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1.
Over the next several years we will deploy a series of spectrometers, imagers, and telescopes at the South Pole as part of a project named SPIREX-for South Pole Infrared Explorer. Our goal is to survey a substantial area of the sky to study the origins of galaxies and stars.From space, the zodiacal light is the limiting source of noise over a wide range of wavelengths. It has a minimum in the near infrared: the reflected sunlight is diminishing with wavelength and reradiated thermal emission from the warm dust is on the rise. For this and other reasons, the near infrared is potentially the best window in which to carry out deep surveys of galaxies.On the ground, the sensitivity of observations in the near infrared is limited by the Poisson noise of the large background flux from the atmosphere and telescope. Within a restricted wavelength range, this background depends only on two parameters: their temperature and emissivity. By building very low emissivity telescopes and operating them in the bitter cold of the Antarctic winter we expect to make observations that will rival in sensitivity those attainable from cooled space-based telescopes.  相似文献   

2.
We report initial performance measurements of a 1/8 scale version of a 32×32 pixel array under development for SIRTF. This array demonstrates that we can reach the sensitivity limits set by the natural backgrounds in space while providing good imaging and photometric performance. Based on the achieved performance levels, we project the imaging capabilities of SIRTF in the far infrared to exceed by a factor of more than 10,000 those achieved by any preceding telescope.  相似文献   

3.
Abstract– Distributions of organic functional groups as well as inorganic features were analyzed in the Bells (CM2) carbonaceous chondrite using near‐field infrared (NFIR) spectroscopy. NFIR spectroscopy has recently been developed to enable infrared spectral mapping beyond the optical diffraction limit of conventional Fourier transform infrared microspectroscopy. NFIR spectral mapping of the Bells 300 nm thick sections on Al plates for 7.5 × 7.5 μm2 areas showed some C‐H‐rich areas which were considered to represent the organic‐rich areas. Heterogeneous distributions of organic matter as well as those of inorganic phases such as silicates (Si‐O) were observed with 1 μm spatial resolution. The NFIR mappings of aliphatic C‐H (2960 and 2930 cm?1) and structural OH (3650 cm?1) confirm that organic matter is associated with phyllosilicates as previously suggested. The NFIR mapping method can provide 1 μm spatial distribution of organic functional groups and their association with minerals. High local sensitivity of NFIR enables us to find organic‐rich areas and to characterize them by their aliphatic CH2/CH3 ratios. The aliphatic CH2/CH3 ratio of Bells is slightly higher than Murchison, similar to Orgueil, and lower than literature values of IDPs and cometary dust particles.  相似文献   

4.
The extragalactic background radiation produced by distant galaxies emitting in the far infrared limits the sensitivity of telescopes operating in this range due to confusion. We have constructed a model of the infrared background based on numerical simulations of the large-scale structure of the Universe and the evolution of dark matter halos. The predictions of this model agree well with the existing data on source counts. We have constructed maps of a sky field with an area of 1 deg2 directly from our simulated observations and measured the confusion limit. At wavelengths 100–300 μm the confusion limit for a 10-m telescope has been shown to be at least an order of magnitude lower than that for a 3.5-m one. A spectral analysis of the simulated infrared background maps clearly reveals the large-scale structure of the Universe. The two-dimensional power spectrum of these maps has turned out to be close to that measured by space observatories in the infrared. However, the fluctuations in the number of intensity peaks observed in the simulated field show no clear correlation with superclusters of galaxies; the large-scale structure has virtually no effect on the confusion limit.  相似文献   

5.
The dust‐to‐gas ratios in three different samples of luminous, ultraluminous, and hyperluminous infrared galaxies are calculated by modelling their radio to soft X‐ray spectral energy distributions (SED) using composite models which account for the photoionizing radiation from H II regions, starbursts, or AGNs, and for shocks. The models are limited to a set which broadly reproduces the mid‐IR fine structure line ratios of local, IR bright, starburst galaxies. The results show that two types of clouds contribute to the IR emission. Those characterized by low shock velocities and low preshock densities explain the far‐IR dust emission, while those with higher velocities and densities contribute to the mid‐IR dust emission. Clouds with shock velocities of 500 km s–1 prevail in hyperluminous infrared galaxies. An AGN is found in nearly all of the ultraluminous infrared galaxies and in half of the luminous infrared galaxies of the sample. High IR luminosities depend on dust‐to‐gas ratios as high as ∼0.1 by mass, however most hyperluminous IR galaxies show dustto‐gas ratios much lower than those calculated for the luminous and ultraluminous IR galaxies. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

