Article

# The Tully-Fisher relation for S0 galaxies

• ##### M. R. Merrifield
Monthly Notices of the Royal Astronomical Society (Impact Factor: 5.52). 09/2006; DOI: 10.1111/j.1365-2966.2006.11031.x
Source: arXiv

ABSTRACT We present a study of the local B and K-band Tully-Fisher Relation (TFR) between absolute magnitude and maximum circular speed in S0 galaxies. To make this study, we have combined kinematic data, including a new high-quality spectral data set from the Fornax Cluster, with homogeneous photometry from the RC3 and 2MASS catalogues, to construct the largest sample of S0 galaxies ever used in a study of the TFR. Independent of environment, S0 galaxies are found to lie systematically below the TFR for nearby spirals in both optical and infrared bands. This offset can be crudely interpreted as arising from the luminosity evolution of spiral galaxies that have faded since ceasing star formation. However, we also find a large scatter in the TFR. We show that most of this scatter is intrinsic, not due to the observational uncertainties. The presence of such a large scatter means that the population of S0 galaxies cannot have formed exclusively by the above simple fading mechanism after all transforming at a single epoch. To better understand the complexity of the transformation mechanism, we have searched for correlations between the offset from the TFR and other properties of the galaxies such as their structural properties, central velocity dispersions and ages (as estimated from line indices). For the Fornax Cluster data, the offset from the TFR relates with the estimated age of the stars in the individual galaxies, in the sense and of the magnitude expected if S0 galaxies had passively faded since being converted from spirals. This correlation implies that a significant part of the scatter in the TFR arises from the different times at which galaxies began their transformation. Comment: 17 pages, 11 figures, 3 tables, accepted for publication in MNRAS

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ABSTRACT: We present deep GMOS long-slit spectroscopy of 15 Coma cluster S0 galaxies, and extract kinematic properties along the major axis to several times the disc scale-length. Supplementing our dataset with previously published data, we create a combined sample of 29 Coma S0s, as well as a comparison sample of 38 Coma spirals. Using photometry from SDSS and 2MASS, we construct the Tully-Fisher relation (TFR; luminosity versus maximum rotational velocity) for S0 galaxies. At fixed rotational velocity, the Coma S0 galaxies are on average fainter than Coma spirals by 1.10$\pm$0.18, 0.86$\pm$0.19 and 0.83$\pm$0.19 mag in the g, i and Ks bands respectively. The typical S0 offsets remain unchanged when calculated relative to large field-galaxy spiral samples. The observed offsets are consistent with a simple star formation model in which S0s are identical to spirals until abrupt quenching occurs at some intermediate redshift. The offsets form a continuous distribution tracing the time since the cessation of star formation, and exhibit a strong correlation (>6{\sigma}) with residuals from the optical colour-magnitude relation. Typically, S0s which are fainter than average for their rotational velocity are also redder than average for their luminosity. The S0 TFR offset is also correlated with both the projected cluster-centric radius and the {\Sigma} (projected) local density parameter. Since current local environment is correlated with time of accretion into the cluster, our results support a scenario in which transformation of spirals to S0s is triggered by cluster infall.
Monthly Notices of the Royal Astronomical Society 05/2013; 433(3). · 5.52 Impact Factor
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##### Article: Caught in the act: Cluster k+a' galaxies as a link between spirals and S0s
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ABSTRACT: We use integral field spectroscopy of 13 disk galaxies in the cluster AC114 at z ~ 0.31 in an attempt to disentangle the physical processes responsible for the transformation of spiral galaxies in clusters. Our sample is selected to display a dominant young stellar population, as indicated by strong Hdelta absorption lines in their integrated spectra. Most of our galaxies lack the [OII] emission line, and hence ongoing star formation. They therefore possess k+a' spectra, indicative of a recent truncation of star formation, possibly preceded by a starburst. Disky `k+a' galaxies are a promising candidate for the intermediate stage of the transformation from star-forming spiral galaxies to passive S0s. Our observations allow us to study the spatial distributions and the kinematics of the different stellar populations within the galaxies. We used three different indicators to evaluate the presence of a young population: the equivalent width of Hdelta, the luminosity-weighted fraction of A stars, and the fraction of the galaxy light attributable to simple stellar populations with ages between 0.5 and 1.5 Gyr. We find a mixture of behaviours, but are able to show that in most of galaxies the last episode of star-formation occured in an extended disk, similar to preceeding generations of stars, though somewhat more centrally concentrated. We thus exclude nuclear starbursts and violent gravitational interactions as causes of the star formation truncation. Gentler mechanisms, such as ram-pressure stripping or weak galaxy-galaxy interactions, appear to be responsible for ending star-formation in these intermediate-redshift cluster disk galaxies.
Monthly Notices of the Royal Astronomical Society 11/2013; · 5.52 Impact Factor
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##### Article: Luminosity-dependent star formation history of S0 galaxies: evidence from GALEX-SDSS-2MASS-WISE colours
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ABSTRACT: We combine UV/optical/near-IR/mid-IR data on a sample of ˜240 S0 galaxies to examine various star formation related processes in them. We split the sample into bright and faint S0 galaxies based on their K-band luminosity. Comparing the far-ultraviolet (FUV)-near-ultraviolet (NUV) versus NUV-K colour-colour diagram with a simple stellar population model shows that ellipticals and bright S0 galaxies are dominated by a stellar population of age >109 yr while faint S0 galaxies may contain stars as young as 108 yr, providing evidence for relatively recent star formation activity. The strength of the 4000 Å break is also systematically higher in brighter S0 galaxies, again indicating the presence of an old stellar population. Their mid-IR colours indicate that bright S0 colours are like those of ellipticals while faint S0 colours are more like spirals. All these observations are consistent with a scenario in which low-luminosity S0 galaxies likely formed by the stripping of gas from the discs of late-type spiral galaxies, which in turn formed their pseudo-bulges through secular evolution processes, possibly involving multiple episodes of star formation. On the other hand, more luminous S0 galaxies likely formed the bulk of their stars at early epochs, similar to the star formation in elliptical galaxies, and are characterized by an old coeval stellar population and classical bulges.
Monthly Notices of the Royal Astronomical Society 06/2013; 432(1):430-437. · 5.52 Impact Factor