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A multi-epoch, multi-instrument analysis of the Seyfert 1 galaxy HE 0436-4717 is conducted using optical to X-ray data from XMM-Newton and Swift (including the Burst Alert Telescope). Fitting of the UV-to-X-ray spectral energy distribution shows little evidence of extinction and the X-ray spectral analysis does not confirm previous reports of deep absorption edges from O VIII. HE 0436-4717 is a 'bare' Seyfert with negligible line-of-sight absorption making it ideal to study the central X-ray emitting region. Three scenarios were considered to describe the X-ray data: partial covering absorption, blurred reflection, and soft Comptonization. All three interpretations describe the 0.5-10.0 keV spectra well. Extrapolating the models to 100 keV results in poorer fits for the partial covering model. When also considering the rapid variability during one of the XMM-Newton observations, the blurred reflection model appears to describe all the observations in the most self-consistent manner. If adopted, the blurred reflection model requires a very low iron abundance in HE 0436-4717. We consider the possibilities that this is an artefact of the fitting process, but it appears possible that it is intrinsic to the object. [ABSTRACT FROM AUTHOR]

ABSTRACT We present a time, spectral and imaging analysis of the X-ray reflector in NGC 4945, which reveals its geometrical and physical structure with unprecedented detail. NGC 4945 hosts one of the brightest AGN in the sky above 10 keV, but it is only visible through its reflected/scattered emission below 10 keV, due to absorption by a column density of ∼4 × 1024 cm−2. A new Suzaku campaign of five observations spanning ∼6 months, together with past XMM-Newton and Chandra observations, shows a remarkable constancy (within <10 per cent) of the reflected component. Instead, Swift-BAT reveals strong intrinsic variability on time-scales longer than 1 yr. Modelling the circumnuclear gas as a thin cylinder with the axis on the plane of the sky, we show that the reflector is at a distance ≥30-50 pc, well within the imaging capabilities of Chandra at the distance of NGC 4945 (1 arcsec ∼18 pc). Accordingly, the Chandra imaging reveals a resolved, flattened, ∼150 pc long clumpy structure, whose spectrum is fully due to cold reflection of the primary AGN emission. The clumpiness may explain the small covering factor derived from the spectral and variability properties. [ABSTRACT FROM AUTHOR]

MCG–6-30-15 is the archetypal example of a type I active galaxy showing broad ‘red-wing’ emission in its X-ray spectrum at energies below the 6.4 keV Fe Kα emission line and a continuum excess above 20 keV. Miller et al. showed that these spectral features could be caused by clumpy absorbing material, but Reynolds et al. have argued that the observed Fe Kα line luminosity is inconsistent with this explanation unless the global covering factor of the absorber(s) is very low. However, the Reynolds et al. calculation effectively considers the only source of opacity to be the Fe K bound–free transition and neglects the opacity at the line energy: correction to realistic opacity decreases the predicted line flux by a large factor. We also discuss the interpretation of the covering factor and the possible effect of occultation by the accretion disc. Finally, we consider a model for MCG–6-30-15 dominated by clumpy absorption, which is consistent with a global covering factor of 0.45, although models that include the effects of Compton scattering are required to reach a full understanding. Variations in covering fraction may dominate the observed X-ray spectral variability. [ABSTRACT FROM AUTHOR]

We present a new time-dependent inhomogeneous jet model of non-thermal blazar emission, which reproduces the entire spectral energy distribution together with the rapid gamma-ray variability. Ultrarelativistic leptons are injected at the base of a jet and propagate along the jet structure. We assume continuous reacceleration and cooling, producing a relativistic quasi-maxwellian (or ‘pile-up’) particle energy distribution. The synchrotron and synchrotron self-Compton jet emissivity are computed at each altitude. Klein–Nishina effects as well as intrinsic gamma–gamma absorption are included in the computation. Due to the pair production optical depth, considerable particle density enhancement can occur, particularly during flaring states. Time-dependent jet emission can be computed by varying the particle injection, but due to the sensitivity of pair production process, only small variations of the injected density are required during the flares. The stratification of the jet emission, together with a pile-up distribution, allows significantly lower bulk Lorentz factors, compared to one-zone models. Applying this model to the case of PKS and its big TeV flare observed in 2006, we can reproduce simultaneously the average broad-band spectrum of this source as well as the TeV spectra and TeV light curve of the flare with bulk Lorentz factor lower than 15. [ABSTRACT FROM AUTHOR]

Simple one-zone homogeneous synchrotron self-Compton models have severe difficulties in explaining the TeV emission observed in the radio galaxy M87. Also, the site the TeV emission region is uncertain: it could be the unresolved jet close to the nucleus, analogously to what is proposed for blazars, or it could be the active knot, called HST-1, tens of parsec away. We explore the possibility that the TeV emission of M87 is produced in the misaligned subparsec-scale jet. We base our modelling on a structured jet, with a fast spine surrounded by a slower layer. In this context the main site responsible for the emission of the TeV radiation is the layer, while the (debeamed) spine accounts for the emission from the radio to the GeV band: therefore we expect a more complex correlation with the TeV component than that expected in one-zone scenarios, in which both components are produced by the same region. Observed from small angles, the spine would dominate the emission, with an overall spectral energy distribution close to those of BL Lac objects with a synchrotron peak located at low energy. [ABSTRACT FROM AUTHOR]

