HARP/ACSIS: a submillimetre spectral imaging system on the James Clerk Maxwell Telescope

Abstract

This paper describes a new Heterodyne Array Receiver Program (HARP) and Auto‐Correlation Spectral Imaging System (ACSIS) that have recently been installed and commissioned on the James Clerk Maxwell Telescope. The 16‐element focal‐plane array receiver, operating in the submillimetre from 325 to 375 GHz, offers high (three‐dimensional) mapping speeds, along with significant improvements over single‐detector counterparts in calibration and image quality. Receiver temperatures are ∼120 K across the whole band, and system temperatures of ∼300 K are reached routinely under good weather conditions. The system includes a single‐sideband (SSB) filter so these are SSB values. Used in conjunction with ACSIS, the system can produce large‐scale maps rapidly, in one or more frequency settings, at high spatial and spectral resolution. Fully sampled maps of size can be observed in under 1 h. The scientific need for array receivers arises from the requirement for programmes to study samples of objects of statistically significant size, in large‐scale unbiased surveys of galactic and extra‐galactic regions. Along with morphological information, the new spectral imaging system can be used to study the physical and chemical properties of regions of interest. Its three‐dimensional imaging capabilities are critical for research into turbulence and dynamics. In addition, HARP/ACSIS will provide highly complementary science programmes to wide‐field continuum studies and produce the essential preparatory work for submillimetre interferometers such as the Submillimeter Array (SMA) and Atacama Large Millimeter/Submillimeter Array (ALMA).

Exploring the 13CO/C18O abundance ratio towards Galactic young stellar objects and HII regions

“…The data of the other CO isotopes were obtained from the 13 CO/C 18 O (J=3-2) Heterodyne Inner Milky Way Plane Survey (CHIMPS), which have an angular and spectral resolution of 15 ′′ and 0.5 km s −1 (Rigby et al 2016). The intensities of both set of data are on the T * A scale, and it was used the mean detector efficiency η mb = 0.61 for the 12 CO, and η mb = 0.72 for the 13 CO and C 18 O to convert T * A to main beam brightness temperature (T mb = T * A /η mb ) (Buckle et al 2009). Taking into account that the CHIMPS survey covers the Galactic region in 27 • .5 ≤ l ≤ 46 • .5 and |b| ≤ 0 • .5, we selected all sources catalogued as YSOs, Hii and diffuse Hii regions lying in this area from the Red MSX Source Survey (Lumsden et al 2013), which is the largest statistically selected catalog of young massive protostars and Hii regions to date.…”

The JCMT Gould Belt Survey: first results from the SCUBA-2 observations of the Ophiuchus molecular cloud and a virial analysis of its prestellar core population

“…The HARP (Heterodyne Array Receiver Programme; Buckle et al 2009) receiver contains an array of 16 heterodyne detectors, arranged in a 4 × 4 footprint on the sky. HARP is used in conjunction with the ACSIS (AutoCorrelation Spectrometer and Imaging System; Buckle et al 2009) backend.…”

“…HARP is used in conjunction with the ACSIS (AutoCorrelation Spectrometer and Imaging System; Buckle et al 2009) backend.…”

Submillimetre Studies of Prestellar and Starless Cores in the Ophiuchus, Taurus and Cepheus Molecular Clouds

“…This is done in order to decrease system temperatures and to increase calibration accuracy. Figure 2.13: HARP-B scanning observing mode, demonstrating how fully sampled coverage is achieved using an undersampled array (from Buckle et al 2009). …”

“…HARP-B (Heterodyne Array Receiver Program for the B-Band) is a 4 × 4 element heterodyne focal plane array receiver, sensitive in the range 325-375 GHz (∼ 800-925 µm), with an angular resolution of 14 ′′ at 345 GHz, or 879µm (Buckle et al 2009). …”