Canadian Hydrogen Intensity Mapping Experiment (CHIME)

Transcription

1 Canadian Hydrogen Intensity Mapping Experiment (CHIME) Richard Shaw Figure 2: The CHIME telescope consists of five parabolic, cylindrical reflectors and associated radio

2 CHIME Collaboration UBC Graeme Addison Mandana Amiri Meiling Deng Mateus Fandino Kenneth Gibbs Carolin Hofer Mark Halpern Adam Hincks Gary Hinshaw Kiyo Masui Kris Sigurdson Mike Sitwell Rick Smegal Don Wiebe McGill Kevin Bandura J-F Cliche Matt Dobbs Adam Gilbert David Hanna Juan Mena Parra Graeme Smecher Amy Tang DRAO Tom Landecker Toronto/CITA Dick Bond Liam Connor Nolan Denman Peter Klages Laura Newburgh Ue-Li Pen Andre Recnick Jeff Peterson (CMU) Richard Shaw Keith Vanderlinde

3 CHIME Overview N 100m The CHIME telescope consists of five parabolic, cylindrical reflectors and associated ra and correlators. The structure is 100m 100m. Note the people in the N figure, for sca cope has no Transit moving radio parts, interferometer and maps half of the sky every day. Observe between MHz 0.5 MHz spectral resolution 1280 dual pol antennas (T recv = 50K) 120 x 2 degree FoV 15 arcmin resolution Located at DRAO in BC Beam: ~120 x 2 deg

4 CHIME Overview N 100m The CHIME telescope consists of five parabolic, cylindrical reflectors and associated ra and correlators. The structure is 100m 100m. Note the people in the N figure, for sca cope has no Transit moving radio parts, interferometer and maps half of the sky every day. Observe between MHz 0.5 MHz spectral resolution 1280 dual pol antennas (T recv = 50K) 120 x 2 degree FoV 15 arcmin resolution Located at DRAO in BC Beam: ~120 x 2 deg

5 CHIME Overview N 100m The CHIME telescope consists of five parabolic, cylindrical reflectors and associated ra and correlators. The structure is 100m 100m. Note the people in the N figure, for sca cope has no moving parts, and maps half of the sky every day. Science Goals Intensity mapping for BAOs Pulsar observations Radio transients Beam: ~120 x 2 deg

6 15 h 14 h Intensity Mapping 13 h Observe galaxies with 21cm line 12 h Automatically gives redshift Don t need to resolve individual galaxies 11 h Other experiments: BINGO(next talk), Tianlai, SKA(?) 10 h Redshift z Chang et al, 2008; Wyithe and Loeb 2008

7 15 h 14 h Intensity Mapping 13 h Observe galaxies with 21cm line 12 h Automatically gives redshift Don t need to resolve individual galaxies 11 h Other experiments: BINGO(next talk), Tianlai, SKA(?) 10 h Redshift z Chang et al, 2008; Wyithe and Loeb 2008

8 Survey Volume WiggleZ: 1.2 (h -1 Gpc) 3 BOSS LRG: 5.3 (h -1 Gpc) 3 Lyα: 37 (h -1 Gpc) 3 CHIME: 203 (h -1 Gpc) 3 Scaled such that: area of patch=volume of survey

9 Probing BAO Potentially 21cm could extend this to higher redshifts Anderson et al. 2013

10 Probing Dark Energy with CHIME 4 2 Planck 0 LCDM DD M (z) / 100 Mpc DH(z) / H Redshift z

11 CHIME Status Fully funded ($11 million) Construction due to start in early 2015 Fully operational in 2016 What are we doing in the meantime?

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13 CHIME Pathfinder 2x40m cylinders (vs 5x100m) 64 dual pol antennas per cylinder 256 correlated channels Currently operating (with reduced number of feeds)

14 CHIME Pathfinder

15 CHIME Pathfinder

16 CHIME Pathfinder

17 CHIME Pathfinder

18 Commissioning First light at the end of November with 8 feeds Installing full 256 feeds over the next month Cas A (single E-W

19 Dark Energy with CHIME Pathfinder 4 2 Planck 0 LCDM DD M (z) / 100 Mpc DH(z) / H Redshift z

20 Data Analysis Analysis is challenging: Wide field at given instant (~ 120 x 2 degrees) Effectively an all sky survey (3π sr) Data volume (>~ 1 TB/day for pathfinder) Polarisation leakage Foreground removal (> 10 6 times brighter)

21 Unpolarised Foreground Frequency / MHz 500 Polarised Foreground (Q) Frequency / MHz Frequency / MHz Simulated Sky d Foreground Problem f / degrees 0K cm Signal f / degrees 750 K 2K f / degrees 2K 140 µk Foregrounds 106 times larger than signal 140 µk

22 m-mode transform Developed m-mode formalism Transit telescopes only (stationary noise) Naturally full sky and widefield. Exact (no UV plane) Breaks problem into statistically independent modes (efficient) Published in arxiv: ; arxiv: Enables an efficient cleaning of foregrounds: Use covariance of data to find a statistical separation (KL Transform/SN eigenmodes) Fully treats mode mixing effects

23 Unpolarised Foreground Frequency / MHz 500 Polarised Foreground (Q) Frequency / MHz Frequency / MHz Simulated Sky d Foreground Cleaning f / degrees 0K cm Signal f / degrees 750 K 2K f / degrees 2K 140 µk Foregrounds 106 times larger than signal 140 µk

24 Frequency Frequency Frequency Foreground Cleaning f / degrees 750 K 2K µk 0.5 µk 2K µk 21cm Signal f / degrees µK K 290 f / degrees 2K f / degrees 30 0 KµK 440 Polarised Foreground (Q) Frequency / MHz f / degrees Unpolarised Foreground Frequency / MHz 0K Frequency / MHz S SimulatedFiltered Sky Foreground d f / degrees 0.5 µk 2K 120 µk 140 Foreground residuals significantly smaller than signal 120 µk 140

25 Power spectrum Estimation Use Optimal Quadratic Estimator (Tegmark 1997) Fractional powerspectrum errors (blue is better) 0.25 NoPol FG No FG Full FG Full FG k k / h Mpc Subtraction works well into foreground wedge k? / h Mpc

26 Summary CHIME is a new wide-field, low frequency radio interferometer intended for surveying Main goal: measure BAOs through Intensity Mapping Coming online in 2016 CHIME Pathfinder is currently taking data New techniques have been developed to address the data analysis challenges (optimality, foregrounds...)