Recent Talks

How far can we see galaxies in the distant Universe? When are the first metals and the first dust formed?
We have now the first results on these topics (Laporte et al. 2017, ApJL, 837, 21L) based on the detailed analysis of
a gravitationally lensed Y-band dropout, A2744_YD4, selected from deep Hubble Space Telescope imaging in the Frontier Field
cluster Abell 2744. Band 7 observations with the Atacama Large Millimeter/submillimeter Array (ALMA) indicate the proximate
detection of a significant 1 mm continuum flux suggesting the presence of dust for a star-forming galaxy with a photometric
redshift of z~8. Deep X-SHOOTER spectra confirms the high-redshift identity of A2744_YD4 via the detection of Lyα emission
at a redshift z =8.38.  The association with the ALMA detection is confirmed by the presence of [O III] 88 μm emission at the
same redshift.  Although both emission features are only significant at the 4-sigma level, we argue their joint detection and
the positional coincidence with a high-redshift dropout in the Hubble Space Telescope images confirms the physical association.
Analysis of the available photometric data and the modest gravitational lensing magnification indicates A2744_YD4
has a stellar mass of ∼2 × 10^9 solar mass, a star formation rate of ∼20 solar mass_yr^‑1 and a dust mass of ∼6 × 10^6 solar mass.
We discuss the implications of the formation of such a dust mass only ≃ 200 Myr after the onset of cosmic reionization.

While there may be some possibilities of detecting biological signatures (“biomarkers”) outside the Solar System from the ground, most authorities
believe that major installations in space are required to do so.
In this talk we present the background, a brief summary of possible biomarkers, of possible targets and of the ways and means to observe them.

I will present results from the "Local Volume HI Survey'' (LVHIS), including a multi-wavelength atlas of 82 nearby galaxies. The LVHIS project targets all nearby, gas-rich galaxies with vLG < 550 km/s or D < 10 Mpc that are detected in the "HI Parkes All-Sky Survey" (HIPASS). A declination limit of DEC < -30 degrees was chosen for observations with the Australia Telescope Compact Array (ATCA). The majority of LVHIS galaxies are dwarf galaxies, but we also mapped the disks and outskirts of several very large galaxies (eg M83).
I will also introduce the Australian Square Kilometre Array Pathfinder (ASKAP) which consists of 36 x 12-m dishes, each equipped with Phased-Array Feeds, operating from 0.7 to 1.8 GHz. With a field-of-view of 30 square degr ASKAP is a fast 21-cm survey machine. Early Science with 12 antennas has started and I will present first results on our target field: nearby groups and clusters.

I've heard many times about the Virtual Observatory, but what really is VO? Is it just for IT people?, for data centres?, for astronomers?, for everybody? Who is behind VO? Is the Virtual Observatory sustainable in the medium-term? Was it just a nice idea or is it really having an impact on the way astronomers make science with archive data?
In this talk I'll try to answer all these questions by describing the Spanish Virtual Observatory, an initiative that began in 2004 with the aim of coordinating at national level the VO-related activities in four different fields.
Special focus will be given to usage examples of VO tools for real VO-science projects.

In my presentation I will give a short introduction to the science of extrasolar planets, in particular the technique of transit, eclipse and phasecurve spectro-photometry.  I will describe my various projects in this emerging field using state of the art spectroscopic and photometric instruments on the largest ground based telescopes, the 'flying telescope' SOFIA (Stratospheric Observatory for Infrared Astronomy) and the Kepler and Hubble space telescopes.

Gamma Ray Bursts (GRBs) are among the most energetic transient phenomena frequently followed up by different observatories and yet several fundamental questions are still open. Fermi and MAGIC are continuing their observations of GRBs since several years, giving highest priorities to the most interesting events. This effort led to remarkable discoveries in the High Energy regime, showing potential for even more meaningful achievements in the Very High Energy (VHE) regime. Enhanced follow up strategies of MAGIC and soon to come CTA Large Size Telescopes (LST) observations create unique opportunities for the detection of GRBs at VHE. In this talk I will give an overview of the high energy GRB properties as seen by Fermi and show the potential for the first VHE detection with MAGIC and CTA LSTs.

The identification and investigation of red supergiants (RSGs) in the Local Group and beyond are extremely important for understanding massive star evolution and mass-loss.  Star-forming dwarf irregular (dIrr) galaxies serve as ideal laboratories for investigating physics of red supergiants within the context of different metallicities of host galaxies. Also, RSGs may be used as tracers for abundance determinations and star formation history of dIrrs. I will present a systematic survey of RSGs and luminous blue variables (LBVs) in nearby dIrr galaxies with the goal to complete the census of these objects in the Local Group. Using the fact that RSGs and LBVs are bright in mid-infrared colors due to dust, we applied a technique that allows us to select dusty massive stars based on their [3.6] and [4.5] Spitzer photometry. I applied our criteria to 7 dIrr galaxies: Pegasus, Phoenix, Sextans A, Sextans B, WLM, IC 10 and IC 1613 selecting 124 point sources, which we observed with the VLT/FORS2, GTC/OSIRIS and duPont/WFCCD spectrographs. In total, we identified 28 RSGs (21 are new discoveries) and 2 new emission line objects in these galaxies. These new discoveries are statistically significant and this sample increased the number of spectroscopically confirmed RSGs in dIrrs by 50%. Moreover, for the newly identified RSGs we measured the fundamental physical parameters by fitting their observational spectral energy distributions with MARCS stellar atmosphere models. This work serves as a basis for further investigation (also in a framework of my activity in IAC) of the newly discovered dusty massive stars and their host galaxies.

After a basic introduction into asteroseismology for the non-expert, we emphasize how to achieve practical applications of the technique based on uninterrupted high-precision data from space. We show how series of detected and identified oscillation modes allow to deduce details of the interior physics of stars that are impossible to unravel in any other way. We highlight the most recent findings on the interior rotation and chemical mixing of stars with a convective core and illustrate how these affect stellar evolution theory. We reveal the power of combining Gaia and asteroseismic data for stellar physics, galactic archeology, and exoplanet studies. Finally, we provide an outlook for future projects in asteroseismology to illustrate the bright future of this research domain.

I give an overview of our spectroscopic work on the old open cluster M67 and what it may tell us about the origin of the Sun, the existence of terrestrial planets around solar twins and effects that change the surface composition of stars. I will argue that much remains to be learned from studies of stars in different environments (globular clusters, open clusters, associations).

The standard cosmological model has been established  and its parameters are now measured with unprecedented precision. However, there is a big difference between modelling and understanding.  The next decade  will see the era of large surveys; a large coordinated effort of the scientific community in the field  is on-going to map the cosmos producing an  exponentially growing amount of data. This will shrink the statistical errors. But precision is not enough: accuracy is also crucial.   Systematic effects may be in the data but may also be in the model used in their interpretation.  I will present a small selection of examples where I explore  approaches to help the  transition from precision to accurate cosmology. This selection is not meant to be exhaustive or representative, it just cover some of the problems I have been working on recently.