Search NASA⌕ Search

SEARCH · Search NASA

Results for “Stellar ages”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Radial velocity detection of extra-solar planetary systems

The goal of this program was to detect planetary systems in orbit around other stars through the ultra high precision measurement of the orbital motion of the star around the star-planet barycenter. The survey of 33 nearby solar-type stars is the essential first step in understanding the overall problem of planet formation. The program will accumulate the necessary statistics to determine the frequency of planet formation as a function of stellar mass, age, and composition.

Cochran, William D.↗
NASA NTRS2020

Cluster Difference Imaging Photometric Survey. II. TOI 837: A Young Validated Planet in IC 2602

We report the discovery of TOI 837b and its validation as a transiting planet. We characterize the system using data from the NASA Transiting Exoplanet Survey Satellite mission, the ESA Gaia mission, ground-based photometry from El Sauce and ASTEP400, and spectroscopy from CHIRON, FEROS, and Veloce. We find that TOI 837 is a T = 9.9 mag G0/F9 dwarf in the southern open cluster IC 2602. The star and planet are therefore 35(sup +11)(sub -5) million years old. Combining the transit photometry with a prior on the stellar parameters derived from the cluster color–magnitude diagram, we find that the planet has an orbital period of 8.3 days and is slightly smaller than Jupiter (R(sub p) = 0.77(sup + 0.09)(sub -0.07) R(sub Jup)). From radial velocity monitoring, we limit M(sub p) sin i to less than 1.20 M(sub Jup) (3σ). The transits either graze or nearly graze the stellar limb. Grazing transits are a cause for concern, as they are often indicative of astrophysical false-positive scenarios. Our follow-up data show that such scenarios are unlikely. Our combined multicolor photometry, high-resolution imaging, and radial velocities rule out hierarchical eclipsing binary scenarios. Background eclipsing binary scenarios, though limited by speckle imaging, remain a 0.2% possibility. TOI 837b is therefore a validated adolescent exoplanet. The planetary nature of the system can be confirmed or refuted through observations of the stellar obliquity and the planetary mass. Such observations may also improve our understanding of how the physical and orbital properties of exoplanets change in time.

Exoplanets↗
DOE OSTI2026

Beyond Point Estimates: Benchmarking Uncertainty Quantification Methods on the AION-1 Astronomical Foundation Model

Foundation models for astronomical surveys offer powerful learned representations that can be transferred to downstream regression tasks such as galaxy property estimation. However, point predictions alone are insufficient for scientific inference; reliable uncertainty quantification (UQ) is essential. We compare seven UQ methods on galaxy property regression using frozen AION-1 foundation-model embeddings, predicting redshift, stellar mass, stellar-population age, gas-phase metallicity, and specific star-formation rate, from Legacy Survey photometry/imaging and DESI spectra, with PROVABGS-derived labels. Distribution-free conformal methods achieve marginal coverage within $\sim$1 pp of the nominal 90% across all properties, while non-conformal baselines (Deep Ensembles, MC~Dropout) fail to calibrate reliably. Among conformal approaches, Conformalized Quantile Regression (CQR) delivers the best coverage in the bin with the poorest model predictions. More importantly, only the Locally Valid and Discriminative (LVD) framework -- particularly when operating on AION-1 embeddings -- also provides finite-sample \emph{local validity}, producing intervals that adapt to each galaxy's local prediction difficulty rather than relying on marginal guarantees alone. These results establish conformal prediction, and LVD in particular, as the preferred UQ framework for uncertainty-aware inference on foundation-model embeddings in astrophysics.

Tame-Narvaez, Karla [Fermilab] (ORCID:000000022249↗
NASA NTRS1991

Lithium in halo stars - Constraining the effects of helium diffusion on globular cluster ages and cosmology

Stellar evolutionary models with diffusion are used to show that observations of lithium in extreme halo stars provide crucial constraints on the magnitude of the effects of helium diffusion. The flatness of the observed Li-T(eff) relation severely constrains diffusion Li isochrones, which tend to curve downward toward higher T(eff). It is argued that Li observations at the hot edge of the plateau are particularly important in constraining the effects of helium diffusion; yet, they are currently few in number. It is proposed that additional observations are required there, as well as below 5500 K, to define more securely the morphology of the halo Li abundances. Implications for the primordial Li abundance are considered. It is suggested that a conservative upper limit to the initial Li abundance, due to diffusive effects alone, is 2.35.

