We present the rest-frame optical and infrared colours of a complete sample of 1114 z < 0.3 galaxies from the Spitzer Wide-Area Infrared Extragalactic (SWIRE) Legacy Survey and the Sloan Digital Sky ...Survey (SDSS). We discuss the optical and infrared colours of our sample and analyse in detail the contribution of dusty star-forming galaxies and active galactic nuclei (AGN) to optically selected red sequence galaxies.
We propose that the optical (g−r) colour and infrared log(L
24/L
3.6) colour of galaxies in our sample are determined primarily by a bulge-to-disc ratio. The (g−r) colour is found to be sensitive to the bulge-to-disc ratio for disc-dominated galaxies, whereas the log(L
24/L
3.6) colour is more sensitive for bulge-dominated systems.
We identify ∼18 per cent (195 sources) of our sample as having red optical colours and infrared excess. Typically, the infrared luminosities of these galaxies are found to be at the high end of star-forming galaxies with blue optical colours. Using emission-line diagnostic diagrams, 78 are found to have an AGN contribution and 117 are identified as star-forming systems. The red (g−r) colour of the star-forming galaxies could be explained by extinction. However, their high optical luminosities cannot. We conclude that they have a significant bulge component.
The number densities of optically red star-forming galaxies are found to correspond to ∼13 per cent of the total number density of our sample. In addition, these systems contribute ∼13 per cent of the total optical luminosity density, and 28 per cent of the total infrared luminosity density of our SWIRE/SDSS sample. These objects may reduce the need for 'dry mergers'.
The western rock lobster (
Panurilus cygnus George.) is a conspicuous consumer in the coastal ecosystems of temperate Western Australia. We used stable isotope analysis and gut content analysis to ...determine the diet and trophic position of western rock lobsters from mid-shelf coastal ecosystems (35–60
m depth) at three locations. Lobsters were primarily carnivorous, and no consistent differences in diet were detected with varying lobster size, sex or among locations. The main components of the diet were bait (from the fishery) and small crustaceans – crabs and amphipods/isopods. Foliose red algae, bivalves/gastropods and sponges were minor contributors to diet. The diet of lobsters in deep coastal ecosystems differed from the results of previous studies of diets of lobsters from shallow coastal ecosystems. In particular, coralline algae and molluscs – important prey in studies of lobsters from shallow coastal ecosystems – were minor components of the diet. These differences are likely to reflect differences in food availability between these systems and potentially, differences in choice of prey by lobsters that inhabit deeper water. Given the high contribution of bait to lobster diet, bait is likely to be subsidizing lobster production in deep coastal ecosystems during the fishing season.
This paper is dedicated to the investigation of an important, but not particularly well known connection between the work of Hegel and Dewey's early educational ideas. A brief exposition of Hegel's ...position in thePhilosophy of Rightis offered, with a particular focus on Hegel's idea of absolute freedom. This exposition is followed by an analysis of one of Dewey's earliest books,Outlines of a Critical Theory of Ethics. Hegelian notions of absolute freedom are shown to be present in theOutlines, and textual evidence is then presented which links the theoretical framework of theOutlinesto Dewey's early educational thought.
Linear clearings, such as roads and tracks, are an obvious anthropogenic feature in many remote environments, even where infrastructure is sparse. Predator species have been shown to prefer moving ...down linear clearings, and therefore, clearings could increase predation risk for other species. We investigated whether tracks cleared for seismic surveys are preferentially used by predators and herbivores in a landscape inhabited by bilbies (Macrotis lagotis), a vulnerable species of conservation concern. We used a paired camera trap array to investigate the use of cleared seismic lines at four time points after clearing (1 month, 3 months, 7 months, 48 months) by six mammal species. Bilbies, cattle (Bos indicus/B. taurus), dingoes (Canis familiaris), feral cats (Felis catus) and agile wallabies (Macropus agilis) preferred to use seismic lines compared with adjacent undisturbed vegetation for almost all surveys, while spectacled hare wallabies (Lagorchestes conspicillatus) avoided them. Bilbies and agile wallabies showed similar temporal activity patterns on and off seismic lines but feral cats, dingoes and cattle used seismic lines at different times of day to control areas. We also investigated microhabitat selection by spool tracking individual bilbies. Bilbies selected a route through vegetation that was more open than surrounding vegetation. While spatial and temporal funnelling of bilbies and their predators (especially cats) may increase the frequency of encounter between the two, it is important to note that bilbies were active at significantly different times to predators both on and off seismic lines. The identified selection for seismic lines, and changes in spatial and temporal overlap between species, can be used to develop effective management strategies, to minimize potential impacts on native species.
