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Active Galaxies Newsletter

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.

Issue 220, February 2016, is also available in LaTeX , postscript (gzipped), pdf, html

Previous issues of the AGN Newsletter can be found in the Back Issues link on the left side bar.

Latest Issue:

Welcome to all the new subscribers, and thanks to everyone who contributed to this issue of the Active Galaxies Newsletter. 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.

Broad-band spectral energy distribution of 3000 Å break quasars from the Sloan Digital Sky Survey

H. Meusinger^1,2, P. Schalldach¹, A. Mirhosseini¹, and F. Pertermann¹

1. Thüringer Landessternwarte Tautenburg, Sternwarte 5, D-07778 Tautenburg, Germany
2. University Leipzig, Faculty of Physics and Earth Sciences, Linnèstr. 5, 04103 Leipzig, Germany

The Sloan Digital Sky Survey (SDSS) discovered a few unusual quasars with a characteristic break in the continuum around 3000 Å that neither shows the typical structure of broad absorption line (BAL) troughs nor is explained by typical intrinsic dust reddening. We used the method of Kohonen self-organising maps for a systematic search for objects with such properties in the SDSS spectra archive. We constructed a sample of 23 quasars classified as 3000 Å break quasars and two comparison samples of quasars with similar properties, to some extent, but also showing typical BAL features. We computed ensemble-averaged broad-band SEDs based on archival data from SDSS, GALEX, 2MASS, UKIDSS, and WISE. The SEDs were corrected for intrinsic dust absorption by the comparison with the average SED of normal quasars. The de-reddened arithmetic median composite SED of the 3000 Å break quasars is found to be indistinguishable from that of the unusual BAL quasars. We conclude that 3000 Å break quasars are most likely extreme versions of BAL quasars. Assuming that the intrinsic SED of the continuum source is represented by the quasar composite SED, the 3000 Å break quasars tend to be intrinsically more luminous than ordinary quasars.

Accepted by A&A

E-mail contact: meus@tls-tautenburg.de
Preprint available at http://arxiv.org/abs/1601.00544

The gamma-ray emitting radio-loud narrow-line Seyfert 1 galaxy PKS2004-447 - I. The X-ray View

A. Kreikenbohm^1,2, R. Schulz^1,2, M. Kadler¹, J. Wilms², A. Markowitz^2,3,4, C.S. Chang⁵, B. Carpenter^6,7, D. Elsässer¹, N. Gehrels⁶, K. Mannheim¹, C. Müller^7,1, R. Ojha^6,8,9, E. Ros^10,11,12, J. Trüstedt¹

1. Lehrstuhl für Astronomie, Universität Würzburg,Würzburg, Germany
2. Dr Karl Remeis-Observatory and Erlangen Centre for Astroparticle Physics,Bamberg, Germany
3. University of California, San Diego, CASS, USA
4. Alexander von Humboldt Fellow
5. Joint ALMA Observatory, ESO, Santiago, Chile
6. Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, USA
7. Department of Astrophysics/IMAPP, Radboud University Nijmegen, The Netherlands
8. Catholic University of America, Washington, USA
9. University of Maryland Baltimore County/CRESST, Baltimore, USA
10. Max-Planck-Institut f??r Radioastronomie, Bonn, Germany
11. Observatori Astronòmic, Univ. València, 46980 Paterna València Spain
12. Dept. d'Astronomia i Astrofísica, Univ. València, València, Spain

