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Ripoche, Paul

University of British Columbia

Studying galaxies helps scientists understand better the structure and history of the Universe. The properties of galaxies, such as their dynamics and evolution, can be inferred through studying the age, composition, and distribution of the different stellar populations (from young stars to their remnants) that constitute them, using multi-wavelength observations. In this thesis, we focus on the study of old stellar populations and their remnants, from X-rays to the near infrared. Superconducting transition-edge sensors carried by X-ray telescopes, such as Colibrì, are powerful tools for the study of neutron stars’ and black holes’ fundamental properties. We develop a low-computational-cost technique that optimizes energy and time resolution to levels of about 1 eV and 100 ns, respectively, over a wide range of energies (0–30 keV). Such sensitivities will give new insights on the physics of dense matter and extreme magnetic fields. Using 2MASS near-infrared photometry and the Gaia Data Release 2, we identify carbon stars in the Large Magellanic Cloud, Small Magellanic Cloud and Milky Way (MW), and we derive the corresponding carbon-star luminosity function (CSLF). Due to its limited dispersion in the J band, the CSLF is a promising rung in the cosmic distance ladder (up to 50–60 Mpc). Thanks to the next generation of telescopes (e.g. James Webb Space Telescope), the CSLF could replace the Cepheid–Type-Ia supernova pair rung, thus enabling the derivation of an independent measurement of the Hubble constant. We identify galactic white dwarfs (WDs) thanks to their colours, in the Canada-France-Hawai‘i Telescope Large Area U-band Deep Survey, at unprecedented faint magnitudes (27 mag). The U-band and optical photometry allows us to fit for the physical properties of the white dwarfs, such as surface temperature, mass, surface gravity, cooling age, and distance. We find a main mass peak consistent with globular-cluster studies, making our sample the largest and deepest old stellar-halo WD population. Finally, we derive a typical age of the MW stellar halo consistent with previous studies, as well as the typical age of the oldest WDs in the MW, putting further constraints on the history of our Galaxy.

Text

2023-08-30

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/85690

Physics

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/