Session O04: Cosmology II

Resolving the extended stellar halos of nearby galaxies: the future of Near-Field Cosmology

The widely accepted Cold Dark Matter cosmological paradigm faces important challenges at the scales of individual galaxies. The study of resolved stellar populations in the nearest galaxies, or "near-field cosmology", provides key constraints on the physics underlying galaxy formation and evolution. In this talk, I will present ongoing panoramic imaging surveys of galaxies in the Local Volume performed with ground-based wide-field imagers and followed-up with a multiwavelength approach. Such surveys constitute the first accurate characterization of the past and ongoing accretion processes shaping the halos of these nearby galaxies and their satellite populations: they do not only quantitatively inform theoretical models of galaxy formation and evolution, but also represent a necessary testbed in preparation for the next generation of ground-based and space-borne telescopes.   

Quantum Gravitational Corrections to Gravity during Inflation

Primordial inflation produces a vast ensemble of cosmological scale gravitons which can affect both the force of gravity and the propagation of gravitational radiation. These effects can be studied by using the graviton self-energy to quantum correct the linearized Einstein equations. We will first give an analysis of the structure of the graviton self-energy and then present an explicit result for one loop corrections to the propagation of gravitons. Although suppressed by a minuscule loop-counting parameter, these corrections are enhanced by the square of the number of inflationary e-foldings. This makes the one loop corrections to the tensor power spectrum potentially observable, in the far future, after the full development of 21 cm cosmology.   

Full-sky, arcminute-scale, 3D models of Galactic microwave foreground dust emission based on filaments

We present the DustFilaments code, a full sky model for the mm Galactic emission of thermal dust. Our model, composed of millions of filaments that are imperfectly aligned with the magnetic field, is able to reproduce the main features of the dust angular power spectra at 353 GHz as measured by the Planck mission. Our model is made up of a population of filaments with sizes following a Pareto distribution, with an axis ratio between short and long semi-axes $\sim 0.16$ and an angle of magnetic field misalignment with a dispersion RMS($\theta_{LH}$)$=10^{\circ}$. On large scales our model follows a Planck-based template. On small scales, our model produces spectra that behave like power-laws up to $\ell \sim 4000$ or smaller scales by considering even smaller filaments, limited only by computing power. We can produce any number of Monte Carlo realizations of small-scale Galactic dust. Our model will allow tests of how the small-scale non-Gaussianity affect CMB weak lensing, and the consequences for the measurement of primordial gravitational waves or relativistic light relic species. Our model also can generate frequency decorrelation on the Modified Black Body (MBB) spectrum of dust, and is freely adjustable to different levels of decorrelation.   

Exploring New Physics with N-Point Correlation Functions

I present the galaxy 4-Point Correlation Function (4PCF) can test for cosmological parity violation. The detection of cosmological parity violation would reflect previously unknown forces present at the earliest moments of the Universe. I outline recent developments both in rapidly evaluating galaxy N-Point Correlation Functions (NPCFs) using GPUs and in determining the corresponding covariance matrices. These make the search for parity violation and other physics in the 4PCF and beyond possible in current and upcoming surveys such as those undertaken by Dark Energy Spectroscopic Instrument (DESI), the Euclid satellite, and the Vera C. Rubin Observatory (VRO).