  In order to shed light on how galactic properties depend on the intergalactic
medium (IGM) environment traced by the Ly$\alpha$ forest, we observationally
investigate the IGM-galaxy connection using the publicly available 3D IGM
tomography data (CLAMATO) and several galaxy catalogs in the COSMOS field. We
measure the cross-correlation function (CCF) for $570$ galaxies with spec-$z$
measurements and detect a correlation with the IGM up to $50$ $h^{-1}$ comoving
Mpc. We show that galaxies with stellar masses of $10^9-10^{10}$ M$_\odot$ are
the dominant contributor to the total CCF signal. We also investigate CCFs for
several galaxy populations: Ly$\alpha$ emitters (LAEs), H$\alpha$ emitters
(HAEs), [OIII] emitters (O3Es), active galactic nuclei (AGNs), and
submillimeter galaxies (SMGs), and we detect the highest signal in AGNs and
SMGs at large scales ($r\geq5$ $h^{-1}$ Mpc), but in LAEs at small scales
($r<5$ $h^{-1}$ Mpc). We find that they live in various IGM environments --
HAEs trace the IGM in a similar manner to the continuum-selected galaxies, but
LAEs and O3Es tend to reside in higher-density regions. Additionally, LAEs' CCF
is flat up to $r\sim3$ $h^{-1}$ Mpc, indicating that they tend to avoid the
highest-density regions. For AGNs and SMGs, the CCF peak at $r=5-6$ $h^{-1}$
Mpc implies that they tend to be in locally lower-density regions. We suspect
that it is due to the photoionization of IGM HI by AGNs, i.e., the proximity
effect.
