arXiv subjects

Glenn van de Ven

Publications and source records attributed to Glenn van de Ven.

At least 199 records · Page 11Linked to original sources

arXiv2012

An Over-Massive Black Hole in the Compact Lenticular Galaxy NGC1277

All massive galaxies likely have supermassive black holes at their centers, and the masses of the black holes are known to correlate with properties of the host galaxy bulge component. Several explanations have been proposed for the existence of these locally-established empirical relationships; they include the non-causal, statistical process of galaxy-galaxy merging, direct feedback between the black hole and its host galaxy, or galaxy-galaxy merging and the subsequent violent relaxation and dissipation. The empirical scaling relations are thus important for distinguishing between various theoretical models of galaxy evolution, and they further form the basis for all black hole mass measurements at large distances. In particular, observations have shown that the mass of the black hole is typically 0.1% of the stellar bulge mass of the galaxy. The small galaxy NGC4486B currently has the largest published fraction of its mass in a black hole at 11%. Here we report observations of the stellar kinematics of NGC 1277, which is a compact, disky galaxy with a mass of 1.2 x 10^11 Msun. From the data, we determine that the mass of the central black hole is 1.7 x 10^10 Msun, or 59% its bulge mass. Five other compact galaxies have properties similar to NGC 1277 and therefore may also contain over-sized black holes. It is not yet known if these galaxies represent a tail of a distribution, or if disk-dominated galaxies fail to follow the normal black hole mass scaling relations.

astro-ph.CO↗

arXiv2012

A census of orbital properties of the M31 satellites

We present an analysis of the dynamics of the M31 satellite system. Proper motion data exist for only two of the M31 satellites. We account for this incompleteness in velocity data by a statistical analysis using a combination of the timing argument and phase-space distribution functions. The bulk of the M31 satellites are well fit by these models and we offer a table of orbital properties, including period, eccentricity and semi-major axis. This enables us to search for evidence of group infall based on orbital similarity rather than propinquity on the sky. Our results favour an association between Cass II and NGC 185, as the orbital parameters are in close agreement, but not for NGC 185 and NGC 147, which have often been associated in the past. Other possible satellite groupings include the pair And I and And XVII; the pair And IX and And X; and the triple And V, And XXV and NGC 147. And XXII has been claimed as a satellite of M33; we find that they are not moving independently along the same orbit, but cannot determine whether they are orbiting each other or are unrelated. Two satellites, And XII and And XIV, have high line-of-sight velocities, consistent with very recent infall from the edge of the Local Group. They are not well described by our underlying smooth phase space distribution function, and are reanalysed without priors on their orbital parameters. For And XIV, multiple pericentric passages are possible and improved distance information is needed to draw further conclusions. For And XII, orbits which assume at least one pericentric passage can be ruled out and it must be on its first infall into the M31 system.

astro-ph.CO↗

arXiv2012

Virgo Cluster and field dwarf ellipticals in 3D: I. On the variety of stellar kinematic and line-strength properties

We present the first large-scale stellar kinematic and line-strength maps for dwarf elliptical galaxies (9 in the Virgo Cluster and 3 in the field environment) obtained with the SAURON integral-field unit. No two galaxies in our sample are alike: we see that the level of rotation is not tied to flattening (we have, e.g. round rotators and flattened nonrotators); we observe kinematic twists in 1 Virgo and 1 field object; we discover large-scale kinematically-decoupled components in 2 field galaxies; we see varying gradients in line-strength maps, from nearly flat to strongly peaked in the center. The great variety of morphological, kinematic, and stellar population parameters seen in our data points to a formation scenario in which properties are shaped stochastically. A combined effect of ram-pressure stripping and galaxy harassment is the most probable explanation. We show the need for a comprehensive analysis of kinematic, dynamical, and stellar population properties which will enable us to place dwarf ellipticals and processes that govern their evolution in the wider context of galaxy formation.

astro-ph.CO↗

arXiv2012

3D view on Virgo and field dwarf elliptical galaxies: late-type origin and environmental transformations

We show the effects of environmental evolution on Virgo cluster and field dwarf elliptical galaxies (dEs), presenting the first large-scale integral-field spectroscopic data for this galaxy class. The great variety of morphological, kinematic, and stellar population parameters seen in our data supports the claim that dEs are defunct dwarf spiral/irregular galaxies and points to a formation scenario that allows for a stochastic shaping of galaxy properties. We further investigate the properties of our sample by analyzing its kinematic and dynamical properties. We compare the level of rotational support of dEs and giant early-type galaxies and show that the properties of the former largely resemble those of giant fast-rotators. Based on our data, no trend exists between the level of rotational support in dEs and their location in the cluster. However, a tentative trend is seen in dark matter fraction: it increases for larger Virgocentric distances.

