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Session 104 - Radio Galaxies, Radio Observations of AGN Jets & Outflows.
Display session, Saturday, January 10
Exhibit Hall,

[104.02] A VLBA Map of the H_2O Maser in the Nucleus of Seyfert 2 Galaxy NGC 1386

J. Braatz, L. Greenhill, J. Moran (CfA), A. Wilson (U. Maryland), J. Herrnstein (NRAO)

Water vapor megamasers have so far been detected towards the nuclei of 20 galaxies, all of which have an active galactic nucleus (AGN). One of the maser sources is the southern Seyfert 2 galaxy NGC 1386 which, at a distance of 16.9 Mpc, is among the nearest AGNs. The single-dish spectrum of the maser in NGC 1386 shows a broad (FWHM \simeq 45 km s^-1) emission feature at about the systemic velocity of the galaxy and two narrow (FWHM \simeq 4 km s^-1) features redshifted by \sim 100 km s^-1. We have mapped the water masers in NGC 1386 with the VLBA + phased VLA and we find a roughly linear structure which extends over 15 mas (1.2 pc). The narrow lines originate in ``clouds'' northeast of the broad feature. Although the linear extension of the masers in NGC 1386 is reminiscent of the thin, rotating disks revealed by VLBI observations of masers in other galaxies, the velocity signature of the masers is complex and does not clearly indicate a rotating structure. Surprisingly, the masers are aligned nearly parallel to the \sim 200 pc elongation of 6 cm continuum emission. The cloud producing the broad line maser emission is marginally resolved at the 0.1 pc scale and shows a velocity gradient on the sky along p.a. 67^\circ. Continuum emission at 1.3 cm was not detected by this observation.

Program listing for Saturday