The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. http://dspace-roma3.caspur.it:80 2013-05-21T13:29:25Z 2013-05-21T13:29:25Z Bianchi, Stefano La Franca, Fabio Matt, Giorgio Guainazzi, Matteo Jimenez Bailon, Elena Longinotti, Anna Lia Nicastro, Fabrizio Pentericci, Laura http://hdl.handle.net/2307/273 2011-12-22T13:35:28Z 2008-06-30T22:00:00Z

<Title>A broad-line region origin for the iron Kα line in NGC 7213</Title> <Authors>Bianchi, Stefano; La Franca, Fabio; Matt, Giorgio; Guainazzi, Matteo; Jimenez Bailon, Elena; Longinotti, Anna Lia; Nicastro, Fabrizio; Pentericci, Laura</Authors> <Issue Date>2008-07</Issue Date> <Is part of>Monthly Notices of the Royal Astronomical Society: Letters</Is part of> <Volume>389</Volume> <Pages>52-56</Pages> <Abstract>The X-ray spectrum of NGC 7213 is known to present no evidence for Compton reflection, a unique result among bright Seyfert 1s. The observed neutral iron Kα line, therefore, cannot be associated with a Compton-thick material, like the disc or the torus, but is due to Compton-thin gas, with the broad-line region (BLR) as the most likely candidate. To check this hypothesis, a long Chandra High-Energy Transmission Grating observation, together with a quasi-simultaneous optical spectroscopic observation at the ESO NTT EMMI were performed. We found that the iron line is resolved with a full width at half-maximum (FWHM) = 2400+1100-600kms-1, in perfect agreement with the value measured for the broad component of the Hα, 2640+110-90kms-1. Therefore, NGC 7213 is the only Seyfert 1 galaxy whose iron Kα line is unambiguously produced in the BLR. We also confirmed the presence of two ionized iron lines and studied them in greater detail than before. The resonant line is the dominant component in the Fe XXV triplet, therefore suggesting an origin in collisionally ionized gas. If this is the case, the blueshift of around 1000kms-1 of the two ionized iron lines could be the first measure of the velocity of a starburst wind from its X-ray emission.</Abstract>

2008-06-30T22:00:00Z Lamastra, Alessandra Bianchi, Stefano Matt, Giorgio Perola, Giuseppe Cesare Barcons, X. Carrera, F. J. http://hdl.handle.net/2307/391 2011-12-22T13:34:34Z 2009-08-31T22:00:00Z

<Title>The bolometric luminosity of type 2 AGN from extinction-corrected [OIII]: no evidence of Eddington-limited sources</Title> <Authors>Lamastra, Alessandra; Bianchi, Stefano; Matt, Giorgio; Perola, Giuseppe Cesare; Barcons, X.; Carrera, F. J.</Authors> <Issue Date>2009-09</Issue Date> <Is part of>Astronomy & Astrophysics</Is part of> <Volume>504</Volume> <Pages>73-79</Pages> <Abstract>Context. There have been recent claims that a significant fraction of type 2 AGN accrete close to or even above the Eddington limit. In type 2 AGN, the bolometric luminosity (L-b) is generally inferred from the [OIII] emission line luminosity (L-OIII). The key issue in estimating the bolometric luminosity in these AGN, is therefore to know the bolometric correction to be applied to L-OIII. A complication arises from the observed L-OIII being affected by extinction, most likely from dust within the narrow line region. The extinction-corrected [OIII] luminosity (L-OIII(c)) is a better estimator of the nuclear luminosity than L-OIII. However, only the bolometric correction to be applied to the uncorrected L-OIII has been evaluated so far. Aims. This paper is devoted to estimating the bolometric correction C-OIII = L-b/L-OIII(c) for deriving the Eddington ratios for the type 2 AGN in a sample of SDSS objects. Methods. We collected 61 sources from the literature with reliable estimates of both L-OIII(c) and X-ray luminosities (L-X). To estimate C-OIII, we combined the observed correlation between L-OIII(c) and L-Xwith the X-ray bolometric correction. Results. In contrast to previous studies, we found a linear correlation between L-OIII(c) and L-X. We estimated C-OIII using an earlier luminosity-dependent X-ray bolometric correction, and we found a mean value of C-OIII in the luminosity ranges log L-OIII = 38-40, 40-42, and 42-44 of 87, 142, and 454, respectively. We used it to calculate the Eddington ratio distribution of type 2 SDSS AGN at 0.3 < z < 0.4 and found that these sources are not accreting near their Eddington limit, contrary to previous claims.</Abstract>

