The Spitzer/IRS ATLAS project

• Home
• History
• Project
• Data
• Contrib

a a a a a a a a a a a a a a a a a a a a a a a a a a

An ATLAS of mid-infrared spectra of star-forming and active galaxies

There are a few Spitzer Legacy programs with IRS observations of galaxies that have already released highly processed data products, like spectral cubes and maps (e.g. SINGS, 5MUSES, SSGSS); but the great majority of IRS spectra, even if public now, can only be obtained as BCD and post-BCD data in the Spitzer archive, and require a further reduction and extraction process that may be tricky to people not familiar with mid-infrared spectroscopy. In addition, the Spitzer Archive interface allows for name, position or abstract keyword searches, but doesn't have the capability to constraint source properties, such as redshift, fluxes or colors (since this information isn't even available in the archive) and thus prospective data-miners are forced to first scrutinize the literature in a quest for suitable candidates or limit their searches to known fields/programs.

With that in mind, and with the aim to help astronomers with little or no experience in mid-infrared spectroscopy to take advantage of Spitzer/IRS data, we have compiled and released the ATLAS database, to facilitate the selection of samples with specific properties by providing MIR measurements as well as the full MIR spectra on a large number of extragalactic sources of all kind.

The ATLAS project currently comprises three distinct data products:

• IRS spectra in the form of ASCII tables containing wavelength, flux density and an estimate on the flux density uncertainty.
• Catalogs in several formats (VOTABLE, FITS) containing up to 200 properties per source, including positions, redshift, photometry in the optical, near-, mid- and far-infrared as well as radio fluxes, mid-IR properties such as PAH equivalent widths and luminosities, silicate strength, continuum luminosities at several restframe wavelengths, etc.
• Templates obtained by composition of all sources within the sample of a given spectral type in the optical or in the mid-infrared. Templates in the form of ASCII tables are provided for type 1 and type 2 Seyfert galaxies, QSOs, starbursts, LINERs, ULIRGs, submillimeter galaxies, etc.

You can browse the catalog and check out the spectra of individual sources using the interactive browser or download the full catalog and spectral library in the download section.

Data quality and intended use

Please note that we do not intend to substitute the Spitzer Archive, but to complement it. The spectra in ATLAS have been obtained from published figures in papers submitted to the arxiv.org preprint service, and thus do not contain all the information available in a properly reduced IRS observation. In particular, quality flags and flux uncertainties are missing (even if we have managed to at least partially overcome this), and many authors smooth or truncate the spectra in their plots. Because of this, researchers who require precise measurement of spectral properties or an accurate estimate of uncertainties are encouraged to use our database to find suitable candidates, and then obtain the latest version of the BCD data from the Spitzer Archive and perform a proper data reduction. A library of fully processed IRS spectra of LIRGs and ULIRGs is available here and also at the Cornell Atlas of Spitzer IRS Spectra.

Disclaimer

Changes in Spitzer data products among versions of the SSC pipeline, use of different reduction and extraction procedures relative to those used by the authors, and changes in calibration files can all produce small differences between the spectra in the ATLAS sample and those you can obtain from the Spitzer Archive. Faint sources and extended sources are particularly sensitive to the details of the reduction and extraction process. In addition, smoothing or resampling of the spectra and correction of cosmetics by the authors can degrade the quality of the data.
The ATLAS project does not perform any verification on the integrity or accuracy of the data published by other authors, and does not evaluate, endorse or object the reduction and extraction process used by them. Use this data at your own risk.