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L Christensen - One of the best experts on this subject based on the ideXlab platform.
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dark matter rich early type galaxies in the Cassowary 5 strong lensing system
Monthly Notices of the Royal Astronomical Society, 2011Co-Authors: Claudio Grillo, L ChristensenAbstract:We study the strong gravitational lensing system number 5 identified by the CAmbridge Sloan Survey Of Wide ARcs in the skY (Cassowary). In this system, a source at redshift 1.069 is lensed into four detected images by two early-type galaxies at redshift 0.388. The average projected angular distance of the multiple images from the primary lens is 12.6 kpc, corresponding to approximately 1.3 times the value of the galaxy effective radius. The observed positions of the multiple images are well reproduced by a model in which the total mass distribution of the deflector is described in terms of two singular isothermal sphere profiles and a small external shear component. The values of the effective velocity dispersions of the two lens galaxies are 328+7− 8 and 350+17− 18 km s−1. The best-fitting lensing model predicts magnification values larger than 2 for each multiple image and a total magnification factor of 17. By modelling the lens galaxy spectral energy distributions, we measure lens luminous masses of (3.09 ± 0.30) × 1011 and (5.87 ± 0.58) × 1011 M⊙ and stellar mass-to-light ratios of 2.5 ± 0.3 and 2.8 ± 0.3 M⊙ L−1⊙, i (in the observed i band). These values are used to disentangle the luminous and dark matter components in the vicinity of the multiple images. We estimate that the dark over total mass ratio projected within a cylinder centred on the primary lens and with a radius of 12.6 kpc is 0.8 ± 0.1. Inside the effective radii of the two galaxies, we measure projected total mass-to-light ratios of 12.6 ± 1.4 and 13.1 ± 1.7 M⊙ L−1⊙, i. We contrast these measurements with the typical values found at similar distances (in units of the effective radius) in isolated lens galaxies and show that the amount of dark matter present in these lens galaxies is almost a factor 4 larger than in field lens galaxies with comparable luminous masses. Data and models are therefore consistent with interpreting the lens of this system as a galaxy group. We infer that the overdense environment and dark matter concentration in these galaxies must have affected the assembly of the lens luminous mass components, resulting in the large values of the galaxy effective radii. We conclude that further multidiagnostics analyses on the internal properties of galaxy groups have the potential of providing us a unique insight into the complex baryonic and dark matter physics interplay that rules the formation of cosmological structures.
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x shooter observations of the gravitational lens system Cassowary 5
Monthly Notices of the Royal Astronomical Society, 2010Co-Authors: V Belokurov, L Christensen, S Dodorico, Max Pettini, Wyn N Evans, M Kellogg, J VernetAbstract:We confirm an eighth gravitational lens system in the CAmbridge Sloan Survey Of Wide ARcs in the skY (Cassowary) catalogue. Exploratory observations with the X-shooter spectrograph on the Very Large Telescope of the European Southern Observatory show the system Cassowary 5 (CSWA 5) to consist of at least three images of a blue star-forming galaxy at z = 1.0686, lensed by an apparent foreground group of red galaxies, one of which is at z = 0.3877. The lensed galaxy exhibits a rich spectrum with broad interstellar absorption lines and a wealth of nebular emission lines. Preliminary analysis of these features shows the galaxy to be young, with an age of ~25-50 Myr. With a star formation rate of ~20 M ⊙ yr -1 , the galaxy has already assembled a stellar mass M * ~ 3 × 10 9 M ⊙ and reached half-solar metallicity. Its blue spectral energy distribution and Balmer line ratios suggest negligible internal dust extinction. A more in-depth analysis of the properties of this system is currently hampered by the lack of a viable lensing model. However, it is already clear that CSWA 5 shares many of its physical characteristics with the general population of UV-selected galaxies at redshifts z = 1-3, motivating further study of both the source and the foreground mass concentration responsible for the gravitational lensing.
