We review the possibility that metallicity could provide a diagnostic for the age of a galaxy, hence that the most metal-poor star forming galaxies in the local universe may be genuinely young. Indeed, observational evidence for “downsizing” shows the average age of the stars in a galaxy to decrease with decreasing mass and metallicity. However, we conclude both from observational and theoretical viewpoints that metallicity is not an arrow of time. Consequently the most metal–poor galaxies of our local universe are not necessarely young. Current observations suggest that an old stellar population is present in all metal-poor galaxies, although a couple of cases, e.g. IZw18, remain under debate. Further observations with more sentitive equipement should settle this question in the coming years.

Several types of pre-solar grains, grains that existed prior to solar system formation, have been found in the fine-grained components of primitive meteorites, interplanetary dust particles (IDPs), and comet samples. Known pre-solar components have isotopic compositions that reflect formation from the ejecta of evolved stars. Other pre-solar materials may have isotopic compositions very similar to solar system materials, making their identification as pre-solar grains problematic. Pre-solar materials exhibit a range of chemical and thermal resistance, so their relative abundances can be used to probe the conditions in the solar nebula. Detailed information on the relative abundances of pre-solar and solar-system materials can provide information on the temperatures, radiation environment, and degree of radial mixing in the early solar system.

The modeling of the Asymptotic Giant Branch phase is made highly uncertain by some still unsolved issues related to the input macro-physics used to calculate the stellar evolution, namely mass loss, nuclear cross sections, overshooting and convective modeling. We show that in the massive intermediate mass models, which achieve at the bottom of their convective envelope temperatures sufficiently high to favour an advanced nucleosynthesis, the treatment of convection plays a major role in determining the physical and chemical evolution of the stellar models during this evolutionary phase.

Convection occurs in the visible photospheric layers of most stars having Te less than about 10000 K, and in some hotter stars. The solar granulation pattern is a symptom of this, as is the non-zero microturbulent velocity often required in abundance analysis to make both weak and strong lines yield the same abundance.

In very sharp-lined stars, the presence of a non-thermal velocity field in the visible stellar atmosphere leads to several other effects which may be detected in spectral line profiles. These include radial velocities that vary systematically with equivalent width, distortions of the line profile as compared to a profile computed with a Voigt profile and rotational broadening (“macroturbulence”), and asymmetries with respect to the line centre (“bisector curvature”).

Detection and interpretation of these effects, with the goal of obtaining empirical information about a velocity field present in the visible layers, requires comparison with calculated synthetic spectra which incorporate model velocity fields. Thus, this review will summarize some of the observational clues concerning photospheric velocity fields, as well as modelling aimed at interpreting these data.

We present results from our on-going study of the distribution and evolution of high-z galaxies. We exploited the large area coverage (~1.3 deg2) of the Subaru / XMM-Newton Deep Survey field (SXDF) to search for Lyman-break galaxies (LBGs) and Lyα Emitters (LAEs) at 3 <z< 7. We have found filamentary large scale structures, which are made of LAEs, with ~10 to 40 Mpc (in commoving units) scale voids as early as at z = 5.7. Galaxies at this redshift show clustering of ~1 Mpc in diameter (in physical unit). The inferred star formation rate density of these clustering is ~130 times the mean of the whole area, indicates burst of star formation activities. Combined with the UKIDSS/UDS photometry, the optical+near-IR SED fitting provides the estimate of masses for some of these high-z galaxies. Preliminary results indicate a number of galaxies at z >5 have already grown up to ~1011 solar mass.

The carbon isotopic ratio, 12C/13C, is a tracer of the mixing events during the evolution along the giant branch, due to the conversion of 12C into 13C (and 14N) via the CN cycle. A decrease of this ratio from 90, the solar value, to 20–25, is expected due to the first dredge-up. However, ratios down to 3–4, the CN cycle equilibrium value, have been observed in giants of the field, of globular and of open clusters. Observations seem to indicate a non-standard mixing in the RGB, probably beginning in the luminosity bump, when the outward moving hydrogen burning shell crosses the molecular weight barrier left by the convective layer in its maximum extent. We are currently analyzing a sample of 24 giants in 8 open clusters for which we determined 12C/13C from high resolution, high signal to noise spectra using spectrum synthesis. In this work we discuss the general characteristics of our results in comparison to previous analyses of giants in open clusters available in the literature.

The Geneva-Copenhagen Survey (Nordström et al., 2004) gives ages, metallicities, velocities, and Galactic orbits for a complete, magnitude-limited sample of 14,000 F and G dwarfs. We have verified the calibrations used in the GCS, improved those of Teff, [Fe/H], distance, and age from uvby β, and checked the effect on the resulting Galactic relations by end- to-end numerical simulations. All the main results of the GCS remain unchanged.

