| Jan 9 |
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| Jan 16 |
Guangtun Ben Zhu |
The distribution of gas around galaxies – the circumgalactic and intergalactic media – contains signatures of key processes of galaxy formation such as out?ows and accretion, and may account for the majority of baryons in the Universe. Absorption-line spectroscopy is a powerful tool to probe gas properties. SDSS has obtained spectroscopy for ~200,000 quasars, providing a perfect dataset for statistical analyses of absorption lines. I will introduce the new techniques we have developed to model quasar spectra and detect absorption lines. With these new tools, we have compiled a metal absorber catalog of ~50,000 systems. I will present a statistical analysis of these absorber systems and discuss implications for gas flow processes. In addition, our results allow us to measure the Galaxy-Gas correlation out to Mpc scales, linking the gas properties of individual galaxies to their large-scale environment. |
| Jan 23 |
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| Jan 30 |
Fred Lo |
The Mega-maser Cosmology Project (MCP) aims to determine
the Hubble Constant, Ho, to ~3 percent accuracy by measuring the angular
diameter distance to "mega-maser galaxies" that harbor circum-nuclear Keplerian disks
exhibiting powerful water maser emission. Under the MCP,
mega-maser search using the GBT and mapping using the VLBA and GBT have now
identified 10 mega-maser galaxies with distances ranging from 30 Mpc to 140 Mpc,
well in the Hubble flow. A 10% angular diameter distance determination to NGC6264 at 150 Mpc
has been demonstrated. A by-product of the MCP is precise mass determination of the supermassive black-holes (BH) in the
mega-maser galaxies. The mega-maser BH mass results appear to be inconsistent with
the putative M-sigma relationship between black holes and galactic bulges.
The status of the MCP will be described. The current status and recent science of ALMA and other NRAO facilities will
also be presented.
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| Feb 6 |
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| Feb 13 |
Mark Dijkstra |
The standard cosmological model successfully reproduces the observed large scale distribution of matter in the Universe. In contrast, on much smaller scales the process of galaxy formation is still poorly understood. The amount of observational data on intermediate scales - which are often referred to as the circumgalactic medium (CGM) - has increased enormously in recent years. I will discuss our efforts to model the existing data on the CGM in the HI Lyman alpha line, which illustrate that the composition of the CGM is still poorly understood. Fortunately, several instruments will be commissioned in the near future that will allow us to map out the CGM more routinely. Having a more complete & consistent picture of the CGM will revolutionize our understanding of galaxy formation.
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| Feb 20 |
Fabio Governato |
I will show results from cosmological simulations of galaxy formation where
repeated gas outflows remove low angular momentum gas and
transfer energy to the DM. This process solves three long lasting
problems in galaxy formation: the substructure overabundance, the existence of
bulgeless galaxies, and the presence of ubiquitous DM 'cores' at the center of
dwarf field galaxies. II will then discuss the existing challenges to
CDM in the context of alternative models to Cold Dark Matter as WDM and SIDM.
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| Feb 27 |
Irina Zhuravleva |
Current X-ray observatories allow us to obtain mostly upper limits on the level of turbulence in galaxy clusters. Using the XMM-Newton Reflection Grating Spectrometers velocities of ~ several 100 km/s were obtained in the coolest X-ray cluster cores by means of line width and resonant scattering measurements. Chandra and XMM-Newton observations enable us to measure the amplitude of density fluctuations that gives us upper limits on turbulence velocities of the order several 100 km/s. The forthcoming Astro-H mission with its unprecedented spectral resolution
will for the first time provide robust direct constraints on the ICM velocity
field. Measurements of the line width and variations of the line centroid
energy at several distances from the cluster centre can be used to measure
the power spectrum of the full 3D velocity field. Detail study of the line width, line profile and resonant scattering effect , coupled with simulations of radiative transfer, will further constrain the anisotropy and spatial scales of gas motions. Finally, calibration of the mass bias relative to these new observables will provide a reliable way of improving mass measurements based
on X-ray data.
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| Mar 6 |
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| Mar 13 |
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| Mar 20 |
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