Detection of missing baryons in galaxy groups with kinetic
  Sunyaev-Zel'dovich effect
  We present the detection of the kinetic Sunyaev-Zel'dovich effect (kSZE)
signals from groups of galaxies as a function of halo mass down to $\log
(M_{500}/{\rm M_\odot}) \sim 12.3$, using the {\it Planck} CMB maps and
stacking about $40,000$ galaxy systems with known positions, halo masses, and
peculiar velocities. The signals from groups of different mass are constrained
simultaneously to take care of projection effects of nearby halos. The total
kSZE flux within halos estimated implies that the gas fraction in halos is
about the universal baryon fraction, even in low-mass halos, indicating that
the `missing baryons' are found. Various tests performed show that our results
are robust against systematic effects, such as contamination by infrared/radio
sources and background variations, beam-size effects and contributions from
halo exteriors. Combined with the thermal Sunyaev-Zel'dovich effect, our
results indicate that the `missing baryons' associated with galaxy groups are
contained in warm-hot media with temperatures between $10^5$ and $10^6\,{\rm
K}$.
