ORCID Profile
0000-0002-4653-8637
Current Organisation
Queensland University of Technology
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Publisher: American Astronomical Society
Date: 27-01-2016
Publisher: American Astronomical Society
Date: 09-01-2017
Publisher: American Astronomical Society
Date: 05-02-2020
Publisher: Cambridge University Press (CUP)
Date: 2023
DOI: 10.1017/PASA.2023.29
Abstract: We present a comparison between the performance of a selection of source finders (SFs) using a new software tool called Hydra. The companion paper, Paper I, introduced the Hydra tool and demonstrated its performance using simulated data. Here we apply Hydra to assess the performance of different source finders by analysing real observational data taken from the Evolutionary Map of the Universe (EMU) Pilot Survey. EMU is a wide-field radio continuum survey whose primary goal is to make a deep ( $20\\mu$ Jy/beam RMS noise), intermediate angular resolution ( $15^{\\prime\\prime}$ ), 1 GHz survey of the entire sky south of $+30^{\\circ}$ declination, and expecting to detect and catalogue up to 40 million sources. With the main EMU survey it is highly desirable to understand the performance of radio image SF software and to identify an approach that optimises source detection capabilities. Hydra has been developed to refine this process, as well as to deliver a range of metrics and source finding data products from multiple SFs. We present the performance of the five SFs tested here in terms of their completeness and reliability statistics, their flux density and source size measurements, and an exploration of case studies to highlight finder-specific limitations.
Publisher: American Astronomical Society
Date: 03-06-2015
Publisher: American Astronomical Society
Date: 23-07-2015
Publisher: Oxford University Press (OUP)
Date: 28-07-2022
Abstract: Following the discovery of SAGE0536AGN (z ∼ 0.14), with the strongest 10-μm silicate emission ever observed for an active galactic nucleus (AGN), we discovered SAGE0534AGN (z ∼ 1.01), a similar AGN but with less extreme silicate emission. Both were originally mistaken as evolved stars in the Magellanic Clouds. Lack of far-infrared emission, and therefore star formation, implies we are seeing the central engine of the AGN without contribution from the host galaxy. They could be a key link in galaxy evolution. We used a dimensionality reduction algorithm, t-distributed stochastic neighbour embedding with multiwavelength data from Gaia EDR3, VISTA survey of the Magellanic Clouds, AllWISE, and the Australian Square Kilometre Array Pathfinder to find these two unusual AGNs are grouped with 16 other objects separated from the rest, suggesting a rare class. Our spectroscopy at South African Astronomical Observatory/Southern African Large Telescope and literature data confirm at least 14 of these objects are extragalactic (0.13 & z & 1.23), all hosting AGN. Using spectral energy distribution fitter C igale we find that the majority of dust emission ($\\gt 70 {{\\ \\rm per\\ cent}}$) in these sources is due to the AGN. Host galaxies appear to be either in or transitioning into the green valley. There is a trend of a thinning torus, increasing X-ray luminosity, and decreasing Eddington ratio as the AGN transition through the green valley, implying that as the accretion supply depletes, the torus depletes and the column density reduces. Also, the near-infrared variability litude of these sources correlates with attenuation by the torus, implying the torus plays a role in the variability.
Publisher: Cambridge University Press (CUP)
Date: 2017
DOI: 10.1017/PASA.2017.41
Abstract: The Taipan galaxy survey (hereafter simply ‘Taipan’) is a multi-object spectroscopic survey starting in 2017 that will cover 2π steradians over the southern sky (δ ≲ 10°, | b | ≳ 10°), and obtain optical spectra for about two million galaxies out to z 0.4. Taipan will use the newly refurbished 1.2-m UK Schmidt Telescope at Siding Spring Observatory with the new TAIPAN instrument, which includes an innovative ‘Starbugs’ positioning system capable of rapidly and simultaneously deploying up to 150 spectroscopic fibres (and up to 300 with a proposed upgrade) over the 6° diameter focal plane, and a purpose-built spectrograph operating in the range from 370 to 870 nm with resolving power R ≳ 2000. The main scientific goals of Taipan are (i) to measure the distance scale of the Universe (primarily governed by the local expansion rate, H 0 ) to 1% precision, and the growth rate of structure to 5% (ii) to make the most extensive map yet constructed of the total mass distribution and motions in the local Universe, using peculiar velocities based on improved Fundamental Plane distances, which will enable sensitive tests of gravitational physics and (iii) to deliver a legacy s le of low-redshift galaxies as a unique laboratory for studying galaxy evolution as a function of dark matter halo and stellar mass and environment. The final survey, which will be completed within 5 yrs, will consist of a complete magnitude-limited s le ( i ⩽ 17) of about 1.2 × 10 6 galaxies supplemented by an extension to higher redshifts and fainter magnitudes ( i ⩽ 18.1) of a luminous red galaxy s le of about 0.8 × 10 6 galaxies. Observations and data processing will be carried out remotely and in a fully automated way, using a purpose-built automated ‘virtual observer’ software and an automated data reduction pipeline. The Taipan survey is deliberately designed to maximise its legacy value by complementing and enhancing current and planned surveys of the southern sky at wavelengths from the optical to the radio it will become the primary redshift and optical spectroscopic reference catalogue for the local extragalactic Universe in the southern sky for the coming decade.
