Search

Measurements of long-lived radioisotopes provide a means, completely independent of other observational channels, to draw conclusions about near-Earth supernovae (SNe) and thus the origin of the Local Bubble (LB). First and foremost in this context is 60Fe, which has already been detected across the Earth and on the Moon. Using Gaia EDR3, we identified 14 SN explosions, with 13 occurring in UCL/LCC, and one in V1062 Sco, all being subgroups of the Sco-Cen OB association. The timing of these explosions was obtained by us through interpolation of rotating stellar evolution tracks via the initial masses of the already exploded massive stars. We further developed a new Monte Carlo-type approach for deriving the trajectories of the SN progenitors. We then performed 3D hydrodynamic simulations based on these initial conditions to explore the evolution of the LB in an inhomogeneous local interstellar medium and the transport of radioisotopes to Earth. The simulations include the stellar winds from the SN progenitors and additional radioisotopes (26Al, 53Mn, and 244Pu) besides 60Fe. We find that (i) our simulations are consistent with measurements of 60Fe, in particular, a peak 2-3 Myr before present, as well as 26Al, 53Mn, and 244Pu data, (ii) stellar winds contribute to the distribution of radioisotopes and also to the dynamics of the LB, (iii) the solar system (SS) entered the LB about 4.6 Myr ago, and (iv) the measured recent influx of 60Fe can be naturally explained by turbulent radioisotopic transport. Our simulations not only support the recent hypothesis that the LB triggered star formation in the solar vicinity through its expansion, but also suggest that the second, separate 60Fe peak measured at 6-9 Myr ago was generated by the passage of the SS through a neighboring superbubble (SB), possibly the Orion-Eridanus SB, prior to its current residence in the LB., Comment: 30 pages, 13 figures, accepted for publication in A&A

The Rayleigh-Taylor (RT) instability is omnipresent in the physics of inversely density-stratified fluids subject to effective gravitational acceleration. In astrophysics, a steep stratification of the ambient medium can fragment a bubble shell faster due to a strongly time-dependent RT instability, causing the classical constant gravity models to fail. We derive the time-dependent instability criteria analytically for the cases of constant, exponential, and power-law accelerations, verifying them through high-resolution numerical simulations. Our results show that (1) even in the linear phase there is a term opposing exponential growth, (2) non-linear growth approaches asymptotically the solution found by Fermi and von Neumann, (3) the interpenetrating spikes and bubbles promote a significant mixing, with the fractal dimension of the interface approaching 1.6, only limited by numerical diffusion, and (4) the probability density function (PDF) for the passive scalar to study mixing becomes increasingly sharper peaked for power-law and exponential acceleration. Applying our solutions to stellar wind bubbles, young supernova remnants (SNRs), and superbubbles (SBs), we find that the growth rate of the RT instability is generally higher in the shells of wind-blown bubbles in a power-law stratified medium than in those with power-law rising stellar mechanical luminosities, Tycho-like than Cas A-like SNRs, and one-sided than symmetric SBs. The recently observed eROSITA bubbles indicate smooth rim surfaces, implying that the outer shell has not been affected by RT instabilities. Therefore the dynamical evolution of the bubbles suggests maximum final ages that are significantly above their current age, which we estimate to be about 20 Myr., Comment: 22 pages, 18 figures, accepted for publication in MNRAS

Aims: We use new deep XMM-Newton observations of the northern disk of M 31 to trace the hot interstellar medium (ISM) in unprecedented detail and to characterise the physical properties of the X-ray emitting plasmas. Methods: We used all XMM-Newton data up to and including our new observations to produce the most detailed image yet of the hot ISM plasma in a grand design spiral galaxy such as our own. We compared the X-ray morphology to multi-wavelength studies in the literature to set it in the context of the multi-phase ISM. We performed spectral analyses on the extended emission using our new observations as they offer sufficient depth and count statistics to constrain the plasma properties. Data from the Panchromatic Hubble Andromeda Treasury were used to estimate the energy injected by massive stars and their supernovae. We compared these results to the hot gas properties. Results: The brightest emission regions were found to be correlated with populations of massive stars, notably in the 10 kpc star-forming ring. The plasma temperatures in the ring regions are ~0.2 keV up to ~0.6 keV. We suggest this emission is hot ISM heated in massive stellar clusters and superbubbles. We derived X-ray luminosities, densities, and pressures for the gas in each region. We also found large extended emission filling low density gaps in the dust morphology of the northern disk, notably between the 5 kpc and 10 kpc star-forming rings. We propose that the hot gas was heated and expelled into the gaps by the populations of massive stars in the rings. Conclusions. It is clear that the massive stellar populations are responsible for heating the ISM to X-ray emitting temperatures, filling their surroundings, and possibly driving the hot gas into the low density regions. Overall, the morphology and spectra of the hot gas in the northern disk of M 31 is similar to other galaxy disks., Comment: 23 pages, 14 figures, accepted for publication in Astronomy & Astrophysics

Aims. Determination of K- and L-shell cross sections of the carbon atom and ions using the modified relativistic binary encounter Bethe (MRBEB) method, a simple analytical scheme based on one atomic parameter that allows determining electron-impact ionization cross sections. The quality of the cross sections calculated with the MRBEB method is shown through: (i) comparison with those obtained with the general ionization processes in the presence of electrons and radiation (GIPPER) code and the flexible atomic code (FAC), and (ii) determination of their effects on the ionic structure and cooling of an optically thin plasma. Results. The three sets of cross sections show deviations among each other in different energy regions. The largest deviations occur near and in the peak maximum. Ion fractions and plasma emissivities of an optically thin plasma that evolves under collisional ionization equilibrium, derived using each set of cross sections, show deviations that decrease with increase in temperature and ionization degree. In spite of these differences, the calculations using the three sets of cross sections agree overall. Conclusions. A simple model like the MRBEB is capable of providing cross sections similar to those calculated with more sophisticated quantum mechanical methods in the GIPPER and FAC codes., Comment: 10 pages, 4 figures, accepted for publication in Astronomy & Astrophysics, section 12. Atomic, molecular, and nuclear data of Astronomy and Astrophysics

There is now solid experimental evidence of at least one supernova explosion within 100 pc of Earth within the last few million years, from measurements of the short-lived isotope 60Fe in widespread deep-ocean samples, as well as in the lunar regolith and cosmic rays. This is the first established example of a specific dated astrophysical event outside the Solar System having a measurable impact on the Earth, offering new probes of stellar evolution, nuclear astrophysics, the astrophysics of the solar neighborhood, cosmic-ray sources and acceleration, multi-messenger astronomy, and astrobiology. Interdisciplinary connections reach broadly to include heliophysics, geology, and evolutionary biology. Objectives for the future include pinning down the nature and location of the established near-Earth supernova explosions, seeking evidence for others, and searching for other short-lived isotopes such as 26Al and 244Pu. The unique information provided by geological and lunar detections of radioactive 60Fe to assess nearby supernova explosions make now a compelling time for the astronomy community to advocate for supporting multi-disciplinary, cross-cutting research programs., Comment: 11 pages, 2 figures. Astro2020 Science White Paper submitted to the 2020 Decadal Survey on Astronomy and Astrophysics