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x shooter observations of the gravitational lens system Cassowary 5
arXiv: Cosmology and Nongalactic Astrophysics, 2010Co-Authors: L Christensen, S Dodorico, Max Pettini, Wyn N Evans, M Kellogg, V Belokurov, J VernetAbstract:We confirm an eighth gravitational lens system in the Cassowary catalogue. Exploratory observations with the X-shooter spectrograph on the VLT show the system CSWA5 to consist of at least three images of a blue star-forming galaxy at z = 1.0686, lensed by an apparent foreground group of red galaxies one of which is at z = 0.3877. The lensed galaxy exhibits a rich spectrum with broad interstellar absorption lines and a wealth of nebular emission lines. Preliminary analysis of these features shows the galaxy to be young, with an age of 25-50 Myr. With a star-formation rate of approximately 20 solar masses/yr, the galaxy has already assembled a stellar mass of 3 x 10^9 solar masses and reached half-solar metallicity. Its blue spectral energy distribution and Balmer line ratios suggest negligible internal dust extinction. A more in-depth analysis of the properties of this system is currently hampered by the lack of a viable lensing model. However, it is already clear that CSWA5 shares many of its physical characteristics with the general population of UV-selected galaxies at redshifts z = 1-3, motivating further study of both the source and the foreground mass concentration responsible for the gravitational lensing.
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Cassowary 20 a wide separation einstein cross identified with the x shooter spectrograph
Monthly Notices of the Royal Astronomical Society, 2010Co-Authors: Max Pettini, L Christensen, S Dodorico, Wyn N Evans, V Belokurov, Paul C Hewett, S E Koposov, E MasonAbstract:We have used spectra obtained with X-shooter, the triple arm optical-infrared spectrograph recently commissioned on the Very Large Telescope of the European Southern Observatory, to confirm the gravitational lens nature of the CAmbridge Sloan Survey Of Wide ARcs in the skY (Cassowary) candidate CSWA 20. This system consists of a luminous red galaxy at redshift z abs = 0.741, with a very high velocity dispersion, σ lens ≃ 500 km s -1 , which lenses a blue star-forming galaxy at z em = 1.433 into four images with a mean separation of ~6 arcsec. The source shares many of its properties with those of UV-selected galaxies at z = 2-3: it is forming stars at a rate SFR ≃ 25 M ⊙ yr -1 , has a metallicity of ~1/4 solar and shows nebular emission from two components separated by 0.4 arcsec (in the image plane), possibly indicating a merger. It appears that foreground interstellar material within the galaxy has been evacuated from the sightline along which we observe the starburst, giving an unextinguished view of its stars and H II regions. CSWA 20, with its massive lensing galaxy producing a high magnification of an intrinsically luminous background galaxy, is a promising target for future studies at a variety of wavelengths.
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Cassowary 20 a wide separation einstein cross identified with the x shooter spectrograph
arXiv: Cosmology and Nongalactic Astrophysics, 2009Co-Authors: Max Pettini, L Christensen, S Dodorico, Wyn N Evans, V Belokurov, Paul C Hewett, S E Koposov, E Mason, J VernetAbstract:We have used spectra obtained with X-shooter, the triple arm optical-infrared spectrograph recently commissioned on the Very Large Telescope of the European Southern Observatory, to confirm the gravitational lens nature of the Cassowary candidate CSWA 20. This system consists of a luminous red galaxy at redshift z(abs) = 0.741, with a very high velocity dispersion sigma(lens) = 500 km/s, which lenses a blue star-forming galaxy at z(em) = 1.433 into four images with mean separation of about 6 arcseconds. The source shares many of its properties with those of UV-selected galaxies z = 2-3: it is forming stars at a rate of 25 solar masses per year, has a metallicity of about 1/4 solar, and shows nebular emission from two components separated by 0.4 arcseconds in the image plane, possibly indicating a merger. It appears that foreground interstellar material within the galaxy has been evacuated from the sight-line along which we observe the starburst, giving an unextinguished view of its stars and H II regions. CSWA 20, with its massive lensing galaxy producing a high magnification of an intrinsically luminous background galaxy, is a promising target for future studies at a variety of wavelengths.
David A Westcott - One of the best experts on this subject based on the ideXlab platform.
