We report the results obtained from optical and near-infrared spectroscopy and also broad-band photometry of lensed low-luminosity galaxies ($1.3\leq z\leq 2.3$) located in the core of lensing clusters. The amplification factor allowed us to obtain the physical properties (SFR, abundance ratios, mass, age of the burst, dust contents, etc.) of star-forming galaxies, 1 to 2 magnitudes fainter than galaxies in a blank field, using the same indicators as in studies of low-redshift galaxies. A part of this study was concentrated on the dynamics of distant lensed galaxies using Integral Field Spectroscopy (SINFONI/VLT science verification programme).

The Sun has typical abundances of both oxygen and sulphur for its metallicity, age and galactic orbit, when compared to the nearby solar-type stars. This result favors a solution of the old riddle of the solar overabundance in oxygen with respect to the local interstellar medium as caused by the recent infall of metal-poor gas over the disk, rather than the competing explanations of an outward migration of the Sun from a inner, and metal richer, birthplace in the disk, or a last-minute supernova which might have enriched the proto-solar nebula.

Until very recently, our knowledge of the local peculiar velocity field has been severely hampered by the lack of reliable distance measurements. HST has dramatically changed this situation, allowing astronomers to obtain accurate distances to more than 150 nearby galaxies. This number could easily reach 400 if enough observing time would be dedicated to snapshot observation of the objects in the catalog of Karachentsev et al (2004). Such a dense grid of objects correctly placed in their 3D position would provide key information on the amplitude of peculiar motions, the radial domain of bound groups, the clustering and morphological segregation properties of galaxies, and the incidence of extreme dwarfs galaxies. The key instrument to measure distances with HST is the Tip of the Red Giant Branch technique. The full exploitation of this powerful distance estimator requires a deeper understanding of the possible sources of errors and biases, such as the absolute calibration of the I-band magnitude of the tip and its dependency on age and metallicity of the underlying population, the possible contamination by AGB stars, the breakdown of the methodology in sparsely populated colour-magnitude diagrams and when the tip is close to the photometric limit.

A sample of distant ($z>0.4$) luminous infrared galaxies (LIRGs) selected from ISOCAM deep survey fields (CFRS, UDSR, UDSF) have been studied on the basis of their high-quality optical spectra from VLT/FORS2 (R=5Å). Robust estimates of dust extinction can be considered via the energy balance between the infrared and H$\beta$ luminosities, after correcting the underlying Balmer absorption properly. Oxygen abundances [12+log(O/H)] in the interstellar medium of the sample galaxies estimated from the “strong-line” method show a range from 8.36 to 8.93, with a median value of 8.67, which is 0.5 lower than that of local bright disks (i.e. $L^*$) at the given magnitude. The timescale to double the stellar masses of such LIRGs can be very short, 0.1-1 Gyr. A significant fraction of distant large disks are indeed LIRGs. Such massive disks could have formed $\sim50$% of their metals and stellar masses since $z\sim1$.

The Phase-Induced Amplitude Coronagraph (PIAAC) uses a lossless beam apodization, performed by aspheric mirrors, to produce a high contrast PSF. Thanks to the lossless apodization, this concept offers a unique combination of high theoretical throughput ($\approx$100%), high angular resolution ($\lambda/d$), small inner working angle (${\approx} 1.5 \lambda/d$), low chromaticity and low sensitivity to pointing errors or angular star diameter. Together, these characteristics make the PRC an ideal choice for direct imaging of extrasolar terrestrial planets (ETPs) from space. We show that a visible telescope smaller than 4m would then achieve the goals of the TPF mission, while other coronagraphs considered for TPF require telescope diameters typically 2 to 3 times larger. On a large size (8m) space telescope, ETPs can be searched for around a significantly larger sample of stars, thus enabling a much higher scientific return.

Low-frequency ($f \leq 10^{-6}$ Hz) quasi-periodic variability observed from radioloud, jet-emitting Active Galactic Nuclei (AGNs) can provide substantial inductive support for the presence of close ($d \lesssim 0.1$ pc) supermassive binary black holes in their centers. Such periodic variability may arise, for example, due to differential Doppler boosting along helical jet paths driven by the orbital motion or jet precession. If the jet path is non-ballistic, travel time effects can lead to a strong reduction of the observable period by up to a factor of $\gamma_b^{-2}$. Here we suggest a binary model where the optical periodicity with timescale of several years is related to accretion disk interactions, radio periodicity to Newtonian jet precession and periodicities in the high energy bands to the orbital motion of the jet. We analyze the explanatory potential of such a framework and comment on the possible origin of periodicities in AO 0235+16.

