Periodic Reporting for period 1 - HALOS2020 (Accurate halo masses in the precision cosmology era)
Berichtszeitraum: 2018-09-01 bis 2020-08-31
The overall goal is to develop techniques for obtaining accurate measurements of the distribution of dark matter in galaxies and apply these to observational data.
Dark matter constitutes 90% of the mass of the Universe, but so far has never been detected by a laboratory experiment. Consequently, our understanding of the properties of dark matter, such as its ability to interact with ordinary matter, is very limited. One of the ways to gain knowledge on dark matter is by measuring its distribution in galaxies. This project is aimed at obtaining improved measurements of the distribution of dark matter in massive galaxies and comparing these measurements with predictions from numerical simulations. The main tool used for these measurements are strong gravitational lensing and weak gravitational lensing.
Dark matter constitutes 90% of the mass of the Universe, but so far has never been detected by a laboratory experiment. Consequently, our understanding of the properties of dark matter, such as its ability to interact with ordinary matter, is very limited. One of the ways to gain knowledge on dark matter is by measuring its distribution in galaxies. This project is aimed at obtaining improved measurements of the distribution of dark matter in massive galaxies and comparing these measurements with predictions from numerical simulations. The main tool used for these measurements are strong gravitational lensing and weak gravitational lensing.
Work was carried out on two fronts in parallel: weak gravitational lensing and strong gravitational lensing.
On the weak lensing side, I completed a measurement of the distribution of dark matter halo mass as a function of the stellar mass and the surface brightness profile of massive galaxies. The measurement revealed that, at fixed stellar mass, dark matter halo mass is at most weakly correlated with the size of a galaxy. The work was published on Astronomy & Astrophysics (Sonnenfeld et al. 2019a). This result is being used to validate models of galaxy evolution: in particular, I started a comparison between these weak lensing measurements and predictions from the EAGLE hydrodynamical simulation. This comparison work is currently being carried out by a Leiden University MSc student, Ms. Juliette Hilhorst.
In order to facilitate the comparison between the properties simulated and observed galaxies, I introduced a new description of the stellar surface mass density profile of galaxies, which is more robust than the traditional description based on the total mass and half-mass radius. This work was published on Astronomy & Astrophysics (Sonnenfeld 2020).
I then started three weak lensing-related projects: one aimed at measuring the distribution of halo virial radius as a function of galaxy half-mass radius, one on predicting to what extent weak lensing data can be used to measure the stellar masses of galaxies and a third one aimed at measuring the distribution of halo mass as a function of the age of the stellar population of galaxies. The first two projects are currently being carried out by Leiden University MSc students, Ms. Lindsey Obserhelman and Ms. Maryam Tajalli, while I am directly working on the third.
On the strong lensing side, I carried out a statistical measurement of the distribution of dark matter and stars in a small sample of lenses from the HSC survey. The main innovation in this work was the development of a method to model and correct for selection effects in strong lensing surveys. The work was published on Astronomy & Astrophysics (Sonnenfeld et al. 2019b). Finally, I led a search for strong lenses in the HSC survey based on crowdsourcing. The campaign led to the discovery of about 200 new likely strong lenses (Sonnenfeld et al. 2020b).
I presented the results described above at the following international conferences:
Australia-ESO conference 2019 (Sydney, Australia, February 18-22, 2019)
Matera Oscura: cosmology and dark matter within galaxies and clusters (Matera, Italy, September 2-6, 2019)
Australia-ESO conference 2020 (Perth, Australia, February 17-21, 2020)
European Astronomical Society annual meeting 2020 (virtual conference, June 29, 2020)
No website has been developed for the project.
On the weak lensing side, I completed a measurement of the distribution of dark matter halo mass as a function of the stellar mass and the surface brightness profile of massive galaxies. The measurement revealed that, at fixed stellar mass, dark matter halo mass is at most weakly correlated with the size of a galaxy. The work was published on Astronomy & Astrophysics (Sonnenfeld et al. 2019a). This result is being used to validate models of galaxy evolution: in particular, I started a comparison between these weak lensing measurements and predictions from the EAGLE hydrodynamical simulation. This comparison work is currently being carried out by a Leiden University MSc student, Ms. Juliette Hilhorst.
In order to facilitate the comparison between the properties simulated and observed galaxies, I introduced a new description of the stellar surface mass density profile of galaxies, which is more robust than the traditional description based on the total mass and half-mass radius. This work was published on Astronomy & Astrophysics (Sonnenfeld 2020).
I then started three weak lensing-related projects: one aimed at measuring the distribution of halo virial radius as a function of galaxy half-mass radius, one on predicting to what extent weak lensing data can be used to measure the stellar masses of galaxies and a third one aimed at measuring the distribution of halo mass as a function of the age of the stellar population of galaxies. The first two projects are currently being carried out by Leiden University MSc students, Ms. Lindsey Obserhelman and Ms. Maryam Tajalli, while I am directly working on the third.
On the strong lensing side, I carried out a statistical measurement of the distribution of dark matter and stars in a small sample of lenses from the HSC survey. The main innovation in this work was the development of a method to model and correct for selection effects in strong lensing surveys. The work was published on Astronomy & Astrophysics (Sonnenfeld et al. 2019b). Finally, I led a search for strong lenses in the HSC survey based on crowdsourcing. The campaign led to the discovery of about 200 new likely strong lenses (Sonnenfeld et al. 2020b).
I presented the results described above at the following international conferences:
Australia-ESO conference 2019 (Sydney, Australia, February 18-22, 2019)
Matera Oscura: cosmology and dark matter within galaxies and clusters (Matera, Italy, September 2-6, 2019)
Australia-ESO conference 2020 (Perth, Australia, February 17-21, 2020)
European Astronomical Society annual meeting 2020 (virtual conference, June 29, 2020)
No website has been developed for the project.
The work carried out so far contributed in two distinct ways to the progress of the field of extragalactic astronomy.
On the one hand, weak and strong lensing measurements produced new measurements of the distribution of dark matter halo mass and of the normalization of the stellar mass-to-light ratio of galaxies, and are currently being used to constrain models of galaxy evolution.
On the other hand, it promoted the adoption of a forward-modeling approach to galaxy-galaxy lensing studies, in which several potential sources of systematic errors are explicitly modeled and accounted for. The impact of these innovations will become more apparent in the coming years, as the precision of weak and strong lensing measurements will increase and more traditional analysis tools will quickly become systematics-limited.
On the one hand, weak and strong lensing measurements produced new measurements of the distribution of dark matter halo mass and of the normalization of the stellar mass-to-light ratio of galaxies, and are currently being used to constrain models of galaxy evolution.
On the other hand, it promoted the adoption of a forward-modeling approach to galaxy-galaxy lensing studies, in which several potential sources of systematic errors are explicitly modeled and accounted for. The impact of these innovations will become more apparent in the coming years, as the precision of weak and strong lensing measurements will increase and more traditional analysis tools will quickly become systematics-limited.