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Abstract We report 10 fast radio bursts (FRBs) detected in the far sidelobe region (i.e., ≥5° off-meridian) of the Canadian Hydrogen Intensity Mapping Experiment (CHIME) from August 28 2018 to August 31 2021. We localize the bursts by fitting their spectra with a model of the CHIME/FRB synthesized beam response. We find that the far sidelobe events have on average ∼500 times greater fluxes than events detected in CHIME’s main lobe. We show that the sidelobe sample is therefore statistically ∼20 times closer than the main lobe sample. We find promising host galaxy candidates (P_cc< 1%) for two of the FRBs, 20190112B and 20210310B, at distances of 38 and 16 Mpc, respectively. CHIME/FRB did not observe repetition of similar brightness from the uniform sample of 10 sidelobe FRBs in a total exposure time of 35,580 hr. Under the assumption of Poisson-distributed bursts, we infer that the mean repetition interval above the detection threshold of the far sidelobe events is longer than 11,880 hr, which is at least 2380 times larger than the interval from known CHIME/FRB detected repeating sources, with some caveats, notably that very narrowband events could have been missed. Our results from these far sidelobe events suggest one of two scenarios: either (1) all FRBs repeat and the repetition intervals span a wide range, with high-rate repeaters being a rare sub-population, or (2) non-repeating FRBs are a distinct population different from known repeaters. 

Abstract We report the detection of 21 cm emission at an average redshift $\overline{z}=2.3$in the cross-correlation of data from the Canadian Hydrogen Intensity Mapping Experiment (CHIME) with measurements of the Lyαforest from eBOSS. Data collected by CHIME over 88 days in the 400–500 MHz frequency band (1.8 <z< 2.5) are formed into maps of the sky and high-pass delay filtered to suppress the foreground power, corresponding to removing cosmological scales withk_∥≲ 0.13 Mpc⁻¹at the average redshift. Line-of-sight spectra to the eBOSS background quasar locations are extracted from the CHIME maps and combined with the Lyαforest flux transmission spectra to estimate the 21 cm–Lyαcross-correlation function. Fitting a simulation-derived template function to this measurement results in a 9σdetection significance. The coherent accumulation of the signal through cross-correlation is sufficient to enable a detection despite excess variance from foreground residuals ∼6–10 times brighter than the expected thermal noise level in the correlation function. These results are the highest-redshift measurement of 21 cm emission to date, and they set the stage for future 21 cm intensity mapping analyses atz> 1.8. 

Abstract Localizing fast radio bursts (FRBs) to their host galaxies is an essential step to better understanding their origins and using them as cosmic probes. The Canadian Hydrogen Intensity Mapping Experiment (CHIME)/FRB Outriggers program aims to add very long baseline interferometry localization capabilities to CHIME, such that FRBs may be localized to tens of milliarcsecond precision at the time of their discovery, more than sufficient for host galaxy identification. The first-built outrigger telescope is theOutrigger (KKO), located 66 km west of CHIME. Cross-correlating KKO with CHIME can achieve arcsecond precision along the baseline axis while avoiding the worst effects of the ionosphere. Since the CHIME–KKO baseline is mostly east/west, this improvement is mostly in right ascension. This paper presents measurements of KKO’s performance throughout its commissioning phase, as well as a summary of its design and function. We demonstrate KKO’s capabilities as a standalone instrument by producing full-sky images, mapping the angular and frequency structure of the primary beam, and measuring feed positions. To demonstrate the localization capabilities of the CHIME–KKO baseline, we collected five separate observations each, for a set of 20 bright pulsars, and aimed to measure their positions to within 5″. All of these pulses were successfully localized to within this specification. The next two outriggers are expected to be commissioned in 2024 and will enable subarcsecond localizations for approximately hundreds of FRBs each year. 

