List of all the talks in the archive, sorted by date.
By the time, in 1937, the Zwicky measured the velocity dispersion of the Coma cluster, astronomers somehow got acquainted with the idea that the universe is filled by some kind of dark matter. After almost a century of investigations, we have learned two things about it, (i) it has to be non-baryonic - that is, made of something new that interact with normal matter only by gravitation- and, (ii) that its effects are observed in stellar systems when and only when their internal acceleration of gravity falls below a fix value a0=1.2×10-8 cm s-2. Being completely decoupled dark and normal matter can mix in any ratio to form the objects we see in the Universe, and indeed observations show the relative content of dark matter to vary dramatically from object to object. This is in open contrast with point (ii). In fact, there is no reason why normal and dark matter should conspire to mix in just the right way for the mass discrepancy to appear always below a fixed acceleration. This systematic, more than anything else, tells us we might be facing a failure of the law of gravity in the weak field limit rather then the effects of dark matter. Thus, in an attempt to avoid the need for dark matter many modifications of the law of gravity have been proposed in the past decades. The most successful - and the only one that survived observational tests - is the Modified Newtonian Dynamics. MOND posits a breakdown of Newton's law of gravity (or inertia) below a0, after which the dependence with distance became linear. Despite many attempts, MOND resisted stubbornly to be falsified as an alternative to dark matter and succeeds in explaining the properties of an impressively large number of objects without invoking the presence of non-baryonic dark matter. This suggests MOND is telling us something important about gravity in the weak field limit. In this talk I will review the basics of MOND and its ability to explain observations without the need of dark matter.
BRITE-Constellation (BRight Target Explorer) consists of six nano-satellites aiming to study of variability of the brightest stars in the sky. Austria, Poland, and Canada contribute two spacecraft each all launched into low earth orbits. The satellites have the same structure: they are 20 cm cubes, 7kg mass, with a CCD photometer fed by 3 cm aperture telescopes. The main difference between pairs of satellites is the instrument passband which set to blue (400-450nm) or red (550-700nm). The core scientific objective is to obtain high precision two color photometry, with a time base of up to 180 days, of stars brighter than 4.5 mag in order to study stellar pulsations, spots, and granulation, eclipsing binaries, search for planets and more.
Since the launch of the first two BRITE satellites in February 2013 more than 5 and a half years of experiences in space have been gathered to run the mission and a summary of lessons learned will be presented. By now more than 20 peer-reviewed scientific articles have been published based on data collected by BRITE-Constellation satellites in space and most results presented therein benefitted greatly from supplementary spectroscopy by meter size telescopes obtained on ground.
Two exotic elements have been introduced into the standard
cosmological model: non-baryonic dark matter and dark energy. The success
in converting a hypothesis into a solid theory depends strongly on whether
we are able to solve the problems in explaining observations with these
dark elements and whether the solutions of these problems are unique within
the standard paradigm without recourse to alternative scenarios. We have
not achieved that success yet because of numerous inconsistencies, mainly
on galactic scales, the non-detection so far of candidate particles for
dark matter, and the existence of many alternative hypotheses that might
substitute the standard picture to explain the cosmological observations. A
review of some ideas and facts is given here.
The cutting off of gas supply in galaxies, whether it is exhausted internally or removed forcibly, can have dramatic consequences and are thought to build up clusters dominated by an early-type galaxy population, as observed in the local Universe. In recent years it has become more and more obvious that this transformation starts in moderate overdensities and filaments surrounding and feeding galaxy clusters. Keeping in mind that the environment of a galaxy cluster is the result of continuous hierarchical assembly boasting a wide range of substructures of locally dense environments, we therefore need to ask: Are the observed galaxy (scaling-) relations due to the timing and physics of cosmological structure formation or due to baryonic physics?
To answer this question we need to look beyond the cluster core.
We therefore investigated members (down to 10^8.5 M_sol) of a massive galaxy cluster at z=0.44 out to 3 virial radii. Our observations probe the nearby infall region, central to the topical question of “pre-processing”. The smoking gun of this “pre-processing” are transitional objects, like passive disk galaxies, whose stellar populations and morphologies indicate a recent change in star formation and/or dynamical history. We find a large number of this virialized population at distinct locations. In our exploration of the galaxy stellar mass-size relation (Kuchner+17), we were able to show that the manifestation of the size distribution of the cluster galaxies is due to an outer disk-fading and possible bulge growth that accompanies the varying fraction of star-forming and quiescent galaxies.
Continuing this quest, the Wiliam Herschel Telescope’s new multi-object survey spectrograph WEAVE will run a dedicated survey that focuses on this question of “pre-processing”. WEAVE will map 16 nearby galaxy clusters and their filamentary structure of infalling galaxies out to 5 viral radii. This will allow us to characterize the onset and continuation of galaxy transformation during their infall process toward the cluster center.
The precipitable water vapour (PWV) is the main absorber in the Earth's atmosphere at infrared (IR) and microwave wavelengths. In the last years, the IAC Sky team has been providing real-time PWV data from a monitor based on the GNSS (GPS) technique (GNSS PWV Monitors; GPM). Among other things, the PWV values help in the scheduling of the telescopes with IR instrumentation. The GPM have undergone a continuous process of upgrading. More recently, we have undertaken the PWV forecasting. We will present in the talk a brief summary of the monitors and details of ForO ("Forecasting the Observatories"), the forecasting system for PWV at the Observatories. ForO is based on a mesoscale Numerical Weather Prediction (NWP) model. The ForO system has been validated and calibrated with PWV data from the GPM and will deliver accurate PWV daily predictions for ORM and OT on a 24, 48 and 72 hours windows. This is a definitive improvement to optimize the flexible scheduling for IR observations, in particular for CanaryCAM and EMIR at the GTC.
Abstract: A small group of giants on RGB show anomalously large amounts of Li in their
photospheres. In some cases, Li abundance exceeds stars' natal clouds (A(Li) = 3.2~dex)
suggesting addition of fresh Li during stars' evolution on RGB. However, the mechanism
that is responsible for such large enhancement is not understood. In this talk, I will describe
observational results till date, possible scenarios for its origin and implications to Galactic Li
La diversidad se ha convertido en una virtud indiscutible, contraria al ideal de la perfección uniforme. Partiendo del origen y la naturaleza de la diversidad biológica, se propone discutir ventajas y costes y señalar medios para inducirla o modificarla.
In the last decade we have explored the cosmic depths and found a statistically significant number of galaxies well into the Epoch of Reionization. However, our physical knowledge of these pristine objects remains very scant. Investigating the internal structure, interstellar medium and evolution of early galaxies is the next challenge to understand key processes as the cosmic history of baryons, feedback, reionization and metal enrichment of the intergalactic medium, This ambitious plan can be tackled by combining a new generation of physically-rich, high resolution, zoom simulations with data in the sub-mm bands provided by ALMA. This approach will be soon strengthened by the forthcoming JWST power. I will review the present status and the open questions in the field.
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.
- IllustrisTNG and insights about the evolution of galaxies in different environmentsDr. Annalisa PillepichThursday December 20, 2018 - 10:30 (Aula)
- MUSE-AO view of the starburst-AGN connection: NGC 7130Dr. Johan KnapenTuesday January 8, 2019 - 12:30 (Aula)