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  • ASTROPHYSICS  (4)
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  • ASTROPHYSICS  (4)
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  • 1
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    X-ray emission from SN 1986J in NGC 891 (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-14
    Description: Using the Position Sensitive Proportional Counter on ROSAT, we detected soft X-ray emission from SN 1986J in NGC 891 approximately nine years after the supernova event. The X-ray emission is characterized by L(x) (0.1-2.5 keV) = 1.6-7 x 10 exp 40 ergs/s, T(x) = 1.0-3.9 keV, and an absorbing column of 5-14 x 10 exp 21/sq cm. The X-ray luminosity, temperature, and absorption column are reproduced surprisingly well in a model where a reverse shock propagates into the outer layers of the exploded star. The large absorbing column is probably intrinsic to the supernova and represents the cooled gas created by a radiative reverse shock.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 398; 2; p. L107-L110.
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    ROSAT observations of compact groups of galaxies (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: We have systematically analyzed a sample of 13 new and archival ROSAT Position Sensitive Proportional Counter (PSPC) observations of compact groups of galaxies: 12 Hickson compact groups plus the NCG 2300 group. We find that approximately two-thirds of the groups have extended X-ray emission and, in four of these, the emission is resolved into diffuse emission from gas at a temperature of kT approximately 1 keV in the group potential. All but one of the groups with extended emission have a spiral fraction of less than 50%. The baryon fraction of groups with diffuse emission is 5%-19%, similar to the values in clusters of galaxies. However, with a single exception (HCG 62), the gas-to-stellar mass ratio in our groups has a median value near 5%, somewhat greater than the values for individual early-type galaxies and two orders of magnitude than in clusters of galaxies. The X-ray luminosities of individual group galaxies are comparable to those of similar field galaxies, although the L(sub X)-L(sub B) relation for early-type galaxies may be flatter in compact groups than in the field.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 443; 2; p. 514-526
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    NASA TECHNICAL REPORTS
  • 3
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    Extraplanar emission-line gas in edge-on galaxies (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Seven edge-on galaxies were imaged H alpha in order to determine if extraplanar emission-line gas (as seen in NGC 891) is a common feature of spiral galaxies. Four of the seven are found to have one or two prominent filamentary extraplanar structures apiece, with typical filament H alpha luminosities of 10(exp 37)-10(exp 38) ergs s(exp -1) and scales of 1-2 kpc. Unlike NGC 891, none of the galaxies has an extensive emission-line halo, to within the sensitivity of the observations, approximately 24 mag per square arcsec in H-alpha (equivalent to an emission measure of 19 pc cm(exp -6) -- more than 7 times fainter than the diffuse emission of NGC 891.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 427; 1; p. 160-164
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    NASA TECHNICAL REPORTS
  • 4
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    Extraplanar emission-line gas in NGC 891 (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: We have used spectroscopy and high-resolution imaging to study the disk-halo interaction in the edge-on spiral galaxy NGC 891, which is known to have extraplanar gas. H(alpha) imaging of the northeast side of this galaxy reveals diffuse emission-line gas both above and below the plane, as well as new bubble-like structures on 0.5-1 kpc scales emerging from the disk. The diffuse emission is best modeled in the radial direction as a disk of constant emission measure with a sharp cutoff. Long-slit spectroscopy of the H(alpha) line within 2.4 kpc of the galaxy's plane shows departures from the velocity structure found in a model with strict corotation. The departures from corotation range up to 40 km/s, consistent with galactic fountain theory.
    Keywords: ASTROPHYSICS
    Type: The Astrophysical Journal, Part 1 (ISSN 0004-637X); 423; 1; p. 190-195
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    NASA TECHNICAL REPORTS
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