Found 15 talks width keyword galactic dynamics

Tuesday April 22, 2014
Dr. Martin Stringer
Instituto de Astrofisica de Canarias


Any viable theory of the formation and evolution of galaxies should be able to broadly account for the emergent properties of the galaxy population, and their evolution with time, in terms of fundamental physical quantities. Yet, when citing the key processes we believe to be central to the story, we often find ourselves listing from a vast and confusing melee of modelling strategies & numerical simulations, rather than appealing to traditional analytic derivations where the connections to the underlying physics are more tangible. By re-examining both complex models and recent observational surveys in the spirit of the classic theories, we will investigate to what extent the trends in the galaxy population can still be seen as an elegant fingerprint of cosmology and fundamental physics.

Thursday June 7, 2012
Dr. Juan Uson
observatoire de Paris - LERMA


Superthin galaxies are bulgeless, late-type spiral galaxies seen edge-on.  HI synthesis observations probe the kinematic structure of their interstellar medium.  Observations of these isolated, quiescent galaxies have reached column densities as low as few x 1018  atoms . cm-2 .  The simple structure of the superthins makes them ideal cosmological laboratories (Uson and Matthews 2003). The strength of the cosmic UV background has a strong influence on the formation of structure in the Universe, from the inhibition of the collapse of small haloes to the ionizing escape fraction in galaxies to the global star formation history.  We have used the VIRUS-P integral-field spectrometer on the University of Texas McDonald Observatory 2.7m telescope to observe the edge of the superthin galaxies UGC7321 and UGC1281 in the Hα emission line, limiting the strength of the local UV background below theoretical expectations (Adams et al., 2011).  New,  observations (March 2011) have improved the sensitivity significantly.  The Hα layer shows a peak brightness of  Σ = 1.0 x 10-19 erg s-1 cm-2 arcsec-2 Å-1 (~7σ)  for spectra smoothed with a 15″ spatial kernel.  This leads to a measurement of the cosmic UV background induced HI photoionization rate Γ = 2.0 x 10-14 s-1 (~7σ, preliminary absolute calibration, Uson et al, BAAS 44, 312-01, 2012).  Contrary to past observational attempts, our measurements covered a large, two-dimensional on-sky area. We reach flux limits that are ~50 times fainter than the sky background with significant smoothing over spatial elements and a sky background model that accounts for variations in the spectral resolution of our instrument.

Tuesday August 2, 2011
Dr. Carlos González Fernández
University of Alicante, Spain


With the discovery of several massive, young clusters in the last five years, the area around the base of the Scutum-Crux arm (around l=28) has become one of the more intense stellar formation areas in the whole Galaxy. This is not totally unexpected, as it is just there where it was predicted that the long bar of the Milky Way would come into contact with the disk, triggering stellar formation. With this talk we review all these evidences and we bring others into light, as we try to obtain a clearer picture of what is happening in these areas and what does it tell us about the inner structure of the Galaxy, particularly of the bulge+bar complex.

Friday July 29, 2011
Dr. Victor Debattista
University of Central Lancashire, UK


In recent years it has become clear that stars can migrate across large regions of the disk without increasing substantially the velocity
dispersion.  I review the theory and consequences of migration and discuss
some of the evidence supporting the occurrence of stellar migration,  including in the Milky Way's thick disk.

Thursday June 30, 2011
Prof. Scott Tremaine
Institute for Advanced Study, Univ. Princeton, USA


The massive black holes found at the centers of most nearby galaxies including our own, are believed to be the ashes of the fuel that powered quasars early in the history of the universe. I will briefly review the astronomical evidence for these objects and then describe some of the exotic dynamical phenomena that originate in their vicinity, including hypervelocity stars, resonant relaxation, and warped and lopsided stellar disks.

Friday June 17, 2011
Dr. Mauro D'Onofrio
University of Padova, Italy


We present the K band FP of the ETGs members of the clusters observed by the WINGS survey. The data confirm a different tilt of the FP with respect to the V solution and the presence of a substantial tilt in the K band. This led us to further investigate the hypothesis that ETG non-homology greatly contribute to the tilt of the FP.

