Publications by Peter Hatfield

Using sparse Gaussian processes for predicting robust inertial confinement fusion implosion yields

IEEE Transactions on Plasma Science IEEE (2019) 1-6

P Hatfield, S Rose, R Scott, I Almosallam, S Roberts, M Jarvis

X-ray-line coincidence photopumping in a potassium-chlorine mixed plasma

Physical Review A American Physical Society (APS) 101 (2020) 053431

LMR Hobbs, D Burridge, MP Hill, DJ Hoarty, CRD Brown, R Charles, G Cooper, SF James, LA Wilson, W Babbage, PW Hatfield, P Beiersdorfer, J Nilsen, H Scott, SJ Rose

Modelling burning thermonuclear plasma rose

Philosophical Transactions A: Mathematical, Physical and Engineering Sciences Royal Society (0)

SJ Rose, P Hatfield, RHH Scott

Augmenting machine learning photometric redshifts with Gaussian mixture models

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2020)

P Hatfield, I Almosallam, M Jarvis, N Adams, R Bowler, Z Gomes, S Roberts, C Schreiber

&lt;jats:title&gt;Abstract&lt;/jats:title&gt; &lt;jats:p&gt;Wide-area imaging surveys are one of the key ways of advancing our understanding of cosmology, galaxy formation physics, and the large-scale structure of the Universe in the coming years. These surveys typically require calculating redshifts for huge numbers (hundreds of millions to billions) of galaxies - almost all of which must be derived from photometry rather than spectroscopy. In this paper we investigate how using statistical models to understand the populations that make up the colour-magnitude distribution of galaxies can be combined with machine learning photometric redshift codes to improve redshift estimates. In particular we combine the use of Gaussian Mixture Models with the high performing machine learning photo-z algorithm GPz and show that modelling and accounting for the different colour-magnitude distributions of training and test data separately can give improved redshift estimates, reduce the bias on estimates by up to a half, and speed up the run-time of the algorithm. These methods are illustrated using data from deep optical and near infrared data in two separate deep fields, where training and test data of different colour-magnitude distributions are constructed from the galaxies with known spectroscopic redshifts, derived from several heterogeneous surveys.&lt;/jats:p&gt;

Observation of He-like satellite lines of the H-like potassium K XIX emission

Astrophysical Journal American Astronomical Society 881 (2019) 92

ME Weller, P Beiersdorfer, TE Lockard, GV Brown, A McKelvey, J Nilsen, R Shepherd, VA Soukhanovskii, MP Hill, LMR Hobbs, D Burridge, DJ Hoarty, J Morton, L Wilson, S Rose, P Hatfield

We present measurements of the H-like potassium (K xix) X-ray spectrum and its He-like (K xviii) satellite lines, which are situated in the wavelength region between 3.34 and 3.39 Å, which has been of interest for the detection of dark matter. The measurements were taken with a high-resolution X-ray spectrometer from targets irradiated by a long-pulse (2 ns) beam from the Orion laser facility. We obtain experimental wavelength values of dielectronic recombination satellite lines and show that the ratio of the Lyα lines and their dielectronic satellite lines can be used to estimate the electron temperature, which in our case was about 1.5 ± 0.3 keV.

Comparing Galaxy Clustering in Horizon-AGN Simulated Lightcone Mocks and VIDEO Observations

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P Hatfield, C Laigle, M Jarvis, JULIEN Devriendt, I Davidzon, O Ilbert, C Pichon, Y Dubois

Hydrodynamical cosmological simulations have recently made great advances in reproducing galaxy mass assembly over cosmic time - as often quantified from the comparison of their predicted stellar mass functions to observed stellar mass functions from data. In this paper we compare the clustering of galaxies from the hydrodynamical cosmological simulated lightcone Horizon-AGN, to clustering measurements from the VIDEO survey observations. Using mocks built from a VIDEO-like photometry, we first explore the bias introduced into clustering measurements by using stellar masses and redshifts derived from SED-fitting, rather than the intrinsic values. The propagation of redshift and mass statistical and systematic uncertainties in the clustering measurements causes us to underestimate the clustering amplitude. We find then that clustering and halo occupation distribution (HOD) modelling results are qualitatively similar in Horizon-AGN and VIDEO. However at low stellar masses Horizon-AGN underestimates the observed clustering by up to a factor of ~3, reflecting the known excess stellar mass to halo mass ratio for Horizon-AGN low mass haloes, already discussed in previous works. This reinforces the need for stronger regulation of star formation in low mass haloes in the simulation. Finally, the comparison of the stellar mass to halo mass ratio in the simulated catalogue, inferred from angular clustering, to that directly measured from the simulation, validates HOD modelling of clustering as a probe of the galaxy-halo connection.

