Compact infrared sources : NGC 7538 and the galactic center

by Willner, Steven Paul

Abstract (Summary)
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. Three infrared and radio sources in NGC 7538 have been observed from 8 to 13 [...] with 1% spectral and 5" spatial resolution. The very small southern source shows a deep silicate absorption feature at 9.7 [...] while the northern extended source shows little or no silicate absorption, but has a 12.8-[...] emission line from Ne II. The data imply that the compact source has a gas to dust ratio of 75 inside the ionized region. The extended source only 10" away has a gas to dust ratio implied by the 10-[...] data alone of 3 x 10[...], but the true ratio must be much lower to account for published 20-[...] measurements. A revised 10-[...] map of the Galactic center with 2[...]3 resolution, broadband photometry of individual sources from 1.2 to 20 [...], and 8 to 13-[...] photometry of individual sources with 1% spectral resolution have been obtained. The principal conclusions of this study are: (1) The five sources with the bluest energy distributions between 1.6 and 3.5 [...] are stars or star clusters. The brightest has a luminosity of 10[...] L[...] while the other four have luminosities of about 10[...] L[...]. (2) There is extended emission from ionized gas and dust. (3) The density of ionized gas in the discrete 10-[...] sources is no higher than that in the extended source. (4) There is at least one compact source that is not associated with the others and has a different energy distribution. (5) Most of the extinction toward the sources observed is interstellar and is moderately uniform. The visual extinction is about 28 magnitudes, and the 9.7-[...] silicate extinction is about 3.7 magnitudes.
Bibliographical Information:

Advisor:E. E. Becklin; G. Neugebauer

School:California Institute of Technology

School Location:USA - California

Source Type:Master's Thesis



Date of Publication:01/29/1976

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