Últimas charlas

Todas las charlas en el archivo, ordenadas por fecha.


olga_maryeva_181213s
Thursday December 13, 2018
Olga Maryeva
Astronomical Institute of Czech Academy of Sciences

Abstract

Massive stars (with masses higher than 30 M) undergo the mass loss during their whole lifes. During hydrogen burning in their cores massive stars demonstrate fast winds with velocity about V∞=2500 km/s and relatively low mass-loss rate about 10 -7-10-6 M/year. At the same time, after the end of core hydrogen burning stars become less stable and mass-loss rate increases, stars move to the stage of Luminous Blue variable (LBV). LBVs are relatively short evolutionary stage in life of massive stars, during which they lose significant amount of mass through strong stellar winds and occasional giant eruptive events. As a result, they shed their outer layers and eventually become hydrogen-deficient Wolf–Rayet stars. Massive stars with 25-40 Mreach LBV stage after being red supergiants i.e. reaching cool end on Hertzsprung– Russell diagram, more massive stars became LBV right after blue supergiants phase. Consideration of the initial mass function leads to conclusion that LBV stars are extremely rare and there should be no more than a few dozens such objects in the Galaxy. Detection of LBV- like shells may be considered an indication of that their associated stars are massive and evolved. Searches for such shells using the infrared surveys resulted in the discovery of many dozens of such shells, while follow-up spectroscopy of their central stars led to the discovery of dozens of new candidates to LBVs. In the talk I will tell about properties of nebula around post-LBV star GR290 and about estimated parameters of couple of stars with LBV-like shells, and discuss that at least in some cases the envelope loss occurs before LBV stage.

Frantisek_Duris_181210s
Monday December 10, 2018
Frantisek Duris
Comenius University in Bratislava

Abstract

In this talk, I will briefly introduce Slovak instrument AMOS - all-sky meteor orbit system. We designed and developed a GUI tool for calculating and visualizing trajectories of meteors in Earth's atmosphere and Solar system from multiple-station observations. The current version of the program includes calculation of 1) atmospheric trajectory and velocity, 2) Solar system trajectory, 3) photometric mass, 4) dark flight and impact, 5) Monte Carlo simulation of errors. The program is written in Lazarus/Object Pascal and can be run under Windows as well as Linux systems. Numerical simulations and graphical outputs are produced in R.
In the second part of the talk, I will discuss the python-based photometry pipeline by Mommert (2017) for reducing 4-colour MuSCAT2 images. We implemented several modifications to significantly increase the number of successfully reduced images. I will discuss how the modifications combine data through colors as well as time to obtain more results.


Chiara_Feruglio_181204s
Tuesday December 4, 2018
Dr. Chiara Feruglio
INAF Observatory of Trieste

Abstract

Why did galaxies stop forming stars? Why do black holes in galactic nuclei have masses proportional to bulge masses? What are the physical mechanisms leading the transition from gas-rich, star-forming galaxies, to red gas-deprived passive galaxies? Theoretical models predict that AGN should play a major role in this co-evolution, by driving super winds that are eventually able to remove gas from galaxies, thus quenching star-formation and preventing them from over growing.  
Today’s flagship Instruments - like ALMA and MUSE/VLT - allow to routinely detect AGN-driven massive winds, and to spatially resolve and measure their main parameters. AGN driven galactic winds seem a widespread feature in AGN host galaxies in the local universe, with mounting numbers also in the distant universe.  
But questions arise about their net impact on the surrounding ISM, on the relative importance of quenching versus stimulating star-formation, on the removal of the gas reservoirs from the disks of the host galaxies. 
Do we really understand the interplay of these AGN super-winds with the ISM of the host galaxy, and -perhaps more importantly- with the entire AGN/host galaxy/circum-galactic medium (CGM) ecosystem? I will discuss both observational and theoretical recent results on this topic - and highlight possible strategies to progress. 


ruben_fechiani_181203s
Monday December 3, 2018
Rubén Fedriani
Dublin Institute for Advanced Studies (DIAS)

