Found 44 talks width keyword galactic formation

Thursday November 13, 2008
Prof. Simon White
Max-Planck Institut für Astrophysik, Garching, Germany


In our now-standard picture for the growth of structure, dark matter halos are the basic unit of nonlinear structure in the present Universe. I will report results from simulations of galaxy-scale dark halos with more than an order of magnitude better mass resolution than any previously published work. Tests demonstrate detailed convergence for (sub)structures well below a millionth the mass of the final system. Even with such resolution the fraction of halo mass in bound subhalos does not rise above a few percent within the half-mass radius. I will also present a new simulation technique which allows structure in the dark matter distribution to be studied on very much smaller scales. This is required for accurate forecasts of the expected signal both in earth-bound experiments designed to detect dark matter directly, and in indirect detection experiments like GLAST which attempt to image dark matter annihilation radiation at gamma-ray wavelengths.

Thursday October 9, 2008
Dr. Juan Antonio Fernández Ontiveros
Instituto de Astrofísica de Canarias, Spain


Starbursts and AGNs are frequently coupled in the central kiloparsecs of Seyfert galaxies, where molecular gas plays a critical role in fueling nuclear starburst activity and feeding the central black hole. Unveiling the dusty nuclear regions with high-spatial resolution techniques in the near-infrared (NIR) permits us to disentangle the AGN and the stellar clusters, characterizing both sources separately. In this context, a small sample of nearby galaxies have been observed with VLT/NaCo adaptive optics in the NIR. These observations were completed with similar high-spatial resolution data in the mid-infrared (VLT/VISIR), optical (HST) and radio wavelengths (VLA). A new alignment for the starburst galaxy NGC 253 was found based on NIR and radio data, due to the high-spatial resolution in both spectral regions, finding NIR counterparts for 8 known radio sources. It is remarkable the lack of any optical or IR counterpart for the radio core, proposed as a low luminosity AGN, which presents an IR-to-radio emission ratio similar (or even lower) than Sgr. A*. Using the high-spatial resolution aligned dataset from optical-IR to radio wavelengths we derived a representative spectral energy distribution (SED) based on 37 young dust embedded clusters resolved in the inner 0.4 kpc. The template is characterized by a maximum at 20 μ and a gentle bump in the 1-2 μ range. These features, absent in lower spatial resolution templates, can be well reproduced by considering an important contribution of very young stellar objects to the IR, and are thus associated with hot dust surrounding the protostars. The average SED was then compared with the nuclear star forming regions found in the Seyfert 2/starburst galaxy NGC 7582.

Thursday September 18, 2008
Dr. Christopher Conselice
University of Nottingham, UK


We examine the latest results concerning the evolution in the structures of galaxies from the local universe up to z ~ 6. We present results from the COSMOS, EGS and UDF surveys and characterise the structure of galaxies in terms of stellar masses. We find in general that galaxy structure becomes more asymmetric with time, and we use this information to determine the merger history of galaxies and the role of mergers in galaxy formation, placing the first firm constraints on the importance of this formation mode.

Thursday June 19, 2008
Prof. Ronald Buta
University of Alabama, USA


Bars are important engines for the evolution of structure in galaxies. Bars can cause secular evolution of both the gas and stellar distributions in galaxies, and recently it has been suggested that bars may be recurrent features, forming, dissolving, and reforming over a Hubble time. Models also have suggested that the strength of bars depends on how effectively the bar can transfer angular momentum to outer halo material. Evaluating current models requires an effective way of quantifying the strengths of bars. In my presentation, I will describe recent attempts to use gravitational torques implied by near-infrared images as a means of quantifying both bars and spirals in disk galaxies. I will also describe some of the recent findings based on Fourier analysis of early-type galaxy bars.

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