Effects of Bursty Star Formation on [C ii] Line Intensity Mapping of High-redshift Galaxies

Abstract

Bursty star formation—a key prediction for high-redshift galaxies from cosmological simulations explicitly resolving stellar feedback in the interstellar medium—has recently been observed to prevail among galaxies at redshift z ≳ 6. Line intensity mapping (LIM) of the 158 μm [C ii] line as a star formation rate (SFR) indicator offers unique opportunities to tomographically constrain cosmic star formation at high redshift, in a way complementary to observations of individually detected galaxies. To understand the effects of bursty star formation on [C ii] LIM, which have remained unexplored in previous studies, we present an analytic modeling framework for high-z galaxy formation and [C ii] LIM signals that accounts for bursty star formation histories induced by delayed supernova feedback. We use it to explore and characterize how bursty star formation can impact and thus complicate the interpretation of the [C ii] luminosity function and power spectrum. Our simple analytic model indicates that bursty star formation mainly affects low-mass galaxies by boosting their average SFR and [C ii] luminosity, and in the [C ii] power spectrum it can create a substantial excess in the large-scale clustering term. This distortion results in a power spectrum shape that cannot be explained by invoking a mass-independent logarithmic scatter. We conclude that burstiness must be accounted for when modeling and analyzing [C ii] data sets from the early Universe, and that in the extreme, the signature of burstiness may be detectable with first-generation experiments such as TIME, CONCERTO, and CCAT-DSS.