Mode identification in the δ Scuti Star 1 Mon     

L. A. Balona  B. Bartlett  †  J. A. R. Caldwell  J. Gaobakwe  †  G. Handler  P. Kalebwe  †  K. Khoabane  †  C. Koen  D. Laney  T. Medupe  J. Menzies  M. Msikinya  †  M. Phillips †  T. Sono † 《Monthly notices of the Royal Astronomical Society》2001,321(2):239-246

We present new multicolour photometry and simultaneous high-dispersion spectroscopy for the δ Scuti star 1 Mon. The two main periodicities in the star are still present, but the third known period is not directly detected in the new radial velocities or light variations. However, it is detected in the periodogram of the second moment of the line profile variations. We use the cross-correlation function as an approximation for the line profile variations. By computing theoretical profiles for a given mode and comparing them with phased cross-correlation profiles, we are able to determine a goodness-of-fit criterion and estimate the most probable spherical harmonic degree,     the azimuthal order, m , of the pulsation and also the angle of inclination. We then compare the relative amplitudes and phases of the photometric variations in five wavebands and obtain the best estimates of     for the two visible periodicities. We confirm the earlier determinations that the main periodicity is a radial mode and that the other periodicity is probably         We show that the line profile variations and light variations give consistent results. We point out the importance of a long wavelength range when using the photometric mode identification technique. Finally, we attempt to match the two periods with unstable modes from linear, non-adiabatic calculations. We are able to show that the principal period is well matched by either the fundamental or first overtone radial mode, but could not find a satisfactory fit to the     mode. We discuss implications for mode identification of δ Scuti stars based on what we have learned from this star.  相似文献   

The colour–magnitude relation for galaxies in the Coma cluster     

A.I. Terlevich  N. Caldwell  R.G. Bower 《Monthly notices of the Royal Astronomical Society》2001,326(4):1547-1562

We present a new photometric catalogue of the Coma galaxy cluster in the Johnson U and V bands. We cover an area of 3360 arcmin² of sky, to a depth of     in a 13-arcsec diameter aperture, and produce magnitudes for ∼1400 extended objects in metric apertures from 8.8- to 26-arcsec diameters. The mean internal rms scatter in the photometry is 0.014 mag in V , and 0.026 mag in U , for     .
We place new limits on the levels of scatter in the colour–magnitude relation (CMR) in the Coma cluster, and investigate how the slope and scatter of the CMR depend on galaxy morphology, luminosity and position within the cluster. As expected, the lowest levels of scatter are found in the elliptical galaxies, while the late-type galaxies have the highest numbers of galaxies bluewards of the CMR. We investigate whether the slope of the CMR is an artefact of colour gradients within galaxies, and show that it persists when the colours are measured within a diameter that scales with galaxy size. Looking at the environmental dependence of the CMR, we find a trend of systematically bluer galaxy colours with increasing projected radius from the centre of the cluster. Surprisingly, this is accompanied by a decreased scatter of the CMR. We investigate whether this gradient could be caused by dust in the cluster potential, however the reddening required would produce too large a scatter in the colours of the central galaxies. The gradient appears to be better reproduced by a gradient in the mean galactic ages with projected radius.  相似文献   

Cosmological weak lensing with the HST GEMS survey     

Catherine Heymans  Michael L. Brown  Marco Barden  John A. R. Caldwell  Knud Jahnke  Chien Y. Peng  Hans-Walter Rix  y Taylor  Steven V. W. Beckwith  Eric F. Bell  rea Borch  Boris Häußler  Shardha Jogee  Daniel H. McIntosh  Klaus Meisenheimer  Sebastian F. Sánchez  Rachel Somerville  Lutz Wisotzki  Christian Wolf 《Monthly notices of the Royal Astronomical Society》2005,361(1):160-176

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Determinable and non-determinable parameters of galvanic distortion in magnetotellurics   总被引：3，自引：0，他引：3  

H. M. Bibby  T. G. Caldwell  C. Brown 《Geophysical Journal International》2005,163(3):915-930

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The American public’s preference for preparation for the possible effects of global warming: impact of communication strategies     

Bo MacInnis  Jon A. Krosnick  Adina Abeles  Margaret R. Caldwell  Erin Prahler  Debbie Drake Dunne 《Climatic change》2015,128(1-2):17-33

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Colour–magnitude relations and spectral line strengths in the Coma cluster     

