We confront predictions of the currently popular theories for dE formation and evolution with the observed position of dEs in $\log L_B$ vs. $\log \sigma$, $\log L_B$ vs. $\log R_{\rm e}$, $\log L_B$ vs. $\log I_{\rm e}$, and $\log R_{\rm e}$ vs. $\log I_{\rm e}$ diagrams and in the ($\log \sigma,\log R_{\rm e},\log I_{\rm e}$) parameter space in which bright and intermediate-luminosity elliptical galaxies and bulges of spirals define a Fundamental Plane (FP). We show that the dE sequences in the various univariate diagrams are disjunct from those traced by bright and intermediate-luminosity elliptical galaxies and bulges of spirals. It appears that semi-analytical models (SAMs) that incorporate quiescent star formation with an essentially $z$-independent star-formation efficiency, combined with post-merger starbursts and the dynamical response after supernova-driven gas-loss, are able to reproduce the position of the dEs in the various univariate and bivariate diagrams.

The status of Very High Energy (VHE, E$\,{>}\,$50 GeV) gamma-ray observations of BL Lacertae objects is presented. The catalogue of well-established BL Lacertae objects detected at VHE energies contains seven members, and there have been recent reports of the detection of another four. All are nearby, X-ray bright sources. The temporal, spectral and broadband multi-wavelength properties of the sources are reviewed and possible implications for the gamma-ray production mechanism discussed. The most recent detections provide more stringent constraints on the cosmic extragalactic background light level and imply that the Universe is more transparent to VHE gamma radiation than previously thought.

The UVES Paranal Observatory Project (POP), is an ESO public database of about 400 stars whose high quality spectra were obtained with UVES, the high resolution spectrometer of the VLT. All stars were observed with two instrument modes, in order to cover almost completely the optical region (300–1000 nm). The resolving power is about 80000, and for most of the spectra, the typical S/N ratio is 300–500 in the V band. Program stars fall into two groups, stars belonging to open clusters IC2391 and NGC6475, and bright field stars. For field stars, the only selection criterion applied was to cover the largest possible variety of spectral types in the HR diagram, including peculiar objects, e.g., Ap and Bp stars, Wolf-Rayet stars, Be stars, carbon stars and metal poor stars. The spectra have been reduced, coadded and merged and various products can be downloaded from a public area. For each star the final spectrum may be displayed through a dedicated user-friendly Spectral Preview Interface. The database is accessible at http://www.eso.org/uvespop

This paper summarizes the general theory and properties for Apodized Pupil Lyot Coronagraphs which consist of a classical hard-edged Lyot coronagraph with an upstream pupil apodization. The ideal apodization function can be determined from an integral eigenvalue problem which solutions are prolate spheroidal functions. Solutions exist for any geometrty, including rectangular, circular, or elliptical. Formal solutions can be extended to the case of arbitrary apertures, using generalized prolate spheroidal functions for centrally obstructed apertures, spiders, or segmented telescopes. The properties of these coronagraphs enable the possibility of multiple stage coronagraphy and achromatization. The new instrument Gemini Planet Imager (GPI) will include such a coronagraph.

Despite recent advances in the study of extra-solar planets the detection of reflected light from planetary atmospheres remains a major goal. For the so-called hot-Jupiters, which are unlikely to be spatially resolved from the central star in the foreseeable future, very high sensitivity measurements are required to detect the reflected signal from the very much larger direct starlight. We describe an optical photo-polarimeter designed to have a polarization sensitivity of at least 1 in $10^6$ and some early observations made in an attempt to detect the polarization signature of $\tau$ Boo b. We discuss the role of such an instrument for the planned ELTs.

The Surface Brightness Fluctuation method has been shown to be a powerful distance indicator for dwarf elliptical galaxies to very low surface brightness levels. It is applicable to stellar systems that are out of reach for classical indicators requiring resolved stellar populations such as the tip magnitude of the red giant branch. I briefly discuss a few results from recent SBF studies of dEs to demonstrate the significance of the SBF method to address longstanding issues related to cosmography, dark matter in galaxy groups, substructures in clusters, and the discrepancy between the mass function of collapsed objects and the faint end of the galaxy luminosity function. For the analysis of the large number of galaxy images that need to be processed as part of such SBF studies we are currently developing a fast, semi-automatic reduction pipeline that will be made readily available to the astronomical community.

