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601.
R. Auld R. F. Minchin J. I. Davies B. Catinella W. van Driel P. A. Henning S. Linder E. Momjian E. Muller K. O'Neil S. Sabatini S. Schneider G. Bothun L. Cortese M. Disney G. L. Hoffman M. Putman J. L. Rosenberg M. Baes W. J. G. de Blok A. Boselli E. Brinks N. Brosch J. Irwin I. D. Karachentsev V. A. Kilborn B. Koribalski K. Spekkens † 《Monthly notices of the Royal Astronomical Society》2006,371(4):1617-1640
602.
Dominique Bockelée-Morvan Nicolas Biver Pierre Colom Florence Henry John K. Davies Harold A. Weaver 《Icarus》2004,167(1):113-128
Radio spectroscopic observations of Comet 19P/Borrelly were performed during the 1994 apparition and at, and near, the time of the Deep Space 1 flyby in 2001. HCN, CS, CH3OH, and H2CO were detected using the 30-m telescope of the Institut de Radioastronomie Millimétrique and the James Clerk Maxwell Telescope, and their production rates relative to water are estimated to be 0.06-0.11, 0.07, 1.7, and 0.4%, respectively. Only upper limits are derived for H2S and CO. The upper limit for CO/H2O (<15%) is not very constraining, while the upper limit for the H2S/H2O ratio of 0.45% is near the bottom of the range of values measured for other comets. Observations of the OH radical at the Nançay radio telescope provide water production rates a few weeks before the 1994 and 2001 perihelia. Observations of the 110-101 water line at 557 GHz with the Odin satellite yield a water production rate of (2.5±0.5)×1028 s−1 on September 22, 2001, at the time of the Deep Space 1 encounter, and (3.3±0.6)×1028 s−1 averaged over the September 22-24, 2001 period. The line shapes are asymmetric and blueshifted by V0∼−0.18 km s−1 for the best observed HCN lines recorded one week after perihelion. The HCN line shapes, and the similar OH and HCN velocity shifts over the September-November 1994 and August-September 2001 periods, favor anisotropic outgassing towards the Sun. Strong outgassing directed along the primary dust jet seen on visible images is not excluded by the HCN line shapes, but unrealistically high gas expansion velocities are required to explain the line shapes in that case. 相似文献
603.
Richard M. McDermid Roland Bacon Harald Kuntschner Eric Emsellem Kristen L. Shapiro Martin Bureau Michele Cappellari Roger L. Davies Jesús Falcn-Barroso Davor Krajnovi Reynier F. Peletier Marc Sarzi Tim de Zeeuw 《New Astronomy Reviews》2006,49(10-12):521
We summarise the results and achievements of integral-field spectroscopy of early-type galaxies, observed as part of a survey using both the SAURON and OASIS spectrographs. From the perspective of integral-field spectroscopy, these otherwise smooth and featureless objects show a wealth of structure, both in their stellar kinematics and populations. We focus on the stellar content, and examine properties on both kiloparsec scales with SAURON, and scales of 100’s of parsecs with OASIS. These complementary studies reveal two types of kinematically distinct components (KDCs), differing primarily in their intrinsic sizes. In previous studies, KDCs and their host galaxies have generally been found to be unremarkable in other aspects. We show that large KDCs, typical of the well-studied cases, indeed show little or no age differences with their host galaxy. The KDCs detected with the higher spatial-resolution of OASIS are intrinsically smaller and include, in contrast, a significant fraction of young stars. We speculate on the relationship between KDCs and their host galaxies, and the implications for young populations in early-type galaxies. 相似文献
604.
Report of the IAU/IAG/COSPAR Working Group on Cartographic Coordinates and Rotational Elements of the Planets and Satellites: 1985 总被引:1,自引:1,他引:0
605.
