Participants

Ethnoastronomy in the colonies in northern Santa Fe province, Argentina

In this talk, we present part of a study about cultural astronomy among European colonists who settled in the northern area of the Argentinean province of Santa Fe, which is part of the southern Chaco. These colonists arrived among waves of immigration occurring in Argentina in the second half of the 19th century and the first half of the 20th century. Ethnographic field research among these rural immigrants and their descendants revealed that the presence of immigrants with different kinds of previous contact with the sky and with different agricultural practices, generated a set of asterisms and astronomical practices that were distributed according to the origins of the different European communities, the contact between colonists with different origins and the criollos, and also according to their uses in agriculture, animal husbandry and meteorology
Hide Información

Spectroscopy of compact groups at intermediate redshifts

Compact groups are groups of four or more galaxies, spatially dense, relatively isolated from larger structures and whose members are separated by distances of the order of their scale.
This work begins with the observation of 24 compact groups selected from the catalog of McConnachie et al. (2009) (incomplete in spectroscopic information), and it is concentrated in the confirmation of those real and compact associations, discarding the groups containing galaxies in projection. We performed a reduction of the obtained spectra and calculated the redshifts of the candidate members. In addition, the morphology of the members of this sample of compact groups is studied.
Hide Información

Multiple-Planet Scattering and the Origin of Hot Jupiters

Doppler and transit observations of exoplanets show a pile-up of Jupiter-size planets in orbits with a 3-day period. A fraction of these hot Jupiters have retrograde orbits with respect to the parent star's rotation, as evidenced by the measurements of the Rossiter-McLaughlin effect. To explain these observations we performed a series of numerical integrations of planet scattering followed by the tidal circularization and migration of planets that evolved into highly eccentric orbits. We considered planetary systems having 3 and 4 planets initially placed in successive mean-motion resonances, although the angles were taken randomly to ensure orbital instability in short time-scales. The simulations included the tidal and relativistic effects, and precession due to stellar oblateness. Our results show the formation of two distinct populations of hot Jupiters. The inner population (Population I) is characterized by semimajor axis $a < 0.03$~AU and mainly formed in the systems where no planetary ejections occurred. Our follow-up integrations showed that this population was transient with most planets falling inside the Roche radius of the star in $<1$ Gyr. The outer population of hot Jupiters (Population II) formed in systems where at least one planet was ejected into interstellar space. This population survives the effects of tides over $>1$ Gyr and fits nicely the observed 3-day pile-up. The relative proportion of retrograde planets seems of be dependent on the stellar age. Both the distribution of almost aligned systems and the simulated 3-day pile up also fit observations better in our 4-planet simulations. This may suggest that the planetary systems with observed hot Jupiters were originally rich in the number of planets, some of which were ejected. In a broad perspective, our work therefore hints on an unexpected link between the hot Jupiters and recently discovered free floating planets.
Hide Información

Determination of the non-stellar continuum in Active Galactic Nuclei

The usual definition of Active Galactic Nuclei (AGN) involves the release of energy that cannot be explained by stellar process. However, quantifying the shape and amount of this non-stellar continuum is not an easy task, the main difficulty arising from the fact that the observed flux contains an appreciably contribution of the stellar emission corresponding to the nuclear regions of the host galaxy. We attempt to determine the non-stellar continuum in AGN by means of the spectral synthesis method. By minimization techniques we determine the non-stellar continua (both shape and quantity) of about 160 near (z<0.1) AGN extracted from the SDSS DR8. Our results include determination of black hole masses, accretion rates, ionization state and kinematics for the whole sample. We expect that our work may contribute to the understanding of the innermost regions of AGN, and establish a possible link between the properties of these regions and those of the host galaxies.
Hide Información