May, 26 2016
May, 19 2016
May, 12 2016
May, 5 2016
April, 28 2016
April, 21 2016
April, 14 2016
"Constraining the primordial power spectrum from large to very small scales"
In this talk I will discuss the constraints on the primordial power spectrum (PPS) beyond the simple power-law model. We use CMB and large scale structure (LSS) datasets to look for features in the power spectrum using a knot-spline model and Bayesian model selection. I will also discuss the implications of a relaxed prior for PPS for other cosmological parameter constraints, particularly neutrino constraints. Finally, I will include limits on the abundance of ultracompact minihalos from dark matter annihilation and pulsar timing measurements to constrain the PPS and the inflationary potential at very small scales - orders of magnitude smaller than what is accessible from CMB and LSS surveys.
Mar, 31 2016
Mar, 24 2016
Mar, 10 2016
Mar, 3 2016
Feb, 25 2016
Feb, 18 2016
Feb, 4 2016
Jan, 28 2016
Jan, 21 2016
Jan, 14 2016
Guest talk by Niall MacCrann, University of Manchester.
Cosmology from Cosmic Shear with DES Science Verification Data:
I present the first cosmology results from the Dark Energy Survey (DES), using cosmic shear. Cosmic shear exploits weak gravitational lensing - the tiny distortions of light from distant sources by the gravitational effect of intervening matter. As well as presenting the main cosmological constraints, I'll go over the basics of weak lensing and cosmic shear, including an overview of potential systematic effects. This will hopefully give you an idea of the inside of the sausage factory! I'll also discuss how we can improve our analysis to account for the decreasing statistical errors associated with massive upcoming weak lensing datasets, and give an update on the current state of the DES.
Dec, 17 2015
Dec, 3 2015
Nov 19, 2015
Nov 12, 2015
Special time: 11.30
Guest talk by Francisco Villaescusa-Navarro
Title: Massive neutrino signatures on the large-scale structure of the Universe
Abstract: Neutrinos are described as fundamental particles by the standard model of particle physics. The fact that neutrinos are massive, as demonstrated by neutrino oscillations experiments, point towards physics beyond the standard model. One of the most important questions in modern physics is: what are the neutrino masses? Current tightest constrain on the sum of the neutrino masses arise from cosmological observables. In order to extract the maximum information from current and future surveys, as well as to avoid introducing biases in the values of the cosmological parameters, it is of primordial importance to understand, both at the linear and at the fully non-linear order, the impact that massive neutrinos induce on the distribution of matter, halos and galaxies. In this talk I will present some of the effects neutrinos induce on the Universe large-scale structure, among then the clustering of matter, the clustering of dark matter halos, the abundance of halos, the abundance of voids, their impact on the BAO peak and their effects of the spatial distribution of neutral hydrogen in the post-reionization era.
Nov 5, 2015
Two guest talks:
Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU)
The University of Tokyo Institutes for Advanced Study (UTIAS
The University of Tokyo
Title:Evolution of Massive Galaxies at z~0.5 in the BOSS survey
The dark matter, which accounts ~80% of gravitational matter, is thought to play an important role in the cosmic structure formation as well as the galaxy formation and evolution. The relation between galaxies and their host dark matter halos has been gained a lot of attentions in this decade. For instance, the stellar-to-halo-mass relation (SHMR) at wide range of mass and redshift has been used to constrain the model of galaxy formation and evolution. However, the massive end (log10(M*/Msun)>11.0) of SHMR is not yet well measured, simply because the number density of massive objects is very small and hence the large statistical sample is required.
Now we have in hand the CMASS galaxy sample in the Baryon Oscillation Spectroscopic Survey (BOSS) in Sloan Digital Sky Survey III (2009-2014) which amounts to almost one million galaxies in a huge cosmological volume, allowing us to measure cosmological probes such as the Baryon Acoustic Oscillation scale and the Redshift-Space Distortion from the large-scale galaxy clustering [O(10-100Mpc)]. Meanwhile, the CMASS sample also provides a suitable galaxy sample for galaxy evolution perspective from the small-scale galaxy clustering [O(0.1-1Mpc)].
In this talk, we present our efforts to model the galaxy-halo connection for the BOSS CMASS sample. In particular, we first reexamine the complicated selection criteria using the two magnitude deeper catalog in the Stripe 82 region, where we show that the CMASS sample is incomplete in terms of stellar mass in a redshift-dependent way. Then we present our method based on the subhalo abundance matching by carefully taking care of the selection effects. Our results suggest warning the standard approach based on the Halo Occupation Distribution, and the halo assembly bias could be a key to fully understand the CMASS galaxy-halo connection.
Elena Massara (a guest of Paul Sutter)
SISSA (Trieste, Italy)
Modelling the Large Scale Structure w and w/o massive neutrinos
Neutrino oscillation experiments have shown that neutrinos are
massive, therefore they affect the evolution of structures in the
Universe at the linear and non-linear levels. I will discuss how to
model the non-linear matter power spectrum in a massive neutrino
cosmology, using an extended version of the halo model. I will show
the comparison between these theoretical predictions and the results
from N-body simulations. Cosmic voids are expected to be good
environments to characterise the neutrino-induced effect on the matter
distribution. I will present the results of a numerical study of void
properties that aims to identify these effects. Finally, I will
discuss a model for describing the shape and evolution of void density
Oct 29, 2015
Oct 22, 2015
Oct 15, 2015
Guest talk by Ron Sega
Dr. Ron Sega, former NASA astronaut and professor of systems engineering andVice President for Energy and the Environment at the Colorado State
University will join us to share his space and life experiences, and
take questions about being an astronaut, technical aspects of
missions, and his work as the NASA Director of Operations at Star
Oct 8, 2015
Guest talk by Stefano Anselmi of Case Western Reserve
"TITLE: "Evading non-linearities: Baryon Acoustic Oscillations at the linear point”ABSTRACT
Cosmology has made fundamental progress thanks to the role of standard rulers. The acoustic peak in the Large Scale Structure clustering correlation function is one of them. However, in the era of precision cosmology, its power has been highly challenged by how late time non-linearities distort the correlation function. Fortunately this is not the end of the story! I will explain how we can evade non-linearities identifying a scale in the correlation function, called the “linear point”, that is an excellent cosmological standard ruler: its position is insensitive to non-linear gravity, redshift space distortions, and scale-dependent bias at the 0.5% level; it is geometrical, i.e. independent of the power spectrum of the primordial density fluctuation parameters. Moreover, the linear point increases its appeal as it is easily identified irrespectively of how non-linearities distort the correlation function. Equally relevant, the correlation function amplitude at the linear point is similarly insensitive to non-linear corrections to within a few percent. Therefore, exploiting the particular Baryon features in the correlation function, we propose three new estimators for growth measurements. We perform a preliminary test in current data finding encouraging results and motivating more careful future investigations.
- arXiv reference: http://arxiv.org/abs/1508.01170 “
Oct 1, 2015
Sept 24, 2015
Sept. 17, 2015
Sept. 10, 2015
Aug 27, 2015
Aug 20, 2015