LIRG nuclei in our sample have deeper silicate features and flatter spectral indices than predicted by these models suggesting deeply embedded dust heating sources and/or contribution from star formation. The 11.3 μm PAH feature is clearly detected in approximately half of the Seyfert nuclei, LLAGN, and (U)LIRGs. While the RG, PG quasars, and (U)LIRGs in our sample have similar nuclear ν L12μm, we do not detect nuclear PAH emission in the RGs and PG quasars.

Published in MNRAS, 455, 563 (2016) DOI: 10.1093/mnras/stv2342

E-mail contact: aalonso@ifca.unican.es
Preprint available at http://arxiv.org/abs/1510.02631


Polarization microlensing in the quadruply imaged broad absorption line quasar H1413+117

D. Hutsemékers1, D. Sluse1, L. Braibant1, T. Anguita2,3

1. Institut d'Astrophysique et de Géophysique, Université de Liège, Quartier Agora - Allée du six Août, 19c, B-4000 Liège, Belgium
2. Departamento de Ciencias Fisicas, Universidad Andres Bello, Fernandez Concha 700, Las Condes, Santiago, Chile
3. Millennium Institute of Astrophysics, Chile

We have obtained spectropolarimetric observations of the four images of the gravitationally lensed broad absorption line quasar H1413+117. The polarization of the microlensed image D is significantly different, both in the continuum and in the broad lines, from the polarization of image A, which is essentially unaffected by microlensing. The observations suggest that the continuum is scattered off two regions, spatially separated, and producing roughly perpendicular polarizations. These results are compatible with a model in which the microlensed polarized continuum comes from a compact region located in the equatorial plane close to the accretion disk and the non-microlensed continuum from an extended region located along the polar axis.

Published in Astronomy and Astrophysics, 584, A61 (2015) DOI: 10.1051/0004-6361/201527243

E-mail contact: D.Hutsemekers@ulg.ac.be, dsluse@ulg.ac.be
Preprint available at http://arxiv.org/abs/1510.06047


The KMOS AGN Survey at High redshift (KASH$z$): the prevalence and drivers of ionised outflows in the host galaxies of X-ray AGN

C. M. Harrison1,†, D. M. Alexander1, J. R. Mullaney2, J. P. Stott3,1, A. M. Swinbank4,1, V. Arumugam5, F. E. Bauer6,7,8, R. G. Bower4,1, A. J. Bunker3,9, R. M. Sharples10,1

1. Centre for Extragalactic Astronomy, Durham University, South Road, Durham, DH1 3LE, U.K.
2. Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, U.K.
3. Astrophysics, Department of Physics, University of Oxford, Keble Road, Oxford, OX1 3RH, U.K.
4. Institute for Computational Cosmology, Department of Physics, Durham University, South Road, Durham, DH1 3LE, U.K.
5. European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany
6. Instituto de Astrofísica, Facultad de Física, Pontifica Universidad Católica de Chile, 306, Santiago 22, Chile
7. Millennium Institute of Astrophysics, Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile
8. Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
9. Affiliate Member, Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Japan 277-8583
10. Centre for Advanced Instrumentation, Durham University, South Road, Durham, DH1 3LE, U.K.

We present the first results from the KMOS AGN Survey at High redshift (KASHz), a VLT/KMOS integral-field spectroscopic (IFS) survey of z>0.6 AGN. We present galaxy-integrated spectra of 89 X-ray AGN (L2-10keV=1042 - 1045 ergs-1), for which we observed [O III] (z≈1.1-1.7) or Hα emission (z≈0.6-1.1). The targets have X-ray luminosities representative of the parent AGN population and we explore the emission-line luminosities as a function of X-ray luminosity. For the [O III] targets, ≈50percent have ionised gas velocities indicative of gas that is dominated by outflows and/or highly turbulent material (i.e., overall line-widths >600kms-1). The most luminous half (i.e., LX>6×1043ergs-1) have a >2 times higher incidence of such velocities. On the basis of our results, we find no evidence that X-ray obscured AGN are more likely to host extreme kinematics than unobscured AGN. Our KASHz sample has a distribution of gas velocities that is consistent with a luminosity-matched sample of z<0.4 AGN. This implies little evolution in the prevalence of ionised outflows, for a fixed AGN luminosity, despite an order-of-magnitude decrease in average star-formation rates over this redshift range. Furthermore, we compare our Hα targets to a redshift-matched sample of star-forming galaxies and despite a similar distribution of Hα luminosities and likely star-formation rates, we find extreme ionised gas velocities are up to ≈10× more prevalent in the AGN-host galaxies. Our results reveal a high prevalence of extreme ionised gas velocities in high-luminosity X-ray AGN and imply that the most powerful ionised outflows in high-redshift galaxies are driven by AGN activity.

