Volume 574, February 2015
|Number of page(s)||9|
|Published online||30 January 2015|
Brightness temperature constraints from interferometric visibilities
1 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
2 Institut für Experimentalphysik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
Received: 30 September 2014
Accepted: 4 December 2014
Context. The brightness temperature is an effective parameter that describes the physical properties of emitting material in astrophysical objects. It is commonly determined by imaging and modeling the structure of the emitting region and estimating its flux density and angular size.
Aims. Reliable approaches for visibility-based estimates of brightness temperature are needed for interferometric experiments in which poor coverage of spatial frequencies prevents successful imaging of the source structure, for example, in interferometric measurements made at millimeter wavelengths or with orbiting antennas.
Methods. Such approaches can be developed by analyzing the relations between brightness temperature and visibility amplitude and its rms error.
Results. A method is introduced for directly calculating the lower and upper limits of the brightness temperature from visibility measurements. The visibility-based brightness temperature estimates are shown to agree well with the image-based estimates obtained in the 2 cm MOJAVE survey and the 3 mm CMVA survey, with good agreement achieved for interferometric measurements at spatial frequencies exceeding ≈ 2 × 108.
Conclusions. The method provides an essential tool for constraining brightness temperature in all interferometric experiments with poor imaging capability.
Key words: galaxies: jets / techniques: interferometric / methods: analytical
© ESO, 2015
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