nb6. Query by frequency

The relevant columns of the ALMA TAP service are:

Import all necessary modules:

Query observations covering a frequency range

The ALMA archive metadata contain the central frequency of the observations in the frequency column and width of the spectral window in the bandwidth column of each observation. In this function we see which observations do overlap with the frequency range given by the user.

Plot all frequency ranges covered by one source

This function allows the user to read out all frequency ranges covered for one source. To achieve this we need to use the frequency_support column. This column contains strings including the frequency limits of each spectral window within each measurent set, sensivity and polarization information. We will show how to apply this function for a source in example 6b.

Example 6a: Query all 'active galaxies' (science category) with frequencies between 200-400 GHz

Example 6b: Display all frequencies covered for one source

We first need to query all observations available for one specific source. In this example we use the sub-mm galaxy SPT0311-58. This galaxy is not in Sesame (Simbad, NED or VizieR) but has been observed by ALMA:

We can now use the function read_band_freq() to visualize the frequency coverage of each spectral window observed for this source.