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1.
The first observations to detect a population of distant galaxies directly in the submillimetre waveband have recently been made using the new Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT). The results indicate that a large number of distant galaxies are radiating strongly in this waveband. Here we discuss their significance for source confusion in future millimetre/submillimetre-wave observations of both distant galaxies and cosmic microwave background radiation (CMBR) anisotropies. Earlier estimates of such confusion involved significant extrapolation of the results of observations of galaxies at low redshifts; our new estimates do not, as they are derived from direct observations of distant galaxies in the submillimetre waveband. The results have important consequences for the design and operation of existing and proposed millimetre/submillimetre-wave telescopes: the Planck Surveyor survey will be confusion-limited at frequencies greater than 350 GHz, even in the absence of Galactic dust emission; a 1σ confusion noise limit of about 0.44 mJy beam−1 is expected for the JCMT/SCUBA at a wavelength of 850 μm; and the subarcsecond resolution of large millimetre/submillimetre-wave interferometer arrays will be required in order to execute very deep galaxy surveys.  相似文献   

2.
Building on the technological success of the IceCube neutrino telescope, we outline a prospective low-energy extension that utilizes the clear ice of the South Pole. Aiming at a 10 Mton effective volume and a 10 MeV threshold, the detector would provide sufficient sensitivity to detect neutrino bursts from core-collapse supernovae (SNe) in nearby galaxies. The detector geometry and required density of instrumentation are discussed along with the requirements to control the various sources of background, such as solar neutrinos. In particular, the suppression of spallation events induced by atmospheric muons poses a challenge that will need to be addressed. Assuming this background can be controlled, we find that the resulting detector will be able to detect SNe from beyond 10 Mpc, delivering between 10 and 41 regular core-collapse SN detections per decade. It would further allow to study more speculative phenomena, such as optically dark (failed) SNe, where the collapse proceeds directly to a black hole, at a detection rate similar to that of regular SNe. We find that the biggest technological challenge lies in the required number of large area photo-sensors, with simultaneous strict limits on the allowed noise rates. If both can be realized, the detector concept we present will reach the required sensitivity with a comparatively small construction effort and hence offers a route to future routine observations of SNe with neutrinos.  相似文献   

3.
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   

4.
We exploit observations at 1.25 mm with the ESO–SEST telescope of a southern galaxy sample, selected from the IRAS PSC and complete to S 60=2 Jy, to derive the FIR and mm luminosity functions and the conditional probability distributions of FIR and mm luminosity of galaxies. The reliability of these estimates is ensured by the good observed correlation of the far-infrared and mm emissions. This detailed knowledge of the millimetric properties of galaxies is used to simulate the extragalactic sub-mm sky (background intensity, small-scale anisotropy signals and discrete source statistics), which is the target of a variety of ground-based and space observatories. We find, in particular, that a recent tentative detection of a sub-mm background would require, if confirmed, strong evolution with cosmic time of the galaxy long-wavelength emissivity. We finally discuss ways to test such evolution with present and forthcoming facilities: while emphasizing the difficulty of achieving this with large mm telescopes on the ground (because of the poor atmospheric conditions of current sub-mm sites), we mention an interesting opportunity with the long-wavelength camera on ISO . Preliminary results of deep surveys, both from space and from the ground, seem indeed to require excess emission in the past by dusty galaxies with respect to no-evolution predictions.  相似文献   

5.
Ermash  A. A.  Pilipenko  S. V.  Lukash  V. N. 《Astronomy Letters》2020,46(5):298-311
Astronomy Letters - The sensitivity of future far-infrared telescopes, such as Millimetron, will be limited by the confusion noise produced by distant galaxies. We have constructed a model of the...  相似文献   

