Christopher A. Hales

EMU: Evolutionary Map of the Universe

EMU is a wide-field radio continuum survey planned for the new Australian Square Kilometre Array Pathfinder (ASKAP) telescope. The primary goal of EMU is to make a deep (rms ~10 μJy/beam) radio continuum survey of the entire Southern sky at 1.3 GHz, extending as far North as +30° declination, with a resolution of 10 arcsec. EMU is expected to detect and catalogue about 70 million galaxies, including typical star-forming galaxies up to z ~ 1, powerful starbursts to even greater redshifts, and active galactic nuclei to the edge of the visible Universe. It will undoubtedly discover new classes of object. This paper defines the science goals and parameters of the survey, and describes the development of techniques necessary to maximise the science return from EMU.

blobcat: software to catalogue flood-filled blobs in radio images of total intensity and linear polarization

We present BLOBCAT, new source extraction software that utilises the flood fill algorithm to detect and catalogue blobs, or islands of pixels representing sources, in twodimensional astronomical images. The software is designed to process radio-wavelength images of both Stokes I intensity and linear polarization, the latter formed through the quadrature sum of Stokes Q and U intensities or as a byproduct of rotation measure synthesis. We discuss an objective, automated method by which estimates of positiondependent background root-mean-square noise may be obtained and incorporated into BLOBCAT’s analysis. We derive and implement within BLOBCAT corrections for two systematic biases to enable the flood fill algorithm to accurately measure flux densities for Gaussian sources. We discuss the treatment of non-Gaussian sources in light of these corrections. We perform simulations to validate the flux density and positional measurement performance of BLOBCAT, and we benchmark the results against those of a standard Gaussian fitting task. We demonstrate that BLOBCAT exhibits accurate measurement performance in total intensity and, in particular, linear polarization. BLOBCAT is particularly suited to the analysis of large survey data.

The radio properties of infrared-faint radio sources

Context. Infrared-faint radio sources (IFRS) are objects that have flux densities of several mJy at 1.4 GHz, but that are invisible at 3.6 µm when using sensitive Spitzer observations with mu Jy sensitivities. Their nature is unclear and difficult to investigate since they are only visible in the radio. Aims. High-resolution radio images and comprehensive spectral coverage can yield constraints on the emission mechanisms of IFRS and can give hints to similarities with known objects. Methods. We imaged a sample of 17 IFRS at 4.8 GHz and 8.6 GHz with the Australia Telescope Compact Array to determine the structures on arcsecond scales. We added radio data from other observing projects and from the literature to obtain broad-band radio spectra. Results. We find that the sources in our sample are either resolved out at the higher frequencies or are compact at resolutions of a few arcsec, which implies that they are smaller than a typical galaxy. The spectra of IFRS are remarkably steep, with a median spectral index of -1.4 and a prominent lack of spectral indices larger than -0.7. We also find that, given the IR non-detections, the ratio of 1.4 GHz flux density to 3.6 µm flux density is very high, and this puts them into the same regime as high-redshift radio galaxies. Conclusions. The evidence that IFRS are predominantly high-redshift sources driven by active galactic nuclei (AGN) is strong, even though not all IFRS may be caused by the same phenomenon. Compared to the rare and painstakingly collected high-redshift radio galaxies, IFRS appear to be much more abundant, but less luminous, AGN-driven galaxies at similar cosmological distances.

HIGHEST REDSHIFT IMAGE of NEUTRAL HYDROGEN in EMISSION: A CHILES DETECTION of A STARBURSTING GALAXY at z = 0.376

Our current understanding of galaxy evolution still has many uncertainties associated with the details of accretion, processing, and removal of gas across cosmic time. The next generation of radio telescopes will image the neutral hydrogen (HI) in galaxies over large volumes at high redshifts, which will provide key insights into these processes. We are conducting the COSMOS HI Large Extragalactic Survey (CHILES) with the Karl G. Jansky Very Large Array, which is the first survey to simultaneously observe HI from z=0 to z~0.5. Here, we report the highest redshift HI 21-cm detection in emission to date of the luminous infrared galaxy (LIRG) COSMOS J100054.83+023126.2 at z=0.376 with the first 178 hours of CHILES data. The total HI mass is

ATLAS - I. Third release of 1.4 GHz mosaics and component catalogues

(2.9\pm1.0)\times10^{10}~M_\odot

CONSTRAINING THE PROPER MOTIONS OF TWO MAGNETARS

, and the spatial distribution is asymmetric and extends beyond the galaxy. While optically the galaxy looks undisturbed, the HI distribution suggests an interaction with candidate a candidate companion. In addition, we present follow-up Large Millimeter Telescope CO observations that show it is rich in molecular hydrogen, with a range of possible masses of

Analytic detection thresholds for measurements of linearly polarized intensity using rotation measure synthesis

(1.8-9.9)\times10^{10}~M_\odot

The Australia Telescope Large Area Survey: 2.3 GHz observations of ELAIS-S1 and CDF-S Spectral index properties of the faint radio sky

. This is the first study of the HI and CO in emission for a single galaxy beyond z~0.2.

Using rotation measure grids to detect cosmological magnetic fields: A Bayesian approach

We present the third data release from the Australia Telescope Large Area Survey (ATLAS). These data combine the observations at 1.4 GHz before and after upgrades to the Australia Telescope Compact Array reaching a sensitivity of 14 microJy/beam in 3.6 deg^2 over the Chandra Deep Field South (CDFS) and of 17 microJy/beam in 2.7 deg^2 over the European Large Area ISO Survey South 1 (ELAIS-S1). We used a variety of array configurations to maximise the uv coverage resulting in a resolution of 16 by 7 arcsec in CDFS and of 12 by 8 arcsec in ELAIS-S1. After correcting for peak bias and bandwidth smearing, we find a total of 3034 radio source components above 5 sigma in CDFS, of which 514 (17 per cent) are considered to be extended. The number of components detected above 5 sigma in ELAIS-S1 is 2084, of which 392 (19 per cent) are classified as extended. The catalogues include reliable spectral indices (delta alpha < 0.2) between 1.40 and 1.71 GHz for ~350 of the brightest components.

Resolving the Structure at the Heart of BAL Quasars Through Microlensing Induced Polarisation Variability

We attempt to measure the proper motions of two magnetars—the soft gamma-ray repeater SGR 1900+14 and the anomalous X-ray pulsar 1E 2259+586—using two epochs of Chandra observations separated by ~5 yr. We perform extensive tests using these data, archival data, and simulations to verify the accuracy of our measurements and understand their limitations. We find 90% upper limits on the proper motions of 54 mas yr–1 (SGR 1900+14) and 65 mas yr–1 (1E 2259+586), with the limits largely determined by the accuracy with which we could register the two epochs of data and by the inherent uncertainties on two-point proper motions. We translate the proper motions limits into limits on the transverse velocity using distances, and find v ⊥ < 1300 km s–1 (SGR 1900+14, for a distance of 5 kpc) and v ⊥ < 930 km s–1 (1E 2259+586, for a distance of 3 kpc) at 90% confidence; the range of possible distances for these objects makes a wide range of velocities possible, but it seems that the magnetars do not have uniformly high space velocities greater than 3000 km s–1. Unfortunately, our proper motions also cannot significantly constrain the previously proposed origins of these objects in nearby supernova remnants or star clusters, limited as much by our ignorance of ages as by our proper motions.