Recent Talks
List of all the talks in the archive, sorted by date.
Abstract
Next generation of CMB experiments will require a large number of detectors (few tens of thousands) in order to tackle the challenging detection of primordial polarization B modes. Furthermore, high resolution experiments are needed for a detailed study of high redshift objects including clusters of galaxies, proto-clusters and dusty galaxies. Within this context Kinetic Inductance Detectors (KIDs) are a serious alternative to bolometers at millimetre wavelengths. Indeed, KIDs are naturally multiplexed and compact allowing us to construct arrays of thousands of detectors. Furthermore, KIDs present short time constants (below 1 ms) and have been demonstrated to be background limited on ground based observations. The NIKA camera, made of two matrices (200 KIDs each) operated at 140 and 240 GHz, has been installed successfully at the IRAM 30 m telescope in Pico Veleta, Granada. NIKA has provided the first ever scientific quality astrophysical observations with KIDs. In particular RXJ1347.5-1145, a massive intermediate redshift galaxy cluster at z = 0.4516 undergoing a merging event, has been successfully mapped at 12 arcsec resolution by NIKA. NIKA is a general purpose camera and it can be also used for other astrophysical objectives including for example observations of high redshift galaxies and proto-clusters, and detailed intensity and polarisation mapping of star-forming regions in the Galaxy. NIKA is a prototype of the NIKA2 camera that should be installed in 2015 at the IRAM 30 m telescope. NIKA2 should have 2 frequency bands at 150 and 250 GHz with about 5000 detectors in total and polarisation capabilities. NIKA2 will be well-suited for in-depth studies of the Intra Cluster Medium in intermediate to high redshift clusters and the follow-up of clusters and proto-clusters newly discovered by the Planck satellite. Finally, we discuss the possibility of including KIDs in the next generation of CMB satellites as for example PRISM.
Abstract
About half the baryons in the local Universe could be in the form of a Warm Hot Intergalactic Medium (WHIM). If a large fraction of the gas is ionized, it could produce significant temperature anisotropies in the Cosmic Microwave Background (CMB), generated by the thermal and also the kinematic Sunyaev-Zeldovich effect. We have developed a theoretical framework to describe the mildly non-linear regime of the WHIM that allows us to compute its contribution to CMB anisotropies. We discuss prospective ways of detecting the WHIM contribution using our formalism and discuss our results on PLANCK data and the constraints we set on the WHIM parameters.
Abstract
In this talk I present an overview of the structure, activity and goals
of the Gaia-ESO survey, a large public spectroscopic survey aimed at investigating
the origin and formation history of our Galaxy by collecting high quality spectroscopy
of representative samples (about 105 Milky Way stars) of all Galactic stellar populations,
in the field and in clusters. Briefly, I discuss the most relevant results obtained so far.
In particular, I present our study on the internal kinematics of Galactic globular clusters based on the radial estimates obtained from the survey complemented with ESO archive data.
Abstract
Can weather models be helpful for astronomers? In this talk, I do a revision of the state-of-the-art in numerical weather prediction models and its specific applications for astronomical observatories. In the context of flexible scheduling, the weather prediction models, and the mesoscale models in particular, can give a significant contribution in the management of the observing nights based on the forecasted atmospheric conditions. A prototype for the operational forecasting of the Precipitable Water Vapour above ORM for observations in the Infrared, currently under development, is presented and discussed.
Abstract
Our group is presently conducting an observational campaign, using the 10-meter Gran Telescopio Canarias (GTC), to obtain the transmission spectrum of several exoplanets during a transit event. The GTC instrument OSIRIS is used in its long-slit spectroscopic mode, covering the spectral range of 520-1040 nm, and observations are taken using a set of custom-built slits of various, broad, widths. We integrate the stellar flux of both stars in different wavelength regions producing several light curves and fit transit models in order to obtain the star-to-planet radius ratio Rp/Rs across wavelength. A Markov Chain Monte Carlo (MCMC) Bayesian approach is used for the transit fitting. With our instrumental setup, OSIRIS has been able to reach precisions down to 250 ppm (WASP-48b, V=11.06 mag) for each color light curve 10 nm wide, in a single transit. Central transit timing accuracies have been measured down to 6 seconds.
Here, we will present refined planet parameters, the detection of planet color signatures, and the transmission spectrum of a set of know transiting exoplanets, namely: WASP-43b, HAT-P-32b, HAT-P-12b, WASP-48b. We will also discuss the capabilities and limitations of GTC with current and future instrumentation, and the role of GTC as tool for the follow up of faint Kepler targets. In particular, we will present the GTC observations of the intriguing evaporating planet KIC 12557548b, for which we performed simultaneous color light curves, and a search for alkali elements in its planetary tail. Other setups for observations (Broad and tunable filter photometry) have also been used and will be briefly discussed. The lessons learned from our GTC exoplanet observations will be discussed in the context of the E-ELT future capabilities.
