共查询到20条相似文献,搜索用时 31 毫秒
1.
F. J. Castander 《Astrophysics and Space Science》1998,263(1-4):91-94
The Sloan Digital Sky Survey (SDSS) is going to carry out a uniform survey of π steradians of the sky in the Northern Galactic
cap and ∼ 225 deg2 in the Southern Hemisphere. The survey consists of a photometric and a spectroscopic survey. The SDSS will generate accurate
photometry in five bands of approximately tens of millions of galaxies, tens of millions of stars and roughly a million quasars.
It will also take spectra and measure redshifts of approximately a million galaxies and ten thousand quasars.
The main characteristics and components of the survey are a dedicated 2.5m telescope, wide field correctors for photometry
and spectroscopy that will provide a field of view of ∼ 3 degrees, a photometric camera with 30 photometric and 22 astrometric
CCDs, and two fibre-fed spectrographs of 320 fibres each. The survey will produce a publicly available science database of
Terabytes dimensions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
Stefan Hilbert R. Benton Metcalf S. D. M. White 《Monthly notices of the Royal Astronomical Society》2007,382(4):1494-1502
21-cm emission from neutral hydrogen during and before the epoch of cosmic reionization is gravitationally lensed by material at all lower redshifts. Low-frequency radio observations of this emission can be used to reconstruct the projected mass distribution of foreground material, both light and dark. We compare the potential imaging capabilities of such 21-cm lensing with those of future galaxy lensing surveys. We use the Millennium Simulation to simulate large-area maps of the lensing convergence with the noise, resolution and redshift-weighting achievable with a variety of idealized observation programmes. We find that the signal-to-noise ratio of 21-cm lens maps can far exceed that of any map made using galaxy lensing. If the irreducible noise limit can be reached with a sufficiently large radio telescope, the projected convergence map provides a high-fidelity image of the true matter distribution, allowing the dark matter haloes of individual galaxies to be viewed directly, and giving a wealth of statistical and morphological information about the relative distributions of mass and light. For instrumental designs like that planned for the Square Kilometre Array, high-fidelity mass imaging may be possible near the resolution limit of the core array of the telescope. 相似文献
3.
We analyze the statistical properties of normal galaxies to be detected in the all-sky survey by the eROSITA X-ray telescope of the Spectrum-X-Gamma observatory. With the current configuration and parameters of the eROSITA telescope, the sensitivity of a 4-year-long all-sky survey will be ≈10?14 erg s?1 in the 0.5–2 keV band. This will allow ~(1.5–2) × 104 normal galaxies with approximately the same contribution of star-forming and elliptical galaxies to be detected. All galaxies of the X-ray survey are expected to enter into the existing far-infrared (IRAS) or near-infrared (2MASS) catalogs; the sample of star-forming galaxies will be approximately equivalent in sensitivity to the sample of star-forming galaxies in the IRAS catalog of infrared sources. Thus, a large homogeneous sample of normal galaxies with measured X-ray, near-infrared, and far-infrared fluxes will be formed. About 90% of the galaxies in the survey are located within ~200–400 Mpc. A typical (most probable) galaxy will have a luminosity log L X ~ 40.5–41.0, will be located at a distance of ~70–90 Mpc, and will be either a star-forming galaxy with a star formation rate of ~20M ⊙ yr?1 whose X-ray emission is produced by ultraluminous X-ray sources (ULXs) or an elliptical galaxy with amass log M * ~ 11.3 emitting through to a hot interstellar gas. The galaxies within 35 Mpc will collectively contain ~102 ULXs with luminosities log L X > 40, ~80% of whichwill be the only luminous source in the galaxy. Thus, although the angular resolution of the eROSITA telescope is too low for the luminosity function of compact sources in galaxies to be studied in detail, the survey data will allow one to investigate its bright end and, possibly, to impose constraints on the maximum luminosity of ULXs. 相似文献
4.