We used our database of ESO VLT-UVES spectra of quasars to build up a sample of 67 damped Lyman-$\alpha$ (DLA) systems with redshifts $1.7<z_{\rm abs}<3.7$. For each system, we measured average metallicities relative to Solar, [X/H] (with either ${\rm X}={\rm Zn}$, S, or Si), and the velocity widths of low-ionisation line profiles, $W_{1}$. We find that there is a tight correlation between the two quantities, detected at the $5\sigma$ significance level. The existence of such a correlation, over more than two orders of magnitude spread in metallicity, is likely to be the consequence of an underlying mass-metallicity relation for the galaxies responsible for DLA absorption lines. The best-fit linear relation is $[{\rm X}/{\rm H}]=(91.35\pm 0.11)\log W_{1} -(3.69\pm 0.18)$ with $W_{1}$ expressed in km s$^{-1}$. While the slope of this velocity-metallicity relation is the same within uncertainties between the higher and the lower redshift bins of our sample, there is a hint of an increase in the intercept point of the relation with decreasing redshift. This suggests that galaxy halos of a given mass tend to become more metal-rich with time. Moreover, the slope of this relation is consistent with that of the luminosity-metallicity relation for local galaxies. The DLA systems having the lowest metallicities among the DLA population would therefore, on average, correspond to the galaxies having the lowest masses. In turn, these galaxies should have the lowest luminosities among the DLA galaxy population. This may explain the recent result that the few DLA systems with detected Ly$\alpha$ emission have higher than average metallicities.

For refining cosmochemical studies, we are investigating the statistical equilibrium (non-LTE) of neutral and singly-ionized calcium (CaI/II) in the atmospheres of solar-type stars. The envisioned applications are a) detailed abundance studies beyond classical models, b) using CaI/II as a gravity indicator for ultra-metal-poor (UMP) stars and c) detailed modelling of the CaII IR triplet lines for the astrophysical parametrization of the Gaia mission. We present first results for some well-studied reference cases, both at solar and low metallicity.

Active Galactic Nuclei emit a substantial portion of their bolometric luminosities in X-rays. For example, the knots in radio jets are prominent sources of synchrotron X-rays while the hotspots of the brightest FRIIs emit self-synchrotron or Inverse Compton radiation. Most high-energy studies on flat-spectrum radio sources have been conducted for blazars which are dominant at $\gamma$-rays.

Augusto et al. (1998) have built a sample of 55 flat-spectrum radio sources dominated by structures (knots, hotspots, etc.) $\sim$0.1–2 kpc away from the nucleus. Seventeen (31%) of these are detected in X-rays (they tend to be the radio strongest) evenly splitting, morphologically, both at optical (radio) bands: nine QSO/BLLac (core-jets) on one-side; eight Galaxy/Sy2 (CSO/MSO/FRII) on the other. We have identified five confirmed compact/medium symmetric objects (CSO/MSOs) as X-ray emitters. A comparable type of source to CSO/MSOs is the physically similar (1–15 kpc) compact steep spectrum source (CSS), 28/129 (22%) of which are detected in X-rays, from a literature-selected sample (the percentage is smaller than for the 55-source sample due to a lower $<\!\!S_{4.85}\!\!>$). A 95% conf. level relation is found for CSSs: $S_X \propto (S_{4.85})^{0.6}$ and we found undistinguishable radio/X-ray properties for both the 55-source and CSS samples: clearly, their similar morphologies (e.g. knots in jets) stand up stronger than their radical radio spectrum differences.

Only two sources among the 55 (4%) have $\gamma$-ray detections and they seem quite abnormal (in $\alpha_{x\gamma}$ values, at least)–one of them is in a Sy2, not in a blazar.

