SEGUE Spectroscopy

Quick Links

A sampling of stars from the imaging data (see Sky Coverage) is targeted for spectroscopic observations. Candidates are assigned to a series of plates, each of which targets 640 objects. Spectra are measured using a a pair of double spectrographs that cover a wavelength range of 3800-9200Å with a resolution of &lambda/&Delta&lambda ~ 1800.

The distribution of SEGUE plates in RA and dec is shown below:

Upper panel: Blue circles indicate main Galactic structure survey: yellow circles are special targets such as open clusters.

Lower panel: Distribution in RA

Two plates are exposed in each of 200 directions on the sky (for a total of 400 plates):

one bright plate, with an exposure time of about 45 minutes,
and one faint plate, with an exposure time of about 1.5 hours.

The faint plate yields S/N ~ 10 for objects as faint as g ~ 20.3 and S/N > 50 for g ~ 18.0. A list of available SEGUE plates, with links to the observed spectra, is available at SEGUE plate list.

The SEGUE Stellar Stellar Parameter Pipeline (SSPP) has been developed to extract atmospheric parameters from the spectra. Radial velocities (with errors ~ 5 - 25 km/s) and fundamental stellar atmospheric parameters (T_eff, surface gravity, and metallicity) are determined for stars at distances from 2 to 150 kpc from the Sun. Rare objects, such as cool white dwarfs (with distances < 100 pc) are also targeted. A detailed description of the SSPP can be found in Lee et al., 2007.