arXiv subjects

Jelle Kaastra

Publications and source records attributed to Jelle Kaastra.

At least 73 records · Page 4Linked to original sources

arXiv2014

The ASTRO-H X-ray Astronomy Satellite

The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions developed by the Institute of Space and Astronautical Science (ISAS), with a planned launch in 2015. The ASTRO-H mission is equipped with a suite of sensitive instruments with the highest energy resolution ever achieved at E > 3 keV and a wide energy range spanning four decades in energy from soft X-rays to gamma-rays. The simultaneous broad band pass, coupled with the high spectral resolution of Delta E < 7 eV of the micro-calorimeter, will enable a wide variety of important science themes to be pursued. ASTRO-H is expected to provide breakthrough results in scientific areas as diverse as the large-scale structure of the Universe and its evolution, the behavior of matter in the gravitational strong field regime, the physical conditions in sites of cosmic-ray acceleration, and the distribution of dark matter in galaxy clusters at different redshifts.

astro-ph.IM↗

arXiv2013

The Hot and Energetic Universe: The missing baryons and the warm-hot intergalactic medium

The backbone of the large-scale structure of the Universe is determined by processes on a cosmological scale and by the gravitational interaction of the dominant dark matter. However, the mobile baryon population shapes the appearance of these structures. Theory predicts that most of the baryons reside in vast unvirialized filamentary structures that connect galaxy groups and clusters, but the observational evidence is currently lacking. Because the majority of the baryons are supposed to exist in a large-scale, hot and dilute gaseous phase, X-rays provide the ideal tool to progress our understanding. Observations with the Athena+ X-ray Integral Field Unit will reveal the location, chemical composition, physical state and dynamics of the active population of baryons.

astro-ph.HE↗

arXiv2012

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.

astro-ph.CO↗

arXiv2012

The ASTRO-H X-ray Observatory

The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the high-energy universe via a suite of four instruments, covering a very wide energy range, from 0.3 keV to 600 keV. These instruments include a high-resolution, high-throughput spectrometer sensitive over 0.3-2 keV with high spectral resolution of Delta E < 7 eV, enabled by a micro-calorimeter array located in the focal plane of thin-foil X-ray optics; hard X-ray imaging spectrometers covering 5-80 keV, located in the focal plane of multilayer-coated, focusing hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4-12 keV, with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and a non-focusing Compton-camera type soft gamma-ray detector, sensitive in the 40-600 keV band. The simultaneous broad bandpass, coupled with high spectral resolution, will enable the pursuit of a wide variety of important science themes.

astro-ph.IM↗

arXiv2011

Galactic Scale Absorption Outflow in the Low Luminosity Quasar IRAS~F04250-5718: HST/COS Observations

We present absorption line analysis of the outflow in the quasar IRAS F04250-5718. Far-ultraviolet data from the Cosmic Origins Spectrograph onboard the Hubble Space Telescope reveal intrinsic narrow absorption lines from high ionization ions (e.g., C IV, N V, and O VI) as well as low ionization ions (e.g., C II and Si III). We identify three kinematic components with central velocities ranging from ~-50 to ~-230 km/s. Velocity dependent, non-black saturation is evident from the line profiles of the high ionization ions. From the non-detection of absorption from a metastable level of C II, we are able to determine that the electron number density in the main component of the outflow is < 30 per cubic cm. Photoionization analysis yields an ionization parameter log U ~ -1.6 +/- 0.2, which accounts for changes in the metallicity of the outflow and the shape of the incident spectrum. We also consider solutions with two ionization parameters. If the ionization structure of the outflow is due to photoionization by the active galactic nucleus, we determine that the distance to this component from the central source is > 3 kpc. Due to the large distance determined for the main kinematic component, we discuss the possibility that this outflow is part of a galactic wind.

astro-ph.CO↗

arXiv2011

Studying the Warm-Hot Intergalactic Medium in Emission

We assess the possibility to detect the warm-hot intergalactic medium (WHIM) in emission and to characterize its physical conditions and spatial distribution through spatially resolved X-ray spectroscopy, in the framework of the recently proposed DIOS, EDGE, Xenia, and ORIGIN missions, all of which are equipped with microcalorimeter-based detectors. For this purpose we analyze a large set of mock emission spectra, extracted from a cosmological hydrodynamical simulation. These mock X-ray spectra are searched for emission features showing both the OVII K alpha triplet and OVIII Ly alpha line, which constitute a typical signature of the warm hot gas. Our analysis shows that 1 Ms long exposures and energy resolution of 2.5 eV will allow us to detect about 400 such features per deg^2 with a significance >5 sigma and reveals that these emission systems are typically associated with density ~100 above the mean. The temperature can be estimated from the line ratio with a precision of ~20%. The combined effect of contamination from other lines, variation in the level of the continuum, and degradation of the energy resolution reduces these estimates. Yet, with an energy resolution of 7 eV and all these effects taken into account, one still expects about 160 detections per deg^2. These line systems are sufficient to trace the spatial distribution of the line-emitting gas, which constitute an additional information, independent from line statistics, to constrain the poorly known cosmic chemical enrichment history and the stellar feedback processes.