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Visual lures increase camera-trap detection of the southern Cassowary (Casuarius casuarius johnsonii)
Wildlife Research, 2017Co-Authors: Wren R. Mclean, David A WestcottAbstract:Context Monitoring is a key component in managing wildlife populations and is critical for revealing long-term population trends of endangered species. Cryptic or highly mobile species that occur in low densities and in remote terrain require the development of specific monitoring methods. The southern Cassowary is an Australian endangered species that poses many challenges for conducting population surveys. Aims The aims of the present study were to determine the effectiveness of camera traps in detecting cassowaries at a site, to determine whether visual lures increased detection rates, and to explore the potential of camera traps in population surveys. Methods Coloured lures (mimicking large blue and red fruit) were placed in front of a set of camera traps and compared with controls (no lures) at 29 survey sites on the Daintree coast, northern Queensland, Australia. Key results Camera traps with lures (1) detected more birds, (2) had a shorter detection latency, (3) had a marginally greater number of captures, (4) experienced a longer capture duration, (5) were more likely to have the Cassowary stop in front of the camera, and (6) achieved a 95% probability of detecting cassowaries in 12 trap days, compared with 28 trap days without lures. Conclusions An increase in the number of cassowaries detected, the reduction in camera latency times and the ability to identify the birds enables a more efficient approach to estimating population sizes over existing methods. This is the first published study to use visual lures to conduct camera trapping of birds. Implications The use of camera traps with lures is a practical and cost-efficient technique for the rapid detection of cassowaries at a site and lends itself to studies of population structure, size and trends.
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prioritising the protection of habitat utilised by southern cassowaries casuarius casuarius johnsonii
Endangered Species Research, 2012Co-Authors: Hamish A Campbell, Ross G Dwyer, Sean Fitzgibbons, Carissa J Klein, Graham Lauridsen, Adam Mckeown, Annebelle Olsson, Scott Sullivan, Matthew E Watts, David A WestcottAbstract:The southern Cassowary Casuarius casuarius johnsonii L. is an endangered flightless bird from northern Australia. The cassowaries' rainforest habitat has been extensively cleared, and the population primarily exists within discrete protected areas. They do, however, venture outside the reserves into modified landscapes, and it is here they are exposed to threatening pro- cesses. We used GPS-based telemetry and the adaptive local convex hull (a-LoCoH) non-paramet- ric kernel method to define the relationship between Cassowary home range (HR) and a protec- tion-area network. The study showed that: (1) females had a larger HR than males; (2) overlapping HR occurred between but not within the sexes; (3) HRs of the same sex partitioned along defined boundaries; and (4) the current protected areas only encompassed core HR for the inhabiting cas- sowaries. This information was incorporated within a spatial-conservation-prioritisation analysis to define the relative cost:benefit relationship for protecting the currently non-protected land utilised by the cassowaries. The results showed that the current reserve system may accommodate up to 24 adult cassowaries, only offering HR protection at the 40 to 60% a-LoCoH. This could be raised, relatively cheaply (1.2-fold the current costs), to 70% a-LoCoH for all birds by protecting adjacent forested areas on private land. Protection beyond the 70% a-LoCoH, however, required protection of large expanses of agricultural land, resulting in an exponential increase in monetary cost (5.1-fold). We argue that total HR protection for the cassowaries was an unfeasible conserva- tion option, but protection of core habitat was achieved relatively cheaply. Combining core HS protection with target incentives to landowners of adjacent cleared land may be the most cost- effective conservation strategy for C.c. johnsonii.
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Predation of Cassowary dispersed seeds: is the Cassowary an effective disperser?
Integrative zoology, 2011Co-Authors: Matt Bradford, David A WestcottAbstract:Post-dispersal predation is a potentially significant modifier of the distribution of recruiting plants and an often unmeasured determinant of the effectiveness of a frugivore's dispersal service. In the wet tropical forests of Australia and New Guinea, the Cassowary provides a large volume, long distance dispersal service incorporating beneficial gut processing; however, the resultant clumped deposition might expose seeds to elevated mortality. We examined the contribution of post-dispersal seed predation to Cassowary dispersal effectiveness by monitoring the fate of 11 species in southern Cassowary (Casuarius casuarius johnsonii Linnaeus) droppings over a period of 1 year. Across all species, the rate of predation and removal was relatively slow. After 1 month, 70% of seeds remained intact and outwardly viable, while the number fell to 38% after 1 year. The proportion of seeds remaining intact in droppings varied considerably between species: soft-seeded and large-seeded species were more likely to escape removal and predation. Importantly, across all species, seeds in droppings were no more likely to be predated than those left undispersed under the parent tree. We speculate that seed predating and scatter-hoarding rodents are responsible for the vast majority of predation and removal from droppings and that the few seeds which undergo secondary dispersal survive to germination. Our findings reinforce the conclusion that the Cassowary is an important seed disperser; however, dispersal effectiveness for particular plant species can be reduced by massive post-dispersal seed mortality.
