Low energy properties of M-state tunneling systems in metals: New candidates for non-Fermi-liquid systems

We construct a generalized multiplicative renormalization group transformation to study the low energy dynamics of a heavy particle tunneling among $M$ different positions and interacting with $N_f$ independent conduction electron channels. Using a $1/N_f$-expansion we show that this M-level scales towards a fixed point equivalent to the $N_f$ channel $SU(M) \times SU(N_f)$ Coqblin-Schrieffer model. Solving numerically the scaling equations we find that a realistic M-level system scales close to this fixed point (FP) and its Kondo temperature is in the experimentally observable range $1-10 K$.Comment: 11 Latex pages, to appear in Phys. Rev. Lett, Figures available from the author by reques

The Detection of an Extremely Bright Fast Radio Burst in a Phased Array Feed Survey

We report the detection of an ultra-bright fast radio burst FRB)from a modest, 3.4-day pilot survey with the Australian Square Kilometre Array Pathfinder. The survey was conducted in a wide- field fly’s-eye configuration using the phased-array-feed technology deployed on the array to instantaneously observe an effective area of 160 deg2, and achieve an exposure totalling 13200 deg2 hr. We constrain the position of FRB 170107 to a region 8 ́ x 8 ́ in size(90% containment)and its fluence to be 58 ± 6 Jy ms. The spectrum of the burst shows a sharp cutoff above 1400 MHz, which could be due to either scintillation or an intrinsic feature of the burst. This confirms the existence of an ultra-bright (> 20 Jy ms) population of FRBs

ASKAP HI imaging of the galaxy group IC 1459

© 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. We present HI imaging of the galaxy group IC 1459 carried out with six antennas of the Australian Square Kilometre Array Pathfinder equipped with phased-array feeds. We detect and resolve HI in 11 galaxies down to a column density of ~1020 cm-2 inside a ~6 deg2 field and with a resolution of ~1 arcmin on the sky and ~8 kms-1 in velocity. We present HI images, velocity fields and integrated spectra of all detections, and highlight the discovery of three HI clouds - two in the proximity of the galaxy IC 5270 and one close to NGC 7418. Each cloud has an HI mass of ~109 M? and accounts for ~15 per cent of the HI associated with its host galaxy. Available images at ultraviolet, optical and infrared wavelengths do not reveal any clear stellar counterpart of any of the clouds, suggesting that they are not gas-rich dwarf neighbours of IC 5270 and NGC 7418. Using Parkes data, we find evidence of additional extended, low-column-density HI emission around IC 5270, indicating that the clouds are the tip of the iceberg of a larger system of gas surrounding this galaxy. This result adds to the body of evidence on the presence of intragroup gas within the IC 1459 group. Altogether, the HI found outside galaxies in this group amounts to several times 109 M?, at least 10 per cent of the HI contained inside galaxies. This suggests a substantial flow of gas in and out of galaxies during the several billion years of the group's evolution

Wide-field broad-band radio imaging with phased array feeds: A pilot multi-epoch continuum survey with ASKAP-BETA

The Boolardy Engineering TestArray is a 6×12mdish interferometer and the prototype of the Australian Square Kilometre Array Pathfinder (ASKAP), equipped with the first generation of ASKAP's phased array feed (PAF) receivers. These facilitate rapid wide-area imaging via the deployment of simultaneous multiple beams within an ~30 deg2 field of view. By cycling the array through 12 interleaved pointing positions and using nine digitally formed beams, we effectively mimic a traditional 1 h × 108 pointing survey, covering ~150 deg2 over 711-1015 MHz in 12 h of observing time. Three such observations were executed over the course of a week. We verify the full bandwidth continuum imaging performance and stability of the system via self-consistency checks and comparisons to existing radio data. The combined three epoch image has arcminute resolution and a 1s thermal noise level of 375 µJy beam-1, although the effective noise is a factor of ~3 higher due to residual sidelobe confusion. From this we derive a catalogue of 3722 discrete radio components, using the 35 per cent fractional bandwidth to measure in-band spectral indices for 1037 of them. A search for transient events reveals one significantly variable source within the survey area. The survey covers approximately two-thirds of the Spitzer South Pole Telescope Deep Field. This pilot project demonstrates the viability and potential of using PAFs to rapidly and accurately survey the sky at radio wavelengths

The Australian Square Kilometre Array Pathfinder: Performance of the Boolardy Engineering Test Array

We describe the performance of the Boolardy Engineering Test Array, the prototype for the Australian Square Kilometre Array Pathfinder telescope. Boolardy Engineering Test Array is the first aperture synthesis radio telescope to use phased array feed technology, giving it the ability to electronically form up to nine dual-polarisation beams. We report the methods developed for forming and measuring the beams, and the adaptations that have been made to the traditional calibration and imaging procedures in order to allow BETA to function as a multi-beam aperture synthesis telescope. We describe the commissioning of the instrument and present details of Boolardy Engineering Test Array’s performance: sensitivity, beam characteristics, polarimetric properties, and image quality. We summarise the astronomical science that it has produced and draw lessons from operating Boolardy Engineering Test Array that will be relevant to the commissioning and operation of the final Australian Square Kilometre Array Path telescope

Discovery of HI gas in a young radio galaxy at z = 0.44 using the Australian Square Kilometre Array Pathfinder

We report the discovery of a new 21-cm H i absorption system using commissioning data from the Boolardy Engineering Test Array of the Australian Square Kilometre Array Pathfinder (ASKAP). Using the 711.5–1015.5 MHz band of ASKAP we were able to conduct a blind search for the 21-cm line in a continuous redshift range between z = 0.4 and 1.0, which has, until now, remained largely unexplored. The absorption line is detected at z = 0.44 towards the GHz-peaked spectrum radio source PKS B1740−517 and demonstrates ASKAP's excellent capability for performing a future wide-field survey for H i absorption at these redshifts. Optical spectroscopy and imaging using the Gemini-South telescope indicates that the H i gas is intrinsic to the host galaxy of the radio source. The narrow [O iii] emission lines show clear double-peaked structure, indicating either large-scale outflow or rotation of the ionized gas. Archival data from the XMM–Newton satellite exhibit an absorbed X-ray spectrum that is consistent with a high column density obscuring medium around the active galactic nucleus. The H i absorption profile is complex, with four distinct components ranging in width from 5 to 300 km s−1 and fractional depths from 0.2 to 20 per cent. In addition to systemic H i gas, in a circumnuclear disc or ring structure aligned with the radio jet, we find evidence for a possible broad outflow of neutral gas moving at a radial velocity of v ~ 300 km s−1. We infer that the expanding young radio source (tage ≈ 2500 yr) is cocooned within a dense medium and may be driving circumnuclear neutral gas in an outflow of ~1 M⊙ yr−1

Erratum: Discovery of H I gas in a young radio galaxy at z = 0.44 using the Australian Square Kilometre Array Pathfinder

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