The impact of an evolving stellar initial mass function on early galaxies and reionisation

Abstract

Observations with JWST have revealed an unexpected high abundance of bright z>10 galaxy candidates. We explore whether a stellar initial mass function (IMF) that becomes increasingly top-heavy towards higher redshifts and lower gas-phase metallicities results in a higher abundance of bright objects in the early universe and how it affects the evolution of galaxy properties compared to a constant IMF. We incorporate such an evolving IMF into the Astraeus framework that couples galaxy evolution and reionisation in the first billion years. Our implementation accounts for the IMF dependence of supernova feedback, metal enrichment, ionising and ultraviolet radiation emission. We conduct two simulations: one with a Salpeter IMF and one with the evolving IMF. Compared to a constant Salpeter IMF, we find that (i) the higher abundance of massive stars in the evolving IMF results in more light per unit stellar mass, a slower build-up of stellar mass and lower stellar-to-halo mass ratio; (ii) due to the self-similar growth of the underlying dark matter halos, the evolving IMF's star formation main sequence hardly deviates from that of the Salpeter IMF; (iii) the evolving IMF's stellar mass-metallicity relation shifts to higher metallicities while its halo mass-metallicity relation remains unchanged; (iv) the evolving IMF's median dust-to-metal mass ratio is lower due to its stronger SN feedback; (v) the evolving IMF requires lower values of the escape fraction of ionising photons and exhibits a flatter median relation and smaller scatter between the ionising photons emerging from galaxies and the halo mass. Yet, the topology of the ionised regions hardly changes compared to the Salpeter IMF. These results suggest that a top-heavier IMF alone is unlikely to explain the higher abundance of bright z>10 sources, since the lower mass-to-light ratio is counteracted by the stronger stellar feedback.

19 pages, 13 figures, Accepted for publication in Astronomy & Astrophysics

References in corpus (33)

• A Highly Consistent Framework for the Evolution of the Star-Forming "Main Sequence" from z~0-6
• UV Luminosity Functions at redshifts z~4 to z~10: 10000 Galaxies from HST Legacy Fields
• Model-independent evidence in favor of an end to reionization by z~6
• Two Remarkably Luminous Galaxy Candidates at $z\approx 10-12$ Revealed by JWST
• The evolution of the galaxy UV luminosity function at redshifts z ~ 8-15 from deep JWST and ground-based near-infrared imaging
• Early results from GLASS-JWST. III: Galaxy candidates at z$\sim$9-15
• Efficient Formation of Massive Galaxies at Cosmic Dawn by Feedback-Free Starbursts
• The chemical enrichment in the early Universe as probed by JWST via direct metallicity measurements at z~8
• New observations of z~7 galaxies: evidence for a patchy reionization
• An excess of massive stars in the local 30 Doradus starburst
• Inferences on the Timeline of Reionization at z~8 From the KMOS Lens-Amplified Spectroscopic Survey
• A lack of evolution in the very bright-end of the galaxy luminosity function from z = 8-10
• Cosmic Reionization On Computers I. Design and Calibration of Simulations
• First look with JWST spectroscopy: $z\sim 8$ galaxies resemble local analogues
• New Constraints on the Faint-end of the UV Luminosity Function at z~7-8 using the Gravitational Lensing of the Hubble Frontier Fields Cluster A2744
• Essential physics of early galaxy formation
• The luminosity function, halo masses and stellar masses of luminous Lyman-break galaxies at redshifts 5<z<6
• Variations of the stellar initial mass function in the progenitors of massive early-type galaxies and in extreme starburst environments
• A Lower Bound of Star Formation Activity in Ultra-high Redshift Galaxies Detected with JWST: Implications for Stellar Populations and Radiation Sources
• The ALMA REBELS Survey: the dust content of $z\sim 7$ Lyman Break Galaxies
• The Luminosity Function at z~8 from 97 Y-band dropouts: Inferences About Reionization
• Stochastic star formation in early galaxies: JWST implications
• The optimally-sampled galaxy-wide stellar initial mass function - Observational tests and the publicly available GalIMF code
• Has JWST already falsified dark-matter-driven galaxy formation?
• Coevolution of metallicity and star formation in galaxies to z=3.7: I. A fundamental plane
• The Stellar Initial Mass Function in Early-Type Galaxies From Absorption Line Spectroscopy. IV. A Super-Salpeter IMF in the center of NGC 1407 from Non-Parametric Models
• Spectroscopic evolution of very massive stars at Z = 1/2.5 Zsun
• Implications of a Temperature Dependent IMF I: Photometric Template Fitting
• Inferring the presence of very massive stars in local star-forming regions
• Evidence for Very Massive Stars in extremely UV-bright star-forming galaxies at $z\sim 2.2-3.6$
• Extreme broad He\2 emission at high and low redshifts: the dominant role of VMS in NGC 3125-A1 and CDFS131717
• AstraeusIV : Quantifying the star formation histories of galaxies in the Epoch of Reionization
• Implications of a Temperature Dependent IMF II: An Updated View of the Star-Forming Main Sequence

