On the Intrinsic Alignments of the Late-Type Spiral Galaxies from the
  Sloan Digital Sky Survey Data Release 7
  A robust detection of the tidally induced intrinsic alignments of the
late-type spiral galaxies with high statistical significance is reported. From
the spectroscopic galaxy sample of SDSS DR7 compiled by Huertas-Company et al.
which lists each galaxy's probabilities of being in five Hubble types,
P(E),P(Ell), P(S0),P(Sab), P(Scd), we select the nearby large late-type spiral
galaxies which have redshifts of 0<=z<=0.02, probabilities of P(Scd)>=0.5 and
angular sizes of D>=7.92 arcsec. The spin axes of the selected nearby large
late-type spiral galaxies are determined up to the two-fold ambiguity with the
help of the circular thin-disk approximation and their spatial correlations are
measured as a function of the separation distance r. A clear signal of the
intrinsic correlation as high as 3.4 sigma and 2.4 sigma is found at the
separation distance of r~1Mpc/h and r~2Mpc/h, respectively. The comparison of
this observational results with the analytic model based on the tidal torque
theory reveals that the spin correlation function for the late-type spiral
galaxies follow the quadratic scaling of the linear density correlation and
that the intrinsic correlations of the galaxy spin axes are stronger than that
of the underlying dark halos. We investigate a local density dependence of the
galaxy spin correlations and found that the correlations are stronger for the
galaxies located in dense regions having more than 10 neighbors within 2Mpc/h.
We also attempt to measure a luminosity dependence of the galaxy spin
correlations, but find that it is impossible with our magnitude-split samples
to disentangle a luminosity from a redshift dependence. We provide the physical
explanations for these observational results and also discuss the effects of
possible residual systematics on the results.