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Consequences of southern Cassowary (Casuarius casuarius, L.) gut passage and deposition pattern on the germination of rainforest seeds
Austral Ecology, 2010Co-Authors: Matt Bradford, David A WestcottAbstract:In Australia's tropical rainforests the endangered southern Cassowary, Casuarius casuarius, L., is the largest native frugivore and many plant species, because of the size of their fruits or seeds, are thought to be largely dependent on cassowaries for their dispersal. In this study we asked whether the contribution of cassowaries to plant recruitment extends beyond removing seeds from the vicinity of the parent. To do this we conducted germination trials involving 17 rainforest plant species to test whether Cassowary consumption and seed deposition pattern alter germination probability or time to germination. Twenty-four per cent of species showed changed germination probabilities, with one species showing no germination without Cassowary consumption, and 35% showed changed time to germination. However these differences did not translate into any significant effects when considered across all species. We examined gut scarification, fruit pulp removal (de-inhibition) and deposition in faecal material as mechanisms for changing germination success; each contributed to the changed success of individual species. There was a negative effect of seed clumping on five species. We conclude that Cassowary consumption can modify germination performance in a minority of rainforest plants and that the effect is generally positive. Although the effect on large seeded species was small it is most likely to be important as the Cassowary is the only animal in Australia able to internally process large numbers of these seeds.
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Diet and Dietary Preferences of the Southern Cassowary (Casuarius casuarius) in North Queensland, Australia
Biotropica, 2008Co-Authors: Matt Bradford, A. J. Dennis, David A WestcottAbstract:We investigated the diet of the southern Cassowary (Casuarius casuarius) by identifying the seeds and fruits in fecal droppings encountered on a set of transects over 2 yr in upland rain forest in the wet tropics of North Queensland. A total of 198 droppings containing 56 plant species were found. We surveyed fleshy fruit availability over the subsequent 68 mo on transects in the same area to ascertain fruiting patterns in the study area. The number of droppings found each month did not correspond to the pattern of available fruit biomass. There was no relationship between the fruit traits of moisture content, flesh to seed mass ratio, color, or crop size to contribution of a species to the diet. During the lean fruiting season (May-July) cassowaries relied more on species that fruited continuously throughout the year as they were significantly over-represented in droppings, while annual fruiting species were under-represented. During months of high fruit availability (October-December), continuously fruiting species were still over-represented in the diet but became less important while annual and biennial species became more important. Significantly more species with large fruit and large seeds appeared in the diet than expected and we confirm that the Cassowary contributes to the continued dispersal of these species over long distances and in large quantities.
V Belokurov - One of the best experts on this subject based on the ideXlab platform.
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The evolution of late-type galaxies from Cassowary lensing systems
Monthly Notices of the Royal Astronomical Society, 2014Co-Authors: Z. Kostrzewa-rutkowska, Thomas E Collett, Matthew W Auger, Łukasz Wyrzykowski, V BelokurovAbstract:We explore the properties of lensing galaxies and lensed faint sources at redshifts between 1.5 and 3.0. Our sample consists of 9 carefully selected strongly-lensed galaxies discovered by the Cassowary survey in the Sloan Digital Sky Survey (SDSS) data. We find that, despite some limitations of the original SDSS data, the homogeneous sample of lensing systems can provide a useful insight into lens and source properties. We also explore the limitations of using low-resolution data to model and analyse galaxy-galaxy lensing. We derive the relative alignment of mass and light in fitted lens profiles. The range of magnification extends above 5, hence we are able to analyse potentially small and low-mass galaxies at high redshifts. We confirm the likely evolution of the size-luminosity relation for blue star-forming galaxies as a function of redshift
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constraining the dark energy equation of state with double source plane strong lenses
arXiv: Cosmology and Nongalactic Astrophysics, 2012Co-Authors: Thomas E Collett, Matthew W Auger, V Belokurov, P J Marshall, Alex HallAbstract:We investigate the possibility of constraining the dark energy equation of state by measuring the ratio of Einstein radii in a strong gravitational lens system with two source planes. This quantity is independent of the Hubble parameter and directly measures the growth of angular diameter distances as a function of redshift. We investigate the prospects for a single double source plane system and for a forecast population of systems discovered by re-observing a population of single source lenses already known from a photometrically selected catalogue such as Cassowary or from a spectroscopically selected catalogue such as SLACS. We find that constraints comparable to current data-sets (15% uncertainty on the dark equation of state at 68%CL) are possible with a handful of double source plane systems. We also find that the method's degeneracy between Omega_M and w is almost orthogonal to that of CMB and BAO measurements, making this method highly complimentary to current probes.
