Can intrinsic alignments of elongated low-mass galaxies be used to map
  the cosmic web at high redshift?
  Hubble Space Telescope observations show that low-mass
($M_*=10^9-10^{10}M_{\odot}$) galaxies at high redshift ($z=1.0-2.5$) tend to
be elongated (prolate) rather than disky (oblate) or spheroidal. This is
explained in zoom-in cosmological hydrodynamical simulations by the fact that
these galaxies are forming in cosmic web filaments where accretion happens
preferentially along the direction of elongation. We ask whether the elongated
morphology of these galaxies allows them to be used as effective tracers of
cosmic web filaments at high redshift via their intrinsic alignments. Using
mock lightcones and spectroscopically-confirmed galaxy pairs from the CANDELS
survey, we test two types of alignments: (1) between the galaxy major axis and
the direction to nearby galaxies of any mass, and (2) between the major axes of
nearby pairs of low-mass, likely prolate, galaxies. The mock lightcones predict
strong signals in 3D real space, 3D redshift space, and 2D projected redshift
space for both types of alignments (assuming prolate galaxy orientations are
the same as those of their host prolate halos), but we do not detect
significant alignment signals in CANDELS observations. However, we show that
spectroscopic redshifts have been obtained for only a small fraction of highly
elongated galaxies, and accounting for spectroscopic incompleteness and
redshift errors significantly degrades the 2D mock signal. This may partly
explain the alignment discrepancy and highlights one of several avenues for
future work.
