The Jets of TeV Blazars at Higher Resolution: 43 GHz and Polarimetric
  VLBA Observations from 2005-2009
  We present 23 new VLBA images of the six established TeV blazars Markarian
421, Markarian 501, H 1426+428, 1ES 1959+650, PKS 2155-304, and 1ES 2344+514,
obtained from 2005 to 2009. Most images were obtained at 43 GHz, and they
reveal the parsec-scale structures of three of these sources (1ES 1959+650, PKS
2155-304, and 1ES 2344+514) at factors of two to three higher resolution than
has previously been attained. Most of the remaining images map the linear
polarization structures at a lower frequency of 22 GHz. We discuss the
transverse structures of the jets as revealed by the high-frequency and
polarimetric imaging. The transverse structures include significant
limb-brightening in Mrk 421, and spine-sheath structures in the electric vector
position angle (EVPA) and fractional polarization distributions in Mrk 421, Mrk
501, and 1ES 1959+650. We use new measured component positions to update
measured apparent jet speeds, in many cases significantly reducing the
statistical error over previously published results. With the increased
resolution at 43 GHz, we detect new components within 0.1-0.2 mas of the core
in most of these sources. No motion is apparent in these new components over
the time span of our observations, and we place upper limits on the apparent
speeds of the components near the core of less than 2c. From those limits, we
conclude that Gamma2 < Gamma1^{1/2} at about 10^5 Schwarzschild radii, where
Gamma1 and Gamma2 are the bulk Lorentz factors in the TeV-emitting and 43
GHz-emitting regions, respectively, assuming that their velocity vectors are
aligned.