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modelling of the complex Cassowary slugs gravitational lenses
arXiv: Cosmology and Nongalactic Astrophysics, 2010Co-Authors: Brendon J Brewer, V Belokurov, Geraint F Lewis, Mike Irwin, Terry J Bridges, Wyn N EvansAbstract:We present the first high-resolution images of CSWA 31, a gravitational lens system observed as part of the SLUGS (Sloan Lenses Unravelled by Gemini Studies) program. These systems exhibit complex image structure with the potential to strongly constrain the mass distribution of the massive lens galaxies, as well as the complex morphology of the sources. In this paper, we describe the strategy used to reconstruct the unlensed source profile and the lens galaxy mass profiles. We introduce a prior distribution over multi-wavelength sources that is realistic as a representation of our knowledge about the surface brightness profiles of galaxies and groups of galaxies. To carry out the inference computationally, we use Diffusive Nested Sampling, an efficient variant of Nested Sampling that uses Markov Chain Monte Carlo (MCMC) to sample the complex posterior distributions and compute the normalising constant. We demonstrate the efficacy of this approach with the reconstruction of the group-group gravitational lens system CSWA 31, finding the source to be composed of five merging spiral galaxies magnified by a factor of 13.
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x shooter observations of the gravitational lens system Cassowary 5
Monthly Notices of the Royal Astronomical Society, 2010Co-Authors: V Belokurov, L Christensen, S Dodorico, Max Pettini, Wyn N Evans, M Kellogg, J VernetAbstract:We confirm an eighth gravitational lens system in the CAmbridge Sloan Survey Of Wide ARcs in the skY (Cassowary) catalogue. Exploratory observations with the X-shooter spectrograph on the Very Large Telescope of the European Southern Observatory show the system Cassowary 5 (CSWA 5) to consist of at least three images of a blue star-forming galaxy at z = 1.0686, lensed by an apparent foreground group of red galaxies, one of which is at z = 0.3877. The lensed galaxy exhibits a rich spectrum with broad interstellar absorption lines and a wealth of nebular emission lines. Preliminary analysis of these features shows the galaxy to be young, with an age of ~25-50 Myr. With a star formation rate of ~20 M ⊙ yr -1 , the galaxy has already assembled a stellar mass M * ~ 3 × 10 9 M ⊙ and reached half-solar metallicity. Its blue spectral energy distribution and Balmer line ratios suggest negligible internal dust extinction. A more in-depth analysis of the properties of this system is currently hampered by the lack of a viable lensing model. However, it is already clear that CSWA 5 shares many of its physical characteristics with the general population of UV-selected galaxies at redshifts z = 1-3, motivating further study of both the source and the foreground mass concentration responsible for the gravitational lensing.
J Vernet - One of the best experts on this subject based on the ideXlab platform.