A. I. Terlevich  Harald Kuntschner  R. G. Bower  N. Caldwell  R. M. Sharples 《Monthly notices of the Royal Astronomical Society》1999,310(2):445-452

We use the C₂4668, Fe4383, H γ _A and H δ _A spectral absorption line indices, together with U - and V -band photometry of 101 galaxies in the Coma cluster, to investigate how mean age and metal abundance correlate with galaxy luminosity. In particular, we use the line index measurements to address the origin of the colour–magnitude relation (CMR). We find that the CMR in Coma is driven primarily by a luminosity–metallicity correlation. We additionally show evidence for a relation between age and luminosity, in the direction predicted by the semi-analytic hierarchical clustering models of Kauffmann & Charlot, but this is only present in the C₂4668 index models, and could be an effect of the lack of non-solar abundance ratios in the Worthey models used.
By comparing deviations from the CMR with deviations in absorption index from analogous 'index–magnitude' relations, we find that colour deviations bluewards of the mean relation are strongly correlated with the hydrogen Balmer line series absorption. We show that the properties of these blue galaxies are consistent with the presence of a young stellar population in the galaxies, rather than with a reduced metallicity.  相似文献   

Latitudinal variations in Jovian stratospheric temperature     

R.D. Cess  Barbara E. Carlson  John Caldwell  I.G. Nolt  F.C. Gillett  A.T. Tokunaga 《Icarus》1981,46(2):249-255

Ground-based observations of Jupiter show that the planet's stratospheric and tropospheric thermal emission are anticorrelated. The observations can possibly be explained by latitudinal variations in cloud altitude. These variations cause differential stratospheric heating by sunlight which is reflected off the clouds and then absorbed within the stratosphere by visible and near-infrared bands of methane.  相似文献   

Infrared polar brightening on Jupiter: III. Spectrometry from the Voyager 1 IRIS experiment     

Sang J. Kim  John Caldwell  A.R. Rivolo  R. Wagener  Glenn S. Orton 《Icarus》1985,64(2):233-248

Spectra from the Voyager 1 IRIS experiment confirm the existence of enhanced infrared emission near Jupiter's north magnetic pole in March 1979. The spectral characteristics of the enhanced emission are consistent with a Planck source function. A temperature-pressure profile is derived for the region near the north magnetic pole, from which quantitative abundance estimates of minor species are made. Some species previously detected on Jupiter, including CH₃D, C₂H₂ and C₂H₆, have been observed again near the pole. Newly discovered species, not previously observed on Jupiter, include C₂H₄, C₃H₄, and C₆H₆. All of these species except CH₃D appear to have enhanced abundances at the north polar region with respect to midlatitudes. Upper limits are determined for C₄H₂ and C₃H₈. The quantitative results are compared with model calculations based on ultraviolet results from the IUE satellite. The plausibility of the C₆H₆ identification in discussed in terms of the literature on C₂H₂ polymerization. The relation of C₆H₆ to cuprene is also discussed.  相似文献   

The effect of oil pollution on the reproduction and feeding behaviour of the sea anemone Actinia equina     

R.F.G Ormond  S Caldwell 《Marine pollution bulletin》1982,13(4):118-122

The effects of oil pollution on the sea anemone Actinia equina were investigated. Chronic pollution with 2.5 ml.l^?1 crude oil resulted, for about seven weeks, in ejection of increased numbers of the young which are normally brooded within the gastric cavity. Subsequently the numbers of surviving young being produced fell to zero, and the ovaries were found to be regressed and lacking ova. The anemones were also more frequently observed with tentacles expanded and mouth open, but the response to food offered to the tentacles was slow or absent. In separate tests it was found that crude oil presented on filter paper to the anemones could act as a feeding inducer, but that it interfered with or diluted the action of natural feeding inducers present in fish muscle extract. These effects are comparable with those which oil pollution has been found by other workers to have upon other anthozoans—the corals.  相似文献   

An inversion in the atmosphere of Titan     

R.E. Danielson  John J. Caldwell  D.R. Larach 《Icarus》1973,20(4):437-443

It is proposed that a large temperature inversion exists in the atmosphere of Titan due to absorption of solar radiation by small “dust” particles. A very simplified preliminary analysis indicates that this inversion model can expain the high infrared brightness temperatures in the absence of a greenhouse effect.  相似文献