Adaptive optics near-infrared imaging of NGC 2992 – unveiling core structures related to radio figure-of-8 loops     

Scott C. Chapman  †  Simon L. Morris  Almudena Alonso-Herrero  Heino Falcke 《Monthly notices of the Royal Astronomical Society》2000,314(2):263-272

We present near-infrared adaptive optics, Very Large Array (VLA) radio and Hubble Space Telescope ( HST ) optical imaging of the nearby Seyfert galaxy NGC 2992. Spiral structure and an extension to the west are traced down to the core region at the limiting resolution of our near-infrared images. A faint, diffuse loop of near-infrared and radio emission is also observed to the north, embedded within the prominent 2-arcsec radio loop previously observed to the north-west. Near-infrared colour maps and CO narrow-band imaging are then used to identify which regions may not be purely reddened stellar populations. Our new data provide evidence that the VLA radio-loop morphology in the shape of a figure of 8 represents two components superimposed: (1) outflow bubbles out of the plane of the disc, coincident with the extended emission-line region (EELR); (2) star formation along the spiral arm within the galaxy disc and through the dust lane. The near-infrared continuum emission associated with the outflowing radio bubbles suggests that the radio loops are driven by the active nucleus.  相似文献   

Properties of hot stars in the Wolf--Rayet galaxy NGC 5253 from ISO-SWS spectroscopy     

Paul A. Crowther  S. C. Beck  Allan J. Willis  Peter S. Conti  Patrick W. Morris  Ralph S. Sutherland 《Monthly notices of the Royal Astronomical Society》1999,304(3):654-668

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Petrophysics and mineral exploration: a workflow for data analysis and a new interpretation framework     

Michael Dentith  Randolph J. Enkin  William Morris  Cameron Adams  Barry Bourne 《Geophysical Prospecting》2020,68(1):178-199

As mineral exploration seeks deeper targets, there will be a greater reliance on geophysical data and a better understanding of the geological meaning of the responses will be required, and this must be achieved with less geological control from drilling. Also, exploring based on the mineral system concept requires particular understanding of geophysical responses associated with altered rocks. Where petrophysical datasets of adequate sample size and measurement quality are available, physical properties show complex variations, reflecting the combined effects of various geological processes. Large datasets, analysed as populations, are required to understand the variations. We recommend the display of petrophysical data as frequency histograms because the nature of the data distribution is easily seen with this form of display. A petrophysical dataset commonly contains a combination of overlapping sub-populations, influenced by different geological factors. To understand the geological controls on physical properties in hard rock environments, it is necessary to analyse the petrophysical data not only in terms of the properties of different rock types. It is also necessary to consider the effects of processes such as alteration, weathering, metamorphism and strain, and variables such as porosity and stratigraphy. To address this complexity requires that much more supporting geological information be acquired than in current practice. The widespread availability of field portable instruments means quantitative geochemical and mineralogical data can now be readily acquired, making it unnecessary to rely primarily on categorical rock classification schemes. The petrophysical data can be combined with geochemical, petrological and mineralogical data to derive explanations for observed physical property variations based not only on rigorous rock classification methods, but also in combination with quantitative estimates of alteration and weathering. To understand how geological processes will affect different physical properties, it is useful to define three end-member forms of behaviour. Bulk behaviour depends on the physical properties of the dominant mineral components. Density and, to a lesser extent, seismic velocity show such behaviour. Grain and texture behaviour occur when minor components of the rock are the dominate controls on its physical properties. Grain size and shape control grain properties, and for texture properties the relative positions of these grains are also important. Magnetic and electrical properties behave in this fashion. Thinking in terms of how geological processes change the key characteristics of the major and minor mineralogical components allows the resulting changes in physical properties to be understood and anticipated.  相似文献   

A worldwide correlation for exponential bed particle size variation in subaerial aqueous flows     

P. H. Morris  D. J. Williams 《地球表面变化过程与地形》1999,24(9):835-847

The particle size of the bed sediments in or on many natural streams, alluvial fans, laboratory flumes, irrigation canals and mine waste deltas varies exponentially with distance along the stream. A plot of the available worldwide exponential bed particle size diminution coefficient data against stream length is presented which shows that all the data lie within a single narrow band extending over virtually the whole range of stream lengths and bed sediment particle sizes found on Earth. This correlation applies to both natural and artificial flows with both sand and gravel beds, irrespective of either the solids concentration or whether normal or reverse sorting occurs. This strongly suggests that there are common mechanisms underlying the exponential diminution of bed particles in subaerial aqueous flows of all kinds. Thus existing models of sorting and abrasion applicable to some such flows may be applicable to others. A comparison of exponential laboratory abrasion and field diminution coefficients suggests that abrasion is unlikely to be significant in gravel and sand bed streams shorter than about 10 km to 100 km, and about 500 km, respectively. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Hydrogeology of desert springs in the Panamint Range,California, USA: Geologic controls on the geochemical kinetics,flowpaths, and mean residence times of springs     

Carolyn L. Gleason  Marty D. Frisbee  Laura K. Rademacher  Donald W. Sada  Zachary P. Meyers  Jeffrey R. Knott  Brian P. Hedlund 《水文研究》2020,34(13):2923-2948