{\bf Context.} Numerical models of the evolution of interstellar and integalactic plasmas often assume that the adiabatic parameter $\gamma$ (the ratio of the specific heats) is constant (5/3 in monoatomic plasmas). However, $\gamma$ is determined by the total internal energy of the plasma, which depends on the ionic and excitation state of the plasma. Hence, the adiabatic parameter may not be constant across the range of temperatures available in the interstellar medium. {\bf Aims.} We aim to carry out detailed simulations of the thermal evolution of plasmas with Maxwell-Boltzmann and non-thermal ($\kappa$ and $n$) electron distributions in order to determine the temperature variability of the total internal energy and of the adiabatic parameter. {\bf Methods.} The plasma, composed of H, He, C, N, O, Ne, Mg, Si, S, and Fe atoms and ions, evolves under collisional ionization equilibrium conditions, from an initial temperature of $10^9$ K. The calculations include electron impact ionization, radiative and dielectronic recombinations and line excitation. The ionization structure was calculated (...) using the Gauss elimination method with scaled partial pivoting. Numerical integrations (...) were carried out using the double-exponential over a semi-finite interval method. In both methods a precision of $10^{-15}$ is adopted. {\bf Results.} The total internal energy of the plasma is mainly dominated by the ionization energy for temperatures lower than $8\times 10^4$ K with the excitation energy having a contribution of less than one percent. In thermal and non-thermal plasmas composed of H, He, and metals, the adiabatic parameter evolution is determined by the H and He ionizations leading to a profile in general having three transitions. However, for $\kappa$ distributed plasmas these three transitions are not observed for $\kappa<15$ (...). In general, $\gamma$ varies from 1.01 to 5/3., Comment: Accepted for publication in Astronomy & Astrophysics; Section: Numerical methods and codes; 9 pages, 6 figures, 2 tables available in CDS

Deep-sea archives all over the world show an enhanced concentration of the radionuclide $^{60}$Fe, isolated in layers dating from about 2.2 Myr ago. Since this comparatively long-lived isotope is not naturally produced on Earth, such an enhancement can only be attributed to extraterrestrial sources, particularly one or several nearby supernovae in the recent past. It has been speculated that these supernovae might have been involved in the formation of the Local Superbubble, our Galactic habitat. Here, we summarize our efforts in giving a quantitative evidence for this scenario. Besides analytical calculations, we present results from high-resolution hydrodynamical simulations of the Local Superbubble and its presumptive neighbor Loop I in different environments, including a self-consistently evolved supernova-driven interstellar medium. For the superbubble modeling, the time sequence and locations of the generating core-collapse supernova explosions are taken into account, which are derived from the mass spectrum of the perished members of certain, carefully preselected stellar moving groups. The release and turbulent mixing of $^{60}$Fe is followed via passive scalars, where the yields of the decaying radioisotope were adjusted according to recent stellar evolution calculations. The models are able to reproduce both the timing and the intensity of the $^{60}$Fe excess observed with rather high precision. We close with a discussion of recent developments and give future perspectives., Comment: 10 pages, 3 figures, published in the special issue of Galaxies: "Searching for Connections among the Fermi Bubbles, the Galactic Center GeV Excess, and Loop I"

Tracking the thermal evolution of plasmas, characterized by an n-distribution, using numerical simulations, requires the determination of the emission spectra and of the radiative losses due to free-free emission from the correspond- ing temperature averaged and total Gaunt factors. Detailed calculations of the latter are presented, associated to n-distributed electrons with the parameter n ranging from 1 (corresponding to the Maxwell-Boltzmann distribu- tion) to 100. The temperature averaged and total Gaunt factors, with decreasing n tend to those obtained with the Maxwell-Boltzmann distribution. Radiative losses due to free-free emission in a plasma evolving under collisional ionization equilibrium conditions and composed by H, He, C, N, O, Ne, Mg, Si, S, and Fe ions, are presented. These losses decrease with the decrease in the parameter n reaching a minimum when n = 1, and, thus converging to the losses of a thermal plasma. Tables of the thermal averaged and total Gaunt factors calculated for n distributions and a wide range electron and photon energies are presented., Comment: Accepted for publication in ApJS. 70 pages, 7 figures and 11 tables

The discovery of radionuclides like 60Fe with half-lives of million years in deep-sea crusts and sediments offers the unique possibility to date and locate nearby supernovae. We want to quantitatively establish that the 60Fe enhancement is the result of several supernovae which are also responsible for the formation of the Local Bubble, our Galactic habitat. We performed three-dimensional hydrodynamic adaptive mesh refinement simulations (with resolutions down to subparsec scale) of the Local Bubble and the neighbouring Loop I superbubble in different homogeneous, self-gravitating environments. For setting up the Local and Loop I superbubble, we took into account the time sequence and locations of the generating core-collapse supernova explosions, which were derived from the mass spectrum of the perished members of certain stellar moving groups. The release of 60Fe and its subsequent turbulent mixing process inside the superbubble cavities was followed via passive scalars, where the yields of the decaying radioisotope were adjusted according to recent stellar evolution calculations. The models are able to reproduce both the timing and the intensity of the 60Fe excess observed with rather high precision, provided that the external density does not exceed 0.3 cm-3 on average. Thus the two best-fit models presented here were obtained with background media mimicking the classical warm ionised and warm neutral medium. We also found that 60Fe (which is condensed onto dust grains) can be delivered to Earth via two physical mechanisms: either through individual fast-paced supernova blast waves, which cross the Earth's orbit sometimes even twice as a result of reflection from the Local Bubble's outer shell, or, alternatively, through the supershell of the Local Bubble itself, injecting the 60Fe content of all previous supernovae at once, but over a longer time range., Comment: 14 pages, 7 figures, accepted for publication in A&A

Traces of 2-3 Myr old 60Fe were recently discovered in a manganese crust and in lunar samples. We have found that this signal is extended in time and is present in globally distributed deep-sea archives. A second 6.5-8.7 Myr old signature was revealed in a manganese crust. The existence of the Local Bubble hints to a recent nearby supernova-activity starting 13 Myr ago. With analytical and numerical models generating the Local Bubble, we explain the younger 60Fe-signature and thus link the evolution of the solar neighborhood to terrestrial anomalies., Comment: 4 pages, 3 figures, accepted for publication in JPS Conf. Proc