Deliyannis, Constantine P.↗
NASA NTRS1994

X-ray sources in regions of star formation. 5: The low mass stars of the Upper Scorpius association

We report followup investigations of Einstein x-ray observations of the Upper Scorpius OB association. We identify 28 low mass pre-main sequence stars as counterparts of x-ray sources in the approximately = 7 square degrees of the OB association observed. Based on kinematics and lithium abundances, these stars are low mass members of the OB association. We use optical spectra and optical and near-IR photometry to determine the stellar luminosities, effective temperatures, masses, and ages. We show that the bolometric corrections and effective temperatures of the G and K stars are consistent with those of subgiants. The low mass stars have isochronal ages of 1-2 Myr, depending on the choice of evolutionary models, with very small dispersion (sigma approximately = 1 Myr). This age is significantly younger than the 5-6 Myr found for the more massive B stars. The small dispersion in stellar ages, less than 10% the sound-crossing time of the association, suggests that star formation was triggered. We present two scenarios for star formation in this association. In the two-episode scenario, formation of the low mass stars was triggered by a supernova explosion, and the low mass stars form quickly, with high efficiency. Alternatively, high and low mass star formation was all initiated at the same time, some 5-6 Myr ago, and the apparent systematic age difference is an artifact of how the isochrones are dated. The effect of the supernova is to terminate mass accretion and yield an apparently coeval population. We show that the incompleteness in the x-ray sampling is about 65%, and is strongly dependent on stellar mass. After correction for incompleteness, we estimate there are about 2000 low mass members (stellar mass less than 2 solar mass) of this association. The mass function in this association is indistinguishable from that of the field. The ratio of naked to classical T Tauri stars is much larger than in Tau-Aur, and may be attributable to the local environment. We also present observations of eight ROX sources associated with the rho Oph cloud, and observations of non-pre-main sequence (PMS) stars in our fields.

Walter, Frederick M.↗
DOE OSTI2022

Revisiting stellar properties of star-forming galaxies with stellar and nebular spectral modelling

Spectral synthesis is a powerful tool for interpreting the physical properties of galaxies by decomposing their spectral energy distributions (SEDs) into the main luminosity contributors (e.g. stellar populations of distinct age and metallicity or ionised gas). However, the impact nebular emission has on the inferred properties of star-forming (SF) galaxies has been largely overlooked over the years, with unknown ramifications to the current understanding of galaxy evolution. The objective of this work is to estimate the relations between stellar properties (e.g. total mass, mean age, and mean metallicity) of SF galaxies by simultaneously fitting the stellar and nebular continua and comparing them to the results derived through the more common purely stellar spectral synthesis approach. The main galaxy sample from SDSS DR7 was analysed with two distinct population synthesis codes: FADO, which estimates self-consistently both the stellar and nebular contributions to the SED, and the original version of STARLIGHT, as representative of purely stellar population synthesis codes. Differences between codes regarding average mass, mean age and mean metallicity values can go as high as ~0.06 dex for the overall population of galaxies and ~0.12 dex for SF galaxies (galaxies with EW(Hα) > 3 Å), with the most prominent difference between both codes in the two populations being in the light-weighted mean stellar age. FADO presents a broader range of mean stellar ages and metallicities for SF galaxies than STARLIGHT, with the latter code preferring metallicity solutions around the solar value (Z ⊙ = 0.02). A closer look into the average light- and mass-weighted star formation histories of intensively SF galaxies (EW(Hα) > 75 Å) reveals that the light contributions of simple stellar populations (SSPs) younger than ≤10 7 (10 9 ) years in STARLIGHT are higher by ~5.41% (9.11%) compared to FADO. Moreover, FADO presents higher light contributions from SSPs with metallicity ≤ Z ⊙ /200 (Z ⊙ /50) of around 8.05% (13.51%) when compared with STARLIGHT. This suggests that STARLIGHT is underestimating the average light-weighted age of intensively SF galaxies by up to ~0.17 dex and overestimating the light-weighted metallicity by up to ~0.13 dex compared to FADO (or vice versa). The comparison between the average stellar properties of passive, SF and intensively SF galaxy samples also reveals that differences between codes increase with increasing EW(Hα) and decreasing total stellar mass. Moreover, comparing SF results from FADO in a purely stellar mode with the previous results qualitatively suggests that differences between codes are primarily due to mathematical and statistical differences and secondarily due to the impact of the nebular continuum modelling approach (or lack thereof). However, it is challenging to adequately quantify the relative role of each factor since they are likely interconnected. This work finds indirect evidence that a purely stellar population synthesis approach negatively impacts the inferred stellar properties (e.g. mean age and mean metallicity) of galaxies with relatively high star formation rates (e.g. dwarf spirals, ‘green peas’, and starburst galaxies). In turn, this can bias interpretations of fundamental relations such as the mass-age or mass-metallicity, which are factors worth bearing in mind in light of future high-resolution spectroscopic surveys at higher redshifts (e.g. MOONS and 4MOST-4HS).

