arXiv subjects

W. Sutherland

Publications and source records attributed to W. Sutherland.

At least 19 recordsLinked to original sources

arXiv2026

Progress of the design of the 12-m optical, Wide-field Spectroscopic Telescope (WST)

The Wide-Field Spectroscopic Telescope (WST) is a 12-m class, Alt-Az optical telescope providing two simultaneous foci, 2 degrees and 3 by 3 arc minutes respectively, for Multi-Object Spectroscopy (MOS) and Integral Field Spectroscopy (IFS) at visible wavelengths. Within the framework of the Horizon Programme, the project has been approved for phase A funding by the EC in 2024 and is currently undergoing intensive development. The optical design relies on a corrected Cassegrain solution feeding multi-object spectrographs through fibres, while the central area of the field is propagated to a gravity-stable Integral Field Station housing an array of spectrographs. We report progress of the design, of the functional and physical definitions of key subsystems, and of the design of high-performance coatings of the telescope optics. The telescope would be located near ESO Paranal - Armazones observatory and protected by a VLT-like enclosure. With a view to minimising risks, from capital investment to operations, designs build extensively on VLT and ELT solutions. Owing to the optical configuration, the telescope can be wavefront-controlled at both foci, with little if any crosstalk between MOS and IFS controls. The optical path is constrained to provide natural guide star, ground-layer adaptive correction at the IFS field, within existing technology. Finally, from its earliest stage of development the system is being scrutinized for its properties in relation to sustainability.

astro-ph.IM↗

arXiv2024

MeerKAT Observations of Herschel Protocluster Candidates

High-redshift protoclusters consisting of dusty starbursts are thought to play an important role in galaxy evolution. Their dusty nature makes them bright in the FIR/submm but difficult to find in optical/NIR surveys. Radio observations are an excellent way to study these dusty starbursts, as dust is transparent in the radio and there is a tight correlation between the FIR and radio emission of a galaxy. Here, we present MeerKAT 1.28 GHz radio imaging of 3 Herschel candidate protoclusters, with a synthesised beam size of ~$7.5'' \times 6.6''$ and a central thermal noise down to $4.35~\mu$Jy/beam. Our source counts are consistent with other radio counts with no evidence of overdensities. Around 95% of the Herschel sources have 1.28 GHz IDs. Using the Herschel 250 micron primary beam size as the searching radius, we find 54.2% Herschel sources have multiple 1.28 GHz IDs. Our average FIR-radio correlation coefficient $q_{250\mu m}$ is $2.33\pm 0.26$. Adding $q_{250\mu m}$ as a new constraint, the probability of finding chance-aligned sources is reduced by a factor of ~6, but with the risk of discarding true identifications of radio-loud/quiet sources. With accurate MeerKAT positions, we cross-match our Herschel sources to optical/NIR data followed by photometric redshift estimations. By removing $z<1$ sources, the density contrasts of two of the candidate protoclusters increase, suggestive of them being real protoclusters at $z>1$. There is also potentially a $0.9<z<1.2$ overdensity associated with one candidate protocluster. In summary, photometric redshifts from radio-optical cross-identifications have provided some tentative evidence of overdensities aligning with two of the candidate protoclusters.

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arXiv2019

The fourth data release of the Kilo-Degree Survey: ugri imaging and nine-band optical-IR photometry over 1000 square degrees

The Kilo-Degree Survey (KiDS) is an ongoing optical wide-field imaging survey with the OmegaCAM camera at the VLT Survey Telescope, specifically designed for measuring weak gravitational lensing by galaxies and large-scale structure. When completed it will consist of 1350 square degrees imaged in four filters (ugri). Here we present the fourth public data release which more than doubles the area of sky covered by data release 3. We also include aperture-matched ZYJHKs photometry from our partner VIKING survey on the VISTA telescope in the photometry catalogue. We illustrate the data quality and describe the catalogue content. Two dedicated pipelines are used for the production of the optical data. The Astro-WISE information system is used for the production of co-added images in the four survey bands, while a separate reduction of the r-band images using the theli pipeline is used to provide a source catalogue suitable for the core weak lensing science case. All data have been re-reduced for this data release using the latest versions of the pipelines. The VIKING photometry is obtained as forced photometry on the theli sources, using a re-reduction of the VIKING data that starts from the VISTA pawprints. Modifications to the pipelines with respect to earlier releases are described in detail. The photometry is calibrated to the Gaia DR2 G band using stellar locus regression. In this data release a total of 1006 square-degree survey tiles with stacked ugri images are made available, accompanied by weight maps, masks, and single-band source lists. We also provide a multi-band catalogue based on r-band detections, including homogenized photometry and photometric redshifts, for the whole dataset. Mean limiting magnitudes (5 sigma in a 2" aperture) are 24.23, 25.12, 25.02, 23.68 in ugri, respectively, and the mean r-band seeing is 0.70".

