Recent Talks
List of all the talks in the archive, sorted by date.
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Planetary transits have proven to be one of the most efficient means of finding planets outside the Solar system, counting over 2500 exoplanet discoveries. These transiting planets are paramount for the study of exoplanet atmospheres as the stellar light is filtered through the planetary atmosphere during transit and planetary absorption signatures become imprinted on the stellar spectrum. Observations of hot-Jupiter transmission spectra have become increasingly numerous and reliable throughout recent years, allowing detailed constrains on the planet's physical and chemical atmospheric properties, interactions between planet and host star, and planet formation history. While early work relied largely on space-based facilities, ground-based techniques have seen major advances recently and have become instrumental in performing an extensive and comparative study of exoplanet atmospheres. I will review the current state of knowledge, summarize recent results and discuss future prospects of exoplanet characterization, with a focus on the potential of ground-based facilities. In particular, I will present recent and new results by our team on the transmission spectra of hot Jupiters.
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Recent studies have made the community aware of the importance of accounting for scattered light when examining low surface brightness galaxy features such as thick discs. In past studies on thick discs of edge-on galaxies the point spread function (PSF) effects were not taken into account or were modelled with a Gaussian kernel.
We have re-examined results on photometric decompositions of discs in the Spitzer Survey of Stellar Structure of Galaxies (S4G) using a revised PSF model that accounts for extended wings out to more than 2.5 arcminutes. We study 141 edge-on galaxies, so we more than double the samples examined in past studies. This is the largest sample of extragalactic thick discs studied so far.
The main difference between our current fits and those presented in the past is that now the scattered light from the thin disc dominates the surface brightness at levels below 26 mag arcsec-2. This change, however, does not affect drastically any of our previously presented results:
- Thick discs are nearly ubiquitous. They are not an artefact caused by scattered light as has been suggested elsewhere.
- Thick discs have masses comparable to those of thin discs in low-mass galaxies (with circular velocities v_c<120 km s-2) whereas they are typically less massive than the thin discs in high-mass galaxies.
- Thick discs and central mass concentrations seem to have formed at the same epoch from a common material reservoir.
- Approximately sixty per cent of the up-bending breaks in face-on galaxies are caused by the superposition of a thin and a thick disc where the scale-length of the latter is the largest.
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How galaxies form and evolve remains one of the cornerstone questions in our understanding of the universe on grand scales. While much progress has been made by studying galaxy populations out to high redshifts, there is also much to be learned from near-field cosmology ? that is, investigating nearby galaxies in detail using observations of resolved stars. I will highlight some recent results from several projects that are providing new insights into the structure and formation history of the Milky Way and the Magellanic Clouds. First, I will discuss how I am mapping the stellar halos of the Milky Way and the Magellanic Clouds and thereby uncovering clues to their hierarchical buildup. Second, I will summarize results from the APOGEE survey that, in combination with high-resolution simulations, are revealing the chemical structure, evolution and dynamical history of the Milky Way disk. I will end with a brief summary of my recent work with the NOAO Data Lab to create an all-sky catalog of NOAO archive images (the NOAO Source Catalog or NSC).
Upcoming talks
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Recent Colloquia
Recent Talks
