List of all the talks in the archive, sorted by date.
CASE (Calar Alto Spectroscopic Explorer) is a new set of instruments for the Calar Alto observatory to unravelling the fine structure of galaxies in the local volume from 3D spectroscopy. CASE represents a new generation of IFS for CAHA that will be explorer in the next six months during the viability study recently approved for the observatory that it is funding by Junta de Andalucía.
The main instrument is planning for the 3.5m telescope and it will be a large field of view integral field optical spectroscopy unit with an intermediate spectral resolution. Other L-IFU will be also studied for the Schmidt telescope. The FoV (3x3 arcmin) and the thousand of optical fibers of CASE will allow us to cover totally most of the galaxies of the Local Universe (distance < 15 Mpc) to map the kinematics, physical and chemical properties of the stellar populations, interstellar medium, and dark matter of galaxies with unprecedented physical spatial scales that range from a few pc in M33 and M31, to less than 100 pc in galaxies of the Virgo cluster.
The intent of this talk is to call the attention of the IAC colleagues to participate in this project.
Following the current debate on the fate of SN-condensed dust grains, I will present a set of three-dimensional hydrodynamical simulations of the interaction of dusty supernova remnants (SNRs) with the shocked winds of neighboring massive stars within young massive stellar clusters (SSCs). As a comparison, I will discuss the evolution of supernova remnants in the diffuse ISM with constant density. Since the hydrodynamics of SNRs is intimately related to the properties of their immediate environment, the lifecycle of dust grains in SNRs within SSCs is radically different from that in the diffuse ISM. Moreover, off-centered SNRs evolving in the steep density gradient established due to a star cluster wind experience a blowout phase: shell fragmentation due to protruding Rayleigh-Taylor instabilities and the venting of SN ejecta. The main finding is that clustered SN explosions will cause a net increase in the amount of dust in the surroundings of young massive stellar clusters.
Gravitational waves (GWs) emitted by binary black hole coalescences provide an excellent opportunity to study General Relativity (GR) in its strong field regime. This GW emission consists on a superposition of different GW harmonics. When the black holes are far apart, the so called quadrupolar harmonic dominates the rest, known as higher harmonics (HMs),which only get triggered during the final merger and ringdown stages of the binary. In this talk, I will show how higher harmonics can be exploited to decode the properties of the binary and the final merged black hole: from its parameters to the properties of its event horizon.
A fully consistent picture of the SNe progenitor evolution can't be found yet. Such scenario increases in complexity as deep and wide surveys, using latest generation instruments, discover new types of transients with unprecedented observational characteristics. For example, the wide heterogeneity observed in interacting transients in the recent years. Still, the nature of these transients is largerly debated: Some are without doubt genuine core-collapse SNe, while others may be giant non-terminal outburst from luminous blue variables. The talk includes my contribution to this topic with data of the recent objects of study and the conclusions extracted from their analysis.
The Milky Way (MW) galaxy is not much different from its faraway cousins. However, our position within the MW allows us to study the properties of its stellar populations with exquisite detail in comparison to extragalactic sources. The bulge of the MW (i.e. the stellar population within ~3 kpc from the Galactic center) is the most massive stellar component of the MW hosting very old stars (>10 Gyr), therefore the study of its stellar population properties can shed light on the formation and evolution of the MW as a whole, and of other spiral galaxies at large.
So far, there is a general consensus on the global kinematic, chemical and structural properties of the bulge populations, however the age, or rather, the distribution of the ages of the stars in the bulge is yet to be completely understood.
We aimed at addressing the questions 'How old is the bulge?' and 'Is there a spatial age gradient in the bulge?' through the determination of the stellar ages in the different fields sparsely distributed within a region of 300 deg² centered on the bulge.
We use images from the VISTA Variables in the Vía Láctea (VVV) survey, based in near infrared passbands, to extract accurate magnitude and color of half a billion stars in the bulge area using point spread function fitting.
The newly derived photometric catalogs, used in addition to probe the extinction towards the bulge, will be made publicly available to the entire community.
The contribution of the intervening disk population along the bulge lines of sight has been detected and removed by using a statistical approach in order to obtain a final stars sample that is representative of the bulge population only.