2009-08-31T22:00:00Z Risaliti, G. Braito, V. Laparola, V. Bianchi, Stefano Elvis, M. Fabbiano, G. Maiolino, R. Matt, Giorgio Reeves, J. Salvati, M. Wang, J. http://hdl.handle.net/2307/393 2011-12-22T13:34:34Z 2009-10-31T23:00:00Z

<Title>A strong excess in the 20-100 kev emission of ngc 1365</Title> <Authors>Risaliti, G.; Braito, V.; Laparola, V.; Bianchi, Stefano; Elvis, M.; Fabbiano, G.; Maiolino, R.; Matt, Giorgio; Reeves, J.; Salvati, M.; Wang, J.</Authors> <Issue Date>2009-11</Issue Date> <Is part of>Astrophysical Journal Letters</Is part of> <Volume>705</Volume> <Pages>L1–L5</Pages> <Abstract>We present a new Suzaku observation of the obscured active galacticnucleus in NGC 1365, revealing an unexpected excess of X-rays above 20keV of at least a factor similar to 2 with respect to the extrapolationof the best-fitting 3-10 keV model. Additional Swift-BAT andIntegral-IBIS observations show that the 20-100 keV is concentratedwithin similar to 1.5 arcmin from the center of the galaxy, and is notsignificantly variable on timescales from days to years. A comparisonof this component with the 3-10 keV emission, which is characterized bya rapidly variable absorption, suggests a complex structure of thecircumnuclear medium, consisting of at least two distinct componentswith rather different physical properties, one of which covers >80% ofthe source with a column density N-H similar to 3-4x10(24) cm(-2). Analternative explanation is the presence of a double active nucleus inthe center of NGC 1365.</Abstract>

2009-10-31T23:00:00Z Risaliti, Guido Miniutti, Giovanni Elvis, Martin Fabbiano, Giuseppina Salvati, Marco Baldi, Alessandro Braito, Valentina Bianchi, Stefano Matt, Giorgio Reeves, James Soria, Roberto Zezas, Andreas http://hdl.handle.net/2307/295 2011-12-22T13:34:55Z 2009-04-30T22:00:00Z

<Title>Variable partial covering and a relativistic iron line in NGC 1365</Title> <Authors>Risaliti, Guido; Miniutti, Giovanni; Elvis, Martin; Fabbiano, Giuseppina; Salvati, Marco; Baldi, Alessandro; Braito, Valentina; Bianchi, Stefano; Matt, Giorgio; Reeves, James; Soria, Roberto; Zezas, Andreas</Authors> <Issue Date>2009-05-01</Issue Date> <Is part of>Astrophysical Journal</Is part of> <Volume>696</Volume> <Pages>160-171</Pages> <Abstract>We present a complete analysis of the hard X-ray (2-10 keV) properties of the Seyfert galaxy NGC 1365, based on a 60 ks XMM-Newton observation performed in 2004 January. The two main results are as follows. (1) We detect an obscuring cloud with N-H similar to 3.5 x 10(23) cm(-2) crossing the line of sight in similar to 25 ks. This implies a dimension of the X-ray source not larger than a few 1013 cm and a distance of the obscuring cloud of the order of 1016 cm. Adopting the black hole mass M-BH estimated from the M-BH-velocity dispersion relation, the source size is D-S < 20R(G) and the distance and density of the obscuring clouds are R similar to 3000-10,000R(G) and n similar to 10(10) cm(-3), i.e., typical values for broad-line region clouds.(2) An iron emission line with a relativistic profile is detected with high statistical significance. A time-integrated fit of the line+continuum reflection components suggests a high iron abundance(approximately three times solar) and an origin of these components in the inner part (within similar to 10R(G)) of the accretion disk, in agreement with the small source size inferred from the analysis of the absorption variability.</Abstract>

