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Dubernet, M. L., Debray, B., Grosjean, A., Bruston, M., Combes, F., Cornille, M., Egret, D., Stéhlé, C., Tchang-Brillet, L., & Zeippen, C. 2003, in ASP Conf. Ser., Vol. 314 Astronomical Data
Analysis Software and Systems XIII, eds. F. Ochsenbein, M. Allen, & D. Egret (San Francisco: ASP), 213
Access to Atomic and Molecular Data/Databases in the VO
M.L. Dubernet
LERMA,
Observatoire de Paris
5, Place Jules Janssen
92195 Meudon Cedex
France
B. Debray, A. Grosjean
Observatoire de Besançon,
41 bis, avenue de l'Observatoire,
BP 1615,
25010 Besançon Cedex
France
M. Bruston, F. Combes, M. Cornille, D. Egret, C. Stéhlé,
L. Tchang-Brillet, C. Zeippen
LERMA,
Observatoire de Paris
5, Place Jules Janssen
92195 Meudon Cedex
France
Abstract:
Numerical and bibliographical Databases in Atomic and Molecular
Physics are essential for both the modelling of various astrophysical
media and the interpretation of astrophysical spectra provided by
ground or space-based telescopes. We report here on our current project
concerning the access to Atomic and Molecular Physics Databases within the
Virtual Observatories, addressing the organisation/access
of data for specific astrophysical applications and the use of standards
for interoperability.
As an example we present the current
status of a numerical and bibliographical database concerning collisional
ro-vibrational excitation rate coefficients of molecules
(
http://basecol.obs-besancon.fr)
It is important to make
atomic and molecular data widely
available in interrelating databases with VO projects; this would allow:
- uniqueness of data used in astrophysical models
- automatic access to these data from web
applications developed for spectrum analysis or modelling
Different steps have been identified in order to organise access to atomic
and molecular data for astrophysical needs:
- identify specific needs for specific applications;
- ``validate'' the relevant atomic and molecular data (precision,
origin of the data: chain of errors);
- get the data into a suitable scientific and technical format;
- semantic definition of the data.
Point 1 was started with the organisation of a
workshop
(),
where physicists and astrophysicists from various areas (solar physics, stars,
planets, interstellar medium) met.
The following conclusions can be drawn:
- data used in different models come from heterogeneous sources;
they are either extracted
from different databases (HITRAN, GEISA, VALD, CHIANTI, NIST, TOPbase, ...)
or calculated by the user.
- The data
are not always reliable and the chain of errors is not known.
It is clear that a dedicated organisation of atomic and molecular
data would be of the utmost interest. We set up a discussion
forum on the subject at
(https://maillist.obs-besancon.fr/wws/info/vo-physique).
A follow up of the project can be found
on
(http://wwwusr.obspm.fr/o-phys/PAGE-VO/main.html).
In view of the scientific preparation of the HIFI instrument of the
Herschel Space Observatory (HSO)
(http://www.sron.nl/divisions/lea/hifi/)
and of
ALMA (http://www.alma.nrao.edu/), particular needs
have been pointed out for:
- data on collisional ro-vibrational excitation of molecules
- data on millimeter and submillimeter spectral data.
These questions are addressed respectively by the
Basemol ()
and (Astrospec) working groups.
In this framework, different groups have been set up to carry out
calculations on collisional ro-vibrational excitation of molecules and to
build a related bibliographic and numerical database.
This database, called
BASECOL (http://basecol.obs-besancon.fr) is
devoted to collisional ro-vibrational excitation of molecules by colliders
such as atom, ion, molecule or electron. We have constituted a national working
group of molecular physicists involved in the calculations of ro-vibrational
cross-sections, in order to ensure the continuity and the quality of the
database. We are currently enlarging the collaboration to the international
molecular physicists community.
We are primarily focusing on collisional systems of interest for various
astrophysical media. The database is composed of several parts:
- a bibliographic database (papers are read and associated to
very precise keywords),
- calculated collisional rates or cross-sections,
- information on the molecular data used
in the cross section calculations, various informations on
ro-vibrational excitation of molecules.
For systems of astrophysical interest, we will:
- provide full information on the chain of errors of the data and give some recommendations
- continue to update the content of the bibliographic database, as well as introducing new choices
such as references on excitation of molecules colliding on a surface
- put on line all the calculated rate coefficients
found in the literature and provide fits of these rate coefficients.
Access is currently available via a classical WEB interface with an
interactive query page for the bibliographic database. An interactive access
to the collisional rates and cross-sections is underway.
We are also addressing the issue of compatibility of the output of the
database within the framework of the Virtual Observatories, in relation
both with WEB tools for spectral analysis and with
other databases such as the UMIST Database for
Astrophysics (http://www.rate99.co.uk/)
and
the Cologne Database for
Molecular Spectroscopy
(http://www.ph1.uni-koeln.de/vorhersagen/).
We have created a discussion forum at
(https://maillist.obs-besancon.fr/wws/info/web-collision).
The BASECOL database will be used both in the modelling of astrophysical
objects (such as the model of Photo-Dissociation Regions (PDR)
currently available
at (http://aristote.obspm.fr/MIS/)) and in
the interpretation
of observed spectra (CASSIS) for HSO:
analysis of observations for the search of new species and the
determination of physical conditions.
Definition of data: UCDs
We are currently addressing the semantic definition
of the Atomic and Molecular Data, in collaboration with
CDS, that is, by defining UCDs
(http://cdsweb.u-strasbg.fr/doc/UCD.htx)
related to atomic and molecular data.
Both the BASECOL database (http://basecol.obs-besancon.fr)
and the MOLAT database (http://molat.obspm.fr) of the
Paris Observatory are going to be used to test the UCDs.
The work in progress is the following:
- go through the existing UCDs and simplify the structure
(remove useless UCDs)
- Work out new UCDs, in particular for molecular physics
- As an example: atomic and molecular processes could
appear in different levels: ``AT" and ``MOL", instead of one level
``AT", as it is at present.
Representing Physics data in VOTable
VOTable (http://cdsweb.u-strasbg.fr/doc/VOTable/) is an XML standard which was
especially designed to
transfer astronomical data in tabular
form. In molecular physics, the data that are often data cubes
(or even ``hypercubes''): for instance the effective collisional
rate coefficients as a function of initial and final quantum
numbers and temperatures.
To be able to represent these data in VOTable, we need
some kind of ``projection'' mechanism to place data cube ``slices''
into VOTable'<TABLE>s. Two solutions can be considered:
- put slices contiguously in one <TABLE> using repeated
<FIELD>s; this solution has been used for some molecular data
available in the CDS Vizier
catalogue service [see table 4 of
catalogue VI/51 about collisional excitation rate of
HCO from (Green 1994)];
- put one slice in one <TABLE>; then all <TABLE>s
must have the same <FIELD>s.
In both cases, we need a further analyser next to the VOTable parser
in order to join data of the same type belonging to either different
<FIELD>s or to a given <FIELD>s in successive
<TABLE>s.
To gather people interested in these matters and share experiences
and questions, a Birds of a Feather
session has been organised (Dubernet 2004).
- Astrospec (contact: adam.walters@cesr.fr)
- CASSIS (contact: adam.walters@cesr.fr)
References
Dubernet, M.L. and Debray, B. , 2004, this volume,
582
Green, S., 1994, VizieR Online Data Catalog, 6051:0+
© Copyright 2004 Astronomical Society of the Pacific, 390 Ashton Avenue, San Francisco, California 94112, USA
Next: BDB - a database for all types of double stars
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