X-ray properties of a sample of NLS1 selected from the SDSS

Galaxy surveys have revealed the existence of Narrow Emission Line Galaxies (NELG) which are spectroscopically classified as starforming (SF), but whose X-ray luminosity exceeds 1042 erg s?1 which unambiguously signals the presence of an AGN. The origin for such a discrepancy is not understood. In order to addres this issue, we present a study using a large sample of 239 NELG (FWHM(H? ) < 1200 km/s) from the SDSS, for which we can construct the BPT diagram and that are detected in the hard (2?10 keV) X-ray band within the 2XMM X-ray source catalogue. We find that 33 of these objects are diagnosed as starforming galaxies but their X-ray luminosity exceeds 1042 erg s?1 . We conducted a detailed analysis of this population, using other optical spectral features,like the FWHM of the H? emission line and the X-ray spectral properties. We find that the bulk of this misclassified population, which represents over 10% of our full sample of hard X-ray detected NELGs, is constituted by NLS1 galaxies.Partial financial support for this work was provided by the spanish Ministry of Science and Innovation, through grant AYA2009-08059

A revision of the X-ray absorption nature of BALQSOs

Aims. Broad absorption-line quasars (BALQSOs) are key objects for studying the structure and emission/absorption properties of AGN. However, despite their fundamental importance, the properties of BALQSOs remain poorly understood. To investigate the X-ray nature of these sources, as well as the correlations between X-ray and rest-frame UV properties, we compile a large sample of BALQSOs observed by XMM-Newton. Methods. We collect information for 88 sources from the literature and existing catalogues, creating the largest BALQSO sample analysed optically and in X-ray to date. We performed a full X-ray spectral analysis (using unabsorbed and both neutral and ionized absorption models) on a sample of 39 sources with higher X-ray spectral quality, and an approximate hardness-ratio analysis on the remaining sources. Using available optical spectra, we calculate the BALnicity index and investigate the dependence of this optical parameter on different X-ray properties. Results. Using the neutral absorption model, we find that 36% of our BALQSOs have NnH < 5 × 1021 cm−2, lower than the expected X-ray absorption for these objects. However, when we used a physically-motivated model for the X-ray absorption in BALQSOs, i.e., ionized absorption, ∼90% of the objects are absorbed. The observed difference in ionized properties of sources with the BALnicity index (BI) =0 and BI > 0 might be explained by different physical conditions of the outflow and/or inclination effects. The absorption properties also suggest that LoBALs may be physically different objects from HiBALs. In addition, we report on a correlation between the ionized absorption column density and BAL parameters. There is evidence (at the 98% level) that the amount of X-ray absorption is correlated with the strength of high-ionization UV absorption. Not previously reported, this correlation can be naturally understood in virtually all BALQSO models, as being driven by the total amount of gas mass flowing towards the observer. We also find a hint of a correlation between the BI and the ionization level detected in X-rays.We thank the anonymous referee for helpful comments. The first author would like to thank the Spanish Ministerio de Ciencia e Innovación for a Juan de la Cierva contract. XB, FJC and RGM acknowledge financial support by the Spanish MICINN under project ESP2006-13608-C02-01.We also acknowledge the Sloan Digital Sky Survey (http://www.sdss.org/). Funding for the SDSS has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England

On the origin of the X-ray emission from a narrow-line radio quasar at z ; 1

We present new XMM?Newton X-ray observations of the z = 1.246 narrow-line radio quasar RX J1011.2+5545 serendipitously discovered by ROSAT. The flat X-ray spectrum previously measured by ROSAT and ASCA is shown to be the result of a steep ? 1.8 power-law spectrum seen through a moderate intrinsic absorbing column (N H ? 4 × 1021 cm?2). The position of the X-ray source is entirely coincident with the nucleus of the radio source that we have resolved in new sensitive VLA observations at 3.6 and 6 cm, implying that scattering in the radio lobes is not responsible for the bulk of X-ray emission. In the EPIC pn image, a faint patch of X-ray emission is apparent 14 arcsec to the north-east of the main X-ray source. The former is positionally coincident with an apparently extended optical object with R ? 21.9, but there is no associated radio emission, thus ruling out the possibility that this represents a hotspot in a jet emanating from the primary X-ray source. No reflection features are detected in the X-ray spectrum of the narrow-line radio quasar, although an Fe line with an equivalent width of up to 600 eV cannot be ruled out.The work reported herein is based partly on observations obtained with XMM–Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and the USA (NASA). The NOT telescope is operated by the Nordic Optical Telescope Scientific Association on the spanish Observatorio del Roque de los Muchachos of the Instituto de Astrof´ısica de Canarias. We are grateful to the service support for conducting the optical observations. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. We acknowledge financial support by the Ministerio de Ciencia y Tecnolog´ıa (Spain), under grants AYA2000-1690 (XB, FJC, MTC), AYA2002-03326 (RC, JIGS) and AYA2001-3092 (MR, JMP). MR and JMP acknowledge also partial support by the European Regional Development Fund (ERDF/FEDER). During this work, MR has been supported by a fellowship from CIRIT (Generalitat de Catalunya, ref. 1999 F I 00199

