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- Title
- A SPectroscopic Survey of Biased Halos in the Reionization Era (ASPIRE): Spectroscopically Complete Census of Obscured Cosmic Star Formation Rate Density at z=4-6
- KIAS Author
- Jun, Hyunsung D.
- Journal
- ASTROPHYSICAL JOURNAL, 2025
- Archive
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- Abstract
- 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 similar to 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 H alpha or [O iii] lambda 5008 lines, including fainter lines such as H beta, [O iii] lambda 4960, [N ii] lambda 6585, and [S ii] lambda lambda 6718,6733 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 similar to 2 x 1011 L circle dot. We find flattening of IRLF at z = 4-6 towards the faint end (power-law slope alpha=0.59-0.45+0.39 ). We determine the dust-obscured cosmic SFRD at this epoch to be log[rho SFR,IR/(M circle dot yr-1Mpc-3)]=-1.52-0.13+0.14 . This is significantly higher than previous determinations 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 similar to 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.