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Stellar Population Properties in the Stellar Streams around SPRC047

Abstract We have investigated the properties (e.g., age, metallicity) of the stellar populations of a ringlike tidal stellar stream (or streams) around the edge-on galaxy SPRC047 (z= 0.031) using spectral energy distribution (SED) fits to integrated broadband aperture flux densities. We used visual images in six different bands and Spitzer/IRAC 3.6μm data. We have attempted to derive best-fit stellar population parameters (metallicity, age) in three noncontiguous segments of the stream. Due to the very low surface brightness of the stream, we have performed a deconvolution with a Richardson–Lucy–type algorithm of the low spatial resolution 3.6μm IRAC image, thereby reducing the effect of the point-spread function aliasedemissionfrom the bright edge-on central galaxy at the locations of our three stream segments. Our SED fits that used several different star formation (SF) history priors, from an exponentially decaying SF burst to continuous SF, indicate that the age–metallicity–dust degeneracy is not resolved, most likely because of inadequate wavelength coverage and low signal-to-noise ratios of the low surface brightness features. We also discuss how future deep visual–near-infrared observations, combined with absolute flux calibration uncertainties at or below the 1% level, complemented by equally well absolute flux-calibrated observations in ultraviolet and mid-infrared bands, would improve the accuracy of broadband SED fitting results for low surface brightness targets, such as stellar streams around nearby galaxies that are not resolved into stars.

Astronomy & Astrophysics↗
NASA NTRS1979

Stellar evolution from the zero-age main sequence

A consistent set of 247 evolutionary sequences extending from the ZAMS to the red-giant branch is presented for Y from 0.10 to 0.40, Z from 0.00001 to 0.10, and masses of 0.55 to 6.90 solar masses. Each sequence is started from a homogeneous ZAMS model, and almost all are evolved to the base of the red-giant branch. It is shown that: (1) the relative position of the main sequence can be determined as a function of composition; (2) theoretical luminosity functions can be derived from the relative evolutionary time scales; (3) a dip in luminosity sometimes occurs at the base of the red-giant branch and is most pronounced at larger Z values; (4) metal-poor stars evolve farther up along the main sequence before turning off toward the red-giant branch; and (5) the onset of helium burning halts the evolution across the Hertzsprung gap for the most massive and most metal-poor models, so that the star remains blue during its phase of core-helium burning.

Mengel, J. G.↗
NASA NTRS2013

Quiescent Galaxies in the 3D-HST Survey: Spectroscopic Confirmation of a Large Number of Galaxies With Relatively Old Stellar Populations at z Approx. 2

Quiescent galaxies at z approx. 2 have been identified in large numbers based on rest-frame colors, but only a small number of these galaxies have been spectroscopically confirmed to show that their rest-frame optical spectra show either strong Balmer or metal absorption lines. Here, we median stack the rest-frame optical spectra for 171 photometrically quiescent galaxies at 1.4 < z < 2.2 from the 3D-HST grism survey. In addition to H (4861 ),we unambiguously identify metal absorption lines in the stacked spectrum, including the G band (4304 ),Mgi (5175 ), and Na i (5894 ). This finding demonstrates that galaxies with relatively old stellar populations already existed when the universe was approx. 3 Gyr old, and that rest-frame color selection techniques can efficiently select them. We find an average age of 1.3+0.10.3 Gyr when fitting a simple stellar population to the entire stack. We confirm our previous result from medium-band photometry that the stellar age varies with the colors of quiescent galaxies: the reddest 80 of galaxies are dominated by metal lines and have a relatively old mean age of 1.6+0.50.4 Gyr, whereas the bluest (and brightest) galaxies have strong Balmer lines and a spectroscopic age of 0.9+0.20.1 Gyr. Although the spectrum is dominated by an evolved stellar population, we also find [O iii] and H emission. Interestingly, this emission is more centrally concentrated than the continuum with LOiii = 1.7+/- 0.3 x 10(exp 40) erg/s, indicating residual central star formation or nuclear activity.

