We present the results of population synthesis simulations aimed at exploring the evolution of the 2–10 keV luminosity of X-ray binaries in a young stellar population. The results are applicable to populations of extragalactic X-ray binaries in starburst galaxies and many LINERs. We find that the integrated 2–10 keV luminosity of the simulated population reaches a maximum of about $10^{40}\,{\rm erg~s}^{-1}$ after approximately 20 Myr (for a star-formation rate of 10 M$_{\odot}$ yr$^{-1}$) and remains significant even after the end of star formation and the demise of the luminous OB stars. The results of our simulation are in agreement with recently-derived correlations between the X-ray luminosity starburst galaxies and their star-formation rate. We also find that the cumulative luminosity function is initially fairly flat, in agreement with recent observational results, becoming steeper as the population ages and the high-mass X-ray binaries are succeeded by binaries with progressively lighter donor stars. Using the output of Hydrogen-ionizing far-UV photons from the stellar population, we can plot the track of a “post-starburst” system in the $L_{\rm X}-L_{\rm H\alpha}$ diagram. The system starts off in the starburst locus but quickly evolves to the AGN locus where it lingers for at least 1 Gyr.

We review the main laboratory results of investigations of processes of molecular hydrogen formation on surfaces. The problem of the formation of molecular hydrogen is a fundamental issue in astrophysics/astrochemistry, because of the great importance that molecular hydrogen has for the structure and evolution of our Universe. Such experiments are done using ultra-high vacuum, low temperature, and atomic/molecular beam techniques to study the formation of molecular hydrogen on dust grain analogues in conditions as close as technically feasible to the ones present in relevant ISM environments. In experiments conducted at Syracuse University, we studied H2 formation on the three most ISM-relevant classes of surfaces: silicates, carbonaceous materials and amorphous water ice. Our experimental investigations range from the evaluation of the catalytic efficiency of the studied surfaces to the energetics of the reaction, i.e. the partition of the formation energy between the grain and the nascent molecule. Such measurements have been done by changing various parameters such as: the temperature of the interstellar dust analogue, the kinetic temperature of the atoms, the morphology of the surface and, to be completed soon, the composition of the solid. Quantitative and qualitative information on the processes of H2 formation is then fed in theoretical models to extract results that pertain to desired ISM environments.

A mid-infrared high-resolution spectral survey of the source IRC+10216 (CW Leo) has been carried out between 11 and 14 $\mu$m. A large number of lines of C$_2$H$_2$ and HCN and their most abundant isotopologues, have been identified. Lines involving high-energy ro-vibrational levels allow an accurate derivation of the physical and chemical conditions in the innermost envelope. We have developed a radiative transfer model capable of fitting the observed lines satisfactorily. The fit of more than 200 ro-vibrational lines allowed us to get the kinetic, vibrational and rotational temperatures and the abundances of the C$_2$H$_2$ and HCN between 1 and 300 R$_*$.

Based on over two decades of experimental, observational, and theoretical studies by scientists around the world, it is now widely accepted that the composite emission of mixtures of vibrationally-excited PAHs and PAH ions can accommodate the general pattern of band positions, intensities, and profiles observed in the discrete IR emission features of carbon-rich interstellar dust, as well as the variations in those characteristics. These variations provide insight into the detailed nature of the emitting PAH population and reflect conditions within the emitting regions giving this population enormous potential as probes of astrophysical environments. Moreover, the ubiquity and abundance of this material has impacts that extend well beyond the IR.

In this paper we will examine recent, combined experimental, theoretical, and observational studies that indicate that nitrogen-substituted PAHs represent an important component of the interstellar dust population, and we will go on to explore some of the ramifications of this result. We will also explore the results of recent experimental studies of the strong, low-lying electronic transitions of ionized PAH ions in the near-IR (0.7–2.5 $\mu$m) and explore the role that these transitions might play in pumping the PAH IR emission in regions of low excitation.

Chandra and XMM-Newton improve our understanding of X-ray populations in galaxies. In particular, there exists a class of ultra-luminous X-ray sources (ULXs) for which the observed luminosity is greater than $10^{39}$ ergs s$^{-1}$. ULXs are of great interest since they represent a population of possible intermediate-mass black holes. While the spectra of majority of ULXs are similar to Galactic X-ray binaries, a few ULXs have very soft X-ray emission ($kT=50$–100 eV) resembling supersoft X-ray sources (SSSs) discovered in the Milky Way and the Magellanic Clouds. We here report some recent multiwavelength observations of three ultra-luminous SSSs in M101, NGC 300, and the Antennae. They have shown many interesting behaviors such as state transitions, spectral changes, and time variabilities in different timescales. Unlike typical SSSs, ultra-luminous SSSs are unlikely associated with white dwarfs because of the high X-ray luminosities. We discuss some binary models involving stellar-mass and intermediate-mass black holes to explain the nature of the systems.

