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1.
Experimental results on the spectral identification of new infrared absorption features and the changes of their absorbances produced through vacuum ultraviolet-extreme ultraviolet (VUV-EUV) photon-induced chemical reactions in the C2H2-H2O mixed ices at 10 K are obtained. To the best of our knowledge, this is the first time that EUV photons have been employed in the study of the photolysis of ice analogues. Two different compositions, i.e., C2H2:H2O=1:4 and 1:1, were investigated in this work. A tunable intense synchrotron radiation light source available at the Synchrotron Radiation Research Center, Hsinchu, Taiwan, was employed to provide the required VUV-EUV photons. In this study, the photon wavelengths selected to irradiate the icy samples corresponded to the prominent solar hydrogen, helium, and helium ion lines at 121.6 nm, 58.4 nm, and 30.4 nm, respectively. The photon dosages used were typically in the range of 1×1015 to 2×1017 photons. Molecular species produced and identified in the ice samples at 10 K resulting from VUV-EUV photon irradiation are mainly CO, CO2, CH4, C2H6, CH3OH, and H2CO. In addition to several unidentified features, we have tentatively assigned several absorption features to HCO, C3H8, and C2H5OH. While new molecular species were formed, the original reactants, i.e., H2O and C2H2, were detectably depleted due to their conversion to other species. The new chemical species produced by irradiation of photons at 30.4 nm and 58.4 nm can be different from those produced by the 121.6-nm photolysis. In general, the product column density of CO reaches saturation at a lower photon dosage than that of CO2. Furthermore, the production yield of CO is higher than that of CO2 in the photon irradiation. In the present study, we also observe that the photon-induced chemical reaction yields are high using photons at 30.4 and 58.4 nm. The results presented in this work are essential to our understanding of chemical synthesis in ice analogues, e.g., the cometary-type ices and icy satellites of planetary systems.  相似文献   

2.
We present the main characteristics of a new mid-IR camera, TIRCAM, operating at the 1.5 m Italian Infrared Telescope.  相似文献   

3.
徐璺  俞允强 《天文学报》1996,37(3):339-344
最近对哈勃常数的观测趋于一个大的值，引进宇宙学常数为主的宇宙学成了保持平坦宇宙并解决年龄矛盾的主要方法．本文讨论了（ｈ，Ω∧，ΩＭ）＝（０．８，０．８，０．２）的宇宙模型的一些后果，并和高红移椭球星系的观测，以及星系计数的观测作了比较．尽管观测事实表明Ω∧＝０．８模型比Ω∧＝０模型更具有优势，但这个结论仍是模糊的．除了年龄问题外，还不能排除（０．８，０，１）标准宇宙学的存在．  相似文献   

4.
Near‐Infrared high spectral and spatial resolution spectroscopy offers new and innovative observing opportunities for astronomy. The “traditional” benefits of IR‐astronomy – strongly reduced extinction and availability of adaptive optics – more than offset for many applications the compared to CCD‐based astronomy strongly reduced sensitivity. Especially in high resolution spectroscopy interferences by telluric lines can be minimized. Moreover for abundance studies many important atomic lines can be accessed in the NIR. A novel spectral feature available for quantitative spectroscopy are the molecular rotational‐vibrational transitions which allow for fundamentally new studies of condensed objects and atmospheres. This is also an important complement to radio‐astronomy, especially with ALMA, where molecules are generally only observed in the vibrational ground state. Rot‐vib transitions also allow high precision abundance measurements – including isotopic ratios – fundamental to understand the thermo‐nuclear processes in stars beyond the main sequence. Quantitative modeling of atmospheres has progressed such that the unambiguous interpretation of IR‐spectra is now well established. In combination with adaptive optics spectro‐astrometry is even more powerful and with VLT‐CRIRES a spatial resolution of better than one milli‐arcsecond has been demonstrated. Some highlights and recent results will be presented: our solar system, extrasolar planets, star‐ and planet formation, stellar evolution and the formation of galactic bulges (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

5.
The dwarf population of starburst galaxies is analyzed by the method of evolving population synthesis. The results show that the existence of an additional population can give a good fit to the available number counts and redshift surveys. These dwarf galaxies readily evolve into low surface brightness objects and become undetectable in our local neighbourhood.  相似文献   

6.
In less than a decade, infrared array detectors have revolutionized infrared astronomy. Most of us remember using single element photometers in the early eighties, yet today, most of us are using 256×256 pixel arrays. At this meeting we have heard of plans to fabricate 1024×1024 arrays in the near infrared. From one to one million pixels in such a short period of time is amazing. The new array technology has also stimulated the development of many varieties of infrared cameras and spectrometers. At the UCLA Infrared Imaging Detector Lab we have commissioned two near infrared imaging systems (KCam and Gemini) based on 256×256 arrays and a spectrometer design study is in progress for 1024×1024 arrays. Performance of these cameras on the telescope will be reported briefly.  相似文献   

