Soft X-ray diffuse background: implications for the nature of the Local Interstellar Medium

Technical Report · Thu Nov 01 00:00:00 EST 1984

OSTI ID:5941010

Mccammon, D

Observations of the diffuse X-ray background in the B and C bands (130-188 eV and 160-284 eV, respectively) provide convincing evidence for the existence of high-temperature interstellar gas. Since the opacity of normal interstellar material is very high, it is assumed that the soft X-ray flux observed in the galactic plane originates within a few hundred parsecs of the Sun. The intensity and B/C ratio of this low-latitude flux can be provided by emission from an equilibrium plasma with normal abundances, T 10 to the 6th power K, and 0.0019 cm(-6) pc emission measure. More sophisticated nonequilibrium models of material heated by a supernova blast wave would reduce the required emission measure somewhat, but not by so much as a factor of two. Arbitrarily limiting the pressure to 10 to the 4th power cm(-3) K gives a maximum density of 0.005 cm(-3) and a minimum radius for the emitting region of 75 pc. This fits in well with ultraviolet interstellar absorption measurements which indicate that the interstellar medium is very deficient in neutral hydrogen out to approx. 100 pc from the Sun.

• Research Organization: Wisconsin Univ., Madison (USA)
• OSTI ID: 5941010
• Report Number(s): N-85-15566
• Resource Relation: Other Information: In NASA, Goddard Space Flight Center, Local Interstellar Medium, No. 81, 195-203p. (N--85-15539 06-90)
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COSMIC GASES
SOFT X RADIATION
INTERSTELLAR SPACE
HIGH TEMPERATURE
ABSORPTION SPECTRA
BACKGROUND RADIATION
EMISSION SPECTRA
FLUX DENSITY
SOLAR ACTIVITY
ELECTROMAGNETIC RADIATION
FLUIDS
GASES
IONIZING RADIATIONS
RADIATIONS
SPACE
SPECTRA
X RADIATION
640105* - Astrophysics & Cosmology- Galaxies