We present absorption-line strengths on the Lick/IDS line-strength system of 381 galaxies and 38 globular clusters in the 4000-6400Å region. All galaxies were observed 1 Lick Observatory Bulletin #1375 2 Present address: Observatories of the Carnegie Institution of Washington, -2at Lick Observatory between 1972 and 1984 with the Cassegrain Image Dissector Scanner spectrograph, making this study one of the largest homogeneous collections of galaxy spectral line data to date. We also present a catalogue of nuclear velocity dispersions used to correct the absorption-line strengths onto the stellar Lick/IDS system. Extensive discussion of both random and systematic errors of the Lick/IDS system is provided. Indices are seen to fall into three families: α-element-like indices (including CN, Mg, Na D, and TiO 2 ) that correlate positively with velocity dispersion; Fe-like indices (including Ca, the G band, TiO 1 , and all Fe indices) that correlate only weakly with velocity dispersion and the α indices; and Hβ which anti-correlates with both velocity dispersion and the α indices. C 2 4668 seems to be intermediate between the α and Fe groups. These groupings probably represent different element abundance families with different nucleosynthesis histories.

No abstract

Aims. This is the second paper of a series devoted to the study of the stellar content of early-type galaxies. The goal of the series is to set constraints on the evolutionary status of these objects Methods. We use a new set of models that include an improved stellar library (MILES) to derive simple stellar population (SSP)-equivalent parameters in a sample of 98 early-type galaxies. The sample contains galaxies in the field, poor groups, and galaxies in the Virgo and Coma clusters. Results. We find that low-density environment galaxies span a larger range in SSP age and metallicity than their counterparts in high density environments, with a tendency for lower σ galaxies to be younger. Early-type galaxies in low-density environments appear on average ∼1.5 Gyr younger and more metal rich than their counterparts in high density environments. The sample of low-density environment galaxies shows an age-metallicity relation in which younger galaxies are found to be more metal rich, but only when metallicity is measured with a Fe-sensitive index. Conversely, there is no age-metallicity relation when the metallicity is measured with a Mg sensitive index. The mass-metallicity relation is only appreciable for the low-density environment galaxies when the metallicity is measured with a Mg-sensitive index, and not when the metallicity is measured with other indicators. On the contrary, this relation exists for the high-density environment galaxies independent of the indicator used to measure the metallicity.Conclusions. This suggests a dependence of the mass-metallicity relation on the environment of the galaxies. Our data favour a scenario in which galaxies in low density environments have suffered a more extended star formation history than the galaxies in the Coma cluster, which appear to host more homogenous stellar populations.

By means of the fossil record method implemented through Pipe3D, we reconstruct the global and radial stellar mass growth histories (MGHs) of an unprecedentedly large sample of galaxies, ranging from dwarf to giant objects, from the "Mapping Nearby Galaxies at the Apache Point Observatory" survey. We confirm that the main driver of the global MGHs is mass, with more massive galaxies assembling their masses earlier (downsizing), though for a given mass, the global MGHs segregate by color, specific star formation rate (sSFR), and morphological type. From the inferred radial mean MGHs, we find that at the late evolutionary stages (or for fractions of assembled mass larger than ∼ 80%), the innermost regions formed stars on average earlier than the outermost ones (inside-out). At earlier epochs, when the age resolution of the method becomes poor, the mass assembly seems to be spatially homogeneous or even in the outside-in mode, specially for the red/quiescent/early-type galaxies. The innermost MGHs are in general more regular (less scatter around the mean) than the outermost ones. For dwarf and low-mass galaxies, we do not find evidence of an outside-in formation mode; instead their radial MGHs are very diverse most of the time, with periods of outside-in and inside-out modes (or strong radial migration), suggesting this an episodic SF history. Blue/star-forming/late-type galaxies present on average a significantly more pronounced inside-out formation mode than red/quiescent/early-type galaxies, independently of mass. We discuss our results in the light of the processes of galaxy formation, quenching, and radial migration. We discus also on the uncertainties and biases of the fossil record method and how they could affect our results.

We present a detailed study of the stellar populations (SPs) and kinematics of the bulge and inner disc regions of eight nearby spiral galaxies (Sa–Sd) based on deep Gemini/GMOS data. The long‐slit spectra extend to 1–2 disc scalelengths with S/N/Å≥ 50. Several different model fitting techniques involving absorption‐line indices and full spectrum fitting are explored, and found to weigh age, metallicity and abundance ratios differently. We find that the SPs of spiral galaxies are not well matched by single episodes of star formation; more representative SPs must involve average SP values integrated over the star formation history (SFH) of the galaxy. Our ‘full population synthesis’ method is an optimized linear combination of model templates to the full spectrum with masking of regions poorly represented by the models. Realistic determinations of the SP parameters and kinematics (rotation and velocity dispersion) also rely on careful attention to data/model matching (resolution and flux calibration). The population fits reveal a wide range of age and metallicity gradients (from negative to positive) in the bulge, allowing for diverse formation mechanisms. The observed positive age gradients within the effective radius of some late‐type bulges helps reconcile the long‐standing conundrum of the coexistence of secular‐like kinematics, light profile shape and stellar bar with the ‘classical’‐like old and α‐enhanced SPs in the Milky Way bulge. The discs, on the other hand, almost always show mildly decreasing to flat profiles in both age and metallicity, consistent with inside‐out formation. Our spiral bulges follow the same correlations of increasing light‐weighted age and metallicity with central velocity dispersion as those of elliptical galaxies and early‐type bulges found in other studies, but when SFHs more complex and realistic than a single burst are invoked, the trend with age is shallower and the scatter much reduced. In a mass‐weighted context, however, all bulges are predominantly composed of old and metal‐rich SPs. While secular contributions to the evolution of many of our bulges are clearly evident, with young (0.001–1 Gyr) SPs contributing as much as 90 per cent of the optical (V‐band) light, the bulge mass fraction from young stars is small (≲25 per cent). The implies a bulge formation dominated by early processes that are common to all spheroids, whether they currently reside in discs or not. While monolithic collapse cannot be ruled out in some cases, merging must be invoked to explain the SP gradients in most bulges. Further bulge growth via secular processes or ‘rejuvenated’ star formation generally contributes minimally to the stellar mass budget, with the relative secular weight increasing with decreasing central velocity dispersion.