A Uniform Database of 2.2-16.5 µm Spectra from the ISOCAM CVF Spectrometer

Abstract

We present all ISOCAM circular variable filter (CVF) spectra that cover more than one-third of the 2.2-16.5 μm spectral range of the instrument. The 364 spectra have been classified according to the classification system of Kraemer et al., as modified by Hodge et al. to account for the shorter wavelength range. Prior to classification, the spectra were processed and recalibrated to create a uniform database. Aperture photometry was performed at each wavelength centered on the brightest position in each image field and the various spectral segments merged into a single spectrum. The aperture was the same for all scale sizes of the images. Since this procedure differs fundamentally from that used in the initial ISOCAM calibration, a recalibration of the spectral response of the instrument was required for the aperture photometry. The recalibrated spectra and the software used to create them are available to the community on-line via the ISO Data Archive. Several new groups were added to the KSPW system to describe spectra with no counterparts in either the SWS or PHT-S databases: CA, E/SA, UE/SA, and SSA. The zodiacal dust cloud provides the most common background continuum to the spectral features, visible in almost 40% of the processed sources. The most characteristic and ubiquitous spectral features observed in the CVF spectral atlas are those of the unidentified infrared bands (UIR), which are typically attributed to ultraviolet-excited fluorescence of large molecules containing aromatic hydrocarbons. The UIR features commonly occur superimposed on the zodiacal background (18%) but can also appear in conjunction with other spectral features, such as fine-structure emission lines or silicate absorption. In at least 13 of the galaxies observed, the pattern of UIR emission features has been noticeably shifted to longer wavelengths.

Based on observations with the Infrared Space Observatory, a European Space Agency (ESA) project with instruments funded by ESA Member States (especially the Principal Investigator countries: France, Germany, the Netherlands, and the United Kingdom) and with the participation of the Institute of Space and Astronautical Science (ISAS) and the National Aeronautics and Space Administration (NASA).