The extreme contrast in mass and luminosity between the extra-solar planets and their host stars make detailed studies of these planets very challenging. In particular, direct observations of extra-solar planets is still beyond the capabilities of the currently available instrumentation, save for perhaps a few extreme cases of very young and massive planets at large distances from the central star. While progress in instrumentation might allow significant progress in detection capabilities either with the 8 and 10-m ground-based telescopes (Planet Finder instruments on the VLT and Gemini) or with the next generation space telescope (JWST), imaging of extra-solar planets over a wide range of parameters, and possibly down to terrestrial planets, will require extremely large ground-based telescopes like OWL or dedicated space instrumentation (TPF or Darwin for instance). We outline here the scientific objectives of EPICS, the OWL Earth-like Planet Imager and Spectrograph, summarize the corresponding high level requirements, present the foreseen observing modes and give a first estimate of its performance.

Brown dwarfs and very low-mass stars are likely to harbour planetary systems with rocky planets. We discuss the possibility of detecting them using accurate radial velocity measurements with a cross-dispersed high-resolution spectrograph coupled to a ground-based extremely large telescope.

We analyze the Luminosity Functions (LFs) of a subsample of 69 clusters from the RASS-SDSS galaxy cluster catalog. The cluster LFs are computed within the physical sizes of the galaxy systems, $r_{500}$ and $r_{200}$. When calculated within the cluster physical sizes, all the cluster LFs appear to have the same shape, well fitted by a composite of two Schechter functions with a marked upturn and a steepening at the faint-end.

We determine the composite LF for early- and late-type galaxies, where the typing is based on the galaxy $u-r$ colors. The late-type LF is well fitted by a single Schechter function with a steep slope. The early-type LF instead cannot be fitted by a single Schechter function, and a composite of two Schechter functions is needed. The faint-end upturn of the global cluster LF is due to the early-type cluster galaxies. The shape of the bright-end tail of the early-type LF does not seem to depend upon the local galaxy density or the distance from the cluster center. The late-type LF shows a significant variation only very near the cluster center. On the other hand, the faint-end tail of the early-type LF shows a significant and continuous variation with the environment.

Oxygen abundances for a large sample of dwarf and giant stars kinematically selected to be part of the Galactic thin and thick disks have been determined from a non-LTE analysis of the O I triplet lines at 777 nm. The abundance analysis was performed using the infrared flux method temperature scale, trigonometric surface gravities, and accurate atomic data. Within this framework, the ionization balance of iron lines could not be satisfied and so we adopted the iron abundances from Fe II lines only given that they are relatively less sensitive to changes in the atmospheric parameters. We show the resulting [O/Fe] vs. [Fe/H] relationship and briefly discuss its implications.

In this paper we first introduce Pupil Replication. We then show simulation results for a pupil replicated classical coronagraph. Furthermore, we show experimental results as a proof of concept as well as a preliminary design for the replication optics.

XMM-Newton has observed the quasar 3C273 several times between 2000 June and 2005 July. In addition data of NASA's Rossi X-ray Timing Explorer is used. We present the results of this monitoring campaign.

The X-ray spectrum of 3C273, in the energy regime of 0.2–100 keV, is believed to be composed of three components: a power law component above about 3 keV, a soft excess below about 2 keV, and an Fe-line. The Fe-line, detected in only a few observations of 3C273, is not detected significantly in individual XMM-observations. Only the 2000 June observations show evidence for a presence of a broad line feature. The high energy component above 3 keV is well described by a single power law model with varying indices and fluxes. The steeper spectra show significantly higher flux levels. The soft excess component below 2 keV also shows variations in flux and spectral slope. Different models are tested to identify the soft excess to be thermal or non-thermal emission.

HE0512–3329 is a gravitationally-lensed double QSO with damped Ly$\alpha$ systems observed at $z=0.931$ in front of both QSO images (DLA A and B). We have obtained spatially resolved HST STIS and optical VLT UVES spectra of both QSOs in order to study differences in the metal abundances across the lines of sight. We detect substantial differences, of roughly 0.5 dex, in both [Mn/H] and [Fe/H], on a transverse scale of 5 $h^{-1}$ kpc. Differential dust depletion appears as the most plausible explanation.

