Publications by Michele Cappellari


Connecting stars and ionised gas with integral-field spectroscopy

NEW ASTRON REV 51 (2007) 13-17

RM McDermid, E Emsellem, KL Shapiro, R Bacon, M Bureau, M Cappellari, RL Davies, T de Zeeuw, J Falcon-Barroso, D Krajnovic, H Kuntschner, RF Peletier, M Sarzi, G van de Ven

Using integral-field spectroscopy, the SAURON survey has shown that early-type galaxies, once thought to be essentially devoid of gas, commonly show ionised gas emission. This emission is found with a rich variety of distributions and kinematics, ranging from very uniform disks or rings, and large-scale twisted structures, to flocculent and irregular streams. Such variety is missed in conventional long-slit spectroscopy, and integral-field spectroscopic data allow accurate removal of the underlying stellar continuum compared with imaging surveys, giving very low detection limits. Moreover, spectral data can simultaneously provide the stellar kinematics and populations as well as the emission-line properties. We investigate the connection between the stellar and gas properties using integral-field spectroscopy from SAURON, OASIS and GMOS, and find that, although some global trends exist, the connection between the stellar population parameters and the gas properties is in some cases puzzlingly unclear. (c) 2006 Elsevier B.V. All rights reserved.


Young kinematically decoupled components in early-type galaxies

ESO ASTROPHY SYMP (2007) 253-257

RM McDermid, E Emsellem, KL Shapiro, R Bacon, M Bureau, M Cappellari, RL Davies, PT de Zeeuw, J Falcon-Barroso, D Krajnovic, H Kuntschner, RF Peletier, M Sarzi

We present results from a series of follow-up observations of a subsample of the representative SAURON survey elliptical (E) and lenticular (SO) galaxies using the OASIS integral-field spectrograph. These observations focus on the central 10 '' x 10 '', with roughly double the spatial resolution of the SAURON observations. This increased spatial resolution reveals a number of interesting and previously unresolved features in the measured stellar kinematics and absorption-line strengths. We find that galaxies exhibiting the youngest global stellar populations (as measured with SAURON) often contain a distinctly young central region (on scales of a few hundred parsec or less) compared to the rest of the galaxy. Moreover, these compact, young components are found to be mostly counter-rotating with respect to the rest of the galaxy. Given that there is no well-established reason for such young components to 'prefer' counter- over co-rotation, this finding raises the following questions: How common are these small KDCs as a function of age? Why are there more young than old compact KDCs? Where are the equivalent co-rotating components? We explore these questions using simple simulated velocity fields and stellar population models, and find that the fading of the young component as it evolves, coupled with the fact that counter-rotating components are more easily detected in the velocity field, may help explain the observed trends.


Stars and gas in the inner parts of galaxies seen in SAURON integral field observations

\nar 51 (2007) 29-33-29-33

RF Peletier, K Fathi, EL Allard, JH Knapen, M Sarzi, G van de Ven, J Falcon-Barroso, M Cappellari, PT de Zeeuw, E Emsellem


Two-dimensional kinematics of a bar and central disk in NGC 5448

Astrophysics and Space Science Proceedings (2007) 125-128

K Fathi, G Van De Ven, R Peletier, E Emsellem, J Falcón-Barroso, M Cappellari, TD Zeeuw

© 2007, Springer Netherlands. All rights reserved. We analyse SAURON kinematic maps of the inner kpc of the early-type (Sa) barred spiral galaxy NGC 5448. The observed morphology and kinematics of the emission-line gas is patchy and perturbed, indicating clear departures from circular motion. The kinematics of the stars is more regular, and displays a small inner disk-like system embedded in a large-scale rotating structure. We focus on the [O iii] gas, and use a harmonic decomposition formalism to analyse the gas velocity field. The higher-order harmonic terms and the main kinematic features of the observed data are consistent with an analytically constructed simple bar model, which is derived using linear theory. Our study illustrates how the harmonic decomposition formalism can be used as a powerful tool to quantify non-circular motions in observed gas velocity fields.


A sauron study of stars and gas in sa bulges

Astrophysics and Space Science Proceedings (2007) 201-206

J Falcon-Barroso, R Bacon, M Bureau, M Cappellari, RL Davies, PT De Zeeuw, E Emsellem, K Fathi, D Krajnovic, H Kuntschner, RM McDermid, RF Peletier, M Sarzi

© 2007, Springer Netherlands. All rights reserved. We present results from our ongoing effort to understand the morphological and kinematical properties of early-type galaxies using the integral-field spectrograph SAURON. We discuss the relation between the stellar and gas morphology and kinematics in our sub-sample of 24 representative Sa spiral bulges. We focus on the frequency of kinematically decoupled components and on the presence of star formation in circumnuclear rings.