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arXiv2017

Galaxy And Mass Assembly (GAMA): The Consistency of GAMA and WISE Derived Mass-to-Light Ratios

Recent work has suggested that mid-IR wavelengths are optimal for estimating the mass-to-light ratios of stellar populations and hence the stellar masses of galaxies. We compare stellar masses deduced from spectral energy distribution (SED) models, fitted to multi-wavelength optical-NIR photometry, to luminosities derived from {\it WISE} photometry in the $W1$ and $W2$ bands at 3.6 and 4.5$\mu$m for non-star forming galaxies. The SED derived masses for a carefully selected sample of low redshift ($z \le 0.15$) passive galaxies agree with the prediction from stellar population synthesis models that $M_*/L_{W1} \simeq 0.6$ for all such galaxies, independent of other stellar population parameters. The small scatter between masses predicted from the optical SED and from the {\it WISE} measurements implies that random errors (as opposed to systematic ones such as the use of different IMFs) are smaller than previous, deliberately conservative, estimates for the SED fits. This test is subtly different from simultaneously fitting at a wide range of optical and mid-IR wavelengths, which may just generate a compromise fit: we are directly checking that the best fit model to the optical data generates an SED whose $M_*/L_{W1}$ is also consistent with separate mid-IR data. We confirm that for passive low redshift galaxies a fixed $M_*/L_{W1} = 0.65$ can generate masses at least as accurate as those obtained from more complex methods. Going beyond the mean value, in agreement with expectations from the models, we see a modest change in $M_*/L_{W1}$ with SED fitted stellar population age but an insignificant one with metallicity.

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arXiv2015

Galaxy And Mass Assembly (GAMA): end of survey report and data release 2

The Galaxy And Mass Assembly (GAMA) survey is one of the largest contemporary spectroscopic surveys of low-redshift galaxies. Covering an area of ~286 deg^2 (split among five survey regions) down to a limiting magnitude of r < 19.8 mag, we have collected spectra and reliable redshifts for 238,000 objects using the AAOmega spectrograph on the Anglo-Australian Telescope. In addition, we have assembled imaging data from a number of independent surveys in order to generate photometry spanning the wavelength range 1 nm - 1 m. Here we report on the recently completed spectroscopic survey and present a series of diagnostics to assess its final state and the quality of the redshift data. We also describe a number of survey aspects and procedures, or updates thereof, including changes to the input catalogue, redshifting and re-redshifting, and the derivation of ultraviolet, optical and near-infrared photometry. Finally, we present the second public release of GAMA data. In this release we provide input catalogue and targeting information, spectra, redshifts, ultraviolet, optical and near-infrared photometry, single-component S\'ersic fits, stellar masses, H$\alpha$-derived star formation rates, environment information, and group properties for all galaxies with r < 19.0 mag in two of our survey regions, and for all galaxies with r < 19.4 mag in a third region (72,225 objects in total). The database serving these data is available at http://www.gama-survey.org/.

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arXiv2013

Herschel-ATLAS: deep HST/WFC3 imaging of strongly lensed submillimeter galaxies

We report on deep near-infrared observations obtained with the Wide Field Camera 3 (WFC3) onboard the Hubble Space Telescope (HST) of the first five confirmed gravitational lensing events discovered by the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS). We succeed in disentangling the background galaxy from the lens to gain separate photometry of the two components. The HST data allow us to significantly improve on previous constraints of the mass in stars of the lensed galaxy and to perform accurate lens modelling of these systems, as described in the accompanying paper by Dye et al. We fit the spectral energy distributions of the background sources from near-IR to millimetre wavelengths and use the magnification factors estimated by Dye et al. to derive the intrinsic properties of the lensed galaxies. We find these galaxies to have star-formation rates of approximately 400 to 2000 M_sol/yr, with approximately (6-25)x10^10 M_sol of their baryonic mass already turned into stars. At these rates of star formation, all remaining molecular gas will be exhausted in less than 100 Myr, reaching a final mass in stars of a few 10^11 M_sol. These galaxies are thus proto-ellipticals caught during their major episode of star formation, and observed at the peak epoch z=1.5-3 of the cosmic star formation history of the Universe.

