A meter-wave survey of the sky region north of declination +30{deg} has been carried out with the Miyun Synthesis Radio Telescope (MSRT), Beijing Astronomical Observatory, at 232MHz. It is a moderately deep survey. The observations were made between January 1985 and December 1993. The covered sky area is divided into 156 fields of view. Basically all adjacent fields are separated by 8 degree angular distance. Fields #54, #56, #115, #116, have no data yet. A catalog of 34462 radio sources is given in Table 2. Table3 shows the information on the 152 fields of view.
A meter-wave sky survey of the region north of declination +30deg has been carried out with the Miyun Synthesis Radio Telescope (MSRT) at 232MHz. The Miyun general catalogue (MGC) contains 26957 radio sources except those located in the galactic plane, its electronic version is available now. Completeness and uniformity of the MGC has been discussed recently (Peng et al, 1995AcApS..15..383P). In this paper, we provide evidence of reliability of the MGC by comparing the MSRT data with other published radio catalogues and also by analyzing the reason why part of the detected sources in the MGC could not be recorded by previous surveys.
The magnetic field configurations in several nearby spiral galaxies contain magnetic arms that are sometimes located between the material arms. The nearby barred galaxy M83 provides an outstanding example of a spiral pattern seen in tracers of gas and magnetic field. We analyse the spatial distribution of magnetic fields in M83 and their relation to the material spiral arms. Isotropic and anisotropic wavelet transforms are used to decompose the images of M83 in various tracers to quantify structures in a range of scales from 0.2 to 10kpc. We used radio polarization observations at {lambda}6.2cm and {lambda}13cm obtained with the VLA, Effelsberg and ATCA telescopes and APEX sub-mm observations at 870{mu}m, which are first published here, together with maps of the emission of warm dust, ionized gas, molecular gas, and atomic gas. The spatial power spectra are similar for the tracers of dust, gas, and total magnetic field, while the spectra of the ordered magnetic field are significantly different. As a consequence, the wavelet cross-correlation between all material tracers and total magnetic field is high, while the structures of the ordered magnetic field are poorly correlated with those of other tracers. The magnetic field configuration in M83 contains pronounced magnetic arms. Some of them are displaced from the corresponding material arms, while others overlap with the material arms. The pitch angles of the magnetic and material spiral structures are generally similar. The magnetic field vectors at {lambda}6.2cm are aligned with the outer material arms, while significant deviations occur in the inner arms and, in particular, in the bar region, possibly due to non-axisymmetric gas flows. Outside the bar region, the typical pitch angles of the material and magnetic spiral arms are very close to each other at about 10{deg}. The typical pitch angle of the magnetic field vectors is about 20{deg} larger than that of the material spiral arms. One of the main magnetic arms in M83 is displaced from the gaseous arms similarly to the galaxy NGC6946, while the other main arm overlaps a gaseous arm, similar to what is observed in M51. We propose that a regular spiral magnetic field generated by a mean-field dynamo is compressed in material arms and partly aligned with them. The interaction of galactic dynamo action with a transient spiral pattern is a promising mechanism for producing such complicated spiral patterns as in M83.
We have mapped the dust continuum emission from the molecular cloud covering a region of 28pcx94pc associated with the well-known H II region RCW 106 at 1.2mm using SIMBA on SEST. The observations, having an HPBW of 24" (0.4pc), reveal 95 clumps, of which about 50% have MSX associations and only 20% have IRAS associations. Owing to their higher sensitivity to colder dust and higher angular resolution the present observations identify new emission features and also show that most of the IRAS sources in this region consist of multiple dust emission peaks. The detected millimeter sources (MMS) include on one end the exotic MMS5 (associated with IRAS 16183-4958, one of the brightest infrared sources in our Galaxy) and the bright (and presumably cold) source MMS54, with no IRAS or MSX associations on the other end. Around 10% of the sources are associated with signposts of high mass star formation activity.
Radio flux densities are presented for 118 extragalactic radio sources monitored at 90, 142 and 230GHz with the IRAM 30m telescope during 1993-1994. For the most frequently observed sources we show light curves including 30 m-measurements published in previous papers, Steppe et al. (1988A&AS...75..317S; 1992A&AS...96..441S and and 1993, Cat. <J/A+AS/102/611>)
The MOJAVE blazar sample consists of the 133 brightest, most compact radio-loud AGNs in the northern sky, and it is selected on the basis of VLBA 2cm correlated flux density exceeding 1.5Jy (2Jy for declinations south of 0) at any epoch between 1994 and 2003. Since 1994 we have been gathering VLBA data on the sample to measure superluminal jet speeds and to better understand the parsec-scale kinematics of AGN jets. We have obtained 1.4GHz VLA A configuration data on 57 of these sources to investigate whether the extended luminosity of blazars is correlated with parsec-scale jet speed and also to determine what other parsec-scale properties are related to extended morphology, such as optical emission line strength and gamma-ray emission. We present images and measurements of the kiloparsec scale emission from the VLA data, which will be used in subsequent statistical studies of the MOJAVE sample.
