Galactic Dust Environments - Attenuation Laws and their Effect on the Cosmological Distance Ladder


  • Call:

    PT-CERN Call 2022/2

  • Academic Year:


  • Domain:

    Astroparticle Physics

  • Supervisor:

    Santiago Gonzalez-Gaitan

  • Co-Supervisor:

    Ana Mourão

  • Institution:

    Instituto Superior Técnico (Universidade de Lisboa)

  • Host Institution:

    CENTRA - Center for astrophysics and gravitation

  • Abstract:

    The Hubble tension, that is, the discrepancy between early and late Universe measurements of the Hubble constant, is one of the main topics of contention in modern cosmology. It is not known whether this tension is a product of new physics as of yet unaccounted for in the LCDM and Standard models or of systematic errors in the measurements. One of these potential systematics is dust reddening, which affects the color-luminosity relation of transients such as Cepheids and Supernovae, routinely used as standard candles in the cosmological distance ladder. Current dust corrections can be overly simplistic, assuming a common reddening effect for all transients and not differentiating between intrinsic and extrinsic color effects. This approach is flawed, as it has been shown that dust properties vary greatly across different galaxies and lines of sight. However, the exact root of these changes is still not fully accounted for. The goal of this PhD thesis is to provide a comprehensive study of dust reddening for transients and their host galaxies, examining often overlooked factors such as galaxy morphology/orientation, correlations with other stellar properties and varying dust screens in local galactic sub-structures. We will look at photometry and integral field spectroscopy for a variety of leading edge surveys, as well as perform extensive simulations of dust mediums in different galaxy types. Using statistical and machine learning methods, the relevant dust properties will be mapped and examined, in an effort to fully characterize the physical effects responsible for the variation of dust properties across the Universe. With this data, we will constrain the dust correction of transients, striving toward a distance ladder calibration with as few systematics as possible. This in-depth study of one of the possible sources of the Hubble tension will therefore provide unprecedented insight into the nature of its origins, potentially opening the doors to new physics.