Three LINERs under the Chandra X-ray microscope

Michael Eracleous, Joseph C. Shields, George Chartas, Edward C. Moran

Research output: Contribution to journalArticle

83 Citations (Scopus)

Abstract

We use observations of three galaxies hosting low-ionization nuclear emission-line regions (LINERs; NGC 404, NGC 4736, and NGC 4579) with the Chandra X-Ray Observatory to study their power sources. We find very diverse properties within this small group: NGC 404 has an X-ray faint nucleus with a soft, thermal spectrum; NGC 4736 harbors a plethora of discrete X-ray sources in and around its nucleus; and NGC 4579 has a dominant nuclear point source embedded in a very extended, diffuse nebulosity. From their multiwavelength properties we conclude the following about the power sources in these LINERs: the nucleus of NGC 404 is the site of a weak, compact starburst, whose X-ray emission is due to gas heated by stellar winds and supernovae; NGC 4736 appears to be in a recent or aging starburst phase, where the X-ray emission is dominated by a dense cluster of X-ray binaries; and NGC 4579 is powered by accretion onto a supermassive black hole. We detect 39 discrete sources in NGC 4736 and 21 in NGC 4579, most with Lx > 1037 ergs s-1. One source in the disk of NGC 4579 appears to be an ultraluminous X-ray binary with Lx(2-10 keV) = 9 × 10 39 ergs s-1, but it could also be a background quasar. The most luminous discrete sources have simple power-law spectra, which along with their luminosities suggest that these are X-ray binaries accreting near or above the Eddington rate for a neutron star. By comparing the luminosity functions of discrete X-ray sources in these and other galaxies, we find a potential connection between the age of the stellar population and the slope of the cumulative X-ray luminosity function: galaxies with primarily old stellar populations have steeper X-ray luminosity functions than starburst galaxies. We suggest that this difference results from the contribution of high-mass X-ray binaries from the young stellar population to the upper end of the luminosity function.

Original languageEnglish (US)
Pages (from-to)108-124
Number of pages17
JournalAstrophysical Journal
Volume565
Issue number1 I
DOIs
StatePublished - Jan 20 2002

Fingerprint

microscopes
x rays
luminosity
galaxies
erg
nuclei
young population
starburst galaxies
harbors
stellar winds
quasars
point sources
neutron stars
point source
supernovae
observatories
power law
harbor
ionization
observatory

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Eracleous, M., Shields, J. C., Chartas, G., & Moran, E. C. (2002). Three LINERs under the Chandra X-ray microscope. Astrophysical Journal, 565(1 I), 108-124. https://doi.org/10.1086/324394
Eracleous, Michael ; Shields, Joseph C. ; Chartas, George ; Moran, Edward C. / Three LINERs under the Chandra X-ray microscope. In: Astrophysical Journal. 2002 ; Vol. 565, No. 1 I. pp. 108-124.
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Eracleous, M, Shields, JC, Chartas, G & Moran, EC 2002, 'Three LINERs under the Chandra X-ray microscope', Astrophysical Journal, vol. 565, no. 1 I, pp. 108-124. https://doi.org/10.1086/324394

Three LINERs under the Chandra X-ray microscope. / Eracleous, Michael; Shields, Joseph C.; Chartas, George; Moran, Edward C.

In: Astrophysical Journal, Vol. 565, No. 1 I, 20.01.2002, p. 108-124.

Research output: Contribution to journalArticle

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N2 - We use observations of three galaxies hosting low-ionization nuclear emission-line regions (LINERs; NGC 404, NGC 4736, and NGC 4579) with the Chandra X-Ray Observatory to study their power sources. We find very diverse properties within this small group: NGC 404 has an X-ray faint nucleus with a soft, thermal spectrum; NGC 4736 harbors a plethora of discrete X-ray sources in and around its nucleus; and NGC 4579 has a dominant nuclear point source embedded in a very extended, diffuse nebulosity. From their multiwavelength properties we conclude the following about the power sources in these LINERs: the nucleus of NGC 404 is the site of a weak, compact starburst, whose X-ray emission is due to gas heated by stellar winds and supernovae; NGC 4736 appears to be in a recent or aging starburst phase, where the X-ray emission is dominated by a dense cluster of X-ray binaries; and NGC 4579 is powered by accretion onto a supermassive black hole. We detect 39 discrete sources in NGC 4736 and 21 in NGC 4579, most with Lx > 1037 ergs s-1. One source in the disk of NGC 4579 appears to be an ultraluminous X-ray binary with Lx(2-10 keV) = 9 × 10 39 ergs s-1, but it could also be a background quasar. The most luminous discrete sources have simple power-law spectra, which along with their luminosities suggest that these are X-ray binaries accreting near or above the Eddington rate for a neutron star. By comparing the luminosity functions of discrete X-ray sources in these and other galaxies, we find a potential connection between the age of the stellar population and the slope of the cumulative X-ray luminosity function: galaxies with primarily old stellar populations have steeper X-ray luminosity functions than starburst galaxies. We suggest that this difference results from the contribution of high-mass X-ray binaries from the young stellar population to the upper end of the luminosity function.

AB - We use observations of three galaxies hosting low-ionization nuclear emission-line regions (LINERs; NGC 404, NGC 4736, and NGC 4579) with the Chandra X-Ray Observatory to study their power sources. We find very diverse properties within this small group: NGC 404 has an X-ray faint nucleus with a soft, thermal spectrum; NGC 4736 harbors a plethora of discrete X-ray sources in and around its nucleus; and NGC 4579 has a dominant nuclear point source embedded in a very extended, diffuse nebulosity. From their multiwavelength properties we conclude the following about the power sources in these LINERs: the nucleus of NGC 404 is the site of a weak, compact starburst, whose X-ray emission is due to gas heated by stellar winds and supernovae; NGC 4736 appears to be in a recent or aging starburst phase, where the X-ray emission is dominated by a dense cluster of X-ray binaries; and NGC 4579 is powered by accretion onto a supermassive black hole. We detect 39 discrete sources in NGC 4736 and 21 in NGC 4579, most with Lx > 1037 ergs s-1. One source in the disk of NGC 4579 appears to be an ultraluminous X-ray binary with Lx(2-10 keV) = 9 × 10 39 ergs s-1, but it could also be a background quasar. The most luminous discrete sources have simple power-law spectra, which along with their luminosities suggest that these are X-ray binaries accreting near or above the Eddington rate for a neutron star. By comparing the luminosity functions of discrete X-ray sources in these and other galaxies, we find a potential connection between the age of the stellar population and the slope of the cumulative X-ray luminosity function: galaxies with primarily old stellar populations have steeper X-ray luminosity functions than starburst galaxies. We suggest that this difference results from the contribution of high-mass X-ray binaries from the young stellar population to the upper end of the luminosity function.

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