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arXiv2013

UltraVISTA: a new ultra-deep near-infrared survey in COSMOS

In this paper we describe the first data release of the UltraVISTA near-infrared imaging survey of the COSMOS field. We summarise the key goals and design of the survey and provide a detailed description of our data reduction techniques . We provide stacked, sky-subtracted images in $YJHK_{\rm s}$ and narrow-band filters constructed from data collected during the first year of UltraVISTA observations. Our stacked images reach $5σ$ $AB$ depths in an aperture of $2\arcsec$ diameter of $\sim 25$ in $Y$ and $\sim 24$ in $JHK_{\rm s}$ bands and all have sub-arcsecond seeing. To this $5σ$ limit, our $K_{\rm s}$ catalogue contains 216,268 sources. We carry out a series of quality assessment tests on our images and catalogues, comparing our stacks with existing catalogues. The $1σ$ astrometric RMS in both directions for stars selected with $17.0<K_{\rm s}\rm {(AB)} <19.5$ is $\sim 0.08\arcsec$ in comparison to the publicly-available COSMOS ACS catalogues. Our images are resampled to the same pixel scale and tangent point as the publicly available COSMOS data and so may be easily used to generate multi-colour catalogues using this data. All images and catalogues presented in this paper are publicly available through ESO's "phase 3" archiving and distribution system and from the UltraVISTA web site.

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arXiv2013

Galaxy And Mass Assembly (GAMA): Spectroscopic analysis

The Galaxy And Mass Assembly (GAMA) survey is a multiwavelength photometric and spectroscopic survey, using the AAOmega spectrograph on the Anglo-Australian Telescope to obtain spectra for up to ~300000 galaxies over 280 square degrees, to a limiting magnitude of r_pet < 19.8 mag. The target galaxies are distributed over 0<z<0.5 with a median redshift of z~0.2, although the redshift distribution includes a small number of systems, primarily quasars, at higher redshifts, up to and beyond z=1. The redshift accuracy ranges from sigma_v~50km/s to sigma_v~100km/s depending on the signal-to-noise of the spectrum. Here we describe the GAMA spectroscopic reduction and analysis pipeline. We present the steps involved in taking the raw two-dimensional spectroscopic images through to flux-calibrated one-dimensional spectra. The resulting GAMA spectra cover an observed wavelength range of 3750<lambda<8850 A at a resolution of R~1300. The final flux calibration is typically accurate to 10-20%, although the reliability is worse at the extreme wavelength ends, and poorer in the blue than the red. We present details of the measurement of emission and absorption features in the GAMA spectra. These measurements are characterised through a variety of quality control analyses detailing the robustness and reliability of the measurements. We illustrate the quality of the measurements with a brief exploration of elementary emission line properties of the galaxies in the GAMA sample. We demonstrate the luminosity dependence of the Balmer decrement, consistent with previously published results, and explore further how Balmer decrement varies with galaxy mass and redshift. We also investigate the mass and redshift dependencies of the [NII]/Halpha vs [OIII]/Hbeta spectral diagnostic diagram, commonly used to discriminate between star forming and nuclear activity in galaxies.

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arXiv2012

The VISTA Deep Extragalactic Observations (VIDEO) Survey

In this paper we describe the first data release of the the Visible and Infrared Survey Telescope for Astronomy (VISTA) Deep Extragalactic Observations (VIDEO) survey. VIDEO is a ~12degree^2 survey in the near-infrared Z,Y,J,H and K_s bands, specifically designed to enable the evolution of galaxies and large structures to be traced as a function of both epoch and environment from the present day out to z=4, and active galactic nuclei (AGN) and the most massive galaxies up to and into the epoch of reionization. With its depth and area, VIDEO will be able to fully explore the period in the Universe where AGN and starburst activity were at their peak and the first galaxy clusters were beginning to virialize. VIDEO therefore offers a unique data set with which to investigate the interplay between AGN, starbursts and environment, and the role of feedback at a time when it was potentially most crucial. We provide data over the VIDEO-XMM3 tile, which also covers the Canada-France-Hawaii-Telescope Legacy Survey Deep-1 field (CFHTLS-D1). The released VIDEO data reach a 5-sigma AB-magnitude depth of Z=25.7, Y=24.5, J=24.4, H=24.1 and K_s=23.8 in 2 arcsec diameter apertures (the full depth of Y=24.6 will be reached within the full integration time in future releases). The data are compared to previous surveys over this field and we find good astrometric agreement with the Two-Micron All Sky Survey, and source counts in agreement with the recently released UltraVISTA survey data. The addition of the VIDEO data to the CFHTLS-D1 optical data increases the accuracy of photometric redshifts and significantly reduces the fraction of catastrophic outliers over the redshift range 0<z<1 from 5.8 to 3.1 per cent in the absence of an i-band luminosity prior. (Truncated Abstract)