astro-ph.CO↗

arXiv2012

A resonant feature near the Perseus arm revealed by red clump stars

We investigate the extinction together with the radial velocity dispersion and distribution of red clump stars in the anti-center direction using spectra obtained with Hectospec on the MMT. We find that extinction peaks at Galactocentric radii of about 9.5 and 12.5 kpc, right in front of the locations of the Perseus and Outer arms and in line with the relative position of dust and stars in external spiral galaxies. The radial velocity dispersion peaks around 10kpc, which coincides with the location of the Perseus arm, yields an estimated arm-interarm density contrast of 1.3-1.5 and is in agreement with previous studies. Finally, we discover that the radial velocity distribution bifurcates around 10-11 kpc into two peaks at +27 km/s and -4 km/s. This seems to be naturally explained by the presence of the outer Lindblad resonance of the Galactic bar, but further observations will be needed to understand if the corotation resonance of the spirals arms also plays a role.

astro-ph.GA↗

arXiv2012

The SAURON project-XXI. The spatially-resolved UV-line strength relations of early-type galaxies

The unexpected rising flux of early-type galaxies at decreasing ultraviolet (UV) wavelengths is a long-standing mystery. One important observational constraint is the correlation between UV-optical colours and Mg2 line strengths found by Burstein et al. (1988). The simplest interpretation of this phenomenon is that the UV strength is related to the Mg line strength. Under this assumption, we expect galaxies with larger Mg gradients to have larger UV colour gradients. By combining UV imaging from GALEX, optical imaging from MDM and SAURON integral-field spectroscopy, we investigate the spatially-resolved relationships between UV colours and stellar population properties of 34 early-type galaxies from the SAURON survey sample. We find that galaxies with old stellar populations show tight correlations between the FUV colours (FUV-V and FUV-NUV) and the Mgb index, Hβ index and metallicity [Z/H]. The equivalent correlations for the Fe5015 index, α-enhancement [α/Fe] and age are present but weaker. We have also derived logarithmic internal radial colour, measured line strength and derived stellar population gradients for each galaxy and again found a strong dependence of the FUV-V and FUV-NUV colour gradients on both the Mg b line strength and the metallicity gradients for galaxies with old stellar populations. In particular, global gradients of Mg b and [Z/H] with respect to the UV colour across galaxies are consistent with their local gradients within galaxies, suggesting that the global correlations also hold locally. From a simple model based on multi-band colour fits of UV upturn and UV-weak galaxies, we have identified a plausible range of parameters that reproduces the observed radial colour profiles. In these models, the centers of elliptical galaxies, where the UV flux is strong, are enhanced in metals by roughly 60% compared to UV-weak regions.

astro-ph.CO↗

arXiv2012

Chemo-orbital evidence from SDSS/SEGUE G-type dwarf stars for a mixed origin of the Milky Way's thick disk

We combine the estimated metallicities [Fe/H], abundances [α/Fe], positions and motions of a sample of 27,500 local (7<R/kpc<9, 0.5<|z|/kpc<2.5) SDSS/SEGUE G-type dwarf stars to investigate the chemo-orbital properties of the Milky Way's disk around the Sun. When we derive the orbital properties reflecting angular momentum, circularity, and thickness as function of [α/Fe] vs. [Fe/H], we find that there is a smooth variation with [α/Fe], a proxy for age. At the same time, the orbital properties of the old stars with [α/Fe]$\gtrsim$0.25 do show a transition with [Fe/H]: below [Fe/H]$\simeq$-0.6 the orbital angular momentum decreases, and the orbits become significantly non-circular and thicker. Radial migration of stars into the Solar neighborhood would naturally result in a smooth variation in the orbital properties, but the latter old metal-poor stars form a clear challenge, in particular because a basic feature of radial migration is that stars remain on near-circular orbits. When we next select stars on near-circular orbits, we indeed find besides the α-young 'thin-disk' stars a significant contribution to the α-old 'thick-disk' metal-rich stars. However, the remaining α-old 'thick-disk' stars on eccentric orbits, including nearly all old metal-poor stars, are difficult to explain with radial migration alone, but might have formed through early-on gas-rich mergers. We thus find chemo-orbital evidence that the thicker component of the Milky Way disk is not distinct from the thin component as expected from smooth internal evolution through radial migration, except for the old metal-poor stars with different orbital properties which could be part of a distinct thick-disk component formed through an external mechanism.