Accepted by MNRAS

E-mail contact: c.m.harrison@mail.com
Preprint available at http://arxiv.org/abs/1511.00008


Interferometric Monitoring of Gamma-Ray Bright Active Galactic Nuclei II: Frequency Phase Transfer

Juan-Carlos Algaba1, Guang-Yao Zhao1, Sang-Sung Lee1,2, Do-Young Byun1, Sin-Cheol Kang1,2, Dae-Won Kim3, Jae-Young Kim3, Jeon-Sook Kim4, Soon-Wook Kim1,2, Motoki Kino1, Atsushi Miyazaki1,5, Jong-Ho Park3, Sascha Trippe3 and Kiyoaki Wajima1

1. Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Korea
2. Korea University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Korea
3. Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Korea
4. National Astronomical Observatory of Japan, 2211 Osawa, Mitaka, Tokyo 1818588, Japan
5. Faculty of Science and Engineering, Hosei University, 372 Kajino-cho, Koganei, Tokyo 1848584, Japan

The Interferometric Monitoring of Gamma-ray Bright Active galactic nuclei (iMOGABA) program provides not only simultaneous multifrequency observations of bright gamma-ray detected active galactic nuclei (AGN), but also covers the highest Very Large Baseline Interferometry (VLBI) frequencies ever being systematically monitored, up to 129 GHz. However, observation and imaging of weak sources at the highest observed frequencies is very challenging. In the second paper in this series, we evaluate the viability of the frequency phase transfer technique to iMOGABA in order to obtain larger coherence time at the higher frequencies of this program (86 and 129 GHz) and image additional sources that were not detected using standard techniques. We find that this method is applicable to the iMOGABA program even under non-optimal weather conditions.

Accepted by Journal of the Korean Astronomical Society, 48, 237 (2015)

E-mail contact: algaba@kasi.re.kr
Preprint available at http://arxiv.org/abs/1510.05817 and http://jkas.kas.org/journals/2015v48n5/v48n5p237_algaba.pdf


Mid-infrared luminous quasars in the GOODS-Herschel fields: a large population of heavily-obscured, Compton-thick quasars at z≈2

A. Del Moro1,2, D. M. Alexander1, F. E. Bauer3,4,5,6, E. Daddi7, D. D. Kocevski8, D. H. McIntosh9, F. Stanley1, W. N. Brandt10,11,12, D. Elbaz7, C. M. Harrison1, B. Luo13, J. R. Mullaney14 and Y. Q. Xue15

1. Centre for Extragalactic Astronomy, Department of Physics, Durham University, South Road, Durham, DH1 3LE, UK
2. Max-Planck-Institut für Extraterrestrische Physik (MPE), Postfach 1312, D85741, Garching, Germany
3. Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, 306, Santiago 22, Chile
4. Millenium Institute of Astrophysics, Santiago, Chile
5. EMBIGGEN Anillo, Concepción, Chile
6. Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, Colorado 80301
7. CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France
8. Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506-0055, USA
9. Department of Physics & Astronomy, University of Missouri-Kansas City, 5110 Rockhill Rd., Kansas City, MO 64110, USA
10. Dept. of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802, USA
11. Institute for Gravitation and the Cosmos, Pennsylvania State University, University Park, PA 16802, USA
12. Department of Physics, Pennsylvania State University, University Park, PA 16802, USA
13. School of Astronomy and Space Science, Nanjing University, Nanjing 210093, China
14. Department of Physics and Astronomy, University of Sheffield, Hounsfield Road, Sheffield S3 7RH, UK
15. Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Chinese Academy of Sciences, Hefei, Anhui 230026, China

We present the infrared (IR) and X-ray properties of a sample of 33 mid-IR luminous quasars (νL6 μm ≥ 6×1044 erg s-1) at redshift z≈ 1-3, identified through detailed spectral energy distribution analyses of distant star-forming galaxies, using the deepest IR data from Spitzer and Herschel in the GOODS-Herschel fields. The aim is to constrain the fraction of obscured, and Compton-thick (CT, NH > 1.5×1024 cm-2) quasars at the peak era of nuclear and star-formation activities. Despite being very bright in the mid-IR band, ≈30% of these quasars are not detected in the extremely deep 2 Ms and 4 Ms Chandra X-ray data available in these fields. X-ray spectral analysis of the detected sources reveals that the majority (≈67%) are obscured by column densities NH > 1022 cm-2; this fraction reaches ≈80% when including the X-ray undetected sources (9 out of 33), which are likely to be the most heavily-obscured, CT quasars. We constrain the fraction of CT quasars in our sample to be ≈24-48%, and their space density to be Φ = (6.7±2.2)×10-6 Mpc-3. From the investigation of the quasar host galaxies in terms of star-formation rates (SFRs) and morphological distortions, as a sign of galaxy mergers/interactions, we do not find any direct relation between SFRs and quasar luminosity or X-ray obscuration. On the other hand, there is tentative evidence that the most heavily-obscured quasars have, on average, more disturbed morphologies than the unobscured/moderately-obscured quasar hosts, which preferentially live in undisturbed systems. However, the fraction of quasars with disturbed morphology amongst the whole sample is ≈40%, suggesting that galaxy mergers are not the main fuelling mechanism of quasars at z≈2.

