The achievable contrast level for space-based detection of exo-planets will be limited by the stability of the optics. As a consequence, active amplitude and phase compensation will be needed. High order aberrations can arise from both non linearity and Fresnel propagation, their wavelength dependence is studied here and it is concluded that $\lambda$ independent errors are dominant. The behavior of a Michelson interferometer equipped with two deformable mirrors under chromatic light is then presented, and an achromatization method based on a dispersive element is suggested.

The 100 m OWL ESO Concept Study has undergone a full review early November 2005. The development of the concept, the conclusions of the review panel and the planned post-review actions for the European Extremely Large Telescope (ELT) to be built by ESO in the next 10 years are presented and discussed.

We present Surface Brightness Fluctuation (SBF) distances of fifteen early-type dwarf galaxies and the S0 galaxy NGC 4150 in the Local Volume based on deep $B$- and $R$-band CCD images obtained with the 2.56 metre Nordic Optical Telescope (NOT). Distances have been determined from Fourier analysed fields selected from optimal locations on the galaxies. Distances were found to range from 3 to 16 Mpc.

The SBF method has been demonstrated to efficiently measure relatively accurate distances from the ground with mid-aperture telescopes. The SBF method to measure distances to dwarf elliptical (dE) galaxies has also been empirically calibrated using three dEs with known tip of the red giant branch (TRGB) distances.

The supernova explosion of 1054 AD, which originated the Crab Nebula and Pulsar, is probably the astronomical event which has been most deeply studied by means of historical sources. However, many mysteries and inconsistencies, both among the different sources and between what is deduced by the historical records and the present day astronomical data, are demanding extraordinary efforts by theoretical astrophysicists in order to put all the data in a meaningful framework. An accurate analysis of the historical sources, like the one we are presenting here, may contribute to solve some of these problems.

We present procedures and preliminary results from a study on the effects of instrumental polarization on the fine structure of the stellar point spread function (PSF). These effects are important to understand because the the aberration caused by instrumental polarization on an otherwise diffraction-limited will likely have have severe consequences for extreme high contrast imaging systems such as NASA's planned Terrestrial Planet Finder (TPF) mission and the proposed NASA Eclipse mission. The report here, describing our efforts to examine these effects, includes two parts: 1) a numerical analysis of the effect of metallic reflection, with some polarization-specific retardation, on a spherical wavefront; 2) an experimental approach for observing this effect, along with some preliminary laboratory results. While the experimental phase of this study requires more fine-tuning to produce meaningful results, the numerical analysis indicates that the inclusion of polarization-specific phase effects (retardation) results in a point spread function (PSF) aberration more severe than the amplitude (reflectivity) effects previously recorded in the literature.

Core collapse supernovae are responsible for at least half of the galactic inventory of Fe-group elements and probably for most of the Fe-group abundances seen in metal poor stars. Recent simulations show the emergence of a proton-rich ($Y_e>0.5$) region in the innermost ejected mass zones due to the neutrino interaction with matter. We explore the nucleosynthesis implications of these findings that result in enhanced abundances of 45Sc, 49Ti, and 64Zn, which is consistent with chemical evolution studies and observations of low metallicity stars.

In this work, observational evidence for the connection between low column density Lyman-$\alpha$ absorbers and large-scale structure traced by gas-rich galaxies is investigated. The H I Parkes All Sky Survey (HIPASS) galaxy catalogue is cross-correlated with known low redshift, low column density ($N_{\rm HI}<10^{15}$ cm$^{-2}$) Lyman-$\alpha$ absorbers from the literature. The absorber-galaxy cross-correlation function shows that on scales from 1–10 h$^{-1}$ Mpc, absorbers are embedded in halos with masses similar to that of galaxy groups.

We provide new nucleosynthesis yields depending on metallicity and energy (i.e., (normal supernovae and hypernovae), and show the evolution of heavy element abundances from C to Zn in the solar neighborhood. We then show the chemodynamical simulation of the Milky Way Galaxy and discuss the G-dwarf problem. We finally show the cosmological simulation and discuss the galaxy formation and chemical enrichment.

For a European ELT, we discuss science requirements and technical options. Science includes from the solar system to the first stars and galaxies. ELT and instrument needs are commented. Design options are discussed for the primary mirror, its segmentation and shape, and an adaptive secondary mirror. Adaptive optics and enclosure are commented.

Dwarf galaxies are the most numerous type of galaxy in the local universe and are extremely important in the understanding of galaxy formation and evolution. A better understanding of the physics of dwarf galaxies is central to several current issues in observational cosmology. For example, simulations of galaxy evolution based on the Cold-Dark-Matter (CDM) model predict far more dwarfs than are observed locally. In the last 20 years there has been a huge amount of interest in the study of dwarf galaxies, partly due to these unanswered puzzles and also because of the improvements in the technology available.

In this laboratory experiment, we study the possibility of producing an apodization of the pupil of a telescope using a classical Michelson interferometer. To simulate the star, we successively used a Laser source, a source of spectral light and a source of white light. Our goal is to study the performance of the assembly with polychromatic light. We present the results of experiments carried out with a rectangular aperture using a HeNe Laser and Na spectral light sources.

We have collected from the literature X-ray fluxes of Young Supernovae, measured with various instruments. After converting the data to one energy range, we have compared the X-ray light curves of these objects. The X-ray luminosities of early Supernovae show coherent trends with Supernova type and provide significant, though short-lived contributions to the X-ray luminosity of Starbursts.