As part of the TANAMI multiwavelength progam, we discuss new X-ray observations of the γ-ray and radio-loud narrow line Seyfert 1 galaxy (γ-NLS1). The active galaxy is a member of a small sample of radio-loud NLS1s detected in γ-rays by the Fermi Large Area Telescope. It stands out for being the radio-loudest and the only southern-hemisphere source in this sample. We present results from our X-ray monitoring program comprised of Swift snapshot observations from 2012 through 2014 and two new X-ray observations with XMM-Newton in 2012. Supplemented by archival data from 2004 and 2011, our data set allows for a careful analysis of the X-ray spectrum and variability of this peculiar source. The (0.5-10)keV spectrum is described well by a power law (Γ∼1.6), which can be interpreted as non-thermal emission from a relativistic jet. The source exhibits moderate flux variability on timescales of both months and years. Correlated brightness variations in the (0.5-2)keV and (2-10)keV bands are explained by a single variable spectral component, such as the one from the jet. A possible soft excess seen in the data from 2004 cannot be confirmed by the new XMM-Newton observations taken during low-flux states. Any contribution to the total flux in 2004 is less than 20% of the power-law component. The (0.5-10)keV luminosities of are in the range of (0.5-2.7)×10⁴⁴ erg s^-1. A comparison of the X-ray properties among the known γ-NLS1 galaxies shows that in four out of five cases the X-ray spectrum is dominated by a flat power law without intrinsic absorption. These objects are moderately variable in their brightness, while spectral variability is observed in at least two sources. The major difference across the X-ray spectra of γ-NLS1s is the luminosity, which spans a range of almost two orders of magnitude from 10⁴⁴ erg s^-1 to 10⁴⁶ erg s^-1 in the (0.5-10)keV band.

Accepted by Astronomy & Astrophysics (A&A 2016, Volume 585, A91 DOI: 10.1051/0004-6361/201424818)

E-mail contact: akreikenbohm@astro.uni-wuerzburg.de
Preprint available at: http://arxiv.org/abs/1509.03735

The nuclear dust lane of Circinus: collimation without a torus

M. Mezcua^1,2,3, M. A. Prieto^3,4, J.A. Fernández-Ontiveros⁵ and K. R. W. Tristram⁶

1. Département de Physique, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montreal, Quebec H3C 3J7, Canada
2. Harvard-Smithsonian Center for Astrophysics (CfA), 60 Garden Street, Cambridge, Massachusetts 02138, USA
3. Instituto de Astrofísica de Canarias (IAC), E-38200 La Laguna, Tenerife, Spain
4. Universidad de La Laguna, Dept. Astrofísica, E-38206 La Laguna, Tenerife, Spain
5. Istituto di Astrofisica e Planetologia Spaziali (INAF-IAPS), Via Fosso del Cavaliere 100, 00133 Roma, Italy
6. European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago de Chile, Chile

In some AGN, nuclear dust lanes connected to kpc-scale dust structures provide all the extinction required to obscure the nucleus, challenging the role of the dusty torus proposed by the Unified Model. In this letter we show the pc-scale dust and ionized gas maps of Circinus constructed using sub-arcsec-accuracy registration of infrared VLT AO images with optical Hubble Space Telescope images. We find that the collimation of the ionized gas does not require a torus but is caused by the distribution of dust lanes of the host galaxy on ∼10 pc scales. This finding questions the presumed torus morphology and its role at parsec scales, as one of its main attributes is to collimate the nuclear radiation, and is in line with interferometric observations which show that most of the pc-scale dust is in the polar direction. We estimate that the nuclear dust lane in Circinus provides 1/3 of the extinction required to obscure the nucleus. This constitutes a conservative lower limit to the obscuration at the central parsecs, where the dust filaments might get optically thicker if they are the channels that transport material from ∼100 pc scales to the centre.

Accepted by MNRAS Letters (DOI: 10.1093/mnrasl/slv209)

E-mail contact: marmezcua.astro@gmail.com
Preprint available at http://arxiv.org/abs/1601.02653

Unravelling the complex structure of AGN-driven outflows: I. Kinematics and sizes

Marios Karouzos¹, Jong-Hak Woo¹, and Hyun-Jin Bae²

1. Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul 151-742, Republic of Korea
2. Department of Astronomy and Center for Galaxy EVolution Research, Yonsei University, Seoul 120-749, Republic of Korea

Outflows driven by active galactic nuclei (AGNs) are often invoked as agents of the long-sought AGN feedback. Yet, characterizing and quantifying the impact on their host galaxies has been challenging. We present Gemini Multi-Object Spectrograph integral field unit data of 6 local (z<0.1) and luminous (L_[OIII]>10⁴² erg s^-1) Type 2 AGNs. In the first of a series of papers, we investigate the kinematics and constrain the size of the outflows. The ionized gas kinematics can be described as a superposition of a gravitational component that follows the stellar motion and an outflow-driven component that shows large velocity (up to 600 km s^-1) and large velocity dispersion (up to 800 km s^-1). Using the spatially resolved measurements of the gas, we kinematically measure the size of the outflow, which is found to be between 1.3 and 2.1 kpc. Due to the lack of a detailed kinematic analysis, previous outflow studies likely overestimate their size by up to more than a factor of 2, depending on how the size is estimated and whether the [OIII] or Hα emission line is used. The relatively small size of the outflows for all 6 of our objects casts doubts on their potency as a mechanism for negative AGN feedback.

