Iron Kα Emission from the Low-Luminosity Active Galaxies M81 and NGC 4579
Abstract
We report on the XMM-Newton spectroscopy of the low-luminosity active galaxies (LLAGNs) M81 and NGC 4579, both of which have known black hole masses and well-sampled spectral energy distributions (SEDs). The iron Kα line profiles from both LLAGNs can be described in terms of two components: a narrow line at 6.4 keV, and a moderately broad line (FWHM~2×104 km s -1) arising from highly ionized, He-like or H-like species (E~6.8keV). We interpret the broad lines arising from an accretion disk, the inner edge of which is restricted to large radii (rin~100rg). However, the Eddington ratio, L/LEdd, of these sources is 3-4 orders of magnitude lower than that required to photoionize a cold disk to He-like iron. We suggest that the lines can be explained as collisionally ionized X-ray lines arising from the transition region between a hot (radiatively inefficient) flow in the inner regions and a cold disk outside r~100rg. The accretion flow geometry probed by our XMM-Newton observations is consistent with the truncated disk models proposed to explain the SED of LLAGNs.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2004
- DOI:
- 10.1086/383607
- arXiv:
- arXiv:astro-ph/0402327
- Bibcode:
- 2004ApJ...607..788D
- Keywords:
-
- Accretion;
- Accretion Disks;
- Galaxies: Active;
- Galaxies: Individual: Messier Number: M81;
- Galaxies: Individual: NGC Number: NGC 4579;
- X-Rays: Galaxies;
- Astrophysics
- E-Print:
- 8 pages, uses emulateapj5, To apear in ApJ