Abstract

In contrast with low-mass young stellar objects (LMYSOs), very little is known about high-mass YSOs (HMYSOs). Latest results indicate that HMYSOs might be born in a similar way as LMYSOs, i.e., through disc accretion and jet ejection. HMYSOs are deeply embedded in their parent cloud and are at kpc distance, hindering direct imaging of their accretion discs. Jets then become essential to understand the physical properties of the central source. High-resolution near-IR VLT instruments allow us to study HMYSO jets down to au scales and compare them with the low-mass regime. In this talk, I will present VLT/ISAAC, SINFONI, and CRIRES results on two HMYSOs. Spectro-astrometry is used to retrieve information about the jet down to mas scales (~tens of au at kpc distance). High-resolution spectroscopy allows us to retrieve the kinematic and dynamic properties of the massive jets. Additionally, HST imaging in the [FeII] shows the jet structure close to the star. Finally, these properties are compared with low-mass jets, suggesting that the formation of HMYSOs might be a scaled-up version of their low-mass counterparts, and their properties scale with mass.


Klaus_Strassmeier_181130s
Friday November 30, 2018
Prof. Klaus G. Strassmeier
AIP

Abstract

The demand of high-res spectroscopy had seen a tremendous increase after the discovery of exoplanets. Such instruments are now among the standard equipment of nearly every observatory. The latest addition in the zoo is PEPSI, the new bench-mounted fiber-fed and stabilized “Potsdam Echelle Polarimetric and Spectroscopic Instrument” for the 11.8m Large Binocular Telescope (LBT). It covers the entire optical wavelength range from 383 to 914 nm in three exposures at resolutions of either R=λ/Δλ=50,000, 130,000 or 250,000. As of this year, the R=130,000 mode can also be used with two dual-beam Stokes IQUV polarimeters and as such provides another unique capability besides the ultra-high resolution mode. It is also fiber linked to a disk-integration solar telescope and the Vatican Observatory's 1.8m VATT. In this talk I introduce the instrument and focus on first data and results in order to "feel the taste". Among the first targets were the Sun and solar twins, Gaia benchmark stars, Jupiter's Io, planet-host stars with hot Jupiters as well as stars with Earth-sized planets, novae, the ISM, and much more.


Fernando_Buitrago_181128s
Wednesday November 28, 2018
Fernando Buitrago
Institute of Astrophysics and Space Sciences (IA)

Abstract

There are galaxies that remain untouched since the ancient
Universe. These unique objects, the so-called relic galaxies, are several times
more massive than our Milky Way but with much smaller sizes, and
containing very old (>10 Gyr) stellar populations. For the very few of
them already found and analysed (most of them by our IAC colleagues),
they seem to host "too heavy" central
super massive black holes, also displaying an overabundance of low mass
versus high mass stars and retaining their primeval morphologies and
kinematics. How did they survive until the present day? Simulations
predict that they reside in galaxy overdensities whose large internal
random motions prevent galaxies from merging. However, we have not yet
determined observationally neither the environments these galaxies
inhabit nor how many there are (their number densities). We make use
of the GAMA survey, that allows us to conduct a complete
census of this elusive galaxy population, because of its large area and
spectroscopic completeness. After inspecting 180 square degrees of the sky
using the deepest photometric images available, we identified 29
massive ultracompact galaxies in the nearby Universe (0.02 < z < 0.3),
that are true windows to the ancient Universe. I will present the first paper
about this exceptional sample, describing their properties and
highlighting the fact that while some galaxies seem to be satellites
of bigger objects, others are not located in clusters, at odds with the
theoretical expectations.


