arXiv subjects

Thales Gutcke

Publications and source records attributed to Thales Gutcke.

3 recordsLinked to original sources

arXiv2025

Co-evolution of baryons and dark matter halos of LYRA dwarf galaxies

We use the extremely high-resolution ($m_{\rm bary}=4\rm{M}_\odot$) LYRA cosmological galaxy formation simulations of six dwarf galaxies with $M_{\rm 200c}\sim10^9\rm{M}_\odot$ at $z=0$ to investigate their stellar assembly histories. Based on the age of stars in these galaxies at $z=0$, $40-100\%$ of their stellar mass was formed by the time of reionization, when star formation (SF) abruptly shuts down. Depending on their halo mass evolution, some of the dwarfs reignite SF post-reionization (rejuvenators), while others remain quenched for the rest of cosmic time (reionization relics). However, the stellar mass of relics can still grow by more than $50\%$ through mergers post-reionisation. We find clear correlations between metallicity distributions of the galaxies and the fraction of stars formed post-reionization ($f_{\rm post-reio}^\star$) such that relics have lower median $\rm [Fe/H]$ with a more prominent low metallicity tail. Moreover, the shape of the galaxies at $z=0$ correlates with their $f_{\rm post-reio}^\star$, with rejuvenators showing more spherical stellar distribution than relics. This difference arises only post-reionization when rejuvenators become rounder with more SF activity. Similarly, the shape of dark matter (DM) halos in the inner regions display more spherical distributions in rejuvenators than in relics. The shape evolution shows that DM haloes in all galaxy formation simulations become rounder in comparison to their collision-less, DM-only counterparts. However, DM haloes of rejuvenators evolve more significantly. We do not find any correlation between SF activity and formation of shallow DM density cores in these galaxies. These predictions can be tested using upcoming observational data. In particular, our results indicate that the scatter in the mass-metallicity relation in the low mass regime is correlated with SF histories and the shape of galaxies.

astro-ph.GA↗

arXiv2018

On the Optimal Choice of Nucleosynthetic Yields, IMF and Number of SNe Ia for Chemical Evolution Modelling

To fully harvest the rich library of stellar elemental abundance data available, we require reliable models that facilitate our interpretation of them. Galactic chemical evolution (GCE) models are one such set, and a key part of which are the selection of chemical yields from different nucleosynthetic enrichment channels, predominantly asymptotic giant branch (AGB) stars, Type Ia supernovae (SNe Ia), and core-collapse supernovae (CC-SNe). Here, we present a scoring system for yield tables based on their ability to reproduce proto-solar abundances within a simple parametrisation of the GCE modelling software Chempy, which marginalises over galactic parameters describing simple stellar populations (SSPs) and interstellar medium physics. Two statistical scoring methods are presented, based on Bayesian evidence and leave-one-out cross-validation and are applied to five CC-SN tables, (a) for all mutually available elements and (b) for a subset of the 9 most abundant elements. We find that the yields of Prantzos et al. (P18, including stellar rotation) and Chieffi & Limongi (C04) best reproduce proto-solar abundances for the two cases, respectively. The inferred best-fit SSP parameters for (b) are $α_\mathrm{IMF}=-2.45^{+0.15}_{-0.11}$ for the initial mass function high-mass slope and $\mathrm{N}_\mathrm{Ia}=1.29^{+0.45}_{-0.31}\times10^{-3}$ M$_\odot^{-1}$ for the SN Ia normalisation, which are broadly consistent across tested yield tables. Additionally, we demonstrate how Chempy can be used to dramatically improve elemental abundance predictions of hydrodynamical simulations by plugging tailored best-fit SSP parameters into a Milky Way analogue from Gutcke & Springel. Our code, including a comprehensive tutorial, is freely available and can additionally provide SSP enrichment tables for any combination of parameters and yield tables.

astro-ph.GA↗

arXiv2017

NIHAO VII: Predictions for the galactic baryon budget in dwarf to Milky Way mass haloes

We use the NIHAO galaxy formation simulations to make predictions for the baryonic budget in present day galaxies ranging from dwarf to Milky Way masses. The sample is made of 88 independent high resolution cosmological zoom-in simulations. NIHAO galaxies reproduce key properties of observed galaxies, such as the stellar mass vs halo mass and cold gas vs stellar mass relations. Thus they make plausible predictions for the baryon budget. We present the mass fractions of stars, cold gas ($T<10^4$K), cool gas ($10^4 < T < 10^5$K), warm-hot gas ($10^5 < T < 5\times10^6$K), and hot gas (T$> 5\times10^6$K) inside the virial radius, $R_{200}$. Compared to the predicted baryon mass, using the dark halo mass and the universal baryon fraction, $f_{\rm b}\equiv Ω_{\rm b}/Ω_{\rm m}=0.15$, we find that all of our haloes are missing baryons. The missing mass has been relocated past 2 virial radii, and cool gas dominates the corona at low mass (M$_{200} < 3 \times 10^{11} M_\odot$) while the warm-hot gas dominates at high mass (M$_{200} > 3 \times 10^{11} M_\odot$). Haloes of mass $\sim 10^{10} M_\odot$ are missing $\sim 90\%$ of their baryons. More massive haloes ($\sim 10^{12} M_\odot$) retain a higher fraction of their baryons, with $\sim 30\%$ missing, consistent with recent observational estimates. Moreover, these more massive haloes reproduce the observed fraction of cold, warm-hot and hot gas. The fraction of cool gas we predict ($0.11\pm0.06$) is significantly lower than the observation from COS-HALOs (0.3-0.47), but agrees with the alternative analysis of Stern et al. 2016.

astro-ph.GA↗