7.
The advent of solid-state imaging devices transformed astronomy. Beginning with the introduction into astronomy of charge-coupled devices in 1976, followed a decade later by infrared arrays, astronomers gained access to near-perfect imaging devices. The consequences have been nothing short of revolutionary, perhaps especially so in the infrared. Witness, for example, the spectacular pictures from the Hubble Space Telescope cameras, or the impressive infrared imagery from the 2MASS project. Within the last decade CCD formats deployed or planned for use in ground-based cameras have become huge. Infrared mosaics, stimulated by the Next Generation Space Telescope, are coming soon. In addition, new technologies such as CMOS (Complementary Metal Oxide Semiconductors) and STJs (Superconductiong Tunnel Junctions) are being developed and the future of astronomical detectors looks very exciting, especially in an era of giant telescopes performing at their diffraction-limit. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

8.
红外相机CASCAM光学设计   总被引：1，自引：1，他引：0  
介绍紫金山天文台研制的光学-近红外相机CASCAM（Chinese Academy of Science，CAMera)的光学系统设计．CASCAM相机以红外列阵HAWAII-1和光学CCD为探测器，配备国家天文台兴隆观测站2．16米和1．26米望远镜进行0．4—2．5μm波长范围的成像和偏振成像观测．相机的光学系统由F／9→F／6缩焦系统和Offner反射成像系统构成．优化设计结果表明，光学设计方案已满足天文观测的要求．CASCAM相机在设计上实现了光学-近红外很宽波段的消色差变焦，并在楔形分柬片、常温滤光片轮和折射式焦面摆动技术等方面进行了新的尝试．  相似文献   

9.
We have reconsidered the energetics of the BN/KL infrared complex, using array images at nine wavelengths between 4.8 and 20 m, and find a much lower luminosity for IRc2 than the generally accepted value. The new observations resolve larcsec structure throughout the region, including several new compact sources within a few arcsec of IRc2 and significant details imaged in the 9.7 m silicate feature. Together with other recent work, the results suggest that luminous stars associated with three compact HII regions found within BN/KL, rather than IRc2, may be the more significant luminosity sources for the complex.  相似文献   

10.
A number of deep, wide-field, near-infrared (NIR) surveys employing new infrared cameras on 4-m class telescopes are about to commence. These surveys have the potential to determine the fraction of luminous dust-obscured quasars that may have eluded surveys undertaken at optical wavelengths. In order to understand the new observations it is essential to make accurate predictions of surface densities and number–redshift relations for unobscured quasars in the NIR based on information from surveys at shorter wavelengths. The accuracy of the predictions depends critically on a number of key components. The commonly used single power-law representation for quasar spectral energy distributions (SEDs) is inadequate and the use of an SED incorporating the upturn in continuum flux at  λ∼ 12 000 Å  is essential. The presence of quasar host galaxies is particularly important over the rest-frame wavelength interval  8000 < λ < 16 000 Å  and we provide an empirical determination of the magnitude distribution of host galaxies using a low-redshift sample of quasars from the Sloan Digital Sky Survey Data Release 3 quasar catalogue. A range of models for the dependence of host galaxy luminosity on quasar luminosity is investigated, along with the implications for the NIR surveys. Even adopting a conservative model for the behaviour of host galaxy luminosity the number counts for shallow surveys in the K band increase by a factor of 2. The degree of morphological selection applied to define candidate quasar samples in the NIR is found to be an important factor in determining the fraction of the quasar population included in such samples.  相似文献   

11.
We find that five sources listed in the new carbon star catalog are not really carbon-rich objects but oxygen-rich stars, because they all have the prominent 10μm silicate features in absorption and the 1612MHz OH maser emission or/and the SiO molecular features. These objects were considered as carbon stars in the catalog based only on their locations in the infrared two-color diagram. Therefore to use the infrared two-color diagram to distinguish carbon-rich stars from oxygenrich stars must be done with caution, because, in general, it has only a statistical meaning.  相似文献   

