We investigate selection and weighting of features by applying a random forest algorithm to multiwavelength data. Then we employ a k-nearest neighbor method to distinguish quasars from stars. We then compare the performance of this approach based on all features, weighted features, and selected features. We find that the k-nearest neighbor approach combined with random forests effectively separates quasars from stars.

To test General Relativity with the tracking data of the BepiColombo Mercury orbiter we need relativistic models for the orbits of Mercury and of the Earth, for the light-time and for all the spatio-temporal reference frames involved, with accuracy corresponding to the measurements: ≃10 cm in range, ≃2 micron/s in range-rate, over 2 years.

For the dynamics we start from the Lagrangian post-Newtonian (PN) formulation, using a relativistic equation for the solar system barycenter to avoid rank deficiency. In the determination of the PN parameters, the difficulty in disentangling the effects of β from the ones of the Sun's oblateness is confirmed. We have found a consistent formulation for the preferred frame effects, although the center of mass is not an integral. For the identification of strong equivalence principle (SEP) violations we use a formulation containing both direct and indirect effects (through the modified position of the Sun in a barycentric frame).

In the light-time equations, the Shapiro effect is modeled to PN order 1 but with an order 2 correction compatible with (Moyer 2003). The 1.5-PN order corrections containing the Sun's velocity are not relevant at the required level of accuracy.

To model the orbit of the probe, we use a mercury-centric reference frame with its own “Mercury Dynamic Time”: this is the largest and the only relativistic correction required, taking into account the major uncertainties introduced by non-gravitational perturbations.

A delicate issue is the compatibility of our solution with the ephemerides for the other planets, and for the Moon, which cannot be improved by the BepiColombo data alone. Conversely, we plan to later export the BepiColombo measurements, as normal points, to contribute with their unprecedented accuracy to the global improvement of the planetary ephemerides.

We present a study of the pre-main-sequence (PMS) population in the stellar association LH95 in the LMC, based on the deepest HST/ACS photometry ever taken in a region of the Magellanic Clouds. This association hosts ~ 2500 PMS stars, distributed in three main subclusters. We isolate this population by subtracting the LMC field, study the reddening distribution which peaks at AV ~ 0.5 mag, and assign masses, down to 0.2 M⊙, to each member using a newly derived conversion of evolutionary models for the LMC metallicity and the ACS photometric system. We derive the first IMF in the subsolar regime ever measured outside our Galaxy, complete down to 0.4 M⊙. It presents a flattening at 1 M⊙, changing its slope from x = 2.05 for intermediate-mass stars to x = 1.05 in the subsolar regime. Correcting for unresolved binarity, it is compatible with the Galactic IMF. We do not find evidence of spatial variations of the IMF in the region. We study the ages of the PMS members using maximum-likelihood methods based on the location of the stars in the color–magnitude diagram with respect to 2D isochrones obtained by applying intrinsic and observational biases (differential extinction, variability, confusion, unresolved binarity) to modeled simple stellar populations. We find a most likely global age of ~ 10 Myr, and demonstrate that neglecting the aforementioned biases leads to an underestimation of the cluster age of up to 50%. We find that the observed luminosity spread is more than twice larger than can be explained by such biases, confirming that the star formation in LH95 lasted a few Myr.

As a sequel to the Li observations by Balachandran, Lambert & Stauffer (1988, 1996) in 35 stars of the 50 Myr old cluster α Persei, we have obtained and analyzed high resolution spectra of another 51 stars. Following a reconsideration of the cluster membership of the stars (Prosser 1992, Makarov 2006, Mermilliod et al. 2008, and Patience et al. 2002), we discuss the Li abundances for 70 stars. With our larger sample, we reexamine the question of whether the scatter in Li abundance at a given Teff seen in young clusters at cool temperatures is real or not.

Ejection of material after the Deep Impact collision with Comet Tempel 1 was studied based on analysis of the images made by the Deep Impact cameras during the first 13 minutes after impact. Analysis of the images shows that there was a local maximum of the rate of ejection at time of ejection ~10 s with typical velocities ~100 m/s. At the same time, a considerable excessive ejection in a few directions began, the direction to the brightest pixel changed by ~50°, and there was a local increase of brightness of the brightest pixel. The ejection can be considered as a superposition of the normal ejection and the longer triggered outburst.

