Canadian Hydrogen Intensity Mapping Experiment

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CHIME telescope
One of the four semi-cylindrical reflectors

The Canadian Hydrogen Intensity Mapping Experiment  (CHIME) is a Canadian radio telescope . It is part of the Dominion Radio Astrophysical Observatory  (DRAO) and is located in rural British Columbia (Okanagan Valley near Okanagan Falls ).

history

The CHIME has been in operation since 2017 ( First Light on September 7, 2017). A smaller prototype was built from 2013, the telescope from 2015.

technology

The radio telescope follows a new design: it has no moving parts, but consists of four side by side, north-south oriented, open at the top half-cylinders (each 20 × 100 m). These have 256 dual- polarized individual receivers in their focal axes (a total of 1024), which scan a large section of the northern sky (around 200 ° square), with different sections being recorded as the earth rotates . Observations are carried out in a broad frequency band from 400–800 MHz. For the amplification, amplifiers from the mobile communications industry with low noise are used, which contributes to the cost-effectiveness.

Computer hardware and software are used extensively. The signals (a total of 2048 from the 1024 individual receivers, each with two polarizations) are processed with high-performance computers - on site in the first digital signal processing in the F-Engine, housed in several containers, with inexpensive FPGA technology and the X-Engine, which together produce 250 kW and process 13 tera bits of data per second  . For the filtering out the FRB signals (pre-processed in the X-engine, consisting of 256 nodes with graphics processors  is (GPU)), a computer 128 nodes with over 2500  CPU - cores and 32.000 gigabytes of  RAM used.

Applications

Originally the CHIME was intended for cosmological purposes, namely a scan and the creation of a three-dimensional map of the hydrogen density in the universe; from this u. a. the expansion history of the universe and the role of dark energy are reconstructed. For this purpose, the cosmological development of the first structures ( baryonic acoustic oscillation  (BAO) in the CMB ) is followed. The BAO was previously determined by measuring individual galaxies and their redshifts , but the measurement aimed at CHIME using the 21 cm line of interstellar hydrogen gas ( Hydrogen Intensity Mapping , HI) can be carried out much more extensively, faster and more efficiently.

The first spectacular discoveries, however, were many new fast radio bursts , very fast (a few milliseconds) transients (bursts) in the radio range, probably from other galaxies. Your explanation is open (including the Blitzar model). Around 25 FRBs were discovered between 2007 and 2017, around a dozen by CHIME in the start-up phase (2018), and 2 to 50 new FRBs are expected every day. In 2018, the second repeating FRB ever was observed there (FRB 180814). The physicist Kendrick Smith of the Perimeter Institute , who received the New Horizons in Physics Prize  2020 in particular, played a key role in this .

Another application is the search for pulsars and the recording of their precise temporal dynamics ( pulsar timing ): the CHIME is supposed to observe around ten pulsars at the same time around the clock. This serves to research the physics of pulsars, to test gravitational theories (pulsars led to the first indirect detection of gravitational waves in the 1970s ) and to research large-scale dynamics that extend over long periods (years), for example caused by gravitational waves from the fusion of supermassive black holes ( Pulsar Timing Array , in collaboration with other telescopes).

literature

  • Davide Castelvecchi: 'Half-pipe' telescope wants probe dark energy in teen Universe . In: Nature News . tape 523 , no. 7562 , July 30, 2015, p. 514 , doi : 10.1038 / 523514a .
  • K. Bandura et al. a .: ICE: a scalable, low-cost FPGA-based telescope signal processing and networking system , Arxiv 2016
  • CHIME / FRB Collaboration (M. Amiri et al.): The CHIME Fast Radio Burst Project: System Overview . In: The Astrophysical Journal . tape 863 , no. 1 , August 2018, p. 48 , doi : 10.3847 / 1538-4357 / aad188 , arxiv : 1803.11235 .

Web links

Individual evidence

  1. ↑ Kevin Bandura et al. a .: Canadian Hydrogen Intensity Mapping Experiment (CHIME) pathfinder . In: Ground-based and Airborne Telescopes V . tape 9145 . International Society for Optics and Photonics, 2014, p. 914522 , doi : 10.1117 / 12.2054950 , arxiv : 1406.2288 .
  2. ↑ Nolan Denman et al. a .: A GPU-based correlator X-engine implemented on the CHIME Pathfinder . In: 2015 IEEE 26th International Conference on Application-specific Systems, Architectures and Processors (ASAP) . 2015, p. 35-40 , doi : 10.1109 / ASAP.2015.7245702 , arxiv : 1503.06202 .
  3. ↑ To be followed up in the future e.g. B. in the Dark Energy Survey , Euclid and the Dark Energy Spectroscopic Instrument  (DESI).
  4. ↑ For FRB 121102 it was shown that the FRBs are repetitive and originate from a small dwarf galaxy with a redshift 0.2
  5. ↑ CHIME / FRB Collaboration: A second source of repeating fast radio bursts . In: Nature . tape 566 , no. 7743 , February 2019, p. 235-238 , doi : 10.1038 / s41586-018-0864-x , arxiv : 1901.04525 .