Using detailed 3D hydrodynamic simulations we study the nature of the Galactic supernova remnant (SNR) CTB 109 (G109.1-1.0), which is well-known for its semicircular shape and a bright diffuse X-ray emission feature inside the SNR. Our model has been designed to explain the observed morphology, with a special emphasis on the bright emission feature inside the SNR. Moreover, we determine the age of the remnant and compare our findings with X-ray observations. With CTB 109 we test a new method of detailed numerical simulations of diffuse young objects, using realistic initial conditions derived directly from observations. We performed numerical 3D simulations with the RAMSES code. The initial density structure has been directly taken from $^{12}$CO emission data, adding an additional dense cloud, which, when it is shocked, causes the bright emission feature. From parameter studies we obtained the position $(\ell , b)=(109.1545^\circ , -1.0078^\circ)$ for an elliptical cloud with $n_\text{cloud}=25~\text{cm}^{-3}$ based on the preshock density from Chandra data and a maximum diameter of 4.54 pc, whose encounter with the supernova (SN) shock wave generates the bright X-ray emission inside the SNR. The calculated age of the remnant is about 11,000 yr according to our simulations. In addition, we can also determine the most probable site of the SN explosion. Hydrodynamic simulations can reproduce the morphology and the observed size of the SNR CTB 109 remarkably well. Moreover, the simulations show that it is very plausible that the bright X-ray emission inside the SNR is the result of an elliptical dense cloud shocked by the SN explosion wave. We show that numerical simulations using observational data for an initial model can produce meaningful results., Comment: 9 pages, 6 figures, accepted for publication in A&A

Aims. Optically thin plasmas may deviate from thermal equilibrium and thus, electrons (and ions) are no longer described by the Maxwellian distribution. Instead they can be described by $\kappa$-distributions. The free-free spectrum and radiative losses depend on the temperature-averaged (over the electrons distribution) and total Gaunt factors, respectively. Thus, there is a need to calculate and make available these factors to be used by any software that deals with plasma emission. Methods. We recalculated the free-free Gaunt factor for a wide range of energies and frequencies using hypergeometric functions of complex arguments and the Clenshaw recurrence formula technique combined with approximations whenever the difference between the initial and final electron energies is smaller than $10^{-10}$ in units of $z^2Ry$. We used double and quadruple precisions. The temperature- averaged and total Gaunt factors calculations make use of the Gauss-Laguerre integration with 128 nodes. Results. The temperature-averaged and total Gaunt factors depend on the $\kappa$ parameter, which shows increasing deviations (with respect to the results obtained with the use of the Maxwellian distribution) with decreasing $\kappa$. Tables of these Gaunt factors are provided., Comment: Paper accepted for publication in Astronomy & Astrophysics. Contains 5 pages, 4 figures, and 9 tables

Galactic winds are a common phenomenon in starburst galaxies in the local universe as well as at higher redshifts. Their sources are superbubbles driven by sequential supernova explosions in star forming regions, which carve out large holes in the interstellar medium and eject hot, metal enriched gas into the halo and to the galactic neighborhood. We investigate the evolution of superbubbles in exponentially stratified disks. We present advanced analytical models for the expansion of such bubbles and calculate their evolution in space and time. With these models one can derive the energy input that is needed for blow-out of superbubbles into the halo and derive the break-up of the shell, since Rayleigh-Taylor instabilities develop soon after a bubble starts to accelerate into the halo. The approximation of Kompaneets is modified in order to calculate velocity and acceleration of a bubble analytically. Our new model differs from earlier ones, because it presents for the first time an analytical calculation for the expansion of superbubbles in an exponential density distribution driven by a time-dependent energy input rate. The time-sequence of supernova explosions of OB-stars is modeled using their main sequence lifetime and an initial mass function. We calculate the morphology and kinematics of superbubbles powered by three different kinds of energy input and we derive the energy input required for blow-out as a function of the density and the scale height of the ambient interstellar medium. The Rayleigh-Taylor instability timescale in the shell is calculated in order to estimate when the shell starts to fragment and finally breaks up. Analytical models are a very efficient tool for comparison to observations, like e.g. the Local Bubble and the W4 bubble discussed in this paper, and also give insight into the dynamics of superbubble evolution., Comment: 18 pages, 11 figures

An enhanced concentration of 60Fe was found in a deep ocean's crust in 2004 in a layer corresponding to an age of ~2 Myr. The confirmation of this signal in terrestrial archives as supernova-induced and detection of other supernova-produced radionuclides is of great interest. We have identified two suitable marine sediment cores from the South Australian Basin and estimated the intensity of a possible signal of the supernova-produced radionuclides 26Al, 53Mn, 60Fe and the pure r-process element 244Pu in these cores. A finding of these radionuclides in a sediment core might allow to improve the time resolution of the signal and thus to link the signal to a supernova event in the solar vicinity ~2 Myr ago. Furthermore, it gives an insight on nucleosynthesis scenarios in massive stars, the condensation into dust grains and transport mechanisms from the supernova shell into the solar system.

Aims. We present the first high-resolution non-equilibrium ionization simulation of the joint evolution of the Local Bubble (LB) and Loop I superbubbles in the turbulent supernova-driven interstellar medium (ISM). The time variation and spatial distribution of the Li-like ions Civ, Nv, and Ovi inside the LB are studied in detail. Methods. This work uses the parallel adaptive mesh refinement code EAF-PAMR coupled to the newly developed atomic and molecular plasma emission module E(A+M)PEC, featuring the time-dependent calculation of the ionization structure of H through Fe, using the latest revision of solar abundances. The finest AMR resolution is 1 pc within a grid that covers a representative patch of the Galactic disk (with an area of 1 kpc^2 in the midplane) and halo (extending up to 10 kpc above and below the midplane). Results. The evolution age of the LB is derived by the match between the simulated and observed absorption features of the Li-like ions Civ, Nv, and Ovi . The modeled LB current evolution time is bracketed between 0.5 and 0.8 Myr since the last supernova reheated the cavity in order to have N(Ovi) < 8 \times 10^12 cm-2, log[N(Civ) /N(Ovi) ] < -0.9 and log[N(Nv) /N(Ovi) ] < -1 inside the simulated LB cavity, as found in Copernicus, IUE, GHRS-IST and FUSE observations., Comment: Letter accepted for publication in Astronomy & Astrophysics

E(A+M)PEC traces the ionization structure, cooling and emission spectra of plasmas. It is written in OpenCL, runs in NVIDIA Graphics Processor Units and can be coupled to any HD or MHD code to follow the dynamical and thermal evolution of any plasma in, e.g., the interstellar medium (ISM)., Comment: To be published in "Advances in Computational Astrophysics: Methods, Tools and Outcomes", R. Dolcetta, M. Limongi, A. Tornambe (Editors), ASP Conf. Series

We present the first to date three-dimensional high-resolution hydrodynamical simulation tracing the non-equilibrium ionization evolution (using the Eborae Atomic and Molecular Plasma Emission Code - E(A+M)PEC) of the Local Bubble and Loop I superbubbles embedded in a turbulent supernova-driven interstellar medium., Comment: To be published in "Advances in Computational Astrophysics: Methods, Tools and Outcomes", R. Dolcetta, M. Limongi, A. Tornambe (Editors), ASP Conf. Series

