Color selection is an efficient technique for extracting candidate AGNs. Many AGNs have been selected on the basis of colors at various wavelengths. In this work, we extracted AGN candidates using near-infrared colors and investigated their properties.

A large fraction, between 10 and 25%, of very metal-poor stars in the Galactic halo are carbon-rich objects, with enhancements of carbon relative to iron exceeding a factor 10. The majority of these carbon-enhanced metal-poor (CEMP) stars show enhancements of heavy s-process elements and have been found to be spectroscopic binary systems. Many of their properties are well explained by the binary mass transfer scenario, in which a former asymptotic giant branch (AGB) companion star has polluted the low-mass star with its nucleosynthesis products. The same scenario predicts the existence of nitrogen-rich metal-poor (NEMP) stars, with [N/C] > 0.5, from AGB companions more massive than about 3 solar masses. In contrast to CEMP stars, however, such NEMP stars are very rare. Recent studies suggest that the high frequency of CEMP stars requires a modified initial mass function (IMF) in the early Galaxy, weighted towards intermediate-mass stars. Such models also implicitly predict a large number of NEMP stars which is not seen.

The presence of water has been considered for a long time as a key condition for life in planetary environments. The Cassini mission discovered water vapour in the Kronian system by detecting absorption of UV emission from a background star (Hansen et al. 2006). Prompted by this discovery, we started an observational campaign for search of another manifestation of the water vapour in the Kronian system, its maser emission at the frequency of 22 GHz (1.35 cm wavelength). Observations with the 32 m Medicina radio telescope (INAF-IRA, Italy) started in 2006 using Mk5A data recording and the JIVE-Huygens software correlator. Later on, an on-line spectrometer was used at Medicina. The 14 m Metsähovi radio telescope (TKK-MRO, Finland) joined the observational campaign in 2008 using a locally developed data capture unit and software spectrometer. More than 300 hours of observations were collected in 2006-2008 campaign with the two radio telescopes. The data were analysed at JIVE using the Doppler tracking technique to compensate the observed spectra for the radial Doppler shift for various bodies in the Kronian system (Pogrebenko et al. 2009). Here we report the observational results for Hyperion, Titan, Enceladus and Atlas, and their physical interpretation. Encouraged by these results we started a campaign of follow up observations including other radio telescopes.

The objective of this contribution is to present some results of an evaluation on the local conditions at the site that were considered in order to propose that the Observatorio Astronómico Nacional, Tonantzintla, (OAN-Tonantzintla) become a National Facility for Astronomy Education. The evaluation included a quantitative diagnostic (CCD photometry) on the quality of the local sky. The attributes of the 1-m telescope, the current instrumentation and a well planned upgrading that includes new instrumentation is considered at the basis for a successful transition maintaining the attractiveness of the site for astronomy education. A 3-year upgrading program actually in progress at UNAM is providing funding for that purpose. Physics and astronomy programs at college and graduated levels at UNAM will benefit from this, yielding clear connections among astronomy researchers and educators and students at various levels. Although the OAN-Tonantzintla faces the danger of deteriorating its sky conditions, we are maintaining awareness of the night sky characteristics in long-term monitoring campaigns and encouraging the local authorities to find alternative solutions to this problem.

New helium abundances of planetary nebulae located towards the bulge of the Galaxy were derived, based on observations made at OPD (Brazil). We present accurate helium abundances for 56 PNe located towards the galactic bulge. The data show good agreement with other results in the literature, in the sense that the distribution of the abundances is similar to previous works. Furthermore, the radial helium gradient is extended towards the galactic center. The results show that no trend can be identified when comparing the internal gradient (R ≤ 4 kpc) to the whole galactic disk.

We obtained long-slit spectra of high S/N of the galaxy M32 with the GMOS Spectrograph at the Gemini-North telescope. We analysed the integrated spectra by means of spectral fitting in order to extract the mixture of stellar populations that best represents its composite nature. As our main result, we propose that an ancient and an intermediate-age population co-exist in M32, and that the balance between these two populations change between the nucleus and outside one effective radius (1reff) in the sense that the contribution from the intermediate population is larger at the nuclear region. We retrieve a smaller signal of a young population at all radii whose origin is unclear, and may be a contamination from horizontal branch stars, blue stragglers or a true young population previously unidentified (Monachesi et al., this volume). We compare our metallicity distribution function for a region 1 to 2 arcmin from the centre to the one obtained with photometric data by Grillmair et al. Both distributions are broad, but our spectroscopically derived distribution has a significant component with [Z/Z⊙] ≤ −1, which is not found by Grillmair et al.

