Planck intermediate results
2016
We present the scaling relation between Sunyaev-Zeldovich (SZ) signal and stellar mass
for almost 260,000 locally brightest galaxies (LBGs) selected from the Sloan Digital Sky
Survey (SDSS). These are predominantly the central galaxies of their dark matter halos. We
calibrate the stellar-to-halo mass conversion using realistic mock catalogues based on the
Millennium Simulation. Applying a multi-frequency matched filter to the Planck
data for each LBG, and averaging the results in bins of stellar mass, we measure
the mean SZ signal down to
M∗ ~ 2 × 1011 M⊙,
with a clear indication of signal at even lower stellar mass. We derive the scaling
relation between SZ signal and halo mass by assigning halo properties from our mock
catalogues to the real LBGs and simulating the Planck observation
process. This relation shows no evidence for deviation from a power law over a halo mass
range extending from rich clusters down to
M500 ~ 2 × 1013 M⊙,
and there is a clear indication of signal down to
M500 ~ 4 × 1012 M⊙.
Planck’s SZdetections in such low-mass halos imply that about a quarter
of all baryons have now been seen in the form of hot halo gas, and that this gas must be
less concentrated than the dark matter in such halos in order to remain consistent with
X-ray observations. At the high-mass end, the measured SZ signal is 20% lower than found
from observations of X-ray clusters, a difference consistent with the magnitude of
Malmquist bias effects that were previously estimated for the X-ray sample.
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