The nature and origin of Seyfert warm absorbers

We collate the results of recent high resolution X-ray spectroscopic observations of 23 AGN, and use the resulting information to try to provide answers to some of the main open questions about warm absorbers: where do they originate, what effect do they have on their host galaxies, and what is their importance within the energetics and dynamics of the AGN system as a whole? We find that the warm absorbers of nearby Seyferts and certain QSOs are most likely to originate in outflows from the dusty torus, and that the kinetic luminosity of these outflows accounts for well under 1% of the bolometric luminosities of the AGN. Our analysis supports, however, the view that the relativistic outflows recently observed in two PG quasars have their origin in accretion disc winds, although the energetic importance of these outflows is similar to that of the Seyfert warm absorbers. We find that the observed soft X-ray absorbing ionisation phases fill less than 10% of the available volume. Finally, we show that the amount of matter processed through an AGN outflow system, over the lifetime of the AGN, is probably large enough to have a significant influence on the evolution of the host galaxy and of the AGN itself

The nature of X-ray-absorbed quasi-stellar objects

There exists a significant population of broad line, z∼ 2 quasi-stellar objects (QSOs) which have heavily absorbed X-ray spectra. Follow-up observations in the submillimetre show that these QSOs are embedded in ultraluminous starburst galaxies, unlike most unabsorbed QSOs at the same redshifts and luminosities. Here we present X-ray spectra from XMM–Newton for a sample of five such X-ray-absorbed QSOs that have been detected at submillimetre wavelengths. We also present spectra in the rest-frame ultraviolet from ground-based telescopes. All the five QSOs are found to exhibit strong C iv absorption lines in their ultraviolet spectra with equivalent width >5 Å. The X-ray spectra are inconsistent with the hypothesis that these objects show normal QSO continua absorbed by low-ionization gas. Instead, the spectra can be modelled successfully with ionized absorbers, or with cold absorbers if they possess unusually flat X-ray continuum shapes and unusual optical to X-ray spectral energy distributions. We show that the ionized absorber model provides the simplest, most self-consistent explanation for their observed properties. We estimate that the fraction of radiated power that is converted into kinetic luminosity of the outflowing winds is typically ∼4 per cent, in agreement with recent estimates for the kinetic feedback from QSOs required to produce the M–σ relation, and consistent with the hypothesis that the X-ray-absorbed QSOs represent the transition phase between obscured accretion and the luminous QSO phase in the evolution of massive galaxies

X-ray Absorption and Reflection in Active Galactic Nuclei

X-ray spectroscopy offers an opportunity to study the complex mixture of emitting and absorbing components in the circumnuclear regions of active galactic nuclei, and to learn about the accretion process that fuels AGN and the feedback of material to their host galaxies. We describe the spectral signatures that may be studied and review the X-ray spectra and spectral variability of active galaxies, concentrating on progress from recent Chandra, XMM-Newton and Suzaku data for local type 1 AGN. We describe the evidence for absorption covering a wide range of column densities, ionization and dynamics, and discuss the growing evidence for partial-covering absorption from data at energies > 10 keV. Such absorption can also explain the observed X-ray spectral curvature and variability in AGN at lower energies and is likely an important factor in shaping the observed properties of this class of source. Consideration of self-consistent models for local AGN indicates that X-ray spectra likely comprise a combination of absorption and reflection effects from material originating within a few light days of the black hole as well as on larger scales. It is likely that AGN X-ray spectra may be strongly affected by the presence of disk-wind outflows that are expected in systems with high accretion rates, and we describe models that attempt to predict the effects of radiative transfer through such winds, and discuss the prospects for new data to test and address these ideas.Comment: Accepted for publication in the Astronomy and Astrophysics Review. 58 pages, 9 figures. V2 has fixed an error in footnote

Past, Present, and Future X-Ray and Gamma-Ray Missions

X- and -ray astronomy began in the early sixties of the last century with balloons flights, sounding rocket experiment and satellites. Long before space satellite detected X- and -rays emitted by cosmic sources, scientists had known that the Universe should be producing these photons. In this chapter we provided an overview of past and present missions that has made the X- and -ray astronomy an integral part of astronomical research, and prospects of future developments

