SALTLIBProposal for a Stellar Spectral Library using HRS@SALT

H. P. Singh,

Department of Physics & Astrophysics

University of Delhi, Delhi – 110 007, India

http://people.du.ac.in/~hpsingh/

Goals of a Spectral Library

• Determination of stellar atmospheric parameters, e.g., Teff,

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 1995-2004

• 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 2003• 5 grating settings (~ 1300 Å each) with Loral 3K X 1K CCD• S/N ~ 100 (20 min exposure for 10th magnitude)• Available to the community at http://www.noao.edu/cflib • 2004, The Astrophysical Journal (Suppl), 152, 251

Indo-US Stellar Spectral Library

The spectrum of the star HD 4128 (K0 III) is plotted with expandedregions to show the large information content of the spectrum. Giventhat the S/N exceeds 100:1 per pixel, essentially all features discerniblein the spectrum are real

www.noao.edu/cflib

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/0702.091)

Applications

Martins et al. 2005, MNRAS,358, 49

Synthetic vs. Indo US

Line Indices: synthetic vs. empirical Martins & Coelho 2007, (astro-ph/0705.1994)

Library Resolution

R=λ/∆λ

Spectral range

(nm)

Number

of stars

Reference

STELIB 2000 320-930 249 Le Borgne et al. 2003

ELODIE 10000 390-680 1300 Prugniel et al.2001,04,07

INDO-US 5000 346-946 1273 Valdes et al.

2004

MILES 2000 352-750 985 Sanchez-Blazquez et al. 2006

IRTF-SpeX 2000 800-2500 210 Rayner et al. 2009

NGSL 1000 167-1025 374 Gregg et al.

2006

X-Shooter (XSL) 10000 320-2480 240 Chen et al. 2011

UVES-POP 80000 307-1030 300 Bagnuolo et al. 2003

LW2000 1100 500-2500 100 Lancon & Wood 2000

Some recent spectral libraries

HRS@SALT 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. 2011. 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 HRS@SALT and for the preparation of future observations.