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x shooter observations of the gravitational lens system Cassowary 5
Monthly Notices of the Royal Astronomical Society, 2010Co-Authors: V Belokurov, L Christensen, S Dodorico, Max Pettini, Wyn N Evans, M Kellogg, J VernetAbstract:We confirm an eighth gravitational lens system in the CAmbridge Sloan Survey Of Wide ARcs in the skY (Cassowary) catalogue. Exploratory observations with the X-shooter spectrograph on the Very Large Telescope of the European Southern Observatory show the system Cassowary 5 (CSWA 5) to consist of at least three images of a blue star-forming galaxy at z = 1.0686, lensed by an apparent foreground group of red galaxies, one of which is at z = 0.3877. The lensed galaxy exhibits a rich spectrum with broad interstellar absorption lines and a wealth of nebular emission lines. Preliminary analysis of these features shows the galaxy to be young, with an age of ~25-50 Myr. With a star formation rate of ~20 M ⊙ yr -1 , the galaxy has already assembled a stellar mass M * ~ 3 × 10 9 M ⊙ and reached half-solar metallicity. Its blue spectral energy distribution and Balmer line ratios suggest negligible internal dust extinction. A more in-depth analysis of the properties of this system is currently hampered by the lack of a viable lensing model. However, it is already clear that CSWA 5 shares many of its physical characteristics with the general population of UV-selected galaxies at redshifts z = 1-3, motivating further study of both the source and the foreground mass concentration responsible for the gravitational lensing.
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x shooter observations of the gravitational lens system Cassowary 5
arXiv: Cosmology and Nongalactic Astrophysics, 2010Co-Authors: L Christensen, S Dodorico, Max Pettini, Wyn N Evans, M Kellogg, V Belokurov, J VernetAbstract:We confirm an eighth gravitational lens system in the Cassowary catalogue. Exploratory observations with the X-shooter spectrograph on the VLT show the system CSWA5 to consist of at least three images of a blue star-forming galaxy at z = 1.0686, lensed by an apparent foreground group of red galaxies one of which is at z = 0.3877. The lensed galaxy exhibits a rich spectrum with broad interstellar absorption lines and a wealth of nebular emission lines. Preliminary analysis of these features shows the galaxy to be young, with an age of 25-50 Myr. With a star-formation rate of approximately 20 solar masses/yr, the galaxy has already assembled a stellar mass of 3 x 10^9 solar masses and reached half-solar metallicity. Its blue spectral energy distribution and Balmer line ratios suggest negligible internal dust extinction. A more in-depth analysis of the properties of this system is currently hampered by the lack of a viable lensing model. However, it is already clear that CSWA5 shares many of its physical characteristics with the general population of UV-selected galaxies at redshifts z = 1-3, motivating further study of both the source and the foreground mass concentration responsible for the gravitational lensing.
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Cassowary 20 a wide separation einstein cross identified with the x shooter spectrograph
arXiv: Cosmology and Nongalactic Astrophysics, 2009Co-Authors: Max Pettini, L Christensen, S Dodorico, Wyn N Evans, V Belokurov, Paul C Hewett, S E Koposov, E Mason, J VernetAbstract:We have used spectra obtained with X-shooter, the triple arm optical-infrared spectrograph recently commissioned on the Very Large Telescope of the European Southern Observatory, to confirm the gravitational lens nature of the Cassowary candidate CSWA 20. This system consists of a luminous red galaxy at redshift z(abs) = 0.741, with a very high velocity dispersion sigma(lens) = 500 km/s, which lenses a blue star-forming galaxy at z(em) = 1.433 into four images with mean separation of about 6 arcseconds. The source shares many of its properties with those of UV-selected galaxies z = 2-3: it is forming stars at a rate of 25 solar masses per year, has a metallicity of about 1/4 solar, and shows nebular emission from two components separated by 0.4 arcseconds in the image plane, possibly indicating a merger. It appears that foreground interstellar material within the galaxy has been evacuated from the sight-line along which we observe the starburst, giving an unextinguished view of its stars and H II regions. CSWA 20, with its massive lensing galaxy producing a high magnification of an intrinsically luminous background galaxy, is a promising target for future studies at a variety of wavelengths.
Hamish A Campbell - One of the best experts on this subject based on the ideXlab platform.
