排序方式： 共有20条查询结果，搜索用时 78 毫秒
1.
Julia Scharwächter Andreas Eckart Susanne Pfalzner Johannes Staguhn Eva Schinnerer 《Astrophysics and Space Science》2003,284(2):507-510
We address current theories of research on morphology, environment and evolution of active galaxies in the form of a detailed
case study of the nearby QSO host I Zw 1. This study is based on sub-kpc resolution 12CO(1-0) observations with the BIMA mm-interferometer and on near-infrared imaging with ISAAC at the VLT. The 12CO(1-0) maps reveal a circumnuclear molecular gas ring with a radius of 0.9 kpc. The imaging data in the J-band are analyzed
with respect to a disk-bulge decomposition. Together with a model of the gas rotation curve, the radial profile of the dynamical
J-band mass-to-light ratio (M/L) is discussed. The J-band images give new evidence for an interaction between I Zw 1 and its
nearby companion. First results from a sequence of N-body simulations for an extensive test of the parameter space of the
interaction are presented.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
S.?PetitEmail author A.?Decarreau F.?Martin R.?Buchet 《Physics and Chemistry of Minerals》2004,31(9):585-592
The aim of this paper is to determine a relationship between the wavenumbers of the first OH-stretching overtones (W2OH) and the wavenumbers of the OH-stretching fundamentals (WOH) to help to interpret the near-infrared (NIR) spectra. The first overtone (2OH) bands appear at wavenumbers less than twice those of the fundamental bands (OH), due to the anharmonic character of vibrations, X = W2OH/2 - WOH, with X being the anharmonicity constant. Talc samples with various crystal chemistries are used to solve the equation and the experimental data are well fitted with X = –85.6 cm–1. As far as the authors are aware, it is the first time that the anharmonicity constant for the OH-stretching vibrations is determined for phyllosilicates. The anharmonicity constant remains almost unchanged for several types of clay samples. Therefore the relation, established from talc samples because their absorption bands are narrow and their wavenumber range of OH vibrations is wide, can be used for any other clay minerals. 相似文献
3.
福建政和东际金-银矿床的热液蚀变特征及其勘探指示意义 总被引：2，自引：0，他引：2
福建东际金-银矿床产于中生代东坑火山岩盆地西缘的流纹质凝灰岩中,矿区及周边火山-沉积岩系遭受了广泛且强度不等的热液蚀变。本文工作采用红外反射光谱技术在东际矿区三个勘探剖面上对钻孔岩心进行系统性高密度采样分析,结果显示蚀变矿物组合及分带的大框架样式主要受原岩成分控制,具体表现为绢云母化趋向于发育于流纹质火山岩中,而绿泥石化则富集在安山质和英安质火山岩中。在更小的矿区局部空间范围内或单一岩性中,热液作用的物化条件作为次级控制因素决定着特定蚀变矿物的成分变化和蚀变类型的强度差异。从层状硅酸盐组合考虑,东际矿区热液蚀变以绢云母化和绿泥石化为最主要类型,而缺失发育良好的蒙脱石带,金-银矿化赋存在以伊利石为主的绢云母化带中,表明成矿环境属于低硫到中硫之间的浅成热液系统。含矿火山岩的热液蚀变组合和强度变化,以及金-银矿化的似层状特点,均指示成矿时流体是沿着南园组凝灰岩层内侧向流动,而蚀变分带细节显示在凝灰岩层中存在着二至三条流体主通道,金-银矿化则赋存在主通道中。流体主通道的热液蚀变标志是富铝绢云母,其与主通道之外的相对贫铝绢云母在红外光谱特征上反差明显。因此,采用红外光谱技术圈定整体热液蚀变系统的空间构型、解译成矿环境的物化条件及变化、并确定绢云母的铝含量变化用以判断成矿流体主通道位置,可以有效地缩小勘探目标和提高找矿工作的预测性。 相似文献
4.