Aims: Bow shock waves are a common feature of groups and clusters of galaxies since they are generated as a result of supersonic motion of galaxies through the intergalactic medium. The goal of this work is to present an analytical solution technique for such astrophysical hypersonic blunt body problems. Methods: A method, developed by Schneider (1968, JFM, 31, 397) in the context of aeronautics, allows calculation of the galaxy's shape as long as the shape of the bow shock wave is known (so-called inverse method). In contrast to other analytical models, the solution is valid in the whole flow region (from the stagnation point up to the bow shock wings) and in particular takes into account velocity gradients along the streamlines. We compare our analytical results with two-dimensional hydrodynamical simulations carried out with an extended version of the VH-1 hydrocode which is based on the piecewise parabolic method with a Lagrangian remap. Results: It is shown that the applied method accurately predicts the galaxy's shape and the fluid variables in the post-shock flow, thus saving a tremendous amount of computing time for future interpretations of similar objects. We also find that the method can be applied to arbitrary angles between the direction of the incoming flow and the axis of symmetry of the body. We emphasize that it is general enough to be applied to other astrophysical bow shocks, such as those on stellar and galactic scales., Comment: 11 pages, 7 figures, accepted for publication in A&A

The ISM, powered by SNe, is turbulent and permeated by a magnetic field (with a mean and a turbulent component). It constitutes a frothy medium that is mostly out of equilibrium and is ram pressure dominated on most of the temperature ranges, except for T< 200 K and T> 1E6 K, where magnetic and thermal pressures dominate, respectively. Such lack of equilibrium is also imposed by the feedback of the radiative processes into the ISM flow. Many models of the ISM or isolated phenomena, such as bubbles, superbubbles, clouds evolution, etc., take for granted that the flow is in the so-called collisional ionization equilibrium (CIE). However, recombination time scales of most of the ions below 1E6 K are longer than the cooling time scale. This implies that the recombination lags behind and the plasma is overionized while it cools. As a consequence cooling deviates from CIE. This has severe implications on the evolution of the ISM flow and its ionization structure. Here, besides reviewing several models of the ISM, including bubbles and superbubbles, the validity of the CIE approximation is discussed, and a presentation of recent developments in modeling the ISM by taking into account the time-dependent ionization structure of the flow in a full-blown numerical 3D high resolution simulation is presented., Comment: 15 pages, 6 figures with 15 panels. Invited review for "The Dynamic ISM: A celebration of the Canadian Galactic Plane Survey" conference; Naramata BC, Canada June 6-10, 2010. To be published in the ASP Conference Series

Aims: We study the diffuse X-ray emission observed in the field of view of the pulsar B 0540-69 in the Large Magellanic Cloud (LMC) by XMM-Newton. We want to understand the nature of this soft diffuse emission, which coincides with the superbubble in the HII region N 158, and improve our understanding of the evolution of superbubbles. Methods: We analyse the XMM-Newton spectra of the diffuse emission. Using the parameters obtained from the spectral fit, we perform calculations of the evolution of the superbubble. The mass loss and energy input rates are based on the initial mass function (IMF) of the observed OB association inside the superbubble. Results: The analysis of the spectra shows that the soft X-ray emission arises from hot shocked gas surrounded by a thin shell of cooler, ionised gas. We show that the stellar winds alone cannot account for the energy inside the superbubble, but the energy release of 2 - 3 supernova explosions in the past ~1 Myr provides a possible explanation. Conclusions: The combination of high sensitivity X-ray data, allowing spectral analysis, and analytical models for superbubbles bears the potential to reveal the evolutionary state of interstellar bubbles, if the stellar content is known., Comment: 7 pages. Accepted for publication in A&A

High-resolution non-ideal magnetohydrodynamical simulations of the turbulent magnetized ISM, powered by supernovae types Ia and II at Galactic rate, including self-gravity and non-equilibriuim ionization (NEI), taking into account the time evolution of the ionization structure of H, He, C, N, O, Ne, Mg, Si, S and Fe, were carried out. These runs cover a wide range (from kpc to sub-parsec) of scales, providing resolution independent information on the injection scale, extended self-similarity and the fractal dmension of the most dissipative structures., Comment: 2 pages, 1 figure. Invited talk to the Joint Discussion 15 "Magnetic Fields in Diffuse Media". To appear in Highlights of Astronomy, Vol. 15, Proc. of the XXVIIth IAU General Assembly, Rio de Janeiro, Brazil, August 2009, eds. E. G. Dal Pino & A. Lazarian, Cambridge University Press

We investigate the role of supernova (SN)-driven galactic winds in the chemical enrichment of the intracluster medium (ICM). Such outflows on galactic scales have their origin in huge star forming regions and expel metal enriched material out of the galaxies into their surroundings as observed, for example, in the nearby starburst galaxy NGC 253. As massive stars in OB-associations explode sequentially, shock waves are driven into the interstellar medium (ISM) of a galaxy and merge, forming a superbubble (SB). These SBs expand in a direction perpendicular to the disk plane following the density gradient of the ISM. We use the 2D analytical approximation by Kompaneets (1960) to model the expansion of SBs in an exponentially stratified ISM. This is modified in order to describe the sequence of SN-explosions as a time-dependent process taking into account the main-sequence life-time of the SN-progenitors and using an initial mass function to get the number of massive stars per mass interval. The evolution of the bubble in space and time is calculated analytically, from which the onset of Rayleigh-Taylor instabilities in the shell can be determined. In its further evolution, the shell will break up and high-metallicity gas will be ejected into the halo of the galaxy and even into the ICM. We derive the number of stars needed for blow-out depending on the scale height and density of the ambient medium, as well as the fraction of alpha- and iron peak elements contained in the hot gas. Finally, the amount of metals injected by Milky Way-type galaxies to the ICM is calculated confirming the importance of this enrichment process., Comment: 6 pages, 7 figures, to be published in Astronomische Nachrichten (proceedings of Symposium 6 of the JENAM 2008, Vienna)

In this paper we review the modeling of the Local Bubble (LB) with special emphasis on the progress we have made since the last major conference "The Local Bubble and Beyond (I)" held in Garching in 1997. Since then new insight was gained into the possible origin of the LB, with a moving group crossing its volume during the last 10 - 15 Myr being most likely responsible for creating a local cavity filled with hot recombining gas. Numerical high resolution 3D simulations of a supernova driven inhomogeneous interstellar medium show that we can reproduce both the extension of the LB and the OVI column density in absorption measured with FUSE for a LB age of 13.5 - 14.5 Myr. We further demonstrate that the LB evolves like an ordinary superbubble expanding into a density stratified medium by comparing analytical 2D Kompaneets solutions to NaI contours, representing the extension of the local cavity. These results suggest that LB blow-out into the Milky Way halo has occurred roughly 5 Myr ago., Comment: 8 pages, 3 figures, to appear in the proceedings of "The Local Bubble and Beyond II", Philadelphia, USA, April 21-24, 2008