The stellar Populations of E and SO galaxies as seen with SAURON

ESO ASTROPHY SYMP (2007) 123-128

H Kuntschner, E Emsellem, R Bacon, M Bureau, M Cappellari, RL Davies, T de Zeeuw, J Falcon-Barroso, D Krajnovic, RM McDermid, RF Peletier, M Serzi

We present selected results from integral-field spectroscopy of 48 early-type galaxies observed as part of the SAURON survey. Maps of the H beta, Fe5015, Mgb and Fe5270 indices in the Lick/IDS system were derived for each of the survey galaxies. The metal line strength maps show generally negative gradients with increasing radius roughly consistent, with the morphology of the light profiles. Remarkable deviations from this general trend exist, particularly the Mg b isoindex contours appear to be flatter than the isophotes of the surface brightness for about 40% of our galaxies without significant dust features. Generally these galaxies exhibit significant rotation. We infer from this that the fast-rotating component features a higher metallicity and/or an increased Mg/Fe ratio, as compared to the galaxy as a whole.We also use the line strength maps to compute average values integrated over circular apertures of one effective radius, and derive luminosity weighted ages and metallicities. The lenticular galaxies show a, wide range in age and metallicity estimates, while elliptical galaxies tend to occupy regions of older stellar populations.


SAURON observations of sa bulges: The formation of a kinematically decoupled core in NGC 5953

ESO ASTROPHY SYMP (2007) 111-115

J Falcon-Barroso, R Bacon, M Bureau, M Cappellari, RL Davies, PT de Zeeuw, E Emsellem, K Fathi, D Krajnovic, H Kuntschner, RM McDermid, RF Peletier, M Sarzi

We present results from our ongoing effort to understand the nature and evolution of nearby galaxies using the SAURON integral-field spectrograph. In this proceeding we focus on the study of the particular case formed by the interacting galaxies NGC 5953 and NGC 5954. We present stellar and gas kinematics of the central regions of NGC5953. We use a simple procedure to determine the age of the stellar populations in the central regions and argue that we may be witnessing the formation of a kinematically decoupled component (hereafter KDC) from cold gas being acquired during the ongoing interaction with NGC 5954.


The kinematics and morphology of the H-I in gas-poor galaxies

NEW ASTRON REV 51 (2007) 8-12

TA Oosterloo, R Morganti, PT de Zeeuw, RM McDermid, D Krajnovic, M Cappellari, F Kenn, A Weijmans, M Sarzi

We present the results of deep Westerbork Synthesis Radio Telescope observations of the neutral hydrogen in 12 nearby elliptical and lenticular galaxies selected from a representative sample of nearby galaxies that were studied earlier at optical wavelengths with the integral-field spectrograph sauron. The observed objects are field galaxies, or (in two cases) are located in poor-group environments. We detect Hi in 70% of the galaxies. This detection rate is much higher than in previous, shallower single-dish surveys, and is similar to that for the ionised gas. The results suggest that at faint detection levels the presence of Hi is a relatively common characteristic of field early-type galaxies. The presence of regular disc-like structures is as common as Hi in offset clouds and tails. All galaxies where Hi is detected also contain ionised gas, whereas no Hi is found around galaxies without ionised gas. Galaxies with regular HI discs tend to have strong emission from ionised gas. In these cases, the similar kinematics of the neutral hydrogen and ionised gas suggest that they form one structure. We do not find a trend between the presence of Hi and the global age of the stellar population or with the global dynamical characteristics of the galaxies. If fast and slow rotators represent the relics of different formation paths, this does not appear in the presence and characteristics of the Hi. The links observed between the large-scale gas and the characteristics on the nuclear scale (e.g. the presence of kinematically decoupled cores and radio continuum emission), suggest that for the majority of the cases the gas is acquired through merging, but the lack of correlation with the stellar-population age suggests that smooth, cold accretion could be an alternative scenario, at least in some galaxies. In either case, the data suggest that early-type galaxies continue to build-up their mass to the present. (c) 2006 Elsevier B.V. All rights reserved.


The black hole in NGC 3379: a comparison of gas and stellar dynamical mass measurements with HST and integral-field data

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 370 (2006) 559-579

KL Shapiro, M Cappellari, T de Zeeuw, RM McDermid, K Gebhardt, RCE van den Bosch, TS Statler


Stellar populations of kinematically decoupled cores in E/S0 galaxies

Proceedings of the International Astronomical Union 2 (2006) 122-

RM McDermid, E Emsellem, KL Shapiro, R Bacon, M Bureau, M Cappellari, RL Davies, T De Zeeuw, J Falcón-Barroso, D Krajnovíc, H Kuntschner, RF Peletier, M Sarzi

