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191 results on '"Webster, R.L."'

1. The impact of tandem redundant/sky-based calibration in MWA Phase II data analysis

Author

Zhang, Z., Pober, J.C., Li, W., Hazelton, B.J., Morales, M.F., Trott, Cathryn, Jordan, Chris, Joseph, R.C., Beardsley, A., Barry, N., Byrne, R., Tingay, Steven, Chokshi, A., Hasegawa, K., Jacobs, D.C., Lanman, A., Line, Jack, Lynch, Christene, McKinley, Ben, Mitchell, D.A., Murray, Steven, Pindor, B., Rahimi, M., Takahashi, K., Wayth, Randall, Webster, R.L., Wilensky, M., Yoshiura, S., Zheng, Q., Zhang, Z., Pober, J.C., Li, W., Hazelton, B.J., Morales, M.F., Trott, Cathryn, Jordan, Chris, Joseph, R.C., Beardsley, A., Barry, N., Byrne, R., Tingay, Steven, Chokshi, A., Hasegawa, K., Jacobs, D.C., Lanman, A., Line, Jack, Lynch, Christene, McKinley, Ben, Mitchell, D.A., Murray, Steven, Pindor, B., Rahimi, M., Takahashi, K., Wayth, Randall, Webster, R.L., Wilensky, M., Yoshiura, S., and Zheng, Q.

Abstract

Precise instrumental calibration is of crucial importance to 21-cm cosmology experiments. The Murchison Widefield Array's (MWA) Phase II compact configuration offers us opportunities for both redundant calibration and sky-based calibration algorithms; using the two in tandem is a potential approach to mitigate calibration errors caused by inaccurate sky models. The MWA Epoch of Reionization (EoR) experiment targets three patches of the sky (dubbed EoR0, EoR1, and EoR2) with deep observations. Previous work in Li et al. (2018) and (2019) studied the effect of tandem calibration on the EoR0 field and found that it yielded no significant improvement in the power spectrum (PS) over sky-based calibration alone. In this work, we apply similar techniques to the EoR1 field and find a distinct result: The improvements in the PS from tandem calibration are significant. To understand this result, we analyse both the calibration solutions themselves and the effects on the PS over three nights of EoR1 observations. We conclude that the presence of the bright radio galaxy Fornax A in EoR1 degrades the performance of sky-based calibration, which in turn enables redundant calibration to have a larger impact. These results suggest that redundant calibration can indeed mitigate some level of model incompleteness error.

Published
2020

2. Modelling and peeling extended sources with shapelets: A Fornax A case study

Author

Line, Jack, Mitchell, D.A., Pindor, B., Riding, J.L., McKinley, Ben, Webster, R.L., Trott, Cathryn, Hurley-Walker, Natasha, Offringa, A.R., Line, Jack, Mitchell, D.A., Pindor, B., Riding, J.L., McKinley, Ben, Webster, R.L., Trott, Cathryn, Hurley-Walker, Natasha, and Offringa, A.R.

Abstract

To make a power spectrum (PS) detection of the 21-cm signal from the Epoch of Reionisation (EoR), one must avoid/subtract bright foreground sources. Sources such as Fornax A present a modelling challenge due to spatial structures spanning from arc seconds up to a degree. We compare modelling with multi-scale (MS) CLEAN components to 'shapelets', an alternative set of basis functions. We introduce a new image-based shapelet modelling package, SHAMFI. We also introduce a new CUDA simulation code (WODEN) to generate point source, Gaussian, and shapelet components into visibilities. We test performance by modelling a simulation of Fornax A, peeling the model from simulated visibilities, and producing a residual PS. We find the shapelet method consistently subtracts large-angular-scale emission well, even when the angular resolution of the data is changed. We find that when increasing the angular resolution of the data, the MS CLEAN model worsens at large angular scales. When testing on real Murchison Widefield Array data, the expected improvement is not seen in real data because of the other dominating systematics still present. Through further simulation, we find the expected differences to be lower than obtainable through current processing pipelines. We conclude shapelets are worthwhile for subtracting extended galaxies, and may prove essential for an EoR detection in the future, once other systematics have been addressed.

Published
2020

3. Biomarker Informed Management of Indeterminate Pulmonary Nodules with a Combined Clinical, Blood and Imaging-Based Biomarker Strategy

Author

Kammer, M., primary, Lakhani, D., additional, Balar, A., additional, Antic, S., additional, Kussrow, A.K., additional, Webster, R.L., additional, Mahapatra, S., additional, Barad, U., additional, Shah, C., additional, Atwater, T., additional, Diergaarde, B., additional, Qian, J., additional, Kaizer, A., additional, Balagurunathan, Y., additional, Helmey, S., additional, Chen, S.-C., additional, Bauza, J., additional, Deppen, S., additional, Sandler, K.L., additional, Maldonado, F., additional, Spira, A., additional, Billatos, E., additional, Schabath, M.B., additional, Gillies, R., additional, Wilson, D.O., additional, Grogan, E.L., additional, Landman, B., additional, Baron, A., additional, Chen, H., additional, Bornhop, D.J., additional, and Massion, P.P., additional

Published
2020
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4. Gridded and direct Epoch of Reionisation bispectrum estimates using the Murchison Widefield Array