Accepted by Astrophysical Journal

E-mail contact: mkarouzos@gmail.com
Preprint available at http://arxiv.org/abs/1601.02621

ZFOURGE catalogue of AGN candidates: an enhancement of 160μm-derived star-formation rates in active galaxies to z=3.2

Michael J. Cowley¹, Lee R. Spitler², Kim-Vy H. Tran³, Glen A. Rees^1,4, Ivo Labbé⁵, Rebecca J. Allen^2,6, Gabriel B. Brammer⁷, Karl Glazebrook⁶, Andrew M. Hopkins², Stéphanie Juneau⁸, Glenn G. Kacprzak⁶, James R. Mullaney⁹, Themiya Nanayakkara⁶, Casey Papovich⁶, Ryan F. Quadri⁵, Caroline M. S. Straatman⁵, Adam R. Tomczak^3,10, and Pieter G. van Dokkum¹¹

1. Department of Physics and Astronomy, Macquarie University, NSW 2109, Australia
2. Australian Astronomical Observatory, PO Box 915, North Ryde, NSW 1670, Australia
3. George P. and Cynthia W. Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A&M University, College Station, TX 77843, USA
4. CSIRO Australia Telescope National Facility, PO Box 76, Epping, NSW 1710, Australia
5. Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
6. Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122, Australia
7. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
8. CEA-Saclay, DSM/IRFU/SAp, F-91191 Gif-sur-Yvette, France
9. Department of Physics and Astronomy, The University of Sheffield, Hounsfield Road, Sheffield, S3 7RH, UK
10. Department of Physics, University of California Davis, One Shields Avenue, Davis, CA 95616, USA
11. Department of Astronomy, Yale University, New Haven, CT 06520, USA

We investigate active galactic nuclei (AGN) candidates within the FourStar Galaxy Evolution Survey (ZFOURGE) to determine the impact they have on star-formation in their host galaxies. We first identify a population of radio, X-ray, and infrared-selected AGN by cross-matching the deep K_s-band imaging of ZFOURGE with overlapping multi-wavelength data. From this, we construct a mass-complete (log(M_*/M_⊙) ≥ 9.75), AGN luminosity limited sample of 235 AGN hosts over z = 0.2-3.2. We compare the rest-frame U-V versus V-J (UVJ) colours and specific star-formation rates (sSFRs) of the AGN hosts to a mass-matched control sample of inactive (non-AGN) galaxies. UVJ diagnostics reveal AGN tend to be hosted in a lower fraction of quiescent galaxies and a higher fraction of dusty galaxies than the control sample. Using 160μm Herschel PACS data, we find the mean specific star-formation rate of AGN hosts to be elevated by 0.34±0.07 dex with respect to the control sample across all redshifts. This offset is primarily driven by infrared-selected AGN, where the mean sSFR is found to be elevated by as much as a factor of ∼5. The remaining population, comprised predominantly of X-ray AGN hosts, is found mostly consistent with inactive galaxies, exhibiting only a marginal elevation. We discuss scenarios that may explain these findings and postulate that AGN are less likely to be a dominant mechanism for moderating galaxy growth via quenching than has previously been suggested.

Accepted by MNRAS (DOI: 10.1093/mnras/stv2992)

E-mail contact: michael.cowley@mq.edu.au
Preprint available at http://arxiv.org/abs/1601.02016

Multi-Epoch Observations of Extremely High-Velocity Emergent Broad Absorption

Jesse A. Rogerson¹, Patrick B. Hall¹, Paola Rodríguez Hidalgo^1,2, Patrik Pirkola¹,William N. Brandt^3,4,5, Nur Filiz Ak⁶

1. Department of Physics and Astronomy, York University, Toronto, ON M3J 1P3, Canada
2. Department of Physics and Astronomy, Humbolt State University, Arcata, CA 95521, USA
3. Department 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. Department of Astronomy and Space Sciences, Faculty of Sciences, Erciyes University, 38039 Kayseri, Turkey