Quiescent↗
NASA NTRS2022

Is [Y/Mg] a Reliable Age Diagnostic for FGK Stars?

Current spectroscopic surveys are producing large catalogs of chemical abundances for stars of all types. The yttrium-to-magnesium ratio, [Y/Mg], has emerged as a candidate age indicator for solar twins in the local stellar neighborhood. However, it is unclear whether it is a viable age diagnostic for more diverse stellar types, so we investigate [Y/Mg] as an age indicator for the FGK-type planet host stars observed by Kepler. We find that the [Y/Mg] "Clock" is most precise for solar twins, with a [Y/Mg]/age slope of m = −0.0370 ±0.0071 dex Gyr −1 and σ Age = 2.6 Gyr. We attribute the lower precision compared to literature results to nonsolar twins contaminating our solar twin sample and recommend a 1.5 Gyr systematic uncertainty for stellar ages derived with any [Y/Mg]–Age relation. We also analyzed the [Y/Mg] Clock as a function of T eff , log⁡ g, and metallicity individually and find no strong trends, but we compute statistically significant [Y/Mg]–Age relations for subsamples defined by ranges in T eff , log g, and metallicity. Finally, we compare [Y/Mg] and rotation ages and find statistically similar trends as for isochrone ages, although we find that rotation ages perform better for GK dwarfs while isochrones perform better for FG subgiants. We conclude that the [Y/Mg] Clock is most precise for solar twins and analogs but is also a useful age diagnostic for FGK stars.

Travis A. Berger↗
DOE OSTI2023

The Chemodynamics of the Stellar Populations in M31 from APOGEE Integrated-light Spectroscopy

We present an analysis of nearly 1000 near-infrared, integrated-light spectra from APOGEE in the inner ~7 kpc of M31. We utilize full-spectrum fitting with A-LIST simple stellar population spectral templates that represent a population of stars with the same age, [M/H], and [α/M]. With this, we determine the mean kinematics, metallicities, α abundances, and ages of the stellar populations of M31's bar, bulge, and inner disk (~4–7 kpc). We find a nonaxisymmetric velocity field in M31 resulting from the presence of a bar. The bulge of M31 is less metal-rich (mean [M/H] = $0.149$$^{+0.067}_{-0.081}$ dex) than the disk, features minima in metallicity on either side of the bar ([M/H] ~ -0.2), and is enhanced in α abundance (mean [α/M] = $0.281$$^{+0.035}_{-0.038}$). The disk of M31 within ~7 kpc is enhanced in both metallicity ([M/H] = $-0.023$$^{+0.050}_{-0.052}$) and α abundance ([α/M] = $0.274$$^{+0.020}_{-0.025}$). Both of these structural components are uniformly old at ≃12 Gyr. We find the mean metallicity increases with distance from the center of M31, with the steepest gradient along the disk major axis (0.043 ± 0.021 dex kpc -1 ). This gradient is the result of changing light contributions from the bulge and disk. The chemodynamics of stellar populations encodes information about a galaxy's chemical enrichment, star formation history, and merger history, allowing us to discuss new constraints on M31's formation. Our results provide a stepping stone between our understanding of the Milky Way and other external galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2013

Quiescent Galaxies in the 3D-HST Survey: Spectroscopic Confirmation of a Large Number of Galaxies with Relatively Old Stellar Populations at Z approx. 2

