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department of astronomy
mcdonald observatory
hobby-eberly telescope
university of texas
AST 381S





Cosmology and the Galaxy Bispectrum

The bispectrum of the galaxy distribution is the lowest order correlation function sensitive to the shape of structures generated by gravitational instability and it has been recognized as a valuable tool in the determination of galaxy bias and as a probe of the Gaussianity of primordial fluctuations. More generally, the bispectrum can prove to be complementary to the power spectrum in constraining cosmological parameters, as we will show by taking into account the covariance properties relevant for a joint analysis of these statistics in current redshift surveys.



Review of "Probing Dark Energy with Baryonic Acoustic Oscillations at High Redshifts"

In this talk, a paper from members of the HETDEX team will be reviewed. Baryonic Acoustic Oscillations (BAOs) are observed in the power spectrum of galaxies as a remnant of of the photon-electron decoupling era, and contains useful information possibly determines the somewhat enigmatic nature of the dark energy. To extract the information of BAOs from the observed power spectrum, one needs to make the observation and extraction algorithm to be accurate to the sub-percent level. The difficulty of extracting the BAOs from the power spectrum lies in the distortion of the power spectrum by the non-linearity, galaxy-bias and redshift space distortions. In the HETDEX project, "fit and extract" method (FITEX) is used for the extraction algorithm. Amongst the several extraction algorithms considered, (e.g., Blake & Glazebrook 2003, Angulo et al. 2005) FITEX method is unique in the point that it does not require explicit modeling of these non-linear effects. Through the modeling and analysis of the possible non-linearity and distortions, the phenomenological fitting function used for FITEX is found to be accurate to the sub-percent level.



Natural Mechanism for Reheating of the Universe

I will show that reheating of the universe after inflation occurs naturally EVEN WITHOUT explicit couplings between inflaton and matter fields, if there is a non-minimal coupling between inflaton and gravity.



The Texas Supernova Search

Supernovae (SNe) are popular tools to explore the cosmological expansion of the Universe owing to their bright peak magnitudes and reasonably high rates; however, even the relatively homogeneous Type Ia supernovae are not perfect standard candles intrinsically. Their absolute peak brightness must be established by corrections that have been largely empirical. Hundreds of SNe are now found every year, shrinking the statistical errors in the cosmological terms, but most of these distant discoveries do little to further the physical understanding of SNe, which may illuminate unknown systematics.

This talk will describe recent results from the The Texas Supernova Search, a campaign designed to discover not the most SNe nor the most distant SNe, but instead to amass a small collection of well-observed nearby SNe with detailed, multi-epoch spectral observations beginning at the earliest possible phases. For the past two years, we have pointed ROTSE-IIIb's 1.85 x 1.85 degree field of view at nearby galaxy clusters and searched thousands of galaxies, covering hundreds of square degrees on the sky, for supernovae. With ToO time on the neighboring 9.2m Hobby-Eberly Telescope, we have captured SNe spectra at some of the earliest phases ever. I will discuss the implications of these data on the physics of SNe explosions, including the propagation of the burning front and the progenitors of Type Ia supernovae.



29 November 2006
Astronomy Program · The University of Texas at Austin · Austin, Texas 78712
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