Regarding the Line-of-Sight Baryonic Acoustic Feature in the Sloan
  Digital Sky Survey and Baryon Oscillation Spectroscopic Survey Luminous Red
  Galaxy Samples
  We analyze the line-of-sight baryonic acoustic feature in the two-point
correlation function {\xi} of the Sloan Digital Sky Survey (SDSS) luminous red
galaxy (LRG) sample (0.16 < z < 0.47). By defining a narrow line-of-sight
region, rp < 5.5 Mpc/h, where rp is the transverse separation component, we
measure a strong excess of clustering at ~ 110 Mpc/h, as previously reported in
the literature. We also test these results in an alternative coordinate system,
by defining the line-of-sight as {\theta} < 3{\deg}, where {\theta} is the
opening angle. This clustering excess appears much stronger than the feature in
the better-measured monopole. A fiducial {\Lambda}CDM non-linear model in
redshift-space predicts a much weaker signature. We use realistic mock catalogs
to model the expected signal and noise. We find that the line-of-sight
measurements can be explained well by our mocks as well as by a featureless
{\xi} = 0. We conclude that there is no convincing evidence that the strong
clustering measurement is the line-of-sight baryonic acoustic feature. We also
evaluate how detectable such a signal would be in the upcoming Baryon
Oscillation Spectroscopic Survey LRG volume (BOSS). Mock LRG catalogs (z < 0.6)
suggest that: (i) the narrow line- of-sight cylinder and cone defined above
probably will not reveal a detectable acoustic feature in BOSS; (ii) a
clustering measurement as high as that in the current sample can be ruled out
(or confirmed) at a high confidence level using a BOSS-sized data set; and
(iii) an analysis with wider angular cuts, which provide better signal-to-noise
ratios, can nevertheless be used to compare line-of-sight and transverse
distances, and thereby constrain the expansion rate H(z) and diameter distance
DA(z).