Publisher: American Astronomical Society
Date: 19-01-2016
Publisher: IOP Publishing
Date: 16-01-2017
Publisher: American Astronomical Society
Date: 21-07-2020
Publisher: Oxford University Press (OUP)
Date: 25-11-0088
Publisher: American Astronomical Society
Date: 24-08-2016
Publisher: American Astronomical Society
Date: 05-01-2017
Publisher: American Astronomical Society
Date: 02-04-2015
Publisher: American Astronomical Society
Date: 24-03-2017
Publisher: IOP Publishing
Date: 05-2014
Publisher: Oxford University Press (OUP)
Date: 14-03-2017
DOI: 10.1093/MNRAS/STX605
Publisher: American Astronomical Society
Date: 27-07-2016
Publisher: American Astronomical Society
Date: 17-08-2018
Publisher: American Astronomical Society
Date: 09-04-2020
Publisher: Zenodo
Date: 2016
DOI: 10.5281/ZENODO.60610
Publisher: Oxford University Press (OUP)
Date: 09-10-2018
Publisher: Zenodo
Date: 2019
Publisher: American Astronomical Society
Date: 10-10-2016
Publisher: Oxford University Press (OUP)
Date: 22-01-2016
Publisher: American Astronomical Society
Date: 22-06-2016
Publisher: IOP Publishing
Date: 16-01-2017
Publisher: American Astronomical Society
Date: 03-05-2018
Publisher: American Astronomical Society
Date: 03-03-2016
Publisher: American Astronomical Society
Date: 18-07-2016
Publisher: IOP Publishing
Date: 10-11-2016
Publisher: Cambridge University Press (CUP)
Date: 2023
DOI: 10.1017/PASA.2023.24
Abstract: The latest generation of radio surveys are now producing sky survey images containing many millions of radio sources. In this context it is highly desirable to understand the performance of radio image source finder (SF) software and to identify an approach that optimises source detection capabilities. We have created Hydra to be an extensible multi-SF and cataloguing tool that can be used to compare and evaluate different SFs. Hydra, which currently includes the SFs Aegean, Caesar, ProFound, PyBDSF, and Selavy, provides for the addition of new SFs through containerisation and configuration files. The SF input RMS noise and island parameters are optimised to a 90% ‘percentage real detections’ threshold (calculated from the difference between detections in the real and inverted images), to enable comparison between SFs. Hydra provides completeness and reliability diagnostics through observed-deep ( $\\mathcal{D}$ ) and generated-shallow ( $\\mathcal{S}$ ) images, as well as other statistics. In addition, it has a visual inspection tool for comparing residual images through various selection filters, such as S/N bins in completeness or reliability. The tool allows the user to easily compare and evaluate different SFs in order to choose their desired SF, or a combination thereof. This paper is part one of a two part series. In this paper we introduce the Hydra software suite and validate its $\\mathcal{D/S}$ metrics using simulated data. The companion paper demonstrates the utility of Hydra by comparing the performance of SFs using both simulated and real images.
Publisher: American Astronomical Society
Date: 21-07-2016
Publisher: American Astronomical Society
Date: 11-02-2016
Publisher: Cambridge University Press (CUP)
Date: 2023
DOI: 10.1017/PASA.2023.42
Abstract: To explore the role environment plays in influencing galaxy evolution at high redshifts, we study $$2.0 \\le z \\lt 4.2$$ environments using the FourStar Galaxy Evolution (ZFOURGE) survey. Using galaxies from the COSMOS legacy field with $${\\rm{log}}\\left( {{{\\rm{M}}_{\\rm{*}}}/{{\\rm{M}}_ \\odot }} \\right) \\geqslant 9.5$$ , we use a seventh nearest neighbour density estimator to quantify galaxy environment, iding this into bins of low, intermediate and high density. We discover new high density environment candidates across $$2.0 \\le z \\lt 2.4$$ and $$3.1 \\le z \\lt 4.2$$ . We analyse the quiescent fraction, stellar mass and specific star formation rate (sSFR) of our galaxies to understand how these vary with redshift and environment. Our results reveal that, across $$2.0 \\le z \\lt 2.4$$ , the high density environments are the most significant regions, which consist of elevated quiescent fractions, $${\\rm{log}}\\left( {{{\\rm{M}}_{\\rm{*}}}/{{\\rm{M}}_ \\odot }} \\right) \\geqslant 10.2{\\rm{\\ massive}}$$ galaxies and suppressed star formation activity. At $$3.1 \\le z \\lt 4.2$$ , we find that high density regions consist of elevated stellar masses but require more complete s les of quiescent and sSFR data to study the effects of environment in more detail at these higher redshifts. Overall, our results suggest that well-evolved, passive galaxies are already in place in high density environments at $$z \\sim 2.4$$ , and that the Butcher-Oemler effect and SFR-density relation may not reverse towards higher redshifts as previously thought.
Publisher: IOP Publishing
Date: 10-09-2015
Publisher: American Astronomical Society
Date: 21-08-2014
Publisher: American Astronomical Society
Date: 13-04-2017
Location: Australia
No related grants have been discovered for Michael Cowley.