25 may 2023 - 14:01 CET

The Centre de Physique des Particules de Marseille (CPPM) team in Marseille, France, invites applications for a 3-year PhD fellowship in the area of Gravitational Wave (GW) Cosmology. The PhD programme will be jointly tutored by the Aix-Marseille Université (IPhU [Institute for the Physics of the Universe] / CPPM [Centre de Physique des Particules de Marseille]) and Sapienza University of Rome.

The successful candidate will spend the first half of the PhD program at the University of Rome Sapienza, working in collaboration with Dr. S. Mastrogiovanni and other scientists of the Virgo group, and will be joining the Virgo collaboration.

The fellow will spend the second half of the PhD programme at CPPM in Marseille working in collaboration with Dr. S Escoffier, Dr. E. Kajfasz and other experts in large galaxy surveys, and will be joining the Euclid consortium.

The fellow will also have the opportunity to travel for collaboration with other French Virgo groups such as the L2IT group in Toulouse led by Dr. N. Tamanini. At the end of the successful PhD programme, a diploma will be released by both Aix-Marseille Université and Sapienza University of Rome.

Application is now open until June 19th, 2023. Interviews will be scheduled during the first 10 days of July. The expected thesis starting date is November 1st, 2023. Applicants must hold a Master of science or equivalent in fundamental physics or astrophysics (or equivalent subjects) by the end of October 2023. A good level of English is necessary. Programming skills (python, C++), strong motivation and interest in cosmology as well as the ability to work in large international collaborations will be valuable assets.

Please send your application to Dr. E. Kajfasz (eric.kajfasz@univ-amu.fr), including:

- A motivation letter (maximum two pages).
- A curriculum vitae
- A brief description of research interest and past achievements
- Two reference letters (Head of the Masters program, supervisor of the Master internship) to be sent directly to eric.kajfasz@univ-amu.fr
- A transcript of all university records (Bachelor and Master)
- A copy of the masters diploma

Thesis title: Preparation and exploitation of Euclid data for Gravitational Wave cosmology

The Standard Cosmological Model has passed many precise observational tests in both the early and late-time universe. Nonetheless, the Cosmological Model still suffers from some important observational and theoretical difficulties. On the observational side, there are discrepancies between different independent measurements of the expansion rate of the Universe, the Hubble constant (H0).

Gravitational waves (GWs) open a new opportunity to shed light on the H0-tension. Differently from SNIa, GWs sources are unique tracers of the luminosity distance and can therefore be used to measure the expansion history of the Universe through the distance-redshift relation (Schutz, Nature 1986). These GW detections used as “standard sirens” provide independent measurements of H0. However, one of the key ingredients is precisely to obtain an independent measurement of the redshift of the galaxy that hosted the merger. In case the GW event is detected together with its electromagnetic (EM) counterpart ("bright standard sirens"), the redshift information is inferred from the unique identified host galaxy. In the absence of EM counterpart, which concerns the ~100 GW observations without an identified host galaxy, GW events are called "dark standard sirens". Dark sirens require knowledge of the position and redshift of the ensemble of potential host galaxies within a volume of confidence. Among the different ways to extract the redshift information from GW sources, a promising method is to use galaxy surveys.

The proposed PhD project aims to establish how the new generation of galaxy surveys, such as the Dark Energy Spectroscopic Instrument (DESI) and the Euclid mission, used in the context of gravitational waves can provide competitive constraints on the measurement of the Hubble constant H0, and can overcome the inconsistency between historical measurements from the CMB and from supernovae. To this end, several objectives have been identified: a) to build novel techniques for GW cosmology, by developing new statistical approaches applied to galaxy samples; b) to infer cosmological constraints using current data, with the goal to bring competitive constraints on the Hubble constant H0 compared to other methods; and c) to prepare tomorrows analyses with the arrival of the next generation observatories.