In this essay, David Waddington and Noah Weeth Feinstein explore how Dewey's conception of science can help us rethink the way science is done in schools. The authors begin by contrasting a view of ...science that is implicitly accepted by many scientists and science educators — science as a search for truth — with Dewey's instrumentalist, technological, and nonrealist conception of science. After demonstrating that the search‐for‐truth conception is closely linked to some ongoing difficulties with science curricula that students find particularly alienating, they then analyze some of the educational opportunities that Dewey's vision opens up. Ultimately, Waddington and Weeth Feinstein argue that Dewey offers a humble and humanistic vision of science and science education practice that captures the power of science by connecting it clearly to everyday human activities and challenges.
The properties of Lyman break galaxies at z ∼ 5 Bremer, M. N.; Lehnert, M. D.; Waddington, I. ...
Monthly notices of the Royal Astronomical Society,
01/2004, Letnik:
347, Številka:
1
Journal Article
Recenzirano
In a recent paper, Lehnert & Bremer have photometrically selected a sample of Lyman break galaxies at z > 4.8 from a single VLT/FORS2 pointing and spectroscopically confirmed half of them to be at ...4.8 < z < 5.8. To study the properties of such galaxies further, we have photometrically selected a similar sample (VAB > 28, iAB < 26.3, iAB−zAB > 0) from the Hubble Space Telescope Advanced Camera for Surveys (HST ACS) images of the Chandra Deep Field-South. This selection results in a sample of 44 sources from ∼150 arcmin2. We find that such galaxies are often barely resolved in the ACS images, having half-light radii of 0.1–0.3 arcsec (<2 kpc). They show no difference in spatial clustering from sources selected by iAB < 26.3, iAB−zAB > 0, which are generally galaxies of lower redshift. However, their distribution over the field is not uniform and their surface density varies considerably over areas comparable to a single 8-m or HST pointing. A reliable determination of the surface and volume densities of such galaxies requires a sky area considerably larger than the current ACS imaging of this field. No individual Lyman break candidate was detected to a 3σ limit of 6 × 10−17 erg s−1 cm−2 at 0.5–5 keV by Chandra (a limiting luminosity of below 2 × 1043 erg s−1 at z∼ 5.3). By summing over all positions, we find that the mean source must be undetected at a level at least a factor of 4 times fainter than this. This rules out anything other than a weak active galactic nucleus (AGN) contribution to the emission from these objects; we conclude that luminous AGNs made little contribution to the final stages of re-ionization of the Universe.
Aims. By combining data from the VIMOS VLT Deep Survey (VVDS) with the Spitzer Wide-area InfraRed Extragalactic survey (SWIRE), we have built the currently largest spectroscopic sample of high ...redshift galaxies selected in the rest-frame near-infrared. We have obtained 2040 spectroscopic redshifts of galaxies with (m_) _{\rm AB} < 21.5 at 3.6 \mu m, and 1255 spectroscopic redshifts of galaxies with (m_) _{\rm AB} < 21. These allow us to investigate the clustering evolution of galaxies selected via their rest- frame near-infrared luminosity in the redshift range 0.2 < z < 2.1. Methods. We use the projected two-point correlation function w_{\rm p}(r_{\rm p}) to study the three dimensional clustering properties of galaxies detected at 3.6 \mu m and 4.5 \mu m with the InfraRed Array Camera (IRAC) in the SWIRE survey with measured spectroscopic redshifts from the first epoch VVDS. We compare these properties to those of a larger sample of 16672 SWIRE galaxies for which we have accurate photometric redshifts in the same field. Results. We find that in the 3.6 \mu m and 4.5 \mu m flux limited samples, the apparent correlation length does not change from redshift similar to 2 to the present. The measured correlation lengths have a mean value of r sub(0) \simeq 3.9\pm0.5 h super(-1) Mpc for the galaxies selected at 3.6 \mu m and a mean value of r sub(0) \simeq 4.4\pm0.5 h super(-1) Mpc for the galaxies selected at 4.5 \mu m, across the whole redshift range explored. These values are larger than those typicaly found for I-band selected galaxies at I_{\rm AB} < 24, for which r sub(0) varies from 2.69 h super(-1) Mpc to 3.63 h super(-1) Mpc between z = 0.5 to z = 2.1. We find that the difference in correlation length between I-band and 3.6-4.5 \mu m selected samples decreases with increasing redshift, becoming comparable at z \simeq 1.5. We interpret this as evidence that galaxies with older stellar populations and galaxies actively forming stars reside in comparably over-dense environments at epochs earlier than z \simeq 1.5, supporting the recently reported flattening of the color-density relation at high redshift. The increasing difference in correlation length with cosmic time observed between rest-frame UV-optical and near-infrared selected samples could then be an indication that star formation is gradually shifting to lower density regions with decreasing redshift, while the older, passively evolving galaxies remain in the most over-dense peaks.