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arXiv2012

Mining the Herschel-ATLAS: submillimeter-selected blazars in equatorial fields

The Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) provides an unprecedented opportunity to search for blazars at sub-mm wavelengths. We cross-matched the FIRST radio source catalogue with the 11655 sources brighter than 35 mJy at 500μm in the \sim 135 square degrees of the sky covered by the H-ATLAS equatorial fields at 9 h and 15 h, plus half of the field at 12 h. We found that 379 of the H-ATLAS sources have a FIRST counterpart within 10 arcsec, including 8 catalogued blazars (plus one known blazar that was found at the edge of one the H-ATLAS maps). To search for additional blazar candidates we have devised new diagnostic diagrams and found that known blazars occupy a region of the log(S500μm/S350μm) vs. log(S500μm/S1.4GHz) plane separated from that of the other sub-mm sources with radio counterparts. Using this diagnostic we have selected 12 further candidates that turn out to be scattered in the (r-z) vs. (u-r) plane or in the WISE colour-colour diagram proposed by Massaro et al. (2012), where known blazars are concentrated in well defined strips. This suggests that the majority of them either are not blazars or have spectral energy distributions contaminated by their host galaxies. A significant fraction of true blazars are found to be hosted by star-forming galaxies. This finding, supported by an analysis of blazars detected in Planck 545 and 857 GHz bands, is at odds with the notion that blazar hosts are passive ellipticals and indicates that the sub-mm selection is providing a novel prospect on blazar properties. Based on an inspection of the available photometric data, including the WISE all-sky survey, the unpublished VIKING survey and new radio observations, we tentatively estimate that there are 11 blazars with synchrotron flux density S500μm > 35mJy over the considered area. This result already allows us to constrain blazar evolution models.

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arXiv2012

Herschel-ATLAS: VISTA VIKING near-IR counterparts in the Phase 1 GAMA 9h data

We identify near-infrared Ks band counterparts to Herschel-ATLAS sub-mm sources, using a preliminary object catalogue from the VISTA VIKING survey. The sub-mm sources are selected from the H-ATLAS Phase 1 catalogue of the GAMA 9h field, which includes all objects detected at 250, 350 or 500 um with the SPIRE instrument. We apply and discuss a likelihood ratio (LR) method for VIKING candidates within a search radius of 10" of the 22,000 SPIRE sources with a 5 sigma detection at 250 um. We find that 11,294(51%) of the SPIRE sources have a best VIKING counterpart with a reliability $R\ge 0.8$, and the false identification rate of these is estimated to be 4.2%. We expect to miss ~5% of true VIKING counterparts. There is evidence from Z-J and J-Ks colours that the reliable counterparts to SPIRE galaxies are marginally redder than the field population. We obtain photometric redshifts for ~68% of all (non-stellar) VIKING candidates with a median redshift of 0.405. Comparing to the results of the optical identifications supplied with the Phase I catalogue, we find that the use of medium-deep near-infrared data improves the identification rate of reliable counterparts from 36% to 51%.

