Spectral line query

Spectral line query#

CARTA supports an initial implementation of spectral line ID overlay on a Spectral Profiler Widget based on the data from the Splatalogue service (https://splatalogue.online).

Makeing a query#

A query can be made by defining a spectral range in frequency or wavelength and, optionally, a lower limit of CDMS/JPL line intensity (logarithmic). The spectral range can be defined as “from-to” or “center-width”. Other filters, such as filtering by species name, energy range, etc., can be applied after the data are retrieved from the Splatalogue. By clicking the “Query” button, molecular data will be retrieved from the Splatalogue service.

Note

The current implementation has some limitations when making a query to the Splatalogue service:

  • The allowed maximum query range, equivalent in frequency, is 20 GHz.

  • The actual query is made with a frequency range in MHz rounded to integer.

  • Only the lines from CDMS and JPL catalogs will be returned when an intensity limit is applied.

  • Up to 100,000 lines are displayed.

  • No “astronomical filters” (e.g., top 20 list, hot cores, etc.) is applied to the query results.

Improvements to the above limitations will be made in future releases.

Once a query is successfully made, the line catalog will be displayed in the tables. The upper table shows the column information in the catalog with options to show or hide a specific column. The actual line catalog is displayed in the lower table. You can use the “Display” toggles in the upper table to show or hide specific columns in the line catalog table.

Filtering and sorting#

The line catalog table accepts a sub-filter for each column such as partial string match or value range. For numeric columns, supported operators are:

  • > : greater than

  • >= : greater than or equal to

  • < : less than

  • <= : less than or equal to

  • == : equal to

  • != : not equal to

  • .. : between (exclusive)

  • ... : between (inclusive)

For examples:

  • To filter everything less than 10, use < 10

  • To filter entries equal to 1.23, use == 1.23

  • To filter everything between 10 and 50 (exclusive), use 10..50

  • To filter everything between 10 and 50 (inclusive), use 10...50

For string columns, a partial match is adopted. For example, CH3 (no quotation) will return entries containing the “CH3” string.

For each column, you can click on the column header to sort the table by that column.

Visualizing line ID overlay#

You can select a set of lines to be overplotted on a Spectral Profiler Widget by checking the checkboxes in the first column of the line table. By clicking the “Plot” button, the selected lines will be displayed by referencing the “Shifted Frequency” column, which is computed based on the user input of a velocity or a redshift. The maximum number of line ID overlays is 1000.

The text labels of the line ID overlay are shown dynamically based on the zoom level of a profile. Different line ID overlays (with different velocity shifts) can be created on different Spectral Profiler Widgets via the “Spectral Profiler” dropdown menu. By clicking the “Clear plot” button, the line ID overlay on the selected Spectral Profiler will be removed.

Note

When there are multiple profiles from different image cubes in the plot, and the x-axis is in velocity, the line ID overlay function is disabled.