Over the past five years, the Egyptian-Spanish Mission on the archaeoastronomy of ancient Egypt and its collaborators has been performing an ambitious scientific project with the aim of studying the cosmovision of the ancient civilization of the pharaohs. Part of the project has consisted of a re-analysis of the iconographic and historical sources that has allowed, among other things, a reassessment of the calendar theory and a new proposal for the sky-maps of ancient Egypt. For various reasons, Archaeoastronomy has not been one of the favourite disciplines of egyptologists in the past. Probably because of this, important questions such as the orientation of Egyptian temples and the relevance of astronomy in this respect had never been afforded with the requisite seriousness and depth. Our work has had among its various priorities, the solution of this problem. In order to achieve this, our team has so far measured the orientation of some 330 temples in the Valley, the Delta, the Oases and the Sinai. The aim is to find a correct and almost definitive answer to the question of whether the ancient Egyptian sacred constructions were astronomically aligned or not. Our results may provide an affirmative answer.

In this talk a brief introduction is given to made-to-measure particle methods and their potential use for modeling the Milky Way Galaxy.

The wavelet transform acts to segregate objects in function of their size. We apply this method on images of galaxies to decompose them into coefficients representing only objects of the same size. The total fluxes of the wavelet coefficients describe the cumulative power spectrum of spatial frequencies. Based on this spectrum, we propose a new parameter to quantify the galaxy texture. As expected, it remains small and quite invariant for early-type galaxies, while it covers a large range and takes larger values for late-type galaxies. Combined with a second parameter, our determination of the texture is able to successfully separate galaxy types. By thresholding the wavelet coefficients, we detect luminous lumps. In irregular galaxies, their radial distribution seems to show a double peak. This could be the trace of a privileged radial distance of strong star formation regions.

In this study we investigate the effects of solar activity on the surface air temperature of mid-latitudes. This enables us to understand existence of solar activity effects on the temperature. We used surface air temperature and pressure data as climate parameters, and solar flare index data as solar activity indicator, for the 25 - 50 degree longitude and 30 - 70 degree latitude zone, including Turkey and European part of Russia. We considered the parameters temperature, pressure and flare index data for the period ranging from January 1975 to the end of December 2007, which covers almost three solar cycles, namely 21st, 22nd, and 23rd. We found some significant correlations between solar activity and surface air temperature for cycles 22 and 23 for some zones. We applied multitaper method to obtain the cyclic behavior of surface air temperature data sets. The most pronounced power peaks were found by this transform around 1.2 and 2.5 years which were reported earlier for some solar activity indicators. We concluded that signature of solar activity effect exists on surface air temperature of mid-latitudes where we studied.

The evolution of Fe-peak elements of several Local Group Dwarf Spheroidal Galaxies are discussed based on the comparison between a chemical evolution model and obsevations. In our scenario, the evolution of these galaxies are mainly controlled by a low star formation efficiency coupled with very intense galactic winds. The low star formation rate gives rise to the observed low metallicities and to [alpha/Fe] and [s/Fe] ratios below solar, whereas the intense galactic winds are responsible for the sharp decrease observed in several abundance ratios. The shape of the stellar metallicity distributions are defined by both parameters and the observed data cannot be reproduced without evoking galactic winds. The same scenario applied to a standard model fits very well several Fe-peak elements, with different nucleosynthesis prescriptions for each set of elements.

We show that anomalous extinction (deviations from the traditionally adopted RV = AV/E(B − V) = 3.1 introduces large uncertainties in the distances of stars, for distances larger than 1-2 kpc. We argue that for such distances and for directions close to the galactic plane, the use of extinction models based on the gas distribution in the Galaxy is safer, for the moment, than the use of extinction maps.

In de la Fuente (2007; Ph. D. Thesis), the molecular clump associated with the ultracompact HII region G12.21–0.10 was confirmed as a large, hot, dense Hot Molecular Core nearby to the ionized gas. The density was confirmed by comparing low resolution NH3(2, 2) and (4, 4) VLA observations, with other molecular lines and radio–continuum observations. These results will be presented in detail in a forthcoming paper (de la Fuente et al. in preparation). In these works, for the first time, the spatial location of the Hot Molecular Core is presented. Here we present the NH3(4,4) observations from de la Fuente (2007; Ph. D. Thesis), confirming that the hotter and denser gas in the molecular core lies in a compact structure, of smaller scale than the NH3(2, 2) emission.