astro-ph.CO↗

arXiv2010

The ASTRO-H Mission

The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the high-energy universe by performing high-resolution, high-throughput spectroscopy with moderate angular resolution. ASTRO-H covers very wide energy range from 0.3 keV to 600 keV. ASTRO-H allows a combination of wide band X-ray spectroscopy (5-80 keV) provided by multilayer coating, focusing hard X-ray mirrors and hard X-ray imaging detectors, and high energy-resolution soft X-ray spectroscopy (0.3-12 keV) provided by thin-foil X-ray optics and a micro-calorimeter array. The mission will also carry an X-ray CCD camera as a focal plane detector for a soft X-ray telescope (0.4-12 keV) and a non-focusing soft gamma-ray detector (40-600 keV) . The micro-calorimeter system is developed by an international collaboration led by ISAS/JAXA and NASA. The simultaneous broad bandpass, coupled with high spectral resolution of Delta E ~7 eV provided by the micro-calorimeter will enable a wide variety of important science themes to be pursued.

astro-ph.IM↗

arXiv2006

Comments on the manuscript: ``The weak absorbing outflow in AGN Mrk 279: evidence of super-solar metal abundances'' astro-ph/0611578 by Fields et al

A recent manuscript posted on astro-ph (astro-ph/0611578) by Fields et al. (hereafter F06) reports evidence of supersolar metal abundances in Mrk 279 by analyzing its Chandra LETGS X-ray spectrum. We point out that it is impossible in principle to obtain direct metal abundances from these X-ray data, since there is no handle on the amount of hydrogen column density. If F06 would have lowered their C, N, O and Fe abundance by a factor of ten and increased the hydrogen column density by a factor of ten, they would have obtained an almost identical fit with subsolar metalicity. F06 find support for their supersolar metal abundances from a cursory analysis of the UV data from the same Mrk 279 campaign. We point out that F06 included in that analysis portions of the UV trough that are known to arise from gas unrelated to the outflow, which weakens the support from the UV data. A detailed analysis of the Chandra LETGS X-ray spectrum was accepted for publication in A&A on Sept 14 2006 (Costantini et al 2006; hereafter C06) and posted on astro-ph on the same date. F06 ignore most of this published analysis while duplicating the finding of two ionization components with similar parameters to the ones found by C06. Finally, we note that it is possible to derive accurate abundances from the UV data set of this object. We already published these findings in a conference precedings and have submitted the relevant manuscript to ApJ. We find that relative to solar the abundances in the Mrk 279 outflow are (linear scaling): carbon 2.2 +/- 0.7, nitrogen 3.5 +/- 1.1 and oxygen 1.6 +/- 0.8.

astro-ph↗

arXiv2006

On the Putative Detection of z>0 X-ray Absorption Features in the Spectrum of Markarian 421

In a series of papers, Nicastro et al. have reported the detection of z>0 OVII absorption features in the spectrum of Mrk421 obtained with the Chandra Low Energy Transmission Grating Spectrometer (LETGS). We evaluate this result in the context of a high quality spectrum of the same source obtained with the Reflection Grating Spectrometer (RGS) on XMM-Newton. The data comprise over 955ks of usable exposure time and more than 26000 counts per 50 milliAngstrom at 21.6 Angstroms. We concentrate on the spectrally clean region (21.3 < lambda < 22.5 Angstroms) where sharp features due to the astrophysically abundant OVII may reveal an intervening, warm--hot intergalactic medium (WHIM). We do not confirm detection of any of the intervening systems claimed to date. Rather, we detect only three unsurprising, astrophysically expected features down to the Log(N_i)~14.6 (3 sigma) sensitivity level. Each of the two purported WHIM features is rejected with a statistical confidence that exceeds that reported for its initial detection. While we can not rule out the existence of fainter, WHIM related features in these spectra, we suggest that previous discovery claims were premature. A more recent paper by Williams et al. claims to have demonstrated that the RGS data we analyze here do not have the resolution or statistical quality required to confirm or deny the LETGS detections. We show that our careful analysis resolves the issues encountered by Williams et al. and recovers the full resolution and statistical quality of the RGS data. We highlight the differences between our analysis and those published by Williams et al. as this may explain our disparate conclusions.

