arXiv subjects

Richard J. Massey

Publications and source records attributed to Richard J. Massey.

30 records · Page 2Linked to original sources

arXiv2019

An open source toolkit for the tracking, termination and recovery of high altitude balloon flights and payloads

We present an open source toolkit of flight-proven electronic devices which can be used to track, terminate and recover high altitude balloon flights and payloads. Comprising a beacon, pyrotechnic and non-pyrotechnic cut-down devices plus associated software, the toolkit can be used to: (i) track the location of a flight via Iridium satellite communication; (ii) release lift and/or float balloons manually or at pre-defined altitudes; (iii) locate the payload after descent. The size and mass of the toolkit make it suitable for use on weather or sounding balloon flights. We describe the technology readiness level of the toolkit, based on over 20 successful flights to altitudes of typically 32,000 m.

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arXiv2018

Overview, design, and flight results from SuperBIT: a high-resolution, wide-field, visible-to-near-UV balloon-borne astronomical telescope

Balloon-borne astronomy is a unique tool that allows for a level of image stability and significantly reduced atmospheric interference without the often prohibitive cost and long development time-scale that are characteristic of space-borne facility-class instruments. The Super-pressure Balloon-borne Imaging Telescope (SuperBIT) is a wide-field imager designed to provide 0.02" image stability over a 0.5 degree field-of-view for deep exposures within the visible-to-near-UV (300-900 um). As such, SuperBIT is a suitable platform for a wide range of balloon-borne observations, including solar and extrasolar planetary spectroscopy as well as resolved stellar populations and distant galaxies. We report on the overall payload design and instrumentation methodologies for SuperBIT as well as telescope and image stability results from two test flights. Prospects for the SuperBIT project are outlined with an emphasis on the development of a fully operational, three-month science flight from New Zealand in 2020.

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arXiv2018

Quantifying the abundance of faint, low-redshift satellite galaxies in the COSMOS survey

Faint dwarf satellite galaxies are important as tracers of small-scale structure, but remain poorly characterized outside the Local Group, due to the difficulty of identifying them consistently at larger distances. We review a recently proposed method for estimating the average satellite population around a given sample of nearby bright galaxies, using a combination of size and magnitude cuts (to select low-redshift dwarf galaxies preferentially) and clustering measurements (to estimate the fraction of true satellites in the cut sample). We test this method using the high-precision photometric redshift catalog of the COSMOS survey, exploring the effect of specific cuts on the clustering signal. The most effective of the size-magnitude cuts considered recover the clustering signal around low-redshift primaries (z < 0.15) with about two-thirds of the signal and 80\%\ of the signal-to-noise ratio obtainable using the full COSMOS photometric redshifts. These cuts are also fairly efficient, with more than one third of the selected objects being clustered satellites. We conclude that structural selection represents a useful tool in characterizing dwarf populations to fainter magnitudes and/or over larger areas than are feasible with spectroscopic surveys.} In reviewing the low-redshift content of the COSMOS field, we also note the existence of several dozen objects that appear resolved or partially resolved in the HST imaging, and are confirmed to be local (at distances of $\sim$250 Mpc or less) by their photometric or spectroscopic redshifts. This underlines the potential for future space-based surveys to reveal local populations of intrinsically faint galaxies through imaging alone.

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arXiv2018

Image Reconstruction Techniques in Neutron and Gamma-Ray Spectroscopy: Improving Lunar Prospector Data

We present improved resolution maps of the Lunar Prospector Neutron Spectrometer thermal, epithermal and fast neutron data and Gamma-Ray Spectrometer Th-line fluxes via global application of pixon image reconstruction techniques. With the use of mock data sets, we show that the pixon image reconstruction method compares favorably with other methods that have been used in planetary neutron and gamma-ray spectroscopy. The improved thermal neutron maps are able to clearly distinguish variations in composition across the lunar surface, including within the lunar basins of Hertzsprung and Schrodinger. The improvement in resolution reveals a correlation between albedo and thermal neutron flux within the craters. The consequent increase in dynamic range confirms that Hertzsprung basin contains one of the most anorthositic parts of the lunar crust, including nearly pure anorthite over a region tens of km in diameter. At Orientale, the improvement in spatial resolution of the epithermal neutron data show that there is a mismatch between measures of regolith maturity that sample the surface and those that probe the near-subsurface, which suggests a complex layering scenario.