The effects of dry and wet merging on the Scaling Laws (SLs) of elliptical galaxies (Es) are discussed. It is found that the SLs, possibly established at high redshift by the fast collapse of gas-rich and clumpy stellar distributions in preexisting dark matter halos following the cosmological SLs, are compatible with a (small) number of galaxy mergers at lower redshift.

A key part of the modern-day regenerative solar magnetic dynamo is the reversal of the Sun's global magnetic field every eleven years. However, recent theoretical models indicate that young-rapidly rotating Sun-like stars may not always undergo full magnetic reversals, but instead may sometimes undergo “attempted” reversals where the magnetic field declines in strength only to return with the same polarity. Using the technique of Zeeman Doppler imaging we have mapped the magnetic field topology of a small sample of young Sun-like stars at multiple epochs, and present tentative evidence of an “attempted” magnetic field reversal on one of our stars.

Optical/near-infrared observations of 14 globular cluster (GC) systems in early-type galaxies are presented. We investigate the recent claims (Yoon et al. 2006) of colour bimodality in GC systems being an artefact of the nonlinear colour–metallicity transformation driven by horizontal-branch morphology. Taking advantage of the fact that the combination of optical and near-infrared colours can, in principle, break the age/metallicity degeneracy we also analyse age distributions in these systems.

Within the framework of linearized Einstein field equations we compute the gravitomagnetic effects on a test particle orbiting a slowly rotating, spherical body with a rotating matter ring fixed to the equatorial plane. Our results show that the effect on the precession of particle orbits is increased by the presence of the ring.

The orbits of the planets as represented by the JPL planetary ephemerides are now primarily determined by radio tracking of spacecraft. Analysis of the data and propagation of the orbits relies on an internally consistent set of equations of motion and propagation of radio signals including relativistic effects at the centimeter level. The planetary ephemeris data set can be used to test some aspects of the underlying theory such as estimates of PPN parameters γ and β, time variation in the gravitational constant G, rotation of the solar system relative to distant objects (Mach's principle), and place stringent limits on the possible violation of the inverse-square law.

Icy plumes venting from Enceladus draw obvious comparisons to such features seen in comets. This paper outlines a consistent evolution from cometary activity to larger icy bodies in the outer solar system. The major differences are due to the systematic effects of increased gravity, including more spherical solid bodies (self-gravity), less porosity, the possible existence of liquid water due to internal sources of heat (Enceladus) versus possible cometary cyrovolcanism, internal inhomogeneities leading to jet-like features, and the possibility of a quasi-bound dusty gas atmosphere, as opposed to the extensive exospheres of comets. Similarities exist also, including gas and dust emission and the filamentary nature of jet-like features (caused by surface topography in comets), surface evolution by dust accumulation, heat and gas transport through the surface layers, among others. Initial results regarding the plume chemistry and comparisons to CAPS ion data show similarities too. Others have considered additional effects such as, charging of particles, micrometeorite impacts and complex interactions with the E-ring neutrals and plasma in great detail so these topics remain outside the scope of this paper.

The UV upturn phenomenon found in giant elliptical galaxies through space observations has been a mystery. Recent GALEX observations have revealed new facts. The most notable is the rarity of UV upturn galaxies. Unlike previous beliefs, UV upturn is found only in less than 10 percent of giant ellitpical galaxies. Another notable finding is that the UV flux has been increasing for the last couple of billion years. This is consistent with the theoretical predictions that suggest hot horizontal branch stars are the main UV sources. Remaining theoretical and observational issues on this topic can be found in another recent review of mine (Yi 2008).