Author

Trott, Cathryn, Watkinson, C.A., Jordan, Chris, Yoshiura, S., Majumdar, S., Barry, Nichole, Byrne, R., Hazelton, B.J., Hasegawa, K., Joseph, R., Kaneuji, T., Kubota, K., Li, W., Line, Jack, Lynch, Christene, McKinley, Ben, Mitchell, D.A., Morales, M.F., Murray, Steven, Pindor, B., Pober, J.C., Rahimi, M., Riding, J., Takahashi, K., Tingay, Steven, Wayth, Randall, Webster, R.L., Wilensky, M., Wyithe, J.S.B., Zheng, Q., Emrich, David, Beardsley, A.P., Booler, Tom, Crosse, B., Franzen, Thomas, Horsley, L., Johnston-Hollitt, Melanie, Kaplan, D.L., Kenney, David, Pallot, D., Sleap, G., Steele, K., Walker, Mia, Williams, Andrew, Wu, C., Trott, Cathryn, Watkinson, C.A., Jordan, Chris, Yoshiura, S., Majumdar, S., Barry, Nichole, Byrne, R., Hazelton, B.J., Hasegawa, K., Joseph, R., Kaneuji, T., Kubota, K., Li, W., Line, Jack, Lynch, Christene, McKinley, Ben, Mitchell, D.A., Morales, M.F., Murray, Steven, Pindor, B., Pober, J.C., Rahimi, M., Riding, J., Takahashi, K., Tingay, Steven, Wayth, Randall, Webster, R.L., Wilensky, M., Wyithe, J.S.B., Zheng, Q., Emrich, David, Beardsley, A.P., Booler, Tom, Crosse, B., Franzen, Thomas, Horsley, L., Johnston-Hollitt, Melanie, Kaplan, D.L., Kenney, David, Pallot, D., Sleap, G., Steele, K., Walker, Mia, Williams, Andrew, and Wu, C.

Abstract

We apply two methods to estimate the 21-cm bispectrum from data taken within the Epoch of Reionisation (EoR) project of the Murchison Widefield Array (MWA). Using data acquired with the Phase II compact array allows a direct bispectrum estimate to be undertaken on the multiple redundantly spaced triangles of antenna tiles, as well as an estimate based on data gridded to the uv-plane. The direct and gridded bispectrum estimators are applied to 21 h of high-band (167-197 MHz; z = 6.2-7.5) data from the 2016 and 2017 observing seasons. Analytic predictions for the bispectrum bias and variance for point-source foregrounds are derived. We compare the output of these approaches, the foreground contribution to the signal, and future prospects for measuring the bispectra with redundant and non-redundant arrays. We find that some triangle configurations yield bispectrum estimates that are consistent with the expected noise level after 10 h, while equilateral configurations are strongly foreground-dominated. Careful choice of triangle configurations may be made to reduce foreground bias that hinders power spectrum estimators, and the 21-cm bispectrum may be accessible in less time than the 21-cm power spectrum for some wave modes, with detections in hundreds of hours.

Published
2019

5. Robust statistics towards detection of the 21 cm signal from the Epoch of Reionization

Author

Trott, Cathryn, Fu, Shih Ching, Murray, Steven, Jordan, Chris, Line, Jack, Barry, N., Byrne, R., Hazelton, B.J., Hasegawa, K., Joseph, R., Kaneuji, T., Kubota, K., Li, W., Lynch, Christene, McKinley, Ben, Mitchell, D.A., Morales, M.F., Pindor, B., Pober, J.C., Rahimi, M., Takahashi, K., Tingay, Steven, Wayth, Randall, Webster, R.L., Wilensky, M., Wyithe, J.S.B., Yoshiura, S., Zheng, Q., Walker, Mia, Trott, Cathryn, Fu, Shih Ching, Murray, Steven, Jordan, Chris, Line, Jack, Barry, N., Byrne, R., Hazelton, B.J., Hasegawa, K., Joseph, R., Kaneuji, T., Kubota, K., Li, W., Lynch, Christene, McKinley, Ben, Mitchell, D.A., Morales, M.F., Pindor, B., Pober, J.C., Rahimi, M., Takahashi, K., Tingay, Steven, Wayth, Randall, Webster, R.L., Wilensky, M., Wyithe, J.S.B., Yoshiura, S., Zheng, Q., and Walker, Mia

Abstract

© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. We explore methods for robust estimation of the 21 cm signal from the Epoch of Reionization (EoR). A Kernel Density Estimator (KDE) is introduced for measuring the spatial temperature fluctuation power spectrum from the EoR. The KDE estimates the underlying probability distribution function of fluctuations as a function of spatial scale, and contains different systematic biases and errors to the typical approach to estimating the fluctuation power spectrum. Extraction of histograms of visibilities allows moments analysis to be used to discriminate foregrounds from 21 cm signal and thermal noise. We use the information available in the histograms, along with the statistical dis-similarity of foregrounds from two independent observing fields, to robustly separate foregrounds from cosmological signal, while making no assumptions about the Gaussianity of the signal. Using two independent observing fields to robustly discriminate signal from foregrounds is crucial for the analysis presented in this paper. We apply the techniques to 13 h of Murchison Widefield Array EoR data over two observing fields. We compare the output to that obtained with a comparative power spectrum estimation method, and demonstrate the reduced foreground contamination using this approach. Using the second moment obtained directly from the KDE distribution functions yields a factor of 2-3 improvement in power for k < 0.3 h Mpc-1 compared with a matched delay space power estimator, while weighting data by additional statistics does not offer significant improvement beyond that available for thermal noise-only weights.

Published
2019

7. Tidal disruptions of the Magellanic Clouds by the Milky Way

Author

Putman, M.E., Gibson, B.K., Staveley-Smith, L., Banks, G., Barnes, D.G., Bhatal, R., Disney, M.J., Ekers, R.D., Freeman, K.C., Koribalski, B., Knezek, P., Malin, D.F., Mould, J.R., Oosterloo, T., Price, R.M., Ryder, S.D., Sadler, E.M., Stewart, I., Stootman, F., Vaile, R.A., Webster, R.L., Wright, A.E., Haynes, R.F., Henning, P., Jerjen, H., and Kilborn, V.

Subjects
Galaxies -- Observations, Magellanic Clouds -- Observations, Milky Way -- Observations, Astronomical research -- Observations, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

An important consideration when determining the morphologies of the galaxies is their interaction over time. The interaction between the Milky Way and the neighbouring Large and Small Magellanic Clouds is one example. A new atomic-hydrogen survey of the southern skies reveal a new stream of gas moving around the Milky Way in the opposite direction to the trailing Magellan Stream, leading the motion of the clouds. It is probable that these leading and trailing streams have been torn from the Magellanic Clouds by gravitational tidal interaction.