astro-ph↗

arXiv2006

Effervescent heating: constraints from nearby cooling flow clusters observed with XMM-Newton

We have used deprojected radial density and temperature profiles of a sample of 16 nearby CF clusters observed with XMM-Newton to test whether the effervescent heating model can satisfactorily explain the dynamics of CF clusters. For each cluster we derived the required extra heating as a function of cluster-centric distance for various values of the unknown parameters $\dot M$ (mass deposition rate) and $f_c$ (conduction efficiency). We fitted the extra heating curve using the AGN effervescent heating function and derived the AGN parameters $L$ (the time-averaged luminosity) and $r_0$ (the scale radius where the bubbles start rising in the ICM). While we do not find any solution with the effervescent heating model for only one object, we do show that AGN and conduction heating are not cooperating effectively for half of the objects in our sample. For most of the clusters we find that, when a comparison is possible, the derived AGN scale radius $r_0$ and the observed AGN jet extension have the same order of magnitude. The AGN luminosities required to balance radiative losses are substantially lowered if the fact that the AGN deposits energy within a finite volume is taken into account. For the Virgo cluster, we find that the AGN power derived from the effervescent heating model is in good agreement with the observed jet power.

astro-ph↗

arXiv2005

ROSAT observations of the soft X-ray background and of the cluster soft excess emission in the Hercules supercluster

Recent observations with the XMM-Newton satellite confirmed the existence of the soft excess phenomenon in galaxy clusters, earlier discovered in several EUVE, ROSAT and BeppoSAX observations. Among the clusters for which XMM has reported detection of soft excess emission are MKW03s and A2052, two clusters in the Hercules concentration. The Hercules supercluster lies along the southern extension of the North Polar Spur, a region of bright soft X-ray emission clearly visible in ROSAT All-Sky Survey images. We analyze 11 pointed ROSAT PSPC observations toward 3 clusters in the Hercule concentration, MKW03s, A2052 and A2063, and 8 neighboring fields in order to investigate the soft X-ray emission in that region of the sky. We find that the soft X-ray emission varies by a factor of few on scales of few degrees, rendering the background subtraction a complex task. If the Noth Polar Spur emission is of local origin, we find that only A2052 and A2063 have evidence of cluster soft excess emission, and that the OVII emission lines detected in XMM observations of A2052 and MKW03s are not associated with the cluster. If part or all of the North Polar Spur soft X-ray enhancement is of extragalactic nature, the three clusters feature strong soft excess emission, and the OVII emission lines observed by XMM are genuinely associated with the clusters. We interpret the soft excess emission with the presence of warm gas, either intermixed with the hot intra-cluster medium or in filamentary structures located around the clusters, and estimate that the warm gas is approximately as massive as the hot intra-cluster medium.

astro-ph↗

arXiv2004

Temperature and entropy profiles of nearby cooling flow clusters observed with XMM-Newton

We investigate temperature and entropy profiles of 13 nearby cooling flow clusters observed with the EPIC cameras of XMM-Newton. When normalized and scaled by the virial radius the temperature profiles turn out to be remarkably similar. At large radii the temperature profiles show a clear decline starting from a break radius at ~ 0.1 r_vir. The temperature decreases by ~30 % between 0.1 r_vir and 0.5 r_vir. As expected for systems where non-gravitational processes are of great importance, the scale length characterizing the central temperature drop is not found to be proportional to the virial radius of the system. The entropy of the plasma increases monotonically moving outwards almost proportional to the radius and the central entropy level is tightly correlated with the core radius of the X-ray emission. The dispersion in the entropy profiles is smaller if the empirical relation S \propto T^{0.65} is used instead of the standard self-similar relation S \propto T and, as expected for cooling flow clusters, no entropy cores are observed.

astro-ph↗

arXiv2004

X-ray/UV Campaign on the Mrk 279 AGN Outflow: Constraining Inhomogeneous Absorber Models

We investigate the applicability of inhomogeneous absorber models in the formation of AGN outflow absorption-troughs. The models we explore are limited to monotonic gradients of absorbing column densities in front of a finite emission source. Our main finding is that simple power-law and gaussian distributions are hard pressed to fit the Mrk 279 high-quality UV outflow data. An acceptable fit for the O VI troughs can only be obtained by assuming unrealistic optical depth values (upward of 100). The strongest constraints arise from the attempt to fit the Lyman series troughs. In this case it is evident that even allowing for complete freedom of both the power-law exponent and the optical depth as a function of velocity cannot yield an acceptable fit. In contrast, partial covering models do yield good fits for the Lyman series troughs. We conclude that monotonic inhomogeneous absorber models that do not include a sharp edge in the optical depth distribution across the source are not an adequate physical model to explain the trough formation mechanism for the outflow observed in Mrk 279.

