| Name: | Anirban Chakraborty |
| Affiliation: | National Centre for Radio Astrophysics (NCRA-TIFR) |
| Conference ID : | ASI2024_136 |
| Title : | Modelling the properties of star-forming galaxies at high redshifts |
| Authors : | Anirban Chakraborty, Tirthankar Roy Choudhury |
| Authors Affiliation: | National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune-411007, India |
| Mode of Presentation: | Poster |
| Abstract Category : | Galaxies and Cosmology |
| Abstract : | Early results from the James Webb Space Telescope (JWST) observations have reported an unexpected abundance of ultraviolet (UV) bright galaxies at z ≥ 10, which appears to be in tension with the expectations from standard galaxy formation models in the ΛCDM framework at these early redshifts. In order to alleviate this tension, several cosmological as well as astrophysical interpretations have been advanced. However, these possibilities, which are needed to explain the observed excess of massive UV-luminous galaxies, can have significant implications on our understanding of the cosmic reionization history as the processes of galaxy formation and reionization are intimately connected to each other.
In this work, we build a semi-analytical model of galaxy formation and evolution to explain the rest-frame galaxy UV luminosity function (UVLF) across a wide range of redshifts (6 < z < 15). Our model also tracks the time evolution of the average ionization fraction in the intergalactic medium (IGM) and self-consistently accounts for the UV suppression in low-mass galaxies due to reionization feedback. We have constrained the free parameters of our model by simultaneously comparing the theoretical predictions with a variety of observational probes like the galaxy UVLF data from HST and JWST, recent measurements of the neutral hydrogen fraction, and the CMB scattering optical depth.
We confirm that a rapid enhancement in the star-formation efficiency and/or UV luminosity per stellar mass formed is required to reconcile with the recent JWST UVLF estimates at z ≥ 11. We further find that it is possible to jointly satisfy the current reionization constraints by adopting a mass-dependent but redshift-independent escape fraction, in which the bulk of the ionizing photons are emitted into the IGM by the fainter galaxies.
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