New probe of the high-redshift Universe: Nulling CMB lensing with interloper-free line intensity mapping pair lensing

Abstract

Intermediate redshifts between galaxy surveys and the cosmic microwave background (CMB) remain unexplored territory. Line intensity mapping (LIM) offers a way to probe the z 1 Universe, including the epoch of reionization and the dark ages. Via exact nulling of the lensing kernel, we show that LIM lensing, in combination with galaxy (resp., CMB) lensing, can uniquely probe the z 1 (resp., pre-reionization) Universe.However, LIM foregrounds are a key hurdle to this futuristic technique. While continuum foregrounds can be controlled by discarding modes perpendicular to the line of sight (low k modes), interloper foregrounds haven't been addressed in the context of LIM lensing. In this paper, we quantify the interloper bias to LIM lensing for the first time, and derive a "LIM-pair" estimator which avoids it exactly after cross-correlating with CMB lensing. This new quadratic lensing estimator works by combining two intensity maps in different lines, from the same redshift, whose interlopers are uncorrelated. As a result, this foreground avoidance method is robust to even large changes in the amplitude of the interloper power and non-Gaussianity. The cross-spectrum of the LIM-pair estimator with CMB lensing is thus robust to the currently large theoretical uncertainties in LIM modeling at high redshift.

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

“…Cross-correlating the kSZ signal derived from the simulated ionization and velocity fields with line tracers of galaxies provides the redshift information missing in kSZ measurements. Similar ideas can be applied to other types broadband, 2D data sets such as the CMB lensing and the cosmic near-IR background, through the large-scale fluctuations of which rich information about the population of ionizing sources may be extracted (Helgason et al 2016;Sun et al 2021b;Maniyar et al 2022;Mirocha et al 2022). Furthermore, as demonstrated already in the low-z universe, 3D Lyα forest tomography serves as a promising probe of the large-scale distribution of the neutral IGM (Lee et al 2018;Newman et al 2020), which can be ideally suited for studying the late stages of the reionization process by itself or in combination with LIM data sets (Qin et al 2021a).…”

Cross-correlation Techniques to Mitigate the Interloper Contamination for Line Intensity Mapping Experiments

“…These far-reaching insights hold the potential to deepen our understanding of cosmic phenomena, uncovering the complex interplay between galaxies and the cosmic environment. Furthermore, cross-correlation studies between LIM and various tracers, including secondary Cosmic Microwave Background (CMB) anisotropies, galaxy surveys, and the cosmic Infrared background, are crucial for resolving degeneracies between astrophysical and cosmological parameters (Schaan & White 2021;Maniyar et al 2022;Fronenberg et al 2023;Zhou et al 2023b). For example, cross-correlations between LIM and 21 cm maps can be instrumental in recovering the autocorrelations within the 21 cm maps, particularly through the application of estimators like the least-squares estimator (Beane & Lidz 2018;Beane et al 2019;McBride & Liu 2023).…”

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

“…In particular, the tight connection between the emission line production and the astrophysics of interstellar gas of galaxies makes LIM a promising statistical probe of galaxy evolution. Historically, large-scale fluctuations of line intensity fields have been mainly considered for cosmological applications, such as probing alternative dark matter models, dark energy, gravitational lensing, neutrino properties, and the primordial non-Gaussianity (e.g., Sitwell et al 2014;Karkare & Bird 2018;Bernal et al 2019;Liu & Breysse 2021;Chung 2022;Maniyar et al 2022;Moradinezhad Dizgah et al 2022). The majority of astrophysical explorations of LIM have been focusing on small, nonlinear scales, where astrophysical processes of galaxy evolution are manifested through their effects on the one-halo or shot-noise components of the LIM power spectrum (e.g., Wolz et al 2017;Breysse & Alexandroff 2019;Mas-Ribas & Chang 2020;Schaan & White 2021).…”