SALTLIB Proposal for a Stellar Spectral Library using H. P. Singh, Department of Physics & Astrophysics University of Delhi, Delhi – , India

Goals of a Spectral Library Determination of stellar atmospheric parameters, e.g., T eff, log g, and [Fe/H] Galaxy Population Synthesis/galaxy spectra Comparison with synthetic stellar spectra from model atmospheres Automated Spectral Classification of stellar spectra Test techniques of Automated Spectral Classification like principal component analysis and Artificial Neural Networks publicly available

H P Singh (University of Delhi, India) R Gupta (IUCAA, Pune, India) F. Valdes, D. Bell (NOAO, Tucson, AZ, USA) J. Rose (Univ. of North Carolina at Chapel Hill,USA) INDO-US COUDE FEED LIBRARY Collaboration from

Spectro-Luminosity coverage: O to M type, I to V class Wavelength coverage: 3500 – 9500 Å Spectral Resolution: 1 Å ~ 1300 stars (7085 individual spectra) Observations for ~ 100 nights between June 1995 to April grating settings (~ 1300 Å each) with Loral 3K X 1K CCD S/N ~ 100 (20 min exposure for 10 th magnitude) Available to the community at , The Astrophysical Journal (Suppl), 152, 251 Indo-US Stellar Spectral Library

The spectrum of the star HD 4128 (K0 III) is plotted with expanded regions to show the large information content of the spectrum. Given that the S/N exceeds 100:1 per pixel, essentially all features discernible in the spectrum are real

IAG ( < 1 Å ) Indo –US ( 1 Å) Miles (2.3 Å ) Stelib (3Å) HNGSL ( 5 Å) Pickles (20 Å) Kurucz (20 Å) Bruzual 2007 (astro-ph/ ) Applications

Martins et al. 2005, MNRAS,358, 49 Synthetic vs. Indo US

Line Indices: synthetic vs. empirical Martins & Coelho 2007, (astro-ph/ )

LibraryResolution R= λ/ ∆ λ Spectral range (nm) Number of stars Reference STELIB Le Borgne et al ELODIE Prugniel et al.2001,04,07 INDO-US Valdes et al MILES Sanchez- Blazquez et al IRTF-SpeX Rayner et al NGSL Gregg et al X-Shooter (XSL) Chen et al UVES-POP Bagnuolo et al LW Lancon & Wood 2000 Some recent spectral libraries

would be an excellent instrument to build a library at high spectral resolution (R=65000). The rationale for such a library would be: - Provide a detailed basis for the validation and calibration of theoretical grids of spectra. (The theoretical spectra still suffer from severe limitations, mostly due to imperfect line lists. A solution is to provide observed spectra at the highest resolution. The comparison will allow to 'correct' the line lists). -A high resolution empirical library would be excellent for fundamental parameters and chemical composition measurements (using the methods developed by us with ELODIE (Wu et al. 2011, Prugniel et al We may provide an on-line tool to measure the atmospheric parameters and implement it in the SALT environment to analyze any star measured with HRS at any resolution.) -The correction of the telluric lines and interstellar extinction lines (This is a difficult issue for the ongoing XSL library (X-shooter spectrograph). With HRS at a 6- 9 times higher resolution, the problem will be handled much more properly. This will allow to provide a considerably better library in the CaT region. It will undoubtedly be precious for the analysis of the Gaia spectra (and re-analysis of RAVE)).

I would suggest to make a high-resolution counterpart of XSL that may be based on the same selection of stars. The only comparable library will be UVES-POP (ESO) that has a very limited coverage of the parameter space. These are mostly bright stars, and I guess that such a program will take a total of about 200 hours (we have to check it with the efficiency curves and the S/N we would like to achieve). This would be a pretty large program, but this can be made over 4-5 years, and shall involve other partners (IUCAA has around 300 hours per year). Stellar libraries are considered a legacy product for the community. It is certainly a good time to start, and to find partners in the SALT community.

Concerning the Science Verification, the proposition may be : - Observe a set of bright stars covering a range of types and luminosity classes with the high-resolution mode. - These stars, drawn out of the first release of XSL (X-shooter stellar library) and will belong to UVES-POP, will allow us to check in detail the accuracy and performances of the spectrograph. - We can pay particular attention to the presence of diffuse light and to the accuracy and stability of the LSF. - We can deliver a fully-reduced mini-library that will be useful as a comparison basis for early-science with and for the preparation of future observations.