Over 180 springs emerge in the Panamint Range near Death Valley National Park, CA, yet, these springs have received very little hydrogeological attention despite their cultural, historical, and ecological importance. Here, we address the following questions: (1) which rock units support groundwater flow to springs in the Panamint Range, (2) what are the geochemical kinetics of these aquifers, and (3) and what are the residence times of these springs? All springs are at least partly supported by recharge in and flow through dolomitic units, namely, the Noonday Dolomite, Kingston Peak Formation, and Johnnie Formation. Thus, the geochemical composition of springs can largely be explained by dedolomitization: the dissolution of dolomite and gypsum with concurrent precipitation of calcite. However, interactions with hydrothermal deposits have likely influenced the geochemical composition of Thorndike Spring, Uppermost Spring, Hanaupah Canyon springs, and Trail Canyon springs. Faults are important controls on spring emergence. Seventeen of twenty-one sampled springs emerge at faults (13 emerge at low-angle detachment faults). On the eastern side of the Panamint Range, springs emerge where low-angle faults intersect nearly vertical Late Proterozoic, Cambrian, and Ordovician sedimentary units. These geologic units are not present on the western side of the Panamint Range. Instead, springs on the west side emerge where low-angle faults intersect Cenozoic breccias and fanglomerates. Mean residence times of springs range from 33 (±30) to 1,829 (±613) years. A total of 11 springs have relatively short mean residence times less than 500 years, whereas seven springs have mean residence times greater than 1,000 years. We infer that the Panamint Range springs are extremely vulnerable to climate change due to their dependence on local recharge, disconnection from regional groundwater flow (Death Valley Regional Flow System - DVRFS), and relatively short mean residence times as compared with springs that are supported by the DVRFS (e.g., springs in Ash Meadows National Wildlife Refuge). In fact, four springs were not flowing during this campaign, yet they were flowing in the 1990s and 2000s.  相似文献   

Can a photometric redshift code reliably determine dust extinction?     

T. S. R. Babbedge  R. Whitaker  S. Morris † 《Monthly notices of the Royal Astronomical Society》2005,361(2):437-450

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Galaxy groups at 0.3 ≤z≤ 0.55 – II. Evolution to z∼ 0     

D. J. Wilman †  M. L. Balogh ‡  R. G. Bower  J. S. Mulchaey  A. Oemler  Jr    R. G. Carlberg  V. R. Eke  I. Lewis  S. L. Morris  R. J. Whitaker 《Monthly notices of the Royal Astronomical Society》2005,358(1):88-100

We compare deep Magellan spectroscopy of 26 groups at  0.3 ≤ z ≤ 0.55  , selected from the Canadian Network for Observational Cosmology 2 field survey, with a large sample of nearby groups from the 2PIGG catalogue. We find that the fraction of group galaxies with significant [O  ii ]λ3727 emission (≥5 Å) increases strongly with redshift, from ∼29 per cent in 2dFGRS to ∼58 per cent in CNOC2, for all galaxies brighter than  ∼ M _*+ 1.75  . This trend is parallel to the evolution of field galaxies, where the equivalent fraction of emission-line galaxies increases from ∼53 to ∼75 per cent. The fraction of emission-line galaxies in groups is lower than in the field, across the full redshift range, indicating that the history of star formation in groups is influenced by their environment. We show that the evolution required to explain the data is inconsistent with a quiescent model of galaxy evolution; instead, discrete events in which galaxies cease forming stars (truncation events) are required. We constrain the probability of truncation ( P _trunc) and find that a high value is required in a simple evolutionary scenario neglecting galaxy mergers  ( P _trunc≳ 0.3 Gyr⁻¹)  . However, without assuming significant density evolution, P _trunc is not required to be larger in groups than in the field, suggesting that the environmental dependence of star formation was embedded at redshifts   z ≳ 0.45  .  相似文献   

Development of immunological procedures for the study of mercury-binding proteins of Mytilus edulis     

G. Roesijadi  J.E. Morris 《Marine environmental research》1984,14(1-4)

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Comparison of the structures of humic acids from marine sediments and degraded field diatoms by 13C- and 1H-NMR spectroscopy     

E.-L. Poutanen  R.J. Morris 《Marine Chemistry》1985,17(2):115-126

Humic acids isolated from marine sediments of the Peru continental shelf and from a degraded field diatom population dominated by the diatoms Skeletonema costatum, Nitzschia seviata and Thalassiosira sp. were characterized on the basis of infrared spectra and ¹³C- and proton-NMR spectra. Aliphatic structures were found to constitute the major fraction of humic acids and they appear to be highly branched. Carbohydrates and to a lesser extent aromatic materials, carbonyl-, ether-, alcohol- and amino groups are important contributors to the structure of marine humic acids. A close relationship was observed between the chemical structure of the sedimentary humic acid and the plankton humic acid.  相似文献   

The effect of low temperature on Antarctic endolithic green algae     

Meyer MA  Huang G-H  Morris GJ  Friedmann EI 《Polarforschung》1988,58(2-3):113-119

Laboratory experiments show that undercooling to about -5 degrees C occurs in colonized Beacon sandstones of the Ross Desert, Antarctica. High-frequency temperature oscillations between 5 degrees C and -5 degrees C or -10 degrees C (which occur in nature on the rock surface) did not damage Hemichloris antarctica. In a cryomicroscope, H. antarctica appeared to be undamaged after slow or rapid cooling to -50 degrees C. 14CO2 incorporation after freezing to -20 degrees C was unaffected in H. antarctica or in Trebouxia sp. but slightly depressed in Stichococcus sp. (isolated from a less extreme Antarctic habitat). These results suggest that the freezing regime in the Antarctic desert is not injurious to endolithic algae. It is likely that the freezing-point depression inside the rock makes available liquid water for metabolic activity at subzero temperatures. Freezing may occur more frequently on the rock surface and contribute to the abiotic nature of the surface.  相似文献