We present the discovery of the highest velocity CIV broad absorption line to date in the z=2.47 quasar SDSS J023011.28+005913.6, hereafter J0230. In comparing the public DR7 and DR9 spectra of J0230, we discovered an emerging broad absorption trough outflowing at ∼60,000 km s^-1, which we refer to as trough A. In pursuing follow up observations of trough A, we discovered a second emergent CIV broad absorption trough outflowing at ∼40,000 km s^-1, namely trough B. In total, we collected seven spectral epochs of J0230 that demonstrate emergent and rapidly (∼10 days in the rest-frame) varying broad absorption. We investigate two possible scenarios that could cause these rapid changes: bulk motion and ionization variability. Given our multi-epoch data, we were able to rule out some simple models of bulk motion, but have proposed two more realistic models to explain the variability of both troughs. Trough A is likely an augmented 'crossing disk' scenario with the absorber moving at 10,000 < v (km s^-1) < 18,000. Trough B can be explained by a flow-tube feature travelling across the emitting region at 8,000 < v (km s^-1) < 56,000. If ionization variability is the cause for the changes observed, trough A's absorber has n_e ≥ 724 cm^-3 and is at r_equal ≥ 2.00 kpc, or is at r < 2.00 kpc with no constraint on the density; trough B's absorber either has n_e ≥1540 cm^-3 and is at r_equal ≥ 1.37 kpc, or is at r < 1.37 kpc with no constraint on the density.

Accepted by MNRAS, DOI: 10.1093/mnras/stv3010

E-mail contact: rogerson@yorku.ca
Preprint available at http://arxiv.org/abs/1509.02842

NuSTAR unveils a low-luminosity heavily obscured AGN in the LIRG NGC 6286

C. Ricci^1,2, F. E. Bauer^1,2,3,4, E. Treister^5,2, C. Romero-Canizales^1,3, P. Arevalo⁶, K. Iwasawa⁷, G. C. Privon⁵, D. B. Sanders⁸, K. Schawinski⁹, D. Stern¹⁰, M. Imanishi^11,12,13

1. Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile
2. EMBIGGEN Anillo
3. Millennium Institute of Astrophysics, Chile
4. Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, Colorado 80301, USA
5. Universidad de Concepción, Departamento de Astronomía, Casilla 160-C, Concepción, Chile
6. Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Gran Bretana N?? 1111, Playa Ancha, Valparaíso, Chile
7. ICREA and Institut de Ciències del Cosmos, Universitat de Barcelona, IEEC-UB, Martí i Franquès, 1, 08028 Barcelona, Spain
8. Institute for Astronomy, 2680 Woodlawn Drive, University of Hawaii, Honolulu, HI 96822
9. Institute for Astronomy, Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich, Switzerland
10. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
11. Subaru Telescope, 650 North A'ohoku Place, Hilo, Hawaii, 96720, U.S.A.
12. National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
13. Department of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), Mitaka, Tokyo 181-8588, Japan

We report the detection of a heavily obscured Active Galactic Nucleus (AGN) in the luminous infrared galaxy (LIRG) NGC 6286, identified in a 17.5ks NuSTAR observation. The source is in an early merging stage, and was targeted as part of our ongoing NuSTAR campaign observing local luminous and ultra-luminous infrared galaxies in different merger stages. NGC6286 is clearly detected above 10keV and, by including the quasi-simultaneous Swift/XRT and archival XMM-Newton and Chandra data, we find that the source is heavily obscured [N_H ≃ (0.95-1.32)×10²⁴ cm^-2], with a column density consistent with being Compton-thick [CT, log (N_H/cm^-2) ≥ 24]. The AGN in NGC 6286 has a low absorption-corrected luminosity (L_2-10keV ∼ 3-20×10⁴¹ erg s^-1) and contributes ≲1% to the energetics of the system. Because of its low-luminosity, previous observations carried out in the soft X-ray band (<10 keV) and in the infrared did not notice the presence of a buried AGN. NGC6286 has multi-wavelength characteristics typical of objects with the same infrared luminosity and in the same merger stage, which might imply that there is a significant population of obscured low-luminosity AGN in LIRGs that can only be detected by sensitive hard X-ray observations.