The distribution of chemical abundances and their variation in space and time are important tools to understand the chemical evolution of disks in spiral galaxies. In this work we present an one infall chemical evolution model for the Galactic disk based on an updated version of the Trieste group model. We adopted a pre enriched gas (to take into account the effect of the halo evolution), an inside-out scenario for the formation of the disk and a threshold in the surface gas density to regulate the star formation rate. The observational constraints for the solar neighbourhood were well reproduced and the spatial and time evolution of the radial abundance gradient were studied. We also used this model to reproduce the chemical evolution of some nearby spiral galaxies. The model was scaled to the disk properties of each galaxy and its dependence with the star formation efficiency and the time scale for the infalling gas into the disk were explored. Using this modified model we were able to reproduce the observed constraints available in the literature for this galaxies. The similarities and the differences between the chemical evolution of these objects and teh Milky Way are discussed to provide a basis to the understanding of the chemical evolution of disks.

We review briefly direct and indirect methods of measuring the masses of black holes in galactic nuclei, and then focus attention on supermassive black holes in active nuclei, with special attention to results from reverberation mapping and their limitations. We find that the intrinsic scatter in the relationship between the AGN luminosity and the broad-line region size is very small, ~0.11 dex, comparable to the uncertainties in the better reverberation measurements. We also find that the relationship between reverberation-based black hole masses and host-galaxy bulge luminosities also seems to have surprisingly little intrinsic scatter, ~0.17 dex. We note, however, that there are still potential systematics that could affect the overall mass calibration at the level of a factor of a few.

Radio astronomy has played an important part in the study of relativity. Famous examples include the discovery and exploitation of pulsars for precise binary pulsar tests, the proof of the existence of gravitational radiation and the discovery of the Cosmic Microwave background. In the future, radio astronomy will continue to play a decisive role, assisted by new and upcoming instruments like LOFAR and the SKA. In this review, I will present the revolution that is ongoing in radio astronomical techniques and outline the impact expected on the studies of relativity.

The atmospheric response to the 11-year solar cycle is studied using the fully interactive 3-D coupled chemistry-general circulation model LMDz-REPROBUS with a complete seasonal cycle. We will show results concerning a comparison between two series of 20-year runs, one in maximum of activity and the other in minimum. The stratosphere-troposphere system shows partly significant response to a solar cycle enhancement of UV radiation. We show how the changes in stratospheric ozone, temperature and zonal wind are connected.

Observations show that massive stars always form in clusters or associations, and that the most massive stars form in the dense cores of large clusters. This suggests that accretion processes in cluster cores may be responsible for the formation of stars. In addition, young stellar clusters have been found to contain subclusters, so that star formation can be seen to be a hierarchical process that involves clustering on a range of scales. In this paper, we propose a fractal model of the parental molecular cloud, namely that of the Julia set given by f(z) = z2 + c, where z and c are complex numbers and c = −0.745430 + 0.113008i, to explain this phenomenon and the associated complex structures seen in star-forming regions.

An unbiased sample of solar twins shows that the Sun has a normal Li abundance for its age and that a low Li abundance does not imply the presence of planets. We find a tight correlation between Li and age, which holds for all stars analyzed in our sample: solar twins, stars with and without detected giant planets, and stars that may host terrestrial planets.

The observation of the sky had an important rôle among the Maya, Aztecs and other prehispanic peoples of Mesoamerica. Their familiarity with the regularities of the apparent motion of the Sun, the Moon and bright planets is attested in a large amount of astronomical data contained in codices and monumental hieroglyphic inscriptions, as well as in their sophisticated calendrical system. On the other hand, the study of architectural alignments has disclosed that civic and ceremonial buildings were largely oriented on astronomical grounds, mostly to sunrises and sunsets on certain dates, allowing the use of observational calendars that facilitated a proper scheduling of agricultural and the associated ritual activities in the yearly cycle. Both accurate knowledge and other astronomically-derived concepts reveal that the significance attributed to certain celestial events by the ancient Mesoamericans can be explained in terms of the relationship of these phenomena with specific environmental and cultural facts, such as seasonal climatic changes and subsistence strategies. It was particularly due to its practical utility that astronomy, intertwined with religious ideas and practices, had such an important place in the worldview and, consequently, in the cosmologically substantiated political ideology of Mesoamerican societies