High-frequency excess in the radio continuum spectrum of the type-1 Seyfert galaxy NGC 985

摘要: The Seyfert galaxy NGC 985 is known to show a high-frequency excess in its radio continuum spectrum milli-Jansky level on the basis of previous observations at 1.4--15 GHz; steep low frequencies (a spectral index $\alpha=-1.10 \pm 0.03$) changes ~10 GHz into an inverted higher ($\alpha=+0.86 0.09$). We conduct new 15--43 using Very Large Array and 100 Nobeyama Millimeter Array. As result, continuing even up 43 has been confirmed. non-detection was not so strong constraint, therefore behavior above remains unclear. astrometric position component coincides with optical nucleus low-frequency accuracy 0.1 arcsec, corresponding ~80 pc; source size constrained be <0.02 <16 pc. discuss physical origin observed component. Dust emission Rayleigh-Jeans regime, free--free from X-ray radiating high-temperature plasma, ensemble broad-line region clouds, or thermal synchrotron hot accretion flow cannot responsible for flux. Compact jets under self-absorption may unlikely terms time scales. Alternatively, we rule out hypotheses absorbed by circumnuclear photo-ionized region, self-absorbed nonthermal disk corona, as