We investigate the Initial Mass Function and mass segregation in super–star cluster M82-F with high resolution Keck/NIRSPEC echelle spectroscopy .
Cross-correlation with template supergiant spectra provides the velocity dispersion of the cluster , enabling measurement of the kinematic ( virial ) mass of the cluster when combined with sizes from NICMOS and ACS images .
We find a mass of 6.6 \pm 0.9 \times 10 ^ { 5 } M _ { \odot } based on near-IR light and 7.0 \pm 1.2 \times 10 ^ { 5 } M _ { \odot } based on optical light .
Using PSF-fitting photometry , we derive the cluster ’ s light-to-mass ( L / M ) ratio in both near-IR and optical light , and compare to population synthesis models .
The ratios are inconsistent with a normal stellar initial mass function for the adopted age of 40–60 Myr , suggesting a deficiency of low-mass stars within the volume sampled .
King model light profile fits to new HST/ACS images of M82-F , in combination with fits to archival near-IR images , indicate mass segregation in the cluster .
As a result , the virial mass represents a lower limit on the mass of the cluster .