astro-ph.GA↗

arXiv2011

The central dark matter distribution of NGC 2976

We study the mass distribution in the late-type dwarf galaxy NGC 2976 through stellar kinematics obtained with the VIRUS-P integral-field spectrograph and anisotropic Jeans models as a test of cosmological simulations and baryonic processes that putatively alter small-scale structure. Previous measurements of the H-alpha emission-line kinematics have determined that the dark matter halo of NGC 2976 is most consistent with a cored density profile. We find that the stellar kinematics are best fit with a cuspy halo. Cored dark matter halo fits are only consistent with the stellar kinematics if the stellar mass-to-light ratio is significantly larger than that derived from stellar population synthesis, while the best-fitting cuspy model has no such conflict. The inferred mass distribution from a harmonic decomposition of the gaseous kinematics is inconsistent with that of the stellar kinematics. This difference is likely due to the gas disk not meeting the assumptions that underlie the analysis such as no pressure support, a constant kinematic axis, and planar orbits. By relaxing some of these assumptions, in particular the form of the kinematic axis with radius, the gas-derived solution can be made consistent with the stellar kinematic models. A strong kinematic twist in the gas of NGC 2976's center suggests caution, and we advance the mass model based on the stellar kinematics as more reliable. The analysis of this first galaxy shows promising evidence that dark matter halos in late-type dwarfs may in fact be more consistent with cuspy dark matter distributions than earlier work has claimed.

astro-ph.CO↗

arXiv2011

The SAURON Project - XX. The Spitzer [3.6] - [4.5] colour in early-type galaxies: colours, colour gradients and inverted scaling relations

We investigate the [3.6] - [4.5] Spitzer-IRAC colour behaviour of the early-type galaxies of the SAURON survey, a representative sample of 48 nearby ellipticals and lenticulars. We investigate how this colour, which is unaffected by dust extinction, can be used to constrain the stellar populations in these galaxies. We find a tight relation between the [3.6]-[4.5] colour and effective velocity dispersion, a good mass-indicator in early-type galaxies. Contrary to other colours in the optical and near-infrared, we find that the colours become bluer for larger galaxies. The relations are tighter when using the colour inside r_e, rather than the much smaller r_e/8 aperture, due to the presence of young populations in the central regions. We also obtain strong correlations between the [3.6]-[4.5] colour and 3 strong absorption lines (H beta, Mg b and Fe 5015). Comparing our data with the models of Marigo et al., which show that more metal rich galaxies are bluer, we can explain our results in a way consistent with results from the optical, by stating that larger galaxies are more metal rich. The blueing is caused by a strong CO absorption band, whose line strength increases strongly with decreasing temperature and which covers a considerable fraction of the 4.5 micron filter. In galaxies that contain a compact radio source, the [3.6]-[4.5] colour is generally slightly redder than in the other galaxies, indicating small amounts of either hot dust, non-thermal emission, or young stars near the center. We find that the large majority of the galaxies show redder colours with increasing radius. abbreviated...

astro-ph.CO↗

arXiv2011

Grigori Kuzmin and Stellar Dynamics

Grigori Kuzmin was a very gifted dynamicist and one of the towering figures in the distinguished history of the Tartu Observatory. He obtained a number of important results in relative isolation which were later rediscovered in the West. This work laid the foundation for further advances in the theory of stellar systems in dynamical equilibrium, thereby substantially increasing our understanding of galaxy dynamics.

astro-ph.CO↗

arXiv2011

Resolving the dynamical mass of a z~1.3 QSO host galaxy using SINFONI and Laser Guide Star assisted Adaptive Optics

