NGC 7582: The Prototype Narrow-Line X-Ray Galaxy
Abstract
NGC 7582 is a candidate prototype of the narrow line X-ray galaxies (NLXGs) found in deep X-ray surveys. An ASCA observation shows the hard (>3 keV) X-ray continuum of NGC 7582 drops 40% in ~6 ks, implying an active galactic nucleus (AGN), while the soft band (<3 keV) does not drop in concert with the hard continuum, requiring a separate component. The X-ray spectrum of NGC 7582 also shows a clear 0.5-2 keV soft (kT=0.8+0.9-0.3 keV or Γ=2.4+/-0.6 LX=6×1040 ergs s-1) low-energy component, in addition to a heavily absorbed [NH=(6+/-2)×1022 cm-2] and variable 2-10 keV power law [Γ=0.7+0.3-0.4 LX=(1.7-2.3)×1042 ergs s-1]. This is one of the flattest 2-10 keV slopes in any AGN observed with ASCA. (The ROSAT HRI image of NGC 7582 further suggests extent to the SE.) These observations make it clear that the hard X-ray emission of NGC 7582, the most ``narrow-line'' of the NLXGs, is associated with an AGN. The strong suggestion is that all NLXGs are obscured AGNs, as hypothesized to explain the X-ray background spectral paradox. The separate soft X-ray component makes NGC 7582 (and by extension other NLXGs) detectable as a ROSAT source.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 1998
- DOI:
- 10.1086/311537
- arXiv:
- arXiv:astro-ph/9806275
- Bibcode:
- 1998ApJ...503L.123S
- Keywords:
-
- GALAXIES: ACTIVE;
- GALAXIES: SEYFERT;
- X-RAYS: GALAXIES;
- GALAXIES: BL LACERTAE OBJECTS: GENERAL;
- Galaxies: BL Lacertae Objects: General;
- Galaxies: Active;
- Galaxies: Seyfert;
- X-Rays: Galaxies;
- Astrophysics
- E-Print:
- text: Latex2e 10 pages, including 1 table, and 2 postscript figures via psfig