Recent Talks
List of all the talks in the archive, sorted by date.
Abstract
El curso tendrá un carácter eminentemente práctico. Tras una breve serie de presentaciones sobre el proyecto Observatorio Virtual y las herramientas de análisis existentes se procederá al desarrollo de casos científicos reales utilizando una metodología VO. El desarrollo de estos casos científicos se realizará bajo la supervisión de personal del Observatorio Virtual Español.
Abstract
Despite speculation that both starburst and nuclear activity in galaxies may be intimately linked via the common triggering mechanism of mergers and interactions, very little is known about the true nature of the link. Thus, the role of AGN in the formation and evolution of galaxies is still not well established. I will present deep Gemini/GMOS imaging observations which are used to investigate the triggering mechanism(s) in a complete sample of radio-loud AGN for which, uniquely, we have quantified the level of both the AGN and star formation activity. I will show results on the proportion of powerful radio galaxies triggered in galaxy mergers and also on the link between the degree of star formation/AGN activity and the interaction status of the host galaxies.
Abstract
El curso tendrá un carácter eminentemente práctico. Tras una breve serie de presentaciones sobre el proyecto Observatorio Virtual y las herramientas de análisis existentes se procederá al desarrollo de casos científicos reales utilizando una metodología VO. El desarrollo de estos casos científicos se realizará bajo la supervisión de personal del Observatorio Virtual Español.
Abstract
El curso tendrá un carácter eminentemente práctico. Tras una breve serie de presentaciones sobre el proyecto Observatorio Virtual y las herramientas de análisis existentes se procederá al desarrollo de casos científicos reales utilizando una metodología VO. El desarrollo de estos casos científicos se realizará bajo la supervisión de personal del Observatorio Virtual Español.
Abstract
We present the results of our systematic search for optically elusive, but intrinsically luminous buried AGNs in >100 nearby (z < 0.3) luminous infrared galaxies with L(IR) > 1011 L⊙, classified optically as non-Seyferts. To disentangle AGNs and stars, we have performed (1) infrared 2.5-35 μ low-resolution (R ~ 100) spectroscopy using Subaru, AKARI, and Spitzer, to estimate the strengths of PAH (polycyclic aromatic hydrocarbon) emission and dust absorption features, (2) high-spatial-resolution infrared 20 micron imaging observations using Subaru and Gemini, to constrain the emission surface brightnesses of energy sources, and (3) millimeter interferometric measurements of molecular gas flux ratios, which reflect the physical and chemical effects from AGNs and stars. Overall, all methods provided consistent pictures. We found that the energetic importance of buried AGNs is relatively higher in galaxies with higher infrared luminosities (where more stars will be formed), suggesting that AGN-starburst connections are luminosity dependent. Our results might be related to the AGN feedback scenario as the possible origin of the galaxy down-sizing phenomenon.
Abstract
Up to now more than 400 extrasolar planets have been discovered, about 60 of them are transiting. Transiting extra-solar planets are particularly interesting, because their masses, diameters, densities and orientations of their orbits can be determined. Observations with the CoRoT Satellite have now turned up 10 transiting extrasolar planets. Although most of them are gas giants, it turns out that each of them is very special, and many of them have surprising properties. An unexpected discovery was for example the detection of emission lines from CoRoT 1b. Other interesting discoveries are CoRoT 2b, a planet orbiting a young star, and CoRoT 3b the first transiting brown dwarf orbiting a main sequence star. While the detection of transiting gas giants is interesting, the ultimate goal of CoRoT clearly was the detection of rocky planets. CoRoT has detected a solar-like star which shows transits that are only 0.03% deep. In this talk it it is demonstrated that this planet is in fact the first planet found outside our solar system from which we can firmly say that it is a rocky planet. New observations of this interesting object even constrain the properties of its exosphere.
Abstract
The Atacama Cosmology Telescope (ACT) has been observing the southern sky in the millimeter range with an angular resolution at the arc-minute level. An analysis of 228 square degrees observed at 148 GHz along a stripe centered at declination -53 degrees reveals the presence of the Silk damping tail in the temperature angular power spectrum of the Cosmic Microwave Background (CMB). This decaying tail becomes truncated by a rising spectrum at scales corresponding to few arcmins (l ~ 3000) whose origin is compatible with a unclustered population of unresolved point sources and some residual anisotropy due to Compton scattering of CMB photons off free electrons (the Sunyaev-Zel'dovich effect). Comparisons with other observations and constraints on different components giving rise to this secondary spectrum are discussed.
Abstract
We present our latest measurement of the SMBH mass function at redshift zero based on detailed structural studies of 1743 galaxies extracted from the B-band Millennium Galaxy Catalogue. Using the empirical correlations between the mass of the black hole and the photometric properties of the spheroid, MBH-L and MBH-n we estimated the SMBH mass of each galaxy and from this construct empirically derived SMBH mass functions. In addition, using a sample of 30 nearby elliptical and spiral galaxies, we will present new results showing the near-IR correlation between bulge properties and SMBH mass.
Abstract
This talk is divided into two related parts. First, we will call your attention to a basic, but often overlooked worrying fact, and presents ways of dealing with it. The fact is: an enormous number of galaxies in surveys like the SDSS have emission lines which are too weak (low S/N) to be classified by usual schemes (ie, diagnostic diagrams). It turns out that most of these are AGN-like, so ignoring them on the basis of low S/N (which most people do) leaves as much as 2/3 of these emission line galaxies unaccounted for. The solution: We present a number of alternative methods to rescue this numerous population from the classification limbo. We find that about 1/3 of these weak-line galaxies are massive, metal rich star-forming systems, while the remaining 2/3 are more like LINERs. In the second part, we revisit the old idea by Binette et al (1994) that post-AGB stars can account for the emission line properties of some galaxies. A "retired galaxy" model is presented and compared to data in the SDSS. We find that about 1/4 of the galaxies classified as LINERs in the SDSS are consistent with this model, where all ionizing radiation is of stellar origin. More dramatically, nearly 100% of weak-line LINERs are perfectly consistent with being just retired galaxies, with no active nucleus. If these ideas are correct, contrary to current practice, relatively few LINERs should be counted as bona fide AGN.
Abstract
When we measure the electron density within an H II region using ratios of emission lines we find characteristic values in the range of 100-300 cm-3. But when we make these measurements using the total luminosity in Hα and the overall radial size of an H II region we find average values in the range 3-10. I will first explain how this discrepancy occurs, and then go on to show some measurements of electron densities in the H II regions of M51 (over 2500 regions) and the dwarf galaxy NGC 4449 (over 250 regions) using the second method, by Leonel Gutiérrez and myself. From these measurements we can infer how the electron density varies with the radial size of an individual region, and how it varies as we move from the center of the galaxy disc to the outside. Some interesting simple global relationships are found, which tell us about the interaction of star forming regions with their surroundings and how this interaction varies across the face of a galaxy.Upcoming talks
- UNDARK kick offThursday October 10, 2024 - 9:15 GMT+1 (Aula)
- TBDDr. Nikki ArendseThursday October 17, 2024 - 10:30 GMT+1 (Aula)
Recent Colloquia
Recent Talks
