A systematic study of the ultra-fast outflow responses to luminosity variations in active galactic nuclei

© 2024 The Author(s). Published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/Context. Ultra-fast outflows (UFOs) have been revealed in a large number of active galactic nuclei (AGN) in the past two decades. Their extreme velocities and high ionization states make them a promising candidate for AGN feedback on the evolution of the host galaxy. However, their exact underlying driving mechanism is not yet fully understood. Aims. Given that the variability of UFOs may be used to distinguish among different launching mechanisms, we aim to search for and characterize the responses of the UFO properties to the variable irradiating luminosity. Methods. We perform a high-resolution time- and flux-resolved spectroscopy of archival XMM-Newton observations on six highly accreting narrow-line Seyfert 1 (NLS1) galaxies, selected by UFO detection and sufficient exposure times. The state-of-the-art methods of the blind Gaussian line scan and photoionization model scan are used to identify UFO solutions. We search for ionized winds and investigate the structure of ionized winds and their responses to the luminosity variations. The location, density, and kinetic energy of UFOs are estimated as well. Results. The powerful photoionization model scan reveals three previously unreported UFOs in RE J1034+396, PG 1244+026 and I ZW 1 with a detection significance above 3σ, and two new warm absorbers (WAs) in RE J1034+396. Five out of six (83%) AGN in our sample host multi-phase ionized winds, where outflows in I ZW 1 are energy-conserved. The relatively low-ionization entrained UFOs are discovered in four (66%) AGN of our sample, supporting the shocked outflow interpretation for ionized winds in AGN. We notice that two out of seven (28%) UFOs in our sample seem to respond to the radiation field and three (43%) UFOs hint at a radiatively accelerated nature, requiring further observations. Combined with published works, we do not find any correlations between UFO responses and AGN properties except for a tentative (∼1.8σ) anti-correlation between the UFO acceleration and the Eddington ratio, to be confirmed by further observations and an enlarged sample. The kinetic energy of UFOs, mostly detected in soft X-rays, is found to have a large uncertainty. We, therefore, cannot conclude whether soft X-ray UFOs have sufficient energy to drive the AGN feedback, although they are very promising based on some reasonable assumptions. The primary UFO in I ZW 1 (detected in the hard X-ray) is the only case in our sample to possess conclusively sufficient energy to affect the host galaxy.Peer reviewe

Accretion and outflow of gas in Markarian 509

A major uncertainty in models for photoionised outflows in AGN is the distance of the gas to the central black hole. We present the results of a massive multiwavelength monitoring campaign on the bright Seyfert 1 galaxy Mrk 509 to constrain the location of the outflow components dominating the soft X-ray band. Mrk 509 was monitored by XMM-Newton, Integral, Chandra, HST/COS and Swift in 2009. We have studied the response of the photoionised gas to the changes in the ionising flux produced by the central regions. We were able to put tight constraints on the variability of the absorbers from day to year time scales. This allowed us to develop a model for the time-dependent photoionisation in this source. We find that the more highly ionised gas producing most X-ray line opacity is at least 5 pc away from the core; upper limits to the distance of various absorbing components range between 20 pc up to a few kpc. The more lowly ionised gas producing most UV line opacity is at least 100 pc away from the nucleus. These results point to an origin of the dominant, slow (v<1000 km/s) outflow components in the NLR or torus-region of Mrk 509. We find that while the kinetic luminosity of the outflow is small, the mass carried away is likely larger than the 0.5 Solar mass per year accreting onto the black hole. We also determined the chemical composition of the outflow as well as valuable constraints on the different emission regions. We find for instance that the resolved component of the Fe-K line originates from a region 40-1000 gravitational radii from the black hole, and that the soft excess is produced by Comptonisation in a warm (0.2-1 keV), optically thick (tau~10-20) corona near the inner part of the disk.Comment: 4 pages, 1 figure, Proceedings of IAUS 290 "Feeding Compact Objects: Accretion on All Scales", C. M. Zhang, T. Belloni, M. Mendez & S. N. Zhang (eds.

