Recent Talks

Radiative transfer is underlying physical phenomenon in many astrophysical problems and among the most difficult phenomena to deal with. The main difficulty arises from the non-local and, in general, non-linear coupling of the radiation field and the state of the gas. A variety of numerical methods have been developed so far to solve the NLTE radiative transfer in spectral lines (NLTE line formation problem). An overview of selected methods will be given in the talk. Special emphasize is put on two extremely fast convergent methods: Iteration Factors Method (IFM) and Forth-and-Back Implicit Lambda Iteration (FBILI) that use the so-called iteration factors in an explicit and implicit way, respectively. Although these methods are developed to solve the general non-linear multi-level problem, their basic ideas and properties are demonstrated on the well-known test-problem of the two-level atom line formation under the assumption of complete redistribution.

I will make an overview of the classical pulsating variable stars (i.e. SX Phoenicis, RR Lyrae, Anomalous Cepheids, Classical Cepheids) in our Local Group and beyond. I will focus on the evolution and pulsation theory that drives our interpretation of their observed properties in terms of stellar evolutionary tracers and powerful distance indicators. The analysis of low mass (and thus ancient) variable stars can provide sound constraints in our understanding of how galaxies form and evolve. Particular attention will be devoted to the idea of whether the current dwarf spheroidal satellites (dSphs) of the MW are surviving representatives of the Halo protogalactic fragments (Fiorentino et al. 2015). Furthermore, I will discuss the use of classical Cepheids to calibrate SNIa host galaxies with the aim of accurately measure the local Hubble constant, Ho.
I will discuss in detail the possible exploitation of the public variable star catalogues coming from the ESA Gaia mission and the next quantum leap that will be possible in the near future thanks to full sky project with extremely deep limiting magnitude such as the Large Synoptic Survey Telescope. I will conclude describing the importance of resolved stellar population studies in preparing the era for extremely large telescopes.

 Nuclear activity and intense star formation are two phenomena known to co-exist in a variety of galaxies, spanning several orders of magnitude in luminosity. I will present a compilation of results derived from studies of type 1 and type 2 AGN, using Spitzer and Herschel data that aim at quantifying the effects of the two phenomena in the mid- and far-infrared. I will address the incidence of
star formation in AGN using various mid- and far-infrared indicators, describe diagnostics, and discuss the effects of AGN on the properties of their hosts.

In the first part of the talk, I discuss the chromospheric activity of quiet Sun. The so-called basal flux, the minimum chromospheric emission of main sequence stars, is discussed in terms of magnetic and non-magnetic heatings. The second half of the talk is about variability of the solar cycle. The extended minimum of the last cycle caused speculations about a possible long-term decline in the solar activity. Based on our observations in past 15 years, I argue that the Sun does not cease to generate sunspots in the next cycle. Finally I outline new tools to evaluate chromospheric activities.

The cosmological large-scale structure encodes a wealth of information about the origin and evolution of our Universe. Galaxy redshift surveys provide a 3-dimensional picture of the luminous sources in the Universe. These are however biased tracers of the underlying dark matter field. I will discuss the different components which are relevant to model galaxy bias, ranging from deterministic nonlinear, over non-local, to stochastic components. These effective bias ingredients permit us to save computational time and memory requirements, to efficiently produce mock galaxy catalogues. These are useful to study systematics of survey, test analysis tools, and compute covariance matrices to perform a robust analysis of the data. Moreover, this description permits us to implement them in inference analysis methods to recover the dark matter field and its peculiar velocity field. I will show some examples based on the largest sample of luminous red galaxies to date based on the final BOSS SDSS-III data release.

The amount of data available in image guided medical interventions and surgeries is growing at a rapid rate. More data per device and more devices present during individual procedures result in a situation, where the interventionalist is often overwhelmed by the amount and complexity of the data available. The lack of integration of the varying source of information is due to the lack of adopted standards and is accentuating this problem. The presentation will cover some of the root causes of this situation and discuss possible solutions.

Using ~320h of good-quality Crab data from Feb 2007 to Apr 2014 the MAGIC telescopes measured the most energetic pulsed photons from a pulsar to date. The new results obtained probe the Crab Pulsar as the most compact TeV accelerator known to date. The remarkable detection of pulsed emission up to 1.5 TeV revealed by MAGIC imposes severe constraints on where and how the underlying electron  population produces  gamma-rays  at  these  energies. Such TeV pulsed photons require a parent population of electrons with a Lorentz factor of at least 5E6. These results strongly suggest IC scattering off low-energy photons as the emission mechanism and a gamma-ray production region in the vicinity of the light cylinder, requiring a revision of the state-of-the-art models proposed to explain how and where gamma-ray pulsed emission from 100 MeV to 1.5 TeV are produced. Investigating the extension of the very high-energy spectral tail of the Crab Pulsar at energies above 400 GeV, the pulse profile was found to show two narrow peaks synchronized with those measured in the GeV energy range. The spectra of the two peaks follow two different power-law functions from 70 GeV up to 1.5 TeV and connect smoothly with the spectra measured above 10 GeV by the Large Area Telescope (LAT) on board the Fermi satellite.

The Square Kilometre Array (SKA) project intends to build a radio-interferometer with 1-sq-km collecting area, and thousands of antennas with baselines up to 3000 km, to be hosted in two continents (Africa and Oceania). This will provide tens of times more sensitivity and allow astronomers to survey the entire sky thousands of times faster than any system currently in existence, with the ability to image huge areas of sky in parallel.

Spain is actively participating in the SKA detailed design phase, both at a scientific and technological level. The potential of SKA for fundamental breakthroughs in Astrophysics, Physics, and Astrobiology has made that the Spanish SKA White Book has been published, with more than 125 authors who have summarized in 29 chapters the interest of the Spanish scientific community. At the same time, SKA constitutes a technology tractor for high-impact societal areas. Among the 100 companies and research institutions across 20 countries that are contributing to SKA design, 10 Spanish research centres and 11 companies participate in several work packages (Dishes, Signal & Data Transport, Central Signal Processor, Science Data Processor, Telescope Manager, and Infrastructure). This Spanish technological participation in the SKA, with an estimated financial value of ~€2M, has been officially acknowledged by the SKA Board. Since October 2013 a representative of the Spanish government has been regularly invited to participate in the SKA Board meetings. Furthermore, at the beginning of 2014, the Board of the Spanish Astronomy Infrastructures Network endorsed the recommendation issued by the Radio Astronomy Infrastructures working group on the interest of the scientific community and industry that Spain explores the possibility to join the SKA project as Full Memb er before the construction phase starts. The interest of the Spanish community and industry was restated during the SKA Spanish day held in October 2014 while a new SKA Spanish Industry Day will be organized by CDTI in 2016.

The aim of this talk is providing a retrospective view of the Spanish participation in SKA project and explain the current status of its participation and opportunities of involvement.

In this talk we will review  the SPICA mission and present its current status under the new framework. Optimized for mid- and far-infrared astronomy with a cryogenically cooled ~2.5m telescope, SPICA will achieve high spatial resolution and unprecedented sensitivity in this wavelength domain. It will enable to address fundamental problems in astrophysics ranging from the formation of planets to the star-formation history of the universe.