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

Abstract

We present galactic chemical evolution (GCE) models of the short-lived radionuclides (SLRs), 26 Al, 36 Cl, 41 Ca, 53 Mn and 60 Fe, across the entire Milky Way galaxy. The objective is to understand the spatial and temporal distribution of the SLRs in the galaxy. The gamma-ray observations infer widespread distribution of 26 Al and 60 Fe across the galaxy. The signatures of the SLRs in the early solar system (ESS) are found in meteorites. We present homogeneous GCE simulation models for SLRs across the galaxy. We also develop a set of heterogeneous GCE models to understand the evolution of the galaxy within independent spatial grids of area, 0.1-1 kpc 2 . These grids evolve distinctly in terms of nucleosynthetic contributions of massive stars. We succeeded in simulating the formation and evolution of generations of stellar clusters/association. Based on the formulation, we provide a novel method to amalgamate the origin of the solar system with the gradual evolution of the galaxy along with a self-consistent origin of SLRs. We explore the possibility of the birth of the solar system in an environment where one of the stellar clusters formed ≥25 Million years earlier. The decaying 53 Mn and 60 Fe remnants from the evolved massive stars from the cluster probably contaminated the local medium associated with the presolar molecular cloud. A Wolf-Rayet wind from a distant massive star, belonging to a distinct cluster, probably contributed, 26 Al (and 41 Ca) to the presolar cloud. The irradiation production of 7,10 Be and 36 Cl occurred later in ESS.

Short-lived Radionuclides in the Milky Way Galaxy

“…The sum of the mass of 26 Al and 60 Fe over the 2-18 kpc of the Galaxy is 0.2 M ⊙ and 0.08 M ⊙ , respectively. The abundance of other SLRs, 36 Cl, 41 Ca and 53 Mn, also follow a similar trend of decrease in the abundance per unit area of the ring as we move towards the Galaxy's outer regions as shown in figure 1 of [3]. The areas of the rings from 2-18 kpc, which have 2 kpc width, from the inner first to outer eighth ring, are given as 37.68, 62.8, 87.92, 113.04, 138.16, 163.28, 188.4, and 213.52 kpc 2 respectively.…”

“…The model also predicts the metallicity and [Fe/H] for the Galaxy over the galactic time scale. Each ring experiences the accretion of gas and forms various generations of stars as explained in section 2 above and in [3]. The SLRs trends mainly depend upon the star formation rate in the region,which is higher in the inner regions and decreases as we move towards the outer regions of the Galaxy.…”

“…Also, the observations from the other galaxies will provide more stringent constraints for the stellar and galactic chemical evolution modelling community. We have studied the abundance of SLRs using the Galactic Chemical Evolution (GCE) models discussed in [3]. Short-lived radionuclide (SLR) 26…”

Theoretical Distributions of Short-Lived Radionuclides for Star Formation in Molecular Clouds

“…We thus determine how the distributions of SLR abundances vary with the time and spatial dependence of star formation, the fractal dimension of the molecular cloud, cluster properties, propagation efficiencies, and other inputs. Although this paper focuses on nuclear enrichment on scales of molecular clouds, we note that additional studies have also considered enrichment on galactic scales (e.g., Fujimoto et al 2018;Cote et al 2019;Kaur & Sahijpal 2019). For example, this latter study estimates the time evolution of the galactic-scale abundances of SLRs and also constructs a working scenario to explain the observed isotopic abundances in our Solar System.…”

“…Most stars form within embedded clusters (Lada & Lada 2003;Porras et al 2003), and the immediate cluster properties largely determine the degree of dynamical disruption (Adams et al 2006;Malmberg et al 2007;Portegies Zwart 2009;Pfalzner et al 2013) and the intensity of the background radiation (Fatuzzo & Adams 2008;Lee & Hopkins 2020;Parker et al 2021). The particle contribution includes both high energy cosmic radiation and short-lived radioactive nuclei, which are produced via supernovae and stellar winds (Vasileiadis et al 2013;Adams et al 2014;Lichtenberg et al 2016;Kuffmeier et al 2016;Nicholson & Parker 2017;Kaur & Sahijpal 2019). The accelerated particles can propagate beyond the immediate cluster environment and thereby influence additional star forming regions within the molecular cloud.…”