Quiescent galaxies at zeta approximately 2 have been identified in large numbers based on rest-frame colors, but only a small number of these galaxies have been spectroscopically confirmed to show that their rest-frame optical spectra show either strong Balmer or metal absorption lines. Here, we median stack the rest-frame optical spectra for 171 photometrically quiescent galaxies at 1.4 less than z less than 2.2 from the 3D-HST grism survey. In addition to H(Beta) (lambda 4861 Angstroms), we unambiguously identify metal absorption lines in the stacked spectrum, including the G band (lambda 4304 Angstroms), Mg I (lambda 5175 Angstroms), and Na i (lambda 5894 Angstroms). This finding demonstrates that galaxies with relatively old stellar populations already existed when the universe was approximately 3 Gyr old, and that rest-frame color selection techniques can efficiently select them. We find an average age of 1.3(+0.1/−0.3) Gyr when fitting a simple stellar population to the entire stack. We confirm our previous result from medium-band photometry that the stellar age varies with the colors of quiescent galaxies: the reddest 80% of galaxies are dominated by metal lines and have a relatively old mean age of 1.6(+0.5/−0.4) Gyr, whereas the bluest (and brightest) galaxies have strong Balmer lines and a spectroscopic age of 0.9(+0.2/−0.1) Gyr. Although the spectrum is dominated by an evolved stellar population, we also find [O III] and Hβ emission. Interestingly, this emission is more centrally concentrated than the continuum with L(sub OIII) = 1.7 +/- 0.3 × 10(exp 40 erg s−1, indicating residual central star formation or nuclear activity.

Quiescent↗
NASA NTRS1995

Sensitivity of solar g-modes to varying G cosmologies

The sensitivity of the solar g-mode oscillation spectrum to variability in the universal gravitational constant G is described. Solar models in varying G cosmologies were constructed by evolving a zero-age main-sequence stellar model to the Sun's current age, while allowing the value of G to change according to the power law G(t) proportional to t(exp -beta), where Beta approximately equals delta G/GH and H is the Hubble constant. All solar models were constrained to the observed luminosity and radius at the current age of the Sun by adjusting the helium abundance and the mixing-length parameter of the models in the usual way for standard stellar models. Low-l g-mode oscillation periods were calculated for each of the models and compared to the claimed observation of the solar g-mode oscillation spectrum by Hill & Gu (1990). If one accepts Hill & Gu's claims, then within the uncertainties of the physics of the solar model calculation, our models rule out all but (delta G/GH) less than approximately 0.05. In other words, we conclude that G could not have varied by more than 2% over the past 4.5 Gyr, the lifetime of the present-day Sun. This result lends independent support to the validity of the standard solar model.

Guenther, D. B.↗
NASA NTRS1993

Indications for common origin and gravitational interaction in three binary LMC clusters

Three close pair clusters of the LMC, NGC 2006/SL 538, NGC 2011 a/b, and NGC 2042 a/b, have been studied in order to establish their binarity. The stellar content in the outer region of each cluster has been investigated by means of low resolution objective UK Schmidt prism spectra, the cores of the clusters have been examined using low resolution integrated IUE spectra, whereas their density profiles and their observed dynamical parameters have been derived by means of star counts. The integrated spectra of their cores and the stellar content of their outer cluster regions have shown a common origin and a very young age (less than 2 x 10 exp 7 yr) for each member of the pairs, whereas their dynamical study has shown that they are gravitationally interacting. Comparing the age of their stellar content with their dynamical and relaxation times, it has been found that these clusters are physically associated and had no time to relax by stellar encounters, no time to merge, and no time to be destroyed by dynamical friction.

Kontizas, E.↗
NASA NTRS1993

Ages, chemistry, and type 1A supernovae: Clues to the formation of the galactic stellar halo

We endeavor to resolve two conflicting constraints on the duration of the formation of the Galactic stellar halo - 2-3 Gyr age differences in halo stars, and the time scale inferred from the observed constant values of chemical element abundance ratios characteristic of enrichment by Type II supernovae - by investigating the time scale for the onset of Type Ia supernovae (SNIa) in the currently favored progenitor model - mergers of carbon and oxygen white dwarfs (CO WDs).