Accepted by ApJ

E-mail contact: cricci@astro.puc.cl
Preprint available at http://arxiv.org/abs/1601.05800

RoboPol: Optical polarization-plane rotations and flaring activity in blazars

D. Blinov^1,2,7, V. Pavlidou^1,2, I. E. Papadakis^1,2, T. Hovatta⁸, T.J. Pearson⁴, I. Liodakis^1,2, G. V. Panopoulou¹, E. Angelakis³, M. Balokovic⁴, H. Das⁶, P. Khodade⁶, S. Kiehlmann⁸, O.G. King⁴, A. Kus⁵, N. Kylafis^2,1, A. Mahabal⁴, A. Marecki⁵, D. Modi⁶, I. Myserlis³, E. Paleologou¹, I. Papamastorakis^{1,2/sup>, B. Pazderska5, E. Pazderski5, C. Rajarshi6, A. Ramaprakash6, A.C.S. Readhead4, P. Reig2,1, K. Tassis1,2, J.A. Zensus3}

1. Department of Physics and Institute for Plasma Physics, University of Crete, 71003, Heraklion, Greece
2. Foundation for Research and Technology - Hellas, IESL, Voutes, 71110 Heraklion, Greece
3. Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
4. Cahill Center for Astronomy and Astrophysics, California Institute of Technology, 1200 E California Blvd, MC 249-17, Pasadena CA, 91125, USA
5. Torun Centre for Astronomy, Nicolaus Copernicus University, Faculty of Physics, Astronomy and Informatics, Grudziadzka 5, 87-100 Torun, Poland
6. Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune - 411 007, India
7. Astronomical Institute, St. Petersburg State University,Universitetsky pr. 28, Petrodvoretz, 198504 St. Petersburg, Russia
8. Aalto University Metsähovi Radio Observatory, Metsähovintie 114, 02540 Kylmälä, Finland

We present measurements of rotations of the optical polarization of blazars during the second year of operation of RoboPol, a monitoring programme of an unbiased sample of gamma-ray bright blazars specially designed for effective detection of such events, and we analyse the large set of rotation events discovered in two years of observation. We investigate patterns of variability in the polarization parameters and total flux density during the rotation events and compare them to the behaviour in a non-rotating state. We have searched for possible correlations between average parameters of the polarization-plane rotations and average parameters of polarization, with the following results: (1) there is no statistical association of the rotations with contemporaneous optical flares; (2) the average fractional polarization during the rotations tends to be lower than that in a non-rotating state; (3) the average fractional polarization during rotations is correlated with the rotation rate of the polarization plane in the jet rest frame; (4) it is likely that distributions of amplitudes and durations of the rotations have physical upper bounds, so arbitrarily long rotations are not realised in nature.

Accepted by Monthly Notices of the Royal Astronomical Society

E-mail contact: blinov@physics.uoc.gr
Preprint available at http://arxiv.org/abs/1601.03392

Local SDSS galaxies in the Herschel Stripe82 survey: A critical assessment of optically-derived star-formation rates

D. J. Rosario^1,2, J. T. Mendel¹, S. L. Ellison ³, D. Lutz¹ and J. R. Trump^4,5

1. Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
2. Centre for Extragalactic Astronomy, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
3. Department of Physics and Astronomy, University of Victoria, BC V8P 5C2, Canada
4. Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802, USA
5. Hubble Fellow

We study a set of 3319 galaxies in the redshift interval 0.04 < z < 0.15 with far-infrared (FIR) coverage from the Herschel Stripe 82 survey (HerS), and emission-line measurements, redshifts, stellar masses and star-formation rates (SFRs) from the SDSS (DR7) MPA/JHU database. About 40% of the sample are detected in the Herschel/SPIRE 250 μm band. Total infrared (TIR) luminosities derived from HerS and ALLWISE photometry allow us to compare infrared and optical estimates of SFR with unprecedented statistics for diverse classes of galaxies. We find excellent agreement between TIR-derived and emission line-based SFRs for H II galaxies. Other classes, such as active galaxies and evolved galaxies, exhibit systematic discrepancies between optical and TIR SFRs. We demonstrate that these offsets are attributable primarily to survey biases and the large intrinsic uncertainties of the D_n4000 and colour-based optical calibrations used to estimate the SDSS SFRs of these galaxies. Using a classification scheme which expands upon popular emission-line methods, we demonstrate that emission-line galaxies with uncertain classifications include a population of massive, dusty, metal-rich star-forming systems that are frequently neglected in existing studies. We also study the capabilities of infrared selection of star-forming galaxies. FIR selection reveals a substantial population of galaxies dominated by cold dust which are missed by the long-wavelength WISE bands. Our results demonstrate that Herschel large-area surveys offer the means to construct large, relatively complete samples of local star-forming galaxies with accurate estimates of SFR that can be used to study the interplay between nuclear activity and star-formation.