6.
Directional thermal infrared measurements of the martian surface is one of a variety of methods that may be used to characterize surface roughness and slopes at scales smaller than can be obtained by orbital imagery. Thermal Emission Spectrometer (TES) emission phase function (EPF) observations show distinct apparent temperature variations with azimuth and emission angle that are consistent with the presence of warm, sunlit and cool, shaded slopes at typically ∼0.1 m scales. A surface model of a Gaussian distribution of azimuth independent slopes (described by θ-bar) is combined with a thermal model to predict surface temperature from each viewing angle and azimuth of the TES EPF observation. The models can be used to predict surface slopes using the difference in measured apparent temperature from 2 separate 60-70° emission angle observations taken ∼180° in azimuth relative to each other. Most martian surfaces are consistent with low to moderate slope distributions. The slope distributions display distinct correlations with latitude, longitude, and albedo. Exceptionally smooth surfaces are located at lower latitudes in both the southern highlands as well as in high albedo dusty terrains. High slopes are associated with southern high-latitude patterned ground and north polar sand dunes. There is little apparent correlation between high resolution imagery and the derived θ-bar, with exceptions such as duneforms. This method can be used to characterize potential landing sites by assuming fractal scaling behavior to meter scales. More precisely targeted thermal infrared observations from other spacecraft instruments are capable of significantly reducing uncertainty as well as reducing measurement spot size from 10s of kilometers to sub-kilometer scales.  相似文献   

7.
AKARI, formerly known as ASTRO-F, is the second Japanese space mission to perform infrared astronomical observations. AKARI was launched on 21 February 2006 (UT) and brought into a sun-synchronous polar orbit at an altitude of 700 km by a JAXA M-V rocket. AKARI has a telescope with a primary-mirror aperture size of 685 mm together with two focal-plane instruments on board: the Infrared Camera (IRC), which covers the spectral range 2–26 μm and the Far-Infrared Surveyor (FIS), which operates in the range 50–180 μm. The telescope mirrors are made of sandwich-type silicon carbide, specially developed for AKARI. The focal-plane instruments and the telescope are cooled by a unique cryogenic system that kept the telescope at 6K for 550 days with 180 l super-fluid liquid Helium (LHe) with the help of mechanical coolers on board. Despite the small telescope size, the cold environment and the state-of-the-art detectors enable very sensitive observations at infrared wavelengths. To take advantage of the characteristics of the sun-synchronous polar orbit, AKARI performed an all-sky survey during the LHe holding period in four far-infrared bands with FIS and two mid-infrared bands with IRC, which surpasses the IRAS survey made in 1983 in sensitivity, spatial resolution, and spectral coverage. AKARI also made over 5,000 pointing observations at given targets in the sky for approximately 10 min each, for deep imaging and spectroscopy from 2 to 180 μm during the LHe holding period. The LHe ran out on 26 August 2007, since which date the telescope and instrument are still kept around 40K by the mechanical cooler on board, and near-infrared imaging and spectroscopic observations with IRC are now being continued in pointing mode.  相似文献   

8.
The expected thermal emission from the shell around stars has been calculated on the graphite model. The calculated spectral distribution is in reasonable agreement with the observed infrared emission from some of the infrared stars.  相似文献   

9.
A model of two compact components (one contributes at radio and submillimeter wavelength and the other is very small and emits at the infrared region) is proposed to interpret the spectrum of quasi-stellar objects at radio and infrared wavelengths. The physical parameters are estimated from the observed data of 3C 273 for our model and for the model which is derived by assuming the infrared emission as an extrapolation of the synchrotron radio-source. It was proved that our model can explain the observational spectra, while the other model has some difficulties to interpret them completely.This work was partially supported by the Brasilian research agency CNPq  相似文献   

10.
The photodissociation regions located between ionized regions and molecular clouds are studied by using a one-dimensional model where molecular H2 are formed on the dust grains, and destructed by photodissociation. The escape probability method is used for the line transfer. The excitation of infrared emission lines of H2 by UV fluorescence in M17, by shock heating in Orion KL and mainly by UV fluorescence in NGC 2023 are discussed.  相似文献   

11.
Using transmittance data appropriate for grain material which is predominantly comprised of polysaccharides we have computed infrared fluxes from several types of galactic infrared source. The model used in these computations involves polysaccharide condensation in material flowing out from O-type stars. With the exception of rather minor discrepancies we show that it is possible to match the 2.1–13 observations of a wide range of galactic infrared sources.  相似文献   

12.
Assuming a dust model of Reeset al. (1969), we study the time dependence of the infrared emission from grains which absorb variable ultraviolet radiation. A time scale for the variability is shown to be fairly small compared with the light travel-time across the infrared emitting region, of which size depends on the wavelength strongly. Comparison of calculated infrared light curves with observations of NGC 4151 leads to the conclusion that the variability at 2.2 is consistent with interpretation by the infrared emission on the basis of thermal process.  相似文献   