Accepted by MNRAS

E-mail contact: adelmoro@mpe.mpg.de
Preprint available at http://arxiv.org/abs/1504.03329


A Spectroscopic Survey of X-ray Selected AGN in the Northern XMM-XXL Field

M.-L. Menzel1, A. Merloni1, A. Georgakakis1, M. Salvato1, E. Aubourg2, W.N. Brandt3,4,5, M. Brusa6,7, J. Buchner1, T. Dwelly1, K. Nandra1, I. Pâris8, P. Petitjean9, A. Schwope10

1. Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, D-85741 Garching, Germany
2. Laboratoire AstroParticule et Cosmologie, 12, rue Alice Domon et Léonie Duquet, F-75205 Paris Cedex 13, France
3. Dept. of Astronomy & Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802, USA
4. Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802, USA
5. Department of Physics, 104 Davey Lab, The Pennsylvania State University, University Park, PA 16802, USA
6. Dipartimento di Fisica e Astronomia, Università di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy
7. INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
8. Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, I-34143 Trieste, Italy
9. Institut d'Astrophysique de Paris, 98 bis boulevard Arago, F-75014 Paris, France
10. Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam, Germany

This paper presents a survey of X-ray selected active galactic nuclei (AGN) with optical spectroscopic follow-up in a ∼ 18 deg2 area of the equatorial XMM-XXL north field. A sample of 8445 point-like X-ray sources detected by XMM-Newton above a limiting flux of F0.5-10 keV > 10-15 erg cm-2 s-1 was matched to optical (SDSS) and infrared (WISE) counterparts. We followed up 3042 sources brighter than r=22.5 mag with the SDSS BOSS spectrograph. The spectra yielded a reliable redshift measurement for 2578 AGN in the redshift range z=0.02-5.0, with 0.5-2 keV luminosities ranging from 1039-1046 erg s-1. This is currently the largest published spectroscopic sample of X-ray selected AGN in a contiguous area. The BOSS spectra of AGN candidates show a distribution of optical line widths which is clearly bimodal, allowing an efficient separation between broad- and narrow-emission line AGN. The former dominate our sample (70 per cent) due to the relatively bright X-ray flux limit and the optical BOSS magnitude limit. We classify the narrow emission line objects (22 per cent of the full sample) using standard BPT diagnostics: the majority have line ratios indicating the dominant source of ionization is the AGN. A small number (8 per cent of the full sample) exhibit the typical narrow line ratios of star-forming galaxies, or only have absorption lines in their spectra. We term the latter two classes "elusive" AGN, which would not be easy to identify correctly without their X-ray emission. We also compare X-ray (XMM-Newton), optical colour (SDSS), and IR (WISE) AGN selections in this field. X-ray observations reveal, by far, the largest number of AGN. The overlap between the selections, which is a strong function of the imaging depth in a given band, is also remarkably small. We show using spectral stacking that a large fraction of the X-ray AGN would not be selectable via optical or IR colours due to host galaxy contamination. A substantial fraction of AGN may therefore be missed by these longer-wavelength selection methods.

Accepted by MNRAS

E-mail contact: mlmenzel@mpe.mpg.de
Preprint available at http://arxiv.org/abs/1511.07870
We publicly release the catalogue of X-ray selected AGN on the following webpage:
http://www.mpe.mpg.de/XraySurveys/XMM-XXL/




Meetings


Active Galactic Nuclei: What's in a name?
ESO, Garching bei München, Germany
June 27 - July 1, 2016

Webpage: http://www.eso.org/sci/meetings/2016/AGN2016
Email: agn2016@eso.org


Active Galactic Nuclei (AGN) are being discovered in ever-larger numbers over the whole electromagnetic spectrum. Different bands employ different methods to identify these sources but, most importantly, provide different windows on AGN physics. The infrared band is mostly sensitive to obscuring material and dust, the optical/UV band is related to emission from the accretion disk, while the X-ray band traces the emission of a (putative) corona. γ-ray and (high flux density) radio samples, on the other hand, preferentially select AGN emitting strong non-thermal radiation. This has led to a proliferation of classes, which outsiders (but insiders as well!) find mesmerizing. The main goal of the Workshop is to paint the AGN "big picture", which comes out of these multi-wavelength surveys, and understand the truly intrinsic and fundamental properties of AGN and the physics behind them. This will be done by discussing primarily these topics:

All of the above will be achieved by having a truly multi-wavelength Workshop consisting of review and contributed talks distributed over six sessions: radio, infrared, optical, X-ray, γ-ray, and variability.

Review speakers: Vernesa Smolcic, Roberto Assef, Gordon Richards, Dave Alexander, Paolo Giommi, Barbara De Marco, and Phil Hopkins.

SOC: Paolo Padovani (chair), Evanthia Hatziminaoglou, Ryan Hickox, Lisa Kewley, Vincenzo Mainieri, Mara Salvato, John Silverman, Sylvain Veilleux