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Title: H I SHELLS AND SUPERSHELLS IN THE I-GALFA H I 21 cm LINE SURVEY. I. FAST-EXPANDING H I SHELLS ASSOCIATED WITH SUPERNOVA REMNANTS

We search for fast-expanding H I shells associated with Galactic supernova remnants (SNRs) in the longitude range l ≈ 32° to 77° using 21 cm line data from the Inner-Galaxy Arecibo L-band Feed Array (I-GALFA) H I survey. Among the 39 known Galactic SNRs in this region, we find such H I shells in 4 SNRs: W44, G54.4-0.3, W51C, and CTB 80. All four were previously identified in low-resolution surveys, and three of those (excluding G54.4-0.3) were previously studied with the Arecibo telescope. A remarkable new result, however, is the detection of H I emission at both very high positive and negative velocities in W44 from the receding and approaching parts of the H I expanding shell, respectively. This is the first detection of both sides of an expanding shell associated with an SNR in H I 21 cm emission. The high-resolution I-GALFA survey data also reveal a prominent expanding H I shell with high circular symmetry associated with G54.4-0.3. We explore the physical characteristics of four SNRs and discuss what differentiates them from other SNRs in the survey area. We conclude that these four SNRs are likely the remnants of core-collapse supernovae interacting with a relatively dense (∼> 1more » cm{sup –3}) ambient medium, and we discuss the visibility of SNRs in the H I 21 cm line.« less
Authors:
;  [1] ; ;  [2] ; ; ;  [3] ;  [4] ;  [5] ;  [6]
  1. Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of)
  2. Department of Physics and Astronomy, Western Kentucky University, Bowling Green, KY 42101 (United States)
  3. Arecibo Observatory, HC 3 Box 53995, Arecibo, PR 00612 (United States)
  4. Department of Astronomy, Columbia University, New York, NY 10027 (United States)
  5. Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)
  6. Radio Astronomy Lab, UC Berkeley, 601 Campbell Hall, Berkeley, CA 94720 (United States)
Publication Date:
OSTI Identifier:
22270704
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 777; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; GALAXIES; HYDROGEN 1; MILKY WAY; RESOLUTION; SUPERNOVA REMNANTS; SUPERNOVAE; SYMMETRY; TELESCOPES