Enhanced fluorescence from x-ray line coincidence pumping of K-pumped Cl and Mg-pumped Ge plasmas

Proceedings of SPIE Society of Photo-optical Instrumentation Engineers 11111 (2019)

J Nilsen, D Burridge, LMR Hobbs, D Hoarty, P Beiersdorfer, GV Brown, N Hell, D Panchenko, MF Gu, AM Saunders, HA Scott, RA London, P Hatfield, MP Hill, L Wilson, R Charles, CRD Brown, S Rose

Transforming education with the Timepix detector - Ten years of CERN@school

Radiation Measurements Elsevier BV (2019) 106090

B Parker, L Thomas, E Rushton, P Hatfield

The blind implosion-maker: Automated inertial confinement fusion experiment design

Physics of Plasmas AIP Publishing 26 (2019) 062706

PW Hatfield, S Rose, R Scott

The design of inertial confinement fusion (ICF) experiments, alongside improving the development of energy density physics theory and experimental methods, is one of the key challenges in the quest for nuclear fusion as a viable energy source [O. A. Hurricane, J. Phys.: Conf. Ser. 717, 012005 (2016)]. Recent challenges in achieving a high-yield implosion at the National Ignition Facility (NIF) have led to new interest in considering a much wider design parameter space than normally studied [J. L. Peterson et al., Phys. Plasmas 24, 032702 (2017)]. Here, we report an algorithmic approach that can produce reasonable ICF designs with minimal assumptions. In particular, we use the genetic algorithm metaheuristic, in which “populations” of implosions are simulated, the design of the capsule is described by a “genome,” natural selection removes poor designs, high quality designs are “mated” with each other based on their yield, and designs undergo “mutations” to introduce new ideas. We show that it takes ∼5 × 104 simulations for the algorithm to find an original NIF design. We also link this method to other parts of the design process and look toward a completely automated ICF experiment design process—changing ICF from an experiment design problem to an algorithm design problem.

First results from the LUCID-Timepix spacecraft payload onboard the TechDemoSat-1 satellite in low Earth orbit

Advances in Space Research Elsevier 63 (2018) 1523-1540

W Furnell, A Shenoy, E Fox, P Hatfield

The Langton Ultimate Cosmic ray Intensity Detector (LUCID) is a payload onboard the satellite TechDemoSat-1, used to study the radiation environment in Low Earth Orbit (635 km). LUCID operated from 2014 to 2017, collecting over 2.1 million frames of radiation data from its five Timepix detectors on board. LUCID is one of the first uses of the Timepix detector technology in open space, with the data providing useful insight into the performance of this technology in new environments. It provides high-sensitivity imaging measurements of the mixed radiation field, with a wide dynamic range in terms of spectral response, particle type and direction. The data has been analysed using computing resources provided by GridPP, with a new machine learning algorithm that uses the Tensorflow framework. This algorithm provides a new approach to processing Medipix data, using a training set of human labelled tracks, providing greater particle classification accuracy than other algorithms. For managing the LUCID data, we have developed an online platform called Timepix Analysis Platform at School (TAPAS). This provides a swift and simple way for users to analyse data that they collect using Timepix detectors from both LUCID and other experiments. We also present some possible future uses of the LUCID data and Medipix detectors in space.

The LUCID-Timepix spacecraft payload and the CERN@school educational programme

JOURNAL OF INSTRUMENTATION 13 (2018)

P Hatfield, W Furnell, A Shenoy, E Fox, R Parker, L Thomas

The environment and host haloes of the brightest z~6 Lyman-break galaxies

MNRAS (0)