Abstract
Cognitive Astrophysics brings together tools, techniques and lessons learned from fields apparently as far apart as linguistics, philosophy and cognitive psychology, and merges them with modes and methods of understanding and discovery in modern cosmology, galaxy evolution and astrophysics. I will present an illustrated overview of the field from a variety of perspectives, and close with a discussion of "Pentessence" as an example of a globally organizing concept describing self-gravitating systems known to be operating on vastly different physical scales and in apparently disparate astrophysical circumstances.
Abstract
At the end of 2013, the Hubble Space Telescope has started its last flagship program : the "Frontier Fields". In the framework of this project, three of the most powerful space telescopes to date - Hubble, Spitzer and Chandra - will dedicate a large amount of their observing time to observe six galaxies clusters, who act as additional lenses and amplify the light from background sources, including very faint galaxies to the edge of the observable Universe. These images will reach a depth comparable to the "Hubble Ultra Deep Field", but in a cluster field. Abell 2744, the first Frontier Fields target, has been observed by HST since November 1 and the first release has been made public on December 17. We have used this dataset to search for Lyman Break galaxy (LBG) at z>6.5 in the 4.9 arcmin^2 field of view of the WFC3. Several sources have been selected and the highest redshift object is estimated at z=8, called Abell2744_Y1. The amplification factor of this object is relatively modest (mu=1.5). We used our own reduced Spitzer images at 3.6 and 4.5 microns to constrain the Spectral Energy Distribution (SED) of the z=8 galaxy candidate. We computed its properties by SED-fitting using templates with and without nebular emissions. The star formation rate (SFR) in this galaxy ranges from 8 to 60Mo/yr, the stellar mass is in the order of (2.5-10) x 10^9 Mo and the size r=0.35+/-0.15 kpc, and it is consistent with expectations and previous estimates in this range of redshift. The brightness of this galaxy (F160W=26.2 AB) makes it one of the brightest z=8 object to date, and could be observed by current NIR-spectrograph in a reasonable amount of time.
Abstract
Twenty years ago, no one convincingly knew the age or the size of the
Universe to within a factor of two. Ten years ago, everyone agreed on
those same two numbers to within 10%. Today, we arguably have brought
the errors down by another factor of two. But that has led to anxiety
rather than euphoria, renewed interest rather than complacency. The
problem is that there are now two independent, competing methods
giving answers of comparable precision and accuracy:
one is a model-based method using the cosmic microwave background
(the CMB), the other is a geometric, parallax-based method using local
measures of distances and expansion velocities. To within about
two-sigma the methods agree. To within about two-sigma the methods
disagree. And basic physics (a fourth neutrino species, perhaps) hangs
in the balance.
I will discuss how this "tension" arose and how it will soon be
relieved. A tie-breaker has been identified and developed, and it is
now being worked on from the ground and from space.
Abstract
The ΛCDM model predicts that galaxies originate in dark matter haloes, undergoing in their early age a process of continuous merges with other galaxies that determines the first part of their evolution. The frequency of these events decreases with time and their gradual change turns to be internally driven, becoming much slower. Bars, elongated stellar structures in the central regions of galaxies, are known to play an active role in this phase of their evolution, so-called secular.
Bars are fundamentally responsible for the redistribution of matter and the angular momentum of the baryonic and dark matter components of disc galaxies. Different simulations predict that bars get stronger and longer in time, slowing down their rotation speed.
Based on the Spitzer Survey of Stellar Structure in Galaxies (S4G) 3.6 μm imaging, we aim to study the secular evolution of disc galaxies by focusing on their stellar bar parameters. We take a large well-defined sample of about 650 nearby barred galaxies and we infer the gravitational potential from 3.6 μm images. We calculate gravitational torques, the ratio of the maximal tangential force to the mean axisymmetric radial force, in order to obtain a quantitative measure of the bar-induced perturbation strengths. In addition, we estimate the bar strength from the m=2 normalized Fourier density amplitudes and determine bar lengths both visually and by using an ellipse fitting method. Bar morphology and the interplay with spiral arms are studied via image-stacking methods as well.
In this talk I will present the statistical results derived from our measurements, providing observational evidence for the evolution of bars in accordance with the current theoretical predictions. We study bar parameters as a function of the Hubble type, addressing how the different measurements of the bar strength correlate with each other and with the galactic mass. The quality of our data allows us to probe the properties of bars in the Local Universe and connect them to the evolution of other galactic structures.
Abstract
European Research Council (ERC) grants support individual researchers of any nationality and age who wish to pursue their frontier research. The ERC encourages in particular proposals that cross disciplinary boundaries, pioneering ideas that address new and emerging fields and applications that introduce unconventional, innovative approaches. ERC grants are awarded through open competition to projects headed by starting and established researchers - the sole criterion for selection is scientific excellence.
ERC grants are part of the European Horizon 2020 programme for research and innovation. Last December the ERC published the new work programme containing the first ERC calls under Horizon 2020. To gain an overall view of the rules and possibilities, we cordially invite you for an ERC information session.
Upcoming talks
- Properties and origin of thick disks in external galaxiesDr. Francesca PinnaThursday January 16, 2025 - 10:30 GMT (Aula)
- Seminar by Luigi TibaldoLuigi TibaldoTuesday January 21, 2025 - 12:30 GMT (Aula)