Confirmation of a Substantial Discrepancy between Radio and UV–IR Measures of the Star Formation Rate Density at 0.2 < z < 1.3

Abstract

We present the initial sample of redshifts for 3839 galaxies in the MeerKAT DEEP2 field—the most sensitive ∼1.4 GHz radio field yet observed with σ _n = 0.55 μ Jy beam ^−1 , reaching the confusion limit. Using a spectrophotometric technique combining coarse optical spectra with broadband photometry, we obtain redshifts with σ _z ≲ 0.01(1 + z ), as determined from repeat observations. The resulting radio luminosity functions between 0.2 < z < 1.3 from our sample of 3839 individual galaxies are in remarkable agreement with those inferred from previous modeling of radio source counts, confirming a ≳50% excess in radio-based star formation rate density (SFRD) ( z ) measurements at 0.2 < z < 1.3 compared to those from the UV–IR. Several sources of systematic error are discussed—totalling ∼0.13 dex when added in quadrature. Even in the event that all systematic errors work to decrease the radio-based SFRD values, they are incapable of reconciling differences between the radio-based measurements with those from the UV–IR at 0.5 < z < 1.3. We conclude that significant work remains to have confidence in a full accounting of the star formation budget of the Universe.

Keywords

• Radio continuum emission
• Radio source counts
• Cosmological evolution
• Galaxy evolution
• Galaxy counts