Volume 527, March 2011
|Number of page(s)||13|
|Published online||24 January 2011|
Stellar metallicities beyond the Local Group: the potential of J-band spectroscopy with extremely large telescopes
UK Astronomy Technology Centre, Royal Observatory Edinburgh,
2 Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623, USA
3 School of Physics & Astronomy, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
4 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK
5 Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
6 Max-Planck-Institute for Astrophysics, Karl-Schwarzschild-Str. 1, 85748 Garching, Germany
7 GEPI, Observatoire de Paris, 5 place Jules Janssen, 92195 Meudon Cedex, France
8 Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012, PR China
9 LAM, OAMP, 38 rue Frédéric Joliot Curie, 13388 Marseille Cedex 13, France
10 Department of Physics, Durham University, South Road, Durham, DH1 3LE, UK
11 LESIA, Observatoire de Paris, 5 place Jules Janssen, 92195 Meudon Cedex, France
Received: 23 October 2010
Accepted: 8 December 2010
We present simulated J-band spectroscopy of red giants and supergiants with a 42 m European Extremely Large Telescope (E-ELT), using tools developed toward the EAGLE Phase A instrument study. The simulated spectra are used to demonstrate the validity of the 1.15–1.22 μm region to recover accurate stellar metallicities from Solar and metal-poor (one tenth Solar) spectral templates. From tests at spectral resolving powers of four and ten thousand, we require continuum signal-to-noise ratios in excess of 50 (per two-pixel resolution element) to recover the input metallicity to within 0.1 dex. We highlight the potential of direct estimates of stellar metallicites (over the range − 1 < [Fe/H] < 0) of red giants with the E-ELT, reaching out to distances of ~ 5 Mpc for stars near the tip of the red giant branch. The same simulations are also used to illustrate the potential for quantitative spectroscopy of red supergiants beyond the Local Volume to tens of Mpc. Calcium triplet observations in the I-band are also simulated to provide a comparison with contemporary techniques. Assuming the EAGLE instrument parameters and simulated performances from adaptive optics, the J-band method is more sensitive in terms of recovering metallicity estimates for a given target. This appears very promising for ELT studies of red giants and supergiants, offering a direct metallicity tracer at a wavelength which is less affected by extinction than shortward diagnostics and, via adaptive optics, with better image quality.
Key words: instrumentation: adaptive optics / instrumentation: spectrographs / techniques: spectroscopic / Galaxy: stellar content / stars: fundamental parameters
© ESO, 2011
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