PW Hatfield, RAA Bowler, MJ Jarvis, CL Hale

By studying the large-scale structure of the bright high-redshift Lyman-break galaxy (LBG) population it is possible to gain an insight into the role of environment in galaxy formation physics in the early Universe. We measure the clustering of a sample of bright ($-22.7<M_{UV}<-21.125$) LBGs at $z\sim6$ and use a halo occupation distribution (HOD) model to measure their typical halo masses. We find that the clustering amplitude and corresponding HOD fits suggests that these sources are highly biased ($b\sim10$) objects in the densest regions of the high-redshift Universe. Coupled with the observed rapid evolution of the number density of these objects, our results suggest that the shape of high luminosity end of the luminosity function is related to feedback processes or the onset of dust obscuration - as opposed to a scenario where these sources are predominantly rare instances of the much more numerous $M_{UV} \sim -19$ population of galaxies caught in a particularly vigorous period of star formation. Despite investigating several variations on the model, we struggle to simultaneously fit both the number densities and clustering measurements. We interpret this as a signal that a refinement of the model halo bias relation at high redshifts or the incorporation of quasi-linear effects may be needed for future attempts at modelling the clustering and number counts. Finally, the difference in number density between the fields (UltraVISTA has a surface density$\sim 1.8$ times greater than UDS) is shown to be consistent with the cosmic variance implied by the clustering measurements.

The clustering and bias of radio-selected AGN and star-forming galaxies in the COSMOS field

Monthly Notices of the Royal Astronomical Society Oxford University Press 474 (2017) 4133-4150

CL Hale, MJ Jarvis, I Delvecchio, PW Hatfield, M Novak, V Smolcic, G Zamorani

Dark matter haloes in which galaxies reside are likely to have a significant impact on their evolution. We investigate the link between dark matter haloes and their constituent galaxies by measuring the angular two-point correlation function of radio sources, using recently released 3 GHz imaging over $\sim 2 \ \mathrm{deg}^2$ of the COSMOS field. We split the radio source population into Star Forming Galaxies (SFGs) and Active Galactic Nuclei (AGN), and further separate the AGN into radiatively efficient and inefficient accreters. Restricting our analysis to $z&lt;1$, we find SFGs have a bias, $b = 1.5 ^{+0.1}_{-0.2}$, at a median redshift of $z=0.62$. On the other hand, AGN are significantly more strongly clustered with $b = 2.1\pm 0.2$ at a median redshift of 0.7. This supports the idea that AGN are hosted by more massive haloes than SFGs. We also find low-accretion rate AGN are more clustered ($b = 2.9 \pm 0.3$) than high-accretion rate AGN ($b = 1.8^{+0.4}_{-0.5}$) at the same redshift ($z \sim 0.7$), suggesting that low-accretion rate AGN reside in higher mass haloes. This supports previous evidence that the relatively hot gas that inhabits the most massive haloes is unable to be easily accreted by the central AGN, causing them to be inefficient. We also find evidence that low-accretion rate AGN appear to reside in halo masses of $M_{h} \sim 3-4 \times 10^{13}h^{-1}$M$_{\odot}$ at all redshifts. On the other hand, the efficient accreters reside in haloes of $M_{h} \sim 1-2 \times 10^{13}h^{-1}$M$_{\odot}$ at low redshift but can reside in relatively lower mass haloes at higher redshifts. This could be due to the increased prevalence of cold gas in lower mass haloes at $z \ge 1$ compared to $z&lt;1$.

Extragalactic optical and near-infrared foregrounds to 21-cm epoch of reionisation experiments

Proceedings of the International Astronomical Union Cambridge University Press 12 (2018) 183-190

MJ Jarvis, RAA Bowler, PW Hatfield

Foreground contamination is one of the most important limiting factors in detecting the neutral hydrogen in the epoch of reionisation. These foregrounds can be roughly split into galactic and extragalactic foregrounds. In these proceedings we highlight information that can be gleaned from multi-wavelength extragalactic surveys in order to overcome this issue. We discuss how clustering information from the lower-redshift, foreground galaxies, can be used as additional information in accounting for the noise associated with the foregrounds. We then go on to highlight the expected contribution of future optical and near-infrared surveys for detecting the galaxies responsible for ionising the Universe. We suggest that these galaxies can also be used to reduce the systematics in the 21-cm epoch of reionisation signal through cross-correlations if enough common area is surveyed.