Smale, D. A., Kendrick, G. A., Harvey, E. S., Langlois, T. J., Hovey, R. K., Van Niel, K. P., Waddington, K. I., Bellchambers, L. M., Pember, M. B., Babcock, R. C., Vanderklift, M. A., Thomson, D. ...P., Jakuba, M. V., Pizarro, O., and Williams, S. B. 2012. Regional-scale benthic monitoring for ecosystem-based fisheries management (EBFM) using an autonomous underwater vehicle (AUV). - ICES Journal of Marine Science, 69: 1108-1118.Monitoring marine habitats and biodiversity is critical for understanding ecological processes, conserving natural resources, and achieving ecosystem-based fisheries management (EBFM). Here, we describe the application of autonomous underwater vehicle (AUV) technology to conduct ongoing monitoring of benthic habitats at two key locations in Western Australia. Benthic assemblages on rocky reefs were sampled with an AUV, which captured >200 000 geo-referenced images. Surveys were designed to obtain 100% coverage of 25 25 m patches of benthic habitat. In 2010, multiple patches were surveyed at 15-40-m depths at three reference sites at the Houtman Abrolhos Islands and at six reference sites at Rottnest Island. The following year, repeat surveys of the same geo-referenced patches were conducted. Benthic assemblages at the Houtman Abrolhos Islands were varied in that one reference site was dominated by hard corals, whereas the other two were macroalgae dominated. Conversely, assemblages at Rottnest Island were dominated by the kelp Ecklonia radiata. The AUV resurveyed each patch with high precision and demonstrated adequate power to detect change. Repeated observations at the reference sites will track natural variability in benthic habitat structure, which in turn will facilitate the detection of ecological change and ultimately feed back into EBFM processes.
We investigate the clustering of galaxies selected in the 3.6 μm band of the Spitzer Wide‐area Infrared Extragalactic (SWIRE) legacy survey. The angular two‐point correlation function is calculated ...for 11 samples with flux limits of S3.6≥ 4–400 μJy, over an 8 deg2 field. The angular clustering strength is measured at >5σ significance at all flux limits, with amplitudes of A= (0.49–29) × 10−3 at 1°, for a power‐law model, Aθ−0.8. We estimate the redshift distributions of the samples using phenomological models, simulations and photometric redshifts, and so derive the spatial correlation lengths. We compare our results with the Galaxies In Cosmological Simulations (GalICS) models of galaxy evolution and with parametrized models of clustering evolution. The GalICS simulations are consistent with our angular correlation functions, but fail to match the spatial clustering inferred from the phenomological models or the photometric redshifts. We find that the uncertainties in the redshift distributions of our samples dominate the statistical errors in our estimates of the spatial clustering. At low redshifts (median z≤ 0.5), the comoving correlation length is approximately constant, r0= 6.1 ± 0.5 h−1 Mpc, and then decreases with increasing redshift to a value of 2.9 ± 0.3 h−1 Mpc for the faintest sample, for which the median redshift is z∼ 1. We suggest that this trend can be attributed to a decrease in the average galaxy and halo mass in the fainter flux‐limited samples, corresponding to changes in the relative numbers of early‐ and late‐type galaxies. However, we cannot rule out strong evolution of the correlation length over 0.5 < z < 1.
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