Expected Source Properties
One of the reasons for providing this information is to aid in technical assessment. All relevant items should be filled in or the project will not validate. This means that a continuum flux must be entered for a continuum project and a line flux and width must be filled in for a spectral line project. If full polarization is selected, at least one of the line or continuum polarization percentages must also be given.
- Passive phasing is required: This is only shown for VLBI and Phased Array projects and is used to signify that the total flux of the source being observed is not sufficient to allow phasing of the array using that source and thus that an additional calibrator must be used. The continuum flux limits are 0.35 Jy for Band 1, 0.5 Jy for Band 3 and Band 6, and 0.7 Jy for Band 7. For spectral line observing the flux thresholds are calculated using the formula reported in the Proposer's Guide. If this is selected, a specific ("fixed") phase calibrator must be defined in Calibrator Setup.
- Peak Continuum Flux Density per Synthesized Beam: The expected flux density per synthesized beam of the source continuum. The weakest component that is to be detected should be entered for each source.
- Continuum Linear Polarization: The expected degree of linear polarization for the source, expressed as a percentage of the peak continuum flux. The polarization of the weakest component should be entered. Note that if the polarization percentage is
0.1 per cent, then the OT will issue a validation error as it will not be possible to detect it reliably.
- Continuum Circular Polarization: As above except for circular polarization. A different limit of 1.8 per cent is applied.
- Peak Line Flux Density per Synthesized Beam: The expected peak flux density per synthesized beam of the line emission. The weakest component that is to be detected should be entered for each source. If the line is seen in absorption against a continuum, enter the depth of the line as a positive quantity.
- Line Linear Polarization: The expected degree of linear polarization for the source, expressed as a percentage of the peak line flux. The same polarization limit (0.1 per cent) applies as for continuum.
- Line Circular Polarization: The same as continuum circular polarization, but for spectral lines.
- Line Width: The expected line width for the lines in this Science Goal (FWHM). The narrowest line that is to be detected should be entered for each source. The line width must be in velocity units. This parameter is also shown for VLBI spectral line observing where it is used to ensure that the line falls within the VLBI spectral window.
If observing the sun, there will only be two choices:
To compensate for the sun's prodigious flux density, solar observations will often make use of a special observing mode known as mixer debiasing. Which mode will be used will depend on the level of solar activity and the frequency band.
The ALMA OT Team, 2024 May 21