Recent Talks

Disks in spiral galaxies consist of stars and gas. The stellar disks show radially an exponential surface brightness distribution (and vertically one resembling an isothermal sheet), with relatively sharp truncations at of order 4 scalelengths. These truncations are most easily seen in edge-on galaxies. The evidence for these truncations and their statistics will be reviewed. Truncations appear to be not only truncations in the distribution of stars, but also in the total density. The origin of these truncations seem related to the maximum specific angular momentum in the material that formed the disks. Disks are extremely flat. The HI-gas often extends beyond the eructations in the stellar disks, but when they do they also show a warp. Again edge-on galaxies show this mostly readily. Analysis shows that the warps start abruptly, just beyond the truncation radius and some other properties also show abrupt changes at the radius of the onset of the warp. This suggests that warps are the result of infall of gas at later times, when the formation of the stellar disks has been completed. The open issue is still that we have not conclusively shown that we can discover the face-on analogs of the truncations we see in edge-on disk. I will outline some recent research I have been involved in and some ideas for further work and collaborations.

The classical idea that globular clusters are the prototypes of simple stellar populations has been revolutionized in the last few years. Multiple sequences of stars have been detected in the colour-magnitude diagram of a number of clusters, mostly thanks to high-precision HST photometry, and the correlation with the chemical properties of different generations of stars has been demonstrated. In this talk, we will first present a summary of the observational picture, and we will then introduce the SUMO project (a SUrvey of Multiple pOpulations). This is a long-term project, lead here at the IAC and aimed at detecting and characterizing multiple populations in a large sample of globular clusters. We will review the scope, the observing and reduction strategy, and the first results. So far, data for more than 30 clusters have been secured, using the wide field imagers available at the 2.2m ESO/MPI and INT telescope, thus covering both hemispheres. We will present a new photometric index which turned out to be very effective in detecting multiple RGBs in nearly all the clusters analyzed so far. The connection with the chemical content of the different populations will be also discussed.

The concordance model of cosmology with its constituents dark matter and dark Energy is an established description of some anomalous observations. However, a series of additional contradictions indicate that the current view is far from satisfactory. Rather than describing observations with new numbers, it is argued that science should reflect its method, considering the fact that real progress was usually achieved by simplification. History, not only with the example of the epicycles, has shown many times that creating new ad-hoc concepts dominated over putting in doubt what had been established earlier. Also critical astrophysicists often believe that lab-tested particle physics has reliable evidence for its model. It is argued instead that the very same sociological and psychological mechanisms have been at work and brought particle physics in a still more deperate situation long ago. As an example, a couple of absurdities of the recent Higgs boson announcements are outlined. It seems inevitable that physics needs a new culture of data evaluation, raw data and source code must become equally transparent and openly accessible.

Traditionally, astronomers study stars and planets by telescope. But we can also learn about them by using a microscope – through studying meteorites. From meteorites, we can learn about the processes and materials that shaped the Solar System and our planet. Tiny grains within meteorites have come from other stars, giving information about the stellar neighbourhood in which the Sun was born.

Meteorites are fragments of ancient material, natural objects that survive their fall to Earth from space. Some are metallic, but most are made of stone. They are the oldest objects that we have for study. Almost all meteorites are fragments from asteroids, and were formed at the birth of the Solar System, approximately 4570 million years ago. They show a compositional variation that spans a whole range of planetary materials, from completely unmelted and unfractionated stony chondrites to highly fractionated and differentiated iron meteorites. Meteorites, and components within them, carry records of all stages of Solar System history. There are also meteorites from the Moon and from Mars that give us insights to how these bodies have formed and evolved.

In her lecture, Monica will describe how the microscope is another tool that can be employed to trace stellar and planetary processes.

The visible survey spectrometers, VIMOS and FLAMES, have need in successful operation for nearly a decade. and within the next few weeks these will be joined by KMOS and near IR mulit-IFU spectrometer. There are also two new instruments in their early design stages, MOONS a near IR Fibre fed spectrometer and 4MOST a visible fibre fed spectrometer. This talk will present these instruments and the observing opportunity that these will provide.

The origin and structure of the Earth's crust is still a major question. Current measurements of the nearby crust are based largely on seismic, gravimetric and electrical  techniques. In this talk, we introduce a novel method based on cosmic-ray muons to create a direct snapshot of the density profile within a volcano (and/or other geological features).  By measuring the muon
absorption along the different paths through an object (volcano, mountain, a fault, ...), one can deduce the density profile within the object. The major feature of this
technique makes possible for us to perform a tomographic measurement by placing two or more cosmic ray detection
systems around the object. Another strong point of this technique is the possibility to carry out fulltime monitoring, since  muons are incessantly arriving, recalling they are
the most numerous energetic charged particles at sea level.

The basis of stellar population modeling was established around 40 years ago somehow
optimized to the technical facilities and observational data available at that epoch. Since then,
it has been used extensively in astronomy and there has been great improvements relating
their associated ingredients in concordance with the development of more powerful computational
and observational facilities.
However, there has been no similar improvements in the understanding about what is
actually modeling neither in improve the modeling itself to include the current technical advances
to obtain more accurate result in the physical inferences obtained from them.
In this talk I present some advances in the subject of stellar
population modeling and how to take advantage of current facilities to obtain more robust
and accurate inferences from stellar systems at different scales
covering the continuum between fully resolved populations to fully unresolved ones in a unified framework.

CARMENES (Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs) is a next-generation instrument being built for the 3.5m telescope at the Calar Alto Observatory by a consortium of German and Spanish institutions. It consists of two separated spectrographs covering the wavelength ranges from 0.5 to 1.0 mum and from 1.0 to 1.7 mum with spectral resolutions R = 82,000, each of which shall perform high-accuracy radial-velocity measurements (~1 m/s) with long-term stability. The fundamental science objective of CARMENES is to carry out a survey of ~300 late-type main-sequence stars with the goal of detecting low-mass planets in their habitable zones. We aim at being able to detect 2 MEarth planets in the habitable zone of M5V stars. The CARMENES first light is expected to occur in Spring 2014.

We report on the discovery of a fourth component in the HD 221356 star system, previously known to be formed by an F8V, slightly metal-poor primary ([Fe/H]= -0.26), and a distant M8V+L3V pair. In our ongoing common proper motion search based on VISTA Hemisphere Survey (VHS) and 2MASS catalogues, we have detected a faint (J = 13.76 ± 0.04 mag) co-moving companion of the F8 star located at a projected distance of ~312 AU. Near-infrared spectroscopy of the new companion indicates an L1±1 spectral type. Using evolutionary models the mass of the new companion is estimated at ~0.08 solar masses, which places the object close to the stellar-substellar borderline. This multiple system provides an interesting example of objects with masses slightly above and below the hydrogen burning mass limit.

Type-Ia supernovae (SNIa) are believed to be thermonuclear explosions of accreting carbon-oxygen white dwarfs that reach the Chandrasekhar mass limit of about 1.39 solar masses. However, the nature of the companion star is still under debate, i.e. to be either a dwarf, a sub giant, or a giant star (single-degenerate channel), or another white dwarf (double-degenerate channel). Both channels have been proposed but their relative frequency remains unclear. We have been exploring regions close to the center of supernova remnants of Galactic SNe to search for the companion of these type-Ia SNe. I will show the very recent results we have found in two Galactic type-Ia SNe.