2009-04-30T22:00:00Z Risaliti, Guido Salvati, Marco Elvis, Martin Fabbiano, Giuseppina Baldi, Alessandro Bianchi, Stefano Braito, Valentina Guainazzi, Matteo Matt, Giorgio Miniutti, Giovanni Reeves, James Soria, Roberto Zezas, Andreas http://hdl.handle.net/2307/305 2011-12-22T13:34:34Z 2008-12-31T23:00:00Z

<Title>The XMM-Newton long look of NGC 1365: uncovering of the obscured X-raysource</Title> <Authors>Risaliti, Guido; Salvati, Marco; Elvis, Martin; Fabbiano, Giuseppina; Baldi, Alessandro; Bianchi, Stefano; Braito, Valentina; Guainazzi, Matteo; Matt, Giorgio; Miniutti, Giovanni; Reeves, James; Soria, Roberto; Zezas, Andreas</Authors> <Issue Date>2009</Issue Date> <Is part of>Monthly notices of the royal astronomical society</Is part of> <Volume>393</Volume> <Pages>L1</Pages> <Abstract>We present an analysis of the extreme obscuration variability observedduring an XMM-Newton 5-d continuous monitoring of the active galacticnuclei (AGN) in NGC 1365. The source was in a reflection-dominatedstate in the first similar to 1.5 d, then a strong increase in the 7-10keV emission was observed in similar to 10 h, followed by a symmetricdecrease. The spectral analysis of the different states clearly showsthat this variation is due to an uncovering of the X-ray source. Fromthis observation, we estimate a size of the X-ray source D-S < 10(13)cm, a distance of the obscuring clouds R similar to 10(16) cm and adensity n similar to 10(11) cm(-3). These values suggest that the X-rayabsorption/reflection originates from the broad-line region clouds.This is also supported by the resolved width of the iron narrow K alphaemission line, consistent with the width of the broad H beta line.</Abstract>

2008-12-31T23:00:00Z Panessa, F. Carrera, F. J. Bianchi, Stefano Corral, A. Gastaldello, F. Barcons, X. Bassani, L. Matt, Giorgio Monaco, L. http://hdl.handle.net/2307/362 2011-12-22T13:34:34Z 2009-08-09T22:00:00Z

<Title>Unabsorbed Seyfert 2 galaxies: the case of 'naked' AGN</Title> <Authors>Panessa, F.; Carrera, F. J.; Bianchi, Stefano; Corral, A.; Gastaldello, F.; Barcons, X.; Bassani, L.; Matt, Giorgio; Monaco, L.</Authors> <Issue Date>2009-08-10</Issue Date> <Is part of>Monthly Notices of the Royal Astronomical Society</Is part of> <Volume>398</Volume> <Pages>1951-1960</Pages> <Abstract>Hawkins reported on a class of 'naked' active galactic nuclei (AGN)characterized by strong amplitude optical brightness variability and the complete absence of broad emission lines in the optical spectrum. The variability suggests that the nucleus is seen directly, however the absence of broad lines contradicts the simple formulation of Unified Models for AGN. We present the results of quasi-simultaneous spectroscopic observations with XMM-Newton and New Technology Telescope(NTT) (La Silla) of two 'naked' AGN. We confirm the 'naked' nature of Q2131-427 for which no broad emission line components have been detected in the optical spectrum and its X-ray spectrum shows no signs of intrinsic absorption. The optical and X-ray mismatch in this source cannot be ascribed to a high nuclear dust-to-gas ratio and a Compton-thick nature is ruled out on the basis of the high F-X/F-[OIII] ratio. The broad-line region (BLR) may be completely absent in this source, possibly as a consequence of its low Eddington ratio. On the other hand, the optical spectrum of Q2130-431 shows H alpha and H beta broad emission line components, revealing the presence of a BLR. A mild X-ray absorption is expected in intermediate type 1.8 Seyfert galaxies like Q2130-431, however we put a very low upper limit on the column density (<2 x 10(20) cm(-2)), also the low Balmer decrement suggests that the BLR itself does not suffer from reddening. We propose that in this object the BLR is intrinsically weak, making a case of 'true' intermediate Seyfert galaxy. We also report on the X-ray detection of the Abell 3783 galaxy cluster in the XMM-Newton field of view of the Q2131-427 observation.</Abstract>