Published
1998

8. On the detection and tracking of space debris using the Murchison Wdefield Array. I. Simulations and test observations demonstrate feasibility

Author

Tingay, Steven, Kaplan, D.L., McKinley, B., Briggs, F., Wayth, Randall, Hurley-Walker, N., Kennewell, J., Smith, C., Zhang, K., Arcus, W., Bhat, Ramesh, Emrich D., Herne, D., Kudryavtseva, N., Lynch, M., Ord, S.M., Waterson, M., Barnes, D.G., Bell, M., Gaensler, B.M., Lenc, E., Bernardi, G., Greenhill, L.J., Kasper, J.C., Bowman, J.D., Jacobs, D., Bunton, J.D., Desouza, L., Koenig, R., Pathikulangara, J., Stevens, J., Cappallo, R.J., Corey, B.E., Kincaid, B.B., Kratzenberg, E., Lonsdale, C.J., McWhirter, S.R., Rogers, A.E.E., Salah, J.E., Whitney, A.R., Deshpande, A., Prabu, T., Udaya Shankar, N., Srivani, K.S., Subrahmanyan, R., Ewall-Wice, A., Feng, L., Goeke, R., Morgan, E., Remillard, R.A., Williams, C.L., Hazelton, B.J., Morales, M.F., Johnston-Hollitt, M., Mitchell, D.A., Procopio, P., Riding, J., Webster, R.L., Wyithe, J.S.B., Oberoi, D., Roshi, A., Sault, R.J., Williams, A., Tingay, Steven, Kaplan, D.L., McKinley, B., Briggs, F., Wayth, Randall, Hurley-Walker, N., Kennewell, J., Smith, C., Zhang, K., Arcus, W., Bhat, Ramesh, Emrich D., Herne, D., Kudryavtseva, N., Lynch, M., Ord, S.M., Waterson, M., Barnes, D.G., Bell, M., Gaensler, B.M., Lenc, E., Bernardi, G., Greenhill, L.J., Kasper, J.C., Bowman, J.D., Jacobs, D., Bunton, J.D., Desouza, L., Koenig, R., Pathikulangara, J., Stevens, J., Cappallo, R.J., Corey, B.E., Kincaid, B.B., Kratzenberg, E., Lonsdale, C.J., McWhirter, S.R., Rogers, A.E.E., Salah, J.E., Whitney, A.R., Deshpande, A., Prabu, T., Udaya Shankar, N., Srivani, K.S., Subrahmanyan, R., Ewall-Wice, A., Feng, L., Goeke, R., Morgan, E., Remillard, R.A., Williams, C.L., Hazelton, B.J., Morales, M.F., Johnston-Hollitt, M., Mitchell, D.A., Procopio, P., Riding, J., Webster, R.L., Wyithe, J.S.B., Oberoi, D., Roshi, A., Sault, R.J., and Williams, A.

Abstract

The Murchison Widefield Array (MWA) is a new low-frequency interferometric radio telescope, operating in the benign radio frequency environment of remote Western Australia. The MWA is the low-frequency precursor to the Square Kilometre Array (SKA) and is the first of three SKA precursors to be operational, supporting a varied science mission ranging from the attempted detection of the Epoch of Reionization to the monitoring of solar flares and space weather. In this paper we explore the possibility that the MWA can be used for the purposes of Space Situational Awareness (SSA). In particular we propose that the MWA can be used as an element of a passive radar facility operating in the frequency range 87.5-108 MHz (the commercial FM broadcast band). In this scenario the MWA can be considered the receiving element in a bi-static radar configuration, with FM broadcast stations serving as non-cooperative transmitters. The FM broadcasts propagate into space, are reflected off debris in Earth orbit, and are received at the MWA. The imaging capabilities of the MWA can be used to simultaneously detect multiple pieces of space debris, image their positions on the sky as a function of time, and provide tracking data that can be used to determine orbital parameters. Such a capability would be a valuable addition to Australian and global SSA assets, in terms of southern and eastern hemispheric coverage. We provide a feasibility assessment of this proposal, based on simple calculations and electromagnetic simulations, that shows that the detection of sub-meter size debris should be possible (debris radius of >0.5 m to ∼1000 km altitude). We also present a proof-of-concept set of observations that demonstrate the feasibility of the proposal, based on the detection and tracking of the International Space Station via reflected FM broadcast signals originating in southwest Western Australia. These observations broadly validate our calculations and simulations. We discuss some signifi

Published
2013

9. A New Layout Optimization Technique for Interferometric Arrays, Applied to the Murchison Widefield Array

Author

Beardsley, A.P., Hazelton, B.J., Morales, M.F., Capallo, R.J., Goeke, R., Emrich, D., Lonsdale, C.J., Arcus, W., Barnes, D., Bernardi, G., Bowman, J.D., Bunton, J.D., Corey, B.E., Deshpande, A., DeSouza, L., Gaensler, B.M., Greenhill, L.J., Herne, D., Hewitt, J.N., Kaplan, D.L., Kasper, J.C., Kincaid, B.B., Koenig, R., Kratzenberg, E., Lynch, M.J., McWhirter, S.R., Mitchell, D.A., Morgan, E., Oberoi, D., Ord, S.M., Pathikulangara, J., Prabu, T., Remillard, R.A., Rogers, A.E.E., Roshi, A., Salah, J.E., Sault, R.J., Udaya Shankar, N., Srivani, K.S., Stevens, J., Subrahmanyan, R., Tingay, Steven, Wayth, Randall, Waterson, M., Webster, R.L., Whitney, A.R., Williams, A., Wyithe, J.S.B., Beardsley, A.P., Hazelton, B.J., Morales, M.F., Capallo, R.J., Goeke, R., Emrich, D., Lonsdale, C.J., Arcus, W., Barnes, D., Bernardi, G., Bowman, J.D., Bunton, J.D., Corey, B.E., Deshpande, A., DeSouza, L., Gaensler, B.M., Greenhill, L.J., Herne, D., Hewitt, J.N., Kaplan, D.L., Kasper, J.C., Kincaid, B.B., Koenig, R., Kratzenberg, E., Lynch, M.J., McWhirter, S.R., Mitchell, D.A., Morgan, E., Oberoi, D., Ord, S.M., Pathikulangara, J., Prabu, T., Remillard, R.A., Rogers, A.E.E., Roshi, A., Salah, J.E., Sault, R.J., Udaya Shankar, N., Srivani, K.S., Stevens, J., Subrahmanyan, R., Tingay, Steven, Wayth, Randall, Waterson, M., Webster, R.L., Whitney, A.R., Williams, A., and Wyithe, J.S.B.

