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2013-05-28T14:00
Cosmology
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1400 |
Hinshaw, Gary |
21 cm Observational Cosmology |
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I will present an overview of 21 cm cosmology with an emphasis on measurements in the redshift range z~1-2 with the forthcoming Canadian Hydrogen Intensity Mapping Experiment (CHIME). CHIME is a new 'digital' radio telescope, funded by CFI, and being developed collaboratively by McGill, U. Toronto, UBC, and the Dominion Radio Astrophysical Observatory (DRAO). CHIME will map the northern sky in the frequency range 400 - 800 MHz with the goal of mapping redshifted 21 cm emission in the redshift range 0.8 < z < 2.5. These data may be used to measure the baryon acoustic oscillation feature in the matter distribution, which in turn may be used to constrain the expansion history of the universe in the epoch when dark energy became the dominant component in the universe. I will describe the design and implementation of CHIME. |
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1430 |
Addison, Graeme |
Cosmological constraints from BAO and large-scale structure clustering |
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I will discuss cosmological constraints from baryon acoustic oscillations and large-scale structure (LSS) clustering measurements, and show that we are now able to make meaningful comparisons between different low-redshift cosmological probes even in the absence of CMB anisotropy constraints. I will show that the LSS data exhibit qualitatively the same tension with type IA supernovae measurements and distance ladder H_0 constraints as found by Planck for a LCDM model, albeit at lower significance. I will then discuss why comparing results from dark energy probes both with and without the inclusion CMB constraints can be useful as data precision continues to improve. |
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1445 |
Masui, Kiyoshi * |
21 cm Intensity mapping with the Green Bank Telescope |
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I will describe observations of z~0.8 21 cm intensity fluctuations using the Green Bank Telescope, which serves as a pilot survey for dedicated 21 cm experiments such as CHIME. We have been able to clean foregrounds from the observed volumes close to the level of the expected signal. A cross-correlation with WiggleZ galaxies unambiguously demonstrates cosmological signal. The auto-correlation contains both signal and residual foregrounds. I will discuss the interpretation of the auto-power, in conjunction with the cross-power, to constrain the amplitude of the signal and hence cosmic neutral hydrogen abundance and clustering. |
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1500 |
Ford, Jes * |
Cluster Masses from Magnification in CFHTLS Wide |
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The magnification component of the weak lensing signal provides additional and complementary information to a shear measurement of dark matter halo profiles. While low redshift halos are better constrained by shear, at increasingly high redshifts magnification becomes quite competitive in signal-to-noise. We present new measurements of cluster masses from the stacked magnification signal of >10,000 galaxy clusters in the CFHTLS Wide fields. We perform a composite-halo fit that accounts for the wide range in mass (richness) and redshift, and discuss some of the challenges faced in interpreting such a signal. |
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1515 |
Ngan, Wayne * |
Using tidal streams to test cosmology |
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Widely known as the "missing satellite" problem, lambda-CDM cosmological simulations of Milky Way-sized dark matter halos predict that there are many more subhalos around us than we observed. Measuring the Milky Way's subhalo mass function (SMF) is an essential step to resolving this problem. It has been shown that tidal streams -- remnants of tidally disrupted stellar systems -- are promising probes to constrain the SMF via the subhalos' small scale perturbations, which are manifested as "gaps", in tidal streams. We simulate tidal streams as N-body stellar systems being disrupted by a galactic potential. The sub-halo mass and encounter distance dependence on the sizes and visibility of gaps in the streams is demonstrated along with a preliminary comparison to data. Upcoming galactic surveys will greatly improve the observational power of these measurements. |
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