  The connection between galaxies and dark matter halos is often quantified
using the stellar mass-halo mass (SMHM) relation. Optical and near-infrared
imaging surveys have led to a broadly consistent picture of the evolving SMHM
relation based on measurements of galaxy abundances and angular correlation
functions. Spectroscopic surveys at $z \gtrsim 2$ can also constrain the SMHM
relation via the galaxy autocorrelation function and through the
cross-correlation between galaxies and Ly$\alpha$ absorption measured in
transverse sightlines; however, such studies are very few and have produced
some unexpected or inconclusive results. We use $\sim$3000 spectra of
$z\sim2.5$ galaxies from the Lyman-alpha Tomography IMACS Survey (LATIS) to
measure the galaxy-galaxy and galaxy-Ly$\alpha$ correlation functions in four
bins of stellar mass spanning $10^{9.2} \lesssim M_* / M_{\odot} \lesssim
10^{10.5}$. Parallel analyses of the MultiDark N-body and ASTRID hydrodynamic
cosmological simulations allow us to model the correlation functions, estimate
covariance matrices, and infer halo masses. We find that results of the two
methods are mutually consistent and are broadly in accord with standard SMHM
relations. This consistency demonstrates that we are able to accurately measure
and model Ly$\alpha$ transmission fluctuations $\delta_F$ in LATIS. We also
show that the galaxy-Ly$\alpha$ cross-correlation, a free byproduct of optical
spectroscopic galaxy surveys at these redshifts, can constrain halo masses with
similar precision to galaxy-galaxy clustering.
