HI 21cm Cosmology and the Bi-spectrum: Closure Diagnostics in Massively Redundant Interferometric Arrays
Creators: name: Carilli, C. L.
name: Nikolic, Bojan
name: Thyagarajan, Nithyanandan
name: Gale-Sides, K.
name: Abdurashidova, Zara
name: Aguirre, James E.
name: Alexander, Paul
name: Ali, Zaki S.
name: Balfour, Yanga
name: Beardsley, Adam P.
name: Bernardi, Gianni
name: Bowman, Judd D.
name: Bradley, Richard F.
name: Burba, Jacob
name: Cheng, Carina
name: DeBoer, David R.
name: Dexter, Matt
name: de~Lera~Acedo, Eloy
name: Dillon, Joshua S.
name: Ewall-Wice, Aaron
name: Fadana, Gcobisa
name: Fagnoni, Nicolas
name: Fritz, Randall
name: Furlanetto, Steve R.
name: Ghosh, Abhik
name: Glendenning, Brian
name: Greig, Bradley
name: Grobbelaar, Jasper
name: Halday, Ziyaad
name: Hazelton, Bryna J.
name: Hewitt, Jacqueline N.
name: Hickish, Jack
name: Jacobs, Daniel C.
name: Julius, Austin
name: Kariseb, MacCalvin
name: Kohn, Saul A.
name: Kolopanis, Mathew
name: Lekalake, Telalo
name: Liu, Adrian
name: Loots, Anita
name: MacMahon, David
name: Malan, Lourence
name: Malgas, Cresshim
name: Maree, Matthys
name: Martinot, Zachary
name: Matsetela, Eunice
name: Mesinger, Andrei
name: Molewa, Mathakane
name: Morales, Miguel F.
name: Neben, Abraham R.
name: Parsons, Aaron R.
name: Patra, Nipanjana
name: Pieterse, Samantha
name: La Plante, Paul
name: Pober, Jonathan C.
name: Razavi-Ghods, Nima
name: Ringuette, Jon
name: Robnett, James
name: Rosie, Kathryn
name: Sell, Raddwine
name: Sims, Peter
name: Smith, Craig
name: Syce, Angelo
name: Williams, Peter K. ~G.
name: Zheng, Haoxuan
Publisher: name: arXiv
Year: 2018
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: New massively redundant low frequency arrays allow for a novel investigation of closure relations in interferometry. We employ commissioning data from the Hydrogen Epoch of Reionization Array to investigate closure quantities in this densely packed grid array of 14m antennas operating at 100 MHz to 200 MHz. We investigate techniques that utilize closure phase spectra for redundant triads to estimate departures from redundancy for redundant baseline visibilities. We find a median absolute deviation from redundancy in closure phase across the observed frequency range of about 4.5deg. This value translates into a non-redundancy per visibility phase of about 2.6deg, using prototype electronics. The median absolute deviations from redundancy decrease with longer baselines. We show that closure phase spectra can be used to identify ill-behaved antennas in the array, independent of calibration. We investigate the temporal behavior of closure spectra. The Allan variance increases after a one minute stride time, due to passage of the sky through the primary beam of the transit telescope. However, the closure spectra repeat to well within the noise per measurement at corresponding local sidereal times (LST) from day to day. In future papers in this series we will develop the technique of using closure phase spectra in the search for the HI 21cm signal from cosmic reionization.
description: 32 pages. 11 figures. Accepted to Radio Science