astro-ph.CO↗

arXiv2012

Herschel-ATLAS: towards a sample of ~1000 strongly-lensed galaxies

While the selection of strongly lensed galaxies with 500{\mu}m flux density S_500>100 mJy has proven to be rather straightforward (Negrello et al. 2010), for many applications it is important to analyze samples larger than the ones obtained when confining ourselves to such a bright limit. Moreover, only by probing to fainter flux densities is possible to exploit strong lensing to investigate the bulk of the high-z star-forming galaxy population. We describe HALOS (the Herschel-ATLAS Lensed Objects Selection), a method for efficiently selecting fainter candidate strongly lensed galaxies, reaching a surface density of ~1.5-2 deg^-2, i.e. a factor of about 4 to 6 higher than that at the 100 mJy flux limit. HALOS will allow the selection of up to ~1000 candidate strongly lensed galaxies (with amplifications \mu>2) over the full H-ATLAS survey area. Applying HALOS to the H-ATLAS Science Demonstration Phase field (~14.4 deg^2) we find 31 candidate strongly lensed galaxies, whose candidate lenses are identified in the VIKING near-infrared catalog. Using the available information on candidate sources and candidate lenses we tentatively estimate a ~72% purity of the sample. The redshift distribution of the candidate lensed sources is close to that reported for most previous surveys for lensed galaxies, while that of candidate lenses extends to substantially higher redshifts than found in the other surveys. The counts of candidate strongly lensed galaxies are also in good agreement with model predictions (Lapi et al. 2011). Even though a key ingredient of the method is the deep near-infrared VIKING photometry, we show that H-ATLAS data alone allow the selection of a similarly deep sample of candidate strongly lensed galaxies with an efficiency close to 50%; a slightly lower surface density (~1.45 deg^-2) can be reached with a ~70% efficiency.

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arXiv2011

Spitzer IRAC identification of Herschel-ATLAS SPIRE sources

We use spitzer-IRAC data to identify near-infrared counterparts to submillimeter galaxies detected with Herschel-SPIRE at 250um in the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS). Using a likelihood ratio analysis we identify 146 reliable IRAC counterparts to 123 SPIRE sources out of the 159. We find that, compared to the field population, the SPIRE counterparts occupy a distinct region of 3.6 and 4.5um color-magnitude space, and we use this property to identify a further 23 counterparts to 13 SPIRE sources. The IRAC identification rate of 86% is significantly higher than those that have been demonstrated with wide-field ground-based optical and near-IR imaging of Herschel fields. We estimate a false identification rate of 3.6%, corresponding to 4 to 5 sources. Among the 73 counterparts that are undetected in SDSS, 57 have both 3.6 and 4.5um coverage. Of these 43 have [3.6] - [4.5]> 0 indicating that they are likely to be at z > 1.4. Thus, ~ 40% of identified SPIRE galaxies are likely to be high redshift (z > 1.4) sources. We discuss the statistical properties of the IRAC-identified SPIRE galaxy sample including far-IR luminosities, dust temperatures, star-formation rates, and stellar masses. The majority of our detected galaxies have 10^10 to 10^11 L_sun total IR luminosities and are not intense starbursting galaxies as those found at z ~ 2, but they have a factor of 2 to 3 above average specific star-formation rates compared to near-IR selected galaxy samples.

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arXiv2011

GAMA/H-ATLAS: The ultraviolet spectral slope and obscuration in galaxies

We use multiwavelength data from the Galaxy And Mass Assembly (GAMA) and Herschel ATLAS (H-ATLAS) surveys to compare the relationship between various dust obscuration measures in galaxies. We explore the connections between the ultraviolet (UV) spectral slope, $\beta$, the Balmer decrement, and the far infrared (IR) to $150\,$nm far ultraviolet (FUV) luminosity ratio. We explore trends with galaxy mass, star formation rate (SFR) and redshift in order to identify possible systematics in these various measures. We reiterate the finding of other authors that there is a large scatter between the Balmer decrement and the $\beta$ parameter, and that $\beta$ may be poorly constrained when derived from only two broad passbands in the UV. We also emphasise that FUV derived SFRs, corrected for dust obscuration using $\beta$, will be overestimated unless a modified relation between $\beta$ and the attenuation factor is used. Even in the optimum case, the resulting SFRs have a significant scatter, well over an order of magnitude. While there is a stronger correlation between the IR to FUV luminosity ratio and $\beta$ parameter than with the Balmer decrement, neither of these correlations are particularly tight, and dust corrections based on $\beta$ for high redshift galaxy SFRs must be treated with caution. We conclude with a description of the extent to which the different obscuration measures are consistent with each other as well as the effects of including other galactic properties on these correlations.