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Using citizen-collected wildlife sightings to predict traffic strike hot spots for threatened species: a case study on the southern Cassowary
Journal of Applied Ecology, 2016Co-Authors: Ross G Dwyer, Luke Carpenter‐bundhoo, Craig E Franklin, Hamish A CampbellAbstract:Assessing the causal factors underpinning the distribution and abundance of wildlife road-induced mortality can be challenging. This is particularly ubiquitous for rare or elusive species, because traffic strikes occur infrequently for these populations and information about localized abundance, distribution and movements are generally lacking. Here, we assessed whether citizen-collected sightings data may serve as a low cost and efficient means of gathering long-term animal roadside presence and road-crossing information, which could then be used to assess the causative factors and direct mitigation actions aimed at reducing wildlife traffic strike frequency. We explored this principle using two decades of traffic strike records and citizen-collected sightings of the southern Cassowary Casuarius casuarius johnsonii. Roads have bisected the cassowaries' rain forest habitat and despite considerable investment into mitigation strategies for this species, road-induced mortality is considered one of the primary threatening processes affecting the population. Using a Bayesian approach and controlling for spatial autocorrelation with conditional autoregressive models, we demonstrate that traffic strikes are primarily a density-dependent process in the southern Cassowary. That is, traffic strike clusters occurred along stretches of road where cassowaries were most frequently sighted. There were, however, road stretches where traffic strike frequency was greater than predicted by the number of roadside sightings, illustrating when and where density-independent processes increased the mortality potential for a road-crossing Cassowary.Synthesis and applications. This is the first time that citizen-collected sightings data have been used to systematically inform upon the abundance and distribution of wildlife traffic strike. The technique not only predicts where incidents are likely to occur but also helps us to understand the factors responsible for strike clustering. While not a replacement for systematic surveys, we highlight citizen-collected sightings data as a low-cost option when assessing contributing factors to vehicle-induced mortality. Accounting for density-dependent and density-independent processes will ensure the most effective allocation of resources when implementing wildlife traffic strike mitigation.
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chemical immobilisation and satellite tagging of free living southern cassowaries
Australian Veterinary Journal, 2014Co-Authors: Hamish A Campbell, Ross G Dwyer, Scott Sullivan, D Mead, Graham LauridsenAbstract:Background: The southern Cassowary (Casuarius casuarius johnsonii) attains 1.8m in height and over 80kg in weight. These large birds are equipped with large claws and, although not a direct threat to humans, they have caused serious injury to handlers and members of the public. Methods and results: This study describes chemical immobilisation, restraint, transport and post-monitoring (satellite tracking) methodologies for adult and juvenile southern cassowaries, captured and released from their natural environment. Conclusions: The described methods have improved the management and research opportunities for the southern Cassowary and may be transferable to other species of large ratite.
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prioritising the protection of habitat utilised by southern cassowaries casuarius casuarius johnsonii
Endangered Species Research, 2012Co-Authors: Hamish A Campbell, Ross G Dwyer, Sean Fitzgibbons, Carissa J Klein, Graham Lauridsen, Adam Mckeown, Annebelle Olsson, Scott Sullivan, Matthew E Watts, David A WestcottAbstract:The southern Cassowary Casuarius casuarius johnsonii L. is an endangered flightless bird from northern Australia. The cassowaries' rainforest habitat has been extensively cleared, and the population primarily exists within discrete protected areas. They do, however, venture outside the reserves into modified landscapes, and it is here they are exposed to threatening pro- cesses. We used GPS-based telemetry and the adaptive local convex hull (a-LoCoH) non-paramet- ric kernel method to define the relationship between Cassowary home range (HR) and a protec- tion-area network. The study showed that: (1) females had a larger HR than males; (2) overlapping HR occurred between but not within the sexes; (3) HRs of the same sex partitioned along defined boundaries; and (4) the current protected areas only encompassed core HR for the inhabiting cas- sowaries. This information was incorporated within a spatial-conservation-prioritisation analysis to define the relative cost:benefit relationship for protecting the currently non-protected land utilised by the cassowaries. The results showed that the current reserve system may accommodate up to 24 adult cassowaries, only offering HR protection at the 40 to 60% a-LoCoH. This could be raised, relatively cheaply (1.2-fold the current costs), to 70% a-LoCoH for all birds by protecting adjacent forested areas on private land. Protection beyond the 70% a-LoCoH, however, required protection of large expanses of agricultural land, resulting in an exponential increase in monetary cost (5.1-fold). We argue that total HR protection for the cassowaries was an unfeasible conserva- tion option, but protection of core habitat was achieved relatively cheaply. Combining core HS protection with target incentives to landowners of adjacent cleared land may be the most cost- effective conservation strategy for C.c. johnsonii.