TRACKING THE DISTRIBUTION OF ²⁶Al AND ⁶⁰Fe DURING THE EARLY PHASES OF STAR AND DISK EVOLUTION

Abstract

Fe ratios of accreting gas within a vicinity of 1000 au of the stars follow the predicted decay curves of the initial abundances at the time of star formation without evidence of spatial or temporal heterogeneities for the first 100 kyr of star formation. Therefore, the observed differences in 26 Al/ 27 Al ratios between FUN and canonical CAIs are likely not caused by admixing of supernova material during the early evolution of the proto-Sun. Selective thermal processing of dust grains is a more viable scenario to account for the heterogeneity in 26 Al/ 27 Al ratios at the time of solar system formation.

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

“…MacPherson & Boss (2011) suggested instead that the FUN inclusions may have originated in a SLRI-poor young stellar object (YSO), ejected by the YSO's bipolar outflow, and transported to a presolar cloud core in the same star-forming region. Kuffmeier et al (2016) have argued against both of these suggestions, in the latter case on the basis that the inclusions would have to come from more than ∼ 0.25 pc away, which they judged to be unrealistic. With regard to the former suggestion, Kuffmeier et al (2016) included as a second step zoom-in calculations of the GMC regions where eleven low mass stars formed, represented in the GMC code as sink particles, with a focus on the SLRI levels in the immediate vicinity (50 AU or 1000 AU) of the sink particles.…”

“…The Vasileiadis et al (2013) and Kuffmeier et al (2016Kuffmeier et al ( , 2017 GMC calculations have a similar limitation to optically thin regimes. In our case, this restriction allows one to learn if a given target cloud can be shocked into collapse, but it prohibits following the calculation to much later times, after the central protostar forms, surrounded by infalling, rotating gas and dust that will form the solar nebula.…”

“…Such interactions are the focus of the present series of studies, where SN shocks with ∼ 60 AU thicknesses strike clouds and within 0.1 Myr trigger collapse to densities of over ∼ 10 −11 g cm −3 . In fact, star formation in the Vasileiadis et al (2013) and Kuffmeier et al (2016) GMC calculation is not the result of SN shock wave triggering, but rather the eventual self-gravitational collapse of pre-stellar cores formed by GMC turbulence over 4 Myr of GMC evolution. Balazs et al (2004) presented observational evidence that a supernova shock front triggered the formation of T Tauri stars in the L1251 cloud.…”

“…However, analysis of Al and Fe dust grains in SN ejecta constrain their sizes to be less than 0.01 µm (Bocchio et al 2016), effectively severely limiting the value of both of these injection mechanism scenarios. Vasileiadis et al (2013) and Kuffmeier et al (2016) have modeled the evolution of a ∼ 10 5 M ⊙ Giant Molecular Cloud (GMC), and shown how the SLRIs ejected by CCSN in the GMC can pollute the surrounding gas to highly variable levels, ranging from 26 Al/ 27 Al ∼ 10 −7 to ∼ 10 −1 , much higher than the canonical solar system ratio of 26 Al/ 27 Al ∼ 5 × 10 −5 (Lee et al 1976). Ratios of 60 Fe/ 56 Fe were as high ∼ 10 −3 (Kuffmeier et al 2016), again much higher than any meteoritical estimates.…”

“…Vasileiadis et al (2013) and Kuffmeier et al (2016) have modeled the evolution of a ∼ 10 5 M ⊙ Giant Molecular Cloud (GMC), and shown how the SLRIs ejected by CCSN in the GMC can pollute the surrounding gas to highly variable levels, ranging from 26 Al/ 27 Al ∼ 10 −7 to ∼ 10 −1 , much higher than the canonical solar system ratio of 26 Al/ 27 Al ∼ 5 × 10 −5 (Lee et al 1976). Ratios of 60 Fe/ 56 Fe were as high ∼ 10 −3 (Kuffmeier et al 2016), again much higher than any meteoritical estimates. Given that the GMC simulation covered a 3D region 40 pc in extent, with computational cell densities no higher than ∼ 10 −16 g cm −3 , data sampled every 0.05 Myr, and minimum grid spacings of 126 AU, this ambitious simulation was unable to follow in detail the interactions of specific supernova shock fronts with any dense molecular cloud cores.…”