13.
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14.
We consider potential sources of infrared (1 to 1 mm) continuum in solar flares. Several mechanisms should produce detectable fluxes: in the 350 window for ground-based observations, impulsive emission will arise in synchrotron radiation from 1–10 MeV electrons, and possibly thermal (free-free) continuum from the source of the white-light flare; the hot flare plasma responsible for soft X-ray emission will also emit detectable fluxes of free-free continuum in the largest flares. At shorter wavelengths the dominant infrared emission will come from the H flare itself. Observations in the infrared wavelengths will help to complete our picture of flare structure in both the impulsive and gradual phases.  相似文献   

15.
A new model for source counts from 8 to 1100 μm is presented, which agrees well with source-count data and the observed background spectrum. The model assumes different evolution for each of the four infrared template types used. The evolution is modified in two ways compared to my 2001 model: (i) the exponential factor is modified so that it tends to a constant value at late times and (ii) the power-law factor is modified so that it tends to zero at redshift   z f   , rather than zero as assumed previously. I find strong evidence from the 850 and 1100 μm counts, and from the infrared background, that   z f = 4–5  , with some preference for a value at the low end of the range, implying that star-forming galaxies at   z > 5  are not significant infrared emitters, presumably due to a low opacity in dust at these early epochs.
The model involves zero or even negative evolution for starbursts and active galactic nuclei at low redshifts (<0.2), suggesting that the era of major mergers and strong galaxy–galaxy interactions is over.  相似文献   

16.
The backward evolution approach to modelling galaxy source counts is re-visited in the wake of the numerous results and revelations from the Infrared Space Observatory ( ISO ), the Submillimetre Common User Bolometer Array (SCUBA) and the detections and measurements of the cosmic extragalactic background light. Using the framework of the Pearson & Rowan-Robinson galaxy evolution model, the observed source counts and background measurements are used to constrain the evolution in the galaxy population. It is found that a strong evolution in both density and luminosity of the high-luminosity tail of the infrared (IR) luminosity function, interpreted as the ultraluminous galaxies discovered first by IRAS and later elevated in status by SCUBA and ISO , can account for the source counts from 15 μm (where it matches the undulations in the integral counts and the hump in the differential counts extremely well) to the submillimetre region, as well as explain the peak in the cosmic infrared background at ∼140 μm. The submillimetre counts are interpreted as the superposition of two separate populations comprising ultraluminous infrared galaxies (ULIGs) at the brighter submillimetre fluxes and starburst galaxies at fluxes fainter than ∼2 mJy. In this scenario the high-redshift ULIGs are tenuously interpreted as the progenitors of today's giant elliptical (gE) galaxies.
All the source count models can be accessed via the world wide web at the URL http://www.ir.isas.ac.jp/~cpp/counts/  相似文献   

17.
Summary The unprecedented quality of the IRAS data prompted a series of papers reinvestigating the origin of the galactic infrared/submillimeter radiation and the nature of the heating sources of the interstellar dust. The scope of this paper is to review the main results of these new studies. Sect. 1 contains a general introduction to the subject and an overview of the earlier work. In Sect. 2 and 3, we summarize our current knowledge on dust properties and on the interstellar radiation field. Then, we present the recent interpretations of the infrared emission of our Galaxy, which are based on the IRAS data: in Sect. 4 we present the results from the galactic disk; Sect. 5 covers the question of the contribution from small dust particles, and in Sect. 6 we describe the infrared radiation from the galactic center. The nature of the heating sources and the origin of the galactic infrared radiation is then discussed in Sect. 7. Finally, Sect. 8 presents a comparison of our Galaxy with external galaxies  相似文献   

18.
The first attempts to measure the infrared outputs of stars preceded by nearly a century the permanent establishment of infrared astronomy as an important aspect of the field. There were a number of false starts in that century, significant efforts that had little impact on the astronomical community at large. Why did these efforts fizzle out? What was different in the start that did not fizzle, in the 1960s? I suggest that the most important advances were the success of radio astronomy in demonstrating interesting phenomena outside of the optical regime, and the establishment virtually simultaneously in the United States of a number of research groups that could support each other and compete against one another in their approach to infrared astronomy.  相似文献   

19.
The study of circumstellar disks around young stellar objects is arguably the area of astrophysics on which the technique of infrared interferometry has had the biggest impact. Here I will review the existing set of observations in this field, concentrating on disks but also including jets/winds and stellar properties. At the end, there is a brief discussion of how ongoing technical developments and observational improvements will expand the impact of infrared interferometry on the study of star formation.  相似文献   

20.
We have calculated for extragalactic Hii regions, the expected relationship between the radio flux at 11 cm and the infrared flux at 11 and 20 m based on the grain models and the parameters which fit the observations of galactic Hii regions. It is shown that the measured infrared fluxes of extragalactic Hii regions are consistent with the expected infrared fluxes for these objects.  相似文献   

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