Abstract

Antenna layout is an important design consideration for radio interferometers because it determines the quality of the snapshot point spread function (PSF, or array beam). This is particularly true for experiments targeting the 21-cm Epoch of Reionization signal as the quality of the foreground subtraction depends directly on the spatial dynamic range and thus the smoothness of the baseline distribution. Nearly all sites have constraints on where antennas can be placed even at the remote Australian location of the Murchison Widefield Array (MWA) there are rock outcrops, flood zones, heritages areas, emergency runways and trees. These exclusion areas can introduce spatial structure into the baseline distribution that enhances the PSF sidelobes and reduces the angular dynamic range. In this paper we present a new method of constrained antenna placement that reduces the spatial structure in the baseline distribution. This method not only outperforms random placement algorithms that avoid exclusion zones, but surprisingly outperforms random placement algorithms without constraints to provide what we believe are the smoothest constrained baseline distributions developed to date. We use our new algorithm to determine antenna placements for the originally planned MWA, and present the antenna locations, baseline distribution and snapshot PSF for this array choice.

Published
2012

10. The Murchison Widefield Array

Author

RFI2010, Mitchell, Daniel A., Greenhill, Lincoln J., Ord, Stephen M., Bernardi, Gianni, Wayth, Randall B., Edgar, Richard G., Clarke, Michael A., Dale, Kevin, Pfister, Hanspeter, Gleadow, Stewart J., Arcus, Wayne, Briggs, F.H., Benkevitch, L., Bowman, J.D., Bunton, J.D., Burns, S., Cappallo, R.J., Corey, B.E., de Oliveira-Costa, A., Desouza, L., Doeleman, S.S., Derome, M.F., Emrich, David, Glossop, Mark, Goeke, R., Gopala Krishna, M.R., Hazelton, B., Herne, David, Hewitt, J.N., Kamini, P.A., Kaplan, D.L., Kasper, J.C., Kincaid, B.B., Kocz, J., Kowald, E., Kratzenberg, E., Kumar, D., Lonsdale, C.J., Lynch, M.J., Madhavi, S., Matejek, M., McWhirter, S.R., Morales, M.F., Morgan, E., Oberoi, D., Pathikulangara, J., Prabu, T., Rogers, A., Salah, J.E., Sault, R.J., Udaya Shankar, N., Srivani, K.S., Stevens, J., Tingay, Steven, Vaccarella, A., Waterson, Mark, Webster, R.L., Whitney, A.R., Williams, A., Williams, C., RFI2010, Mitchell, Daniel A., Greenhill, Lincoln J., Ord, Stephen M., Bernardi, Gianni, Wayth, Randall B., Edgar, Richard G., Clarke, Michael A., Dale, Kevin, Pfister, Hanspeter, Gleadow, Stewart J., Arcus, Wayne, Briggs, F.H., Benkevitch, L., Bowman, J.D., Bunton, J.D., Burns, S., Cappallo, R.J., Corey, B.E., de Oliveira-Costa, A., Desouza, L., Doeleman, S.S., Derome, M.F., Emrich, David, Glossop, Mark, Goeke, R., Gopala Krishna, M.R., Hazelton, B., Herne, David, Hewitt, J.N., Kamini, P.A., Kaplan, D.L., Kasper, J.C., Kincaid, B.B., Kocz, J., Kowald, E., Kratzenberg, E., Kumar, D., Lonsdale, C.J., Lynch, M.J., Madhavi, S., Matejek, M., McWhirter, S.R., Morales, M.F., Morgan, E., Oberoi, D., Pathikulangara, J., Prabu, T., Rogers, A., Salah, J.E., Sault, R.J., Udaya Shankar, N., Srivani, K.S., Stevens, J., Tingay, Steven, Vaccarella, A., Waterson, Mark, Webster, R.L., Whitney, A.R., Williams, A., and Williams, C.

Published
2010

11. The Murchison Widefield Array: Design Overview

Author

Lonsdale, C.J., primary, Cappallo, R.J., additional, Morales, M.F., additional, Briggs, F.H., additional, Benkevitch, L., additional, Bowman, J.D., additional, Bunton, J.D., additional, Burns, S., additional, Corey, B.E., additional, deSouza, L., additional, Doeleman, S.S., additional, Derome, M., additional, Deshpande, A., additional, Gopala, M.R., additional, Greenhill, L.J., additional, Herne, D.E., additional, Hewitt, J.N., additional, Kamini, P.A., additional, Kasper, J.C., additional, Kincaid, B.B., additional, Kocz, J., additional, Kowald, E., additional, Kratzenberg, E., additional, Kumar, D., additional, Lynch, M.J., additional, Madhavi, S., additional, Matejek, M., additional, Mitchell, D.A., additional, Morgan, E., additional, Oberoi, D., additional, Ord, S., additional, Pathikulangara, J., additional, Prabu, T., additional, Rogers, A., additional, Roshi, A., additional, Salah, J.E., additional, Sault, R.J., additional, Shankar, N.U., additional, Srivani, K.S., additional, Stevens, J., additional, Tingay, S., additional, Vaccarella, A., additional, Waterson, M., additional, Wayth, R.B., additional, Webster, R.L., additional, Whitney, A.R., additional, Williams, A., additional, and Williams, C., additional

Published
2009
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17. A study of neutral hydrogen in five small galaxy groups.