We report on the radio-quiet quasar SDSS J2125−0813 which obviously emits optical Fe ii emission lines and double-peaked broad Balmer emission lines. Using the accretion disc model for double-peaked, broad, low-ionization emission lines, we reproduce the composite line spectra at the optical band between 4100 and 5600 Å. Broad Fe ii emission lines can be fitted simultaneously with the broad Hβ and Mg i lines, such that all broad lines have an elliptical disc profile with the same disc parameters. This result indicates that the optical Fe ii emission lines originate from the accretion disc near the central black hole which produces the double-peaked broad Balmer emission lines. Furthermore, we find that the object has a dimensionless accretion rate , which is much larger than the accretion rate for the advection-dominated accretion flow (ADAF) mode, and that the energy budget of the accretion disc is enough to power the double-peaked broad Balmer emission lines. [ABSTRACT FROM AUTHOR]

High-velocity outflows from active galactic nuclei are a well-known phenomenon in terms of the broad absorption lines seen in the ultraviolet/optical. More recently, similar, possibly related, outflows have been reported in the X-ray. The most extreme example is seen in the nearby, luminous QSO PDS 456, which displays a massive, high-velocity (50 000 km s−1), high-ionization X-ray outflow of . Here we present the ultraviolet spectrum of PDS 456 as observed by the Hubble Space Telescope. We find that the ultraviolet spectrum is also extreme, displaying very broad emission lines, with C ivλ1549 blueshifted by 5000 km s−1 and a broad Lyα absorption trough blueshifted by 14 000–24 000 km s−1. No strong, broad high-ionization absorption features are seen. We interpret the combined ultraviolet and X-ray spectrum of PDS 456 as the signature of a decelerating, cooling outflow, which may be driven by radiation and/or magnetic field. This outflow may be the source of some of the broad emission- and absorption-line gas. [ABSTRACT FROM AUTHOR]

We apply a simple model, tested on local ultraluminous infrared galaxies (ULIRGs), to disentangle the active galactic nuclei (AGN) and starburst contributions in submillimetre and 24 μm-selected ULIRGs observed with the Spitzer–Infrared Spectrograph spectrometer. We quantitatively estimate the average AGN contribution to the stacked μm rest-frame spectra of these sources in different luminosity and redshift ranges and, under the assumption of similar infrared-to-bolometric ratios as in local ULIRGs, the relative AGN/starburst contributions to the total infrared luminosity. Though the starburst component is always dominant in submillimetre-selected ULIRGs, we find a significant increase of the AGN contribution at redshift with respect to lower z objects. Finally, we quantitatively confirm that the mid-infrared emission of 24 μm-selected ULIRGs is dominated by the AGN component, but the starburst component contributes significantly to the bolometric luminosity. [ABSTRACT FROM AUTHOR]

We report the serendipitous discovery of a previously unknown quasar at 10.5 arcsec from Q2225-403 . The observation of the broad emission line of Mg ii and of the surrounding Fe ii multiplets indicates that the companion quasar is at . The spectrum of Q2225-403 shows a number of absorption lines, the most noteworthy is the Mg ii line at the same redshift of the companion, suggesting that we are probing the gas within the halo ∼80 kpc from the closer quasar. From high-resolution near-infrared images, we were able to resolve the host galaxies of the two quasars. Basing on the known surface density of quasars in the 2dF survey, we estimate that the probability of finding such a close pair is ≲1 per cent. [ABSTRACT FROM AUTHOR]

We present an analysis of the 5–8 μm Spitzer-IRS spectra of a sample of 68 local ultraluminous infrared galaxies (ULIRGs). Our diagnostic technique allows a clear separation of the active galactic nucleus (AGN) and starburst (SB) components in the observed mid-infrared emission, and a simple analytic model provides a quantitative estimate of the AGN/SB contribution to the bolometric luminosity. We show that AGN are ∼30 times brighter at 6 μm than SBs with the same bolometric luminosity, so that even faint AGN can be detected. Star formation events are confirmed as the dominant power source for extreme IR activity, since ∼85 per cent of ULIRG luminosity arises from the SB component. None the less an AGN is present in the majority (46/68) of our sources. [ABSTRACT FROM AUTHOR]

We present X-ray observations of the hyperluminous infrared galaxy (HLIRG) IRAS 00182− 7112 obtained using the XMM–Newton EPIC camera. A luminous hard X-ray source coincident with the nucleus is revealed, along with weaker soft X-ray emission which may be extended or offset from the hard emission. The EPIC spectrum is extremely flat and shows Fe Kα emission with very high equivalent width: both are typical characteristics of a buried, Compton-thick active galactic nucleus (AGN) which is seen only in scattered light. Perhaps the most remarkable characteristic of the spectrum is that the Fe Kα line energy is that of He-like iron, making IRAS 00182−7112 the first hidden AGN known to be dominated by ionized, Compton-thick reflection. Taking an appropriate bolometric correction, we find that this AGN could easily dominate the far-infrared (FIR) energetics. The nuclear reflection spectrum is seen through a relatively cold absorber with column density consistent with recent Spitzer observations. The soft X-ray emission, which may be thermal in nature and associated with star-forming activity, is seen unabsorbed. The soft X-rays and weak polycyclic aromatic hydrocarbon features both give estimates of the star formation rate , insufficient to power the FIR emission and supportive of the idea that this HLIRG is AGN-dominated. [ABSTRACT FROM AUTHOR]