  N2H+ observations of molecular cloud cores in Taurus with the Nobeyama 45 m
radio telescope are reported. We compare ``cores with young stars'' with
``cores without young stars''. The differences in core radius, linewidth, and
core mass are small. Linewidth is dominated by thermal motions in both cases.
N2H+ maps show that the intensity distribution does not differ much between
cores without stars and those with stars. This is in contrast to the result
previously obtained in H13CO+ toward Taurus molecular cloud cores. Larger
degree of depletion of H13CO+ in starless cores will be one possible
explanation for this difference. We studied the physical state of molecular
cloud cores in terms of ``critical pressure'' for the surface (external)
pressure. There is no systematic difference between starless cores and cores
with stars in this analysis. Both are not far from the critical state for
pressure equilibrium. We suggest that molecular cloud cores in which thermal
support is dominated evolve toward star formation by keeping close to the
critical state. This result is in contrast with that obtained in the
intermediate-mass star forming region OMC-2/3, where molecular cloud cores
evolve by decreasing the critical pressure appreciably. We investigate the
radial distribution of the integrated intensity. Cores with stars are found to
have shallow (-1.8 to -1.6) power-law density profiles.
