An Overview of CHIME, the Canadian Hydrogen Intensity Mapping Experiment

Abstract

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a drift scan radio telescope operating across the 400–800 MHz band. CHIME is located at the Dominion Radio Astrophysical Observatory near Penticton, BC, Canada. The instrument is designed to map neutral hydrogen over the redshift range 0.8–2.5 to constrain the expansion history of the universe. This goal drives the design features of the instrument. CHIME consists of four parallel cylindrical reflectors, oriented north–south, each 100 m × 20 m and outfitted with a 256-element dual-polarization linear feed array. CHIME observes a two-degree-wide stripe covering the entire meridian at any given moment, observing three-quarters of the sky every day owing to Earth’s rotation. An FX correlator utilizes field-programmable gate arrays and graphics processing units to digitize and correlate the signals, with different correlation products generated for cosmological, fast radio burst, pulsar, very long baseline interferometry, and 21 cm absorber back ends. For the cosmology back end, the N feed 2 correlation matrix is formed for 1024 frequency channels across the band every 31 ms. A data receiver system applies calibration and flagging and, for our primary cosmological data product, stacks redundant baselines and integrates for 10 s. We present an overview of the instrument, its performance metrics based on the first 3 yr of science data, and we describe the current progress in characterizing CHIME’s primary beam response. We also present maps of the sky derived from CHIME data; we are using versions of these maps for a cosmological stacking analysis, as well as for investigation of Galactic foregrounds.

Wide-band Timing of the Parkes Pulsar Timing Array UWL Data

“…There are a number of possible improvements that can be applied to observational strategies, instrumentation, and analysis techniques, such as increasing the number of pulsars in the array and the cadence of observations, or enlarging telescope apertures. In particular, several recent projects and facilities, such as the Five Hundred Meter Aperture Spherical Telescope (FAST; Hobbs et al 2019) and the Canadian Hydrogen Intensity Mapping Experiment (CHIME/Pulsar Project; Amiri et al 2021Amiri et al , 2022, will soon join PTA efforts and significantly increase available observing time and collecting area.…”

Statistical Association between the Candidate Repeating FRB 20200320A and a Galaxy Group

“…Furthermore, FRB 20200320A has a scattering timescale of 2.46(3) ms at 600 MHz (see Figure 13 of CHIME/FRB Collaboration 2023), 1% of which could be produced by the Galactic interstellar medium (ISM) based on the NE2001 and YMW16 models. Given the FRB redshift, the remaining 99% of scattering could originate from the host CGM and circum-burst environment (Macquart & Koay 2013;Masui et al 2015;Prochaska & Neeleman 2018;Chawla et al 2022;Ocker et al 2023;Sammons et al 2023). In sharp contrast, FRB 20201105A (the second burst from presumably the same source) has a scattering timescale of = 1 ms at 600 MHz (CHIME/FRB Collaboration 2023).…”

Cosmic Tidal Reconstruction in Redshift Space

“…The isotropic modulation to the local power spectrum can also give an estimate of the large-scale density by measuring the amplitude of the small-scale power spectrum in different subvolumes (e.g., Chiang et al 2014;Li et al 2014;Chiang et al 2015) or using a tidal field quadratic estimator as we presented here. However, compared with the local anisotropic distortions, the isotropic modulation is more likely to be impacted by observational systematics, e.g., variations in the foreground stars, seeing, and galactic dust extinction, since both lead to the change in the local galaxy power spectrum.…”