Quantitative Spectroscopic J-band Study of Red Supergiants in Perseus OB-1

Abstract

We demonstrate how the metallicities of red supergiant (RSG) stars can be measured from quantitative spectroscopy down to resolutions of ~3000 in the J-band. We have obtained high resolution spectra on a sample of the RSG population of h and chi Persei, a double cluster in the solar neighborhood. We show that careful application of the MARCS model atmospheres returns measurements of Z consistent with solar metallicity. Using two grids of synthetic spectra--one in pure LTE and one with NLTE calculations for the most important diagnostic lines--we measure Z = +0.04 +/- 0.10 (LTE) and Z = -0.04 +/- 0.08 (NLTE) for the sample of eleven RSGs in the cluster. We degrade the spectral resolution of our observations and find that those values remain consistent down to resolutions of less than R of 3000. Using measurements of effective temperatures we compare our results with stellar evolution theory and find good agreement. We construct a synthetic cluster spectrum and find that analyzing this composite spectrum with single-star RSG models returns an accurate metallicity. We conclude that the RSGs make ideal targets in the near infrared for measuring the metallicities of star forming galaxies out to 7-10 Mpc and up to ten times farther by observing the integrated light of unresolved super star clusters.

13 pages, 12 figures. Accepted to ApJ

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• Red Supergiant Stars as Cosmic Abundance Probes: KMOS Observations in NGC 6822
• Red Supergiant Stars as Cosmic Abundance Probes. III. NLTE effects in J-band Magnesium lines
• Red Supergiants as Cosmic Abundance Probes: The Magellanic Clouds
• Red Supergiants as Cosmic Abundance Probes: The Sculptor Galaxy NGC 300
• Red Supergiants as Cosmic Abundance Probes: massive star clusters in M83, and the mass-metallicity relation of nearby galaxies
• Multiplicity of the red supergiant population in the young massive cluster NGC 330
• The metallicity and distance of NGC 2403 from blue supergiants
• New infrared spectral indices of luminous cold stars: from early K to M-types
• Metallicities of Young Massive Clusters in NGC 5236 (M83)
• Identification of late-type stars of class I
• Red supergiant stars in IC 1613 and metallicity-dependent mixing length in the evolutionary model
• MAGIS (Measuring Abundances of red super Giants with Infrared Spectroscopy) project I. Establishment of an abundance analysis procedure for red supergiants and its evaluation with nearby stars
• Science Case and Requirements for the MOSAIC Concept for a Multi-Object Spectrograph for the European Extremely Large Telescope
• Stellar population astrophysics (SPA) with the TNG -- The chemical content of the red supergiant population in the Perseus complex