The XMM-Newton wide angle survey (XWAS): the X-ray spectrum of type-1 AGN

Aims. We discuss the broad band X-ray properties of one of the largest samples of X-ray selected type-1 AGN to date (487 objects in total), drawn from the XMM-Newton Wide Angle Survey (XWAS). The objects presented in this work cover 2−10 keV (rest-frame) luminosities from ∼1042−1045 erg s−1 and are detected up to redshift ∼4. We constrain the overall properties of the broad band continuum, soft excess and X-ray absorption, along with their dependence on the X-ray luminosity and redshift.We discuss the implications for models of AGN emission. Methods. We fitted the observed 0.2−12 keV broad band spectra with various models to search for X-ray absorption and soft excess. The F-test was used with a significance threshold of 99% to statistically accept the detection of additional spectral components. Results. We constrained the mean spectral index of the broad band X-ray continuum to (Γ) = 1.96 ± 0.02 with intrinsic dispersion σ(Γ) = 0.27+0.01 −0.02. The continuum becomes harder at faint fluxes and at higher redshifts and hard (2−10 keV) luminosities. The dependence of Γ with flux is likely due to undetected absorption rather than to spectral variation. We found a strong dependence of the detection efficiency of objects on the spectral shape. We expect this effect to have an impact on the measured mean continuum shapes of sources at different redshifts and luminosities. We detected excess absorption in >∼3% of our objects, with rest-frame column densities ∼a few ×1022 cm−2. The apparent mismatch between the optical classification and X-ray properties of these objects is a challenge for the standard orientation-based AGN unification model. We found that the fraction of objects with detected soft excess is ∼36%. Using a thermal model, we constrained the soft excess mean rest-frame temperature and intrinsic dispersion to kT ∼ 100 eV and σkT ∼ 34 eV. The origin of the soft excess as thermal emission from the accretion disk or Compton scattered disk emission is ruled out on the basis of the temperatures detected and the lack of correlation of the soft excess temperature with the hard X-ray luminosity over more than 2 orders of magnitude in luminosity. Furthermore, the high luminosities of the soft excess rule out an origin in the host galaxy.We acknowledge Chris Done, Bozena Czerny, Gordon Stewart, Pilar Esquej and Ken Pounds for useful comments. We acknowledge the anonymous referee for a careful reading of the manuscript and for comments that improved the paper. S.M., M.W. and J.A.T. acknowledge support from the UK STFC research council. F.J.C. acknowledges financial support for this work from the Spanish Ministerio de Educación y Ciencia under project ESP2006-13608-C02-01. A.C. acknowledges financial support from the Spanish Ministerio de Educación y Ciencia fellowship and also from the MIUR and The Italian Space Agency (ASI) grants PRIN-MUR 2006-02-5203 and No. I/088/06/0. M.K. acknowledges support from the NASA grant NNX08AX50G and NNX07AG02G

Accretion and outflow of gas in Markarian 509

A major uncertainty in models for photoionised outflows in AGN is the distance of the gas to the central black hole. We present the results of a massive multiwavelength monitoring campaign on the bright Seyfert 1 galaxy Mrk 509 to constrain the location of the outflow components dominating the soft X-ray band. Mrk 509 was monitored by XMM-Newton, Integral, Chandra, HST/COS and Swift in 2009. We have studied the response of the photoionised gas to the changes in the ionising flux produced by the central regions. We were able to put tight constraints on the variability of the absorbers from day to year time scales. This allowed us to develop a model for the time-dependent photoionisation in this source. We find that the more highly ionised gas producing most X-ray line opacity is at least 5 pc away from the core; upper limits to the distance of various absorbing components range between 20 pc up to a few kpc. The more lowly ionised gas producing most UV line opacity is at least 100 pc away from the nucleus. These results point to an origin of the dominant, slow (v<1000 km s−1) outflow components in the NLR or torus-region of Mrk 509. We find that while the kinetic luminosity of the outflow is small, the mass carried away is likely larger than the 0.5 Solar mass per year accreting onto the black hole. We also determined the chemical composition of the outflow as well as valuable constraints on the different emission regions. We find for instance that the resolved component of the Fe-K line originates from a region 40-1000 gravitational radii from the black hole, and that the soft excess is produced by Comptonisation in a warm (0.2-1 keV), optically thick (τ~ 10-20) corona near the inner part of the dis

