Leiden University Scholarly Publications

Werf, P.P. van der; Goss, W.; O'Dell, C. (2013)

Tearing the Veil: Interaction of the Orion Nebula with its Neutral Environment

Article / Letter to editor

We present H I 21 cm observations of the Orion Nebula, obtained with the Karl G. Jansky Very Large Array, at an angular resolution of 7.''2 { imes} 5.''7 and a velocity resolution of 0.77 km s$^{-1}$. Our data reveal H I absorption in the Veil toward the radio continuum of the H II region, and H I emission arising from the Orion Bar photon-dominated region (PDR) and from the Orion-KL outflow. In the Orion Bar PDR, the H I signal peaks in the same layer as the H$_{2}$ near-infrared vibrational line emission, in agreement with models of the photodissociation of H$_{2}$. The gas temperature in this region is approximately 540 K, and the H I abundance in the interclump gas in the PDR is 5%-10% of the available hydrogen nuclei. Most of the gas in this region therefore remains molecular. Mechanical feedback on the Veil manifests itself through the interaction of ionized flow systems in the Orion Nebula, in particular the Herbig-Haro object HH 202, with the Veil. These interactions...Show more We present H I 21 cm observations of the Orion Nebula, obtained with the Karl G. Jansky Very Large Array, at an angular resolution of 7.''2 { imes} 5.''7 and a velocity resolution of 0.77 km s$^{-1}$. Our data reveal H I absorption in the Veil toward the radio continuum of the H II region, and H I emission arising from the Orion Bar photon-dominated region (PDR) and from the Orion-KL outflow. In the Orion Bar PDR, the H I signal peaks in the same layer as the H$_{2}$ near-infrared vibrational line emission, in agreement with models of the photodissociation of H$_{2}$. The gas temperature in this region is approximately 540 K, and the H I abundance in the interclump gas in the PDR is 5%-10% of the available hydrogen nuclei. Most of the gas in this region therefore remains molecular. Mechanical feedback on the Veil manifests itself through the interaction of ionized flow systems in the Orion Nebula, in particular the Herbig-Haro object HH 202, with the Veil. These interactions give rise to prominent blueward velocity shifts of the gas in the Veil. The unambiguous evidence for interaction of this flow system with the Veil shows that the distance between the Veil and the Trapezium stars needs to be revised downward to about 0.4 pc. The depth of the ionized cavity is about 0.7 pc, which is much smaller than the depth and the lateral extent of the Veil. Our results reaffirm the blister model for the M42 H II region, while also revealing its relation to the neutral environment on a larger scale.Show less

All authors

Werf, P.P. van der; Goss, W.; O'Dell, C.

Date

2013

Journal

The Astrophysical Journal

Volume

762

Pages

101

DOI

doi:10.1088/0004-637X/762/2/101

Link

http://adsabs.harvard.edu/abs/2013ApJ...762..101V