Galaxy Orientation and Alignment Effects in the SDSS DR6
  We identify, categorize, and quantify alignment effects among host and
satellite galaxies using a spectroscopically-confirmed, low-redshift (z<0.23)
galaxy sample from the Sloan Digital Sky Survey Data Release 6. Consistent with
other recent findings, we find that satellite galaxies (SGs) of red, centrally
concentrated (elliptical) host galaxies (HGs) with radial velocity separation
|Delta_V|<600 km/s preferentially reside near the projected major axes of their
HGs. Among these, this preference is strongest for highly concentrated, red
SGs. We find that fractional anisotropy increases with decreasing \Delta_V and
Delta_R and is nearly 40% greater among the closest SGs (Delta_R<250 kpc/h)
relative to more distant (Delta_R>500 kpc/h) SGs. For highly concentrated SGs
at small (<300 kpc/h) projected separation, we observe a strong radial
(hostward) alignment signal in isophotal position angles (PAs) due to isophotal
twisting and contamination that is not present when using galaxy model PAs.
Among objects for which both isophotal and galaxy model PAs agree to <15
degrees, this elongation signal is significantly weaker. We also investigate
the "Holmberg Effect," a well-known result wherein nearby (<40 kpc/h) SGs of
large, inclined spiral HGs were seen to preferentially reside near the minor
axes of their HGs. Survey limitations preclude a strict test of this effect
using only SDSS spectroscopic galaxies. By adopting a looser set of cuts than
those of Holmberg's study, we recover a comparable preference among faint blue
SGs for the HG minor axis at marginal significance (~3 sigma). We conclude that
several types of alignment likely exist among different galaxy populations, but
that the observed nature and strength of alignment trends depend sensitively on
both selection criteria and on the method used to determine galaxy orientation.
