The Astronomical Journal
We present spectroscopic observations of 26 galaxies of type E and S0, based on their blue morphologies, located in voids by the study of Grogin & Geller in 1999. Measurements of redshift, velocity dispersion, and four Lick line indices, Mg b , Fe5270, Fe5335, and Hβ with their errors are given for all of these galaxies, along with Hβ, [O III], Hα, and [N II] emission line strengths for a subset of these objects. These sources are brighter than M* for low-density regions and tend to be bluer than their counterpart early-type objects in high-density regions. Using the models of Thomas et al., developed in 2003, gives metal abundances and ages with a median α enhancement, [α/Fe] = +0.13, and median metal abundance, [Z/H] = +0.22, values comparable to those found for E and S0 galaxies in clusters, but with a wider spread in [Z/H] toward low values. If the emission line subsample is interpreted as younger, the proportion of young objects is higher than for early types in higher-density regions. There is a significant incidence of sources in the sample with emission lines in their spectra (46% with Hβ and [O III] and 69% with Hα or [N II]) as well as shells and rings in their morphologies (19%). The diagnostic , diagram places 10 of 12 emission line galaxies in or near the star-forming and liner region and two among the Seyferts. The Hα fluxes indicate star-formation rates of 0.2-1.0 M ☉ yr–1. The percentage of these early-type void galaxies undergoing star formation appears to be higher compared to their cluster counterparts and the range of ages wider.
Wegner, Gary and Grogin, Norman A., "Ages and Metallicities of Early-Type Void Galaxies from Line Strength Measurements" (2008). Open Dartmouth: Faculty Open Access Articles. 2086.