The BeppoSAX archive is currently the largest reservoir of high sensitivity simultaneous soft and hard-X ray data of Seyfert galaxies. From this database all the Seyfert galaxies (105 objects of ...which 43 are type I and 62 are type II) with redshift lower than 0.1 have been selected and analyzed in a homogeneous way. Taking advantage of the broad-band coverage of the BeppoSAX MECS and PDS instruments (~2-100 keV), the X-ray data so collected allow us to infer the average spectral properties of nearby Seyfert galaxies included in the original sample and, most notably the photon index (Γ ~ 1.8), the high-energy cut-off (Ec ~ 290 keV), and the relative amount of reflection (R ~ 1.0). The data collected have been used to test some basic assumptions of the unified scheme for active galactic nuclei. The distributions of the isotropic indicators used here (photon index, relative amount of reflection, high-energy cut-off and narrow FeKα energy centroid) are similar in type I and type II objects while the absorbing column and the iron line equivalent width significantly differ between the two classes of active galactic nuclei with type II objects displaying larger columns (NH ~ 3.7$\times$1022 and 6.1$\times$1023 cm-2 for type I and II objects respectively) and equivalent width (EW ~ 220 and 690 eV for type I and II sources respectively). Confirming previous results, the narrow FeKα line is consistent, in Seyfert 2, with being produced in the same matter responsible for the observed obscuration. These results support the basic picture of the unified model. Moreover, the presence of a X-ray Baldwin effect in Seyfert 1 has been measured using the 20-100 keV luminosity $(EW \propto L(20-100)^{-0.22\pm0.05})$. Finally, the possible presence of a correlation between the photon index and the amount of reflection is confirmed thus indicating thermal Comptonization as the most likely origin of the high energy emission for the active galactic nuclei included in the original sample.
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An atlas of high energy ($E\geq2$ keV) spectra of nearby ($z\leq0.1$) Seyfert galaxies observed with ${\it BeppoSAX}$ is presented. The data have been analyzed in an homogeneous way. The final sample ...contains ${\it BeppoSAX}$ MECS+PDS (LECS data were not used here) pointings of 113 objects. No useful X-ray data were present for eight targets. The catalog of X-ray spectra contains data for 43 type-I Seyfert (including Seyfert 1.0, 1.2, and 1.5) and for 62 type-II objects (including Seyfert 1.8, 1.9, and 2.0). A total of 163 X-ray spectra (84 for type-I and 79 for type-II objects) were analyzed, since some sources were observed several times. 81 sources were detected at high energy (above 10 keV) by the PDS: 39 are Seyfert I and 42 are Seyfert II. The broadband X-ray spectra covering the ~2–100 keV band are 130 in total. In a forthcoming paper, the statistical analysis of these data will be presented.
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The X-ray spectra of many active galactic nuclei (AGNs) show a soft X-ray excess below 1–2 keV on top of the extrapolated high-energy power law. The origin of this component is uncertain. It could be ...a signature of relativistically blurred, ionized reflection or the high-energy tail of thermal Comptonization in a warm (kT ~ 1 keV), optically thick (τ ≃ 10–20) corona producing the optical/UV to soft X-ray emission. The purpose of the present paper is to test the warm corona model on a statistically significant sample of unabsorbed, radio-quiet AGNs with XMM-Newton archival data, providing simultaneous optical/UV and X-ray coverage. The sample has 22 objects and 100 observations. We use two thermal Comptonization components to fit the broadband spectra, one for the warm corona emission and one for the high-energy continuum. In the optical/UV, we also include the reddening, the small blue bump, and the Galactic extinction. In the X-rays, we include a warm absorber and a neutral reflection. The model gives a good fit (reduced χ2 < 1.5) to more than 90% of the sample. We find the temperature of the warm corona to be uniformly distributed in the 0.1–1 keV range, while the optical depth is in the range ~10–40. These values are consistent with a warm corona covering a large fraction of a quasi-passive accretion disk, i.e., that mostly reprocesses the warm corona emission. The disk intrinsic emission represents no more than 20% of the disk total emission. According to this interpretation, most of the accretion power would be released in the upper layers of the accretion flow.
