MERLIN Data Research Articles

High-resolution observations of eight 3CR compact steep-spectrum radio sources

We present high-resolution observations carried out at 18-cm wavelength with MERLIN and the European VLBI Network (EVN) on eight compact steep-spectrum (CSS) sources from the 3CR catalogue (3C43, 186, 190, 286, 299, 318, 346, 454). The typical resolution achieved on maps made with combined data is ≲ 30 mas. The relationships between compact features on these maps with low-brightness extended regions seen in the MERLIN data alone can be found. Prominent jets were found in seven sources, enabling us to discuss the properties of jets for the 3CR sample of CSS sources in general. The jet opening angle is similar to that in large-scale powerful radio sources, but several jets show pronounced curvature and bending perhaps indictive of strong interactions with an interstellar medium. The jet/counter-jet brightness ratios are consistent with moderate |$(\beta \gtrsim 0.7)$| Doppler boosting.

Sensitive VLA observations of OH 127.8 - 0.0 and OH 26.5 + 0.6

view Abstract Citations (42) References (37) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Sensitive VLA Observations of OH 127.8-0.0 and OH 26.5+0.6 Bowers, P. F. ; Johnston, K. J. Abstract VLA maps with the highest signal-to-noise ratio and dynamic range thus far observed for OH/IR stars are presented throughout the velocity range of the outer envelopes for the bright 1612 MHz sources OH 127.8 - 0.0 and OH 26.5 + 0.6. The maps are compared to VLBI and MERLIN data, and the shell parameters are determined to the highest accuracy obtainable with the assumptions of the standard expanding shell model. The linear radius of the maser shell of OH 127.8 - 0.0 is constant to within + or - 10 percent (rms) as a function of direction from the star, but that of OH 26.5 + 0.6 differs by as much as 50 percent on opposite sides of the shell, possibly because of excess ultraviolet radiation contributed by an O8 star in its vicinity. The extent to which rotational components, radial acceleration, or random velocity fluctuations may be present in the envelopes is considered. OH 127.8 - 0.0 appears to be a supergiant star, but its OH profile and light curve are unlike those of known supergiants. Publication: The Astrophysical Journal Pub Date: May 1990 DOI: 10.1086/168724 Bibcode: 1990ApJ...354..676B Keywords: Infrared Stars; Interstellar Masers; Very Large Array (Vla); Continuous Radiation; Hydroxyl Radicals; Signal To Noise Ratios; Stellar Envelopes; Astrophysics; INFRARED: SOURCES; INTERFEROMETRY; MASERS; STARS: CIRCUMSTELLAR SHELLS full text sources ADS | data products SIMBAD (2)

The Radio Structures of the Compact Steep Spectrum Sources 3C119, 3C287 and 3C343

The compact steep spectrum radio sources, 3C119, 3C287 and 3C343, are identified with QSO'S of redshift 0.46, 1.055 and 0.988 and visual magnitude 20.0, 17.7 and 20.6 respectively. The overall physical extent of each source is −500 pc (Fanti et al. 1985, 1986). Here we present the results of new global VLBI 18 cm observations which have been combined with MERLIN data to improve the U-V coverage. The data were mapped using the CALTECH and AIPS software packages and also using OLAF software system developed in Jodrell Bank for 3C119 and 3C343.

Radiative transfer in circumstellar 1612 MHz OH masers

A detailed investigation of radiative transfer in the 1612 MHz OH maser in the expanding envelopes around evolved stars is made in the context of the standard model in which the mass outflow is windlike. The most sensitive diagnostic of the models is the maser emission at the velocity of the star for which VLA and MERLIN data exist. Fully saturated models are analytically eliminated. Detailed numerical modeling also eliminates partially saturated models. The need to examine alternative models for the mass outflow is suggested by this conclusion. A model for the mass outflow from these stars is advocated in which all mass is lost by the ejection of blobs of material. These blobs, acted on by radiation pressure on grains, evolve into platelike structures in the OH maser region. It is shown that the peculiar difficulties of the standard model for the OH masers do not occur in this picture.