6.
The redshifted spectral line radiation emitted from both atomic fine-structure and molecular rotational transitions in the interstellar medium (ISM) of high-redshift galaxies can be detected in the centimetre, millimetre and submillimetre wavebands. Here we predict the counts of galaxies detectable in an array of molecular and atomic lines. This calculation requires a reasonable knowledge of both the surface density of these galaxies on the sky, and the physical conditions in their ISM. The surface density is constrained using the results of submillimetre-wave continuum surveys. Follow-up OVRO Millimeter Array observations of two of the galaxies detected in the dust continuum have provided direct measurements of CO rotational line emission at redshifts of 2.56 and 2.81. Based on these direct high-redshift observations and on models of the ISM that are constrained by observations of low-redshift ultraluminous infrared galaxies, we predict the surface density of line-emitting galaxies as a function of line flux density and observing frequency. We incorporate the sensitivities and mapping speeds of existing and future millimetre/submillimetre-wave telescopes and spectrographs, and so assess the prospects for blank-field surveys to detect this line emission from gas-rich high-redshift galaxies.  相似文献   

7.
Charge‐exchange (CE) emission produces features which are detectable with the current X‐ray instrumentation in the brightest near galaxies. We describe these aspects in the observed X‐ray spectra of the star forming galaxies M82 and NGC 3256, from the Suzaku and XMM‐Newton telescopes. Emission from both ions (O, C) and neutrals (Mg, Si) is recognised. We also describe how microcalorimeter instrumentation on future missions will improve CE observations (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

8.
Summary The discovery of giant gravitational arcs and arclets in rich clusters of galaxies is one of the major events of the last decade in observational cosmology. High resolution imaging in subarcsecond seeing conditions of giant arcs gives information on the cluster potential and the matter distribution within the inner regions of clusters. Ultra-deep photometry of the clusters reveals numerous arclets with an orthoradial orientation from which one can infer the projected mass profile at large distance and the redshift distribution of the faintest distant background galaxies which are unobservable with standard spectroscopic techniques. Thanks to the strong magnification factor, the spectroscopy of giant arcs is possible and we can therefore observe with great detail a few very distant galaxies. Individual redshifts of arcs give the total mass of the lens, whereas the spectroscopy of a large sample of arcs also gives information on the redshift distribution of distant galaxies. It is obvious that cluster lenses play an important role as large natural telescopes for probing the distant universe. Finally, observations of multiple-arc configurations due to different sources may even constrain the cosmological parameters. We are now confident that gravitational lensing will be an essential tool within the next decade for observing very high redshift galaxies and the weak shear generated by the largest structures of the universe.In this review we summarize the present status of gravitational arc(let)s surveys with particular emphasis on the most important issues which have arisen during the last years and on the prospects for the future, regarding the rebirth of the Hubble Space Telescope, the coming of a new generation of Very Large Telescopes, and the development of large CCDs in the optical and the infrared.  相似文献   

9.
Origin of magnetic fields, its structure and effects on dynamical processes in stars to galaxies are not well understood. Lack of a direct probe has remained a problem for its study. The first phase of Square Kilometre Array (SKA-I), will have almost an order of magnitude higher sensitivity than the best existing radio telescope at GHz frequencies. In this contribution, we discuss specific science cases that are of interest to the Indian community concerned with astrophysical turbulence and magnetic fields. The SKA-I will allow observations of a large number of background sources with detectable polarization and measure their Faraday depths (FDs) through the Milky Way, other galaxies and their circum-galactic mediums. This will probe line-of-sight magnetic fields in these objects well and provide field configurations. Detailed comparison of observational data (e.g., pitch angles in spirals) with models which consider various processes giving rise to field amplification and maintenance (e.g., various types of dynamo models) will then be possible. Such observations will also provide the coherence scale of the fields and its random component through RM structure function. Measuring the random component is important to characterize turbulence in the medium. Observations of FDs with redshift will provide important information on magnetic field evolution as a function of redshift. The background sources could also be used to probe magnetic fields and its coherent scale in galaxy clusters and in bridges formed between interacting galaxies. Other than FDs, sensitive observations of synchrotron emission from galaxies will provide complimentary information on their magnetic field strengths in the sky plane. The core shift measurements of AGNs can provide more precise measurements of magnetic field in the sub parsec region near the black hole and its evolution. The low band of SKA-I will also be useful to study circularly polarized emission from Sun and comparing various models of field configurations with observations.  相似文献   

10.
In the coming few years, more new telescopes with large aperture will become available for observations of stars in the Milky Way and in Local Group galaxies, and, increasingly, of stars in more distant galaxies. A wide range of new targets will come within reach not only from the increase of telescope aperture, but also from new technology which improves the performance goals of modern instrumentation. New technologies on the horizon will be explored to evaluate their impact on scientific programs in the future. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