This study tests the hypothesis that Fourier-transform infrared spectroscopy (FTIRS) of lake sediments can be used to infer
past changes in tree-line position and total organic carbon (TOC) content of lake water. A training set of 100 lakes from
northern Sweden spanning a broad altitudinal and TOC gradient from 0.7 to 14.9 mg/l was used to assess whether vegetation
zones and TOC can be modelled from FTIR spectra of surface sediments (0–1 cm) using principal component analysis (PCA) and
partial least squares (PLS) regression. Preliminary results show that FTIRS of lake sediments can be used to reconstruct past
changes in tree line and the TOC content of lake water, which is hardly surprising since FTIRS registers the properties of
organic and minerogenic material derived from the water mass and the drainage area. The FTIRS model for TOC gives a root mean
squared error (RMSECV) of calibration of 1.4 mg/l (10% of the gradient) assessed by internal cross-validation (CV) yielding
an Rcv2 of 0.64. This should be compared with a near-infrared spectroscopy (NIRS) and diatom transfer function for TOC from the same
set of lakes, which have a Rcv2 of 0.61 and 0.31, and RMSECV of 1.6 and 2.3 mg/l, respectively. The FTIRS-TOC model was applied to a Holocene sediment core
from a tree-line lake and the results show similar trends as inferences from NIRS and pollen from the same core. Overall,
the results indicate that changes in FTIR spectra from lake sediments reflect differences in catchment vegetation and TOC,
and that FTIRS-models based on surface-sediment samples can be applied to sediment cores for retrospective analysis. 相似文献
5.
Data with the 2MASS prototype camera were obtained in a 2.3 sq. deg region in Taurus containing Heiles Cloud 2, a region known from IRAS observations to contain a number of very young solar type stars. Data at 1.25 (J), 1.65 (H), and 2.2 (K
s
)µm are presented. These data are representative of the type and quality of data expected from the planned near-IR surveys, 2MASS and DENIS. Near-IR surveys will be useful for determining the large scale variation of extinction with clouds, for determining the luminosity function in nearby clouds down to ranges of 0.1–1.0 L, and for finding highly extincted T Tauri stars missed by IRAS because the bulk of their luminosity is emitted shortward of 12µm. 相似文献
6.
Transneptunian objects and Centaurs are supposed to be among the most pristine bodies of the Solar System. To investigate their physical properties and their surface composition, an ESO large program at the Very Large Telescope was carried out. In this paper we present photometric and spectroscopic near-infrared data of two Centaurs (1998 SG35 and 2000 QC243) and one transneptunian object (47171 1999 TC36). For 47171 1999 TC36 and 1998 SG35 visible photometry is also presented. Models of the surface composition of these objects are presented and discussed. By including a small percentage of water ice in our geographical mixtures, we obtain a better agreement with the observations in the H and K bands. 相似文献
7.
Near-infrared observations of Europa's disk-integrated opposition surge by Cassini VIMS, first published in Fig. 4 of Brown et al. (2003, Icarus, 164, 461), have now been modeled with the commonly used Hapke photometric function. The VIMS data set emphasizes observations at 16 solar phase angles from 0.4° to 0.6°—the first time the <1° phase “heart” of Europa's opposition surge has been observed this well in the near-IR. This data set also provides a unique opportunity to examine how the surge is affected by changes in wavelength and albedo: at VIMS wavelengths of 0.91, 1.73, and 2.25 μm, the geometric albedo of Europa is 0.81, 0.33, and 0.18, respectively. Despite this factor-of-four albedo range, however, the slope of Europa's phase curve at <1° phase is similar at all three wavelengths (to within the error bars) and this common slope is similar to the phase coefficient seen in visible-light observations of Europa. The two components of the opposition surge—involving different models of the physical cause of the surge—are the Shadow Hiding Opposition Effect (SHOE) and the Coherent Backscatter Opposition Effect (CBOE). Because of sparse VIMS phase coverage, it is not possible to constrain all the surge parameters at once in a Hapke function that has both SHOE and CBOE; accordingly, we performed separate Hapke fits for SHOE-only and CBOE-only surges. At 2.25 μm, where VIMS data are somewhat noisy, both types of surges can mimic the slope of the VIMS phase curve at <1° phase. At 0.91 and 1.73 μm, however—where VIMS data are “cleaner”—CBOE does a noticeably poorer job than SHOE of matching the VIMS phase coefficient at <1° phase; in particular, the best CBOE fit insists on having a steeper phase-curve slope than the data. This discrepancy suggests that Europa's near-IR opposition surge cannot be explained by CBOE alone and must have a significant SHOE component, even at wavelengths where Europa is bright. 相似文献
8.
