Cosmological Constraints on the Global Star Formation Law of Galaxies: Insights from Baryon Acoustic Oscillation Intensity Mapping

Abstract

Originally proposed as a cosmological probe of the large-scale structure, line intensity mapping (LIM) also offers a unique window into the astrophysics of galaxy evolution. Adding to the astrophysical explorations of the LIM technique that have traditionally focused on small, nonlinear scales, we present a novel method to study the global star formation law using forthcoming data from large-scale baryonic acoustic oscillation (BAO) intensity mapping. Using the amplitude of the percent-level but scale-dependent bias induced by baryon fraction fluctuations on BAO scales, we show that combining auto- and cross-correlation power spectra of two (or more) LIM signals allows to probe the star formation law power index  . We examine the prospect for mapping Hα and [O iii] lines across all scales, especially where imprints of the baryon fraction deviation exist, with space missions like SPHEREx. We show that although SPHEREx may only marginally probe  by accessing a modest number of large-scale modes in its 200 deg2 deep survey, future infrared all-sky surveys reaching a comparable depth with an improved spectral resolution (R ≳ 400) are likely to constrain  to a precision of 10%–30%, sufficient for distinguishing models with varying feedback assumptions, out to z ∼ 4 using BAO intensity mapping. Leveraging this effect, large, cosmic-variance-limited LIM surveys in the far future can scrutinize the physical connection between galaxy evolution and the large-scale cosmological environment, while performing stringent tests of the standard cosmological model.

LIMFAST. II. Line Intensity Mapping as a Probe of High-redshift Galaxy Formation

“…In particular, because the star formation law only alters the relative gas content of galaxies instead of the amount of star formation, as illustrated in Figure 1, lines originating from the neutral ISM are most sensitive to changes in the star formation law. We note, though, that measurements of LSS using LIM signals of star formation lines from H II regions can still be useful probes of the star formation law across cosmic time (Sun 2022).…”

LIMFAST. I. A Seminumerical Tool for Line Intensity Mapping

“…While neither a universal, fixed U nor the exact anticorrelation considered may be true in reality, they illustrate how much LIM predictions might be affected by the detailed photoionization modeling of H II regions associated with the formation of massive stars. Without a good understanding of the chemical abundance and ionization conditions of H II regions in high-z galaxies, it would therefore be difficult to gauge how reliably LIM measurements of lines like [O II] and [O III] can be applied to constraining the cosmic SFRD at high redshift (Gong et al 2017;Sun 2022). We will further elaborate on this and its implications for future LIM observations in Section 4.3.…”

Constraining the halo-ISM connection through multi-transition carbon monoxide line-intensity mapping

“…Cross-correlation between LIM and galaxy surveys, for instance, will enable insights into the atomic and molecular gas content of the cross-correlated galaxies [13][14][15][16]. Just as important are LIM-LIM cross-correlations, particularly between 21 cm IM and cmto mm-wave LIM in star-formation lines [17][18][19], but also between different star-formation lines [20][21][22][23] -in some cases even within the same survey. For instance, the CO Mapping Array Project (COMAP; [24]), a single-dish CO LIM experiment, is currently in a Pathfinder phase operating at observing frequencies of 26-34 GHz and primarily targeting CO(1-0) at z ∼ 3.…”