Browsing by Subject "absorption-bands"
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Item Mapping The Interstellar Medium With Near-Infrared Diffuse Interstellar Bands(2015-01) Zasowski, Gail; Menard, B.; Bizyaev, Dmitry; Garcia-Hernandez, D. Anibal; Perez, A. E. G.; Hayden, M. R.; Holtzman, Jon; Johnson, John A.; Kinemuchi, K.; Majewski, Steven R.; Nidever, David L.; Shetrone, Matthew; Wilson, J. C.; Shetrone, MatthewWe map the distribution and properties of the Milky Way's interstellar medium as traced by diffuse interstellar bands (DIBs) detected in near-infrared stellar spectra from the SDSS-III/APOGEE survey. Focusing exclusively on the strongest DIB in the H band, at lambda similar to 1.527 mu m, we present a projected map of the DIB absorption field in the Galactic plane, using a set of about 60,000 sightlines that reach up to 15 kpc from the Sun and probe up to 30 mag of visual extinction. The strength of this DIB is linearly correlated with dust reddening over three orders of magnitude in both DIB equivalent width (Wpm) and extinction, with a power law index of 1.01 +/- 0.01, a mean relationship of W-DIB/A(v) = 0.1 angstrom mag(-1) and a dispersion of similar to 0.05 angstrom mag(-1) at extinctions characteristic of the Galactic midplane. These properties establish this DIB as a powerful, independent probe of dust extinction over a wide range of Av values. The subset of about 14,000 robustly detected DIB features have a W-DIB distribution that follows an exponential trend. We empirically determine the intrinsic rest wavelength of this transition to be lambda(0) = 15 272.42 angstrom and use it to calculate absolute radial velocities of the carrier, which display the kinematical signature of the rotating Galactic disk. We probe the DIB carrier distribution in three dimensions and show that it can be characterized by an exponential disk model with a scale height of about 100 pc and a scale length of about 5 kpc. Finally, we show that the DIB distribution also traces large-scale Galactic structures, including the Galactic long bar and the warp of the outer disk.Item Review: A Search For Diffuse Bands In The Circumstellar Envelopes Of Post-AGB Stars(2008-03) Luna, R.; Cox, N. L. J.; Satorre, M. A.; Hernández, D. A. García.; Suarez, O.; Lario, P. G.; García Hernández, D. A.In this work we present the results of a systematic search for diffuse bands (DBs, hereafter) in the circumstellar envelopes of a carefully selected sample of post-AGB stars. We concentrated on analyzing 9 of the DBs most commonly found in the interstellar medium. The strength of these features is determined using high-resolution optical spectroscopy, and the results obtained are compared with literature data on field stars affected only by interstellar reddening. Based on the weak features observed in the subsample of post-AGB stars dominated by circumstellar reddening, we conclude that the carrier(s)of these DBs must not be present in the circumstellar environment of these sources, or at least not under the excitation conditions in which DBs are formed. This conclusion is applicable to all the post-AGB stars studied, irrespective of the dominant chemistry or the spectral type of the star considered. A detailed radial velocity analysis of the features observed in individual sources confirms this result, as the Doppler shifts measured are found to be consistent with an interstellar origin.