The determination of the stellar ages in different fields is provided through the comparison between the observations and synthetic stellar population models, which have been carefully tailored to account for the observational effects (i.e. distance dispersion, differential reddening, photometric completeness, photometric and systematic uncertainties).
The simulations leading to the construction of synthetic populations have been carried out by using two different methods: i) a model that uses a spectroscopically derived metallicity distribution functions as prior, leaving the age as the only free parameter; ii) a genetic algorithm that finds the best solution within all possible combinations of age and metallicity (i.e. uniform prior in age and metallicity using IAC-POP/Minniac suite).
We ultimately find that the bulge itself appears to be on average old (>9.5 Gyr) throughout its extension (|l| < 10° and -10° < b < +5°), with a mild gradient of about 0.16 Gyr/deg towards the Galactic center.
The Exoplanet group in Ondrejov, CZ was founded in 2016. The astronomical Institute Ondrejov operates a 2-m telescope equipped with an Echellespectrograph. In the seminar an overview about the potential of our ground based support program for exoplanetary missions will be presented along with first results from 2017/2018 campaign. Furthermore, our institute in cooperation with Tautenburg Observatory and Universidad Catolica de Chile plans to design a new spectrograph for 1.52m telescope at ESO La Silla observatory, Chile which should contribute to candidate vetting process for PLATO in the future and most certainly also for TESS.
Tigre is a 1.2m f:8 RC robotic telescope designed to do spectroscopic monitoring of dynamical processes, mainly in stellar astrophysics, for objects of less than 2" of size and brighter than magnitude 10...11. Its 2-channel (red/blue) echelle spectrograph HEROS has a resolution of 20,000 and covers simultaneously almost the whole range from the near IR to near UV (8800-3800A). It can also be used to determine the exact physical properties of stellar samples of interest, comparing high s/n (80-120) spectra with PHOENIX models and iSpec analysis. The large amount of spectroscopic data ideally serves a large variety of undergraduate and graduate thesis projects. This presentation gives a brief insight into this dedicated, yet economic international project of the universities of Hamburg, Guanajuato and Liege and the opportunities it has to offer to the international community.
The search of Earth-like extrasolar planets approaches a key moment in its history. With the arrival of ESPRESSO (observing already!), the possibility of detecting Earth-like planets around solar-type stars is at last a reality, and the opportunities to characterize earth-like planets and super-Earths are more numerous than ever. High precision radial velocity (RV) measurements (better than 1 m s−1 for instruments like HARPS and HARPS-N) have given astronomers the possibility of detecting and characterizing small exoplanets for a few years, down to the mass of the Earth, when orbiting M-dwarfs at short orbital periods, or a few Earth-masses at longer periods. The arrival of the new generation of instruments (ESPRESSO) brings a revolution in precision, to the level of 5-10 cm s-1, allowing for the detection or characterization of Earth-mass planets at longer orbital periods, in the habitable zone of Sun-like stars. At these levels of precision, signals induced by stellar activity in the RV curves become the most important limiting factor, even in the case of magnetically quiet stars. Stellar activity can induce apparent Doppler shifts of the stellar spectrum, which cause periodic signals that range from less than one to dozens of meters per second. The correct detection and characterization of the different star-induced signals and their effect in the RVs is one of the most important steps to detect and properly characterize low-mass exoplanets, and its importance will greatly increase with increased precision, as even in the case of the quietest stars, these signals will surface. Unveiling the population of small-mass planets in the range of super-Earths and smaller, especially at long orbital periods (close to the habitable zone of their stars and beyond), is a key step to understand the formation of planetary systems. To really paint the full picture of the systems, and accurately derive their parameters, we need to identify and model together the planetary companions and activity signals present in the data. I will present the current state of the field, the challenges and the techniques to overcome them, focusing on the efforts that I have made during the last years.