Elchanan Almoznino & Noah Brosch 《Monthly notices of the Royal Astronomical Society》1998,298(3):920-930
We selected samples of late-type dwarf galaxies in the Virgo cluster with H i information. The galaxies were observed at the Wise Observatory using several broad-band and Hα bandpasses. UV measurements were carried out with the IUE Observatory from VILSPA, and with the FAUST shuttle-borne UV telescope. We describe the observations in detail, paying particular attention to the determination of measurement errors, and present the observational results together with published data and far-infrared information from IRAS . The sample will be analysed in subsequent papers, in order to study star formation mechanisms in galaxies. 相似文献
5.
S. Johnston R. Taylor M. Bailes N. Bartel C. Baugh M. Bietenholz C. Blake R. Braun J. Brown S. Chatterjee J. Darling A. Deller R. Dodson P. Edwards R. Ekers S. Ellingsen I. Feain B. Gaensler M. Haverkorn G. Hobbs A. Hopkins C. Jackson C. James G. Joncas V. Kaspi V. Kilborn B. Koribalski R. Kothes T. Landecker A. Lenc J. Lovell J.-P. Macquart R. Manchester D. Matthews N. McClure-Griffiths R. Norris U.-L. Pen C. Phillips C. Power R. Protheroe E. Sadler B. Schmidt I. Stairs L. Staveley-Smith J. Stil S. Tingay A. Tzioumis M. Walker J. Wall M. Wolleben 《Experimental Astronomy》2008,22(3):151-273
6.
本文介绍了云南天文台一米望远镜附属的一台低色散光谱仪实验装置,介绍了该装置的设计原理、系统结构参数及试观测情况,并讨论了存在的问题和解决问题的设想。我们已用该装置观测到19m左右的具有大红移的类星体光谱。该类低色散光谱仪,将为我国星系研究工作者提供实测条件。 相似文献
7.
J. Stuart B. Wyithe Abraham Loeb Brian P. Schmidt 《Monthly notices of the Royal Astronomical Society》2007,380(3):1087-1097
Reionization is thought to be dominated by low-mass galaxies, while direct observations of resolved galaxies probe only the most massive, rarest objects. The cross-correlation between fluctuations in the surface brightness of the cumulative Lyα emission (which serves as a proxy for the star formation rate) and the redshifted 21-cm signal from neutral hydrogen in the intergalactic medium (IGM) will directly probe the causal link between the production of ionizing photons in galaxies and the reionization of the IGM. We discuss the prospects for detecting this cross-correlation for unresolved galaxies. We find that on angular scales ≲10 arcmin detection will be practical using wide-field near-infrared (near-IR) imaging from space in combination with the forthcoming Mileura Wide-field Array – Low Frequency Demonstrator. When redshifted 21-cm observations of the neutral IGM are combined with space-based near-IR imaging of Lyα emission, the detection on angular scales ≲3 arcmin will be limited by the sensitivity of the 21-cm signal, even when a small-aperture optical telescope (∼2 m) and a moderate field of view (∼10 deg2 ) are used. On scales ≳3 arcmin, the measurement of cross-correlation will be limited by the accuracy of the foreground sky subtraction. 相似文献
8.
《New Astronomy》2016
Gravitational wave bursts in the formation of neutron stars and black holes in energetic core-collapse supernovae (CC-SNe) are of potential interest to LIGO-Virgo and KAGRA. Events nearby are readily discovered using moderately sized telescopes. CC-SNe are competitive with mergers of neutron stars and black holes, if the fraction producing an energetic output in gravitational waves exceeds about 1%. This opportunity motivates the design of a novel Sejong University Core-CollapsE Supernova Survey (SUCCESS), to provide triggers for follow-up searches for gravitational waves. It is based on the 76 cm Sejong university telescope (SUT) for weekly monitoring of nearby star-forming galaxies, i.e., M51, M81-M82 and blue dwarf galaxies from the unified nearby galaxy catalog with an expected yield of a few hundred per year. Optical light curves will be resolved for the true time-of-onset for probes of gravitational waves by broadband time-sliced matched filtering. 相似文献
9.
