A sample of IRAS galaxies with infrared luminosities as high as 1011.8 to 1012.8 L⊙ were observed using the Australia Telescope Compact Array (ATCA) at 8.6, 4.8, 2.4 and 1.4 GHz. 4 galaxies in the sample are found to have steep spectra at high frequency and their flux densities decrease at low frequency, showing a peak-like spectral pattern with the peak flux at several GHz. Two possible mechanisms, synchrotron self-absorption and free-free absorption, for the turning-over in the low-frequency side are discussed. From the analysis of the spectra of the IRAS sources, 00199-7426, 02587-6336, 07020-5423 and 21547-5823, we conclude that free-free absorption may be the cause for the low-frequency turnover. By model fitting to the observations several physical parameters of the sources are obtained.

The quasars, 0420-014, 0748+126 and 2251+158 (3C 454.3), have been observed at 1.3cm with a global VLBI network. We have obtained the hybrid maps of the quasars at sub-milliarcsecond resolution. The brightness distribution is revealed in their nuclear regions. The observed data are fitted with a small number of Gaussian components. 2251+158 shows a core-jet structure, and its nuclear region is elongated in the direction PA = -130 degrees. The jet is curved. Its observations at the epoch 1992.9 show it to be in the course of a large burst, accompanied by several smaller ones. The strongest component has a flux of similar to 4.11 Jy (67% of the total detected flux), mostly from an area of 0.16 x 0.01 mas. Doppler boosting is probably responsible for raising the brightness temperature up to 2.6 x 10(12) K.

使用澳大利亚致密阵 （ATCA）在 1 .4GHz上观测了一个极高光度的IRAS星系样本。在这个样本所包括的 3 7个IRAS星系中 ,探测到 1 9个源的射电发射 ,获得了它们的射电参数 ,如峰值位置 ,射电流量等。该样本的射电功率范围在 2 2 .9＜logP1 .4G（W /Hz） ＜2 3 .8,本文给出了观测的初步结果。

The optical emission from the barred spiral galaxy NGC 7528 shows characteristics of both Seyfert 2 and starburst galaxies. Properties near the central region of the Galaxy are studied with radio and infrared observational data. The result reveals that a violent star formation activity may exist near the center of NGC 7582, and the star formation rate in the region is much higher than that of the Galaxy. Starbursting probably plays an important role in the properties of the Seyfert 2 galaxy.

Six nearby moderately luminous IRAS galaxies have been observed at two wavelengths with the Australia Telescope Compact Array. Radio emission was detected in two of them, IRAS 20272-4738 and IRAS 23156-4238, and their parameters including flux, peak position, size and spectral index, obtained. These sources were confirmed with infrared, radio and optical data. Combining with previous results we discuss their emission characteristics.

A sample of radio sources with ultraluminous infrared luminosity has been observed by using the Australia Compact Array (AT) at multiple wavelengths. The parameters, such as position, flux, spectal index and size, etc, of the radio sources have been obtained. The paper presents our data reduction of the aperture synthesis telescope and mapping method.

We present MERLIN and VLA radio measurements of the Seyfert galaxy NGC 5929 at 15, 8, 5, 1.6 and 0.4 GI-H. All measurements have subarcsecond angular resolution ranging from 0.6 arcsec at 0.4 GHz to 50 mas at 5 GHz, We confirm the triple structure reported in earlier studies. The weak central source of the triplet is almost certainly associated with the active nucleus. It has a flat spectral index and is unresolved even at 50-mas resolution, consistent with a synchrotron-self-absorbed core. The two components which straddle the core have sizes of order 10 pc and have steep spectral indices, and hence can be considered as small radio 'lobes'. Both of these components show evidence for low-frequency turnovers at 0.4 GHz, which we interpret as evidence for free-free absorption by ionized gas with an emission measure of similar to 10(5) pc cm(-6). As the north-eastern component shows greater free-free absorption than the south-western component, we propose that it is behind most of the narrow-line region (NLR) ionized gas, This implies that the nuclear collimated ejection is towards the observer in the south-west and away from the observer in the north-east.There is evidence of weak extended emission, particularly at 0.4 GHz, which may represent flows approximately perpendicular to the central triplet, We compare the radio structure of NGC 5929 to recent HST images and discuss the possible models to relate the radio and optical structures.