Recent studies of the tight scaling relations between the masses of supermassive black holes and their host galaxies have suggested that in the past black holes constituted a larger fraction of their host galaxies' mass. However, these arguments are limited by selection effects and difficulties in determining robust host galaxy masses at high redshifts. Here we report the first results of a new, complementary diagnostic route: we directly determine a dynamical host galaxy mass for the z=1.3 luminous quasar J090543.56+043347.3 through high-spatial-resolution (0.47", 4kpc FWHM) observations of the host galaxy gas kinematics over 30x40 kpc using ESO/VLT/SINFONI with LGS/AO. Combining our result of M_dyn = 2.05+1.68_0.74 x 10^11 M_sun (within a radius 5.25 +- 1.05 kpc) with M_BH,MgII = 9.02 \pm 1.43 x 10^8 M_sun, M_BH,Halpha = 2.83 +1.93-1.13 x 10^8 M_sun, we find that the ratio of black hole mass to host galaxy dynamical mass for J090543.56+043347.3 matches the present-day relation for M_BH vs. M_Bulge,Dyn, well within the IR scatter, deviating at most a factor of two from the mean. J090543.56+043347.3 displays clear signs of an ongoing tidal interaction and of spatially extended star formation at a rate of 50-100 M_sun/yr, above the cosmic average for a galaxy of this mass and redshift. We argue that its subsequent evolution may move J090543.56+043347.3 even closer to the z=0 relation for M_BH vs. M_Bulge,Dyn. Our results support the picture where any substantive evolution in these relations must occur prior to z~1.3. Having demonstrated the power of this modelling approach we are currently analyzing similar data on seven further objects to better constrain such evolution.

astro-ph.CO↗

arXiv2011

The ATLAS3D project - III. A census of the stellar angular momentum within the effective radius of early-type galaxies: unveiling the distribution of Fast and Slow Rotators

We provide a census of the apparent stellar angular momentum within 1 Re of a volume-limited sample of 260 early-type galaxies (ETGs) in the nearby Universe, using integral-field spectroscopy obtained in the course of the ATLAS3D project. We exploit the LambdaR parameter to characterise the existence of two families of ETGs: Slow Rotators which exhibit complex stellar velocity fields and often include stellar kinematically Distinct Cores (KDCs), and Fast Rotators which have regular velocity fields. Our complete sample of 260 ETGs leads to a new criterion to disentangle Fast and Slow Rotators which now includes a dependency on the apparent ellipticity (Epsilon). It separates the two classes significantly better than the previous prescription, and than a criterion based on V/Sigma: Slow Rotators and Fast Rotators have LambdaR lower and larger than kFSxSQRT(Epsilon), respectively, where kFS=0.31 for measurements made within 1 Re. We show that the vast majority of early-type galaxies are Fast Rotators: these have regular stellar rotation, with aligned photometric and kinematic axes (Paper II, Krajnovic et al. 2011}, include discs and often bars and represent 86% (224/260) of all early-type galaxies in the volume-limited ATLAS3D sample. Fast Rotators span the full range of apparent ellipticities from 0 to 0.85, and we suggest that they cover intrinsic ellipticities from about 0.35 to 0.85, the most flattened having morphologies consistent with spiral galaxies. Only a small fraction of ETGs are Slow Rotators representing 14% (36/260) of the ATLAS3D sample of ETGs. Of all Slow Rotators, 11% (4/36) exhibit two counter-rotating stellar disc-like components and are rather low mass objects (Mdyn<10^10.5 M_Sun). All other Slow Rotators (32/36) appear relatively round on the sky (Epsilon_e<0.4), tend to be massive (Mdyn>10^10.5 M_Sun), and often (17/32) exhibit KDCs.

astro-ph.CO↗

arXiv2011

The SAURON project - XVIII. The integrated UV-linestrength relations of early-type galaxies

Using far (FUV) and near (NUV) ultraviolet photometry from guest investigator programmes on the Galaxy Evolution Explorer (GALEX) satellite, optical photometry from the MDM Observatory and optical integral-field spectroscopy from SAURON, we explore the UV-linestrength relations of the 48 nearby early-type galaxies in the SAURON sample. Identical apertures are used for all quantities, avoiding aperture mismatch. We show that galaxies with purely old stellar populations show well-defined correlations of the integrated FUV-V and FUV-NUV colours with the integrated Mgb and Hbeta absorption linestrength indices, strongest for FUV-NUV. Correlations with the NUV-V colour, Fe5015 index and stellar velocity dispersion are much weaker. These correlations put stringent constraints on the origin of the UV-upturn phenomenon in early-type galaxies, and highlight its dependence on age and metallicity. In particular, despite recent debate, we recover the negative correlation between FUV-V colour and Mg linestrength originally publicised by Burstein et al. (1988), which we refer to as the "Burstein relation", suggesting a positive dependence of the UV-upturn on metallicity. We argue that the scatter in the correlations is real, and present mild evidence that a strong UV excess is preferentially present in slow-rotating galaxies. We also demonstrate that most outliers in the correlations are galaxies with current or recent star formation, some at very low levels. We believe that this sensitivity to weak star formation, afforded by the deep and varied data available for the SAURON sample, explains why our results are occasionally at odds with other recent but shallower surveys. This is supported by the analysis of a large, carefully-crafted sample of more distant early-type galaxies from the Sloan Digital Sky Survey (SDSS), more easily comparable with current and future large surveys.

