| Name: RUPAM SARKAR |
| Affiliation: PRESIDENCY UNIVERSITY |
| Conference ID: ASI2026_140 |
| Title: Slow UV Luminosity Function Evolution Driven by evolving Star Formation time scale at $z > 10$ |
| Abstract Type: Poster |
| Abstract Category: Galaxies and Cosmology |
| Author(s) and Co-Author(s) with Affiliation: Rupam Sarkar(Presidency University, 86/1 College Street, Kolkata - 700073, India), Saumyadip Samui(Presidency University, 86/1 College Street, Kolkata - 700073, India) |
| Abstract: Recent JWST observations reveal an unexpectedly slow evolution in the ultraviolet luminosity function (UV LF) of galaxies at redshifts $z > 10$. To investigate this phenomenon, we develop a semi-analytical model of the UV LF, calibrated against well-constrained measurements at $z \sim 2-10$. Our analysis identifies a transition in star formation modes across cosmic epochs: at $z \lesssim 5$, a longer characteristic star formation timescale with nearly constant efficiency ($f_\star$) dominates, whereas at $6 \lesssim z \lesssim 10$, shorter timescales prevail without requiring an increase in $f_\star$. For $z > 10$, the slow UV LF evolution is best explained by a shift toward even shorter star formation timescale combined with same star formation efficiency as in low redshift galaxies. Further we show that a dust-free conditions or a top-heavy initial mass function (IMF) alone cannot reproduce the observations, although IMFs with lower mass cutoffs ($10-300~\rm M_\odot$) enhance UV luminosity more effectively than those with higher cutoffs ($50-300~\rm M_\odot$) at $z = 14$. By combining UV LF modeling with stellar mass constraints from \texttt{Prospector}-based SED fitting, we try to break degeneracies between IMF variations and star formation histories. Our results indicate that evolving star formation timescales rather than IMF or dust changes are the primary drivers of the observed high-redshift UV LF evolution, reflecting changing physical conditions during the earliest phases of galaxy assembly. Additionally, we show that moderate AGN activity in high redshift galaxies could further boost UV luminosities at $z \gtrsim 14$, potentially explaining the observed UV LF without changes in stellar parameters, and highlight the need for spectroscopic follow-up to assess AGN contamination. |
