Recent Talks

(1) In this talk I will present a recent study of the bar fraction in the Coma Cluster galaxies based on a sample of 190 galaxies selected from the Sloan Digital Sky Survey Data Release 6 and observed with the Hubble Space Telescope (HST) Advanced Camera for Survey (ACS). The unprecedented resolution of the HST-ACS images allows us to explore the presence of bars, detected by visual classification, throughout a luminosity range of 9 mag (-23 < Mr < -14), permitting us to study the poor known region of dwarf galaxies. We find that bars are hosted by galaxies in a tight range of both luminosities (-22 < Mr < -17) and masses (10⁹ < M/M? < 10¹¹). This result holds when compared with a sample of bright/massive field galaxies. In addition, we find that the bar fraction does not vary significantly when going from the center to the cluster outskirts, implying that cluster environment plays a second-order role in bar formation/evolution. The shape of the bar fraction distribution with respect to both luminosity and mass is well matched by the luminosity distribution of disk galaxies in Coma, indicating that bars are good tracers of cold stellar disks. We discuss the implications of our results for the formation and evolution scenarios of bars and disks.

(2) The Herschel Space Observatory was launched on 14 May 2009. After a short commissioning and performance verification period, the science demonstration observations started in September 2009. Herschel is carrying out now routine science observations. The three instruments (SPIRE, PACS and HIFI) are working extremely well. The first results of the many Herschel Key Projects were presented at the ESLAB 2010 conference in ESTEC on May 4-7 2010 and will be published in a special issue of Astronomy and Astrophysics. In this talk I will introduce the observing capabilities of Herschel and will review some of the first results in extragalactic astronomy and in particular those of the Herschel Multi-tiered Extragalactic Survey (HerMES).

We present the new stellar population synthesis models based on the empirical stellar spectral library MILES, which can be regarded nowadays as standard in the field of stellar population studies. The synthetic SEDs cover the whole optical range at resolution 2.3 Å (FWHM). The unprecedented stellar parameter coverage of MILES allowed us to extend our model predictions from intermediate- to very-old age regimes, and the metallicity coverage from super-solar to [M/H] = -2.3. Observed spectra can be studied by means of full spectrum fitting or line-strengths. For the latter we propose a new Line Index System (LIS) to avoid the intrinsic uncertainties associated with the popular Lick/IDS system and provide more appropriate, uniform, spectral resolution. We present a web-page with a suite of on-line tools to facilitate the handling and transformation of the spectra. Online examples with practical applications to work with stellar spectra for a variety of instrumental setups will be shown. Furthermore we will also show examples of how to compute spectra and colors with varying instrumental setup, redshift and velocity dispersion for a suite of Star Formation Histories.

Among the over 450 known exoplanets, the planets that transit their central star stand out, due to the wealth of information that can be gained about both planet and central star. The CoRoT mission has been designed to detect smaller and longer-periodic transiting exoplanets than can be found from ground observations. CoRoT-9b was detected by the satellite in summer 2008 and underwent follow-up observations from ground for another year. It stands out as having the largest periastron distance of all transiting planets, being expected to maintain permanently a moderate surface temperature, estimated between 250 and 430K. It is also the first exoplanet to which planet evolution models can be applied, without uncertain corrections that have been needed for 'hot' transiting planets. These models indicate it to be rather similar to Jupiter. Temperate gas-giant planets with low-to-moderate eccentric orbits constitute the largest group of currently known planets; they are probably similar to the gas giants of the solar system. With CoRoT-9b being this group’s first transiting planet, it may give rise to a much better understanding of these common planets. While CoRoT-9b itself is certainly not habitable, moons around it could be similar to Titan and provide some chance of habitability. Upcoming observations with the Spitzer space telescope are designed to improve on planet parameters and to perform a deeper search for the detection of its moons.

The quiet Sun (the 99%, or more, of the solar surface not covered by sunspots or active regions) is receiving increased attention in recent years; its role on the global magnetism and its complexity are being increasingly recognised. A picture of a rather stochastic quiet Sun magnetism is emerging. From these recent works, the quiet Sun magnetism is presented as a myriad of magnetic field vectors having an isotropical distribution with a cascade of scales down to the mean free path of the photon. But this chaotic representation also shows clear signs of intermittency: at a low frequency rate (0.022 events h^-1 arcsec^-2) the magnetic field appear in the quiet Sun forming well-organised loop structures at granular scales. More interesting, these loops rise to higher layers and their energy input into the chromosphere can be important for the heating of this layer. In the talk, I will present a pedagogic view of the quiet Sun magnetism. I will focus on the ascent of the smallest ever observed magnetic flux emergence through the solar atmosphere. More specifically, I will show how to infer from high resolution, spectro-polarimetric observations (taken with the SOT instrument onboard Hinode) the magnetic topology of the fields, how they rise through the photosphere to the chromosphere, and the implications of this phenomena for chromospheric (and coronal) heating.