Author

Barnes, D.G. and Webster, R.L.

Subjects
*GALAXIES, *IMAGING systems in astronomy, *OPEN clusters of stars, *ASTRONOMICAL observations
Abstract

High-resolution H i imaging observations of a heterogeneous sample of small galaxy groups are presented. The five galaxy groups studied show a broad range of individual H i properties: e.g. loose groups surrounding LGG 138 and the genuinely compact LGG 455 are identified; a massive ring of neutral gas is discovered encircling two luminous galaxies in the LGG 138 group; a galaxy-sized mass of H i is found in LGG 455 confined to an extragalactic cloud which exceeds the threshold density for star formation, yet is optically invisible; and the CCG 1 group is argued to be a chance alignment of Centaurus cluster galaxies. Global results of the study are that the deficit of H i flux in synthesis imaging data compared with single-dish data is put forward as a quantitative measure of the diffuseness of neutral gas in galaxy groups; several groups contain gas-poor galaxies that ordinarily would contain detectable quantities of H i – this is interpreted as being caused by an increased chance of gas-sweeping collisions in the group environment; and some evidence is found to support previous findings that compact groups preferentially occur in loose systems. [ABSTRACT FROM AUTHOR]

Published
2001
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18. Red synchrotron jets in Parkes quasars.

Author

Whiting, M.T., Webster, R.L., and Francis, P.J.

Subjects
*SPECTRAL energy distribution, *QUASARS, *SYNCHROTRON radiation, *OPTICAL polarization
Abstract

We present model fits to spectral energy distributions in the optical and near-infrared of >100 flat-spectrum radio quasars from the Parkes Half-Jansky Flat-spectrum Sample. We find that ∼40 per cent of the sources have power-law spectral energy distributions (SEDs), while a similar number show evidence for two primary components: a blue power law and optical synchrotron emission. The blue power law is similar to the dominant component observed in the spectra of optically selected quasars. There is strong evidence that the synchrotron component has a turnover in the ultraviolet–optical rest frame of the spectrum. In the remaining sources, it is likely that the synchrotron peaks at longer wavelengths. This mixture of two components is supported by optical polarization measurements in a subgroup of the sources. The sources with power-law SEDs show evidence for an excess number of red power-law slopes compared with optically selected quasars. There are additional spectral components in some of the sources, such as dust and the underlying galaxy, which have not been considered here. [ABSTRACT FROM AUTHOR]

Published
2001
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19. Using the 2 degree Field galaxy redshift survey to detect gravitationally lensed quasars.

Author

Mortlock, D.J. and Webster, R.L.

Subjects
*GRAVITATIONAL lenses, *QUASARS
Abstract

Galaxy redshift surveys can be used to detect gravitationally lensed quasars if the spectra obtained are searched for the emission lines of quasars. Previous investigations of this possibility have used simple models to show that the 2 degree Field (2dF) redshift survey could yield several tens of new lenses, and that the larger Sloan Digital Sky Survey should contain an order of magnitude more. However the particular selection effects of the samples were not included in these calculations, limiting the robustness of the predictions; thus a more detailed simulation of the 2dF survey was undertaken here. The use of an isophotal magnitude limit reduces both the depth of the sample and the expected number of lenses, but more important is the Automatic Plate Measuring survey's star–galaxy separation algorithm, used to generate the 2dF input catalogue. It is found that most quasar lenses are classed as merged stars, with only the few lenses with low-redshift deflectors likely to be classified as galaxies. Explicit inclusion of these selection effects implies that the 2dF survey should contain 10 lenses on average. The largest remaining uncertainty is the lack of knowledge of the ease with which any underlying quasars can be extracted from the survey spectra. [ABSTRACT FROM AUTHOR]

Published
2001
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20. Interpretation of the OGLE Q2237+0305 microlensing light curve (1997–1999).

Author

Wyithe, J.S.B., Webster, R.L., and Turner, E.L.

Subjects
*QUASARS, *LIGHT curves
Abstract

The four bright images of the gravitationally lensed quasar Q2237+0305 are being monitored from the ground (e.g. OGLE collaboration, Apache Point Observatory) in the hope of observing a high-magnification event (HME). Over the past three seasons (1997–1999) the OGLE collaboration has produced microlensing light curves with unprecedented coverage. These demonstrate smooth, independent (therefore microlensing) variability between the images. We have retrospectively applied probability functions for HME parameters to the observed light-curve features. We conclude that the 1999 image C peak was as a result of the source having passed outside of a cusp rather than to a caustic crossing. In addition, we find that the image C light curve shows evidence for a caustic crossing between the 1997 and the 1998 observing seasons involving the appearance of new critical images. Our models predict that the next image C event is most likely to arrive 500 d following the 1999 peak, but with a large uncertainty (∼100–2000 d). Finally, given the image A light-curve derivative at the end of the 1999 observing season, our modelling suggests that a caustic crossing will occur between the 1999 and the 2000 observing seasons, suggesting a minimum for the image A light curve ∼1–1.5 mag fainter than the 1999 November level. [ABSTRACT FROM AUTHOR]

Published
2000
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21. Predicting caustic-crossing high-magnification events in Q2237+0305.

Author

Wyithe, J.S.B., Webster, R.L., Turner, E.L., and Agol, E.

