Possible detection of the M31 rotation in WMAP data
  Data on the cosmic microwave background (CMB) radiation by the Wilkinson
Microwave Anisotropy Probe (WMAP) had a profound impact on the understanding of
a variety of physical processes in the early phases of the Universe and on the
estimation of the cosmological parameters. Here, the 7-year WMAP data are used
to trace the disk and the halo of the nearby giant spiral galaxy M31. We
analyzed the temperature excess in three WMAP bands (W, V, and Q) by dividing
the region of the sky around M31 into several concentric circular areas. We
studied the robustness of the detected temperature excess by considering 500
random control fields in the real WMAP maps and simulating 500 sky maps from
the best-fitted cosmological parameters. By comparing the obtained temperature
contrast profiles with the real ones towards the M31 galaxy, we find that the
temperature asymmetry in the M31 disk is fairly robust, while the effect in the
halo is weaker. An asymmetry in the mean microwave temperature in the M31 disk
along the direction of the M31 rotation is observed with a temperature contrast
up to about 130 microK/pixel. We also find a temperature asymmetry in the M31
halo, which is much weaker than for the disk, up to a galactocentric distance
of about 10 degrees (120 kpc) with a peak temperature contrast of about 40
microK/pixel. Although the confidence level of the signal is not high, if
estimated purely statistically, which could be expected due to the weakness of
the effect, the geometrical structure of the temperature asymmetry points
towards a definite effect modulated by the rotation of the M31 halo. This
result might open a new way to probe these relatively less studied galactic
objects using high-accuracy CMB measurements, such as those with the Planck
satellite or planned balloon-based experiments, which could prove or disprove
our conclusions.
