Found 24 talks width keyword galactic structure
I will review the status of our understanding of galaxy formation in the prevailing cold dark matter paradigm. After reviewing the successes and failures of the most natural predictions of this scenario I will focus on the consequences of two of its main predictions: the presence of large numbers of low-mass dark matter halos and the prevalence of accretion events during the formation of normal galaxies. In particular, I will discuss the interpretation of the recent discovery of a population of ultra-faint galaxies in the Local Group, and its relation to the profuse cold dark matter substructure expected in the Galactic halo. I will also discuss the importance that accretion events might have had in shaping not only the stellar halo but also the disk component(s) of the Milky Way.
AbstractWe 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.
AbstractWarps of disk galaxies are ubiquitous. In almost every disk galaxy a bending of the disk occurs where the stars fade away and hence where the dark matter halo becomes dominant. A clear understanding of this phenomenon has not been reached yet. Analysing H I observations of a small sample of symmetric, warped disk galaxies we found that they exhibit a two-disk structure, the warp being the transition from the inner flat disk to an outer, inclined one. At the transition radius, the rotation curve changes. This points towards symmetric warps being a long-lived phenomenon reflecting an internal change in the structure of the Dark Matter halo.
While warps usually occur where the stellar disks fade, examples of extreme warps are known that commence already at the centre of galaxies. One is present in the neutral gas disk of the "Spindle Galaxy "NGC 2685, formerly thought of as being a two-ringed polar ring galaxy. Utilising deep HI observations, we found that the two-ringed appearance is due to projection effects and that it rather possesses one coherent,extremely warped HI disk. Our success in fitting a tilted-ring model to the HI component, and, with that, assuming circular orbits of the tracer material, and the shape of the fitted rotation curve hint towards a rather spherical shape of the overall potential.
AbstractBars 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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