  Quantum Monte Carlo (QMC) simulations of correlated electron systems provide
unbiased information about system behavior at a quantum critical point (QCP)
and can verify or disprove the existing theories of non-Fermi liquid (NFL)
behavior at a QCP. However, simulations are carried out at a finite
temperature, where quantum-critical features are masked by finite temperature
effects. Here we present a theoretical framework within which it is possible to
separate thermal and quantum effects and extract the information about NFL
physics at $T=0$. We demonstrate our method for a specific example of 2D
fermions near a Ising-ferromagnetic QCP. We show that one can extract from QMC
data the zero-temperature form of fermionic self-energy $\Sigma (\omega)$ even
though the leading contribution to the self-energy comes from thermal effects.
We find that the frequency dependence of $\Sigma (\omega)$ agrees well with the
analytic form obtained within the Eliashberg theory of dynamical quantum
criticality, and obeys $\omega^{2/3}$ scaling at low frequencies. Our results
open up an avenue for QMC studies of quantum-critical metals.