The evidence is becoming strong that the luminosity function of galaxies varies with environment. Higher density, more dynamically evolved regions appear to have more dwarfs per giant. The situation is becoming clearer as a result of wide field imaging surveys with the Canada-France-Hawaii and Subaru telescopes and spectroscopy of faint dwarfs with the Keck telescope. We report here on extensive observations of the small but dense NGC 5846 Group. The faint end of the luminosity function rises relatively steeply in this case.

We employ a new Infrared Flux Method (IRFM) temperature scale (Ramírez & Meléndez 2005a, b) in order to determine Li, O, and Fe NLTE abundances in a sample of relatively unevolved (dwarfs, turn-off, subgiants) metal-poor stars. We show that the analysis of the permitted OI triplet and FeII lines leads to a plateau in [OI/FeII] over the broad metallicity range $-3.2 <$ [Fe/H] $<-$0.7, independent of temperature and metallicity, and with a star-to-star scatter of only 0.1 dex. The Li abundance in halo stars is also found to be independent of temperature and metallicity (Spite plateau), with a star-to-star scatter of just 0.06 dex over the metallicity range $-3.4 <$ [Fe/H] $<-1$. Our Li abundance (Meléndez & Ramírez 2004) is higher than previously reported values, but still lower than the primordial abundance suggested by WMAP data and BBN.

We have used Chandra archival observations of 19 galaxies hosting LINERs to explore the morphology and source population of their inner kiloparsec. Our goal was, in general, to determine the power source behind their nuclear X-ray emission and, in particular, to investigate the presence of an AGN. We find an AGN in 12 of the 19 galaxies in the sample. We also find that diffuse, thermal emission is common with properties very similar to what is found in normal galaxies. In 10 out of the 19 galaxies, the diffuce emission dominates the nuclear X-ray power. The X-ray point-source populations were studied by producing cumulative luminosity functions and their properties are also similar to what is found in normal galaxies.

Direct detection of exoplanets is a topic of increasing interest since the first exoplanet discovery by indirect methods. It represents a formidable task because of the small angular separation and large contrast ratio between planet and parent star. We present a novel family of stellar coronagraphs based on the standard coronagraph design but transformed to perform optical differentiation. The proposed coronagraphic masks are used to perform the first or the second derivative of the incoming field. This concept offers a new method to detect exoplanets providing both, deep starlight extinction and high angular resolution. To perform optical differentiation the coronagraph's occulting disk is replaced by an especially designed mask. A further improvement on the coronagraph performance is made by adding a gaussian profile to the differentiation mask in order to reduce the amount of diffracted light. The theoretical rejection rate of our coronagraph is infinite. Computer simulations carried out for the ideal case show that it achieves deep starlight reduction corresponding to a gain of at least 37 mag ($10^{-15}$ light intensity reduction). To take full advantage of the capabilities of our coronagraph atmospheric distortions must be reduced by the use of extreme adaptive optics systems or by its use on space telescopes.

Cool, extrasolar gas giants similar to Jupiter and Saturn in our own Solar System should be detectable by virtue of the light they reflect in the optical and near-infrared with the next generation of Extremely Large Telescopes (ELTs) equipped with adaptive optics systems. Broad band imaging or very low-resolution spectra should then enable the characterization of the orbit, mass, atmospheric scattering properties, and presence of large rings in these gas giant analogues.

We report the current results of our on-going search for molecular hydrogen (H$_2$) in damped Lyman-$\alpha$ (DLA) and sub-DLA systems at $1.8<z_{\rm abs}<3.4$ using the Ultraviolet and Visible Echelle Spectrograph (UVES) installed at the ESO's Very Large Telescope (VLT), Unit Kueyen.

The starlight coming from the intergalactic space in galaxy clusters and groups witnesses the violent tidal interactions that galaxies experience in these dense environments. Such interactions may be (at least partly) responsible for the transformation of normal star-forming galaxies into passive dwarf ellipticals (dEs).

