High-Resolution X-Ray Spectroscopy of Four Active Galaxies: Probing the Intercloud Medium
Abstract
The focal plane crystal spectrometer (FPCS) on the Einstein Observatory has been used to perform a high-resolution spectroscopic search for oxygen X-ray line emission from four active galaxies: Fairall 9, Mrk 421, Mrk 501, and PKS 0548-322. Specifically, we searched for O VIII Lyα and Lyβ, whose unredshifted energies are 653 and 775 eV, respectively. No narrow-line emission was detected within the energy bands searched. We supplemented the FPCS results with data acquired simultaneously by the Einstein Monitor Proportional Counter (MPC) and obtained power-law fits to the continuum spectra from these sources. We calculate upper limits on the line flux from these sources of <~ 30 eV equivalent width and use a photoionization model to place corresponding upper limits on the densities of diffuse gas surrounding the active nuclei. The upper limits on gas density range from ~ 0.02-50 cm^-3^ and probe various radial distances from the central source. This is the first time high-resolution X-ray spectroscopy has been used to place constraints on the intercloud medium in active galaxies.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1990
- DOI:
- 10.1086/168968
- Bibcode:
- 1990ApJ...358..139L
- Keywords:
-
- Active Galaxies;
- Galactic Nuclei;
- Interstellar Matter;
- Molecular Clouds;
- X Ray Astronomy;
- X Ray Spectroscopy;
- Astronomical Models;
- Emission Spectra;
- High Resolution;
- Line Spectra;
- Oxygen;
- Photoionization;
- Astrophysics;
- GALAXIES: NUCLEI;
- GALAXIES: X-RAYS