Recent Talks
List of all the talks in the archive, sorted by date.
Abstract
In this talk we present spectroscopy of asteroids 24 Themis and 65 Cybele in the 2-4 μ region obtained with the NASA 3.5m IRTF telescope. Their spectra are very similar, and present the typical water ice band at 3.1 μ and additional absorption bands in the 3.2-3.4 μ region that can be attributed to solid organics, showing that there is a small amount of water ice and solid organics widely distributed across their surface. Spectra in the 6-25 μ region obtained with SPITZER of 65 Cybele also show that its surface is covered by a fine anhydrous silicate grains mantle as other outer belt asteroids like the Trojans are. This dust mantle, with a small amount of water ice and complex organic solids, is similar to comet surface where non-equilibrium phases coexist. The presence of water-ice and anhydrous silicates is indicative that hydration did not happened or is incomplete, suggesting that the temperatures were always sufficiently low. This is the first detection of water ice and and solid organics in the surface of an asteroid and suggest that these materials are much more abundant than expected in the surface of asteroids with semi-major axis a > 3 AU. The cosmogonical and astrobiological relevance of this discovery will be discussed.
Abstract
Two-dimensional stellar kinematics obtained with the integral-field spectrograph SAURON allow the classification of early-type galaxies into 'slow' and 'fast' rotators, different from their morphological classification into ellipticals and lenticulars. Most fast rotators, including lenticular as well as many elliptical galaxies, are consistent with oblate axisymmetric disk-like systems. On the other hand, the slow-rotator ellipticals show clear deviations from axisymmetry, which can be modeled with our extension of Schwarzschild's orbit superposition method to triaxial geometry. Besides galaxies, I show that Schwarzschild's method can also be used to model in detail globular clusters such as ω Cen and M15. The recovered internal orbital structure of ω Cen reveals besides a signature of tidal interaction, also a central stellar disk, supporting its origin as the nucleus of a stripped dwarf galaxy. The formally best-fit Schwarzschild model for M15 includes an intermediate-mass black hole, but we cannot exclude a model in which dark remnants make up the dark mass in the collapsed core.
Abstract
CALIFA is the largest IFS survey ever performed up to date. Recently started, it will observe ~600 galaxies in the Local Universe with PPAK at the 3.5m of the Calar Alto Observatory, sampling most of the size of these galaxies and covering the optical wavelength range between 3700-7100 Å, using to spectroscopic setups. The main goal of this survey is to characterize the spatially resolved spectroscopic properties (both the stellar and ionized gas components) of all the population of galaxies at the current cosmological time, in order to understand in detail the how is the final product of the evolution of galaxies. To do so, the sample will cover all the possible galaxies within the color-magnitude diagram, down to MB ~ -18 mag, from big dry early-types to active fainter late-type galaxies. The main science drivers of the survey is to understand how galaxies evolve within the CM-diagram, understanding the details the process of star formation, metal enrichment, migrations and morphological evolution of galaxies.
Abstract
For most persistent low mass X-ray binaries (LMXBs) and transients in outbursts the optical emission is dominated by reprocessing of the X-rays in the outer accretion disk. This has severely hampered any dynamical studies and thereby our knowledge of their system parameters. A new avenue opened thanks to the discovery of narrow high-excitation emission components arising from the irradiated companion star. These lines are most prominent in the Bowen region (a blend of N III and C III lines between 4630 and 4650 Å). In this talk I will discuss this new technique, give an overview of the main results of our survey on the optically brightest LMXBs, and discuss the implications for their system parameters. Furthermore, I will point out the main limitations of this technique and how they might be overcome.
Abstract
A new method of imaging in the visible has given the highest resolution images ever taken anywhere. It needs a natural guide star of only 18.5 mag (I band). This talk will show how it can be done on the WHT, the VLT and even on the GTC.