Convection theories for star and planet formation studies have to be (1) simple, to allow a self-consistent solution with other relevant processes, (2) time-dependent, because convection often starts in collapse-flows, and (3) robust, i.e. physically well-behaved under a wide range of conditions ranging from the quiet protoplanetary nebula to supercritical protostellar accretion-shocks with Mach-numbers of a few hundred. I describe how the equations of radiation fluid-dynamics can be augmented by a one-equation convection model in order to construct a system of equations that contains the Sun, brown dwarfs and planets as well as their nearly isothermal parent-clouds. The system of equations is calibrated to the Sun and tested by the solar convection zone and the pulsations of RR-Lyrae stars. I discuss the following applications: (1) star formation as the collapse of Bonnor-Ebert spheres of masses ranging from the stellar domain to the brown dwarf region, (2) the approach to the main sequence, (3) companion mass determinations for direct imaging searches for exoplanets, with GQ Lupi as an example, and (4) the formation of Pegasi-planets, and the “large core” exoplanet, HD 149 026, in particular.

We review the results recently obtained by means of panoramic (3D) spectroscopy on the 6-m telescope BTA (SAO RAS). This research is devoted to observational evidences of gas inflow into the centers of galaxies, which must ensure the fueling of an active nucleus. 3D spectroscopy allows us to trace the behavior of gas and stars in the one-kiloparsec size vicinity of an AGN and also far from the center.

The goal of this work is to present an analysis of the observational projects developed by the Teaching and Popularization Section of the Liga Ibero-Americana de Astronomía (LIADA). The Section is based in Brazil and counts on the support of 16 volunteer coordinators from most Latin-American countries. The observational projects are described on the home page of LIADA and aim to attract the attention of the general public, teachers and students to encourage their active participation in observational astronomy. The strategy is to circulate support material and open a discussion forum about each of the astronomical phenomena to enhance their consideration by and visibility to the public. Participants' reports are posted on the Internet forum and the web page of LIADA. We have analyzed the records of these activities and present an evaluation of the difficulties with written reports, the need of a dynamic maintenance of the home page, the establishment of a useful communications network and the visibility of the activities of LIADA.

We investigate the variations of the magnetic field, Doppler factor, and relativistic particle density along the jet of a quasar at z=0.72. We chose 4C 19.44 for this study because of its length and straight morphology. The 18 arcsec length of the jet provides many independent resolution elements in the Chandra X-ray image. The straightness suggests that geometry factors, although uncertain, are almost constant along the jet. We assume the X-ray emission is from inverse Compton scattering of the cosmic microwave background. With the aid of assumptions about jet alignment, equipartition between magnetic-field and relativistic-particle energy, and filling factors, we find that the jet is in bulk relativistic motion with a Doppler factor ≈ 6 at an angle no more than 10∘ to the line of sight over de-projected distances ≈ 150–600 kpc from the quasar, and with a magnetic field ≈10 μGauss.

New interest have appeared recently in observations of radio sources at the shortest radio wavelengths in connection with planned searches CMB radiation. A high sensitivity 2.7 cm receiver was installed at RATAN-600 in 1989. We discuss the results of deep surveys (“Cold”) of a ±10' strip of the sky centered on the declination of SS 433 covering an interval of 11h in R.A. carried out with the RATAN-600 telescope at 2.7 and 7.6 cm in 1987–2000.

We select far-infrared (60 μm) and far-ultraviolet (1530Å) samples of nearby galaxies. We derived distributions of the bolometric luminosity of young stars in both samples: they are found to be consistent with each other for galaxies of intermediate luminosities but some differences are found for high (>5 × 1010L⊙) luminosities. The ratio of the total IR luminosity to the FUV one is found to increase with the bolometric luminosity in a similar way for both samples up to 5 × 1010L⊙. Brighter galaxies are found to have a different behavior according to their selection: the LTIR/LFUV ratio of the FUV selected galaxies brighter than 5 × 1010L⊙ reaches a plateau whereas LTIR/LFUV continues to increase with the luminosity of bright galaxies selected in FIR. The volume averaged specific star formation rate (SFR per unit galaxy stellar mass, SSFR) is found to decrease toward massive galaxies within each selection. The SSFR is found larger than that measured for optical and NIR selected sample for the whole mass range for the FIR selection and for masses larger than 1010M⊙ for the FUV selection. Luminous and massive galaxies selected in FIR appear as active as galaxies with similar characteristics detected at z ~ 0.7. Details are presented in Buat et al. (2006).

