Triggering Collapse of the Presolar Dense Cloud Core and Injecting Short-lived Radioisotopes with a Shock Wave. V. Nonisothermal Collapse Regime

Abstract

Recent meteoritical analyses support an initial abundance of the short-lived radioisotope 60 Fe that may be high enough to require nucleosynthesis in a core collapse supernova, followed by rapid incorporation into primitive meteoritical components, rather than a scenario where such isotopes were inherited from a well-mixed region of a giant molecular cloud polluted by a variety of supernovae remnants and massive star winds. This paper continues to explore the former scenario, by calculating three dimensional, adaptive mesh refinement, hydrodynamical code (FLASH 2.5) models of the self-gravitational, dynamical collapse of a molecular cloud core that has been struck by a thin shock front with a speed of 40 km/sec, leading to the injection of shock front matter into the collapsing cloud through the formation of Rayleigh-Taylor fingers at the shock-cloud intersection. These models extend the previous work into the nonisothermal collapse regime using a polytropic approximation to represent compressional heating in the optically thick protostar. The models show that the injection efficiencies of shock front material are enhanced compared to previous models, which were not carried into the nonisothermal regime and so did not reach such high densities. The new models, combined with the recent estimates of initial 60 Fe abundances, imply that the supernova triggering and injection scenario remains as a plausible explanation for the origin of the short-lived radioisotopes involved in the formation of our solar system.

Triggering Collapse of the Presolar Dense Cloud Core and Injecting Short-lived Radioisotopes with a Shock Wave. VI. Protostar and Protoplanetary Disk Formation

“…This cooling, however, is only appropriate in optically thin regions, and hence is invalid in high density regions. Boss (2017) extended the models to later, higher density phases of evolution by employing a barotropic equation of state once densities high enough to produce an optically thick protostar arose, i.e., for densities above some critical density ρ cr (Boss 1980). The same approach is employed here, in addition to the sink particle artifice, to handle high density regions.…”

“…In higher density regions, the gas pressure p is defined to depend on the gas density as p ∝ ρ γ , where the barotropic exponent γ equals 7/5 for molecular hydrogen gas. Boss (2017) tested several different choices for ρ cr in order to find a value that reproduced approximately the thermal evolution found in the spherically symmetrical collapse models of Vaytet et al (2013), who studied the collapse of solar-mass gas spheres with a multigroup radiative hydrodynamics code. Boss (2017) found that ρ cr ∼ 5 × 10 −13 g cm −3 was the best choice for reproducing the Vaytet et al (2013) thermal evolutions.…”

“…In all of the new models, the initial shock wave was defined to have a speed of 40 km s −1 , a width of 3 × 10 −4 pc, and a density of 7.2 × 10 −18 g cm −3 , as assumed by Boss (2017). This particular choice is based on previous modeling, which examined a wide range of shock parameters.…”

Heterogeneous evolution of the galaxy and the origin of the short-lived nuclides in the early solar system

“…A wide range of astrophysical scenarios have been proposed for the origin of the solar system (see e.g., Boss 1995;Cameron et al 1995;Wasserburg et al 2006;Sahijpal & Soni 2006;Gaidos et al 2009;Gounelle et al 2009;Huss et al 2009;Sahijpal and Gupta 2009;Dauphas and Chaussidon 2011;Boss 2017;Liu 2017;Lugaro, Ott & Kereszturi 2018;Jones et al 2019). Evolved stars ranging from massive Wolf-Rayet (WR) stars, Supernovae (SN Ia, Ib/c, SN II) and Asymptotic Giant Branch (AGB) stars have been proposed along with distinct stellar environments associated with the birth of the solar system.…”

“…Various stellar nucleosynthetic processes can contribute towards the predicted abundance of the SLRs (Cameron et al 1995;Wasserburg et al 2006;Sahijpal & Soni 2006;Gaidos et al 2009;Gounelle et al 2009;Huss et al 2009;Sahijpal and Gupta 2009;Dauphas and Chaussidon 2011;Boss 2017;Dwarkadas et al 2017;Liu 2017;Lugaro et al 2018;Jones et al 2019).…”