Abstract
Developed since 2006 by the IAC and UPCT, FASTCAM is an optical camera which takes advantage of recently available low noise and fast read-out CCDs (with integration times ~30 ms) to perform speckle imaging of astrophysical sources. At high enough speed rate, the atmospheric turbulence - classically responsible for image degradation , i.e. seeing- can be frozen in the image, which permits us to implement "lucky imaging techniques". In this shared talk, we will review the principle and objectives of the instrument (mainly oriented so far towards the study of brown dwarfs), we will present the results obtained in different campaigns at the NOT and WHT telescopes stressing the effort towards high contrast and high resolution optical imaging potential which can be further enhanced with post-processing techniques. In this talk we will also discuss some ideas for future projects and scientific applications, possibly in conjunction with the GTC.
Abstract
I will present a short introduction to speckle imaging and the so-called speckle holography technique. Subsequently, I will present results of speckle observations with the VLT (NACO) and Keck (NIRC) telescopes. The experiments demonstrate that in the observed targets speckle imaging combined with holographic image reconstruction provides imaging quality that can compete with and even supersede current adaptive optics (AO) imaging systems. Speckle imaging is a way to achieve reliable, high-quality, diffraction limited imaging capacity at relatively low costs. I will discuss what would be the estimated performance of speckle cameras at the WHT and GTC and sketch possible concepts.
Abstract
Using the k-means cluster analysis algorithm, we carry out an unsupervised classification of all galaxy spectra in the seventh and final Sloan Digital Sky Survey data release (SDSS/DR7). Except for the shift to rest-frame wavelengths and the normalization to the g-band flux, no manipulation is applied to the original spectra. The algorithm guarantees that galaxies with similar spectra belong to the same class. We find that 99% of the galaxies can be assigned to only 17 major classes, with 11 additional minor classes including the remaining 1%. The classification is not unique since many galaxies appear in between classes; however, our rendering of the algorithm overcomes this weakness with a tool to identify borderline galaxies. Each class is characterized by a template spectrum, which is the average of all the spectra of the galaxies in the class. These low-noise template spectra vary smoothly and continuously along a sequence labeled from 0 to 27, from the reddest class to the bluest class. Our Automatic Spectroscopic K-means-based (ASK) classification separates galaxies in colors, with classes characteristic of the red sequence, the blue cloud, as well as the green valley. When red sequence galaxies and green valley galaxies present emission lines, they are characteristic of active galactic nucleus activity. Blue galaxy classes have emission lines corresponding to star formation regions. We find the expected correlation between spectroscopic class and Hubble type, but this relationship exhibits a high intrinsic scatter. Several potential uses of the ASK classification are identified and sketched, including fast determination of physical properties by interpolation, classes as templates in redshift determinations, and target selection in follow-up works (we find classes of Seyfert galaxies, green valley galaxies, as well as a significant number of outliers). The ASK classification is publicly accessible through various Web sites.
Abstract
We present recent theoretical and empirical results concerning the accuracy of Cepheid distance estimates based on optical and near-infrared (NIR) Period-Luminosity (PL) relations. In particular, we plan to discuss the dependence of both slope and zero-point on the metal content using a large sample of extragalactic Cepheids. Moreover, we discuss pros and cons of optical and NIR reddening free Period-Wesenheit relations. We also mention the impact that GAIA will have on the precision of the Cepheid distance scale and the role that E-ELT will play in the identification of Cepheids beyond the Local Volume.
Abstract
Teams from industry, universities and institutes across Europe are contributing to the design and development phase of the European Southern Observatory's project to build the world's biggest optical/infrared telescope. I will outline some of exciting scientific prospects for a fully-adaptive 42m telescope, from studying exoplanets to the furthest galaxies, and then show how some of the technical challenges are being addressed. I will place special emphasis on the work UK teams are doing on instrumentation, detectors and adaptive optics.Upcoming talks
- Harmoni IFS Pre-Optics SCT Prototype testsRafael Melgar HernándezFriday April 4, 2025 - 11:30 GMT+1 (Aula)
- Latest Neutrino Achievements and Possible Synergies to Science in the IACProf. Anatael CabreraTuesday April 8, 2025 - 12:30 GMT+1 (Aula)
Recent Colloquia
Recent Talks