Cited by in corpus (27)

• The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics
• The JWST-PRIMAL Legacy Survey. A JWST/NIRSpec reference sample for the physical properties and Lyman-$\alpha$ absorption and emission of $\sim 500$ galaxies at $z=5.5-13.4$
• A remarkable Ruby: Absorption in dense gas, rather than evolved stars, drives the extreme Balmer break of a Little Red Dot at $z=3.5$
• COSMOS-Web: stellar mass assembly in relation to dark matter halos across $0.2<z<12$ of cosmic history
• EPOCHS IV: SED Modelling Assumptions and their impact on the Stellar Mass Function at 6.5 < z < 13.5 using PEARLS and public JWST observations
• The Extreme Low-mass End of the Mass-Metallicity Relation at $z\sim 7$
• Observable and ionizing properties of star-forming galaxies with very massive stars and different IMFs
• Synergising semi-analytical models and hydrodynamical simulations to interpret JWST data from the first billion years
• The effect of the environment-dependent stellar initial mass function on the photometric properties of star-forming galaxies
• Exploiting synergies between JWST and cosmic 21-cm observations to uncover star formation in the early Universe
• The mass-metallicity relation as a ruler for galaxy evolution: insights from the James Webb Space Telescope
• Constraints on the early Universe star formation efficiency from galaxy clustering and halo modeling of H$\alpha$ and [O III] emitters
• Modelling the star-formation activity and ionizing properties of high-redshift galaxies
• ALMA observations of super-early galaxies: attenuation-free model predictions
• Tracing the galaxy-halo connection with galaxy clustering in COSMOS-Web from z = 0.1 to z ~ 12
• Beyond the first galaxies primordial black holes shine
• Signatures of Rapidly Rotating Stars with Chemically Homogeneous Evolution in the First Galaxies
• Explanation of high redshift luminous galaxies from JWST by early dark energy model
• The first GLIMPSE of the faint galaxy population at Cosmic Dawn with JWST: The evolution of the ultraviolet luminosity function across z~9-15
• Exploring Cosmic Dawn with PANORAMIC I: The Bright End of the UVLF at $z\sim 9-17$
• The BoRG-$JWST$ Survey: Abundance and Mass-to-light Ratio of Luminous $z=7-9$ Galaxies from Independent Sight Lines with NIRSpec
• The THESAN-ZOOM project: Star formation efficiency from giant molecular clouds to galactic scale in high-redshift starbursts
• Matching JWST UV Luminosity Functions with Refined $\Lambda$CDM Halo Models
• High-redshift Galaxies from JWST Observations in More Realistic Dark Matter Halo Models
• Dark Secrets of Baryons: Illuminating Dark Matter-Baryon Interactions with JWST
• Impact of anisotropic photon emission from sources during the epoch of reionisation
• The Cosmic Rush Hour: Rapid Formation of Bright, Massive, Disky, Star-Forming Galaxies as Signatures of Early-Universe Physics