We present preliminary results from the Hamburg/ESO survey for damped Ly-$\alpha$ (hereafter, DLA) systems. This survey is characterised by (i) good knowledge of the biases affecting the parent QSO survey, and (ii) the brightness and (iii) relatively wide magnitude distribution of the background QSOs. Therefore, it is well–suited to study possible magnitude–dependent biases in DLA surveys, such as the one expected from dust obscuration.

We have systematically searched for damped Lyman-$\alpha$ line candidates in 5 Å, resolution spectra of the 188 QSOs that constitute our statistical sample. These candidates have later been re-observed with UVES at the ESO–Very Large Telescope (VLT) for confirmation and accurate $N(HI)$ measurements. In the redshift range covered by the survey, 19 DLA systems have been discovered. Over the whole survey, we find that the number density $n(z)$ and cosmological density of gas $\Omega_\mathrm{gas}$ have comparable values to the ones obtained by CORALS (Ellison et al. 2001).

However, the number densities of DLA systems $n(z)$ in two sub–samples of equal absorption distance path defined by the magnitude of the background QSOs differ by a factor of $\approx 5$. We estimate that the probability that $n(z)$ is equal in the two sub–samples is $<0.003$. A similar, only slightly less significant difference is found for $\Omega_\mathrm{gas}$.

We review the need for technology developments to meet the science cases that have been assembled for optical and infrared telescopes from 20 to 100 metres. Novel technologies can make an impact on the scientific capabilities of these ELTs, make them more affordable and decrease the operating costs. We consider those technologies highlighted by design studies and technology roadmapping exercises on both sides of the Atlantic, with particular emphasis on instrumentation. We do not consider adaptive optics (AO), which is covered by Ellerbroek & Hubin (this volume). Finally, we recommend a joint technology development programme to enable a world-wide suite of ELTs to be built.

Three-dimensional common-path interferometer is proposed to obtain achromatic nulling for the on-axial source; the off-axial source remains detectable. The 3D interferometer involves $\pm 90^{\circ }$ polarization rotations in each interferometer arm. That results in the achromatic 180$^{\circ}$ phase shift, so that the on-axial source interferes destructively. Depending on the source axial position, the light energy is split by different ratios between the Bright and the Nulled interferometer outputs. For the linearly polarized on-axial source, all the energy at nearly 100% is directed to the Bright port. For the off-axial source, the light is split by the ratio at nearly 50%/50% between the Bright and the Nulled ports. The common-path scheme compensates effectively the optical path difference (OPD) and it remains stable to mechanical vibrations. Theory, simulations and preliminary breadboard experiments are shown to be in reasonable agreement.

We investigate the variations in the broadband luminosities of low and intermediate redshift galaxies due to the stochastic nature of the neutral hydrogen distribution present in the form of Ly$\alpha$ absorbers in the intergalactic medium. This effect is caused by variations in the distribution and properties (redshift, column density, Doppler parameter) of the absorbers along different lines-of-sight out to a given redshift. Using a set of observationally constrained redshift-, column density-, and Doppler parameter distributions we perform Monte Carlo simulations for a large number of lines-of-sight towards galaxies at a given redshift $z_{em}$ and calculate attenuated FUV/NUV magnitudes and corresponding 1-, 2-, and 3$\sigma$ variations. We predict significant variations in luminosity ranging from -0.22 to +0.48 magnitudes at the 1$\sigma$level for galaxies at$z=1.5$inGALEXdata.

PN G 135.9 +55.9 is an extraordinary nebula discovered recently in the Galactic halo (Tovmassian et al. 2001). The first studies estimated its oxygen abundance to be 1/100 of the solar value or even less.

Being extremely metal-poor, PNG 135.9+55.9 offers an unprecedented opportunity to check our understanding of the evolution of intermediate-mass stars at very low metallicity, by complementing the data obtained from metal-poor giants (Spite et al 2005). Indeed, PNG 135.9+55.9 and some of those stars are snapshots of the evolution of very similar stars at different times.

We present our most recent abundance analysis for this object, providing stringent limits on the abundances of C, N, O, and Ne, to be confronted with the predictions for the yields of low metallicity intermediate mass stars.

ULXs have been studied for 20 years, but only recently have detailed X-ray spectral/timing studies, and investigations of their statistical properties and their environments and counterparts been undertaken. I will review progress in these areas.

The structural properties of a sample of 50 dEs in the Virgo cluster are here derived from Near InfraRed (NIR, H-band 1.65 $\mu$m) surface photometry and analysed. One-dimensional surface brightness (SB) profiles are extracted using elliptical isophote fitting. They are characterised by means of structural parameters, namely the half light radius $R_e$, the average surface brightness within $R_e$ ($\mu_e$), and a concentration index ($c_{31}$). We show that typical dEs have close-to-exponential NIR SB distributions.

The relations between dEs and giant ellipticals (Es) are investigated by comparing the NIR structural parameters of 273 Es in nearby clusters. Further analysis is conducted using the optical-NIR colour $B-H$ and by studying the relationships between structural and dynamical parameters (fundamental plane) for the two classes of galaxies. The transition between the two regimes is smooth and no dichotomy is seen.

With the information era in astronomy coming, this “data avalanche” may provide many answers to important problems in contemporary astrophysics. The most important problem is sifting through massive amounts of data to mine knowledge. In this paper, we positionally cross-identify multi-wavelength data from optical, near-infrared, and X-ray bands, and then employ Alternating Decision Trees (ADTree) to quickly and robustly separate AGN candidates to a high degree of accuracy. We emphasise the application of the method due to the development of large survey projects and the establishment of the virtual observatory, and conclude that the application of data mining algorithms in astronomy is of great importance to discover new knowledge impossible to obtain before, and promote the development of astronomy.