First Light for the First Station of the Long Wavelength Array

TL;DR

The Long Wavelength Array's first station, LWA1, is a highly sensitive, versatile radio telescope operating between 10-88 MHz, enabling advanced studies in astrophysics, transient phenomena, and space weather with unique observational capabilities.

Contribution

This paper reports the first light and commissioning results of LWA1, a novel, highly sensitive meter-wavelength radio telescope with multiple beams and transient buffer modes for diverse astrophysical research.

Findings

LWA1 has a system equivalent flux density of ~3 kJy at zenith.

LWA1 provides four steerable beams with 16 MHz bandwidth each.

LWA1 has demonstrated potential for pulsar and sky imaging observations.

Abstract

The first station of the Long Wavelength Array (LWA1) was completed in April 2011 and is currently performing observations resulting from its first call for proposals in addition to a continuing program of commissioning and characterization observations. The instrument consists of 258 dual-polarization dipoles, which are digitized and combined into beams. Four independently-steerable dual-polarization beams are available, each with two "tunings" of 16 MHz bandwidth that can be independently tuned to any frequency between 10 MHz and 88 MHz. The system equivalent flux density for zenith pointing is ~3 kJy and is approximately independent of frequency; this corresponds to a sensitivity of ~5 Jy/beam (5sigma, 1 s); making it one of the most sensitive meter-wavelength radio telescopes. LWA1 also has two "transient buffer" modes which allow coherent recording from all dipoles simultaneously, providing instantaneous all-sky field of view. LWA1 provides versatile and unique new capabilities for Galactic science, pulsar science, solar and planetary science, space weather, cosmology, and searches for astrophysical transients. Results from LWA1 will detect or tightly constrain the presence of hot Jupiters within 50 parsecs of Earth. LWA1 will provide excellent resolution in frequency and in time to examine phenomena such as solar bursts, and pulsars over a 4:1 frequency range that includes the poorly understood turnover and steep-spectrum regimes. Observations to date have proven LWA1's potential for pulsar observing, and just a few seconds with the completed 256-dipole LWA1 provide the most sensitive images of the sky at 23 MHz obtained yet. We are operating LWA1 as an open skies radio observatory, offering ~2000 beam-hours per year to the general community.