Average Fe Kα emission from distant AGN

[Context]: One of the most important parameters in the XRB (X-ray background) synthesis models is the average efficiency of accretion onto SMBH (super-massive black holes). This can be inferred from the shape of broad relativistic Fe lines seen in X-ray spectra of AGN (active galactic nuclei). Several studies have tried to measure the mean Fe emission properties of AGN at different depths with very different results. [Aims]: We compute the mean Fe emission from a large and representative sample of AGN X-ray spectra up to redshift ∼3.5. [Methods]: We developed a method of computing the rest-frame X-ray average spectrum and applied it to a large sample (more than 600 objects) of type 1 AGN from two complementary medium sensitivity surveys based on XMM-Newton data, the AXIS and XWAS samples. This method makes use of medium-to-low quality spectra without needing to fit complex models to the individual spectra but with computing a mean spectrum for the whole sample. Extensive quality tests were performed by comparing real to simulated data, and a significance for the detection of any feature over an underlying continuum was derived. [Results]: We detect with a 99.9% significance an unresolved Fe Kα emission line around 6.4 keV with an EW ∼ 90 eV, but we find no compelling evidence of any significant broad relativistic emission line in the final average spectrum. Deviations from a power law around the narrow line are best represented by a reflection component arising from cold or low-ionization material. We estimate an upper limit for the EW of any relativistic line of 400 eV at a 3σ confidence level. We also marginally detect the so-called Iwasawa-Taniguchi effect on the EW for the unresolved emission line, which appears weaker for higher luminosity AGN. [Conclusions]: We computed an upper limit for the average relativistic Fe Kα line contribution that is significantly lower than previously reported values from similar analyses. Our results, however, are in excellent agreement with individual analyses of local AGN samples. We attribute this difference either to our more sophisticated method of modeling the underlying continuum, to intrinsic differences in source populations, and/or to the uneven data quality of the individual spectra of the various samples.Partial financial support for this work was provided by the Spanish Ministerio de Educación y Ciencia under project ESP2006−13608. A.C. acknowledges financial support from a Spanish Ministerio de Educación y Ciencia fellowship and also from the MIUR and The Italian Space Agency (ASI) grants PRIN−MUR 2006−02−5203 and n. I/088/06/0. M.J.P., S.M., J.A.T. and M.G.W. acknowledge support from the UK STFC research council. M.C. is supported by the Deutsches Zentrumfuer Luft-und Raumfahrl (DLR) GmbH under contract No. FKZ50 OR 0404.Peer Reviewe

The physics and astrophysics of X-ray outflows from Active Galactic Nuclei

The highly energetic outflows from Active Galactic Nuclei detected in X-rays are one of the most powerful mechanisms by which the central supermassive black hole (SMBH) interacts with the host galaxy. The last two decades of high resolution X-ray spectroscopy with XMM and Chandra have improved our understanding of the nature of these outflowing ionized absorbers and we are now poised to take the next giant leap with higher spectral resolution and higher throughput observatories to understand the physics and impact of these outflows on the host galaxy gas. The future studies on X-ray outflows not only have the potential to unravel some of the currently outstanding puzzles in astronomy, such as the physical basis behind the MBH$-\sigma$ relation, the cooling flow problem in intra-cluster medium (ICM), and the evolution of the quasar luminosity function across cosmic timescales, but also provide rare insights into the dynamics and nature of matter in the immediate vicinity of the SMBH. Higher spectral resolution ($\le 0.5$ eV at $1$ keV) observations will be required to identify individual absorption lines and study the asymmetries and shifts in the line profiles revealing important information about outflow structures and their impact. Higher effective area ($\ge 1000 \rm \,cm^{2}$) will be required to study the outflows in distant quasars, particularly at the quasar peak era (redshift $1\le z\le 3$) when the AGN population was the brightest. Thus, it is imperative that we develop next generation X-ray telescopes with high spectral resolution and high throughput for unveiling the properties and impact of highly energetic X-ray outflows. A simultaneous high resolution UV + X-ray mission will encompass the crucial AGN ionizing continuum, and also characterize the simultaneous detections of UV and X-ray outflows, which map different spatial scales along the line of sight.Comment: A Science White Paper submitted to the Astro2020 Decadal Surve

Transient obscuration event captured in NGC~3227 II. Warm absorbers and obscuration events in archival XMM-Newton and NuSTAR observations

© The European Southern Observatory (ESO). This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1051/0004-6361/202141599The relationship between warm absorber (WA) outflows of active galactic nuclei and nuclear obscuration activities caused by optically thick clouds (obscurers) crossing the line of sight is still unclear. NGC 3227 is a suitable target for studying the properties of both WAs and obscurers because it matches the following selection criteria: WAs in both ultraviolet (UV) and X-rays, suitably variable, bright in UV and X-rays, and adequate archival spectra for making comparisons with the obscured spectra. In the aim of investigating WAs and obscurers of NGC 3227 in detail, we used a broadband spectral-energy-distribution model that is built in findings of the first paper in our series together with the photoionization code of SPEX software to fit the archival observational data taken by XMM-Newton and NuSTAR in 2006 and 2016. Using unobscured observations, we find four WA components with different ionization states (loga ζ [erg cm s -1] ∼-1.0, 2.0, 2.5, 3.0). The highest-ionization WA component has a much higher hydrogen column density (∼10 22 cm -2) than the other three components (∼10 21 cm -2). The outflow velocities of these WAs range from 100 to 1300 km s -1, and show a positive correlation with the ionization parameter. These WA components are estimated to be distributed from the outer region of the broad line region (BLR) to the narrow line region. It is worth noting that we find an X-ray obscuration event in the beginning of the 2006 observation, which was missed by previous studies. We find that it can be explained by a single obscurer component. We also study the previously published obscuration event captured in one observation in 2016, which needs two obscurer components to fit the spectrum. A high-ionization obscurer component (loga ζa ∼a 2.80; covering factor C f a ∼a 30%) only appears in the 2016 observation, which has a high column density (∼10 23 cm -2). A low-ionization obscurer component (loga ζa ∼a 1.0a -a 1.9; C f a ∼a 20%-50%) exists in both 2006 and 2016 observations, which has a lower column density (∼10 22 cm -2). These obscurer components are estimated to reside within the BLR by their crossing time of transverse motions. The obscurers of NGC 3227 are closer to the center and have larger number densities than the WAs, which indicate that the WAs and obscurers might have different origins.Peer reviewe