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arXiv2017

Evidence for a Localised Source of the Argon in the Lunar Exosphere

We perform the first tests of various proposed explanations for observed features of the Moon's argon exosphere, including models of: spatially varying surface interactions; a source that reflects the lunar near-surface potassium distribution; and temporally varying cold trap areas. Measurements from the Lunar Atmosphere and Dust Environment Explorer (LADEE) and the Lunar Atmosphere Composition Experiment (LACE) are used to test whether these models can reproduce the data. The spatially varying surface interactions hypothesized in previous work cannot reproduce the persistent argon enhancement observed over the western maria. They also fail to match the observed local time of the near-sunrise peak in argon density, which is the same for the highland and mare regions, and is well reproduced by simple surface interactions with a ubiquitous desorption energy of 28 kJ/mol. A localised source can explain the observations, with a trade-off between an unexpectedly localised source or an unexpectedly brief lifetime of argon atoms in the exosphere. To match the observations, a point-like source requires source and loss rates of ~$1.9\times10^{21}$ atoms/s. A more diffuse source, weighted by the near-surface potassium, requires much higher rates of ~$1.1\times10^{22}$ atoms/s, corresponding to a mean lifetime of just 1.4 lunar days. We do not address the mechanism for producing a localised source, but demonstrate that this appears to be the only model that can reproduce the observations. Large, seasonally varying cold traps could explain the long-term fluctuation in the global argon density observed by LADEE, but not that by LACE.

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arXiv2017

Equatorial locations of water on Mars: Improved resolution maps based on Mars Odyssey Neutron Spectrometer data

We present a map of the near subsurface hydrogen distribution on Mars, based on epithermal neutron data from the Mars Odyssey Neutron Spectrometer. The map's spatial resolution is approximately improved two-fold via a new form of the pixon image reconstruction technique. We discover hydrogen-rich mineralogy far from the poles, including ~10 wt. % water equivalent hydrogen (WEH) on the flanks of the Tharsis Montes and greater than 40 wt. % WEH at the Medusae Fossae Formation (MFF). The high WEH abundance at the MFF implies the presence of bulk water ice. This supports the hypothesis of recent periods of high orbital obliquity during which water ice was stable on the surface. We find the young undivided channel system material in southern Elysium Planitia to be distinct from its surroundings and exceptionally dry; there is no evidence of hydration at the location in Elysium Planitia suggested to contain a buried water ice sea. Finally, we find that the sites of recurring slope lineae (RSL) do not correlate with subsurface hydration. This implies that RSL are not fed by large, near-subsurface aquifers, but are instead the result of either small (less than 120 km diameter) aquifers, deliquescence of perchlorate and chlorate salts or dry, granular flows.

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arXiv2016

The design and development of a high-resolution visible-to-near-UV telescope for balloon-borne astronomy: SuperBIT

Balloon-borne astronomy is unique in that it allows for a level of image stability, resolution, and optical backgrounds that are comparable to space-borne systems due to greatly reduced atmospheric interference, but at a fraction of the cost and over a significantly reduced development time-scale. Instruments operating within visible-to-near-UV bands ($300$ - $900$ um) can achieve a theoretical diffraction limited resolution of $0.01"$ from the stratosphere ($35$ - $40$ km altitude) without the need for extensive adaptive optical systems required by ground-based systems. The {\it Superpressure Balloon-borne Imaging Telescope} ("SuperBIT") is a wide-field imager designed to achieve 0.02$"$ stability over a 0.5$^\circ$ field-of-view, for deep single exposures of up to 5 minutes. SuperBIT is thus well-suited for many astronomical observations, from solar or extrasolar planetary observations, to resolved stellar populations and distant galaxies (whether to study their morphology, evolution, or gravitational lensing by foreground mass). We report SuperBIT's design and implementation, emphasizing its two-stage real-time stabilization: telescope stability to $1$ - $2"$ at the telescope level (a goal surpassed during a test flight in September 2015) and image stability down to $0.02"$ via an actuated tip-tilt mirror in the optical path (to be tested during a flight in 2016). The project is progressing toward a fully operational, three month flight from New Zealand by 2018