12.
Keck AO survey of Io global volcanic activity between 2 and 5 μm   总被引：1，自引：0，他引：1  
We present in this Keck AO paper the first global high angular resolution observations of Io in three broadband near-infrared filters: Kc (2.3 μm), Lp (3.8 μm), and Ms (4.7 μm). The Keck AO observations are composed of 13 data sets taken during short time intervals spanning 10 nights in December, 2001. The MISTRAL deconvolution process, which is specifically aimed for planetary images, was applied to each image. The spatial resolution achieved with those ground-based observations is 150, 240, and 300 km in the Kc, Lp, and Ms band, respectively, making them similar in quality to most of the distant observations of the Galileo/NIMS instrument. Eleven images per filter were selected and stitched together after being deprojected to build a cylindrical map of the entire surface of the satellite. In Kc-band, surface albedo features, such as paterae (R>60 km) are easily identifiable. The Babbar region is characterized by extremely low albedo at 2.2 μm, and shows an absorption band at 0.9 μm in Galileo/SSI data. These suggest that this region is covered by dark silicate deposits, possibly made of orthopyroxene. In the Lp-Ms (3-5 μm) bands, the thermal emission from active centers is easily identified. We detected 26 hot spots in both broadband filters over the entire surface of the minor planet; two have never been seen active before, nine more are seen in the Ms band. We focused our study on the hot spots detected in both broadband filters. Using the measurements of their brightness, we derived the temperature and area covered by 100 brightness measurements. Loki displayed a relatively quiescent activity. Dazhbog, a new eruption detected by Galileo/NIMS in August 2001, is a major feature in our survey. We also point out the fading of Tvashtar volcanic activity after more than two years of energetic activity, and the presence of a hot, but small, active center at the location of Surt, possibly a remnant of its exceptional eruption detected in February 2001. Two new active centers, labeled F and V on our data, are detected. Using the best temperature and the surface area derived from the L and M band intensities, we calculated the thermal output of each active center. The most energetic hot spots are Loki and Dazhbog, representing respectively 36 and 19% of the total output calculated from a temperature fit of all hot spots (20.6×1012 W). Based on the temperature derived from hot spots (∼400 K), our measurement can unambiguously identify the contribution to the heat flux from the silicate portion of the surface. Because the entire surface was observed, no extrapolation was required to calculate that flux. It is also important to note that we measured the brightness of the individual hot spots when they were located close to the Central Meridian. This minimizes the line-of-sight effect which does not follow strictly a classical cosine law. Finally, we argue that despite the widespread volcanic activity detected, Io was relatively quiescent in December 2001, with a minimum mean total output of 0.4-1.2 W m−2. This output is at least a factor of two lower than those inferred from observations made at longer wavelengths and at different epochs.  相似文献   

13.
We present proper-motion measurements for carbon stars found during the APM Survey for Cool Carbon Stars in the Galactic halo as reported in an earlier paper by Totten & Irwin. Measurements are obtained using a combination of POSSI, POSSII and UKST survey plates supplemented where necessary by CCD frames taken at the Isaac Newton Telescope. We find no significant proper motion for any of the new APM colour-selected carbon stars and so conclude that there are no dwarf carbon stars present within this sample. We also present proper-motion measurements for three previously known dwarf carbon stars and demonstrate that these measurements agree favourably with those previously quoted in the literature, verifying our method of determining proper motions. Results from a complimentary program of JHK photometry obtained at the South African Astronomical Observatory are also presented. Dwarf carbon stars are believed to have anomalous near-infrared colours, and this feature is used for further investigation of the nature of the APM carbon stars. Our results support the use of JHK photometry as a dwarf/giant discriminator and also reinforce the conclusion that none of the new APM-selected carbon stars is a dwarf. Finally, proper-motion measurements combined with extant JHK photometry are presented for a sample of previously known halo carbon stars, suggesting that one of these stars, CLS29, is likely to be a previously unrecognized dwarf carbon star.  相似文献   

14.
本文采用演化星族综合方法，讨论了在低红移因短时间星暴过程而变亮的矮星系族。指出，它们的存在能够与目前暗星系计数和红移巡天结果相容，作为一个附加的星系族，它们较易演化为低面光度的星系而在邻域中探测不到，因此是解释暗星系计数和红移巡天结果的适当候选天体，值得对它们作进一步的研究。  相似文献   

15.
H2O, CO and CO2 ices are condensed on carbonaceous and silicate dust grains in dense interstellar clouds and circumstellar environments. The presence of these ices is inferred by analysing their infrared (IR) spectra. The upcoming Herschel space observatory (HERSCHEL) and ground-based astronomy project (ALMA) will provide new spectral data in the unexplored far infrared (FIR) and sub-millimetre range. In our laboratory we are developing instrumentation to study ices at IR region. One of the key components of our laboratory is a silicon composite bolometer in our IFS. This detector allows us to obtain spectra with a sensitivity much greater than that obtained with a standard deuterated triglycine sulphate (DTGS) detector working at room temperature and under vacuum conditions. We plan to collect mid infrared (MIR) and FIR spectra of simple ices and their mixtures and compare these with observational data. It is also planned to do a systematic laboratory study of the effects that ultraviolet (UV) photolysis and thermal annealing have on the ice band profiles and their structure.  相似文献   