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
10.
O. Boulade 《Experimental Astronomy》1998,8(1):25-29
We present in this paper a project for a 1 square degree 16k x 16k CCD camera for the prime focus of the 3.6m CFH telescope on the Mauna Kea mountain. This camera will be used to make a deep multicolor survey of about 100 square degrees, with scientific applications ranging from studies of the solar neighborhood and the galactic structure to studies of the large scale structure of the universe or the weak lensing of galaxies by dark matter. 相似文献
11.
In this paper the search for optical identifications in the 5C-radio surveys is continued. Near the positions of 135 radio sources of the 5C3 catalogue all present optical objects up to the plate limit (about B ≈︁ 21) have been measured photometrically in UBVr and astrometrically on plates of the 134/200 cm Schmidt telescope of the Karl Schwarzschild Observatory Tautenburg. A total of 111 candidates for possible optical identifications were found. The number of real identifications will be, of course, much smaller. Among the 111 objects there are: 12 supposed QSO's, 21 galaxies or probable galaxies, 56 stellar objects the greater part of which may be main sequence stars, subdwarfs and white dwarfs, and I object may be the centre of an H II region in the OB-association OB 182. 21 objects near the plate limit could not be classified. A statistical treatment with information on the real rate of identification (it roughly will amount to about 10%) and its reliability will be given in part III. 相似文献
12.
13.
Nario Kuno Akihiko Hirota Tomoka Tosaki Rie Miura 《Astrophysics and Space Science》2008,313(1-3):293-296
We present recent results of the observations of giant molecular clouds in nearby galaxies with the Nobeyama 45 m telescope
and Millimeter Array. We give some brief comments about observations of GMCs in nearby galaxies with ALMA. 相似文献
14.
《Chinese Astronomy and Astrophysics》1982,6(1):68-75
Two southern radio galaxies 1331-09 and 1417-20 have been observed with the Fleurs synthesis radio telescope at 1415 MHz. The deduced geometrical and physical parameters show that 1331-09 is a giant radio galaxy having two outer components extending 1.9 Mpc and a central component coinciding with its optical counterpart. Many similarities of its features to CygA suggest that hot spots structure at the outer edge of its components should be expected in a higher resolution map. The source 1417-20 is a rather typical radio galaxy with halo-nucleus structure. 相似文献
15.
K. Golap N. Udaya Shankar S. Sachdev R. Dodson Ch. V. Sastry 《Journal of Astrophysics and Astronomy》1998,19(1-2):35-53
A new, meter-wave radio telescope has been built in the north-east of Mauritius, an island in the Indian Ocean, at a latitude
of -20.14‡. The Mauritius Radio Telescope (MRT) is a Fourier Synthesis T-shaped array, consisting of a 2048 m long East-West
arm and an 880 m long South arm. In the East-West arm 1024 fixed helices are arranged in 32 groups and in the South arm 16
trolleys, with four helices on each, which move on a rail are used. A 512-channel digital complex correlation receiver is
used to measure the visibility function. At least 60 days of observing are required for obtaining the visibilities up to 880
m spacing. The Fourier transform of the calibrated visibilities produces a map of the area of the sky under observation with
a synthesized beam width 4′ × 4.6′ sec(δ + 20.14‡) at 151.5 MHz.
The primary objective of the telescope is to produce a sky survey in the declination range –70‡ to –10‡ with a point source
sensitivity of about 200 mJy (3a level). This will be the southern sky equivalent of the Cambridge 6C survey. In this paper
we describe the telescope, discuss the array design and the calibration techniques used, and present a map made using the
telescope. 相似文献
16.