We present a model for the prediction of the optical/infra-red emission from ULXs. In the model, ULXs are binary systems with accretion taking place through Roche lobe overflow. We show that irradiation effects and presence of an accretion disk significantly modify the optical/infrared flux compared to single stars, and also that the system orientation is important. We include additional constraints from the mass transfer rate to constrain the parameters of the donor star, and to a lesser extent the mass of the BH. We apply the model to fit photometric data for several ULX counterparts. We find that most donor stars are of spectral type B and are older and less massive than reported elsewhere, but that no late-type donors are admissible. The degeneracy of the acceptable parameter space will be significantly reduced with observations over a wider spectral range, and if time-resolved data become available.

We present preliminary results of a Fourier transform power spectra analysis carried out on a sample of dwarf irregular galaxies and Local Group members. This project is intended to study turbulence and the ISM structure in irregulars as a class.

Using HST emission line images of the Orion Nebula, separated by 7 years in epoch, we have obtained evidence of localized temporal variability of both density and temperature during this period. Applying a digital filter to reduce high frequency noise, we used images in Hα and [OIII] to quantify separately the variability in these two parameters. We detected fractional temperature variations of order 0.4% on scales of 2′10−2 pc. The same images yielded proper motion information; using cross-correlation to optimize the accuracy of the differential measurements we produced velocity field maps across the nebula, with vectors ranging up to ~130kms−1 across the line of sight. It is notable that in zones of rapid proper motion we find by far the largest density variations, as would be expected. It is much easier to quantify the temperature variations, on the other hand, in zones with low or zero detectable proper motion (see the other figure here), though these temperature variations appear across the whole face of the nebula.

We are using NVO tools to obtain a large (N≃100), uniform (SDSS images, cross checked with HST images; analyzed using WESIX) database of super star clusters in nearby star-forming galaxies in order to address two fundamental astronomical questions: (i) Is the initial luminosity function of star clusters universal?; and (ii) What fraction of super star clusters is ‘missing’ in optical studies (i.e., are hidden by dust)?

We use multi-colour data of the gravitational lensing cluster Abell 1835 to search for high-z candidates (Richard et al. 2006) and extremely red galaxies.

Applying a colour criteria of R-K ≥ 5.6 we have selected 12 EROs, of which 10(9) have no R(I)-band detection. Two of these sources posses multiple detections in the ACS z850 band, possibly gravitationally bound objects.

Using the method of Pozzetti and Mannucci (2000) to classify an ERO either as evolved elliptical or dusty starburst, we find that two thirds of all objects have colours assigned to evolved ellipticals. One of the remaining 4 sources is the known sub-mm source SMMJ14009+0252.

The spectral energy distributions of sources with no optical detection show strong similarities to the SED of the high-z object of Mobasher et al. (2005), i.e. a degeneracy between a low- and high-z solution. However, for objects we accept the low-z solution as the better fit.

A detailed analyses of the colour properties and spectral energy distribution will be published in two forthcoming papers (Schaerer et al., Hempel et al.).

In this contribution, we will overview the NANTEN observations of molecular clouds faced to H II regions, supershells, and interacting galaxies, which demonstrate that star/molecular cloud formation is being triggered by young OB associations, supershells, and collisions between galaxies. The large volume filling factor of explosive events like supernovae, ultraviolet radiation fields and stellar winds of massive stars suggest that most of the interstellar medium has been agitated by such strong impacts and triggered star formation is a common event at all scales from small molecular clouds to large galaxy-galaxy mergers. The consequence is the increase of star formation efficiency in many cases, and that more massive stars or clusters of more member stars tend to be formed by triggering than in spontaneous star formation.

The existence of an observed meteor shower associated with some Near-Earth Asteroid (NEA) is one of the few useful criteria that can be used to indicate that such an object could be a candidate for being regarded as an extinct or dormant cometary nucleus. In order to identify possible new NEA-meteor showers associations, the secular variations of the orbital elements of the NEA 2000 PG3, with comet-like albedo (0.02), and moving on a comet-like orbit, was investigated under the gravitational action of the Sun and six planets (Mercury to Saturn) over one cycle of variation of the argument of perihelion. The theoretical geocentric radiants and velocities of four possible meteor showers associated with this object are determined. Using published data, the theoretically predicted showers were identified with the night-time September Northern and Southern δ-Piscids fireball showers and several fireballs, and with the day-time meteor associations γ-Arietids and α-Piscids. The character of the orbit and low albedo of 2000 PG3, and the existence of observed meteor showers associated with 2000 PG3 provide evidence supporting the conjecture that this object may be of cometary nature.