Near-Infrared Spectral Properties of Metal-Poor Red Supergiants Valentin D. Ivanov (ESO) Collaborators: Marcia J. Rieke, A. Alonso- Herrero, Danielle Alloin

Why the world needs yet another near-infrared spectral atlas? - improved metallicity coverage for red supergiants for population synthesis models of metal-poor galaxies undergoing active star formation - higher resolution than the typically used in order to work in-between the sky emission lines, for example searching for high redshift emitters in the near infrared - stellar abundance and abundance ratio analysis - templates are needed for kinematic mass estimates of the recently discovered massive star clusters; such estimates would be based on the CO band head (i.e. Mengel et al. 2002)

Currently Available IR Spectral Atlases Summary from Ivanov et al. (2004, accepted to ApJS) From Ivanov et al. (2004, ApJS. 151, 387)

Program stars - Sample Selection - goal: equidistant T eff coverage at fixed abundance [Fe/H]~ Observed stars: -- sequence of: K2-K5-M0-M1-M6 SMC RSGs -- Milky Way stars: HD8498 – K5 III HD – K2 II

Program stars – Sample Selection MBR – Meliani et al. (1995) OSK - Oestreicher and Schmidt-Kaler (1998) Red line – observed SMC stars

Observations and Data Reduction - one night with VLT: Aug 25/26, strategy: 1 or 2 AB cycles = nodding along the slit; always a nearby star of similar brightness was put in the slit - set up: slit 0.6”; typically 1x120 sec in H- band and 2x120 sec in K-band; R~9000 – some degradation in comparison with the expected R~10000, due to instrument miss-alignment - spectral coverage: (4 settings) and microns (3 settings) - typical signal-to-noise ratio S/N~20-30, dominated by the systematics such as sky background and transmission variation - telluric standards: B-A stars at the same or similar airmass; the spectra of the program stars will be flux-calibrated

Data MBR P123 K2I T eff =4293 K log g=+0.57 [Fe/H]=-0.70 Note Bene: this is a preliminary reduction! Note the telluric correction artifacts at ~1.75 and ~2.40 microns!

Spectral Features MBR P123 K2I T eff =4293 K log g=+0.57 [Fe/H]=-0.70

Summary - the main goals of this project are to improve the metallicity coverage of infrared spectral atlases for the red supergiants which dominate the near-IR continuum of starbursts - five red supergiants stars in the Small Magellanic Cloud were observed at medium- high spectral resolution (R~9000) with ISAAC at the VLT; one Galactic red giant and one Galactic red supergiant were observed for comparison purposes.