astro-ph.CO↗

arXiv2011

Physical Condition of Molecular Gas at the Centre of NGC 1097

We have used the Xco conversion factor, Local Thermal Equilibrium and Large Velocity Gradient approximation to parametrize the cold and warm phase of the interstellar medium from five different low transitions of CO in the central 21"(kpc) of NGC 1097. We have applied a one-component model and derived a typical kinetic temperature of ~33K, and its molecular Hydrogen density and a CO column density. A two-component model results in 85% cold-to-total gas fraction with a 90K warm counterpart. Furthermore, we "resolve" the spatially unresolved single dish observations by selecting velocity channels that in an interferometric velocity map correspond to specific regions. We have selected five such regions and found that the physical properties in these regions are comparable to those derived from the full line profile. This implies that the central kpc of NGC 1097 is rather homogeneous in nature, and, although the regions are not uniquely located within the ring, the star formation along the ring is homogeneously distributed (in agreement with recent Herschel observations). We have further revised the mass inflow rate onto the Supermassive Black Hole in this prototype LINER/Sy1 galaxy and found that, accounting for the total interstellar medium and applying a careful contribution of the disc thickness and corresponding stability criterion, increases the previous estimations by a factor 10. Finally we have calculated the Xco for the centre of NGC 1097 using an independent estimation of the surface density to the CO emission, and obtained Xco=(2.8+-0.5)x10^20 cm^-2(K km s^-1)^-1 at radius 10.5" and Xco=(5.0+-0.5)x10^20 cm^-2(K km s^-1)^-1 at 7.5". With the approach and analysis described, we have demonstrated that important physical properties can be derived to a resolution beyond the single dish resolution element, however, caution is necessary for interpreting the results.(Abriged)

astro-ph.CO↗

arXiv2010

The Einstein Cross: constraint on dark matter from stellar dynamics and gravitational lensing

[Abridged] We present two-dimensional line-of-sight stellar kinematics of the lens galaxy in the Einstein Cross, obtained with the GEMINI 8m telescope, using the GMOS integral-field spectrograph. The velocity map shows regular rotation up to ~100 km/s around the minor axis of the bulge, consistent with axisymmetry. The velocity dispersion map shows a weak gradient increasing towards a central (R<1") value of sigma_0=170+/-9 km/s. We deproject the observed surface brightness from HST imaging to obtain a realistic luminosity density of the lens galaxy, which in turn is used to build axisymmetric dynamical models that fit the observed kinematic maps. We also construct a gravitational lens model that accurately fits the positions and relative fluxes of the four quasar images. We find that the resulting luminous and total mass distribution are nearly identical around the Einstein radius R_E = 0.89", with a slope that is close to isothermal, but which becomes shallower towards the center if indeed mass follows light. The dynamical model fits to the observed kinematic maps result in a total mass-to-light ratio (M/L)_dyn=3.7+/-0.5 M_sun/L_sun,I (in the I-band). This is consistent with the Einstein mass M_E = 1.54 x 10^10 M_sun divided by the (projected) luminosity within R_E, which yields a total mass-to-light ratio of (M/L)_E=3.4 M_sun/L_sun,I, with an error of at most a few per cent. We estimate from stellar populations model fits to colors of the lens galaxy a stellar mass-to-light ratio (M/L)_* from 2.8 to 4.1 M_sun/L_sun,I. Although a constant dark matter fraction of 20 per cent is not excluded, dark matter may play no significant role in the bulge of this ~L* early-type spiral galaxy.