Accepted by MNRAS

E-mail contact: david.rosario@durham.ac.uk
Preprint available at http://arxiv.org/abs/1601.03039v1

ALMA resolves extended star formation in high-z AGN host galaxies

C. M. Harrison¹, J. M. Simpson¹, F. Stanley¹, D. M. Alexander¹, E. Daddi², J. R. Mullaney³, M. Pannella⁴, D. J. Rosario¹, I. Smail^1,5

1. Centre for Extragalactic Astronomy, Department of Physics, Durham University, South Road, Durham, DH1 3LE
2. CEA Saclay, Laboratoire AIM-CNRS-Université Paris Diderot, Irfu/SAp, Orme des Merisiers, 91191 Gif-sur-Yvette, France
3. Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, U.K.
4. Universitäts-Sternwarte München, Scheinerstr. 1, D-81679 München, Germany
5. Institute for Computational Cosmology, Department of Physics, Durham University, South Road, Durham, DH1 3LE, U.K.

We present high resolution (0.3") Atacama Large Millimeter Array (ALMA) 870μm imaging of five z ≈ 1.5-4.5 X-ray detected AGN (with luminosities of L_2-8keV > 10⁴² erg s^-1). These data provide a ≳20× improvement in spatial resolution over single-dish rest-frame FIR measurements. The sub-millimetre emission is extended on scales of FWHM≈0.2"-0.5", corresponding to physical sizes of 1-3kpc (median value of 1.8kpc). These sizes are comparable to the majority of z=1-5 sub-millimetre galaxies (SMGs) with equivalent ALMA measurements. In combination with spectral energy distribution analyses, we attribute this rest-frame far-infrared (FIR) emission to dust heated by star formation. The implied star-formation rate surface densities are ≈20-200 M_⊙ yr^-1kpc^-2, which are consistent with SMGs of comparable FIR luminosities (i.e., L_IR ≈ [1-5]×10¹² L_⊙). Although limited by a small sample of AGN, which all have high FIR luminosities, our study suggests that the kpc-scale spatial distribution and surface density of star formation in high-redshift star-forming galaxies is the same irrespective of the presence of X-ray detected AGN.

Accepted by MNRAS

E-mail contact: c.m.harrison@mail.com
Preprint available at http://arxiv.org/abs/1510.06740

Radio Galaxies: Resolving the AGN Phenomenon

3 half day session (Event 1.7) at the 41st COSPAR Scientific Assembly 2016

Radio galaxies are providing us with excellent laboratories, where we can probe physical aspects, unification, and cosmic evolution of AGN. Thanks to recent space-based observations, we are now able to resolve the different components of radio galaxies, both in imaging and in spectroscopy. Observations from the radio to the X-ray range can probe the ejection of matter into the jet and monitor their evolution over decades. Gamma-ray observations have shown that radio galaxies are detectable up to the VHE range, although their jets are not pointing at us. At the same time, we observe them out to the early Universe up to redshifts larger than z=5. Planck maps will provide us with new insights into the population of radio galaxies and their distribution in space in the 30-900 GHz range.

It is time to take a closer look again at these sources, to revise the physical picture of radio galaxies, and to answer questions like:

• What triggers highly relativistic jets - and how are they launched?
• How are the jets so well collimated very close to the central engine and how is it confined over a distance of, in some cases, several 100 kpc?
• How do radio galaxies emit VHE photons into the line of sight?
• Why is there no hot spot seen in some radio lobes?
• Are all radio galaxies obscured?
• Why are some AGN in the radiative mode while others are in the jet mode?
• What are the intrinsic differences between low-excitation and high-excitation radio galaxies and how do these relate to the FR-I/II classification?
• What is the high-redshift luminosity function of radio galaxies and how does it evolve to the present day Universe?
• How do radio galaxies interact with their environment?