The nature and origins of warm absorbers in Active Galactic Nuclei

This dissertation describes my analysis of XMM-Newton observations of six Active Galactic Nuclei (AGN), concentrating on the high resolution spectroscopy of soft X-ray absorption features, and discusses the results in the context of the origins and astrophysical implications of ionised outflows in AGN. I studied two Seyfert galaxies (NGC 3783 and NGC 7469) and four BL Lac objects (1H1219-1-301, H1426-I-428, Markarian 501 and PKS 0548-322), all of which have shown evidence in previous work of soft X-ray ionised absorption. NGC 3783 has very deep soft X-ray absorption. I find that there are at least two main ionisation phases. The low ionisation phase appears to be fairly well concentrated around a single ionisation parameter, whilst the high ionisation phase probably contains a range of ionisation levels. NGC 7469 has a warm absorber with a much lower overall column in our line of sight. Despite this, the detected ions from its absorber span a range of four orders of magnitude in ionisation parameter. In the BL Lac objects, neither the RGS nor the EPIC spectra show any evidence of intrinsic ionised absorption. By looking back over the history of observations of ionised X-ray absorption in these sources, I am able to show that the existence of such features can be ruled out at 93% confidence. I compare the results of these analyses with findings from high resolution X- ray spectroscopic observations of other AGN, in order to come to some conclusions about the origins and importance of the warm absorber phenomenon. I find that Seyfert, NLSyl and certain QSO absorbers are most consistent with an origin in the dusty torus, whilst the outflows in two QSOs are more likely to be accretion disc winds. I show that the kinetic luminosities of the torus outflows must account for less than 1% of the bolometric luminosities of the AGN

A long look at NGC 3783 with the XMM-NEWTON reflection grating spectrometer

A long 280 ks observation of the Seyfert 1 galaxy NGC 3783 with XMM-Newton is reported. We focus on the oxygen line complex between 17 and 24 Angstrom as measured with the Reflection Grating Spectrometer. Accurate absorption column densities and emission-line fluxes are obtained. We explore several options for the geometry and physical form of the emitting and absorbing gas. The lack of change in ionization in the absorber despite an increase in continuum flux during the observation restricts the high-ionization (O-K) and the low-ionization (Fe-M) gas to distances of at least 0.5 and 2.8 pc, respectively, away from the central source. Given the P Cygni type profiles in the resonance spectral lines and the similar velocity widths, column densities, and ionization structure inferred separately from the emission and absorption lines, it is tempting to relate the X-ray narrow-line emitting plasma with the X-ray-absorbing gas. Under this assumption, the scenario of dense clumped clouds can be ruled out. Conversely, extended ionization cones (r greater than or similar to 10 pc) are consistent with the observation independent of this assumption. These findings are in stark contrast to the picture of numerous clumpy (n(e) greater than or similar to 10(9) cm(-3)) clouds drawn recently from UV spectra, but they are consistent with the extended X-ray emission cones observed directly in Seyfert 2 galaxies

Multiwavelength campaign on Mrk 509 VI. HST/COS observations of the far-ultraviolet spectrum RID B-4804-2010

We present medium-resolution (lambda/Delta lambda similar to 20 000) ultraviolet spectra covering the 1155-1760 angstrom spectral range of the Seyfert 1 galaxy Mrk 509 obtained using the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST). Our observations were obtained simultaneously with a Low Energy Transmission Grating Spectrometer observation using the Chandra X-ray Observatory, and they are part of a multiwavelength campaign in September through December 2009 which also included observations with XMM-Newton, Swift, and INTEGRAL. Our spectra are the highest signal-to-noise observations to date of the intrinsic absorption components seen in numerous prior ultraviolet observations. To take advantage of the high S/N, we describe special calibrations for wavelength, flat-field and line-spread function corrections that we applied to the COS data. We detect additional complexity in the absorption troughs compared to prior observations made with the Space Telescope Imaging Spectrograph (STIS) on HST. We attribute the UV absorption to a variety of sources in Mrk 509, including an outflow from the active nucleus, the interstellar medium and halo of the host galaxy, and possible infalling clouds or stripped gaseous material from a merger that are illuminated by the ionizing radiation of the active nucleus. Variability between the STIS and COS observation of the most blue-shifted component (#1) allows us to set an upper limit on its distance of <250 pc. Similarly, variability of component 6 between FUSE observations limits its distance to <1.5 kpc. The absorption lines in all components only partially cover the emission from the active nucleus with covering fractions that are lower than those seen in the prior STIS observations and are comparable to those seen in spectra from the Far Ultraviolet Spectroscopic Explorer (FUSE). Given the larger apertures of COS and FUSE compared to STIS, we favor scattered light from an extended region near the active nucleus as the explanation for the partial covering. As observed in prior X-ray and UV spectra, the UV absorption has velocities comparable to the X-ray absorption, but the bulk of the ultraviolet absorption is in a lower ionization state with lower total column density than the gas responsible for the X-ray absorption. We conclude that the outflow from the active nucleus is a multiphase wind

Prompt optical observations of GRB 050319 with the Swift UVOT

The UVOT telescope on the Swift observatory has detected optical afterglow emission from GRB 050319. The flux declined with a power-law slope of alpha = -0.57 between the start of observations some 230 s after the burst onset (90 s after the burst trigger) until it faded below the sensitivity threshold of the instrument after similar to 5 x 10(4) s. There is no evidence for the rapidly declining component in the early light curve that is seen at the same time in the X-ray band. The afterglow is not detected in UVOT shortward of the B band, suggesting a redshift of about 3.5. The optical V-band emission lies on the extension of the X-ray spectrum, with an optical-to-X-ray slope of beta = 0.8. The relatively flat decay rate of the burst suggests that the central engine continues to inject energy into the fireball for as long as a few x 10(4) s after the burst