astro-ph↗

arXiv2010

Kinematic analysis of nuclear spirals: feeding the black hole in NGC1097

We present a harmonic expansion of the observed line-of-sight velocity field as a method to recover and investigate spiral structures in the nuclear regions of galaxies. We apply it to the emission-line velocity field within the circumnuclear starforming ring of NGC1097, obtained with the GMOS-IFU spectrograph. The radial variation of the third harmonic terms are well described by a logarithmic spiral, from which we interpret that the gravitational potential is weakly perturbed by a two-arm spiral density wave with inferred pitch angle of of 52+/-4 degrees. This interpretation predicts a two-arm spiral distortion in the surface brightness, as hinted by the dust structures in central images of NGC1097, and predicts a combined one-arm and three-arm spiral structure in the velocity field, as revealed in the non-circular motions of the ionised gas within the circumnuclear region of this galaxy. Next, we use a simple spiral perturbation model to constrain the fraction of the measured non-circular motions that is due to radial inflow. We combine the resulting inflow velocity with the gas density in the spiral arms, inferred from emission line ratios, to estimate the mass inflow rate as a function of radius, which reaches about 0.011 Msun/yr at a distance of 70 pc from the center. This value corresponds to a fraction of about 4.2 x 10^{-3} of the Eddington mass accretion rate onto the central black hole in this LINER/Seyfert1 galaxy. We conclude that the line-of-sight velocity not only can provide a cleaner view of nuclear spirals than the associated dust, but that the presented method also allows the quantitative study of these possibly important links in fueling the centers of galaxies, including providing a handle on the mass inflow rate as a function of radius.

astro-ph.GA↗

arXiv2010

Short gamma-ray bursts from dynamically-assembled compact binaries in globular clusters: pathways, rates, hydrodynamics and cosmological setting

We present a detailed assessment of the dynamical pathways leading to the coalescence of compact objects in Globular Clusters (GCs) and Short Gamma-Ray Burst (SGRB) production. We consider primordial binaries, dynamically formed binaries (through tidal two-body and three-body exchange interactions) and direct impacts of compact objects (WD/NS/BH). We show that if the primordial binary fraction is small, close encounters dominate the production rate of coalescing compact systems. We find that the two dominant channels are the interaction of field NSs with dynamically formed binaries, and two-body encounters. We then estimate the redshift distribution and host galaxy demographics of SGRB progenitors, and find that GCs can provide a significant contribution to the overall observed rate. We have carried out hydrodynamical modeling of evolution of close stellar encounters with WD/NS/BH, and show that there is no problem in accounting for the energy budget of a typical SGRB. The particulars of each encounter are variable and lead to interesting diversity: the encounter characteristics are dependent on the impact parameter, in contrast to the merger scenario; the nature of the compact star itself can produce very different outcomes; the presence of tidal tails in which material falls back onto the central object at later times is a robust feature of these calculations, with the mass involved being larger than for binary mergers. It is thus possible to account generically in this scenario for a prompt episode of energy release, as well as for activity many dynamical time scales later (abridged).

astro-ph.HE↗

arXiv2010

The SAURON project - XVII. Stellar population analysis of the absorption line strength maps of 48 early-type galaxies

(Abridged) We present a stellar population analysis of the absorption line strength maps for 48 early-type galaxies from the SAURON sample. Using the line strength index maps of Hbeta, Fe5015, and Mgb, measured in the Lick/IDS system and spatially binned to a constant signal-to-noise, together with predictions from up-to-date stellar population models, we estimate the simple stellar population-equivalent (SSP-equivalent) age, metallicity and abundance ratio [alpha/Fe] over a two-dimensional field extending up to approximately one effective radius. We find a large range of SSP-equivalent ages in our sample, of which ~40% of the galaxies show signs of a contribution from a young stellar population. The most extreme cases of post-starburst galaxies, with SSP-equivalent ages of <=3 Gyr observed over the full field-of-view, and sometimes even showing signs of residual star-formation, are restricted to low mass systems(sigma_e <= 100 k/ms or ~2x10^10 M_sol). Spatially restricted cases of young stellar populations in circumnuclear regions can almost exclusively be linked to the presence of star-formation in a thin, dusty disk/ring, also seen in the near-UV or mid-IR. The flattened components with disk-like kinematics previously identified in all fast rotators (Krajnović et al.) are shown to be connected to regions of distinct stellar populations. These range from the young, still star-forming circumnuclear disks and rings with increased metallicity preferentially found in intermediate-mass fast rotators, to apparently old structures with extended disk-like kinematics, which are observed to have an increased metallicity and mildly depressed [alpha/Fe] ratio compared to the main body of the galaxy. The slow rotators generally show no stellar population signatures over and above the well known metallicity gradients and are largely consistent with old (>=10 Gyr) stellar populations.

astro-ph.GA↗