We present an overview of the Chandra ACIS Survey of M33 (ChASeM33): A Deep Survey of the Nearest Face-on Spiral Galaxy. The 1.4 Ms survey covers the galaxy out to $R \approx 18\arcmin (\approx 4$ kpc). These data provide the most intensive, high spatial resolution assessment of the X-ray source populations available for the confused inner regions of M33. Mosaic images of the ChASeM33 observations show several hundred individual X-ray sources as well as soft diffuse emission from the hot interstellar medium. Bright, extended emission surrounds the nucleus and is also seen from the giant \hii regions NGC 604 and IC 131. Fainter extended emission and numerous individual sources appear to trace the inner spiral structure. The initial source catalog, arising from $\sim$~2/3 of the expected survey data, includes 394 sources significant at the $3\sigma$ confidence level or greater, down to a limiting luminosity (absorbed) of $\sim$1.6\ergs{35} (0.35 -- 8.0 keV). The hardness ratios of the sources separate those with soft, thermal spectra such as supernova remnants from those with hard, non-thermal spectra such as X-ray binaries and background active galactic nuclei. Emission extended beyond the Chandra point spread function is evident in 23 of the 394 sources. Cross-correlation of the ChASeM33 sources against previous catalogs of X-ray sources in M33 results in matches for the vast majority of the brighter sources and shows 28 ChASeM33 sources within 10\arcsec of supernova remnants identified by prior optical and radio searches. This brings the total number of such associations to 31 out of 100 known supernova remnants in M33., Comment: accepted for publication ApJS, full resolution images and complete tables available at http://hea-www.harvard.edu/vlp_m33_public/

We study, by means of adaptive mesh refinement hydro- and magnetohydrodynamical simulations that cover a wide range of scales (from kpc to sub-parsec), the dimension of the most dissipative structures and the injection scale of the turbulent interstellar gas, which we find to be about 75 pc, in agreement with observations. This is however smaller than the average size of superbubbles, but consistent with significant density and pressure changes in the ISM, which leads to the break-up of bubbles locally and hence to injection of turbulence. The scalings of the structure functions are consistent with log-Poisson statistics of supersonic turbulence where energy is dissipated mainly through shocks. Our simulations are different from previous ones by other authors as (i) we do not assume an isothermal gas, but have temperature variations of several orders of magnitude and (ii) we have no artificial forcing of the fluid with some ad hoc Fourier spectrum, but drive turbulence by stellar explosions at the Galactic rate, self-regulated by density and temperature thresholds imposed on the ISM gas., Comment: Five pages and three figures. Accepted for publication in Astrophysical Journal (Letters)

We present and interpret new X-ray data for M33SNR21, the brightest X-ray supernova remnant (SNR) in M33. The SNR is in seen projection against (and appears to be interacting with) the bright HII region NGC592. Data for this source were obtained as part of the Chandra ACIS Survey of M33 (ChASeM33) Very Large Project. The nearly on-axis Chandra data resolve the SNR into a ~5" diameter (20 pc at our assumed M33 distance of 817+/-58 kpc) slightly elliptical shell. The shell is brighter in the east, which suggests that it is encountering higher density material in that direction. The optical emission is coextensive with the X-ray shell in the north, but extends well beyond the X-ray rim in the southwest. Modeling the X-ray spectrum with an absorbed sedov model yields a shock temperature of 0.46(+0.01,-0.02) keV, an ionization timescale of n_e t = $2.1 (+0.2,-0.3) \times 10^{12}$ cm$^{-3}$ s, and half-solar abundances (0.45 (+0.12, -0.09)). Assuming Sedov dynamics gives an average preshock H density of 1.7 +/- 0.3 cm$^{-3}$. The dynamical age estimate is 6500 +/- 600 yr, while the best fit $n_e t$ value and derived $n_e$ gives 8200 +/- 1700 yr; the weighted mean of the age estimates is 7600 +/- 600 yr. We estimate an X-ray luminosity (0.25-4.5 keV) of (1.2 +/- 0.2) times $10^{37}$ ergs s$^{-1}$ (absorbed), and (1.7 +/- 0.3) times $10^{37}$ ergs s$^{-1}$ (unabsorbed), in good agreement with the recent XMM-Newton determination. No significant excess hard emission was detected; the luminosity $\le 1.2\times 10^{35}$ ergs s$^{-1}$ (2-8 keV) for any hard point source., Comment: 27 pages, 6 figures (3 color). ApJ (in press)

It is shown that a number of key observations of the Galactic ISM can be understood, if it is treated as a highly compressible and turbulent medium energized predominantly by supernova explosions (and stellar winds). We have performed extensive numerical high resolution 3D hydrodynamical and magnetohydrodynamical simulations with adaptive mesh refinement over sufficiently long time scales to erase memory effects of the initial setup. Our results show, in good agrement with observations, that (i) volume filling factors of the hot medium are modest (typically below 20%), (ii) global pressure is far from uniform due to supersonic (and to some extent superalfvenic) turbulence, (iii) a significant fraction of the mass (about 60%) in the warm neutral medium is in the thermally unstable regime (500 K < T < 5000 K), (iv) the average number density of OVI in absorption is 1.81 10^{-8} cm^{-3}, in excellent agreement with Copernicus and FUSE data, and its distribution is rather clumpy, consistent with its measured dispersion with distance., Comment: Invited Paper at IAU Symposium 237 "Triggered Star Formation in a Turbulent ISM", Bruce Elmegreen and Jan Palous (eds.), 6 pages, 7 Figures

The Local and Loop I superbubbles are the closest and best investigated supernova (SN) generated bubbles and serve as test laboratories for observations and theories of the interstellar medium. Since the morphology and dynamical evolution of bubbles depend on the ambient density and pressure distributions, a realistic modelling of the galactic environment is crucial for a detailed comparison with observations. We have performed 3D high resolution (down to 1.25 pc on a kpc-scale grid) hydrodynamic simulations of the Local Bubble (LB) and the neighbouring Loop I (L1) superbubble in a realistically evolving inhomogeneous background ISM, disturbed already by SN explosions at the Galactic rate for 200 Myr before the LB and L1 are generated. The LB is the result of 19 SNe occurring in a moving group, which passed through the present day local HI cavity. We can reproduce (i) the OVI column density in absorption within the LB in agreement with COPERNICUS and recent FUSE observations, giving N(OVI) <2 10^{13} cm^-2 and N(OVI)<7 10^{12} cm^-2, respectively, (ii) the observed sizes of the Local and Loop I superbubbles, (iii) the interaction shell between LB and L1, discovered with ROSAT, (iv) constrain the age of the LB to be 14.5+0.7/-0.4 Myr, (v) predict the merging of the two bubbles in about 3 Myr, when the interaction shell starts to fragment, (vi) the generation of blobs like the Local Cloud as a consequence of a dynamical instability. We find that evolving superbubbles strongly deviate from idealised self-similar solutions due to ambient pressure and density gradients, as well as due to turbulent mixing and mass loading. Hence, at later times the hot interior can break through the surrounding shell, which may also help to explain the puzzling energy "deficit" observed in LMC bubbles., Comment: Accepted for publication in Astronomy and Astrophysics Letters. The paper contains 5 pages and 11 figures. Fig. 1a replaced by correct figure

The statistical properties of interstellar turbulence are studied by means of three-dimensional high-resolution HD and MHD simulations of a SN-driven ISM. It is found that the longitudinal and transverse turbulent length scales have time averaged (over a period of 50 Myr) ratios of 0.5-0.6, almost similar to the one expected for isotropic homogeneous turbulence. The mean characteristic size of the larger eddies is found to be ~75 pc. Furthermore, the scalings of the structure functions measured in the simulated disk show unambiguous departure from the Kolmogorv (1941) model being consistent with the latest intermittency studies of supersonic turbulence (Politano & Pouquet 1995; Boldyrev 2002). Our results are independent of the resolution, indicating that convergence has been reached, and that the unresolved smaller dissipative scales do not feed back on the larger ones., Comment: 4 pages, 2 figures including 5 plots. Contributed paper delivered at the Portuguese National Astronomical & Astrophysics Meeting, held in Lisbon (Portugal) on 28-29 July 2005

