Next Generation Spectral Library

Available Formats

The intrinsic dispersion of the STIS low resolution gratings varies from 1.37Å per pixel in the UV to 4.86Å per pixel in the red. Some users will find it easiest to deal with each star as a single file with a single dispersion, while others will prefer to work with the data in its "as observed" dispersion. And some will want fits files, others ascii tables. In an effort to please (most) everyone, we plan to make the spectra for each star available in these formats:

1) One fits image with a linear dispersion of 1.37Å per pixel over the wavelength range 1670Å to 10200Å. This multispec file can be viewed in iraf with splot, etc. Here is an example fits image.

1a) A two-column ascii table of the data in the fits image in (1), listing the wavelengths and fluxes, plus a prepended fits header. Here is an example text file.

2) A trio of multispec fits images for each star, suitable for splot viewing, one for each of the STIS gratings, G230LB, G430L, and G750L. These fits spectra have a linear dispersion which is very close to the natural dispersion of the raw data. These multispec files also include "bands" with the total counts, the background, and an error array produced by the CALSTIS routines. Our pipeline at this time does not subtract any background, so the background (band 3) is all zeroes. Here are three examples, G230LB , G430L , and G750L . These spectra are presented "as extracted" by the CALSTIS software, so the ends can be somewhat noisy. The noisy parts are clipped by our pipeline when producing the final spectra in (1) and (1a). Users who download the individual grating spectra are advised to use their judgment. If there is sufficient demand, we can clean up these spectra for distribution, but feel at this time that a bit of reality is not a bad thing.

2a) The three spectra in (2) can easily be turned into text files, as was done in (1a), but we leave this up to the user. If this is a hardship for anyone, we will do it and make them available, though it would quadruple the number of files and links we would have to maintain.

3) If you are interested in just a few stars, informative postscript plots of individual objects can be viewed or downloaded. In this example plot, one can clearly see the effects of the red contamination in the extreme UV where the spectrum turns up.

4) The whole lot of (1), (1a), or (2) can be downloaded as gzipped tar files.

When the library reaches completion, the spectra will be parsed by abundance into the four [Fe/H] ranges:

-2.0 < [Fe/H] < -1.5

-1.3 < [Fe/H] < -0.5

-0.3 < [Fe/H] < +0.1


[Fe/H] > +0.2.

and made available as four separate libraries. For now, we simply supply in each spectrum a header keyword indicating the published metallicity that we assumed in choosing the star for the library.

Header Information

Eventually, header keywords will be added to indicate the adopted [Fe/H], log(g) and T_eff. These values will be refined and homogenized as analysis of the spectra proceeds. We will also add header information providing the observed V magnitude, various broad band colors determined from the STIS spectra, the Hipparcos parallax, the Hipparcos catalog number, the absolute V magnitude, proper motion, and RA and Dec, and other useful information.

Jump To:
UCD Physics Dept.
Cosmology Research Group
Institute of Geophysics and Planetary Physics at the Lawrence Livermore National Laboratory

Last modified February, 2004
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