The details of low-frequency (< 1 GHz) observing and data reduction for the VLA are sufficiently different from the steps described in the AIPS Cookbook that we have developed this site. Moreover, the low-frequency systems at the VLA, particularly the 74 MHz system, are sufficiently new that we are still learning about them. Expect updates!
Synposis of low-frequency data reduction; useful for those who need a quick reminder.
Low-Frequency Data Reduction at the VLA: A Tutorial for New Users; Cookbook-style description of how to reduce low-frequency data (also available in PostScript)
Source models in FITS format. (Check their epoch! Use IMHEADER and EPOSWTCH, if necessary!)
| Source | 74 MHz | 330 MHz |
|---|---|---|
| Cygnus A | model | model |
| Cassiopeia A | model | model |
| Virgo A | model | |
| 3C 123 | model | |
| Taurus A | model |
Caveats:
In some cases, these sources are topics of active research. Please do not publish these models without permission.
Models of additional sources are available upon request.
The flux densities of these models (i.e., the total flux density contained in the CC table) are correct on the Baars et al. (1977) flux density scale at the center frequency of observation. Observers using slightly different frequencies (e.g., 327 MHz vs. 330 MHz) should adjust the flux densities accordingly.
This table is a quick reference guide for the sensitivity of the VLA below 1 GHz. It is adapted from the VLA Observational Status Summary section on Sensitivity (q.v.).
| Frequency | Approximate Wavelength | Band Code Name | System Temperature | Antenna Efficiency | RMS Sensitivity in 12 hrs | Untapered Brightness Sensitivity (D-config) | Peak Confusing Source in Beam | Total Confusing Flux in Beam |
| (MHz) | (cm) | (K) | (%) | (mJy/beam) | (K) | (Jy) | (Jy) | |
| 73--74.5 | 400 | 4 | 1000--10000 | 20 | 15 | 0.3 | 20 | 350 |
| 300--340 | 90 | P | 150--180 | 40 | 0.17 | 0.052 | 1.8 | 15 |
| Frequency | Configuration | Primary Beam | |||
| (MHz) | A | B | C | D | (FWHP) |
| 74 | 25" | 1' | 3' | 10' | 700' |
| 330 | 6" | 20" | 1' | 3' | 150' |
Preparing the OBSERVE file.
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