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We describe the construction and study of an objectively-defined sample of early-type galaxies in low-density environments. The sample galaxies are selected from a recently-completed redshift survey using uniform and readily-quantified isolation criteria, and are drawn from a sky area of ~700 deg^2, to a depth of 7000 k/ms and an apparent magnitude limit of b_J < 16.1. Their early-type (E/S0) morphologies are confirmed by subsequent CCD imaging. Five out of the nine sample galaxies show signs of morphological peculiarity such as tidal debris or blue circumnuclear rings. We confirm that E/S0 galaxies are rare in low-density regions, accounting for only ~8% of the total galaxy population in such environments. We present spectroscopic observations of nine galaxies in the sample, which are used, in conjunction with updated stellar population models, to investigate star-formation histories. Environmental effects on early-type galaxy evolution are investigated by comparison with a sample of Fornax cluster E/S0s. Results from both samples are compared with predictions from semi-analytic galaxy formation models. The Mg-sig relation of E/S0s in low-density regions is shown to be indistinguishable from that of the Fornax sample. Luminosity-weighted stellar ages and metallicities are determined by considering various combinations of line-indices. At a given luminosity, the E/S0 galaxies in low-density regions are younger than the E/S0s in clusters (by ~2-3 Gyr), and also more metal-rich (by ~0.2 dex). We infer that an anti-correlation of age and metallicity effects is responsible for maintaining the zero-point of the Mg-sig relation. The youngest galaxies in our sample show clear morphological signs of interaction. (Abridged)
New photometric and long-slit spectroscopic observations are presented for NGC 7113, PGC 1852, and PGC 67207 which are three bright galaxies residing in low-density environments. The surface-brightness distribution is analysed from the K_S-band image
We present the analysis of the HI content of a sample of early-type galaxies (ETGs) in low-density environments (LDEs) using the data set provided by the Arecibo Legacy Fast ALFA (ALFALFA) survey. We compare their properties to the sample in the Virg
We present an analysis of deep WSRT observations of the HI in 33 nearby early-type galaxies selected from a sample studied earlier at optical wavelengths with the SAURON integral-field spectrograph. The sample covers both field environments and the V
We explore the environmental dependence of star formation timescales in low mass galaxies using the [$alpha$/Fe] abundance ratio as an evolutionary clock. We present integrated [$alpha$/Fe] measurements for 11 low mass ($M_star sim 10^9~M_odot$) earl
We discuss the properties of the HI in low-luminosity early-type galaxies. The morphology of the HI is more regular than that of the HI in many more-luminous early-type galaxies. The HI is always distributed in a disk and is more centrally concentrat