CCAPP Cosmology Lunch meets on Thursdays at 12:30 pm in the Price Place (PRB M2005).

Nov 19, 2015

Nov 12, 2015
        Special time: 11.30
        Guest talk by Francisco Villaescusa-Navarro
        Trieste, Italy 

        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:
        Shun Saito
        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
        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 and
        Vice 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
        City, Russia.

Oct 8, 2015

    Guest talk by Stefano Anselmi of Case Western Reserve

        "TITLE: "Evading non-linearities: Baryon Acoustic Oscillations at the linear point”
         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: “ 

Oct 1, 2015

Sept 24, 2015

Sept. 17, 2015 
  • Vlah et al. 2015,, "Perturbation theory, effective field theory, and oscillations in the power spectrum"
  • Huterer et al. 2015,, "No evidence for bulk velocity from type Ia supernovae"

Sept. 10, 2015

Sept.3, 2015 

Aug 27, 2015 

Aug 20, 2015

Aug 13, 2015

Aug 6, 2015

July 30, 2015
July 23, 2015 
July 16, 2015

July 10, 2015
Jun 25, 2015

June 11, 2015

June 4, 2015
May 28, 2015 

May 13, 2015, 

May 7, 2015, 

April 30, 2015, 


April 23, 2015,

April 16, 2015, 

April 9, 2015, 
  • Guest talk by Evan Scheider
    • Introducing CHOLLA: A New Massively-Parallel Hydrodynamics Code
    • In recent years, computer architectures have grown to incorporate a variety of accelerators that substantially increase the power of a CPU by providing access to thousands of parallel computational elements. Among these accelerators are graphics processor units, or GPUs - devices that were originally designed for on-screen pixel rendering but have since been adapted for general use by the scientific community. In this talk, I will give an overview of a new massively-parallel hydrodynamics code, CHOLLA, written to run natively on these devices. I will discuss advantages and limitations of the GPU programming model, and show some initial scientific results obtained with CHOLLA on the El Gato cluster at the UofA
  • Talk by Ashely Ross
    • Early Dark Energy Survey Science Results.  

April 2, 2015, 

March 26, 2015, 

March 19, 2015 

March 12, 2015

March 5, 2015 

Feb 26, 2015

Feb 19, 2015

Feb 12, 2015
Feb 5, 2015 

Jan 29, 2015 

Jan 22, 2015 

Jan 15, 2015 

Dec 18, 2014
  •     Slepian and Eisenstein 2014,, "On the signature of the baryon-dark matter relative velocity in the two and three-point galaxy correlation functions"

Dec 11, 2014
    Guest talk by Alice Pisani. 
        Precision Cosmology with Cosmic Voids: 
            Modern surveys allow us to access to high quality measurements, by sampling the galaxy distribution in detail also in the emptier regions, voids. Cosmic voids present  themselves as a new tool to constrain cosmology. While the treatment of systematics is simpler in these empty regions, with the aim of achieving the level of precision cosmology a careful modeling of such effects is necessary.  In particular, peculiar velocities affect the way we observe cosmic voids, and thus their effect needs to be understood. Using mock catalogues, I analyze the effect of  peculiar velocities on void properties.  In this talk I thus present the results of the analysis of the                 systematic effects affecting voids and discuss it in the framework of current and future surveys. Additionally, I present a preliminary forecast for void abundances with the   future Euclid and Wfirst missions and obtain, using the Fisher matrix formalism, a prediction for the constraints that void abundances will set on cosmological parameters.

Dec 4, 2014
Nov 20, 2014

Nov 13, 2014

Nov 6, 2014

Oct 30, 2014
  • Chevallard et al. 2014,, "Effect of primordial non-Gaussianities on the far UV-luminosity function of high-redshift galaxies: implications for cosmic reionization"
  • Ngolè Mboula et al.,, "Super-resolution method using sparse regularization for point-spread function recovery"
  • Thompson et al.,, "The rise and fall of a challenger: the Bullet Cluster in Lambda Cold Dark Matter simulations"

Oct 23 2014, 
    Talk by Andreu Font-Ribera (Lawrence Berkeley National Laboratory): "Studying the Expansion of the Universe with BOSS quasars"
            After six years of observations, the Baryon Oscillation Spectroscopic Survey (BOSS) ended last summer, and will soon make its data public
            (SDSS Data Release 12). During these years, it has used the SDSS telescope to obtain spectra of 1.5 million galaxies to get very
            accurate measurements of the Baryon Acoustic Oscillations (BAO) scale at redshift z ~0.5. At the same time, BOSS observed over 184 000 high
            redshift quasars (z>2.15) with the goal of detecting the BAO feature in the clustering of the intergalactic medium, using a technique known
            as the Lyman alpha forest (LyaF).
            In this talk I will overview several results from the LyaF working group in BOSS, including the measurement of BAO at z=2.4 both from the
            auto-correlation of the LyaF (Delubac et al. 2014), and from its cross-correlation with quasars (Font-Ribera et al. 2014). From the
            combination of these studies we are able to measure the expansion rate of the Universe 11 billion years ago with a 2% uncertainty.

Oct 16, 2014

Oct 9, 2014 

Oct 2, 2014 

Sept 25, 2014 

Sept 18, 2014

Sept 11, 2014

Sept 4, 2014 

August 28, 2014
August 21, 2014