We report the results from an homogeneous analysis of the X-ray (ACIS-S/Chandra) data available for a sample of 52 LINER galaxies. The X-ray morphology has been classified attending to their nuclear compactness in the hard band (4.5–8.0 keV), into 2 categories: AGN-like nuclei (with a clearly identified unresolved nuclear source) and Starburst-like nuclei (without a clear nuclear source). 60% of the total sample are classified as AGNs, with a median luminosity of $\rm{L_{X}(2.0\hbox{-}10.0 keV)=2.5\times 10^{40} erg s^{-1}}$, which is an order of magnitude higher than that for SB-like nuclei. The spectral fitting allows to conclude that most of the objects need a non-negligible thermal contribution. When no spectral fitting can be performed (low signal-to-noise ratio), the Color-Color diagrams allow us to compute physical parameters such as density column, temperature of the thermal model or spectral index and therefore to analyze the origin of the X-ray emission. All X-ray morphology, spectral fitting and Color-Color diagrams allow conclude that a high percentage of LINER galaxies host AGN nuclei.

We present results of the X-ray spectral analysis of the $\sim$370 ksec deep survey obtained with XMM-Newton on the Chandra Deep Field South (CDFS). Using sample of 127 sources with redshift identifications and with a raw count limit of 100 (pn detector) we explored both the physical properties of individual sources, and the general properties of two AGN classes. The corresponding flux limits in the (0.5–2) and (2–10) keV bands are 1 $\times 10^{-16}$ and 9 $\times 10^{-16}$ erg cm$^{-2}$ s$^{-1}$, respectively. The average photon index is $\Gamma \sim$1.9 and $\Gamma \sim$1.8 for type-1 AGN and type-2 AGN, respectively. Although the properties of the spectra of more that 90% of AGN are in good agreement with the unified model, a fraction of ‘atypical’ objects (absorbed type-1 and unabsorbed type-2 AGN) was detected.

We present recent results on the carbon chemistry in photodissociation regions. We show that carbon chains and rings (CCH, c-C$_3$H$_2$ and C$_4$H) are tightly spatially correlated with each other, and with the mid-infrared emission due to PAHs (7 and 15 $\mu$m), mapped by ISOCAM. Neither the spatial distribution, nor the abundances of these species can be fit by state-of-the-art PDR models, which calls for another production mechanism. We discuss model predictions for carbon clusters and simple hydrocarbons. We show how selected abundance ratios can be used as a diagnostic of the physical conditions. We stress the need for more theoretical and laboratory work on fundamental processes relevant for the interstellar medium, which should be taken into account in the astrochemical models, but whose rates are not known accurately enough.

The results obtained during the first three years of operation of INTEGRAL will be reviewed. Over 30 GRBs have been localised by the INTEGRAL burst alert system (IBAS) and the coordinates distributed. The follow-up observations with XMM-Newton and large telescopes have led to many interesting results. A comparison will also be made between the sensitivities of INTEGRAL and SWIFT.

The IAU Symposium 230, Populations of High Energy X-ray Sources in Galaxies has been a wide-spectrum affair, with talks discussing results from the soft X-ray to the Gamma-ray range on virtually the entire universe, from our Galaxy to the high redshift regions when first galaxies emerged. I do not name any presenter in this summary, but concentrate on themes and results that I have found striking.

I review recent progress in determining the rate coefficients appropriate to modelling interstellar chemistry, give some information on appropriate databases from which rate coefficients can be obtained, and point to the importance of the gas-grain interaction in determining molecular abundances. Although many of the fundamental gas-phase reactions have been studied in the laboratory, the failure of the models to explain the observations of water and methanol in cold clouds indicates that grains may have an important role, both in acting as a surface for freeze-out and in the synthesis of complex molecules. The major challenge in astrochemistry is to develop a more quantitative model for the role of grains and, in some cases, to incorporate a better, probably more complex, physical model for interstellar clouds.