2009-08-09T22:00:00Z Bianchi, Stefano Bonilla, N. Fonseca Guainazzi, Matteo Matt, Giorgio Ponti, Gabriele http://hdl.handle.net/2307/384 2011-12-22T13:34:34Z 2008-12-31T23:00:00Z

<Title>CAIXA: a catalogue of AGN in the XMM-Newton archive II. Multiwavelength correlations</Title> <Authors>Bianchi, Stefano; Bonilla, N. Fonseca; Guainazzi, Matteo; Matt, Giorgio; Ponti, Gabriele</Authors> <Issue Date>2009</Issue Date> <Is part of>Astronomy & Astrophysics</Is part of> <Volume>501</Volume> <Pages>915-924</Pages> <Abstract>Aims. The availability of large amounts of multiwavelength data allows us to perform an extensive statistical analysis to look for correlations between different parameters of AGN. The physical implications of these correlations, when considered within the framework of current AGN models, can be enlightening in the resolution of the problems and the open issues which still characterise this class of sources. Methods. We presented CAIXA, a Catalogue of AGN in the XMM-Newton Archive, in a companion paper. It consists of radio-quiet X-ray unobscured sources, which cover a range in X-ray luminosities between L2-10keV = 2.0 x 10(41) and 3.9 x 10(46) erg s(-1), and in redshift from z = 0.002 to z = 4.520. Here, a systematic search for correlations between the X-ray spectral properties and the multiwavelength data was performed for the sources in CAIXA. All the significant (>99.9%confidence level) correlations are discussed along with their physical implications for current models of AGN. Results. Two main correlations are discussed in this paper: a) a very strong anti-correlation between the FWHM of the H beta optical line and the ratio between the soft and the hard X-ray luminosity. Although similar anti-correlations between optical line width and X-ray spectral steepness have already been discussed in the literature, we consider the formulation we present in this paper as more fundamental, as it links model-independent quantities. Coupled with a strong anti-correlation between the V to hard X-ray flux ratio and the H betaFHWM, it supports scenarios for the origin of the soft excess in AGN, which require strong suppression of the hard X-ray emission; b) a strong (and expected) correlation between the X-ray luminosity and the black hole mass. Its slope, flatter than 1, is consistent with Eddington ratio-dependent bolometric corrections. Moreover, we critically review through various statistical tests the role that distance biases play in the strong radio to X-ray luminosity correlation found in CAIXA and elsewhere; we conclude that only complete, unbiased samples should be used to draw observational constraints on the origin of radio emission in radio-quiet AGN.</Abstract>

2008-12-31T23:00:00Z Bianchi, Stefano Piconcelli, Enrico Chiaberge, Marco Jimenez Bailon, Elena Matt, Giorgio Fiore, Fabrizio http://hdl.handle.net/2307/325 2011-12-22T13:35:27Z 2009-03-31T22:00:00Z

<Title>How complex is the obscuration in active galactic nuclei? new cluesfrom the suzaku monitoring of the x-ray absorbers in ngc 7582</Title> <Authors>Bianchi, Stefano; Piconcelli, Enrico; Chiaberge, Marco; Jimenez Bailon, Elena; Matt, Giorgio; Fiore, Fabrizio</Authors> <Issue Date>2009-04</Issue Date> <Is part of>Astrophysical Journal</Is part of> <Volume>695</Volume> <Pages>781-787</Pages> <Abstract>We present the results of a Suzaku monitoring campaign of the Seyfert 2galaxy, NGC 7582. The source is characterized by very rapid (ontimescales even lower than a day) changes of the column density of aninner absorber, together with the presence of constant componentsarising as reprocessing from a Compton-thick material. The best-fittingscenario implies important modifications to the zeroth-order view ofUnified Models. While the existence of a pc-scale torus is needed inorder to produce a constant Compton reflection component and an ironKa-emission line, in this Seyfert 2 galaxy this is not viewed along theline of sight. On the other hand, the absorption of the primarycontinuum is due to another material, much closer to the black hole,roughly at the distance of the broad-line region, which can produce theobserved rapid spectral variability. On top of that, the constantpresence of a 10(22) cm(-2) column density can be ascribed to thepresence of a dust lane, extended on a galactic scale, as previouslyconfirmed by Chandra. There is now mounting evidence that complexity inthe obscuration of active galactic nuclei (AGNs) may be the rule ratherthan the exception. We therefore propose to modify the UnificationModel, adding to the torus the presence of two furtherabsorbers/emitters. Their combination along the line of sight canreproduce all the observed phenomenology.</Abstract>

