2024/12/09 by Fengwu Sun, Sun, Fengwu, Feige Wang +53 · 4 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Scientific Research and Discoveries #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2412.06894
openalex publication_date 2024/12/09 · openalex created_date 2024/12/12 · openalex updated_date 2026/08/01
We present a stringent measurement of the dust-obscured star-formation rate density (SFRD) at z=4-6 from the ASPIRE JWST Cycle-1 medium and ALMA Cycle-9 large program. We obtained JWST/NIRCam grism spectroscopy and ALMA 1.2-mm continuum map along 25 independent quasar sightlines, covering a total survey area of ∼35 arcmin2 where we search for dusty star-forming galaxies (DSFGs) at z = 0 - 7. We identify eight DSFGs in seven fields at z=4-6 through the detection of Hα or [O III] λ5008 lines, including fainter lines such as Hβ, [O III] λ4960, [N II] λ6585, [S II] λλ6718,6733 for six sources. With this spectroscopically complete DSFG sample at z=4-6 and negligible impact from cosmic variance (shot noise), we measure the infrared luminosity function (IRLF) down to LIR ∼ 2×1011 L_\odot. We find flattening of IRLF at z=4-6 towards the faint end (power-law slope α= 0.59-0.45+0.39). We determine the dust-obscured cosmic SFRD at this epoch as log[ρSFR,IR / (M_\odot yr-1 Mpc-3)] = -1.52-0.13+0.14. This is significantly higher than previous determination using ALMA data in the Hubble Ultra Deep Field, which is void of DSFGs at z=4-6 because of strong cosmic variance (shot noise). We conclude that the majority (66±7%) of cosmic star formation at z ∼ 5 is still obscured by dust. We also discuss the uncertainty of SFRD propagated from far-IR spectral energy distribution and IRLF at the bright end, which will need to be resolved with future ALMA and JWST observations.