11.
COSMOS measures on a deep UK Schmidt Telescope Plate have been used to obtain the number-magnitude count for galaxies in a field of 14.6 square degrees near the South Galactic Pole. The results are in excellent agreement with data for the North Galactic Pole for galaxies fainter thanB=18.0, indicating no large-scale differences between north and south. A deficiency in numbers is observed for galaxies withB16.0. This is comparable to the deficiency atB17.5 for counts at the North Galactic Pole and supports the suggested asymmetry of the bright galaxy distribution between north and south galactic poles.  相似文献   

12.
Fermi卫星对GeV能段的河外伽马射线背景(Extragalactic Gamma-ray Background, EGB)进行了较为精确的测量, 极大提高了对高能伽马射线背景的认识, 但是在TeV能段, 使用空间探测器进行观测非常困难, 只能依赖地面伽马射线探测器, 如成像大气切伦科夫望远镜. 目前, 对于TeV能段的河外伽马射线背景的认识还不完善. 使用有低活跃状态能谱的61个TeV源(包含2个星暴星系、6个射电星系以及53个耀变体)的累计流量给出河外TeV伽马射线背景的下限. 结果显示, 低能段(0.5--4.5TeV)流量由两个临近的耀变体Mrk 421和Mrk 501主导, 贡献了大约58%的累计背景流量; 而大于4.5TeV的能段, 由3个已观测到10TeV以上能段流量的极端耀变体H 1426+428、1ES 1959+650以及1ES 0229+200主导. 最后分别探究了星暴星系、射电星系以及耀变体对河外TeV伽马射线背景的贡献, 不同耀变体子类对河外TeV伽马射线背景的贡献以及不同红移区间TeV源对河外伽马射线背景的贡献.  相似文献   

13.
ISLA will be an astronomical observatory, operating at the upper limit of our planet Earth atmosphere, offering space like observing conditions in most aspects. ISLA can be maintained easily, modified easily if necessary, always kept at the state of the art and operated for very extended periods without polluting the stratosphere. ISLA is ideally suited to become the first world space observatory as the observing conditions are very much space-like – diffraction limited angular resolution, very low ambient temperature, remote control – however ISLA is easily accessible, telescopes and instruments can be continuously improved and ISLA's costs corresponds only to those of ground-based modern astronomical installations like the ESO-VLT-, KECK- and GEMINI-observatories. The cost of observing and experimenting on ISLA will be orders of magnitudes lower than those of building and operating any space telescope, allowing the astronomers of developing nations to participate in the ISLA observatory within their limited financial possibilities as competent and full partners. ISLA's 4-m and 2-m telescopes will operate diffraction limited from 0.3 μm in the optical, over the infrared, far-infrared to the sub-mm spectral range. ISLA's individual telescopes will permit imaging with 20 milli-arcsec spatial resolution in the optical, 5 times better than the Hubble Space Telescope. ISLA's telescopes can be combined to form an interferometer with a maximum baseline of 250 m with nearly complete coverage of the u,v plane. Interferometric resolution will be of the order of 20 micro-arcsec for the optical. ISLA will thus offer spatial resolution comparable or better than the intercontinental VLBI radio interferometers. ISLA's telescope efficiency will be many orders of magnitude better than comparable ground-based telescopes. The light collecting power of ISLA's interferometric telescopes will be orders of magnitudes greater than the future space interferometers under discussion. ISLA, being an aviation project and not a space project, can be realised in the typical time scale for the development of aviation: about 5 years. ISLA's cost for the whole observatory, including its movable ground station etc. will be of the order of a typical medium size ESA space mission. ISLA's lifetime will be in excess of many decades, as it can easily be maintained, modernised, repaired and improved. ISLA will become the origin of a new astronomical international organisation with worldwide participation. ISLA's telescopes will be of the greatest importance to all astronomical fields, as it will permit to study much fainter, much more distant objects with microscopic spatial resolution in wavelength regions inaccessible from ground. ISLA's many telescopes permit easily simultaneous observations at many wavelengths for rapidly varying objects, from continuously monitoring the surfaces of the planets in our solar system, surfaces of close-by stars, nuclei of galaxies to QSO's. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

