The TIME-Pilot intensity mapping experiment

Abstract

TIME-Pilot is designed to make measurements from the Epoch of Reionization (EoR), when the first stars and galaxies formed and ionized the intergalactic medium. This will be done via measurements of the redshifted 157.7 um line of singly ionized carbon ([CII]). In particular, TIME-Pilot will produce the first detection of [CII] clustering fluctuations, a signal proportional to the integrated [CII] intensity, summed over all EoR galaxies. TIME-Pilot is thus sensitive to the emission from dwarf galaxies, thought to be responsible for the balance of ionizing UV photons, that will be difficult to detect individually with JWST and ALMA. A detection of [CII] clustering fluctuations would validate current theoretical estimates of the [CII] line as a new cosmological observable, opening the door for a new generation of instruments with advanced technology spectroscopic array focal planes that will map [CII] fluctuations to probe the EoR history of star formation, bubble size, and ionization state. Additionally, TIME-Pilot will produce high signal-to-noise measurements of CO clustering fluctuations, which trace the role of molecular gas in star-forming galaxies at redshifts 0 < z < 2. With its unique atmospheric noise mitigation, TIME-Pilot also significantly improves sensitivity for measuring the kinetic Sunyaev-Zel'dovich (kSZ) effect in galaxy clusters. TIME-Pilot will employ a linear array of spectrometers, each consisting of a parallel-plate diffraction grating. The spectrometer bandwidth covers 185-323 GHz to both probe the entire redshift range of interest and to include channels at the edges of the band for atmospheric noise mitigation. We illuminate the telescope with f/3 horns, which balances the desire to both couple to the sky with the best efficiency per beam, and to pack a large number of horns into the fixed field of view. Feedhorns couple radiation to the waveguide spectrometer gratings. Each spectrometer grating has 190 facets and provides resolving power above 100. At this resolution, the longest dimension of the grating is 31 cm, which allows us to stack gratings in two blocks (one for each polarization) of 16 within a single cryostat, providing a 1x16 array of beams in a 14 arcminute field of view. Direct absorber TES sensors sit at the output of the grating on six linear facets over the output arc, allowing us to package and read out the detectors as arrays in a modular manner. The 1840 detectors will be read out with the NIST time-domain-multiplexing (TDM) scheme and cooled to a base temperature of 250 mK with a 3He sorption refrigerator. We present preliminary designs for the TIME-Pilot cryogenics, spectrometers, bolometers, and optics.

Cosmology with intensity mapping techniques using atomic and molecular lines

“…In table 4 we summarize the assumed experimental details. For full details of TIME and TIMEPilot please refer to Staniszewski et al (2014) and to Crites et al (2014). Note that we assume the number of bolometers is the same.…”

Lithographed spectrometers for tomographic line mapping of the Epoch of Reionization

“…For a star-formation rate sufficient to sustain reionization and [CII] brightness and metallicities matching lower redshift observations, TIME-Pilot should detect the clustering term of the [CII] spectrum with S/N ∼ 10 after approximately a month of observing time at Mauna Kea. 11 Detailed studies of the redshift history of the signal will require more sensitivity, and finer spatial and spectral resolution may be required to successfully mask out CO foregrounds. TIME-Pilot uses established technology to rapidly begin observations and to begin the search for a signal.…”

Constraining the evolution of [C ii] intensity through the end stages of reionization

“…There are several planned experiments that aim to place constraints on the integrated intensity of [CII] over the epoch of reionization, including (i) the Cerro Chajnantor Atacama Telescope (CCAT-prime; Parshley et al 2018) 1 which plans to trace [CII] over z ∼ 5 − 8, probing the late stages of reionization, (ii) the Tomographic Intensity Mapping Experiment (TIME; e.g., Crites et al 2014Crites et al , 2017 and (iii) the CarbON CII line in post-rEionization and ReionizaTiOn (CONCERTO; Serra et al 2016;Lagache 2018) experiment 2 which plans to observe the evolution of CII over z ∼ 4.5 − 8.5. Above z ∼ 4, the [CII] line redshifts into the millimetre wavelengths, where the Atacama Large Millimetre Array (ALMA) facility can make observations in the single dish mode; the ALMA bands 7 and 8 enable [CII] emission observations from z ∼ 2.8 − 5.…”