Environmental quenching and galactic conformity in the galaxy cross-correlation signal

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 472 (2017) 3570-3588

PW Hatfield, MJ Jarvis

The MeerKAT international GHz tiered extragalactic exploration (MIGHTEE) survey

Proceedings of Science (2016)

MJ Jarvis, AR Taylor, I Agudo, JR Allison, RP Deane, B Frank, N Gupta, I Heywood, N Maddox, K McAlpine, MG Santos, AMM Scaife, M Vaccari, JTL Zwart, E Adams, DJ Bacon, AJ Baker, BA Bassett, PN Best, R Beswick, S Blyth, ML Brown, M Brüggen, M Cluver, S Colafranceso, G Cotter, C Cress, R Davé, C Ferrari, MJ Hardcastle, C Hale, I Harrison, PW Hatfield, HR Klöckner, S Kolwa, E Malefahlo, T Marubini, T Mauch, K Moodley, R Morganti, R Norris, JA Peters, I Prandoni, M Prescott, S Oliver, N Oozeer, HJA Röttgering, N Seymour, C Simpson, O Smirnov, DJB Smith, K Spekkens, J Stil, C Tasse, K van der Heyden, IH Whittam, WL WIlliams

© Copyright owned by the author(s). The MIGHTEE large survey project will survey four of the most well-studied extragalactic deep fields, totalling 20 square degrees to µJy sensitivity at Giga-Hertz frequencies, as well as an ultra-deep image of a single ∼1 deg2 MeerKAT pointing. The observations will provide radio continuum, spectral line and polarisation information. As such, MIGHTEE, along with the excellent multi-wavelength data already available in these deep fields, will allow a range of science to be achieved. Specifically, MIGHTEE is designed to significantly enhance our understanding of, (i) the evolution of AGN and star-formation activity over cosmic time, as a function of stellar mass and environment, free of dust obscuration; (ii) the evolution of neutral hydrogen in the Universe and how this neutral gas eventually turns into stars after moving through the molecular phase, and how efficiently this can fuel AGN activity; (iii) the properties of cosmic magnetic fields and how they evolve in clusters, filaments and galaxies. MIGHTEE will reach similar depth to the planned SKA all-sky survey, and thus will provide a pilot to the cosmology experiments that will be carried out by the SKA over a much larger survey volume.

The galaxy-halo connection in the VIDEO survey at 0.5 < z < 1.7

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 459 (2016) 2618-2631

PW Hatfield, SN Lindsay, MJ Jarvis, B Haussler, M Vaccari, A Verma

The MeerKAT International GHz tiered Extragalactic Exploration (MIGHTEE) survey

Proceedings of Science Proceedings of Science (2016)

M Jarvis, AR Taylor, I Agudo, RP Deane, B Frank, N Gupta, I Heywood, N Maddox, K McAlpine, AMM Scaife, M Vaccari, JTL Zwart, E Adams, DJ Bacon, AJ Baker, BA Bassett, PN Best, R Beswick, S Blyth, ML Brown, C Hale, I Harrison, PW Hatfield

The MIGHTEE large survey project will survey four of the most well-studied extragalactic deep fields, totalling 20 square degrees to $\mu$Jy sensitivity at Giga-Hertz frequencies, as well as an ultra-deep image of a single ~1 square degree MeerKAT pointing. The observations will provide radio continuum, spectral line and polarisation information. As such, MIGHTEE, along with the excellent multi-wavelength data already available in these deep fields, will allow a range of science to be achieved. Specifically, MIGHTEE is designed to significantly enhance our understanding of, (i) the evolution of AGN and star-formation activity over cosmic time, as a function of stellar mass and environment, free of dust obscuration; (ii) the evolution of neutral hydrogen in the Universe and how this neutral gas eventually turns into stars after moving through the molecular phase, and how efficiently this can fuel AGN activity; (iii) the properties of cosmic magnetic fields and how they evolve in clusters, filaments and galaxies. MIGHTEE will reach similar depth to the planned SKA all-sky survey, and thus will provide a pilot to the cosmology experiments that will be carried out by the SKA over a much larger survey volume.

The rich are different: evidence from the RAVE survey for stellar radial migration

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 447 (2015) 3526-3535

G Kordopatis, J Binney, G Gilmore, RFG Wyse, V Belolcurov, PJ McMillan, P Hatfield, EK Grebel, M Steinmetz, JF Navarro, G Seabroke, I Minchev, C Chiappini, O Bienayme, J Bland-Hawthorn, KC Freeman, BK Gibson, A Helmi, U Munari, Q Parker, WA Reid, A Siebert, A Siviero, T Zwitter