Radio observations at 3.6, 6, 18 and 20 cm were made of the late-type giant FK Com using the VLA in US. Emission at mJy level was detected but no circular polarization was found. Fitting with a thermal model was not successful: for an electron density of 9 × 108cm−3 and a temperature of 5 × 107 K, the observed flux would require an emitting radius of 120 R⊙, which seems unlikely, and the predicted X-luminosity in 2 orders of magnitude higher than was observed by the Einstein Observatory. The radio and X luminosities of FK Com are close to those of RS CVn systems. If the radio emission is produced by relativistic electrons, then the observed flux can be produced by a body with a 10 G magnetic field at a radius of 3R⊙.

We used the US VLA to observe the chromospherically active binary UX Ari at five frequencies between 1.4 GHz and 15 GHz. During the period of observation, UX Ari was in a low state of activity with a luminosity of 6.6 ∼ 12.6 × 1016 ergs−1 Hz−1. The low frequency end of the spectrum was rather flat, the high frequency end followed a power law, the degree of circular polarization was almost zero at the low frequency end and was medium strong (15%) at the high frequency end. The emission mechanism is possibly gyrosynchrotron, from which we estimate a magnetic field of a few to a few tens Gauss, a relativistic electron density of the order of 104 ∼ 102 cm−3, and a thermal electron density of 108 cm−3.

Observations at five frequencies in the range 1.4–15 GHz were made using the US VLA on the chromospheric activity type binary HR1099. During the period of observation the source was in the course of a strong flare event, its radio luminosity reached l.8 × 1018erg s−1 Hz−1. As the flux decreased, the spectrum steepened, the spectral inversion frequency decreased and the degree of circular polarization increased towards a medium strong polarization. The direction of circular polarization varied with the frequency. The emission mechanism during the strong flare is probably synchrotron accelerated emission. We found, for the time of the flare, and at optical depth τ ∼ 1, a magnetic field of about 10 G, a mean electron energy of about 4MeV, an electron density of 3–9 × 104 cm−3 and a spectral index of about 1.3 in the power-law electron energy spectrum.

This paper presents images of the compact steep-spectrum quasar 3C 286 obtained with global VLBI arrays at 4.99 and 1.66 GHz. The morphology appears to be intermediate between the core-jet types and grossly distorted objects. The central portion is resolved into two components of almost equal peak brightnesses and spectral indices. On the 1.66 GHz map, the jet extends in position angle approximately -136-degrees, up to a knot (W1) (approximately 75 mas from the component C2) from which it curves rapidly towards the west to form another knot (W2). It is possible that the VLBI jet bends further towards the secondary component separated from the core by approximately 2.6'' in p.a. -115-degrees seen in high dynamic range VLA or Merlin maps. The jet has a sinuous feature shown clearly on the 5 GHz map. There is a low brightness extension at the North ( designated N1) shown on both the 1.66 and 5 GHz maps, which is connected to the component C1 and bends towards the east.

The chromospherically-active binary, V711 Tau, had been observed by using the American Very Large Array (VLA) at five bands from 1.4 to 15 GHz. During the observation, the source was undergoing an intense flare, its radio luminosity up to 1.8 × 1018 erg s−1 Hz−1. The degree of circular polarization in the phase of the most intense flare was very small. With the decaying of the flare the flux density decreased, spectral index became smaller, spectra steeper and reversal frequency lower; the degree of circular polarization increased and its direction was dependent on frequency. These observational facts support the conclusion that the emission during intense flare is synchrotron (or synchro-cyclotron) mechanism. The magnetic intensity is about 10 G nearτ = 1, the average electron energy, 4 MeV, the electron density with larger than 10 keV, 3 × 104−9 × 104 cm−3 and the electronic energy spectrum index in power-law distribution 1.3.