2009-03-31T22:00:00Z Bianchi, Stefano Guainazzi, Matteo Matt, Giorgio Bonilla, N. Fonseca Ponti, Gabriele http://hdl.handle.net/2307/285 2011-12-22T13:35:28Z 2009-01-31T23:00:00Z

<Title>CAIXA: a catalogue of AGN in the XMM-Newton archive I. Spectral analysis</Title> <Authors>Bianchi, Stefano; Guainazzi, Matteo; Matt, Giorgio; Bonilla, N. Fonseca; Ponti, Gabriele</Authors> <Issue Date>2009-02</Issue Date> <Is part of>Astronomy & Astrophysics</Is part of> <Volume>495</Volume> <Pages>421-430</Pages> <Abstract>Aims. We present CAIXA, a Catalogue of AGN In the XMM-Newton Archive.It consists of all the radio-quiet X-ray unobscured (N-H < 2 x 10(22)cm(-2)) active galactic nuclei (AGN) observed by XMM-Newton in targetedobservations, whose data are public as of March 2007. With its 156sources, this is the largest catalogue of high signal-to-noise X-rayspectra of AGN.Methods. All the EPIC pn spectra of the sources in CAIXA were extractedhomogeneously, and a baseline model was applied in order to derivetheir basic X-ray properties. These data are complemented bymultiwavelength data found in the literature: black hole masses, fullwidth half maximum (FWHM) of H beta, radio and optical fluxes.Results. Here we describe our homogeneous spectral analysis of theX-ray data in CAIXA and present all the results on the parametersadopted in our best-fit models.</Abstract>

2009-01-31T23:00:00Z Matt, Giorgio Bianchi, Stefano Awaki, Hisamitsu Comastri, Andrea Guainazzi, Matteo Iwasawa, Kazushi Jimenez-Bailon, Elena Nicastro, Fabrizio http://hdl.handle.net/2307/286 2011-12-22T13:35:28Z 2009-02-28T23:00:00Z

<Title>Suzaku observation of the Phoenix galaxy</Title> <Authors>Matt, Giorgio; Bianchi, Stefano; Awaki, Hisamitsu; Comastri, Andrea; Guainazzi, Matteo; Iwasawa, Kazushi; Jimenez-Bailon, Elena; Nicastro, Fabrizio</Authors> <Issue Date>2009-03</Issue Date> <Is part of>Astronomy & Astrophysics</Is part of> <Volume>496</Volume> <Pages>653-658</Pages> <Abstract>Context. In recent years, several Seyfert 2 galaxies have beendiscovered that change state when observed in X-rays a few years apart,switching from Compton-thin to reflection-dominated or viceversa.Aims. We observed a member of this class of "Changing-look" sources,the Phoenix galaxy, with Suzaku, with the aim of better understandingthe nature of the variations.Methods. The Suzaku spectrum was analyzed, and the results comparedwith previous ASCA and XMM-Newton observations.Results. The source was caught in a Compton-thin state, as inXMM-Newton, but differently from ASCA. Comparing the Suzaku andXMM-Newton observations, a variation in the column density of theabsorber on a time scale of years is discovered. A similar change, buton much shorter time scales (i.e. ks) may also explain the count-ratevariations during the Suzaku observations. A soft excess is alsopresent, likely due to continuum and line emission from photoionizedcircumnuclear matter.</Abstract>

2009-02-28T23:00:00Z