We study the faint end of the HI mass function (HIMF) in order to test the predictions of the CDM theory on the number density of objects with small (dark) masses. The neutral hydrogen is much better tracer of the underlying mass distribution compared to the luminous matter and can be used to test the existence of a population of small galaxies in which the star formation has been partially or completely suppressed during cosmic evolution. Due to technical limitations, the existing HI surveys are not very sensitive on masses below 10$^8$ HI $M_{\odot}$. We designed a blind HI survey to be sensitive for objects with small HI masses. The surveyed area is in the Canis Venatici groups of galaxies and covers in total $\approx$86 deg$^2$ of sky, with the observed velocities in the range $-350 < cz < 1400$ km s$^{-1}$. We detected 69 objects, 22 of them for the first time in HI. All new HI detections fall in the lower part of the mass-histogram, confirming our ability to detect galaxies with small HI masses. The calculated HIMF is flat in the faint end regime ($\alpha {\sim}{-}$1), different from the steep rise predicted by CDM models. Possible effects of the environment on the estimated HIMF parameters are discussed.

The detection of telluric extra-solar planets implies an extremely high contrast long exposure imaging capability at near-infrared and probably visible wavelengths. We present here the core of any Planet Finder instrument which is the extreme AO sub-system. The level of AO correction directly impacts on the exposure time required for planet detection. The extreme adaptive optics system has to correct for the perturbation induced by the atmospheric turbulence as well as for the internal aberrations of the instrument itself. An example of application is proposed in the frame of the EPICS project (XAO system for the ESO OWL telescope).

We develop and test a method for the estimation of carbon abundance ratios, [C/Fe], and metallicities, [Fe/H], in metal-deficient stars, based on application of artificial neural networks and synthesis models to medium-resolution (1–2 Å) spectra in the region of the CH G-band feature at $\lambda$ 4300 Å. We calibrate this method by comparison to modern carbon abundance determinations for N $\simeq 125$ stars reported in the recent literature. As a first application, we estimate the abundance of carbon and [Fe/H] for the sample of 56 stars identified as carbon-rich, relative to stars of similar metal abundance, in the sample of “strong G-band” stars discussed by Beers, Preston, & Shectman.

We present initial results from an high-resolution imaging search for damped Ly$\alpha$ absorbers toward the high-redshift quasar APM 08279+5255 by using the Adaptive Optics system (AO) attached to the Subaru telescope. We detected in total 11 objects within a $23''\times23''$ field around the quasar. Among these detected objects, we identified a possible candidate for the galaxy giving rise to the damped Ly$\alpha$ absorption at z$_{abs}$=2.974 with a criteria of distance from the sight-line toward the quasar and luminosity.

The goals of the Navigator Program at NASA are to find Earth-like planets around nearby stars, to determine if they are habitable, and to search for signs of life. Three strategic missions are planned to carry out this program: the Space Interferometer Mission Planetquest (SIM), the Terrestrial Planet Finder Coronagraph (TPF-C), and the Terrestrial Planet Finder Interferometer (TPF-I). These missions, along with the PI-class Kepler project, will each discover unique knowledge about extrasolar planets, synergistically building on the other missions.

The association of “long” Gamma-Ray Bursts (durations > 2 seconds) with peculiar Type Ic supernovae suggests strongly that this type of GRB is produced by the collapse of the rapidly rotating core of an initially very massive star to a black hole. At the time of collapse the star has lost its hydrogen-rich envelope and the GRB is thought to be produced by a collimated relativistic jet of matter ejected along the star's rotation axis. The angular momentum constraints for producing such a “collapsar” or “hypernova” suggest that the GRB-producing core collapses constitute only a small fraction of all core collapses of massive stars. As to the short-duration GRBs (< 2 seconds), which make up about one third of all GRBs, the most favoured model is that of the coalescence of a double neutron star or of a neutron star-black hole binary. Also these events are expected to be very rare, having a frequency of at most one event per hundred thousand years for a galaxy like our own. Due to the collimation of the relativistically ejected matter, the observable frequency of GRB events will, like in the case of the “long” bursts, be at least a factor hundred smaller.

We present new carbon-enhanced stars identified from the third public release of the Sloan Digital Sky Survey, SDSS-DR3. We have generated synthetic spectra with varying carbon abundances, and compare them with the SDSS spectra. We have also performed a preliminary analysis of s-process enhancement in several SDSS carbon-enhanced stars. Spectral features that are sensitve to stellar luminosity and temperature have also been explored. These methods will be applied to the large set of public SDSS data, as well as to the forthcoming data from SEGUE, the Sloan Extension for Galactic Understanding and Evolution, in order to study carbon enhancement at different metallicities, the fraction of s-process enhancement that occurs in carbon-enhanced stars, and possibly isotopic carbon abundances and nitrogen abundances.