ORCID Profile
0000-0001-7821-7195
Current Organisation
University of Nottingham
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Publisher: American Astronomical Society
Date: 08-08-2019
Publisher: Oxford University Press (OUP)
Date: 16-02-2011
Publisher: Oxford University Press (OUP)
Date: 06-06-2012
Publisher: Oxford University Press (OUP)
Date: 07-10-2014
Publisher: EDP Sciences
Date: 31-10-2012
Publisher: Oxford University Press (OUP)
Date: 17-06-2017
Publisher: American Astronomical Society
Date: 27-10-2020
Abstract: Strong gravitational lenses are a rare and instructive type of astronomical object. Identification has long relied on serendipity, but different strategies—such as mixed spectroscopy of multiple galaxies along the line of sight, machine-learning algorithms, and citizen science—have been employed to identify these objects as new imaging surveys become available. We report on the comparison between spectroscopic, machine-learning, and citizen-science identification of galaxy–galaxy lens candidates from independently constructed lens catalogs in the common survey area of the equatorial fields of the Galaxy and Mass Assembly survey. In these, we have the opportunity to compare high completeness spectroscopic identifications against high-fidelity imaging from the Kilo Degree Survey used for both machine-learning and citizen-science lens searches. We find that the three methods—spectroscopy, machine learning, and citizen science—identify 47, 47, and 13 candidates, respectively, in the 180 square degrees surveyed. These identifications barely overlap, with only two identified by both citizen science and machine learning. We have traced this discrepancy to inherent differences in the selection functions of each of the three methods, either within their parent s les (i.e., citizen science focuses on low redshift) or inherent to the method (i.e., machine learning is limited by its training s le and prefers well-separated features, while spectroscopy requires sufficient flux from lensed features to lie within the fiber). These differences manifest as separate s les in estimated Einstein radius, lens stellar mass, and lens redshift. The combined s le implies a lens candidate sky density of ∼0.59 deg −2 and can inform the construction of a training set spanning a wider mass–redshift space. A combined approach and refinement of automated searches would result in a more complete s le of galaxy–galaxy lens candidates for future surveys.
Publisher: Oxford University Press (OUP)
Date: 18-11-2011
Publisher: Oxford University Press (OUP)
Date: 24-03-2011
Publisher: Oxford University Press (OUP)
Date: 05-2013
DOI: 10.1093/MNRAS/STT529
Publisher: American Astronomical Society
Date: 19-01-2010
Publisher: Oxford University Press (OUP)
Date: 27-06-2011
Publisher: Oxford University Press (OUP)
Date: 03-2011
Publisher: Oxford University Press (OUP)
Date: 25-11-2010
Publisher: Oxford University Press (OUP)
Date: 24-01-2013
DOI: 10.1093/MNRAS/STS633
Publisher: EDP Sciences
Date: 08-2022
DOI: 10.1051/0004-6361/202142935
Abstract: Aims. We present the capabilities of G alapagos -2 and G alfitm in the context of fitting two-component profiles – bulge–disk decompositions – to galaxies, with the ultimate goal of providing complete multi-band, multi-component fitting of large s les of galaxies in future surveys. We also release both the code and the fit results to 234 239 objects from the DR3 of the GAMA survey, a s le significantly deeper than in previous works. Methods. We use stringent tests on both simulated and real data, as well as comparison to public catalogues to evaluate the advantages of using multi-band over single-band data. Results. We show that multi-band fitting using G alfitm provides significant advantages when trying to decompose galaxies into their in idual constituents, as more data are being used, by effectively being able to use the colour information buried in the in idual exposures to its advantage. Using simulated data, we find that multi-band fitting significantly reduces deviations from the real parameter values, allows component sizes and Sérsic indices to be recovered more accurately, and – by design – constrains the band-to-band variations of these parameters to more physical values. On both simulated and real data, we confirm that the spectral energy distributions (SEDs) of the two main components can be recovered to fainter magnitudes compared to using single-band fitting, which tends to recover ‘disks’ and ‘bulges’ with – on average – identical SEDs when the galaxies become too faint, instead of the different SEDs they truly have. By comparing our results to those provided by other fitting codes, we confirm that they agree in general, but measurement errors can be significantly reduced by using the multi-band tools developed by the MEGAMORPH project. Conclusions. We conclude that the multi-band fitting employed by G alapagos -2 and G alfitm significantly improves the accuracy of structural galaxy parameters and enables much larger s les to be be used in a scientific analysis.
