Public Release of A-SLOTH: Ancient Stars and Local Observables by Tracing Halos

Abstract

The semianalytical model a-sloth (Ancient Stars and Local Observables by Tracing Halos) is the first public code that connects the formation of the first stars and galaxies to observables. After several successful projects with this model, we publish the source code (https://gitlab.com/thartwig/asloth) and describe the public version in this paper. The model is based on dark matter merger trees that can either be generated based on Extended Press–Schechter theory or be imported from dark matter simulations. On top of these merger trees, a-sloth applies analytical recipes for baryonic physics to model the formation of both metal-free and metal-poor stars and the transition between them with unprecedented precision and fidelity. a-sloth samples individual stars and includes radiative, chemical, and mechanical feedback. It is calibrated based on six observables, such as the optical depth to Thomson scattering, the stellar mass of the Milky Way and its satellite galaxies, the number of extremely metal-poor stars, and the cosmic star formation rate density at high redshift. a-sloth has versatile applications with moderate computational requirements. It can be used to constrain the properties of the first stars and high-z galaxies based on local observables, predicts properties of the oldest and most metal-poor stars in the Milky Way, can serve as a subgrid model for larger cosmological simulations, and predicts next-generation observables of the early universe, such as supernova rates or gravitational wave events.

Modelling the cosmological Lyman-Werner background radiation field in the Early Universe

“…Present and future observations will be key to complement highresolution simulations of PopIII star formation (Hirano et al 2015;Stacy et al 2016;Park et al 2021) and specific models for PopIII stars (Schaerer 2002;Raiter et al 2010;Gessey-Jones et al 2022;Larkin et al 2023), to put tighter constraints on their IMF. JWST and ALMA will investigate spectral signatures of PopIII-dominated galaxies (Yajima & Khochfar 2017;Woods et al 2021;Nakajima & Maiolino 2022;Latif et al 2022b), while precise metal abundances measurements in Damped Lyman-𝛼 systems (Welsh et al 2019(Welsh et al , 2022 model the chemical enrichment from PopIII supernovae and stellar archaeology is already constraining the IMF low-mass end with local observations of extremely-metal-poor stars (Frebel et al 2007;Rossi et al 2021;Hartwig et al 2015aHartwig et al , 2022. This will help reducing the uncertainties in the LWB modelling presented here.…”

Simulating the Collapse of Rotating Primordial Gas Clouds to Study the Possibility of the Survival of Population III Protostars

“…The age of the universe and the expected time at which the very first stars formed makes direct observations a difficult prospect (see recent surveys by, e.g., Frebel et al 2019;Schauer et al 2020;Suda et al 2021;Finkelstein et al 2022;Hartwig et al 2022). Theoretical prediction of the Lambda cold dark matter model shows that the entire process is led by the gravitational collapse of dark matter halos as a consequence of hierarchical structure formation (see the latest results in, e.g., Bohr et al 2020;Springel et al 2020;Wang et al 2020;May & Springel 2021;Latif et al 2022.…”

Machine Learning Detects Multiplicity of the First Stars in Stellar Archaeology Data

“…The crucial transition from a primordial Universe to a Universe enriched with heavier elements (summarized as "metals" by astronomers) was initiated by the first stars, also termed Population III stars. These stars formed in pristine minihalos around redshift 6-30 (Bromm et al 2002;Yoshida et al 2003;Magg et al 2016;Jaacks et al 2019;Liu & Bromm 2020a;Skinner & Wise 2020;Kulkarni et al 2021;Schauer et al 2021;Hartwig et al 2022). They ended the cosmic dark ages, they provided the first metals, they contributed to the reionization of the Universe, they might have provided the seeds for the first supermassive black holes (Woods et al 2019), and they have set the scene for all subsequent galaxy formation (Taylor & Kobayashi 2014;Dayal & Ferrara 2018;Chen et al 2020;Washinoue & Suzuki 2021).…”

“…Some of these second-generation stars have survived until the present day and we can observe them as old, metal-poor stars in the Milky Way. If we can determine the chemical composition of such extremely metal-poor (EMP, [Fe/H] 8 −3) stars with highresolution spectroscopy, we can infer the nature of the first SNe and therefore constrain the properties of the first stars (e.g., Umeda & Nomoto 2003;Tominaga et al 2014;Placco et al 2016;Fraser et al 2017;Ishigaki et al 2018;Choplin et al 2019;Hansen et al 2020;Placco et al 2021;Skúladóttir et al 2021;Hartwig et al 2022).…”