Inexplicable observations on the Universe prompt cosmologists to propose either ad hoc explanationsas dark matter and energy maintaining general relativity entirely valid, or to propose alternatives togeneral relativity, without evoking dark ingredients . But for the former investigation track,experimental confirmations are missing, and for the latter general relativity continues to predictobservations with exactitude.Confronted with this dichotomy, and with a multi-parametrised cosmology, we consider legitimate alsoto investigate on the nature of the main messenger from the Universe, light, that we stick so far tointerpret as Maxwellian. But the photon in the Standard Model singles out as the only massless freeparticle, and the waves emerge from a linear theory of the XIX century. What if light were to bedescribed by a different theory?Results on testing non-Maxwellian electromagnetism (either massive initiated by de Broglie and Procaor non-linear by Born and Infeld, Heisenberg and Euler) include setting photon mass upper limits fromthe modified Ampère law in solar wind through the Cluster spacecraft , or from frequency dependentgroup velocities of photons from Fast Radio Bursts [2,5]. Future nanosatellite swarms operating in anew radio-astronomy window, 10 KHz - 10 MHz,  might provide a significant contribution.De Broglie formulated a photon mass already in 1922 and in the later year he estimated such mass to belower than 10 -53 kg, surprisingly close to the actual limits established by the Particle Data Group.Meanwhile, an effective photon mass emerges when Lorentz symmetry is broken in (possibly Super-Symmetrised) Standard Model Extensions, as well as bi-refringence and dissipation [3,4].Non-linear effects as polarisation dependent frequency shifts in strong magnetic field in Magnetars havebeen analysed too , but we are now progressing in modelling a general non-linear electromagnetismLagrangian and look whether wave dissipation in vacuum may occur, possibly in presence of abackground field. When wave dissipation is transferred into photon energy description, we cannot avoidconsidering, additional, non-cosmological redshifts.
 Bentum M.J., Bonetti L., Spallicci A.D.A.M., 2017. Adv. Sp. Res., 59, 736. Bonetti L., Ellis J., Mavromatos N.E., Sakharov A.S., Sarkisyan-Grinbaum E.K.G., Spallicci A.D.A.M., 2016. Phys. Lett.B, 757, 548. Bonetti L., dos Santos Filho L.R., Helayël-Neto J.A., Spallicci A.D.A.M., 2017. Phys. Lett. B, 764, 203. Bonetti L., dos Santos Filho L.R., Helayël-Neto J.A., Spallicci A.D.A.M., 2017. arXiv:1709.04995 Bonetti L., Ellis J., Mavromatos N.E., Sakharov A.S., Sarkisyan-Grinbaum E.K.G., Spallicci A.D.A.M., 2017. Phys. Lett.B, 768, 326. Bonetti L., Perez Bergliaffa S.E., Spallicci A.D.A.M., 2017, 14 th Marcel Grossmann Meeting, 12-18 July 2015 Roma, M.Bianchi, R.T. Jantzen, R. Ruffini Eds., World Scientific, 3531. Capozziello S., Prokopec T., Spallicci A.D.A.M., 2017. Aims and Scopes of the Special Issue: Foundations of Astrophysicsand Cosmology, Volume 47, Issue 6. Retinò A., Spallicci A.D.A.M., Vaivads A., 2016. Astropart. Phys., 82, 49.
In symbiotic stars, two different physical regimes of circumstellar
material exist side by side. Around the donor red giant star, there is a
cool and dense conical region of neutral wind. During quiescent phases,
the rest of the wind from the donor is ionized by its companion, in most
cases, a very hot and luminous white dwarf powered by accretion from the
giant's wind. Mass outflow from the majority of cool components in
symbiotic binaries is still not understood well. Some information about
the distribution of circumstellar matter can be obtained by measuring the
neutral hydrogen column densities from Rayleigh scattering along the
multiple lines of sight. I will present the wind velocity profiles derived
from the measured column densities of neutral hydrogen for two quiet
high-inclination symbiotic systems, EG And and SY Mus. The column density
models indicate the wind focusing towards the orbital plane and allow to
investigate the origin of the asymmetric UV continuum light curve profiles
of symbiotic stars.
- Vertical magnetic field on the boundary of an evolving poreMiss Marta Garcia RivasTuesday September 24, 2019 - 12:30 (sala GTC)
- Recursos educativosDavid CalleThursday September 26, 2019 - 10:30 (Museo de la Ciencia y el Cosmos)