10199 Chariklo (1997 CU26) is the largest Centaur so far known. We carried out near-infrared observations of this object during two different runs separated by a year. Although no evidence for spectral variations has been found over short time scales, slight differences have been detected between the two observational runs. We interpret these findings as likely due to a heterogeneous composition of the surface of Chariklo. We suggest two different models comprising geographical mixtures of tholins, amorphous carbon, and water ice in slightly different percentages. Our observations confirm the presence of water ice on the surface of this Centaur, as already detected by Brown et al. (1998, Science 280, 1430-1432) and Brown and Koresko (1998, Astrophys. J. 505, L65-67). 相似文献
9.
The European SMART-1 mission to the Moon, primarily a testbed for innovative technologies, was launched in September 2003 and will reach the Moon in 2005. On board are several scientific instruments, including the point-spectrometer SMART-1 Infrared Spectrometer (SIR). Taking into account the capabilities of the SMART-1 mission and the SIR instrument in particular, as well as the open questions in lunar science, a selection of targets for SIR observations has been compiled. SIR can address at least five topics: (1) Surface/regolith processes; (2) Lunar volcanism; (3) Lunar crust structure; (4) Search for spectral signatures of ices at the lunar poles; and (5) Ground truth and study of geometric effects on the spectral shape. For each topic we will discuss specific observation modes, necessary to achieve our scientific goals. The majority of SIR targets will be observed in the nadir-tracking mode. More than 100 targets, which require off-nadir pointing and off-nadir tracking, are planned. It is expected that results of SIR observations will significantly increase our understanding of the Moon. Since the exact arrival date and the orbital parameters of the SMART-1 spacecraft are not known yet, a more detailed planning of the scientific observations will follow in the near future. 相似文献
10.
S. Rodriguez S. Le Moulic C. Sotin H. Clnet R.N. Clark B. Buratti R.H. Brown T.B. McCord P.D. Nicholson K.H. Baines the VIMS Science Team 《Planetary and Space Science》2006,54(15):1510-1523
Titan is one of the primary scientific objectives of the NASA–ESA–ASI Cassini–Huygens mission. Scattering by haze particles in Titan's atmosphere and numerous methane absorptions dramatically veil Titan's surface in the visible range, though it can be studied more easily in some narrow infrared windows. The Visual and Infrared Mapping Spectrometer (VIMS) instrument onboard the Cassini spacecraft successfully imaged its surface in the atmospheric windows, taking hyperspectral images in the range 0.4–5.2 μm. On 26 October (TA flyby) and 13 December 2004 (TB flyby), the Cassini–Huygens mission flew over Titan at an altitude lower than 1200 km at closest approach. We report here on the analysis of VIMS images of the Huygens landing site acquired at TA and TB, with a spatial resolution ranging from 16 to14.4 km/pixel. The pure atmospheric backscattering component is corrected by using both an empirical method and a first-order theoretical model. Both approaches provide consistent results. After the removal of scattering, ratio images reveal subtle surface heterogeneities. A particularly contrasted structure appears in ratio images involving the 1.59 and 2.03 μm images north of the Huygens landing site. Although pure water ice cannot be the only component exposed at Titan's surface, this area is consistent with a local enrichment in exposed water ice and seems to be consistent with DISR/Huygens images and spectra interpretations. The images show also a morphological structure that can be interpreted as a 150 km diameter impact crater with a central peak. 相似文献