MULTIFREQUENCY VLBI OBSERVATIONS OF PKS-1413- A VERY YOUNG RADIO GALAXY(135 )

We present high-dynamic range VLBA maps of the radio galaxy/BL Lac obj ect PKS 1413+135 at 3.6, 6, 13, and 18 cm. These observations reveal t hat PKS 1413+135 possesses complex, two-sided parsec-scale structure, similar to that of other compact symmetric objects (CSOs). Its morphol ogy appears to be that of a miniature wide-angle-tail (WAT) radio sour ce, and its total power is at the upper extreme of that seen in WATs. Comparison of these maps with previous data reveals no evidence for su perluminal motion, and supports the hypothesis that the milliarcsecond -scale structure of PKS 1413+135, unlike most BL Lacs and flat radio s pectrum quasars, is not a product of relativistic beaming. However, be aming is likely present within the core seen at 3.6 cm, due to its hig h brightness temperature. These new VLBA maps allow a more precise, bu t not completely unambiguous, interpretation of the various absorption data, suggesting that the A(v)>30 mag is due to a normal molecular cl oud complex in the disk of the optical spiral galaxy at z=0.247, great er than or similar to few kpc away from its nucleus. The absence of sc atter broadening of the core source at 1.6 and 2.3 GHz and the lack of multiple images add to the evidence against the hypothesis (originall y suggested by Stocke et al.) that PKS 1413+135 is background to the s piral galaxy at z=0.247, in which the AGN appears centered. But if the AGN is within the spiral, the absence of reprocessed radiation (e.g., near-IR dust continuum and emission lines) remains difficult to under stand, since the very high extinction is unlikely to cover the entire dust and line emitting regions. Whether within or background to the op tical galaxy, PKS 1413+135 is similar to other CSOs in being a young r adio source (of age less than or similar to 10(4) yr), with evidence f or absorption along our line of sight. (C) 1996 American Astronomical Society.