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2013-05-30T16:00
Distant Galaxies
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1600 |
Taranu, Dan * |
Forming Elliptical Galaxies via Mergers in Groups |
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We present a series of hundreds of collisionless simulations of mergers in groups of spiral galaxies, designed to test whether elliptical galaxies can be formed by multiple mergers in the centers of such groups. Mock observations of the central galaxies are compared to observational catalogues of early-type galaxies from the SDSS and ATLAS3D surveys. The central galaxies' surface brightness profile and ellipticity distributions show marked similarity to local ellipticals. Moreover, the simulated ellipticals have exceptionally tight scaling relations, with the fundamental plane (size, luminosity and velocity dispersion) relation having less than 0.03 dex scatter. Most intriguingly, the fundamental plane shows a 'tilt' with respect to the virial relation comparable to that observed in local ellipticals. These findings suggest that multiple dry mergers could be a key mechanism for the formation of elliptical galaxies, in contrast to the currently favoured scenario of gas-rich binary mergers. |
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1615 |
Côté, Benoit * |
Galaxy Model for Galactic Winds in Cosmological Simulations |
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We present a model to describe the evolution of galaxies and the galactic winds resulting from this evolution. Our model takes into account the chemical enrichment of stellar winds from massive, rotating stars, core-collapse supernovae (Type II, Ib, Ic), hypernovae, stellar winds from low-mass stars on the asymptotic gain branch, and Type Ia supernovae. We test our enrichment model by comparing its predictions with the abundance patterns of 14 chemical elements observed in the Milky Way stars. To do so, we combines the effect of many stellar populations created from the star formation history of the Galaxy. This enrichment model is combined to a galaxy evolution model that includes radiative cooling, star formation, feedback from all the considered stellar phases, and the mass ejection from a galactic wind. Using a semi-analytical prescription to drive galactic winds, we calculate the spatial density distribution of the mass ejected into the intergalactic medium. This model will eventually be used to provide a sub-grid treatment for galactic winds in cosmological simulations to study the enrichment history of the intergalactic medium. |
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1630 |
Weijmans, Anne-Marie |
Integral-field spectroscopy of local nuggets: deciphering their structure and formation history |
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Red nuggets are a challenge for our understanding of galaxy formation and evolution. These compact, quiescent, massive galaxies are at z ~ 2 a factor 2-5 smaller than equally massive local galaxies. What kind of galaxies are these red nuggets, and how do they grow so much in size later during their evolution? To find answers to these questions, we turn to local compact massive galaxies: these rare objects share many properties with high-redshift red nuggets, but due to their lower redshift (z |
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1645 |
Hill, Allison |
Quasars in the Mid-Infrared: The Suburban Real Estate Around a Growing Supermassive Black Hole |
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At the centres of most large galaxies resides a black hole millions of times the mass of our Sun. When dust and gas enter the vicinity of the supermassive black hole, it begins to feed and grow through the formation of an accretion disk. This growing stage is a quasar, and these objects are among the most luminous phenomena in the universe; they ionize gas and sublimate dust in the central parsecs of the accretion disk. Beyond this region, temperatures are low enough that dust and gas can survive. This material reprocesses the UV-optical emission from the accretion disk into thermal mid-infrared continuum. The mid-infrared is also host to a suite of high ionization coronal lines from low-density ionized gas illuminated by the central continuum, and dust features from silicate and graphites. Polycyclic-aromatic hydrocarbons features from star formation in the host galaxy may also be present. Few features are detected in most mid-infrared spectra because of typically low signal-to-noise ratios. By generating spectral composites from 184 Spitzer observations, we boost the signal-to-noise ratio and reveal important features in the complex spectra. We detect high-ionization, forbidden emission lines all templates, PAH features in all but the most luminous objects, and broad silicate and graphite features in emission. We are therefore able to determine how the narrow line region and the torus change with quasar luminosity via a systematic characterization of the continuum and emission features. |
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1700 |
Vernstrom, Tessa * |
The Deepest View of the Radio Universe at 3 GHz |
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We have used the JVLA in the C-configuration to image one primary beam at 3 GHz with 8 arcsecond resolution and 1.0 μJy/beam rms noise near the pointing center. Our image is confusion-limited with confusion noise of ~1.2 μJy per beam rms. This yields the deepest view yet of the radio universe, allowing us a first direct look at the population(s) of μJy radio sources. Our immediate investigation concerns source counts: previous counts below ~300 μJy from numerous surveys at ~1.5 GHz disagree by factors of as much as three. As well, recent results from the ARCADE 2 balloon-borne experiment measured the cosmic radio background at 3 GHz to be several factors larger than that from the integrated surface brightness from current source counts. Our confusion-limited wide-band data allow us to probe the sub-μJy flux density range; using new modeling, P(D) and Monte Carlo Markov Chain statistical techniques we have placed new constraints on the source counts in this range and therefore the background temperature from discrete sources. These results together with the population analysis will give strong leads for deep surveys with SKA prototypes. |
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1715 |
Taylor, Russ |
The Deep Sky at 5 GHz |
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The new broad-band capability of the Jansky Very Large Array provided by the Canadian WIDAR correlator has been used for a long integration mosaic observations to create an ultra-deep, full-polarization image of a small area of the sky at 5 GHz. With a sensitivity of 1 microJy this is the deepest radio image at these frequencies ever created, exploring the radio source population at flux densities well below the regime dominated by classical radio galaxies and Active Galactic Nuclei. We present initial results of the radio sources revealed, including evidence that the spatial distribution of the faintest sources shows structure suggestive of a local cosmic web, and that the microJy sensitivity level marks the transition to detection of polarized emission from a population of sources dominated by emission from magnetic fields in the disks of normal galaxies. |
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