We present observations of RR Lyrae variables in the Local Group late-type spiral galaxy M33 .
Using the Advanced Camera for Surveys on the Hubble Space Telescope , we have identified 64 ab-type RR Lyraes in M33 .
We have estimated reddenings for these stars based on their minimum light V - I colors and metallicities based on their periods .
From the distributions of these properties , we conclude that the RR Lyraes belong to two populations - one associated with the halo of M33 and the other with its disk .
Given that RR Lyraes are produced by populations older than \sim 10 Gyr , this suggests that not only does the field halo of M33 contain an old component , but so does its disk .
This is one of the best pieces of evidence for the existence of a halo field component in M33 .
Using a relation between RR Lyrae absolute magnitude and metallicity ( M _ { V } ( RR ) = 0.23 [ Fe / H ] +0.93 ) , we estimate a mean distance modulus of \langle ( m - M ) _ { 0 } \rangle = 24.67 \pm 0.08 for M33 .
This places M33 approximately 70 kpc beyond M31 in line-of-sight distance .