Spitzer IRS Observations of the Galactic Center: Shocked Gas in the Radio Arc Bubble - AstrophysicsReport as inadecuate

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Abstract: We present Spitzer IRS spectra R ~600, 10 - 38 micron of 38 positions inthe Galactic Center GC, all at the same Galactic longitude and spanningplus-minus 0.3 degrees in latitude. Our positions include the Arches Cluster,the Arched Filaments, regions near the Quintuplet Cluster, the ``Bubble- lyingalong the same line-of-sight as the molecular cloud G0.11-0.11, and the diffuseinterstellar gas along the line-of-sight at higher Galactic latitudes. Frommeasurements of the O IV, Ne II, Ne III, Si II, S III, S IV, FeII, Fe III, and H 2 S0, S1, and S2 lines we determine the gasexcitation and ionic abundance ratios. The Ne-H and S-H abundance ratios are ~1.6 times that of the Orion Nebula. The main source of excitation isphotoionization, with the Arches Cluster ionizing the Arched Filaments and theQuintuplet Cluster ionizing the gas nearby and at lower Galactic latitudesincluding the far side of the Bubble. In addition, strong shocks ionize gas toO^{+3} and destroy dust grains, releasing iron into the gas phase Fe-H ~ 1.3times 10^{-6} in the Arched Filaments and Fe-H ~ 8.8 times 10^{-6} in theBubble. The shock effects are particularly noticeable in the center of theBubble, but O$^{+3}$ is present in all positions. We suggest that the shocksare due to the winds from the Quintuplet Cluster Wolf-Rayet stars. On the otherhand, the H 2 line ratios can be explained with multi-component models of warmmolecular gas in photodissociation regions without the need for H 2 productionin shocks.

Author: Janet P. Simpson 1 and 2, Sean W. J. Colgan 1, Angela S. Cotera 2, Edwin F. Erickson 1, David J. Hollenbach 3, Michael J. Kaufman

Source: https://arxiv.org/

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