The SEGUE Stellar Parameter Pipeline. II. Validation with Galactic Globular and Open Clusters

TL;DR

This paper validates the SEGUE Stellar Parameter Pipeline (SSPP) by comparing its derived stellar parameters with literature values for stars in globular and open clusters, quantifying its accuracy and limitations.

Contribution

It provides a detailed validation of the SSPP's accuracy in determining stellar parameters using cluster data, highlighting its uncertainties and current biases.

Findings

SSPP has a typical metallicity uncertainty of 0.13 dex.

Good agreement between SSPP and stellar evolution models for temperature and gravity.

SSPP underestimates [Fe/H] by about 0.3 dex for near-solar-metallicity stars.

Abstract

We validate the performance and accuracy of the current SEGUE (Sloan Extension for Galactic Understanding and Exploration) Stellar Parameter Pipeline (SSPP), which determines stellar atmospheric parameters (effective temperature, surface gravity, and metallicity) by comparing derived overall metallicities and radial velocities from selected likely members of three globular clusters (M 13, M 15, and M 2) and two open clusters (NGC 2420 and M 67) to the literature values. Spectroscopic and photometric data obtained during the course of the original Sloan Digital Sky Survey (SDSS-I) and its first extension (SDSS-II/SEGUE) are used to determine stellar radial velocities and atmospheric parameter estimates for stars in these clusters. Based on the scatter in the metallicities derived for the members of each cluster, we quantify the typical uncertainty of the SSPP values, sigma([Fe/H]) = 0.13 dex for stars in the range of 4500 K < Teff < 7500 K and 2.0 < log g < 5.0, at least over the metallicity interval spanned by the clusters studied (-2.3 < [Fe/H] < 0). The surface gravities and effective temperatures derived by the SSPP are also compared with those estimated from the comparison of the color-magnitude diagrams with stellar evolution models; we find satisfactory agreement. At present, the SSPP underestimates [Fe/H] for near-solar-metallicity stars, represented by members of M 67 in this study, by about 0.3 dex.