Smecker-Hane, Tammy A.↗
NASA NTRS2011

Stellar Populations of Highly Magnified Lensed Galaxies Young Starburst at Z to Approximately 2

We present a comprehensive analysis of the rest-frame UV to near-IR spectral energy distributions and rest-frame optical spectra of four of the brightest gravitationally lensed galaxies in the literature: RCSGA 032727-132609 at z = 170, MS1512-cB58 at z = 2.73, SGAS J152745.1+065219 at z = 2.76 and SGAS J12265L3+215220 at z = 2.92. This includes new Spitzer imaging for RCSGA0327 as well as new spectra, near-IR imaging and Spitzer imaging for SGAS1527 and SGAS1226. Lensing magnifications of 3-4 magnitudes allow a detailed study of the stellar populations and physical conditions. We compare star formation rates as measured from the SED fit, the Ha and [O II] .(lambda)3727 emission lines, and the UV+IR bolometric luminosity where 24micron photometry is available. The SFR estimate from the SED fit is consistently higher than the other indicators, which suggests that the Calzetti dust extinction law used in the SED fitting is too flat for young star-forming galaxies at z approx. 2. Our analysis finds similar stellar population parameters for all four lensed galaxies: stellar masses 3 - 7 x 10(exp 9) Stellar mass, young ages approx. 100 Myr, little dust content E(B - V)=0.10-0.25, and star formation rates around 20- 100 Stellar mass/y. Compared to typical values for the galaxy population at z approx. 2, this suggests we are looking at newly formed, starbursting systems that have only recently started the build-up of stellar mass. These results constitute the first detailed, uniform analysis of a sample of the growing number of strongly lensed galaxies known at z approx. 2. Subject headings: galaxies: high-redshift, strong gravitational lensing, infrared: galaxies

Wuyts, Eva↗
NASA NTRS1991

On the utility of low resolution IUE spectroscopy of the 2800 A Mg II lines as a stellar chromosphere indicator

Low resolution IUE spectroscopy of the 2800-A Mg II h and k lines is shown to provide a useful means for documenting chromospheric activity among relatively young dwarf stars. An index I(Mg II) has been defined which measures the integrated flux in the region 2784-2814 A relative to the flux interpolated from nearby comparison regions. Values of this index have been derived from low resolution IUE spectra for a sample of field dwarfs for which Ca II H and K line indices have been published as part of the Mount Wilson HK program. The large range in chromospheric activity among field dwarfs that is exhibited by the Mount Wilson Ca II S index is found to also be reflected by the lower resolution I(Mg II) index. Using an age calibration of Ca II emission line strengths derived by Barry, it is found that the value of I(Mg II) can be used to distinguish between dwarfs younger and older than 3 Gyr. The low resolution nature of the I(Mg II) index means that it holds potential for use as an age diagnostic for stellar population studies. Among dwarfs of age greater than 3 Gyr there is some evidence that this Mg II index is affected by line blanketing.

Smith, Graeme H.↗
DOE OSTI2020

Galaxy properties as revealed by MaNGA – III. Kinematic profiles and stellar population gradients in S0s

ABSTRACT This is the third paper of a series where we study the stellar population gradients (SP; ages, metallicities, α-element abundance ratios, and stellar initial mass functions) of early-type galaxies (ETGs) at $z$ ≤ 0.08 from the Mapping Nearby Galaxies at APO Data Release 15 (MaNGA-DR15) survey. In this work, we focus on the S0 population and quantify how the SP varies across the population as well as with galactocentric distance. We do this by measuring Lick indices and comparing them to SP synthesis models. This requires spectra with high signal-to-noise ratio which we achieve by stacking in bins of luminosity (Lr) and central velocity dispersion (σ0). We find that: (1) there is a bimodality in the S0 population: S0s more massive than $3\times 10^{10}\, \mathrm{M}_\odot$ show stronger velocity dispersion and age gradients (age and σr decrease outwards) but little or no metallicity gradient, while the less massive ones present relatively flat age and velocity dispersion profiles, but a significant metallicity gradient (i.e. [M/H] decreases outwards). Above $2\times 10^{11}\, \mathrm{M}_\odot$, the number of S0s drops sharply. These two mass scales are also where global scaling relations of ETGs change slope. (2) S0s have steeper velocity dispersion profiles than fast-rotating elliptical galaxies (E-FRs) of the same luminosity and velocity dispersion. The kinematic profiles and SP gradients of E-FRs are both more similar to those of slow-rotating ellipticals (E-SRs) than to S0s, suggesting that E-FRs are not simply S0s viewed face-on. (3) At fixed σ0, more luminous S0s and E-FRs are younger, more metal rich and less α-enhanced. Evidently for these galaxies, the usual statement that ‘massive galaxies are older’ is not true if σ0 is held fixed.

Domínguez Sánchez, H.↗