共查询到19条相似文献,搜索用时 390 毫秒
1.
用澳大利亚悉尼大学的Fleurs综合孔径射电望远镜,在1415MHz上对两个南天射电星系PKS1331-09和PKS1417-20进行了观测,得到了分辨率约为40弧秒的射电亮度分布图,并求得了它们的几何参数和物理参数.前者是一个延伸达1.9 Mpc的巨射电星系,具有与CygA十分相似的双源结构.我们猜测用更高分辨率观测该源时,可期望在它的子源外边沿发现热斑结构;后者是一通常的晕核结构源. 相似文献
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用4km Ooty综合孔径射电望远镜,来研究Abell星系团A514在326.5MHz上的射电结构。该文给出了A514星系团中四个射电星系(射电源)的射电图,并作了初步分析,得出射电星系的某些结构特性及其物理参数。 相似文献
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本文介绍了高红移射电星系近年来的研究进展。新的天文观测手段和技术方法的发展,导致了一批高红移射电星系的发现。多波段的联合研究,揭示了出高红移射电星系光学/红外辐射与射电结构之间的成协现象。开发这些亮而远的射电星系研究有助于我们了解早期的演2化及星系活动的内在原因。 相似文献
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本文叙述用荷兰威斯特堡3公里基线射电望远镜对射电星系3C390.3进行的0.6京赫射电观测。3C390.3是一个边缘增亮型双子源射电源,在热斑与中心核源之间有强的桥状结构把二者连接起来。观测到复杂的线偏振结构:南部子源有双重结构,北部子源有三重结构。本文还把新观测与1.5公里基线1.4京赫的观测进行了比较,从而导出了源区一些重要的物理参数。 相似文献
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从射电结构的角度评述了BLLac天体和FR-I射电星系的统一模型的最新进展,内容包括射电结构,延展射电光度(Pext),最大角尺度(LAS),射电核主导系数(f)的比较以及对相对论聚束的测试。最新的射电观测资料表明XBLs是介于FR-I和RBLs之间的过渡型天体,这对BLLac天体是聚束的FR-I射电星系提供了一个很好的证据。 相似文献
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利用30颗左右射电星的光学和射电位置,在坐标和自行系统、参考星表及位置历元统一的基础上,得到了光学系统与射电系统间的转动参数的初步结果。 相似文献
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云南天文台高分辨率射电频谱仪观测到10毫秒级变周期振荡,带宽约10MHz,叠加在一个持续时间约500ms的射电频谱上.在德国Weissenau的太阳射电频谱记录上找到了对应的爆发;同时SESC(美国空间环境服务中心)发表了同一时刻获得的245MHz总强度射电爆发记录;还在日面城到了相应的H_α亮点. 相似文献
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1991年3月,我们利用上海25m射电望远镜和欧洲VLBI网联合对几个河外射电源进行了第二历元的327MHzVLBI观测.数据的相关处理先后在上海天文台三台站MK2相关处理机和美国的Caltech/JPL相关处理机进行,以便于比较相关结果。本文给出3C84、3C345和3C380的混合图。与第一历元的观测比较,3C345和3C380的流量密度没有明显的变化,但3C345的结构变化明显。3C84和3C345有喷流的迹象.3C454.3的总流量在不到两年的时间内增加了25%,如果这个变化是内禀的话,那么可能意味着一次新的流量爆发。 相似文献
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C. H. Ishwara-Chandra S. K. Sirothia Y. Wadadekar S. Pal 《Journal of Astrophysics and Astronomy》2011,32(4):609-612
Most of the radio galaxies with z > 3 have been found using the red-shift spectral index correlation. We have started a programme with the Giant Metrewave
Radio Telescope (GMRT) to exploit this correlation at flux density levels about 100 times deeper than the known high-redshift
radio galaxies, with an aim to detect candidate high-redshift radio galaxies. Here we present results from the deep 150 MHz
observations of LBDS-Lynx field, which has been imaged at 327, 610 and 1412 MHz with the Westerbork Synthesis Radio Telescope
(WSRT) and at 1400 and 4860 MHz with the Very Large Array (VLA). We find about 150 radio sources with spectra steeper than
1. About two-thirds of these are not detected in Sloan Digital Sky Survey (SDSS), hence are strong candidate high-redshift
radio galaxies, which need to be further explored with deep infra-red imaging and spectroscopy to estimate the red-shift. 相似文献
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M. Vivekanand 《Monthly notices of the Royal Astronomical Society》2002,332(1):55-58
Seven giant radio pulses were recorded from the millisecond pulsar PSR B1937+21 during ≈8.1 min observation by the Ooty Radio Telescope (ORT) at 326.5 MHz. Although sparse, these observations support most of the giant pulse behaviour reported at higher radio frequencies (430 to 2380 MHz). Within the main component of the integrated profile, they are emitted only in a narrow (≲47 μs) window of pulse phase, close to its peak. This has important implications for doing super-high precision timing of PSR B1937+21 at low radio frequencies. 相似文献
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S. Sukumar 《Journal of Astrophysics and Astronomy》1987,8(4):281-294
The refraction of radio waves as they traverse through the terrestrial ionosphere and troposphere introduces a differential
phase path which results for a radio interferometer in variations of the visibility phase. Though refraction due to troposphere
is significant for synthesis radio telescopes operating at 1.0 GHz and above, ionospheric refraction is dominant at lower
frequencies. This problem is important in the case of Ooty Synthesis Radio Telescope (OSRT) operating at 326.5 MHz, due to
its proximity to the magnetic equator. This paper deals with the nature of phase variations suffered by OSRT due to refraction
and explains the methodology evolved to alleviate them. 相似文献
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Prospects for Detecting the 326.5 MHz Redshifted 21-cm HI Signal with the Ooty Radio Telescope (ORT)