Discovery of an X-ray-selected radio-loud obscured AGN at z = 1.246

We have discovered an obscured active galaxy at redshift z = 1 .246 identified with the ROSAT X-ray source RX J1011.2+5545. We report on multiwavelength observations of this source and discuss its X-ray, optical and radio properties. This is the first X-ray selected, obscured active galaxy at high redshift to be shown to be radio-loud, with a radio counterpart exhibiting a classical double-lobe morphology.ACKNOWLEDGMENTS XB and RC were visiting astronomers of the CentroAstron´omico Hispano-Alem´an, Calar Alto, operated by the Max-Planck-Institute for Astronomy, Heidelberg jointly with the Spanish ‘Comisi´on Nacional de Astronom´ıa’. The William Herschel Telescope is operated on the island of La Palma by the Isaac Newton Group in the spanish Observatorio del Roque de los Muchachos of the Instituto de Astrof´ısica de Canarias. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration. XB, RC, MTC and JIGS acknowledge financial support by the DGES under project PB95-012

Exploring X-ray and radio emission of type 1 AGN up to z ~ 2.3

Context. X-ray emission from active galactic nuclei (AGN) is dominated by the accretion disk around a supermassive black hole. The radio luminosity, however, has not such a clear origin except in the most powerful sources where jets are evident. The origin (and even the very existence) of the local bi-modal distribution in radio-loudness is also a debated issue. Aims. By analysing X-ray, optical and radio properties of a large sample of type 1 AGN and quasars (QSOs) up to z > 2, where the bulk of this population resides, we aim to explore the interplay between radio and X-ray emission in AGN, in order to further our knowledge on the origin of radio emission, and its relation to accretion. Methods. We analyse a large (~800 sources) sample of type 1 AGN and QSOs selected from the 2XMMi XMM-Newton X-ray source catalogue, cross-correlated with the SDSS DR7 spectroscopic catalogue, covering a redshift range from z ~ 0.3 to z ~ 2.3. Supermassive black hole masses are estimated from the Mg II emission line, bolometric luminosities from the X-ray data, and radio emission or upper limits from the FIRST catalogue. Results. Most of the sources accrete close to the Eddington limit and the distribution in radio-loudness does not appear to have a bi-modal behaviour. We confirm that radio-loud AGN are also X-ray loud, with an X-ray-to-optical ratio up to twice that of radio-quiet objects, even excluding the most extreme strongly jetted sources. By analysing complementary radio-selected control samples, we find evidence that these conclusions are not an effect of the X-ray selection, but are likely a property of the dominant QSO population. Conclusions. Our findings are best interpreted in a context where radio emission in AGN, with the exception of a minority of beamed sources, arises from very close to the accretion disk and is therefore heavily linked to X-ray emission. We also speculate that the radio-loud/radio-quiet dichotomy might either be an evolutionary effect that developed well after the QSO peak epoch, or an effect of incompleteness in small samples.Based on observations obtained with XMM-Newton (an ESA science mission with instruments and contributions directly funded by ESA Member States and the USA, NASA). Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the US Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS Web Site is http://www.sdss.org/. The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. This research has made use of NASA’s Astrophysics Data System. The research uses the interactive graphical viewer and editor for tabular data TOPCAT (http://www.starlink.ac.uk/topcat/) and its command-line counterpart STILTS (http://www.starlink.ac.uk/stilts/). We warmly thank the referee for her/his suggestions that significantly improved the paper. L.B. acknowledges support from the Spanish Ministry of Science and Innovation through a “Juan de la Cierva” fellowship. Financial support for this work was provided by the Spanish Ministry of Economy and Competitiveness through research grant AYA2010-21490-C02-01 FJHH acknowledges support from CSIC through the undergraduate research programme “JAE-Introducción a la investigación”

Averaging the AGN X-ray spectra from deep Chandra fields

Context. The emission line most often observed in the X-ray spectra of active galactic nuclei (AGN) is Fe Kα. It is known that it can be broadened and deformed by relativistic effects if emitted close enough to the central super massive black hole (SMBH). Recent statistical studies of the X-ray spectra of AGN samples have found that a narrow Fe line is ubiquitous, while whether the broad features are as common it is still uncertain. Aims. We present here the results of an investigation on the characteristics of the Fe line in the average X-ray spectra of AGN in deep Chandra fields. Methods. The average spectrum of the AGN was computed using Chandra spectra with more than 200 net counts from the AEGIS, Chandra deep field north (CDFN) and Chandra deep field south (CDFS) surveys. The sample spans a broader range of X-ray luminosities than other samples studied with stacking methods up to z 3.5. We analyzed the average spectra of this sample using our own averaging method, checking the results against extensive simulations. Subsamples defined in terms of column density of the local absorber, redshift, and luminosity were also investigated. Results. We found a very significant Fe line with a narrow profile in all our samples and in almost all the subsamples that we constructed. The equivalent width of the narrow line estimated in the average spectrum of the full sample is 74 eV. In the subsample of AGN with L < 1.43 × 1044 erg s−1 and z < is 108 eV.Financial support for this work was provided by the Spanish Ministry of Science and Innovation through the grants AYA2009-08059 and AYA2010-21490-C02-01. The authors acknowledge the computer resources, technical expertise, and assistance provided by the Spanish Supercomputing Network (RES) node (Altamira) at the Universidad de Cantabria in Santander; we especially thank Luis Cabellos for the technical user support. We thank Prof. Andrea Comastri and Prof. Giorgio Matt, for useful comments. This research made use of data obtained from the Chandra Data Archive and the Chandra Source Catalog, and software provided by the Chandra X-ray Center (CXC) in the application of the package CIAO. This study made use of data from AEGIS, a multiwavelength sky survey conducted with the Chandra, GALEX, Hubble, Keck, CFHT, MMT, Subaru, Palomar, Spitzer, VLA, and other telescopes and supported in part by the NSF, NASA, and the STFC. This research made use of NASA’s Astrophysics Data System