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arXiv2014

The 400d Galaxy Cluster Survey weak lensing programme: III: Evidence for consistent WL and X-ray masses at $z\approx 0.5$

Scaling properties of galaxy cluster observables with mass provide central insights into the processes shaping clusters. Calibrating proxies for cluster mass will be crucial to cluster cosmology with upcoming surveys like eROSITA and Euclid. The recent Planck results led to suggestions that X-ray masses might be biased low by $\sim\!40$ %, more than previously considered. We extend the direct calibration of the weak lensing -- X-ray mass scaling towards lower masses (as low as $1\!\times\!10^{14}\,\mathrm{M}_{\odot}$) in a sample representative of the $z\!\sim\!0.4$--$0.5$ population. We investigate the scaling of MMT/Megacam weak lensing (WL) masses for $8$ clusters at $0.39\!\leq\!z\!\leq\!0.80$ as part of the \emph{400d} WL programme with hydrostatic \textit{Chandra} X-ray masses as well as those based on the proxies, e.g. $Y_{\mathrm{X}}\!=\!T_{\mathrm{X}}M_{\mathrm{gas}}$. Overall, we find good agreement between WL and X-ray masses, with different mass bias estimators all consistent with zero. Subdividing the sample, we find the high-mass subsample to show no significant mass bias while for the low-mass subsample, there is a bias towards overestimated X-ray masses at the $\sim\!2σ$ level for some mass proxies. The overall scatter in the mass-mass scaling relations is surprisingly low. Neither observation can be traced back to the parameter settings in the WL analysis. We do not find evidence for a strong ($\sim\!40$ %) underestimate in the X-ray masses, as suggested to reconcile Planck cluster counts and cosmological constraints. For high-mass clusters, our measurements are consistent with studies in the literature. The mass dependent bias, significant at $\sim\!2σ$, may hint at a physically different cluster population (less relaxed clusters with more substructure and mergers); or it may be due to small number statistics.

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arXiv2011

Measuring the Geometry of the Universe from Weak Gravitational Lensing behind Galaxy Groups in the HST COSMOS survey

Gravitational lensing can provide pure geometric tests of the structure of space-time, for instance by determining empirically the angular diameter distance-redshift relation. This geometric test has been demonstrated several times using massive clusters which produce a large lensing signal. In this case, matter at a single redshift dominates the lensing signal, so the analysis is straightforward. It is less clear how weaker signals from multiple sources at different redshifts can be stacked to demonstrate the geometric dependence. We introduce a simple measure of relative shear which for flat cosmologies separates the effect of lens and source positions into multiplicative terms, allowing signals from many different source-lens pairs to be combined. Applying this technique to a sample of groups and low-mass clusters in the COSMOS survey, we detect a clear variation of shear with distance behind the lens. This represents the first detection of the geometric effect using weak lensing by multiple, low-mass systems. The variation of distance with redshift is measured with sufficient precision to constrain the equation of state of the universe under the assumption of flatness, equivalent to a detection of a dark energy component Omega_X at greater than 99% confidence for an equation-of-state parameter -2.5 < w < -0.1. For the case w = -1, we find a value for the cosmological constant density parameter Omega_Lambda = 0.85+0.044-0.19 (68% C.L.), and detect cosmic acceleration (q_0 < 0) at the 98% C.L.. We consider the systematic uncertainties associated with this technique and discuss the prospects for applying it in forthcoming weak-lensing surveys.