We discuss acceleration measurements for a large sample of extragalactic radio jets from the Monitoring Of Jets in Active Galactic Nuclei with VLBA Experiments (MOJAVE) program, which studies the parsec-scale jet structure and kinematics of a complete, flux-density-limited sample of active galactic nuclei (AGNs). Accelerations are measured from the apparent motion of individual jet features or "components" which may represent patterns in the jet flow. We find that significant accelerations are common both parallel and perpendicular to the observed component velocities.
We discuss the jet kinematics of a complete flux-density-limited sample of 135 radio-loud active galactic nuclei (AGNs) resulting from a 13 year program to investigate the structure and evolution of parsec-scale jet phenomena. Our analysis is based on new 2cm Very Long Baseline Array (VLBA) images obtained between 2002 and 2007, but includes our previously published observations made at the same wavelength, and is supplemented by VLBA archive data. In all, we have used 2424 images spanning the years 1994-2007 to study and determine the motions of 526 separate jet features in 127 jets.
We present 1625 new 15GHz (2cm) VLBA images of 295 jets associated with active galactic nuclei (AGNs) from the MOJAVE and 2cm VLBA surveys, spanning observations between 1994 August 31 and 2013 August 20. For 274 AGNs with at least 5 VLBA epochs, we have analyzed the kinematics of 961 individual bright features in their parsec-scale jets. A total of 122 of these jets have not been previously analyzed by the MOJAVE program. In the case of 451 jet features that had at least 10 epochs, we also examined their kinematics for possible accelerations. At least half of the well-sampled features have non-radial and/or accelerating trajectories, indicating that non-ballistic motion is common in AGN jets. Since it is impossible to extrapolate any accelerations that occurred before our monitoring period, we could only determine reliable ejection dates for ~24% of those features that had significant proper motions. The distribution of maximum apparent jet speeds in all 295 AGNs measured by our program to date is peaked below 5c , with very few jets with apparent speeds above 30c . The fastest speed in our survey is ~50c , measured in the jet of the quasar PKS0805-07, and is indicative of a maximum jet Lorentz factor of ~50 in the parent population. An envelope in the maximum jet speed versus redshift distribution of our sample provides additional evidence of this upper limit to the speeds of radio-emitting regions in parsec-scale AGN jets. The Fermi-LAT-detected gamma-ray AGNs in our sample have, on average, higher jet speeds than non-LAT-detected AGNs, indicating a strong correlation between parsec-scale jet speed and the gamma-ray Doppler boosting factor. We have identified 11 moderate-redshift (z<0.35) AGNs with fast apparent speeds (>10c) that are strong candidates for future TeV gamma-ray detection. Of the five gamma-ray loud narrow-lined Seyfert I AGNs in our sample, three show highly superluminal jet motions, while the others have sub-luminal speeds. This indicates that some narrow-lined Seyfert I AGNs possess powerful jets with Lorentz factors in excess of 10, and viewing angles less than 10{deg}, consistent with those of typical BL Lac objects and flat-spectrum radio quasars.
We describe the parsec-scale kinematics of 200 active galactic nucleus (AGN) jets based on 15GHz Very Long Baseline Array (VLBA) data obtained between 1994 August 31 and 2011 May 1. We present new VLBA 15 GHz images of these and 59 additional AGNs from the MOJAVE and 2cm Survey programs. Nearly all of the 60 most heavily observed jets show significant changes in their innermost position angle over a 12-16yr interval, ranging from 10{deg} to 150{deg} on the sky, corresponding to intrinsic variations of ~0.5{deg} to ~2{deg}. The BL Lac jets show smaller variations than quasars. Roughly half of the heavily observed jets show systematic position angle trends with time, and 20 show indications of oscillatory behavior. The time spans of the data sets are too short compared to the fitted periods (5-12yr), however, to reliably establish periodicity. The rapid changes and large jumps in position angle seen in many cases suggest that the superluminal AGN jet features occupy only a portion of the entire jet cross section and may be energized portions of thin instability structures within the jet. We have derived vector proper motions for 887 moving features in 200 jets having at least five VLBA epochs. For 557 well-sampled features, there are sufficient data to additionally study possible accelerations. We find that the moving features are generally non-ballistic, with 70% of the well-sampled features showing either significant accelerations or non-radial motions. Inward motions are rare (2% of all features), are slow (<0.1mas/yr), are more prevalent in BL Lac jets, and are typically found within 1mas of the unresolved core feature. There is a general trend of increasing apparent speed with distance down the jet for both radio galaxies and BL Lac objects. In most jets, the speeds of the features cluster around a characteristic value, yet there is a considerable dispersion in the distribution. Orientation variations within the jet cannot fully account for the dispersion, implying that the features have a range of Lorentz factor and/or pattern speed. Very slow pattern speed features are rare, comprising only 4% of the sample, and are more prevalent in radio galaxy and BL Lac jets. We confirm a previously reported upper envelope to the distribution of speed versus beamed luminosity for moving jet features. Below 10^26^W/Hz there is a fall-off in maximum speed with decreasing 15GHz radio luminosity. The general shape of the envelope implies that the most intrinsically powerful AGN jets have a wide range of Lorentz factors up to ~40, while intrinsically weak jets are only mildly relativistic.
