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The Seyfert galaxy NGC 985 is known to show a high-frequency excess in itsradio continuum spectrum in a milli-Jansky level on the basis of previousobservations at 1.4--15 GHz; a steep spectrum at low frequencies (a spectralindex of $\alpha=-1.10 \pm 0.03$) changes at ~10 GHz into an inverted spectrumat higher frequencies ($\alpha=+0.86 \pm 0.09$). We conduct new observations at15--43 GHz using the Very Large Array and at 100 GHz using the NobeyamaMillimeter Array. As a result, the high-frequency excess continuing at evenhigher radio frequencies up to 43 GHz has been confirmed. The non-detection at100 GHz was not so strong constraint, and therefore the spectral behavior above43 GHz remains unclear. The astrometric position of the high-frequency excesscomponent coincides with the optical position of the Seyfert nucleus and thelow-frequency radio position to an accuracy of 0.1 arcsec, corresponding to ~80pc; the radio source size is constrained to be <0.02 arcsec, corresponding to<16 pc. We discuss the physical origin of the observed high-frequency excesscomponent. Dust emission at the Rayleigh-Jeans regime, free--free emission fromX-ray radiating high-temperature plasma, free--free emission from the ensembleof broad-line region clouds, or thermal synchrotron from hot accretion flowcannot be responsible for the observed radio flux. Compact jets undersynchrotron self-absorption may be unlikely in terms of observed time scales.Alternatively, we cannot rule out the hypotheses of synchrotron jets free--freeabsorbed by a circumnuclear photo-ionized region, and self-absorbed nonthermalsynchrotron from disk corona, as the origin of the high-frequency excesscomponent.

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