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Spectral absorption features can be used to constrain the stellar initialmass function (IMF) in the integrated light of galaxies. Spectral indices usedat low redshift are in the far red, and therefore increasingly hard to detectat higher and higher redshifts as they pass out of atmospheric transmission andCCD detector wavelength windows. We employ IMF-sensitive indices at bluerwavelengths. We stack spectra of red, quiescent galaxies around $z=0.4$, fromthe DEEP2 Galaxy Redshift Survey. The $z=0.4$ red galaxies have 2 Gyr averageages so that they cannot be passively evolving precursors of nearby galaxies.They are slightly enhanced in C and Na, and slightly depressed in Ti. Split byluminosity, the fainter half appears to be older, a result that should bechecked with larger samples in the future. We uncover no evidence for IMFevolution between $z=0.4$ and now, but we highlight the importance of sampleselection, finding that an SDSS sample culled to select archetypal ellipticalgalaxies at z$\sim$0 is offset toward a more bottom heavy IMF. Other samples,including our DEEP2 sample, show an offset toward a more spiral galaxy-likeIMF. All samples confirm that the reddest galaxies look bottom heavy comparedwith bluer ones. Sample selection also influences age-color trends: red,luminous galaxies always look old and metal-rich, but the bluer ones can bemore metal-poor, the same abundance, or more metal-rich, depending on how theyare selected.

Optical spectroscopy and initial mass function of $z=0.4$ red galaxies