Subjects
*QUASARS, *ASTRONOMICAL photometry
Abstract

The central regions of the gravitationally lensed quasar Q2237+0305 can be indirectly resolved on nano-arcsecond scales if viewed spectrophotometrically during a microlensing high-magnification event (HME). Q2237+0305 is currently being monitored from the ground (e.g. OGLE collaboration, Apache Point Observatory), with the goal, among others, of triggering ground- and spacecraft-based target-of-opportunity (TOO) observations of such an HME. In this work we investigate the rate of change (trigger) in image brightness that signals an imminent HME and importantly, the separation between the trigger and the event peak. In addition, we produce colour dependent model light curves by combining high-resolution microlensing simulations with a realistic model for a thermal accretion disc source. We make hypothetical TOO spectroscopic observations using our determination of the appropriate trigger as a guide. We find that if the source spectrum varies with source radius, a three-observation TOO programme should be able to observe a microlensing change in the continuum slope following a light-curve trigger with a success rate of &gsim;80 per cent. [ABSTRACT FROM AUTHOR]

Published
2000
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22. A small source in Q2237+0305?

Author

Wyithe, J.S.B., Webster, R.L., and Turner, E.L.

Subjects
*STELLAR spectra, *LENSES
Abstract

Microlensing in Q2237+0305 between 1985 and 1995 has been interpreted in two different ways. First, the observed variations can be explained through microlensing by stellar mass objects of a continuum source with dimensions significantly smaller than the microlens Einstein Radius (η[sub 0]), but consistent with that expected for thermal accretion discs. However, other studies have shown that models having sources as large as 5η[sub 0] can reproduce the observed variation. In this paper we present evidence in favour of a small source. Our approach uses the distribution of microlensed light-curve derivatives to place statistical limits (as a function of source size) on the number of microlens Einstein radii crossed by the source during the monitoring period. In contrast with previous analyses, our results are therefore not dependent on an assumed time-scale. Limits on the source size are obtained from two separate light-curve features. First, recently published monitoring data show large variations (∼0.8–1.5 mag) between image brightnesses over a period of ∼700 d or ∼15 per cent of the monitoring period. Secondly, the 1988 peak in the image A light curve had a duration that is a small fraction (&lsim;0.02) of the monitoring period. Such rapid microlensing rises and short microlensing peaks only occur for small sources. We find that the observed large, rapid variation limits the source size to be <0.2η[sub 0] (95 per cent confidence). The width of the light-curve peak provides a stronger constraint of <0.025η[sub 0] (99 per cent confidence). The Einstein radius (projected into the source plane) of the average microlens mass in Q2237+0305 is η[sub 0]∼10[sup 17]√ cm. The interpretation that stars are responsible for microlensing in Q2237+0305 therefore results in limits on the continuum source size that are consistent with current accretion disc theory. [ABSTRACT FROM AUTHOR]

Published
2000
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23. The clustering of colour-selected galaxies.

Author

Brown, M.J.I., Webster, R.L., and Boyle, B.J.

Subjects
*ANGULAR correlations (Nuclear physics), *GALAXY clusters
Abstract

We present measurements of the angular correlation function of galaxies selected from a B[sub J]∼23.5 multicolour survey of two 5°×5° fields located at high galactic latitudes. The galaxy catalogue of ∼4×10[sup 5] galaxies is comparable in size to catalogues used to determine the galaxy correlation function at low redshift. Measurements of the z∼0.4 correlation function at large angular scales show no evidence for a break from a power law, although our results are not inconsistent with a break at &gsim;15 h[sup -1] Mpc. Despite the large fields-of-view, there are large discrepancies between the measurements of the correlation function in each field, possibly caused by dwarf galaxies within z∼0.11 clusters near the South Galactic Pole. Colour selection is used to study the clustering of galaxies from z∼0 to z∼0.4. The galaxy correlation function is found to depend strongly on colour, with red galaxies more strongly clustered than blue galaxies by a factor of &gsim;5 at small scales. The slope of the correlation function is also found to vary with colour, with γ∼1.8 for red galaxies and γ∼1.5 for blue galaxies. The clustering of red galaxies is consistently strong over the entire magnitude range studied, although there are large variations between the two fields. The clustering of blue galaxies is extremely weak over the observed magnitude range, with clustering consistent with r[sub 0]∼2 h[sup -1] Mpc. This is weaker than the clustering of late-type galaxies in the local Universe, and suggests that galaxy clustering is more strongly correlated with colour than morphology. This may also be the first detection of a substantial low-redshift galaxy population with clustering properties similar to faint blue galaxies. [ABSTRACT FROM AUTHOR]

Published
2000
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24. The rate of caustic crossing microlensing events for Q2237+0305.

Author

Wyithe, J.S.B., Webster, R.L., and Turner, E.L.

Subjects
*SPECTROPHOTOMETRY, *QUASARS
Abstract

Spectrophotometric observations of the gravitationally microlensed quasar Q2237+0305 made during a high magnification event (HME) potentially provide a very powerful tool for probing the structure of the accretion discs of quasars, on scales of ∼10[sup -8] arcsec. In cases where the HME is produced by a single caustic (SHME), microlensing induced changes in the spectrum during the event may be used to directly infer the source intensity profile. Several groups are actively monitoring Q2237+0305 with this goal in mind. How often we can expect to observe an HME is dependent on the lens system parameters of galactic transverse velocity, mean microlens mass and the size of the magnified continuum source. We have previously used published microlensed light curves to obtain expressions for the likelihood of the values for these parameters. Here, we use this information to investigate the expected rate of SHMEs. We find the average rate of SHMEs as well as the number that we can expect to observe over periods of a decade and of a single observing season. We find that the average SHME rate summed over all images of Q2237+0305 is in the range of 1.5±0.6–6.2±1.3 events per decade. During the period following a caustic crossing we find that the event rate in the corresponding image is enhanced by ∼50–100 per cent, and therefore that the overall event rate may be higher during these periods. From the distribution of events expected during a six month period we find that there is one chance in ∼4–10 of observing an SHME per observing season. The systematic dependence in these values arises from the different assumptions for smooth matter content, orientation of the galactic transverse velocity and the size of photometric error in the monitoring data. The results support continued monitoring of Q2237+0305 with the aim of obtaining detailed spectroscopic and photometric observations of an SHME. [ABSTRACT FROM AUTHOR]

Published
2000
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25. Limits on the microlens mass function of Q2237+0305.