Publisher: Oxford University Press (OUP)
Date: 03-2012
Publisher: Oxford University Press (OUP)
Date: 19-05-2016
Publisher: Oxford University Press (OUP)
Date: 21-12-2012
Publisher: Oxford University Press (OUP)
Date: 29-06-2013
DOI: 10.1093/MNRAS/STT890
Publisher: Oxford University Press (OUP)
Date: 02-2010
Publisher: Oxford University Press (OUP)
Date: 29-08-2014
Publisher: Oxford University Press (OUP)
Date: 24-11-2017
Publisher: Oxford University Press (OUP)
Date: 26-07-2011
Publisher: Oxford University Press (OUP)
Date: 12-2011
Publisher: Oxford University Press (OUP)
Date: 10-01-2015
Publisher: Oxford University Press (OUP)
Date: 12-12-2011
Publisher: Oxford University Press (OUP)
Date: 03-08-2012
Publisher: Oxford University Press (OUP)
Date: 02-2012
Publisher: Oxford University Press (OUP)
Date: 04-07-2011
Publisher: Oxford University Press (OUP)
Date: 02-07-2013
Publisher: Oxford University Press (OUP)
Date: 29-10-2010
Publisher: Oxford University Press (OUP)
Date: 30-09-2015
Publisher: Oxford University Press (OUP)
Date: 29-10-2010
Publisher: EDP Sciences
Date: 07-2010
Publisher: Oxford University Press (OUP)
Date: 19-06-2015
Publisher: Oxford University Press (OUP)
Date: 12-2007
Publisher: Oxford University Press (OUP)
Date: 10-2009
Publisher: EDP Sciences
Date: 2013
Publisher: Oxford University Press (OUP)
Date: 27-01-2017
DOI: 10.1093/MNRAS/STX228
Publisher: Oxford University Press (OUP)
Date: 03-12-2015
Publisher: Oxford University Press (OUP)
Date: 06-08-2018
Publisher: Cambridge University Press (CUP)
Date: 2010
DOI: 10.1071/AS09053
Abstract: A heuristic greedy algorithm is developed for efficiently tiling spatially dense redshift surveys. In its first application to the Galaxy and MassAssembly (GAMA) redshift survey we find it rapidly improves the spatial uniformity of our data, and naturally corrects for any spatial bias introduced by the 2dF multi-object spectrograph. We make conservative predictions for the final state of the GAMA redshift survey after our final allocation of time, and can be confident that even if worse than typical weather affects our observations, all of our main survey requirements will be met.
Publisher: Oxford University Press (OUP)
Date: 08-05-2014
DOI: 10.1093/MNRAS/STU632
Publisher: Oxford University Press (OUP)
Date: 11-08-2011
Publisher: Oxford University Press (OUP)
Date: 12-2010
Publisher: Oxford University Press (OUP)
Date: 22-10-2012
Publisher: Oxford University Press (OUP)
Date: 22-01-2018
DOI: 10.1093/MNRAS/STY124
Publisher: Oxford University Press (OUP)
Date: 07-02-2013
DOI: 10.1093/MNRAS/STT030
Publisher: EDP Sciences
Date: 09-2016
Publisher: EDP Sciences
Date: 07-2010
Publisher: Oxford University Press (OUP)
Date: 02-03-2011
Publisher: Oxford University Press (OUP)
Date: 12-02-2014
Publisher: Oxford University Press (OUP)
Date: 12-2006
Publisher: Oxford University Press (OUP)
Date: 06-09-2015
Publisher: EDP Sciences
Date: 2020
DOI: 10.1051/0004-6361/201833522
Abstract: We present a multi-wavelength analysis of the galaxies in nine clusters selected from the WINGS dataset, examining how galaxy structure varies as a function of wavelength and environment using the state of the art software GALAPAGOS-2 . We simultaneously fit single-Sérsic functions on three optical ( u , B and V ) and two near-infrared ( J and K ) bands thus creating a wavelength-dependent model of each galaxy. We measure the magnitudes, effective radius ( R e ), the Sérsic index ( n ), axis ratio, and position angle in each band. The s le contains 790 cluster members (located close to the cluster centre 0.64 × R 200 ) and 254 non-member galaxies that we further separate based on their morphology into ellipticals, lenticulars, and spirals. We find that the Sérsic index of all galaxies inside clusters remains nearly constant with wavelength while R e decreases as wavelength increases for all morphological types. We do not observe a significant variation on n and R e as a function of projected local density and distance from the clusters centre. Comparing the n and R e of bright cluster galaxies with a subs le of non-member galaxies we find that bright cluster galaxies are more concentrated (display high n values) and are more compact (low R e ). Moreover, the light profile (𝒩) and size (ℛ) of bright cluster galaxies does not change as a function of wavelength in the same manner as non-member galaxies.
Publisher: Oxford University Press (OUP)
Date: 08-11-2010
Publisher: Oxford University Press (OUP)
Date: 22-05-2015
DOI: 10.1093/MNRAS/STV779
Publisher: EDP Sciences
Date: 05-2015
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Steven Bamford.