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VOTADA: CHIANTI on AstroGrid
How to access the CHIANTI atomic database from AstroGrid
1 The CHIANTI database
The CHIANTI atomic database provides a critically evaluated set of up-to-date atomic data for calculating spectra from astrophysical plasmas. For full details, user guides and references see the CHIANTI Homepage .
The CHIANTI package is written in IDL and is distributed as part of the SolarSoft library.
2 VOTADA
The VOTADA proposal, that was selected in the 2006 AstroGrid Tool Call, aims at providing accurate basic atomic data (and derived products), together with tools for astrophysical applications, within Astrogrid. The broad objective here is to make CHIANTI available to a wide range of astronomers and to allow retrieval of CHIANTI information without the need to use IDL. This objective was achieved by importing CHIANTI information into a relational database, that can be queried from the AstroGrid Workbench.
VOTADA is principally aimed at the interpretation of optically-thin emission from plasmas collisionally excited and in equilibrium, however it also provides basic ion atomic data that are useful for other modelling purposes. VOTADA-CHIANTI includes a subset of the atomic data present in CHIANTI, and some derived products.
The database and examples queries to it are described below. The current version of the database was obtained from CHIANTI Version 5.2. For any questions please contact Giulio Del Zanna (gdz -at- mssl.ucl.ac.uk) or Silvia Dalla (s.dalla -at- manchester.ac.uk).
3 Database Access
Chianti data can be accessed via the AstroGrid Workbench.
- Follow this link for help in downloading and launching the AstroGrid Workbench.
- Once Workbench is running click on the Task Launcher icon.
- Search for 'chianti' . Select 'Datacenter for Chianti' by clicking on the box to the left of the name. Choose adql as the interface. This will take you to the Query Builder.
- See below for example CHIANTI queries and how to run them.
4 The catalogue database
At present the database of CHIANTI information available via AstroGrid consists of two tables: SpectralLines and LineEmissivities. SpectralLines describes the spectral lines part of CHIANTI. Line Emissivities gives the values of the emissivity calculated on a grid of temperatures and densities.
The table SpectralLines contains all the information for each spectral line present in the CHIANTI database. Most importantly, observed and theoretical wavelengths, transition probability, weighted oscillator strength, full spectroscopic notation together with observed and theoretical energies of initial and final levels. Please reference these data as CHIANTI version 5.2 (Landi et al. 2006) and acknowledge usage of AstroGrid to retrieve the information from the VOTADA database. Also, the references found in the CHIANTI files should be cited, whenever appropriate.
In optically-thin plasmas, spectral line intensities are proportional to the 'fractional line emissivity', which is the product of the Einstein A-value and the fractional population of the upper level of the emitting ion. The table LineEmissivities contains the values of the spectral line emissivities calculated for a grid of electron temperatures and densities. The emissivities in the table have been calculated adopting standard options and do not include photo-excitation. Please read the information in the original CHIANTI files for limits of applicability and references to original publications.
The spectral line intensities are also proportional to the ion and element abundances. The ion abundances are currently calculated assuming ionization equilibrium.
Below is a description of columns of SpectralLines
| Name | Description | Units |
|---|---|---|
| LINE_NUMBER | identifier of the line in the database | |
| CHEMICAL_ELEMENT | atomic Z number of the element | |
| IONISATION_STAGE | ionisation stage | |
| ION_TYPE | Type of ion ('d' for dielectronic or 'n') | |
| TITLE | Short description of the line | |
| FINAL_LEVEL_INDEX | index of the lower energy level | |
| INITIAL_LEVEL_INDEX | index of the upper energy level | |
| TRANSITION_TYPE | Type of transition | |
| WAVELENGTH_METERS | Observed vacuum wavelength (0 for 2-photon trans.; Theoretical wavel. if not available) | m |
| THEORETICAL_WAVELENGTH | Theoretical wavelength (0 for two-photon trans.; -1 if not available) | m |
| WEIGHTED_OSCILLATOR_STRENGTH | gf value (weighted oscill. strength, 0 if trans. is not electric-dipole allowed) | |
| EINSTEIN_A | A-value (transition probability) | {s-1} |
| FINAL_LEVEL_CONFIGURATION | Configuration of lower level | |
| FINAL_LEVEL_SPIN | Spin 2S+1 of lower level | |
| FINAL_LEVEL_L | Angular momentum L of lower level | |
| FINAL_LEVEL_J | Total angular momentum J of lower level | |
| FINAL_LEVEL_ENERGY | Observed energy of lower level | cm^{-1} |
| FINAL_LEVEL_THEORETICAL_ENERGY | Theoretical energy of lower level (-1 if not available) | |
| INITIAL_LEVEL_CONFIGURATION | Configuration of upper level | |
| INITIAL_LEVEL_SPIN | Spin 2S+1 of upper level | |
| INITIAL_LEVEL_L | Angular momentum L of upper level | |
| INITIAL_LEVEL_J | Total angular momentum J of upper level | |
| INITIAL_LEVEL_ENERGY | Observed energy of upper level (-1 if not available) | cm^{-1} |
| INITIAL_LEVEL_THEORETICAL_ENERGY | Theoretical energy of upper level (-1 if not available) | |
| COMMENT | References to papers, comments |
5 Example queries
Once the Query Builder appears, click on the Adql/s tab. Now you can type in your query as a string. For example this query:
Select * From SpectralLines as t1 where t1.WAVELENGTH_METERS > 0.000000018 and t1.WAVELENGTH_METERS < 0.000000020
returns all lines in the database with wavelength in the required range. (Note: exponential notation can be used eg 1.8E-08 but will give some error messages in the query builder - will be fixed soon).
Once you finished typing in your query hit return.
To submit the query click on the green icon. This will open a Lookout window.
To view the results launch Topcat . Then in the Lookout window put your mouse over 'Result' in the bottom right corner and choose 'To Topcat' 'as Votable'.
The database of CHIANTI spectral data available via AstroGrid allows retrieval of lines and emissivity information in a single query:
Select * From SpectralLines as a, LineEmissivities as b where a.WAVELENGTH_METERS > 0.000000018 and a.WAVELENGTH_METERS < 0.000000020 and a.LINE_NUMBER=b.LINE_NUMBER AND b.LOG_DENSITY=10.0 and b.LOG_TEMPERATURE=5.0
Here emissivities for lines in the given wavelength range are retrieved for the specified values of the log of the density (cm^{-3}) and log of temperature (Kelvin).
- The Figure below shows the query in the Query Builder
The Figure below shows the result VoTable containing spectral line and emissivity information.