Author

Wyithe, J.S.B., Webster, R.L., and Turner, E.L.

Subjects
*GRAVITATIONAL lenses, *QUASARS, *STELLAR mass, *MEASUREMENT, *ASTRONOMICAL observations
Abstract

Gravitational microlensing at cosmological distances is potentially a powerful tool for probing the mass functions of stars and compact objects in other galaxies. In the case of multiply imaged quasars, microlensing data have been used to determine the average microlens mass. However, the measurements have relied on an assumed transverse velocity for the lensing galaxy. Since the measured mass scales with the square of the transverse velocity, published mass limits are quite uncertain. In the case of Q2237+0305 we have properly constrained this uncertainty. The distribution of light-curve derivatives allows a quantitative treatment of the relative rates of microlensing arising from proper motions of microlenses, the orbital stream motion of microlenses and the bulk galactic transverse velocity. By demanding that the microlensing rate arising from the motions of microlenses is the minimum that should be observed we determine lower limits for the average mass of stars and compact objects in the bulge of Q2237+0305. If microlenses are assumed to move in an orbital stream the lower limit ranges between 0.005 and 0.023 M[sub ⊙], where the systematic dependence arises from the fraction of smooth matter and the size of photometric error assumed for the published monitoring data. However, if the microlenses are assumed to move according to an isotropic velocity dispersion then a larger lower limit of 0.019–0.11 M[sub ⊙] is obtained. A significant contribution of Jupiter-mass compact objects to the mass distribution of the galactic bulge of Q2237+0305 is therefore ruled out unambiguously. [ABSTRACT FROM AUTHOR]

Published
2000
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26. A gravitational microlensing determination of continuum source size in Q2237+0305.

Author

Wyithe, J.S.B., Webster, R.L., Turner, E.L., and Mortlock, D.J.

Subjects
*QUASARS, *GRAVITATIONAL lenses, *ASTRONOMICAL observations
Abstract

Following the detection of a gravitational microlensing high-magnification event (HME) in Q2237+0305A, attempts have been made to place limits on the dimensions of the quasar continuum source. The analyses have studied either the observed event magnitude or the event duration. The latter approach has been hampered by lack of knowledge about the transverse velocity of the lensing galaxy. We obtain both upper and lower statistical limits on the size of the continuum source from the observed HME using determinations of transverse velocity obtained from the published monitoring data. Our calculations take account of the caustic orientation as well as the component of the caustic velocity that results from stellar proper motions. Our determination of the source size relies on an estimated duration of 52 d for the HME, and so will be refined when more HMEs are observed. We find that the upper and lower limits on the magnified region of the R-band continuum source are 6×10[sup 15] and 2×10[sup 13] cm, respectively (99 per cent confidence). Through consideration of the joint probability for source size and mean microlens mass we find that the mean mass lies between ∼0.01 and ∼1 M[sub ⊙] (95 per cent confidence). [ABSTRACT FROM AUTHOR]

Published
2000
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27. The distribution of microlensed light-curve derivatives: the relationship between stellar proper motions and transverse velocity.

Author

Wyithe, J.S.B., Webster, R.L., and Turner, E.L.

Subjects
*RADIAL velocity of stars, *LENSES
Abstract

We present a method for computing the probability distribution of microlensed light-curve derivatives both in the case of a static lens with a transverse velocity, and in the case of microlensing that is produced through stellar proper motions. The distributions are closely related in form, and can be considered equivalent after appropriate scaling of the input transverse velocity. The comparison of the distributions in this manner provides a consistent way to consider the relative contribution to microlensing (both large and small fluctuations) of the two classes of motion, a problem that is otherwise an extremely expensive computational exercise. We find that the relative contribution of stellar proper motions to the microlensing rate is independent of the mass function assumed for the microlenses, but is a function of optical depth and shear. We find that stellar proper motions produce a higher overall microlensing rate than a transverse velocity of the same magnitude. This effect becomes more pronounced at higher optical depth. With the introduction of shear, the relative rates of microlensing become dependent on the direction of the transverse velocity. This may have important consequences in the case of quadruply lensed quasars such as Q2237+0305, where the alignment of the shear vector with the source trajectory varies between images. [ABSTRACT FROM AUTHOR]

Published
2000
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28. Jatropha dioica

Author

G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, and G.L. Webster & R.L. Wilbur

Abstract

Angiosperms, http://name.umdl.umich.edu/IC-HERB00IC-X-1194373%5DMICH-V-1194373, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1194373/MICH-V-1194373/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1950

29. Doodia lyonii

Author

Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, and Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur

Abstract

Pteridophytes, http://name.umdl.umich.edu/IC-HERB00IC-X-1186413%5DMICH-V-1186413, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1186413/MICH-V-1186413/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1947

30. Blechnum appendiculatum

Author

Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, and Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur

Abstract

Pteridophytes, http://name.umdl.umich.edu/IC-HERB00IC-X-1186270%5DMICH-V-1186270, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1186270/MICH-V-1186270/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1947

31. Asplenium macraei

Author

G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, and G.L. Webster & R.L. Wilbur

Abstract

Pteridophytes, http://name.umdl.umich.edu/IC-HERB00IC-X-1191543%5DMICH-V-1191543, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1191543/MICH-V-1191543/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1948

32. Asplenium kaulfussii

Author

Harold. St. John, G.L. Webster & R.L. Wilbur, Harold. St. John, G.L. Webster & R.L. Wilbur, Harold. St. John, G.L. Webster & R.L. Wilbur, and Harold. St. John, G.L. Webster & R.L. Wilbur

Abstract

Pteridophytes, http://name.umdl.umich.edu/IC-HERB00IC-X-1176495%5DMICH-V-1176495, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1176495/MICH-V-1176495/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1947

