Phd Projects at CAS

PhD Project in Observations

Molecules are crucial players in fundamental astrophysical events such as star and planetary system formation. Studying the chemical inventory of star-forming regions provides unique information on the evolution of gas and dust during the formation of stars and planets. Additionally, molecular emission and absorption can be used to measure fundamental physical properties such as temperature, density, and kinematics. Since molecules are not homogeneously distributed across star-forming regions, multi-molecular and multi-line observations allow the reconstruction of their 3D chemical and physical structures. This PhD project will analyze and interpret single-dish and interferometric data of pre-stellar and protostellar cores to understand the chemical budget available to form planets.

Supervisor: Dr. S. Spezzano

The Environment and Disk connection

The classical picture of star-formation involves a process dominated by the material in the parental dense core, and it is the underlying assumption for simulating the star- and disk-formation process in an isolated box, which has been widely used to learn about the star-formation process. The way in which the material is delivered down to the disk-forming scales plays a critical role, with important implications for planet formation. It controls the amount of angular momentum that is deposited in the central region, which affects the disk size and its chemical composition. Further, there is mounting observational evidence that the planet formation process starts earlier than previously thought, when material is still being deposited onto the disk from the surrounding environment. It is, therefore, crucial to understand the disk build-up phase, since this determines the initial conditions for planet formation.

Recent observations at different evolutionary stages, from the embedded Class 0 up to the late Class II, have revealed the presence of accretion streamers reaching disk scales. The different observational techniques highlight the complementary nature of the various observatories, building a more complete understanding of the accretion process onto the disk. These accretion flows could provide a mechanism to trigger accretion outbursts or modify the chemical abundances of the central region. At the same time, new numerical simulations of the disk and star-formation process have explored the role of non-spherical accretion onto the disk formation scales. However, the role of this previously unaccounted mass delivery mechanism on the early planet formation process is not well explored.

The PhD project will focus on study the interplay between disks and the environment. The data for the project is mostly based on an ongoing NOEMA large program, which is surveying 32 embedded young stellar objects in the Perseus molecular with many molecular lines (data have been obtained for 3/4 of the sample, and to be finished at the end of the year). Complementary ALMA observations are expected, thanks to different already approved ALMA projects. Some analysis techniques are already available, although opportunities for improving them are available and welcomed. In summary, this project will work very close with interferometric observations of molecular lines, and with a particular interest in constraining the disk and streamer interaction and their role in the disk and planet formation.

Supervisor: Dr. Jaime Pineda

Pineda et al. (2020) link
Hsieh et al. (2023) link
Valdivia-Mena et al. (2022) link
Pineda et al. (2022) link

NOEMA large program: link