Abstract In 2021, a catalog of 536 fast radio bursts (FRBs) detected with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) radio telescope was released by the CHIME/FRB Collaboration. This large collection of bursts, observed with a single instrument and uniform selection effects, has advanced our understanding of the FRB population. Here we update the results for 140 of these FRBs for which channelized raw voltage (“baseband”) data are available. With the voltages measured by the telescope’s antennas, it is possible to maximize the telescope sensitivity in any direction within the primary beam, an operation called “beamforming.” This allows us to increase the signal-to-noise ratios of the bursts and to localize them to subarcminute precision. The improved localizations are also used to correct the beam response of the instrument and to measure fluxes and fluences with an ∼10% uncertainty. Additionally, the time resolution is increased by 3 orders of magnitude relative to that in the first CHIME/FRB catalog, and, applying coherent dedispersion, burst morphologies can be studied in detail. Polarization information is also available for the full sample of 140 FRBs, providing an unprecedented data set to study the polarization properties of the population. We release the baseband data beamformed to the most probable position of each FRB. These data are analyzed in detail in a series of accompanying papers. 

Abstract We present a detection of 21 cm emission from large-scale structure (LSS) between redshift 0.78 and 1.43 made with the Canadian Hydrogen Intensity Mapping Experiment. Radio observations acquired over 102 nights are used to construct maps that are foreground filtered and stacked on the angular and spectral locations of luminous red galaxies (LRGs), emission-line galaxies (ELGs), and quasars (QSOs) from the eBOSS clustering catalogs. We find decisive evidence for a detection when stacking on all three tracers of LSS, with the logarithm of the Bayes factor equal to 18.9 (LRG), 10.8 (ELG), and 56.3 (QSO). An alternative frequentist interpretation, based on the likelihood ratio test, yields a detection significance of 7.1σ(LRG), 5.7σ(ELG), and 11.1σ(QSO). These are the first 21 cm intensity mapping measurements made with an interferometer. We constrain the effective clustering amplitude of neutral hydrogen (Hi), defined as ${\mathit{}}_{\mathrm{H}\mathrm{I}}\equiv {10}^3{\mathrm{\Omega }}_{\mathrm{H}\mathrm{I}}\left(b_{\mathrm{H}\mathrm{I}}+〈f{\mu }^2〉\right)$, where Ω_Hiis the cosmic abundance of Hi,b_Hiis the linear bias of Hi, and 〈fμ²〉 = 0.552 encodes the effect of redshift-space distortions at linear order. We find ${\mathit{}}_{\mathrm{H}\mathrm{I}}={1.51}_{-0.97}^{+3.60}$for LRGs (z= 0.84), ${\mathit{}}_{\mathrm{H}\mathrm{I}}={6.76}_{-3.79}^{+9.04}$for ELGs (z= 0.96), and ${\mathit{}}_{\mathrm{H}\mathrm{I}}={1.68}_{-0.67}^{+1.10}$for QSOs (z= 1.20), with constraints limited by modeling uncertainties at nonlinear scales. We are also sensitive to bias in the spectroscopic redshifts of each tracer, and we find a nonzero bias Δv= − 66 ± 20 km s⁻¹for the QSOs. We split the QSO catalog into three redshift bins and have a decisive detection in each, with the upper bin atz= 1.30 producing the highest-redshift 21 cm intensity mapping measurement thus far. 

Abstract We present a beam pattern measurement of the Canadian Hydrogen Intensity Mapping Experiment (CHIME) made using the Sun as a calibration source. As CHIME is a pure drift-scan instrument, we rely on the seasonal north–south motion of the Sun to probe the beam at different elevations. This semiannual range in elevation, combined with the radio brightness of the Sun, enables a beam measurement that spans ∼7200 square degrees on the sky without the need to move the telescope. We take advantage of observations made near solar minimum to minimize the impact of solar variability, which is observed to be <10% in intensity over the observation period. The resulting data set is highly complementary to other CHIME beam measurements—both in terms of angular coverage and systematics—and plays an important role in the ongoing program to characterize the CHIME primary beam.