Simulating the collapse of rotating primordial gas clouds to study the survival possibility of Pop III protostars

TL;DR

This study uses advanced 3D simulations to explore how rotating primordial gas clouds collapse, revealing conditions under which Pop III protostars can survive or be ejected, impacting our understanding of early star formation.

Contribution

It presents the first detailed 3D SPH simulations of primordial gas cloud collapse with varying rotation, extending the evolution tracking to 50 solar masses to assess protostar survival.

Findings

Slow-rotating clouds produce more massive protostars.

Fast-rotating clouds have a 10-20% chance of ejecting low-mass stars.

Protostars can grow significantly without radiative feedback.

Abstract

It has been argued that the low-mass primordial stars ($m_{\rm Pop III}\,\leq 0.8\,M_\odot$) are likely to enter the main sequence and hence possibly be found in the present-day Galaxy. However, due to limitations in existing numerical capabilities, current three-dimensional (3D) simulations of disk fragmentation are capable of following only a few thousands of years of evolution after the formation of the first protostar. In this work we use a modified version of {\sc Gadget}-2 smoothed particle hydrodynamics(SPH) code to present the results of non-linear collapse of the gas clouds associated with various degrees of initial solid body rotation (parameterized by $\beta$) using a piecewise polytropic equation of state. The 3D simulations are followed till the epoch when 50$M_{\odot}$ of mass has been accreted in protostellar objects, which is adequate enough to investigate the dynamics of the protostars with the surrounding gaseous medium and to determine the mass function, accretion rate and survival possibility of these protostellar objects till present epoch. We found that evolving protostars that stay within slow-rotating parent clouds can become massive enough due to accretion in the absence of radiative feedback, whereas $10-20 \%$ of those formed within a fast-rotating clouds ($\beta \ge 0.1$) have the possibility to get ejected from the gravitational bound cluster as low mass stars.