Accretion and Outflow Processes in Massive Star Formation

• Grant number: 25/16334-2
• Support Opportunities: Scholarships in Brazil - Master
• Start date: September 01, 2025
• End date: August 31, 2027
• Field of knowledge: Physical Sciences and Mathematics - Astronomy - Stellar Astrophysics
• Principal Investigator: Ciriaco Goddi
• Grantee: Luiza Olivieri Ponte
• Host Institution: Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 21/01183-8 - Astrophysical jets at the highest-angular resolution with very long baseline interferometry, AP.JP

Abstract

Outflows from high-mass young stellar objects (HMYSOs) play a critical role in the formation of massive stars, yet their driving mechanisms remain poorly understood. Various models-ranging from magneto-centrifugal winds to radiation and ionization-driven flows-predict different outflow morphologies (e.g., narrow vs. wide bases, single vs. multiple components), collimation degrees, and momentum and energy distributions over spatial scales.To constrain these models and advance our understanding of high-mass star formation (HMSF), we have initiated a comprehensive observational program with ALMA. The primary goals are to characterize the morphology and kinematics of massive outflows and to quantify how their physical properties (velocity, mass, momentum, kinetic energy) vary with both distance from the protostar and stellar mass/luminosity.Within this context, the Master's project will focus on the W51 star-forming complex, one of the most luminous and active stellar nurseries in the Galaxy, located at a distance of 5.4 kpc. The student will apply and expand upon methodologies developed in previous case studies of individual sources, using ALMA observations spanning multiple frequency bands (3 mm and 1.3 mm) and a wide range of spatial resolutions (from 0."2 to 0."02).Low-resolution ALMA imaging (0."2; Ginsburg et al. (2017)) has revealed dozens of collimated outflows from HMYSOs in W51, making it an ideal laboratory for statistical studies of outflows in HMSF. Follow-up high-resolution observations (0."02; Goddi et al. (2020)) further demonstrated that these sources are in an active accretion phase. ALMA's capabilities allow us to trace the velocity field and physical structure of outflows over a range of spatial scales (R ~ 10³ - 10¿ AU), as a function of the properties of the central sources.The ultimate aim of the project is to address key open questions in massive star formation:1. How do the physical properties of outflows vary with protostellar mass and evolutionary stage?2. Can accretion continue after the onset of an H II region, or do all H II regions expand and disrupt infall?3. What is the dominant driving mechanism of outflows from HMYSOs?