Owing to the rapid progress of space sciences and the high-energy astrophysics in the past 2–3 decades, historical supernova records have made important contributions to modern astrophysics and will continue to do so in the future. The main topics here are the earliest supernova observed by human beings and the AD393 guest star as well as our new concept of “Po stars”

Chandra observations have allowed the detection of a large number of low mass X-ray binaries (LMXBs) in early-type galaxies. Comparison to catalogs of globular clusters (GCs) from Hubble Space Telescope observations have shown that a high fraction of the LMXBs in early-type galaxies are associated with GCs. The fraction of LMXBs associated with globular clusters increases along the Hubble sequence from spiral bulges to S0s to Es to cDs. On the other hand, the fraction of globular clusters which contain X-ray sources appears to be roughly constant ($\sim$4% for $L_X \gtrsim 10^{38}$ ergs/s, $\sim$10% for $L_X \gtrsim 10^{37}$ ergs/s). There is a strong tendency for the X-ray sources to be associated with the optically more luminous GCs. There is a trend for the X-ray sources to be found preferentially in redder, more metal-rich GCs, which is independent of optical luminosity correlation.

The relative role of formation of LMXBs in GCs and in situ formation in the field is uncertain. One of the best ways to study this is to compare the spatial distribution of GC-LMXBs, field LMXBs, GCs, and optical light in the galaxies. Theoretical models and results of fits to the observed distributions are presented.

We explore the X-ray diagnostics of cosmic star formation history that have possible form recent deep field X-ray studies. We summarize the status of our understanding of the X-ray evolution of galaxies. We indicate the lessons learnt so far from number count plots, and criteria for distinguishing between normal/straburst galaxies and AGNs in deep X-ray surveys. We summarize how the observed correlations between X-ray emission and that at other wavebands indicate the value of X-rays as a probe of cosmic star formation.

HD34921 has been identified as the counterpart of the X-ray source 4U0515+38 (=1H0521+373). The InfraRed properties are reminiscent of the B[e] system CI Cam. Optical short-term variability suggests a compact companion. We discuss how this system fits in the overall framework of Be stars and X-ray binaries.

We present new experimental data and review previous experimental results on molecular hydrogen formation from atomic recombination on porous amorphous solid water (ASW) surfaces at temperatures from 10 K to 30 K, i.e. under conditions of relevance to cold dense interstellar clouds. We show that the desorption of molecular hydrogen formed on porous ASW surfaces is well described by a model, in which the molecules are assumed to be completely thermalized to the surface temperature and to be evenly distributed throughout the porous network of the ASW films. These results emphasize that, not only the chemical properties, but also the physical morphology of dust grain surfaces must be considered to obtain a full understanding of molecular hydrogen formation on interstellar dust grain surfaces.

Although our Galactic Center harbors a black hole (Sgr A*) of a few million solar masses, it and its environments are very quiet at present. In X-rays however, the close vicinity of Sgr A* shows very unique and various phenomena mostly originated from young stellar populations. We report on the X-ray perspective on the young stellar populations which are related to our Galactic Center activities. The discussion is essentially based on the observational facts of new X-ray objects in the Galactic Center region in the $1^\circ \times 2^\circ $ area. They are;

1. Clusters of young high mass stars, which are Sgr B2, Arches, IRS 13 and Quintuplet.

2. X-ray reflections in the giant molecular clouds, such as Sgr B2, Sgr C, M0.01-0.09 and others.

3. New candidates of X-ray supernova remnants (SNRs), which are Sgr A East, G0.570-0.018 and G359.8-0.3.

4. Non-thermal Jets, Filaments and Shells, which are unique X-ray features in the GC region. These X-ray features may be closely related with each other, hence may have common origins. A unified picture is presented for the X-ray activity of our Galactic Center comparing with the X-ray spectra from other type of galaxies such as;

5. Star burst galaxy (NGC 253), low luminosity AGN (M 81) and Seyfert 2 (NGC 1068).

The particle acceleration and the non-thermal radiation in the magnetospheres of collapsing stars are considered. The collapsing stars can be powerful sources of the high-energy charged particles and the non-thermal radiation bursts. These bursts can be observed by means of modern astronomical instruments.

It is discovered that young SNRs have very thin filaments emitting nonthermal X-rays from accelerated electrons. In this paper, a new age and distance indicator is proposed using the spectral and spatial features of nonthermal filaments. We applied this method to the Vela Jr. SNR, for which age and distance are still unknown, and estimated that this SNR is one of the nearest and youngest SNR in our Galaxy: the estimated distance and age are 0.33 (0.26–0.50) kpc and 660 (420–1400) years, respectively.

We report the serendipitous discovery of several ULX candidates in XMM-Newton observations. Such discoveries suggest that ULXs are not a negligible component of the extragalactic X-ray source population.