16.
The JHKL' photometry and 2.3–4 μm spectrophotometry of some M giants, S type stars and carbon stars are presented in this paper. It is found that in combination with IRAS data, the energy spectra in 1–100 μm of S type stars are intermediate between those of M giants and carbon stars, which are obviously different. The spectrophotometry in the near infrared shows that, besides carbon stars, which have HCN and C2H2 strong absorptions at 3.1 μm, some S type stars have the similar but weaker absorption in the same spectral region. However, no trace of any absorption at 3.1 μm can be seen in M giants. These results probably provide more evidence for the M-S-C sequence in the late stage of stellar evolution.  相似文献   

17.
We have retrieved Spitzer archive data of pre-stellar cores taken with the Multiband Imaging Photometer for Spitzer (MIPS) at a wavelength of 160 μm. Seventeen images, containing 18 cores, were constructed. Flux densities were measured for each core, and background estimates were made. Mean off-source backgrounds were found to be 48 ± 10 MJy sr−1 in Taurus and 140 ± 55 MJy sr−1 in Ophiuchus. Consistency was found between the MIPS 170-μm and ISOPHOT 160-μm calibrations. Fourteen cores were detected both by MIPS and by our previous submillimetre surveys. Spectral energy distributions were made for each core, using additional 24- and 70-μm data from the Spitzer data archive, as well as previous infrared and submillimetre data. Previous temperature estimates were refined, and new temperature estimates were made where no Infrared Space Observatory ( ISO ) data exist. A temperature range of 8–18 K was found for the cores, with most lying in the range 10–13 K. We discount recent claims that a large number of pre-stellar cores may have been misclassified and in fact contain low-luminosity protostars detectable only by Spitzer . We find no new protostars in our sample other than that previously reported in L1521F. It is shown that this has a negligible effect on pre-stellar lifetime estimates.  相似文献   

18.
Photometric observations at optical and near-infrared wavelengths are presented for members of a new sample of candidate Vega-like systems, or main sequence stars with excess infrared emission due to circumstellar dust. The observations are combined with IRAS fluxes to define the spectral energy distributions of the sources. Most of the sources show only photospheric emission at near-IR wavelengths, indicating a lack of hot (∼1000 K) dust. Mid-infrared spectra are presented for four sources from the sample. One of them, HD 150193, shows strong silicate emission, while another, HD 176363, was not detected. The spectra of two stars from our previous sample of Vega-like sources both show UIR-band emission, attributed to hydrocarbon materials. Detailed comparisons of the optical and IRAS positions suggest that in some cases the IRAS source is not physically associated with the visible star. Alternative associations are suggested for several of these sources. Fractional excess luminosities are derived from the observed spectral energy distributions. The values found are comparable to those measured previously for other Vega-like sources.  相似文献   

19.
The near-IR spectral properties of minerals, meteorites, and lunar soil vary with temperature. The manner in which these materials vary is diagnostic of aspects of their composition. We quantify the spectral dependence on temperature by reporting the change in relative reflectance with temperature as a function of wavelength. We call this quantity, ΔR/ΔT (in units of K−1), as a function of temperature the “thermo-reflectance spectrum.” The thermo-reflectance spectra of olivine and pyroxene are distinct, and most of the observable structure in thermo-reflectance spectra of the ordinary and carbonaceous chondrites can be understood in terms of a mixture of the thermo-reflectance spectra of olivine and pyroxene. The magnitude of thermo-reflectance spectra of meteorites and lunar soils is much less than that of pure minerals. Lunar soils are particularly subdued. While conventional analysis of remotely obtained spectra of the Moon can neglect temperature effects, spatially resolved measurements of the surface of the asteroid Vesta will likely have a strong temperature-dependent component based on measurements of a eucrite and a howardite.  相似文献   

20.
Hanner  M. S.  Gehrz  R. D.  Harker  D. E.  Hayward  T. L.  Lynch  D. K.  Mason  C. C.  Russell  R. W.  Williams  D. M.  Wooden  D. H.  Woodward  C. E. 《Earth, Moon, and Planets》1997,79(1-3):247-264
The dust coma of comet Hale-Bopp was observed in the thermal infrared over a wide range in solar heating (R = 4.9–0.9 AU) and over the full wavelength range from 3 μm to 160 μm. Unusual early activity produced an extensive coma containing small warm refractory grains; already at 4.9 AU, the 10 μm silicate emission feature was strong and the color temperature was 30% above the equilibrium blackbody temperature. Near perihelion the high color temperature, strong silicate feature, and high albedo indicated a smaller mean grain size than in other comets. The 8–13 μm spectra revealed a silicate emission feature similar in shape to that seen in P/Halley and several new and long period comets. Detailed spectral structure in the feature was consistent over time and with different instruments; the main peaks occur at 9.3, 10.0 and 11.2 μm. These peaks can be identified with olivine and pyroxene minerals, linking the comet dust to the anhydrous chondritic aggregate interplanetary dust particles. Spectra at 16–40 μm taken with the ISO SWS displayed pronounced emission peaks due to Mg-rich crystalline olivine, consistent with the 11.2 μm peak. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

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