14.
AGB variables, particularly the large amplitude Mira type, are a vital step on the distance scale ladder. They will prove particularly important in the era of space telescopes and extremely large ground-based telescopes with adaptive optics, which will be optimized for infrared observing. Our current understanding of the distances to these stars is reviewed with particular emphasis on improvements that came from Hipparcos as well as on recent work on Local Group galaxies. In addition to providing the essential calibration for extragalactic distances Gaia may also provide unprecedented insight into the poorly understood mass-loss process itself.  相似文献   

15.
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16.
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   

17.
A new infrared camera (AIR Camera) has been developed at NASA-Ames Research Center for observations from ground-based telescopes. The heart of the camera is a Hughes 58 × 62 pixel Arsenic-doped Silicon detector array that has the spectral sensitivity range to allow observations in both the 10 and 20 micron atmospheric windows.The U.S. Government right to retain a non-exclusive, royalty-free licence in and to any copyright is acknowledged.  相似文献   

18.
We present basic observational strategies for ASTRO-F [also known as the Infra-Red Imaging Surveyor (IRIS) ] to be launched in 2004 by the Japanese Institute of Space and Astronautical Science (ISAS). We examine two survey scenarios, a deep ∼1 deg2 survey reaching sensitivities an order of magnitude below all but the deepest surveys performed by ISO in the mid-IR, and a shallow ∼18  deg2 mid-IR (7–25μm in six bands) covering an area greater than the entire area covered by all ISO mid-IR surveys. Using two cosmological models, the number of galaxies predicted for each survey is calculated. The first model uses an enhancement of a classical (1+ z )3.1 pure luminosity evolution model by Pearson & Rowan-Robinson. The second model incorporates a strongly evolving ultraluminous infrared galaxy component. For the deep survey, between 20 000 and 30 000 galaxies should be detected in the shortest wavebands, and ≈5000 in the longest (25-μm) band. It is predicted that the shallow survey will detect of the order of 100 000–150 000 sources. We find that for both ASTRO-F and other small-aperture space telescopes, confusion due to faint sources may be severe, especially at the longest mid-IR wavelengths. Using the exceptional range of observational options provided by ASTRO-F (nine wavelength filters and spectroscopic ability from 2.2 to 25 μm), we show that by combining the mid-IR observations with the near-IR camera on ASTRO-F , both the different galaxy populations and rough photometric redshifts can be distinguished in the colour–colour plane. In its role as a surveyor (plus near-IR spectroscopic ability) ASTRO-F will complement well the SIRTF space observatory mission.  相似文献   

19.
With the Planck and Herschel satellite missions of the European Space Agency, the far-infrared and submillimeter window will offer new investigation tools toward clusters of galaxies in the distant Universe. These are the Sunyaev Zel'dovich (SZ) effect of the cosmic microwave background and the thermal emission of dust grains. The power of the SZ effect is such that Planckis expected to discover thousands of new clusters at redshifts larger than 0.2, where only a few tens are known today. The dust can be present at large scale in the intracluster medium, and we show that even at very low abundances it is able to be a major cooling agent for the whole cluster. However the dominating dust emission will be that of the background infrared star forming galaxies. In all cases, the data processing of space borne sensitive submillimeter observations of clusters of galaxies such as the one that Planck and Herschel will provide, will require a very carefull combined analysis of the SZ effect and dust thermal emission.  相似文献   

20.
The Antarctic astronomical telescopes work chronically on the top of the unattended South Pole, and they have only one chance to maintain every year. Due to the complexity of the optical, mechanical, and electrical systems, the telescopes are hard to be maintained and need versatile expedition teams, which means that an excessive awareness is essential for the reliability of the Antarctic telescopes. Based on the fault mechanism and fault mode of the main-axis control system for the Antarctic equatorial astronomical telescope AST3-3 (Antarctic Schmidt Telescope 3-3), the method of fault tree analysis is introduced in this article, and we obtain the importance degree of the top event from the importance degree of the bottom event structure. From the above result, the hidden problems and weak links of the system can be effectively found out, which will indicate the direction for improving the stability of the system and optimizing the design of the system.  相似文献   

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