We have studied the core of the Hydra I cluster, around its central cD galaxy, NGC 3311. We have analyzed the kinematics a sample of 60 intracluster planetary nebulae (PNs), detected using the multi-slit imaging spectroscopy technique (MSIS, Gerhard et al., 2005, Ventimiglia et al., 2008). PNs are good tracers of light (Coccato et al., 2009) and the MSIS allows to measure their velocities and positions at the same time. The histogram of the PN radial velocities presents several discrete components. We are comparing this result with ΛCDM hydro-dynamical simulations and other data in order to interpret it in the framework of the formation of extended halos around cD galaxies. V band photometric data around NGC 3311 have revealed the presence of an excess of light in the North-East part of the galaxy, which is spatially coincident with most of the PNs contributing to the reddest peak in the PNs LOSVD. We have measured, using Long-Slit data, the velocity of HCC26, a dwarf (DW) galaxy in the middle of the excess of light. The reddest peak in the PNs LOSVD is consistent both with the velocity of HCC 26 and of several other DWs in the same region. We are investigating the possibility that the light in excess has been stripped from these galaxies and now incorporated into the halo of NGC 3311.

Broad absorption lines (BALs), seen in a small fraction of both the radio-quiet and radio-loud quasar populations, are probably caused by the outflow of gas with high velocities and are part of the accretion process. The presence of BALs is due to a geometrical effect and/or it is connected with the quasar evolution. Using the final release of FIRST survey combined with a catalog of BAL QSOs from SDSS/DR3, we have constructed a new sample of compact radio-loud BAL QSOs, which constitutes the majority of radio-loud BAL QSOs. The main goal of this project is to study the origin of BALs by analysis of the BAL QSOs radio morphology, orientation, and jet evolution using the European VLBI Network (EVN) at 1.6 GHz and the Very Long Baseline Array (VLBA) at 5 and 8.4 GHz.

Helium abundances were derived for a sample of planetary nebulae of the Small Magellanic Cloud. These abundances were corrected from the chemical evolution of the galaxy as well as from stellar nucleosynthesis, and the primordial helium abundance then was estimated for the sample. Results indicate that the resulting average value for the sample is consistent with the expected values for primordial helium from SBBN and other values derived from HII regions in different stellar systems, even varying the enrichment ratio within its uncertainty range.

We present the results of [Ba/Eu] ratio determinations for a sample of Carbon-Enhanced Metal Poor (CEMP) stars, comparing them with other CEMP stars found in the literature for which abundances for both elements are available. The stellar spectra were observed at 4.2m William Herschel Telescope (WHT) on July/2003, using Utrecht Echelle Spectrograph (UES) with R ~ 52000 and S/N ~ 40. WHT covers a wavelength range of λλ3700-5700.

In the last few years, X-ray observational studies of young star clusters have advanced significantly, mainly thanks to the great capabilities of current X-ray observatories such as Chandra and XMM/Newton. In addition to enabling a detailed study of coronae of individual bright stars, high-spatial-resolution X-ray observations of many young clusters and star-forming regions, even massive and distant ones, have led to the detection of large populations of X-ray-bright members, often down to subsolar masses, and despite strong absorption. The peculiar ability of X-ray emission to select young, low-mass cluster stars against a crowded Galactic-plane field-star background has permitted better studies of global cluster properties, with respect to optical/infrared studies alone, including of cluster initial mass functions (across wide mass ranges), star-formation histories (with indication of age spreads—or even sequences—in many clusters) and morphologies (various degrees of symmetry and dynamical relaxation), sometimes with evidence of mass segregation. Also, the complementary availability of X-ray and optical/infrared data has enabled to place constraints on lifetimes and depletion mechanisms of pre-main-sequence circumstellar disks.

The french committee linking astronomers and teachers (CLEA, http://clea-astro.eu) has been active for more than 30 years in the formation of teachers (from primary to high school) in the field of astronomy.

Stars with significant subsurface convection zones develop magnetic loop structures that, arising from the surface upward to the external atmospheres, cause flux variability detectable throughout the whole electromagnetic spectrum. In fact, diagnostics of magnetic activity are in radio wavelengths, where gyrosincrotron radiation arises from the quiescent and flaring corona; in the optical region, where important signatures are the Balmer lines, the Ca ii IRT and H&K lines; in the UV and X ray domains, the latter mainly due to coronal thermal plasma. The zoo of different magnetic features observed for the Sun – spots, faculae, flares, CMEs – are characterized by different temporal evolution and energetics, both in quantity and quality. As a consequence, the time scale of variability, the amount of involved energy and the quality of the involved photons are used as fingerprints in interpreting the observed stellar variability in the framework of the solar-stellar analogy. Here I review main results from long-term multiwavelength observations of cool star atmospheres, with emphasis to similarities and differences with the solar case.