The CosmoverseLectures@YourDesk is an exciting new online series that aims to build on the CosmoVerse Training Series and to showcase lecture-style talks on the most prominent works related to cosmological tensions. This will provide early stage researchers with an in-depth understanding of the technical details of leading measurements connected with establishing the robustness of the question of cosmic tensions with a real focus on the underlying analysis.
The CosmoVerse Training Series was aimed at the interface of Fundamental Physics and Data Analysis in Cosmology , while here there will be more focus on the effects of Observational Cosmology and systematics and its intersection with these other areas. By evaluating recent works in the measurement of cosmological parameters using Type Ia supernova, Cosmic microwave background, Baryon acoustic oscillations, Large scale structure, Tip of the red-giant branch, and other measurements, the series will cover the core observables in the field.
Speakers
- Slides
- watch video
Supernova Cosmology, the nuts and bolts
Thursday - March 27, 2025 @ 10:00am CET
Tamara Davis (University of Queensland)
Tamara Davis is an enthusiastic professor of astrophysics at the University of Queensland. She led the Australian Dark Energy Survey (OzDES) and is Deputy Director of the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav). She ran cosmology analyses for three supernova cosmology teams, ESSENCE (2007), SDSS (2009), and DES (2024). During the 2010s she also worked with the WiggleZ survey doing baryon acoustic oscillation cosmology, and is continuing that now with DESI. She is an avid communicator of science and occasional guest host of astrophysics documentaries, including the episode “Black Hole Hunters” which won the American Institute of Physics Science Communication Award. Amongst her many accolades she received an Order of Australia for “significant service to astrophysical science, to education, and to young astronomers”.
How do type Ia supernovae constrain cosmology? It sounds simple… they’re standard(isable) candles so you use their apparent magnitude as a proxy for their distance and plot that against redshift to make a Hubble diagram. Compare that to theory and voila!!, cosmological parameters. Even though supernovae are one of the simplest possible cosmological probes, in practice there are many subtleties and potential selection effects/systematics that need to be taken into account. This talk will show from the ground up the considerations needed when making a supernova Hubble diagram, and potential pitfalls in its use. It will then explore the latest results from projects such as the Dark Energy Survey and discuss the significance of hints of time-varying dark energy seen in the data.
- Slides
- watch video
Cosmic Microwave Background
Thursday - March 27, 2025 @ 10:00am CET
Julien Lesgourgues
RWTH Aachen University
- Slides
- watch video
Baryonic Acoustic Oscillations
Thursday - April 10, 2025 @ 2:00pm CET
Hee-Jong Seo
Ohio University
- Slides
- watch video
Large Scale Structure
Thursday - April 10, 2025 @ 2:00pm CET
Stephen Chen
IAS, Princeton, US
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- watch video
Cepheid variables in the distance ladder
Thursday - April 24, 2025 @ 2:00pm CET
Louise Breuval (Space Telescope Science Institute (STScI))
I’m an ESA Research Fellow at the Space Telescope Science Institute (STScI) in Baltimore (USA), and a member of the SH0ES team. My research focuses on the astronomical distance ladder and the direct measurement of the Hubble Constant H0 with Cepheid variables.
Cepheid variables are the most widely used and the best understood primary distance indicators. In this lecture, I will start by describing how they can be used to measure extragalactic distances and what is their role in the direct measurement of the Hubble constant, H0. The lecture will then cover the most recent updates on the Cepheid and SNIa distance ladder by the SH0ES team, focusing on the first step of the measurement: the geometric calibration of the Cepheid Period-Luminosity relation (Leavitt Law) in nearby galaxies. I will explain how we measure Cepheid distances with the Hubble and James Webb Space Telescopes, and will present important improvements from the Gaia mission. Finally, I will describe how systematic uncertainties are treated in the Cepheid distance ladder.
- Slides
- watch video
Tip of the Red Giant Branch Stars as Distance Indicators
Thursday - April 24, 2025 @ 2:00pm CET
Gagandeep Anand (Space Telescope Science Institute (STScI))
Gagandeep Anand is a Senior Staff Scientist at the Space Telescope Science Institute working on the Advanced Camera for Surveys (ACS), which is one of the two operational imagers on the Hubble Space Telescope. His main research area is near-field cosmology with resolved stellar populations, with a particular focus on the extragalactic distance scale.
The tip of the red giant branch (TRGB) marks the brightest ascent of low-mass red giants, and has been used to measure distances to over five hundred nearby galaxies with the Hubble Space Telescope. I will go over the underlying physical basis for the use of the TRGB as a standard candle, the evolution of the technique over time, and the current state of the method. Particular attention will be given to recent developments in the field, especially with the advent of JWST and in the context of the Hubble tension.