Astronomy and Astrophysics, volume 593A, 7-7 (2016/9-1)
Gas absorption and dust extinction towards the Orion Nebula Cluster.
HASENBERGER B., FORBRICH J., ALVES J., WOLK S.J., MEINGAST S., GETMAN K.V. and PILLITTERI I.
Abstract (from CDS):
Aims. We characterise the relation between the gas and dust content of the interstellar medium towards young stellar objects in the Orion Nebula Cluster.
Methods. X-ray observations provide estimates of the absorbing equivalent hydrogen column density NH based on spectral fits. Near-infrared extinction values are calculated from intrinsic and observed colour magnitudes (J-H) and (H-Ks) as given by the VISTA Orion A survey. A linear fit of the correlation between column density and extinction values AV yields an estimate of the NH/AV ratio. We investigate systematic uncertainties of the results by describing and (if possible) quantifying the influence of circumstellar material and the adopted extinction law, X-ray models, and elemental abundances on the NH/AV ratio.
Results. Assuming a Galactic extinction law with RV=3.1 and solar abundances by Anders & Grevesse (1989, Geochim. Cosmochim. Acta, 53, 197), we deduce an NH/AV ratio of (1.39±0.14)x1021cm–2mag–1 for Class III sources in the Orion Nebula Cluster where the given error does not include systematic uncertainties. This ratio is consistent with similar studies in other star-forming regions and approximately 31% lower than the Galactic value. We find no obvious trends in the spatial distribution of NH/AV ratios. Changes in the assumed extinction law and elemental abundances are demonstrated to have a relevant impact on deduced AV and NH values, respectively. Large systematic uncertainties associated with metal abundances in the Orion Nebula Cluster represent the primary limitation for the deduction of a definitive NH/AV ratio and the physical interpretation of these results.
© ESO, 2016
dust, extinction - X-rays: ISM - infrared: ISM - stars: pre-main sequence
VizieR on-line data:
<Available at CDS (J/A+A/593/A7): table1.dat>
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