VALD is a collection of atomic and molecular transition parameters. While VALD originally focused on data that is of interest to the astrophysical community, the database is now used across many fields.
VALD is regularly updated with critically evaluated data sets. The VALD project team experts investigate the statistical properties of the data, extensively compare the data for transitions in common to different sources, and establish a recommended quality rating for each new source which is a basis for data selection.
In addition to atomic and molecular line data VALD offers tools for selecting subsets of data for typical astrophysical applications such as line identification, preparing for spectroscopic observations, chemical composition and radial velocity measurements, and model atmosphere calculations.
Access to the database is provided through both a web portal and an email interface. Data can be extracted in different units, users can create and save alternative ranking tables.
The VALD database was created in 1995 as the « Vienna Atomic Line Database » and aimed at providing the relevant information for atomic transitions significantly contributing to absorption in stellar spectra.
The primary objectives of VALD are to compile accurate and complete lists of spectral lines relevant to stellar atmospheres and spectroscopy, and to evaluate line lists and suggest rankings according to the quality of line data. Further development has focused on creating tools for to end-users to extract data in a format compatible with existing software for the analysis of stellar spectra. While VALD originally focused on data that is of interest to the astrophysical community, the database is now used across many fields.
Methodology for data-
VALD data is collected from a large number of mostly inhomogeneous sources and reformatted into a common data format. Data in each linelist are then vetted by the VALD team such that compilation of line data will yield the best available atomic and molecular data for the calculation of synthetic spectra. This vetting is performed in terms of ranking parameters for the different kinds of transition data present in each linelist (such as wavelengths and oscillator strengths). While the VALD team proposes a standard ranking of data, the end user can also choose different rankings on a personal basis.
Services linked to the database-
Scientific manager: Ulrike Heiter (ulrike.heiter[at]physics.uu.se)
Technical manager: Thomas Marquart (thomas[at]marquart.se)