ALMA

Description

The alma sub-system allows access to flux densities for continuum calibration.

It relies on the latest alma_calibrator.csv file installed in "$LINUXPOPS_HOME"/share directory as alma_calibrators.dat.

Every effort to keep this rapidly changing database up to date is made. Users who have their own installation of Linuxpops will need to manage these updates.

Updating The Catalog

Here is the alma.README located in the ~linuxpops/share directory.

To update the ALMA calibrator catalog:
cd linuxpops/share   (this directory)
Rename current catalog: alma_calibrators.dat to: alma_calibrators-Mar-2020.dat 
(for instance)
Move the newly renamed catalog: alma_calibrators-Mar-2020.dat along with the 
alma_sourcecat_searchresults-Mar-2020.csv file to old_alma_catalogs.
Download the latest catalog from here: https://almascience.eso.org/sc/
In the query form leave all fields blank except:
Flux Density: > 3.0
After: 2011-06-01
Before: 20xx-12-31  ( The end of the current year)
Set the 'Download' type to csv and hit Download
Rename to catalog:
mv alma_sourcecat_searchresults.csv alma_sourcecat_searchresults-Mar-2021.csv
Now run parser: 
./parse_alma_catalog.csh alma_sourcecat_searchresults.csv > alma_calibrators.dat
In linuxpops: Linuxpops(C) >> alma reload 
to see if there are any errors in parsing the new catalog
                                                                         
NOTE: Currently, the maximum number of catalog entries is defined as:
#define MAX_ALMA_CALIBRATORS 12480
As of this writing, March 2021, the ALMA catalog is up to 8757 entries.
If the catalog starts to get too big, you can change the above search
criteria to make the 'After' field a year later to remove the earlier
entries.  If the historical flux values are important, then change the
define in alma.c to a larger value and recompile.

Reference

From the ALMA Web Site: https://almascience.eso.org/alma-data/calibrator-catalogue

The ALMA Calibrator Source Catalog is a database of astronomical measurements of calibrator sources, mostly bright quasars in the mm and sub-mm regime. It contains over 11000 ALMA measurements of over 1800 sources (1 July 2015). The most important properties are flux density with uncertainty at a given frequency and angular structure information or limits, and polarization measurements for some calibrators. External information had been provided via 'seed' catalogs, such as from VLA (Calibrator Manual), SMA1, ATCA, CRATES, and coordinates from VLBI, and we acknowledge the institutions and individuals who contributed this effort. Note that the absolute flux density scale does not include the model uncertainty of the solar system object used as primary amplitude calibrator, and in some cases it can exceed the stated flux density error in the catalog. Also, the observation and reduction procedures changed in mid-2012, so the measurements before this date may state flux density errors that underestimate the true uncertainty.

A main use of the database is to allow the selection of bandpass and phase calibrators for science observations. It also contains a set of 30 quasars, grid sources evenly distributed over the sky, which are monitored regularly enough to provide amplitude calibration in addition to solar system objects. Calibrator sources are selected either manually during phase 2 preparation or by the astronomer on duty, or automatically via on-line queries during the execution of themobservation. In each case suitable criteria regarding visibility, flux density and proximity to the science targets have to be specified.

Usage

You may obtain the flux density of a calibrator source by typing just 'alma' and if the currently selected source matches one of the calibrators, then a listing of all measurements is displayed. If your current source is not a calibrator an error message will appear.

Commands

    - alma [source]
            - Produce a text listing of flux densities for the currently selected source or the named source.
              The listing will be frequency band limited.

    - alma plot xxx.x
            - Produce a time series of flux density for the currently selected source.
            - xxx.x is the freq of interest.
                    - Choices are:
                            - 90, 100
                            - 220 - 290 by 10
                            - 340, 350
                            - 673
                            - 898

    - alma sort [name | date | freq | jansky]
            - Sort the catalog by the named field.

    - alma catalog
            - Produce a ARO source catalog from the currently selected band.

    - alma all
            - List all sources and calibrations for any measurement falling into the currently selected ALMA band.

    - alma reload
            - Reload the alma_calibrators.dat file.

Plotting:

Plot flux density for 3C94 @ 90 GHz.

    alma plot 90