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arXiv2011

Precision simulation of ground-based lensing data using observations from space

Current and upcoming wide-field, ground-based, broad-band imaging surveys promise to address a wide range of outstanding problems in galaxy formation and cosmology. Several such uses of ground-based data, especially weak gravitational lensing, require highly precise measurements of galaxy image statistics with careful correction for the effects of the point-spread function (PSF). In this paper, we introduce the SHERA (SHEar Reconvolution Analysis) software to simulate ground-based imaging data with realistic galaxy morphologies and observing conditions, starting from space-based data (from COSMOS, the Cosmological Evolution Survey) and accounting for the effects of the space-based PSF. This code simulates ground-based data, optionally with a weak lensing shear applied, in a model-independent way using a general Fourier space formalism. The utility of this pipeline is that it allows for a precise, realistic assessment of systematic errors due to the method of data processing, for example in extracting weak lensing galaxy shape measurements or galaxy radial profiles, given user-supplied observational conditions and real galaxy morphologies. Moreover, the simulations allow for the empirical test of error estimates and determination of parameter degeneracies, via generation of many noise maps. The public release of this software, along with a large sample of cleaned COSMOS galaxy images (corrected for charge transfer inefficiency), should enable upcoming ground-based imaging surveys to achieve their potential in the areas of precision weak lensing analysis, galaxy profile measurement, and other applications involving detailed image analysis.

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arXiv2008

Subaru Weak Lensing survey -- II: Multi-object Spectroscopy and Cluster Masses

We present the first results of a MOS campaign to follow up cluster candidates located via weak lensing. Our main goals are to search for spatial concentrations of galaxies that are plausible optical counterparts of the weak lensing signals, and to determine the cluster redshifts from those of member galaxies. Around each of 36 targeted cluster candidates, we obtain 15-32 galaxy redshifts. For 28 of these targets, we confirm a secure cluster identification. This includes three cases where two clusters at different redshifts are projected along the same line-of-sight. In 6 of the 8 unconfirmed targets, we find multiple small galaxy concentrations at different redshifts. In both the remaining two targets, a single small galaxy concentration is found. We evaluate the weak lensing mass of confirmed clusters. For a subsample of our most cleanly measured clusters, we investigate the statistical relation between their weak lensing mass and the velocity dispersion of their member galaxies, comparing our sample with optically and X-ray selected samples from the literature. Our lensing-selected clusters are consistent with sigma_v=sigma_sis, with a similar scatter to the optically and X-ray selected clusters. We thus find no evidence of selection bias compared to these other techniques. We also derive an empirical relation between the cluster mass and the galaxy velocity dispersion, which is in reasonable agreement with the prediction of N-body simulations in the LCDM cosmology.

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arXiv2007

A Subaru Weak Lensing Survey I: Cluster Candidates and Spectroscopic Verification

We present the results of an ongoing weak lensing survey conducted with the Subaru telescope whose initial goal is to locate and study the distribution of shear-selected structures or halos. Using a Suprime-cam imaging survey spanning 21.82 square degree, we present a catalog of 100 candidate halos located from lensing convergence maps. Our sample is reliably drawn from that subset of our survey area, (totaling 16.72 square degree) uncontaminated by bright stars and edge effects and limited at a convergence signal to noise ratio of 3.69. To validate the sample detailed spectroscopic measures have been made for 26 candidates using the Subaru multi-object spectrograph, FOCAS. All are confirmed as clusters of galaxies but two arise as the superposition of multiple clusters viewed along the line of sight. Including data available in the literature and an ongoing Keck spectroscopic campaign, a total of 41 halos now have reliable redshifts. For one of our survey fields, the XMM LSS (Pierre et al. 2004) field, we compare our lensing-selected halo catalog with its X-ray equivalent. Of 15 halos detected in the XMM-LSS field, 10 match with published X-ray selected clusters and a further 2 are newly-detected and spectroscopically confirmed in this work. Although three halos have not yet been confirmed, the high success rate within the XMM-LSS field (12/15) confirms that weak lensing provides a reliable method for constructing cluster catalogs, irrespective of the nature of the constituent galaxies or the intracluster medium.

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