We study the ovi distribution in space and time in a representative section of the Galactic disk by 3D adaptive mesh refinement HD and MHD simulations of the ISM, including the disk-halo-disk circulation. The simulations describe a supernova driven ISM on large (10 kpc) and small (1.25 pc) scales over a sufficiently large timescale (400 Myrs) in order to establish a global dynamical equilibrium. The Ovi column density, N(Ovi), is monitored through lines of sight measurements at different locations in the simulated disk. One has been deliberately chosen to be inside of a hot bubble, like our own Local Bubble, while the other locations are random. We obtain a correlation between N(Ovi) and distance, which is independent of the observer's vantage point in the disk. In particular, the location of the observer inside a hot bubble does not have any influence on the correlation, because the contribution of an individual bubble (with a typical extension of 100 pc) is negligibly small. We find a remarkable agreement between the Ovi column densities (as a function of distance) and the averaged Ovi density (~1.8x10^{-8}$ cm$^{-3}$) in the disk from our simulations and the values observed with Copernicus, and FUSE. Our results strongly support the important r\^ole of turbulent mixing in the distribution of Ovi clumps in the ISM. Supernova induced turbulence is quite strong and unavoidable due to shearing motions in the ISM and operates on a large range of scales., Comment: 4 pages using emulateapj5 style, 5 figures including a simulation image. Accepted for publication in ApJ Letters

Dealing numerically with the turbulent nature and non-linearity of the physical processes involved in the ISM requires the use of sophisticated numerical schemes coupled to HD and MHD mathematical models. SNe are the main drivers of the interstellar turbulence by transferring kinetic energy into the system. This energy is dissipated by shocks (which is more efficient) and by molecular viscosity. We carried out adaptive mesh refinement simulations (with a finest resolution of 0.625 pc) of the turbulent ISM embedded in a magnetic field with mean field components of 2 and 3 $\mu$G. The time scale of our run was 400 Myr, sufficiently long to avoid memory effects of the initial setup, and to allow for a global dynamical equilibrium to be reached in case of a constant energy input rate. It is found that the longitudinal and transverse turbulent length scales have a time averaged (over a period of 50 Myr) ratio of 0.52-0.6, almost similar to the one expected for isotropic homogeneous turbulence. The mean characteristic size of the larger eddies is found to be \~75 pc in both runs. In order to check the simulations against observations, we monitored the OVI and HI column densities within a superbubble created by the explosions of 19 SNe having masses and velocities of the stars that exploded in vicinity of the Sun generating the Local Bubble. The model reproduces the FUSE absorption measurements towards 25 white dwarfs of the \ovi column density as function of distance and of \nhi. In particular for lines of sight with lengths smaller than 120 pc it is found that there is no correlation between N(OVI) and N(HI)., Comment: Extended contributed paper by M.A. presented at the international conference "The Magnetized Plasma in Galaxy Evolution", held at the Jagiellonian University, Cracow (Poland), 27.9.-1.10. 2004, K.T. Chyzy, R.-J. Dettmar, K. Otianowska-Mazur (eds.), 8 pages, 5 figures

We review recent 3D high resolution numerical HD and MHD studies of a multi-component and multi-phase ISM. The computational grid was chosen large enough in the disk to represent typical ISM gas patterns, and in the halo to include the full extent of the Galactic fountain. The evolution of the ISM is driven by supernovae of all types and followed for 400 Myrs, long enough to get rid of memory effects of the initial distributions. The results are substantially different from previous classical analytical models and entail: (i) a very inhomogeneous distribution of ISM gas, (ii) a high level of supernova driven turbulence, (iii) an active Galactic fountain flow, reaching out to about 5 kpc on either side of the disk, (iv) a low volume filling factor for the hot gas of about 20%, (v) a very weak correlation between magnetic field and gas density, n, for n < 100 cm^-3, and, (vi) about 50% of the gas disk mass with n < 100 cm^-3, residing in classically thermally unstable temperature regimes., Comment: Invited Review Paper, given on the international conference on "The Magnetized Plasma in Galaxy Evolution", held at the Jagiellonian University, Cracow (Poland), 27.9.-1.10. 2004, K.T. Chyzy, R.-J. Dettmar, K. Otianowska-Mazur (eds.), 8 pages, 12 figures, 1 table

In star forming disk galaxies, matter circulation between stars and the interstellar gas, and, in particular the energy input by random and clustered supernova explosions, determine the dynamical and chemical evolution of the ISM, and hence of the galaxy as a whole. Using a 3D MHD code with adaptive mesh refinement developed for this purpose, we have investigated the r\^ole of magnetized matter circulation between the gaseous disk and the surrounding galactic halo. Special emphasis has been put on the effect of the magnetic field with respect to the volume and mass fractions of the different ISM ``phases'', the relative importance of ram, thermal and magnetic pressures, and whether the field can prevent matter transport from the disk into the halo. The simulations were performed on a grid with an area of 1 kpc$^{2}$, centered on the solar circle, extending $\pm 10$ kpc perpendicular to the galactic disk with a resolution as high as 1.25 pc. The simulations were run for a time scale of 400 Myr, sufficiently long to avoid memory effects of the initial setup, and to allow for a global dynamical equilibrium to be reached in case of a constant energy input rate. (...) We find that in general gas transport into the halo in 3D is not prevented by an initial disk parallel magnetic field, but only delayed initially, for as long as it is needed to punch holes into the thick magnetized gas disk. The mean volume filling factor of the hot phase in the disk is similar in HD and MHD (the latter with a total field strength of 4.4 $\mu$G) runs, amounting to $\sim 17-21%$ for the Galactic supernova rate., Comment: Paper accepted for publication in A&A (31 Jan); 17 pages with 10 Figures including 6 images and 16 plots (all in low quality jpeg files). For better resolution images contact the authors

State of the art models of the ISM use adaptive mesh refinement to capture small scale structures, by refining on the fly those regions of the grid where density and pressure gradients occur, keeping at the same time the existing resolution in the other regions. With this technique it became possible to study the ISM in star-forming galaxies in a global way by following matter circulation between stars and the interstellar gas, and, in particular the energy input by random and clustered supernova explosions, which determine the dynamical and chemical evolution of the ISM, and hence of the galaxy as a whole. In this paper we review the conditions for a self-consistent modelling of the ISM and present the results from the latest developments in the 3D HD/MHD global models of the ISM. Special emphasis is put on the effects of the magnetic field with respect to the volume and mass fractions of the different ISM ``phases'', the relative importance of ram, thermal and magnetic pressures, and whether the field can prevent matter transport from the disk into the halo. The simulations were performed on a grid with a square area of 1 kpc$^{2}$, centered on the solar circle, extending $\pm 10$ kpc perpendicular to the galactic disk with a resolution as high as 1.25 pc. The run time scale was 400 Myr, sufficiently long to avoid memory effects of the initial setup, and to allow for a global dynamical equilibrium to be reached in case of a constant energy input rate., Comment: 11 pages, 6 figures (6 postscript plots and 2 jpg images), Paper of Review Talk given by M. de Avillez at the conference "The Young Local Universe", XXXIXth Rencontres de Moriond, La Thuile, Aosta Valley, Italy, March 21 - 28, 2004, eds. T. Montmerle, A. Chalabaev, J. Tran Thanh Van