Detecting mass substructure in galaxy clusters: an aperture mass statistic for gravitational flexion
Adrienne Leonard Lindsay J. King Stephen M. Wilkins 《Monthly notices of the Royal Astronomical Society》2009,395(3):1438-1448
Gravitational flexion has been introduced as a technique by which one can map out and study substructure in clusters of galaxies. Previous analyses involving flexion have measured the individual galaxy–galaxy flexion signal, or used either parametric techniques or a Kaiser, Squires and Broadhurst (KSB)-type inversion to reconstruct the mass distribution in Abell 1689. In this paper, we present an aperture mass statistic for flexion, and apply it to the lensed images of background galaxies obtained by ray-tracing simulations through a simple analytic mass distribution and through a galaxy cluster from the Millennium Simulation. We show that this method is effective at detecting and accurately tracing structure within clusters of galaxies on subarcminute scales with high signal to noise even using a moderate background source number density and image resolution. In addition, the method provides much more information about both the overall shape and the small-scale structure of a cluster of galaxies than can be achieved through a weak lensing mass reconstruction using gravitational shear data. Lastly, we discuss how the zero-points of the aperture mass might be used to infer the masses of structures identified using this method. 相似文献
17.
18.
Subhashis Roy Sharanya Sur Kandaswamy Subramanian Arun Mangalam T. R. Seshadri Hum Chand 《Journal of Astrophysics and Astronomy》2016,37(4):42
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
19.
Fei Shi Xu Kong Fu-Zhen Cheng Center for Astrophysics University of Science Technology of China Hefei National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2006,6(6):641-648
Based on a sample of 72 Blue Compact Galaxies (BCGs) observed with the 2.16m telescope of the National Astronomical Observatories, Chinese Academy of Sciences (NAOC) and about 4000 strong emission line galaxies from the Sloan Digital Sky Survey, we analyzed their chemical evolution history using the revised chemical evolution model of Larsen et al. Our sample covers a much larger metallicity range (7.2 < 12 log(O/H) < 9.0). We found that, in order to reproduce the observed abundance pattern and gas fraction over the whole metallicity range, a relatively continuous star formation history is needed for high metallicity galaxies, while assuming a series of instantaneous bursts with long quiescent periods (some Gyrs) for low metallicity galaxies. Model calculations also show that only the closed-box model is capable of reproducing the observational data over the whole metallicity range. Models that consider the ordinary winds and/or inflow can only fit the observations in the low metallicity range, and a model with enriched wind cannot fit the data in the whole metallicity range. This implies that the current adopted simple wind and inflow models are not applicable to massive galaxies, where the underlying physics of galactic winds or inflow could be more complicated. 相似文献
20.
We present evidence for non-Gaussian velocity fields within the cores of luminous elliptical galaxies. This evidence is based on high signal-to-noise ratio, medium-resolution spectroscopy of the cores of early-type members of the Virgo and Coma Clusters obtained with the Wisconsin-Indiana-Yale-NOAO 3.5 m telescope. The Virgo data were acquired using an integral-field unit (DensePak), which allows the velocity field to be sampled over a variety of spatial scales. The Coma data were obtained through single 2&arcsec; diameter fibers. The cross-correlation profiles of luminous elliptical galaxies show considerable structure, often having several features with amplitudes as high as 10% that of the cross-correlation peak itself. This structure is most obvious within a radius of 1&farcs;5 (at Virgo), or =100 pc, and is nearly undetectable when the data are binned over R<15", or =1 kpc. Similar features are found in the single-fiber spectra of the luminous elliptical galaxies in the Coma Cluster, suggesting that they are ubiquitous in giant elliptical galaxies. Interestingly, only the most luminous elliptical galaxies show these phenomena; the central regions of lower luminosity elliptical galaxies have regular Gaussian-like profiles. We interpret this kinematic structure as "stellar streaming" and suggest that these phenomena could be a relic signature of the merger history of luminous elliptical galaxies. 相似文献