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It has been known for decades that the observed number of baryons in the local Universe falls about 30-40 per cent short
of the total number of baryons predicted
by Big Bang nucleosynthesis, as ...inferred
from density fluctuations of the cosmic microwave background and seen during the first 2-3 billion years of the Universe in the so-called 'Lyman α forest'
(a dense series of intervening H I Lyman α absorption lines in the optical spectra of background quasars). A theoretical solution to this paradox locates the missing baryons in the hot and tenuous filamentary gas between galaxies, known as the warm-hot intergalactic medium. However, it is difficult to detect them there because the largest by far constituent of this gas-hydrogen-is mostly ionized and therefore almost invisible in far-ultraviolet spectra with typical signal-to-noise ratios
. Indeed, despite large observational efforts, only a few marginal claims of detection have been made so far
. Here we report observations of two absorbers of highly ionized oxygen (O VII) in the high-signal-to-noise-ratio X-ray spectrum of a quasar at a redshift higher than 0.4. These absorbers show no variability over a two-year timescale and have no associated cold absorption, making the assumption that they originate from the quasar's intrinsic outflow or the host galaxy's interstellar medium implausible. The O VII systems lie in regions characterized by large (four times larger than average
) galaxy overdensities and their number (down to the sensitivity threshold of our data) agrees well with numerical simulation predictions for the long-sought warm-hot intergalactic medium. We conclude that the missing baryons have been found.
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We carried out a systematic analysis of time lags between X-ray energy bands in a large sample (32 sources) of unabsorbed, radio quiet active galactic nuclei (AGN), observed by XMM-Newton. The ...analysis of X-ray lags (up to the highest/shortest frequencies/time-scales), is performed in the Fourier-frequency domain, between energy bands where the soft excess (soft band) and the primary power law (hard band) dominate the emission. We report a total of 15 out of 32 sources displaying a high-frequency soft lag in their light curves. All 15 are at a significance level exceeding 97 per cent and 11 are at a level exceeding 99 per cent. Of these soft lags, seven have not been previously reported in the literature, thus this work significantly increases the number of known sources with a soft/negative lag. The characteristic time-scales of the soft/negative lag are relatively short (with typical frequencies and amplitudes of ν ∼ 0.07-4 × 10−3 Hz and τ ∼ 10-600 s, respectively), and show a highly significant ( 4σ) correlation with the black hole mass. The measured correlations indicate that soft lags are systematically shifted to lower frequencies and higher absolute amplitudes as the mass of the source increases. To first approximation, all the sources in the sample are consistent with having similar mass-scaled lag properties. These results strongly suggest the existence of a mass-scaling law for the soft/negative lag, that holds for AGN spanning a large range of masses (about 2.5 orders of magnitude), thus supporting the idea that soft lags originate in the innermost regions of AGN and are powerful tools for testing their physics and geometry.
ABSTRACT
Multimessenger astronomy received a great boost following the discovery of kilonova (KN) AT2017gfo, the optical counterpart of the gravitational wave source GW170817 associated with the ...short gamma-ray burst GRB 170817A. AT2017gfo was the first KN that could be extensively monitored in time using both photometry and spectroscopy. Previously, only few candidates have been observed against the glare of short GRB afterglows. In this work, we aim to search the fingerprints of AT2017gfo-like KN emissions in the optical/NIR light curves of 39 short GRBs with known redshift. For the first time, our results allow us to study separately the range of luminosity of the blue and red components of AT2017gfo-like kilonovae in short GRBs. In particular, the red component is similar in luminosity to AT2017gfo, while the blue KN can be more than 10 times brighter. Finally, we exclude a KN as luminous as AT2017gfo in GRBs 050509B and 061201.
Abstract
We present results from a comprehensive study of ultrafast outflows (UFOs) detected in a sample of 14 quasars, 12 of which are gravitationally lensed, in a redshift range of 1.41–3.91, near ...the peak of the active galactic nucleus (AGN) and star formation activity. New XMM-Newton observations are presented for six of them, which were selected to be lensed and contain a narrow absorption line (NAL) in their UV spectra. Another lensed quasar was added to the sample, albeit already studied because it was not searched for UFOs. The remaining seven quasars of our sample are known to contain UFOs. The main goals of our study are to infer the outflow properties of high-
z
quasars, constrain their outflow induced feedback, study the relationship between the outflow properties and the properties of the ionizing source, and compare these results to those of nearby AGN. Our study adds six new detections (> 99% confidence) of UFOs at
z
> 1.4, almost doubling the current number of cases. Based on our survey of six quasars selected to contain a NAL and observed with XMM-Newton, the coexistence of intrinsic UV NALs and UFOs is found to be significant in >83% of these quasars suggesting a link between multiphase AGN feedback properties of the meso- and microscale. The kinematic luminosities of the UFOs of our high-
z
sample are large compared to their bolometric luminosities (median of
L
K
/
L
Bol
≳ 50%). This suggests they provide efficient feedback to influence the evolution of their host galaxies and that magnetic driving may be a significant contributor to their acceleration.