The Local Bubble (LB) is an X-ray emitting region extending 100 pc in radius in the Galactic plane and 300 pc perpendicular to it, and it is embedded in a somewhat larger H{\sc i} deficient cavity. Its origin and spectral properties in UV, EUV and X-rays are still poorly understood. We have performed 3D high resolution (down to 1.25 pc) hydrodynamic superbubble simulations of the LB and Loop I superbubble in a realistic \emph{inhomogeneous} background ISM, disturbed by supernova (SN) explosions at the Galactic rate. We can reproduce (i) the size of the bubbles (in contrast to similarity solutions), (ii) the interaction shell with Loop I, discovered with ROSAT, (iii) predict the merging of the two bubbles in about 3 Myr, when the interaction shell starts to fragment, and, (iv) the generation of blobs like the Local Cloud as a consequence of a dynamical instability. The \ion{O}{6} column densities are monitored and found to be in excellent agreement with \textsc{Copernicus} and FUSE absorption line data, showing LB column densities $<1.7 \times 10^{13} {\rm cm}^{-2}$, in contrast to other existing models., Comment: 3 Pages, 3 figures (including 1 jpg image and 3 plots); poster paper to appear in "Astrophysics in the Far Ultraviolet: Five Years of Discovery with FUSE", 2005, ASP Conference Series, eds. G. Sonneborn, H. W. Moos, and B-G Andersson

The role of matter circulation between the disk and halo in establishing the volume filling factors of the different ISM phases in the Galactic disk is investigated, using a modified version of the three-dimensional supernova-driven ISM model of Avillez (2000). We carried out adaptive mesh refinement simulations of the ISM with five supernova rates (in units of the Galactic value), $\sigma/\sigma_{Gal}=1$, 2, 4, 8 and 16 (corresponding to starburst conditions) using three finer level resolutions of 2.5, 1.25 and 0.625 pc, allowing us to understand how resolution would affect the volumes of gas phases in pressure equilibrium. We find that the volume filling factors of the different ISM phases depend sensitively on the existence of a duty cycle between the disk and halo acting as a pressure release valve for the hot (T> 10^5.5 K) phase in the disk., Comment: Accepted for publication in Astronomy & Astrophysics. 14 pages with 9 figures that include 9 simulations images and 20 plots in low resolution jpeg format. High resolution postscript images are available upon request to mavillez@galaxy.lca.uevora.pt

We have performed high resolution 3D simulations of the Local Bubble (with 1.25 pc finest resolution) in a realistic background ISM, jointly with the dynamical evolution of the neighbouring Loop I superbubble. We can reproduce (i) the size of the bubbles (in contrast to similarity solutions), (ii) the interaction shell with Loop I, discovered with ROSAT, (iii) predict the merging of the two bubbles in about 3 Myr, when the interaction shell starts to fragment, and, (iv) the generation of blobs like the Local Cloud as a consequence of a dynamical instability., Comment: 2 pages, 2 simulation images in jpeg format, to appear in the proceedings of ``From Observations to Self-Consistent Modelling of the ISM in Galaxies'', M.A. de Avillez and D. Breitschwerdt (eds.), Kluwer

We have performed high resolution 3D simulations with adaptive mesh refinement, following the ISM evolution in a star forming galaxy both on small (<1 pc) and large (>10 kpc) scales, enabling us to track structures in cooling shock compressed regions as well as the entire Galactic fountain flow. It is shown in an MHD run that the latter one is not inhibited by a large scale disk parallel magnetic field. The fountain plays a vital role in limiting the volume filling factor of the hot gas. Contrary to classical models most of the gas between 100K and 8000 K is found to be thermally unstable. On scales of superbubbles we find that the internal temperature structure is rather inhomogeneous for an old object like our Local Bubble, leading to low OVI column densities, consistent with observations., Comment: 8 pages, 4 figures that include 1 simulation image in jpeg format and 3 plots, to be published in How Does the Galaxy Works?, E.J. Alfaro, E.Perez, J. Franco (eds.), Kluwer, Dordrecht

We give a summary of the current state of Local Bubble research, resulting from the discussions of a dedicated panel meeting. After more than 25 years of intense observational and theoretical work, we are still far from a coherent picture, although a probable one emerges at the horizon. A multi-supernova origin seems to be the best guess, with non-equilibrium cooling and soft X-ray emission accompanying its expansion. In addition our vantage point may force us to accept a substantial but quantitatively unknown contribution from heliospheric emission., Comment: 11 pages, 4 figures, Summary of the Panel Discussion "The Local Bubble", to appear in: Proceedings of the Conference "How the Galaxy Works - Galactic Tertulia: A Tribute to Don Cox and Ron Reynolds'', Granada (Spain), 23-27 June 2003, Kluwer (in press), eds. E.J Alfaro, E. Perez, J. Franco

We present the first to date high resolution calculations of the ISM down to scales of 0.625 pc of the global and local ISM. The simulations show the morphology and structure of the different ISM phases and reproduce many of the features that have been observed in the Milky Way and other galaxies. In particular, they show that the hot gas has a moderately low volume filling factor (~20%) even in the absence of magnetic fields. Also, cold gas is mainly concentrated in filamentary structures running perpendicular to the midplane forming and dissipating within 10-12 Myr. Compression is the dominant process for their formation, but thermal instability also plays a role. Also the evolution of the Local Bubble is simulated by multi-supernova explosions; calculated extensions after ~13 Myr match observations., Comment: 7 pages, 3 Figures that include 4 simulation images (in jpeg format) and 2 plots (in ps format), to appear in the proceedings of "Star Formation Through Time" - A conference to honour Roberto J. Terlevich, ASP Conference Series

Starburst galaxies are generally associated with extended X-ray and radio halos, giving a clear hint of an outflow of gas and relativistic particles from the disk into the halo. The driving agents are, not surprisingly, active star forming regions, injecting hot gas and cosmic rays generated by supernova remnant and superbubble shock waves. The dynamics of the outflow and the thermal evolution of the plasma are strongly coupled, and therefore a self-consistent model is necessary for a satisfactory description. Since the plasma temperature is between one and a few million Kelvin, the halo is most conspicuous in soft X-rays. It will be shown that X-ray data obtained recently with XMM-Newton EPIC pn bear clear spectral signatures that are in strong disagreement with an isothermal halo in collisional ionization equilibrium (CIE). Instead a temperature structure in X-ray halos is observed. It will be demonstrated that a galactic wind outflow model in which the non-equilibrium ionization structure is calculated self-consistently can give a satisfactory and physical explanation for the X-ray spectral characteristics, e.g. in case of the local starburst galaxy NGC 3079. In particular, high subsolar abundances, that have been reported from X-ray observations in some cases, are shown to be artefacts of CIE spectral fit models. It is found that spectral models are strongly constrained by the presence of diagnostic lines such as OVII and OVIII as well as Fe-L line complexes. Thus a detailed spectral X-ray model will help to provide important galactic wind parameters, such as mass loss rate and velocity profile, which may also serve as valuable input for galactic outflows in the early universe., Comment: 7 pages, 7 figures, Invited Review Talk at Conference "Winds, Bubbles & Explosions: A Conference to Honor John Dyson", Patzcuaro, Mexico, Sept. 9 - 13, 2002

