Exploring the high-mass end of the stellar mass function of star forming galaxies at cosmic noon

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Sherman, Sydney Beth

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We present the high-mass end of the galaxy stellar mass function using the largest sample to date (5,352) of star-forming galaxies with M[subscript star] > 10¹¹M[subscript circled dot] at cosmic noon, 1.5 < z < 3.5. This sample is uniformly selected across 17.2 deg² (~0.44 Gpc³ comoving volume from 1.5 < z < 3.5), mitigating the effects of cosmic variance and encompassing a wide range of environments. This area, a factor of 10 larger than previous studies, provides robust statistics at the high-mass end. Using multi-wavelength data in the Spitzer/HETDEX Exploratory Large Area (SHELA) footprint we find that the SHELA footprint star-forming galaxy stellar mass function is steeply declining at the high-mass end probing values as high as ~ 10⁻⁴ Mpc³/dex and as low as ~ 5 X 10⁸ Mpc³/dex across a stellar mass range of log(M[subscript star]/M[subscript circled dot]) ~ 11 - 12. We compare our empirical star-forming galaxy stellar mass function at the high mass end to three types of numerical models: hydrodynamical models from IllustrisTNG, abundance matching from the UniverseMachine, and three different semi-analytic models (SAMs; SAG, SAGE, GALACTICUS). At redshifts 1.5 < z < 3.5 we find that results from IllustrisTNG and abundance matching models agree within a factor of ~2 to 10, however the three SAMs strongly underestimate (up to a factor of 1,000) the number density of massive galaxies. We discuss the implications of these results for our understanding of galaxy evolution



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