X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet active galactic nuclei (AGNs). These have been detected essentially ...through blueshifted Fe XXV/XXV delta K-shell transitions. In the previous paper of this series we defined UFOs as those highly ionized absorbers with an outflow velocity higher than 10,000 km s--1 and assessed the statistical significance of the associated blueshifted absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. The present paper is an extension of that work. First, we report a detailed curve of growth analysis of the main Fe XXV/XXV delta transitions in photoionized plasmas. Then, we estimate an average spectral energy distribution for the sample sources and directly model the Fe K absorbers in the XMM-Newton spectra with the detailed Xstar photoionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35% and that the majority of the Fe K absorbers are indeed associated with UFOs. The outflow velocity distribution spans from ~10,000 km s--1 (~0.03c) up to ~100,000 km s--1 (~0.3c), with a peak and mean value of ~42,000 km s--1 (~0.14c). The ionization parameter is very high and in the range log Delta *x ~ 3-6 erg s--1 cm, with a mean value of log Delta *x ~ 4.2 erg s--1 cm. The associated column densities are also large, in the range N H ~ 1022-1024 cm--2, with a mean value of N H ~ 1023 cm--2. We discuss and estimate how selection effects, such as those related to the limited instrumental sensitivity at energies above 7 keV, may hamper the detection of even higher velocities and higher ionization absorbers. We argue that, overall, these results point to the presence of extremely ionized and possibly almost Compton-thick outflowing material in the innermost regions of AGNs. This also suggests that UFOs may potentially play a significant role in the expected cosmological feedback from AGNs and their study can provide important clues on the connection between accretion disks, winds, and jets.
X-ray emission from the active galactic nucleus (AGN) is believed to be produced via Comptonization of optical/ultraviolet seed photons emitted by the accretion disk, upscattered by hot electrons in ...a corona surrounding the black hole. A critical compactness versus temperature threshold is predicted above which any increase in the source luminosity, for a fixed size, would then generate positron-electron pairs rather than continue heating the coronal plasma. Current observations seem to confirm that all AGNs populate the region below this critical line. These models, however, have never been probed by observations in the high-luminosity regime, where the critical line is expected to reach low temperatures. To fill this observational gap, we selected two luminous (log(LBol) > 47.5 erg s−1) quasars, 2MASSJ1614346+470420 (z = 1.86) and B1422+231 (z = 3.62), and obtained XMM-Newton and NuSTAR deep observations for them. We performed detailed spectral analysis of their quasisimultaneous soft and hard X-ray data, in order to constrain the parameters of their coronae. Using a phenomenological cutoff power-law model, with the inclusion of a reflection component, we derived rest-frame values of the high-energy cutoff of Ecut = keV and Ecut = keV, respectively. Comptonization models consistently give as best-fit parameters electron temperatures of ∼45 keV and ∼28 keV, respectively, and optically thick coronae (τ > 1). These low coronal temperatures fall in the limited region allowed at these luminosities to avoid runaway pair production.
ABSTRACT
We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the quadruply lensed z = 1.51 quasar HS 0810+2554 which provide useful insight on the kinematics and ...morphology of the CO molecular gas and the ∼ 2 mm-continuum emission in the quasar host galaxy. Lens modelling of the mm-continuum and the spectrally integrated CO(J = 3→2) images indicates that the source of the mm-continuum has an eccentricity of e ∼ 0.9 with a size of ∼1.6 kpc and the source of line emission has an eccentricity of e ∼ 0.7 with a size of ∼1 kpc. The spatially integrated emission of the CO(J = 2→1) and CO(J = 3→2) lines shows a triple peak structure with the outer peaks separated by Δv21 = 220 ± 19 km s−1 and Δv32 = 245 ± 28 km s−1, respectively, suggesting the presence of rotating molecular CO line emitting gas. Lensing inversion of the high spatial resolution images confirms the presence of rotation of the line emitting gas. Assuming a conversion factor of αCO = 0.8 M⊙ (K km s−1 pc2)−1 we find the molecular gas mass of HS 0810+2554 to be MMol = (5.2 ± 1.5)/μ32 × 1010 M⊙, where μ32 is the magnification of the CO(J = 3→2) emission. We report the possible detection, at the 3.0–4.7σ confidence level, of shifted CO(J = 3→2) emission lines of high-velocity clumps of CO emission with velocities up to 1702 km s−1. We find that the momentum boost of the large-scale molecular wind is below the value predicted for an energy-conserving outflow given the momentum flux observed in the small-scale ultrafast outflow.
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