The dynamical evolution of hot optically thin plasmas in the ISM crucially depends on the heating and cooling processes. It is essential to realize that all physical processes that contribute operate on different time scales. In particular detailed balancing is often violated since the statistically inverse process of e.g. collisional ionization is recombination of an ion with two electrons, which as a three-body collision is usually dominated by radiative recombination, causing a departure from collisional ionization equilibrium. On top of these differences in atomic time scales, hot plasmas are often in a dynamical state, thereby introducing another time scale, which can be the shortest one. The non-equilibrium effects will be illustrated and discussed in the case of galactic outflows. It will be shown, that spectral analyses of X-ray data of edge-on galaxies show a clear signature in the form of "multi-temperature" halos, which can most naturally be explained by the "freezing-in" of highly ionized species in the outflow, which contribute to the overall spectrum by DELAYED RECOMBINATION. This naturally leads to a non-equilibrium cooling function, which modifies the dynamics, which in turn changes the plasma densities and thermal energy budget, thus feeding back on the ionization structure. Therefore SELF-CONSISTENT modelling is needed., Comment: 11 pages, 11 figures, Invited Talk on the JENAM 2002 Workshop "From Observations to Self-Consistent Modelling of the ISM in Galaxies", Kluwer Academic Publishers (in press); Figure 1 (right) replaced

We present a Chandra X-ray observation that shows, unambiguously for the first time, the presence of a giant diffuse X-ray-emitting corona around the edge-on disk galaxy NGC 4631. This corona, with a characteristic thermal temperature of 2-7\times10^6 K, extends as far as 8 kpc away from the galactic plane. The X-ray morphology resembles the radio halo of the galaxy, indicating a close connection between outflows of hot gas, cosmic rays, and magnetic field from the galactic disk. Enhanced diffuse X-ray emission is apparently enclosed by numerous H\alpha-emitting loops blistered out from the central disk of the galaxy, as is evident in a comparison with our deep Hubble Space Telescope imaging., Comment: 3 pages, 8 figures. To appear in ApJ Letters. Full resolution version available at http://xray.astro.umass.edu/n4631.ps.gz

The development of galactic fountain theories is reviewed with special emphasis on the different approaches and concepts that have been used in the past. In particular the outstanding contribution of Franz Kahn to our physical understanding is appreciated. It is argued that galactic outflows represent an essential phase during galaxy evolution. The dynamics of the outflow imprints its signature on the emission spectra of soft X-rays, which may well be observable with AXAF and XMM. Finally, some remarks about winds in starburst galaxies and AGN are made., Comment: 12 pages; contribution to the proceedings of "Astrophysical Dynamics" (Evora, April 1999; in honour of Franz Kahn), D. Berry, D. Breitschwerdt, A. da Costa, J. Dyson (eds); to appear in Ap&SS

We present here an analysis of the X-ray properties of a sample of LINER galaxies observed with the ROSAT PSPC and HRI instruments. A spatial analysis shows that the bulk of the X-ray emission is consistent with arising from a point source; some extended emission appears at weak emission levels. The X-ray spectra are formally best described by a powerlaw with photon index Gamma_x ~ -2 or thermal emission from a Raymond-Smith plasma with highly subsolar abundances (Z < 0.1). Several emission mechanisms that might contribute to the observed X-ray spectra are discussed. In particular, we take the very subsolar abundances derived from Raymond-Smith fits as an indication of a more complex emission mechanism, like the presence of a second hard component or plasma out of collisional-ionization equilibrium., Comment: 4 pages incl. 2 figures (needs crckapb.sty); contribution to the proc. of `Astrophysical Dynamics' (Evora, April 14-16, 1999), D. Berry, D. Breitschwerdt, A. da Costa, J. Dyson (eds); to appear in Ap&SS. Preprint and related papers are available at http://www.xray.mpe.mpg.de/~skomossa/

Warm absorbers are an important new probe of the central region of active galaxies (AGN). Observing and modeling this component provides a wealth of information on the nature of the warm absorber itself, its relation to other components of the active nucleus, and the intrinsic AGN X-ray spectral shape. We briefly review the general properties of dusty warm gas. For the first time, we then apply such a model to the IR loud quasar IRAS 13349+2438. It was the first to be suggested to host a dusty warm absorber (Brandt et al. 1996), but has not yet been modeled as such., Comment: 4 pages incl. 2 figures (needs crckapb.sty); contribution to the proc. of `Astrophysical Dynamics' (Evora, April 14-16, 1999), to appear in Ap&SS; Preprint and related papers available at http://www.xray.mpe.mpg.de/~skomossa/

The Narrow-line Seyfert 1 galaxy RXJ0134.3-4258 was detected during the ROSAT all-sky survey with an ultrasoft spectrum (Greiner 1996). Our later pointed observation led to the discovery of drastic spectral variability. Here, we present the first detailed analysis of the soft X-ray properties of this peculiar source., Comment: 4 pages incl. 2 figures (needs crckapb.sty); contribution to the proc. of `Astrophysical Dynamics' (Evora, April 14-16, 1999), to appear in Ap&SS; Preprint and related papers on RXJ0134.3-4258 are available at http://www.xray.mpe.mpg.de/~skomossa/

We present the first dynamically and thermally self-consistent calculations of fast adiabatically expanding gas flows from the Galactic disk into the halo. It is shown that in a hot plasma (T >= 10^6 K) with a high overpressure with respect to the ambient medium, the dynamical time scale is much shorter than the intrinsic time scales (e.g. for recombination, collisional excitation and ionization etc.). Therefore dynamical models that use collisional ionization equilibrium (CIE) cooling functions for the evolution of the plasma are in general not correct. In particular, the emission spectra obtained from non-equilibrium calculations are radically different. We describe a method to obtain self-consistent solutions using an iterative procedure. It is demonstrated that soft X-ray background emission between 0.3 and 1.5 keV can be well explained by a superposition of line emission and delayed recombination of an initially hot plasma streaming away from the Galactic disk (outflow and/or winds). In addition to these local winds we also present calculations on global winds from spiral galaxies, which originate from a hot and quiescent galactic corona. We also emphasize that it is dangerous to derive plasma temperatures merely from line ratios of ionized species, such as NV/OVI, unless the dynamical and thermal history of the plasma is known., Comment: 19 pages incl. 15 figures, to appear in Astronomy and Astrophysics Main Journal