Other
Scientific paper
Dec 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003aas...203.6307p&link_type=abstract
American Astronomical Society Meeting 203, #63.07; Bulletin of the American Astronomical Society, Vol. 35, p.1310
Other
Scientific paper
We present the results of an ongoing Chandra and XMM-Newton survey of galactic nuclei with known black hole masses and well-sampled spectral energy distributions, with emphasis here on our best-studied case, NGC 3998, a ``type 1'' LINER galaxy (i.e., with significant broad Hα emission). Our goal is to test the extent to which radiatively inefficient accretion flow (RIAF) models and/or scaled-down AGN models are consistent with the observed properties of these galaxies. The XMM-Newton data, when simultaneously fitted with archival ASCA\ and BeppoSAX, data show that the 0.1--100 keV X-ray spectrum of NGC 3998 is consistent with a simple power-law model with a photon index of ˜ 1.9, and this power-law also extrapolates to the UV flux determined with the OM. The upper-limit for narrow Fe-K emission is ˜ 24 eV, which is one of the strictest limits to date for any AGN. This significantly rules out Fe-K emission as is expected to be observed in typical Seyfert 1 galaxies. The hard X-ray flux of NGC 3998 has not been observed to vary significantly (at >30% level) either between or within the X-ray observations, which is also in contrast to typical Seyfert 1 galaxies. The mid-IR to X-ray SED is consistent with a RIAF along with an outer, truncated thin disk. However the optical to X-ray SED is also consistent with a Comptonized thin disk with a very low (˙ {M} < 10-5}˙ {M Edd) accretion rate. Accretion disk models in general do not account for the observed radio flux of NGC 3998 which is probably dominated by a jet, and a jet may also be contributing at shorter wavelengths. We will also discuss a possible OM U-band counterpart for the ULX in NGC 3998. Preliminary Chandra results for the other galaxies in our sample will be presented.
Ho Luis C.
Ptak Andrew
Quataert Eliot
Terashima Yoshinosuke
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