The suggestion by Zaritsky & Lin ( 1997 ; ZL ) that a vertical extension of the red clump feature in color-magnitude diagrams ( CMDs ) of the Large Magellanic Cloud ( LMC ) is consistent with a significant population of foreground stars to the LMC that could account for the observed microlensing optical depth ( Renault et al . 1997 ; Alcock et al . 1997a ) has been challenged by various investigators ( cf .
Alcock et al . 1997b , Gallart 1998 , Bennett 1998 , Gould 1998 , Beaulieu & Sackett 1998 , and Ibata , Lewis , & Beaulieu 1998 ) .
We respond by ( 1 ) examining each of the challenges presented to determine whether any or all of those arguments invalidate the claims made by ZL and ( 2 ) presenting new photometric and spectroscopic data obtained in an attempt to resolve this issue .
We systematically discuss why the objections raised so far do not unequivocally refute ZL ’ s claim .
We conclude that although the CMD data do not mandate the existence of a foreground population , they are entirely consistent with a foreground population associated with the LMC that contributes significantly ( \sim 50 % ) to the observed microlensing optical depth .
From our new data , we conclude that \mathrel { \hbox to 0.0 pt { \lower 3.0 pt \hbox { $ \mathchar 536 $ } \hss } \raise 2.0 pt% \hbox { $ \mathchar 316 $ } } 40 % of the VRC stars are young , massive red clump stars because ( 1 ) synthetic color-magnitude diagrams created using the star formation history derived indepdently from HST data ( Geha et al . 1998 ) suggest that < 50 % of the VRC stars are young , massive red clump stars , ( 2 ) the angular distribution of the VRC stars is more uniform than that of the young ( age < 1 Gyr ) main sequence stars , and ( 3 ) the velocity dispersion of the VRC stars in the region of the LMC examined by ZL , 18.4 \pm 2.8 km sec ^ { -1 } ( 95 % confidence limits ) , is inconsistent with the expectation for a young disk population .
Each of these arguments is predicated on assumptions and the conclusions are uncertain .
Therefore , an exact determination of the contribution to the microlensing optical depth by the various hypothesized foreground populations , and the subsequent conclusions regarding the existence of halo MACHOs , requires a detailed knowledge of many complex astrophysical issues , such as the IMF , star formation history , and post-main sequence stellar evolution .