DIFFUSE INTERSTELLAR BAND AT 8620 Å IN RAVE: A NEW METHOD FOR DETECTING THE DIFFUSE INTERSTELLAR BAND IN SPECTRA OF COOL STARS

Diffuse interstellar bands (DIBs) are usually observed in spectra of hot stars, where interstellar lines are rarely blended with stellar ones. The need for hot stars is a strong limitation in the number of sightlines we can observe and their distribution in the Galaxy, as hot stars are rare and conc...

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Bibliographic Details
Published in:The Astrophysical journal 2013-12, Vol.778 (2), p.1-11
Main Authors: Kos, J, Zwitter, T, Grebel, E K, Bienayme, O, Binney, J, Bland-hawthorn, J, Freeman, K C, Gibson, B K, Gilmore, G, KORDOPATIS, G
Format: Article
Language:English
Subjects:
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
COMPARATIVE EVALUATIONS
Cool stars
Diffuse interstellar bands
DISTRIBUTION
DUSTS
Equivalence
GALAXIES
Hot stars
Interstellar
Mathematical analysis
MATTER
RADIAL VELOCITY
SIGNAL-TO-NOISE RATIO
SPECTRA
Spectral lines
STARS
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Summary:Diffuse interstellar bands (DIBs) are usually observed in spectra of hot stars, where interstellar lines are rarely blended with stellar ones. The need for hot stars is a strong limitation in the number of sightlines we can observe and their distribution in the Galaxy, as hot stars are rare and concentrated in the Galactic plane. We are introducing a new method, where interstellar lines can be observed in spectra of cool stars in large spectroscopic surveys. The method is completely automated and does not require prior knowledge of the stellar parameters. The main step is a construction of the stellar spectrum, which is done by finding other observed spectra that lack interstellar features and are otherwise very similar to the spectrum in question. Such spectra are then combined into a single stellar spectrum template, matching the stellar component of the observed spectrum. We demonstrate the performance of this new method on a sample of 482,430 Radial Velocity Experiment survey spectra. However, many spectra have to be combined (48 on average) in order to achieve a signal-to-noise ratio high enough to measure the profile of the DIB at 8620 A, hence limiting the spatial information about the interstellar medium. We compare its equivalent width with extinction maps and with Bayesian reddening, calculated for individual stars, and provide a linear relation between the equivalent width and reddening. Separately from the introduced method, we calculate equivalent widths of the DIB in spectra of hot stars with known extinction and compare all three linear relations.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/778/2/86