Detection of an Unidentified Soft X-ray Emission Feature in NGC 5548

NGC~5548 is an X-ray bright Seyfert 1 active galaxy. It exhibits a variety of spectroscopic features in the soft X-ray band, including in particular the absorption by the AGN outflows of a broad range of ionization states, with column densities up to 1E27 /m^2, and having speeds up to several thousand kilometers per second. The known emission features are in broad agreement with photoionized X-ray narrow and broad emission line models. We report on an X-ray spectroscopic study using 1.1 Ms XMM-Newton and 0.9 Ms Chandra grating observations of NGC 5548 spanning two decades. The aim is to search and characterize any potential spectroscopic features in addition to the known primary spectral components that are already modeled in high precision. We detect a weak unidentified excess emission feature at 18.4 Angstrom (18.1 Angstrom in the restframe). The feature is seen at >5 sigma statistical significance taking into account the look elsewhere effect. No known instrumental issues, atomic transitions, and astrophysical effects can explain this excess. The observed intensity of the possible feature seems to anti-correlate in time with the hardness ratio of the source. However, the variability might not be intrinsic, it might be caused by the time-variable obscuration by the outflows. An intriguing possibility is the line emission from charge exchange between a partially ionized outflow and a neutral layer in the same outflow, or in the close environment. Other possibilities, such as emission from a highly-ionized component with high outflowing speed, cannot be fully ruled out.Comment: 14 pages, 8 figures, accepted for publication in Astronomy & Astrophysic

Cosmic Evolution of Active Galactic Nuclei

Resumen del trabajo presentado al VIII Scientific Meeting of the Spanish Astronomical Society (Sociedad Española de Astronomía, SEA), celebrado en Santander del 7 al 11 de julio de 2008.The X-ray Luminosity Function (XLF) is a key tool to understand the evolution of Active Galactic Nuclei (AGN) and the variation in the accretion rate of matter onto the supermassive black hole that resides in their centres along cosmic time. We have studied the density of sources per unit luminosity in three energy bands combining the XMS survey with other shallower and deeper samples, up to redshifts of ∼ 3. The XMS survey covers a sky area of ∼ 3. 3 square degrees at medium fluxes, where the bulk of the Cosmic X-ray Background is emitted. Moreover, extragalactic surveys such as XMS are essential since they contain a large amount of obscured AGN that decisively contribute to the background emission. We have found evolution in the AGN detected in soft (0.5–2 keV), hard (2–10 keV) and ultrahard (4.5–7.5 keV) X-rays, finding a maximum in the comoving density of these objects at redshifts of ∼ 1. Since we have detailed spectral information of most of the AGN detected at > 2 keV, we have studied their XLF along with their intrinsic absorption properties in order to obtain purely observational results and to determine the evolution of absorbed AGN at different epochs of the Universe.Peer Reviewe

Exploring structure around submm-bright QSO

23 diapositivas.-- Trabajo presentado al Meeting "The Infrared/X-ray Connection in Galaxy Evolution" session 6: AGN feedback; celebrado en MSSL, UK, 2010.We have assembled a sample of X-ray and submm luminous QSOs which are therefore both growing their central black holes through accretion and forming stars copiously (Stevens+05). They are also surrounded by submm source overdensities (Stevens+10), placing them in the centres of high density peaks of the z~2 Universe, probably giving rise to massive ellipticals like those seen in the local Universe. We explore in detail here the field around one of those QSO: RX J0941 (z=1.82). Radio observations confirm the submm source detections and pinpoint the optical/NIR/MIR counterparts. We have used photometric redshifts and SED matching, showing that at least 4 of the 5 submm sources are associated to the QSO, with very little room for AGN contribution. These are mature galaxies with BH-to-stellar mass ratios about one dex below local values: most of their central BH mass is still to be accreted, which can happen in a few tens of My. The total mass is similar to that of a present-day cD galaxy and local stellar-to-BH masses can be reached if L3% of the available gas mass is accreted.Peer reviewe