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Title: On structural patterns in H II regions

Abstract

High-resolution photographs of H II regions show that a large number of stars embedded in the nebulosities appear to be surrounded by emply spaces. This phenomenon seems to be quite common but has escaped attention up to now. The effect is not a photographic one, nor does it arise in the half-tone reproduction processes employed in publications, but no satisfactory explanation is apparent. 9 refs.

Authors:
 [1]
  1. (NASA, Goddard Space Flight Center, Greenbelt, MD (USA))
Publication Date:
OSTI Identifier:
5398151
Resource Type:
Journal Article
Resource Relation:
Journal Name: Publications of the Astronomical Society of the Pacific; (USA); Journal Volume: 101
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; H2 REGIONS; MORPHOLOGY; IMAGES; NEBULAE; PHOTOGRAPHY; STARS; VOIDS; COSMIC RADIO SOURCES; 640105* - Astrophysics & Cosmology- Galaxies

Citation Formats

Feibelman, W.A. On structural patterns in H II regions. United States: N. p., 1989. Web. doi:10.1086/132466.
Feibelman, W.A. On structural patterns in H II regions. United States. doi:10.1086/132466.
Feibelman, W.A. Mon . "On structural patterns in H II regions". United States. doi:10.1086/132466.
@article{osti_5398151,
title = {On structural patterns in H II regions},
author = {Feibelman, W.A.},
abstractNote = {High-resolution photographs of H II regions show that a large number of stars embedded in the nebulosities appear to be surrounded by emply spaces. This phenomenon seems to be quite common but has escaped attention up to now. The effect is not a photographic one, nor does it arise in the half-tone reproduction processes employed in publications, but no satisfactory explanation is apparent. 9 refs.},
doi = {10.1086/132466},
journal = {Publications of the Astronomical Society of the Pacific; (USA)},
number = ,
volume = 101,
place = {United States},
year = {Mon May 01 00:00:00 EDT 1989},
month = {Mon May 01 00:00:00 EDT 1989}
}
  • The contribution to the continuous emission by electron scattering in an H II region (Pottasch's suggestion) was studied. The phenomenon was evaluated for different cases, and compared wtth the contribution due to atomic processes. It was proved, taking into account all the possible variables, that the contribution is neglected for typical H II regions in the Galaxy, and in other galaxies. (auth)
  • Aperture synthesis observations at 21 cm are presented of a group of H II regions situated in a 2 deg x 2 deg area around 1 = 111 deg in the Perseus Arm. The beamwidth used was 24" x 28". The group contains the well known objects NGC 7538, the Bubble Nebula NGC 7635, and S 157. Radial velocity data suggest that all regions are close together. All regions of the group seem to be younger than 10/sup 8/ yr, but their apparent ages vary considerably. In general a very good correlation is found between optical and radio features. Threemore » small H II regions of size approx equal 0.5 pc appear to have emission measures in excess of 10/sup 6/ cm/sup -6/ pc; in this they resemble the Orion nebula. Two regions are of larger size (3 and 7 pc). In addition two optically invisible, point-like sources, that are obscured by local dark matter, are found. Very likely both sources are cocoon stars similar to W 3 OH. The total group of H II regions may be a loose OB association in statu nascendi. (auth)« less
  • A CCD survey at H-alpha results in a catalog of 157 H II regions in the Local Group irregular galaxy NGC 6822. Most of them are newly detected, faint surface-brightness objects. Positions and maps are given, and identifications are correlated with those of previous studies. 10 references.
  • We derive the Mg/H ratio in the Orion nebula and in 30 Doradus. We also derive the O/H and the Fe/O ratios in the extremely metal-poor galaxy SBS 0335-052 E. We estimate the dust depletions of Mg, Si, and Fe in Galactic and extragalactic H II regions. From these depletions we estimate the fraction of O atoms embedded in dust as a function of the O/H ratio. We find an increasing depletion of O with increasing O/H. The O depletion increases from about 0.08 dex, for the metal poorest H II regions known, to about 0.12 dex, for metal-rich Hmore » II regions. This depletion has to be considered to compare nebular with stellar abundances.« less