NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Collections About News Help Login
Back to Results
ROSAT detection of diffuse hot gas in the edge-on galaxy NGC 4631ROSAT observation is presented of the edge-on spiral galaxy NGC 4631, a nearby Sc/SBd galaxy best known for its extended radio halo. Because of the low foreground Galactic X-ray-absorbing gas column density, N(sub H) approximately 1.4 x 10(exp 20)cm(exp -2), this observation is sensitive to gas of temperature greater than or equal to a few times 10(exp 5) K. A soft (approximately 0.25 keV) X-ray radiation out to more than 8 kpc above the midplane of the galaxy was detected. The strongest X-ray emission in the halo is above the central disk, a region of about 3 kpc radius which shows high star formation activity. The X-ray emission in the halo is bordered by two extended filaments of radio continuum emission. Diffuse X-ray emission from hot gas in the galaxy's disk was found. The spectrum of the radiation can be characterized by a thermal plasma with a temperature of 3 x 10(exp 6) K and a radiative cooling rate of approximately 8 x 10(exp 39) ergs s(exp -1). This rate is only a few percent of the estimated supernova energy release in the interstellar medium of the galaxy. Analysis of the X-ray spectrum shows evidence for the presence of a cooler (several times 10(exp 5) K) halo gas component that could consume a much larger fraction of the supernova energy. Strong evidence was found for disk/halo interaction. Hot gas apparently blows out from supershells in the galaxy's disk at a rate of approximately 1 solar mass yr(exp -1). This outflow of hot gas drags magnetic field lines up in the halo and forms a magnetized gaseous halo. If the magnetic field lines are still anchored to the disk gas at large disk radii, the outflowing gas may be confined high above the disk by magnetic pressure. A strong X-ray source which coincides spatially with an H I supershell has been identified. However, the source is likely an extremely luminous X-ray binary with L(sub chi)(0.1 - 2 keV) approximately 5 x 10(exp 39) ergs s(exp -1), which makes it a stellar mass black hole candidate.
Document ID
19950011081
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Wang, Q. David (Colorado Univ. Boulder, CO, United States)
Walterbos, Rene A. M. (New Mexico State Univ. Las Cruces, NM., United States)
Steakley, Michael F. (New Mexico State Univ. Las Cruces, NM., United States)
Norman, Colin A. (Johns Hopkins Univ. Baltimore, MD., United States)
Braun, Robert (Netherlands Foundation for Research in Astronomy Dwingelo, Netherlands)
Date Acquired
September 6, 2013
Publication Date
January 1, 1994
Subject Category
Astronomy
Report/Patent Number
NAS 1.26:197535
NASA-CR-197535
Accession Number
95N17496
Funding Number(s)
CONTRACT_GRANT: NSF AST-91-23777
CONTRACT_GRANT: NAG5-1924
CONTRACT_GRANT: NAG5-1Y29
CONTRACT_GRANT: NAG5-2014
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

Related Records

There are no records associated with this record.
No Preview Available