In this contribution we present the first systematic study of the IntraCluster Light (ICL) for a statistically representative sample (Zibetti et al. 2005), which comprises 683 clusters selected between $z=0.2$ and 0.3 from ${\sim}1500 \deg^2$ in the SDSS. Their ICL is studied by stacking the images in the $g$-, $r$-, and $i$-band after masking out all galaxies and polluting sources. In this way a very uniform background illumination is obtained, that allows us to measure surface brightnesses as faint as 31 mag arcsec$^{-2}$ and to trace the ICL out to 700 kpc from the central galaxy. We find that the local fraction of light contributed by intracluster stars rapidly decreases as a function of the clustercentric distance, from $\sim$40% at 100 kpc to $\sim$5% at 500 kpc. By comparing the distribution and colours of the ICL and of the clusters galaxies, we find indication that the main source of ICL are the stars stripped from galaxies that plunge deeply into the cluster potential well along radial orbits. Thus, if dEs are the remnants of these stripped progenitors we should expect similar radial orbital anisotropies and correlations between the dE luminosity function and the amount of ICL in different clusters.

The diffuse emission we measure is contaminated by faint unresolved galaxies: this makes our flux estimate depend to some extent on the assumed luminosity function, but, on the other hand, allows us to constrain the number of faint galaxies. Our present results disfavour steep ($\alpha<-1.35$) faint-end powerlaw slopes.

A new approach to high contrast observations near bright stars with a single-aperture telescope is discussed, which is based on the idea of a rotating separated-aperture nulling interferometer. The approach can be described as a rotating sub-aperture nuller, because it nulls two or more sub-apertures within a single telescope's pupil, and uses baseline rotation to modulate the signals from off-axis sources in a manner similar to that of potential space-based nulling interferometers. The sub-aperture beams can be combined in a number of ways, including a fiber nuller and a rotational shearing interferometer. Such a rotating nulling coronagraph has two great advantages. First, it can be used on a ground-based telescope to test signal reconstruction approaches pertinent to potential space-based nulling interferometers. Moreover, it also has the potential to enable ground-based coronagraphic observations of faint off-axis companions very close to bright stars.

Various projects to find planets or entire planetary systems around main sequence stars in the solar neighborhood are presently under way. When ELTs will be operational, there will be literally thousands of confirmed planetary systems including spectro-photometric detections. At this point it becomes inevitable to consider the next logical step: the spectroscopic analysis of the atmospheres of these planets. High-resolution spectroscopy, i.e. resolving $v \times \sin (i)$ of these planets, in the wavelength regime of 950-5500nm is a powerful and promising tool. In view of the obvious contrast problems in detecting such planets non-LTE features are specifically targeted. Sensitivity estimates for the detection of the non-thermal OH glow in oxygen-bearing atmospheres are given. With 8m-class telescopes such a search is impossible, but a dedicated spectrograph, e.g. at the projected ESO 100m OWL telescope could detect Earth-like planets at a distance of ${\approx} 10$ parsec. A conceptual design for a dedicated spectrograph, NOCTUA, is presented. In case of ELTs of smaller size the science case changes and the instrument requirements have to be adjusted. Preparatory work with CRIRES, ESO's Cryogenic Infrared Echelle Spectrograph on the VLT at $\frac{\lambda}{\Delta \lambda} \approx 10^5$ as well as other science cases are shortly discussed.

We have determined the chemical composition of the carbon dwarf G77-61, from Keck IR and optical spectra. We present here a new analysis with the oxygen abundance measured for the first time. We show that G77-61 is extremely metal-poor ([Fe/H]$\,{=}\,{-}$4), with large overabundances of C, N and O ([C/Fe] = 3.2, [N/Fe] = 2.2, [O/Fe] = 2.2). It also shows moderate enhancements of Ca and Mg, Na, and Cr of typically 0.5 dex relative to Fe. We discuss the possible origin of these peculiarities.

We refer on analysis of the ESA INTEGRAL satellite data for blazars, promising sources to be observed during their active states. We further refer on searches for and analysis of supermassive binary black holes requiring very long time intervals (50 years and more) provided by digitised astronomical plates.