We investigate the population of cool , evolved stars in the Local Group dwarf elliptical galaxy M32 , using Infrared Array Camera observations from the Spitzer Space Telescope .
We construct deep mid-infrared colour-magnitude diagrams for the resolved stellar populations within 3.5 arcmin of M32 ’ s centre , and identify those stars that exhibit infrared excess .
Our data is dominated by a population of luminous , dust-producing stars on the asymptotic giant branch ( AGB ) and extend to approximately 3 mag below the AGB tip .
We detect for the first time a sizeable population of ‘ extreme ’ AGB stars , highly enshrouded by circumstellar dust and likely completely obscured at optical wavelengths .
The total dust-injection rate from the extreme AGB candidates is measured to be 7.5 \times 10 ^ { -7 } { M } _ { \odot } { yr } ^ { -1 } , corresponding to a gas mass-loss rate of 1.5 \times 10 ^ { -4 } { M } _ { \odot } { yr } ^ { -1 } .
These extreme stars may be indicative of an extended star-formation epoch between 0.2 and 5 Gyr ago .