The WINGS data show that there are now several evidence of both structural and dynamical non-homology for the class of ETGs. Among these we will discuss in detail the tight relation between the mass of the ETGs, their stellar mass-to-light ratio M/L, and the Sersic index n describing the shape of their light profiles. We guess through a series of mock simulations that this relation acts as a fine-tuning that keeps small the scatter around the FP. We therefore conclude that ETG non-homology is closely connected either with the problem of the tilt and with the small scatter around the FP.

Tuesday May 24, 2011
Dr. Alexandre Vazdekis
Instituto de Astrofisica de Canarias, Spain


We find a distinct stellar population in the counterrotating and kinematically decoupled core of the isolated massive elliptical galaxy NGC 1700. Coinciding with the edge of this core, we find a significant change in the slope of the gradient of various representative absorption line indices. Our age estimate for this core is markedly younger than the main body of the galaxy. We find lower values for the age, metallicity, and Mg/Fe abundance ratio in the center of this galaxy when we compare them with other isolated elliptical galaxies with similar velocity dispersion. We discuss the different possible scenarios that might have lead to the formation of this younger kinematically decoupled structure and conclude that, in light of our findings, the ingestion of a small stellar companion on a retrograde orbit is the most favored.

Tuesday May 17, 2011
Dr. Martín López Corredoira
Instituto de Astrofísica de Canarias, Spain


Milky Way and most spiral galaxies present some features in the outer part of its disk such as S-warping or U-warping, flaring, lopsidedness, truncation/non-truncation and others, both for the stellar and the gas component. In the present talk, I will review some of the galactic dynamics hypotheses which try to explain these features: either in terms of gravitational interaction, magnetic fields, accretion of intergalactic matter or others. The gravitational interaction may be among the different components of the galaxy or between the spiral galaxy and another companion galaxy. The accretion of intergalactic matter may be either into the halo, with a later gravitational interaction between the misaligned halo and the disc, or directly onto the disc. The phenomena of the outer disc in spiral galaxies might be produced by more than a mechanism. Nonetheless, the hypothesis of accretion of intergalactic matter onto the disc presents several advantages over its competitors, since it explains most of the relevant observed features, whereas other hypotheses only explain them partially.

Tuesday April 12, 2011
Dr. Rafael Barrena
Instituto de Astrofísica de Canarias, Spain


Extended, diffuse radio emission (halos and relics) in galaxy clusters is a rare phenomenon. The origin of these radio sources and their connection with cluster mergers is still being debated. Here we present the results of the DARC program, aimed to the internal Dynamics Analysis of ”Radio” Clusters and mainly based on a long-term TNG-INT program (20 clusters at z=0.1-0.3). The study of kinematics of member galaxies show that DARC clusters are examples of very substructured systems and allow us to detect and weight the interveining subclusters, as well as to obtain infor- mation about their relative motions and the merger geometry. The multiwavelength observational picture (optical, radio and X-ray) of DARC clusters is well interpreted in a scenario of a recent, major cluster merger.

Thursday March 17, 2011
Dr. Alber Bosma
Astronomy Observatory of Marseilles Provence, OAMP, France


Dark Matter in Galaxies is an important subject of current astrophysical research. I will concentrate on spiral galaxies, and first give an overview of the subject from the standpoint of a radioastronomer with a long involvement in the subject. This includes a historical introduction and a review of some of the present-day debates. The currently popular Lambda-CDM model has problems on the scale of galaxies. In a second part I will address more specifically the problem that we still do not know how much dark matter there is in spiral galaxies, and how it is distributed. This is due to the fact that the M/L of the visible matter is poorly constrained and that there is a 'conspiracy' between the dark and the baryonic material. I will present various dynamical methods that have been proposed to constrain the dark matter mass distribution and discuss their advantages and disadvantages.

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