Observations of the redshifted 21-cm HI fluctuations promise to be an important probe of the post-reionization era (z≤ 6). In this paper we calculate the expected signal and foregrounds for the upgraded Ooty Radio Telescope (ORT) which operates at frequency ν o = 326.5 MHz which corresponds to redshift z = 3.35. Assuming that the visibilities contain only the HI signal and system noise, we show that a 3 σ detection of the HI signal (~1 mK) is possible at angular scales 11′ to 3° with ≈1000 h of observation. Foreground removal is one of the major challenges for a statistical detection of the redshifted 21 cm HI signal. We assess the contribution of different foregrounds and find that the 326.5 MHz sky is dominated by the extragalactic point sources at the angular scales of our interest. The expected total foregrounds are 104?105 times higher than the HI signal. 相似文献
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Taufiq Hidayat Achmad Munir Budi Dermawan Anton Timur Jaelani Stéphane Léon Dading Hadi Nugroho Andriyan Bayu Suksmono Putra Mahasena Premana Wardayanti Premadi Dhani Herdiwijaya Chatief Kunjaya Zadrach Ledoufij Dupe Budi Brahmantyo Denny Mandey Muhammad Yusuf Hesti Retno Tri Wulandari Falahuddin Arief Muhammad Irfan Agus Triono Puri Jatmiko Evan Irawan Akbar Hery Leo Sianturi Jehunias Leonidas Tanesib Ali Warsito Judhistira Aria Utama 《Experimental Astronomy》2014,37(1):85-108
We report the first measurements of radio frequency spectrum occupancy performed at sites aimed to host the future radio astronomy observatory in Indonesia. The survey is intended to obtain the radio frequency interference (RFI) environment in a spectral range from low frequency 10 MHz up to 8 GHz. The measurements permit the identification of the spectral occupancy over those selected sites in reference to the allocated radio spectrum in Indonesia. The sites are in close proximity to Australia, the future host of Square Kilometre Array (SKA) at low frequency. Therefore, the survey was deliberately made to approximately adhere the SKA protocol for RFI measurements, but with lower sensitivity. The RFI environment at Bosscha Observatory in Lembang was also measured for comparison. Within the sensitivity limit of the measurement equipment, it is found that a location called Fatumonas in the surrounding of Mount Timau in West Timor has very low level of RFI, with a total spectrum occupancy in this measured frequency range being about 1 %, mostly found at low frequency below 20 MHz. More detailed measurements as well as a strategy for a radio quiet zone must be implemented in the near future. 相似文献
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The results of flux pulsar radioemission measurements at meter wavelengths, made at Pushchino Radio Astronomical Observatory
of the Lebedev Physical Institute, are presented. Flux densities at 102, 85, 61 and 39 MHz have been measured for 85, 29,
37 and 23 pulsars correspondingly. Some of them were performed at all frequencies simultaneously.
On the basis of these data and high frequencies data obtained by other authors, spectra of 52 pulsars were plotted. In practically
all investigated pulsars we have detected a turn-over frequency at which the flux density of pulsar radioemission attained
its maximum. Its mean value isv
m
=130±80 MHz. Averaged on many pulsars, the spectral index is negative in the 39–61 MHz frequency range
and passes through zero at frequencies of about 100 MHz, becoming positive in the 100–400 MHz frequency range. It was noticed
that the spectral index in the 100–400 MHz interval depends upon such pulsar periods as α100−=0.7logp+0.9. Using the spectra, more precise radio luminosities of pulsars have been computed. 相似文献
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A new solar radio spectrograph to observe solar radio bursts has been installed at the Ichon branch of the Radio Research
Laboratory, Ministry of Information and Communication, Korea. The spectrograph consists of three different antennas to sweep
a wide band of frequencies in the range of 30 MHz ∼ 2500 MHz. Its daily operation is fully automated and typical examples
of solar radio bursts have been successfully observed. In this paper we describe briefly its hardware and data processing
methods. Then we present coronal shock speeds estimated for 34 type II bursts from May 1998 to November 2000 and compare them
with those from other observatories. We also present the close relationship between onset time of type II bursts and X-ray
flares as well as their associations with coronal mass ejections. 相似文献