astro-ph↗

arXiv2004

High Resolution X-ray Spectroscopy of G292.0+1.8/MSH 11-54

We present a preliminary analysis of XMM-Newton observations of the oxygen-rich supernova remnant G292.0+1.8 (MSH 11-54). Although the spatial extent of the remnant is 8 arcmin the bright central bar is narrow (1'-2') resulting in RGS spectra of a high spectral quality. This allows us to spectroscopically identify a cool, Te = 0.3 keV, and underionized component, resolve details of the Fe-L complex, and resolve the forbidden and resonant lines of the O VII triplet. We are also able to constrain the kinematics of the remnant using Ne IX as observed in the second order spectrum, and O VIII in the first order spectrum. We do not find evidence for O VII line shifts or Doppler broadening (sigma_v < 731 km/s), but line broadening of the Ne X Ly-alpha line seems to be present, corresponding to sigma_v ~ 1500 km/s.

astro-ph↗

arXiv2003

Contrasting the UV and X-ray O VI Column Density Inferred for the Outflow in NGC 5548

We compare X-ray and UV spectroscopic observations of NGC 5548. Both data sets show O VI absorption troughs associated with the AGN outflow from this galaxy. We find that the robust lower limit on the column density of the O VI X-ray trough is seven times larger than the column density found in a study of the O VI UV troughs. This discrepancy suggests that column densities inferred for UV troughs of Seyfert outflows are often severely underestimated. We identify the physical limitations of the UV Gaussian modeling as the probable explanation of the O VI column density discrepancy. Specifically, Gaussian modeling cannot account for a velocity dependent covering fraction, and it is a poor representation for absorption associated with a dynamical outflow. Analysis techniques that use a single covering fraction value for each absorption component suffer from similar limitations. We conclude by suggesting ways to improve the UV analysis.

astro-ph↗

arXiv2002

The complex X-ray spectrum of the supersoft source MR Vel

We present the X-ray spectrum of MR Vel/RXJ0925.7-4758 obtained with the Medium Energy Grating spectrometer of the Chandra X-ray Telescope. The simplest models used by earlier authors, stellar atmospheres in combination with a thermal plasma in collisional ionization equilibrium, cannot explain the spectrum. Neither does a photo-ionized plasma. We identify P Cygni profiles of Fe XVII and O VIII, from which we conclude that these lines arise in a wind. We conclude that major uncertainty exists about the bolometric luminosity of MR Vel, and perhaps of supersoft sources in general, so that the theoretical prediction that this luminosity derives from steady nuclear burning cannot be verified.

astro-ph↗

arXiv2002

A synoptic spectral study of Cassiopeia-A based on XMM-Newton and BeppoSax observations

In this paper we present recent image and spectral data of Cas-A obtained with XMM-Newton and BeppoSAX. Analysis of the hard X-ray continuum does not support an interpretation of the hard X-radiation as synchrotron emission produced in the primary shock, non-thermal Bremsstrahlung is a plausible alternative. Moreover, a recent 500 kilosecond deep observation of the hard X-ray continuum by BeppoSAX has revealed the positive detection of the 44Sc nuclear decay lines at 67.9 and 78.4 keV. Appropriate modelling of the hard X-ray continuum leads to an estimate of the initial 44Ti mass of (0.8-2.5)E-4 solar masses. We also present ionisation age, temperature, abundances maps. The observed elemental abundance ratio patterns can be reconciled best with a type Ib SNe, arising from a 60 solar mass progenitor (ZAMS) with high-mass-loss. The accurate modeling of the image-resolved emission line spectra has enabled us to derive reliable Doppler velocities for the bright Si-K, S-K, and Fe-K line complexes.

astro-ph↗

arXiv2002

Non-thermal bremsstrahlung as the dominant hard X-ray continuum emission from the supernova remnant MSH14-63 (RCW 86)

We present an analysis of the X-ray emission of the supernova remnant MSH14-63, which was partially covered by four observations with XMM-Newton. The detection of Fe K emission at 6.4 keV, and the lack of spatial correlation between hard X-ray and radio emission is evidence against a dominant X-ray synchrotron component. We argue that the hard X-ray continuum is best explained by non-thermal bremsstrahlung from a supra-thermal tail to an otherwise cool electron gas. The existence of low electron temperatures, required to explain the absence of line emission, is supported by low temperatures found in other parts of the remnant, which are as low as 0.2 keV in some regions.

astro-ph↗