33. Cibotium nealiae

Author

Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, and Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur

Abstract

Pteridophytes, http://name.umdl.umich.edu/IC-HERB00IC-X-1193068%5DMICH-V-1193068, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1193068/MICH-V-1193068/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1947

34. Sadleria pallida

Author

Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, and Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur

Abstract

Pteridophytes, http://name.umdl.umich.edu/IC-HERB00IC-X-1191761%5DMICH-V-1191761, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1191761/MICH-V-1191761/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1947

35. Cibotium menziesii

Author

Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, and Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur

Abstract

Pteridophytes, http://name.umdl.umich.edu/IC-HERB00IC-X-1193372%5DMICH-V-1193372, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1193372/MICH-V-1193372/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1947

36. Coniogramme pilosa

Author

Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, and Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur

Abstract

Pteridophytes, http://name.umdl.umich.edu/IC-HERB00IC-X-1175510%5DMICH-V-1175510, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1175510/MICH-V-1175510/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1947

37. Doryopteris decora

Author

Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur, and Harold St. John, R.S. Cowan, G.L. Webster & R.L. Wilbur

Abstract

Pteridophytes, http://name.umdl.umich.edu/IC-HERB00IC-X-1175636%5DMICH-V-1175636, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1175636/MICH-V-1175636/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1947

38. Psilotum complanatum

Author

G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, and G.L. Webster & R.L. Wilbur

Abstract

Pteridophytes, http://name.umdl.umich.edu/IC-HERB00IC-X-1175018%5DMICH-V-1175018, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1175018/MICH-V-1175018/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1948

39. Isopterygium micans

Author

G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, and G.L. Webster & R.L. Wilbur

Abstract

Bryophytes, http://name.umdl.umich.edu/IC-HERB00IC-X-537722%5DMICH-B-537722, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/537722/MICH-B-537722/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1950

40. Euphorbia corollata

Author

G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, and G.L. Webster & R.L. Wilbur

Abstract

Angiosperms, http://name.umdl.umich.edu/IC-HERB00IC-X-1245363%5DMICH-V-1245363, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1245363/MICH-V-1245363/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1950

41. Proserpinaca palustris

Author

G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, and G.L. Webster & R.L. Wilbur

Abstract

Angiosperms, http://name.umdl.umich.edu/IC-HERB00IC-X-1223739%5DMICH-V-1223739, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1223739/MICH-V-1223739/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1950

42. Tillandsia usneoides

Author

G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, and G.L. Webster & R.L. Wilbur

Abstract

Angiosperms, http://name.umdl.umich.edu/IC-HERB00IC-X-1197281%5DMICH-V-1197281, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1197281/MICH-V-1197281/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1950

43. Euphorbia bombensis

Author

G.L. Webster & R.L. Wilbbur, G.L. Webster & R.L. Wilbbur, G.L. Webster & R.L. Wilbbur, and G.L. Webster & R.L. Wilbbur

Abstract

Angiosperms, http://name.umdl.umich.edu/IC-HERB00IC-X-1288891%5DMICH-V-1288891, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1288891/MICH-V-1288891/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1950

44. Euphorbia geyeri

Author

G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, and G.L. Webster & R.L. Wilbur

Abstract

Angiosperms, http://name.umdl.umich.edu/IC-HERB00IC-X-1288918%5DMICH-V-1288918, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1288918/MICH-V-1288918/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1950

45. Euphorbia hypericifolia

Author

G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, and G.L. Webster & R.L. Wilbur

Abstract

Angiosperms, http://name.umdl.umich.edu/IC-HERB00IC-X-1288610%5DMICH-V-1288610, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1288610/MICH-V-1288610/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1950

46. Urochloa ciliatissima

Author

G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, and G.L. Webster & R.L. Wilbur

Abstract

Angiosperms, http://name.umdl.umich.edu/IC-HERB00IC-X-1426004%5DMICH-V-1426004, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1426004/MICH-V-1426004/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1950

47. Euphorbia missurica

Author

G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, and G.L. Webster & R.L. Wilbur

Abstract

Angiosperms, http://name.umdl.umich.edu/IC-HERB00IC-X-1288487%5DMICH-V-1288487, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1288487/MICH-V-1288487/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1950

48. Euphorbia nutans

Author

G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, G.L. Webster & R.L. Wilbur, and G.L. Webster & R.L. Wilbur

Abstract

Angiosperms, http://name.umdl.umich.edu/IC-HERB00IC-X-1288322%5DMICH-V-1288322, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1288322/MICH-V-1288322/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1950

49. Rhynchospora plumosa

Author

G.L. Webster, R.L. Wilbur, G.L. Webster, R.L. Wilbur, G.L. Webster, R.L. Wilbur, and G.L. Webster, R.L. Wilbur

Abstract

Angiosperms, http://name.umdl.umich.edu/IC-HERB00IC-X-1400918%5DMICH-V-1400918, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1400918/MICH-V-1400918/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1950

50. Rhynchospora glomerata

Author

G.L. Webster, R.L. Wilbur, G.L. Webster, R.L. Wilbur, G.L. Webster, R.L. Wilbur, and G.L. Webster, R.L. Wilbur

Abstract

Angiosperms, http://name.umdl.umich.edu/IC-HERB00IC-X-1400273%5DMICH-V-1400273, https://quod.lib.umich.edu/cgi/i/image/api/thumb/herb00ic/1400273/MICH-V-1400273/!250,250, The University of Michigan Library provides access to these materials for educational and research purposes. Some materials may be protected by copyright. If you decide to use any of these materials, you are responsible for making your own legal assessment and securing any necessary permission. If you have questions about the collection, please contact the Herbarium professional staff: herb-dlps-help@umich.edu. If you have concerns about the inclusion of an item in this collection, please contact Library Information Technology: libraryit-info@umich.edu., https://www.lib.umich.edu/about-us/policies/copyright-policy

Published
1950

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