Andrew J. Westphal Christopher Snead Anna Butterworth Giles A. Graham John P. Bradley Saa Bajt Patrick G. Grant Graham Bench Sean Brennan Piero Pianetta 《Meteoritics & planetary science》2004,39(8):1375-1386
Abstract— In January 2006, the Stardust mission will return the first samples from a solid solar system body beyond the Moon and the first samples of contemporary interstellar dust ever collected. Although sophisticated laboratory instruments exist for the analysis of Stardust samples, techniques for the recovery of particles and particle residues from aerogel collectors remain primitive. Here, we describe our recent progress in developing techniques for extracting small volumes of aerogel, which we have called “keystones,” which completely contain particle impacts but minimize the damage to the surrounding aerogel collector. These keystones can be fixed to custom‐designed micromachined silicon fixtures (so called “microforklifts”). In this configuration, the samples are self‐supporting, which can be advantageous in situations where interference from a supporting substrate is undesirable. The keystones may also be extracted and placed onto a substrate without a fixture. We have also demonstrated the capability of homologously crushing these unmounted keystones for analysis techniques that demand flat samples. 相似文献
606.
607.
Thomas Stephan Anna L. Butterworth Friedrich Hrz Christopher J. Snead Andrew J. Westphal 《Meteoritics & planetary science》2006,41(2):211-216
Abstract— Powdered Allende projectiles were fired into silica aerogel at 6.1 km/sec in order to evaluate particle retrieval and analysis techniques for samples from the Stardust mission. Since particles may disintegrate and ablate along the penetration paths in a high‐porosity aerogel, TOF‐SIMS analysis may be a suitable method to determine the distribution of such materials along the tracks as well as potential compositional modifications. Therefore, two ?350 μm‐sized tracks, residing at the surface of a keystone specimen that was flattened between two silicon chips, were analyzed. TOF‐SIMS allows for a detailed study of the chemical composition of particles that survived the impact mostly intact and of fine‐grained material from disintegrated projectiles. In the investigated keystone, material from light gas gun debris dominated. Besides the two tracks, a continuous, 40‐μm‐thick surface layer of implanted material—probably gun residue—was found. One of the two analyzed tracks is compositionally distinct from this surface layer and is likely to contain residual material of an Allende projectile. The analyses clearly demonstrate that tracks, resulting from impactors in the 5–10 μm size range, can be successfully analyzed with TOF‐SIMS. 相似文献
608.
609.
Anna Curir 《Astrophysics and Space Science》2006,306(3):99-112
The peculiar ring galaxies are formed as a result of a cosmic interaction. An intruder galaxy plunges through the center of
a rotating disk galaxy triggering radially expanding density waves inside the disk. In this paper we exploited SPH simulations
with the aim to examine the role of a “live” halo and/or bulge in driving the morphology of the interacting galaxy. Moreover
we explore the effects of different implementations of the shear viscosity and of the pressure gradient in the code. 相似文献
610.
The late‐glacial Bølling period was first identified by Johs. Iversen on the basis of pollen results from Lake Bølling Sø in Denmark. Because there were no radiocarbon dates from the sequence the Bølling Chronozone (12 000–13 000 14C yr BP) was later established on the basis of dates from other sites. A new project is reinvestigating the sediments from the Bølling Sø sequence with AMS radiocarbon dating and multiproxy analyses. Here we present results of AMS radiocarbon dating, macrofossil analyses, cladoceran analyses (Cladocera concentrations and chydorid ephippia) and Pediastrum analyses (concentrations). The AMS dates on land plant remains show that the lower part of the sequence is around 12 500 14C yr BP, and thus clearly pre‐dates the Allerød chronozone. However, construction of a chronology for the sequence was problematic, partly because of reworking of macroscopic plant remains. The climate ameliorated after glacial conditions to such an extent that growth of plants could begin at ca. 12 500 14C yr BP, but the results of multiproxy analyses show little evidence for a further warming period during the pre‐Allerød part of the sequence. Lake productivity was low, and tree birch rare or maybe absent. This may reflect widespread occurrence of dead ice, unstable soils, heavy in‐wash of minerogenic matter to the lake, resulting in turbid water and rapid sedimentation. The early pioneer vegetation was characterised by Salix polaris and Dryas octopetala, and by herbs. The Allerød Chronozone, and especially its initial part, appears to have been relatively warm but reduced cladoceran concentrations and increased proportion of chydorid ephippia suggest that climate cooled in the middle Allerød and that the late Allerød was colder than the early part. The early Younger Dryas was probably colder than the late Younger Dryas. Clear warming is apparent at the beginning of the Holocene, where the first macrofossil evidence of trees (Betula pubescens, Populus tremula) is found. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献