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arXiv2010

Galaxy and Mass Assembly (GAMA): Dust obscuration in galaxies and their recent star formation histories

We present self-consistent star formation rates derived through pan-spectral analysis of galaxies drawn from the Galaxy and Mass Assembly (GAMA) survey. We determine the most appropriate form of dust obscuration correction via application of a range of extinction laws drawn from the literature as applied to Halpha, [O{II}] and UV luminosities. These corrections are applied to a sample of 31,508 galaxies from the GAMA survey at z < 0.35. We consider several different obscuration curves, including those of Milky Way, Calzetti (2001) and Fischera and Dopita (2005) curves and their effects on the observed luminosities. At the core of this technique is the observed Balmer decrement, and we provide a prescription to apply optimal obscuration corrections using the Balmer decrement. We carry out an analysis of the star formation history (SFH) using stellar population synthesis tools to investigate the evolutionary history of our sample of galaxies as well as to understand the effects of variation in the Initial Mass Function (IMF) and the effects this has on the evolutionary history of galaxies. We find that the Fischera and Dopita (2005) obscuration curve with an R_{v} value of 4.5 gives the best agreement between the different SFR indicators. The 2200A feature needed to be removed from this curve to obtain complete consistency between all SFR indicators suggesting that this feature may not be common in the average integrated attenuation of galaxy emission. We also find that the UV dust obscuration is strongly dependent on the SFR.

astro-ph.CO↗

arXiv2010

Herschel-ATLAS: counterparts from the UV--NIR in the science demonstration phase catalogue

We present a technique to identify optical counterparts of 250 um-selected sources from the Herschel-ATLAS survey. Of the 6621 250 um > 32 mJy sources in our science demonstration catalogue we find that ~60 percent have counterparts brighter than r=22.4 mag in the Sloan Digital Sky Survey. Applying a likelihood ratio technique we are able to identify 2423 of the counterparts with a reliability R > 0.8. This is approximately 37 percent of the full 250 micron catalogue. We have estimated photometric redshifts for each of these 2423 reliable counterparts, while 1099 also have spectroscopic redshifts collated from several different sources, including the GAMA survey. We estimate the completeness of identifying counterparts as a function of redshift, and present evidence that 250 um-selected Herschel-ATLAS galaxies have a bimodal redshift distribution. Those with reliable optical identifications have a redshift distribution peaking at z ~ 0.25 +/- 0.05, while sub-mm colours suggest that a significant fraction with no counterpart above the r-band limit have z > 1. We also suggest a method for selecting populations of strongly-lensed high redshift galaxies. Our identifications are matched to UV--NIR photometry from the GAMA survey, and these data are available as part of the Herschel-ATLAS public data release.

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arXiv2009

The Herschel ATLAS

The Herschel ATLAS is the largest open-time key project that will be carried out on the Herschel Space Observatory. It will survey 510 square degrees of the extragalactic sky, four times larger than all the other Herschel surveys combined, in five far-infrared and submillimetre bands. We describe the survey, the complementary multi-wavelength datasets that will be combined with the Herschel data, and the six major science programmes we are undertaking. Using new models based on a previous submillimetre survey of galaxies, we present predictions of the properties of the ATLAS sources in other wavebands.

astro-ph.CO↗

arXiv2009

The MACHO Project HST Follow-Up: The Large Magellanic Cloud Microlensing Source Stars

We present Hubble Space Telescope (HST) WFPC2 photometry of 13 microlensed source stars from the 5.7 year Large Magellanic Cloud (LMC) survey conducted by the MACHO Project. The microlensing source stars are identified by deriving accurate centroids in the ground-based MACHO images using difference image analysis (DIA) and then transforming the DIA coordinates to the HST frame. None of these sources is coincident with a background galaxy, which rules out the possibility that the MACHO LMC microlensing sample is contaminated with misidentified supernovae or AGN in galaxies behind the LMC. This supports the conclusion that the MACHO LMC microlensing sample has only a small amount of contamination due to non-microlensing forms of variability. We compare the WFPC2 source star magnitudes with the lensed flux predictions derived from microlensing fits to the light curve data. In most cases the source star brightness is accurately predicted. Finally, we develop a statistic which constrains the location of the Large Magellanic Cloud (LMC) microlensing source stars with respect to the distributions of stars and dust in the LMC and compare this to the predictions of various models of LMC microlensing. This test excludes at > 90% confidence level models where more than 80% of the source stars lie behind the LMC. Exotic models that attempt to explain the excess LMC microlensing optical depth seen by MACHO with a population of background sources are disfavored or excluded by this test. Models in which most of the lenses reside in a halo or spheroid distribution associated with either the Milky Way or the LMC are consistent which these data, but LMC halo or spheroid models are favored by the combined MACHO and EROS microlensing results.

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