Nacho_Trujillo_181127s
Tuesday November 27, 2018
Dr. Nacho Trujillo
IAC

Abstract

The faint glow produced by the stripped stars of the galaxies within clusters is shown to follow the dark matter distribution with extreme accuracy. In this contribution, we will show how the Intra-Cluster light can be used to trace the dark matter distribution of galaxy clusters just using deep imaging. This finding opens up the possibility of exploring the distribution of dark matter in hundreds of galaxy clusters and test the current LCDM paradigm.


nick_cox_221118_181122s
Thursday November 22, 2018
Dr. Nick Cox
ACRI-ST

Abstract

The composition and nature of interstellar dust grains and the molecular composition of interstellar gas are important factors in understanding the chemistry and physics of the diffuse interstellar medium and its role in star formation and galaxy evolution. In this contribution we present the first results from two VLT surveys studying in detail the nature and properties of interstellar gas and dust in diffuse clouds.

The ESO diffuse interstellar band large exploration survey (EDIBLES) focusses on the atomic and molecular content of the diffuse ISM by probing the lines-of-sight towards ~120 bright OB stars. This survey provides a deep census of interstellar atomic and molecular abundances and diffuse interstellar band (DIB) absorptions in the diffuse/translucent ISM. The goal of EDIBLES is to `reverse-engineer' the physical properties of the carriers of the enigmatic unidentified diffuse interstellar bands as a contribution towards their identification. I will present the first results related to DIB profiles, interstellar hydrides, and the C60 fullerene.

The large interstellar polarisation survey (LIPS) is a medium-resolution spectropolarimetry study with FORS2 (and WHT) to measure the wavelength-dependent polarisation of starlight by aligned interstellar dust grains in ~100 lines-of-sight (a large fraction overlapping with EDIBLES). We investigate the variations (evolution) of dust grains through a parametrised Serkowski-law fitting of these curves. The polarisation spectra are combined with UV extinction curves and modelled simultaneously with a physical dust grain model. We present the first observational results in terms of the Serkowski-parameters as well as the dust modelling of a sub-set of the targets, in particular our study of “single-cloud” sightlines.

Together, EDIBLES and LIPS provide a new comprehensive examination of the molecules and dust properties in a statistically large sample of Galactic sightlines.


Ana_Monreal_Ibero_181120s
Tuesday November 20, 2018
Dr. Ana Monreal Ibero
IAC

Abstract

Diffuse Interstellar Bands (DIBs) are non-stellar weak absorption features of unknown origin found in the spectra of different astronomical objects when they are viewed through one or several clouds of Interstellar Medium. Galaxies other than ours offer the opportunity of study the behavior of DIBs under physical (e.g. radiation field) and chemical (e.g. metallicity and relative abundances) different to those typically found in the Milky Way. This can in turn, put further constrains on the nature of the agents creating these features. Because of their weakness, studies targeting extragalactic DIBs are relatively scarce.  This is a research that will certainly blossom at the E-ELT era. However, we can already start paving the way.

In this talk, we will illustrate how MUSE can help us in this quest. I will use as examples some results on two highly reddened systems. In the first one, AM 1353-272, we established a gradient of DIB strength in a galaxy at more than 150 Mpc (Monreal-Ibero et al. 2015, A&A, 576, 3). In the second one, The Antennae Galaxy, we measured the strength of the l5780 and l5797 DIBs in more than 100 independent line of sights, thus mapping these DIBs in a system outside the Local Group for the first time (Monreal-Ibero et al. 2017, A&A, 615, 33). The distribution of DIB strength was compared with that of atomic hydrogen, molecular gas, and PAHs as traced by the emission in the mid-infrared. In both cases, DIB strength correlates well with extinction, similar to results for the Milky Way.


artie_hatzes_181115s
Thursday November 15, 2018
Dr. A. P. Hatzes
Thuringia State Observatory

Abstract

In 1988 I joined the quest find exoplanets with the radial velocity method. At the time, exoplanet research was virtually unknown, and no extra-solar planets had been discovered. Since then, we have discovered several thousand extra-solar planets found mostly via the radial velocity and transit methods.

Planets with masses as low as the Earth and even in the habitable zone of low mass stars have been detected. We have also taken the first steps to characterize these new worlds in terms of their masses, radii, densities, internal structure and atmospheric composition. This was unforeseen thirty years ago. In my talk I will review the expectations we had when we first started searching for extra-solar planet, he surprises along the way, and what to expect in the future from extra-solar planet research.