New data sources are used to assess Lick/IDS feature strength gradients inside the half-light radius R _ { e } of the compact Local Group elliptical galaxy M32 .
A Hubble Space Telescope ( HST ) STIS spectrum seemed to indicate ionized gas and a very young central stellar population .
In fact , this conclusion is entirely spurious because of incomplete removal of ion hits .
More robust ground-based spectra taken at the MDM Observatory are , in contrast , the most accurate measurements of Lick/IDS indices yet obtained for M32 .
All but a few ( of 24 measured ) indices show a statistically significant gradient .
The CN indices show a maximum at 4″ radius , dropping off both toward the nucleus and away from it .
At 2″ radius there is a discontinuity in the surface brightness profile , but this feature is not reflected in any spectral feature .
Comparing with models , the index gradients indicate a mean age and abundance gradient in the sense that the nucleus is a factor of 2.5 younger and a factor of 0.3 dex more metal-rich than at 1 R _ { e } .
This conclusion is only weakly dependent on which index combinations are used and is robust to high accuracy .
Stars near the M32 nucleus have a mean age and heavy element abundance [ M/H ] of ( 4.7 Gyr , +0.02 ) , judging from models by Worthey with variable abundance ratios .
This result has very small formal random errors , although , of course , there is significant age-metallicity degeneracy along an ( age , abundance ) line segment from ( 5.0 Gyr , 0.00 ) to ( 4.5 Gyr , +0.05 ) .
An abundance pattern of [ C/M ] = +0.077 ( carbon abundance affects CN , C _ { 2 } 4668 , and the bluer Balmer features ) , [ N/M ] = -0.13 , [ Mg/M ] = -0.18 , [ Fe/M ] \approx 0.0 , and [ Na/M ] = +0.12 is required to fit the feature data , with a fitting precision of about 0.01 dex ( with two caveats : the [ Fe/M ] guess has about twice this precision because of the relative insensitivity of the Fe5335 feature to iron , and the [ Na/M ] value may be falsely amplified because of interstellar absorption ) .
Model uncertainties make the accuracies of these values at least twice the magnitude of the precision .
Forcing scaled-solar abundances does not change the age very much , but it increases the rms goodness of model-data fit by a factor of 3 and broadens the allowed range of age to \pm 1 Gyr .
The abundance ratios do not show strong trends with radius , except for the nuclear weakening of CN ( measuring mainly N ) mentioned above , which needs reconfirming with better data .
The overall abundance pattern contrasts with larger elliptical galaxies , in which all measurable lighter elements are enhanced relative to iron and calcium .
Nucleosynthetic theory does not provide a ready explanation for these mixtures .