In this poster contribution, we present results from high spatial resolution integral-field spectroscopy of elliptical (E) and lenticular (S0) galaxies from the SAURON representative survey, obtained with the OASIS and GMOS spectrographs. These seeing-limited observations explore the central 10'10 (typically one kiloparsec diameter) regions of these galaxies using a spatial sampling four times higher than SAURON (027 vs. 094 spatial elements), resulting in almost a factor of two improvement in the median PSF. These data allow accurate study of the central regions to complement the large-scale view provided by SAURON. We derive the stellar and gas kinematics, stellar absorption-line strengths and nebular emission-line strengths for our sample, and derive maps of the luminosity-weighted stellar age, metallicity and abundance ratio via stellar population models. From these data we find a wealth of structures either not seen or poorly resolved in the SAURON data, including a number of kinematically-decoupled cores (KDCs) in the centres of some galaxies. We compare the intrinsic size and luminosity-weighted stellar age of all the visible KDCs in the full SAURON sample, and find two types of components: kiloparsec-scale KDCs, which are older than 8 Gyr, and are found in galaxies with little net rotation; and compact KDCs, which have intrinsic diameters of less than a few hundred parsec, show a range of stellar ages from 0.5 - 15 Gyr (with 5/6 younger than 5 Gyr), are found exclusively in fast-rotating galaxies, and are close to counter-rotating around the same axis as their host. Of the 7 galaxies in the SAURON sample with integrated luminosity-weighted ages less than 5 Gyr, 5 show such compact KDCs, suggesting a link between counter-rotation and recent star-formation. We show that this may be partly due to a combination of small sample size at young ages, and an observational bias, since young KDCs are easier to detect than their older and/or co-rot ating counterparts.


Dark matter in the central regions of early type galaxies

EAS Publications Series 20 (2006) 127-130

M Cappellari, R Bacon, M Bureau, MC Damen, RL Davies, PT De Zeeuw, E Emsellem, J Falcon-Barroso, D Krajnović, H Kuntschner, RM McDermid, RF Peletier, M Sarzi, RCE Van Den Bosch, G Van De Ven

We investigate the well-known correlations between the dynamical rnass-to-light ratio M/L and other global observables of elliptical (E) arid lenticular (S0) galaxies. We construct two-integral Jeans and three-integral Schwarzschild dynamical models for a sample of 25 E/S0 galaxies with SAURON integral-field stellar kinematics to about one effective (half-light) radius Re. The comparison of the dynamical M/L with the (M/L)pop inferred from the analysis of the stellar population, indicates that dark matter in early-type galaxies contributes ∼30% of the total mass inside one Re, in agreement with previous studies, with significant variations from galaxy to galaxy. Our results suggest a variation in M/L at constant (M/L)pop, which seems to be linked to the galaxy dynamics. We speculate that fast rotating galaxies have lower dark matter fractions than the slow rotating and generally more massive ones. © EAS, EDP Sciences 2006.


The SAURON project - VI. Line strength maps of 48 elliptical and lenticular galaxies

Monthly Notices of the Royal Astronomical Society 369 (2006) 497-528

H Kuntschner, E Emsellem, R Bacon, M Bureau, M Cappellari, RL Davies, PT De Zeeuw, J Falcón-Barroso, D Krajnović, RM McDermid, RF Peletier, M Sarzi

We present absorption line strength maps of 48 representative elliptical and lenticular galaxies obtained as part of a survey of nearby galaxies using our custom-built integral-field spectrograph, SAURON, operating on the William Herschel Telescope. Using high-quality spectra, spatially binned to a constant signal-to-noise ratio, we measure four key age, metallicity and abundance ratio sensitive indices from the LickIDS system over a two-dimensional field extending up to approximately one effective radius. A discussion of calibrations and offsets is given, along with a description of error estimation and nebular emission correction. We modify the classical Fe5270 index to define a new index, , which maximizes the useable spatial coverage of SAURON. Maps of Hβ, Fe5015, Mg b and are presented for each galaxy. We use the maps to compute average line strengths integrated over circular apertures of one-eighth effective radius, and compare the resulting relations of index versus velocity dispersion with previous long-slit work. The metal line strength maps show generally negative gradients with increasing radius roughly consistent with the morphology of the light profiles. Remarkable deviations from this general trend exist, particularly the Mg b isoindex contours appear to be flatter than the isophotes of the surface brightness for about 40 per cent of our galaxies without significant dust features. Generally, these galaxies exhibit significant rotation. We infer from this that the fast-rotating component features a higher metallicity andor an increased MgFe ratio as compared to the galaxy as a whole. The Hβ maps are typically flat or show a mild positive outwards radial gradient, while a few galaxies show strong central peaks andor elevated overall Hβ strength likely connected to recent star formation activity. For the most prominent post-starburst galaxies, even the metal line strength maps show a reversed gradient. © 2006 RAS.


Stellar populations of decoupled cores in E/S0 galaxies with sauron and oasis

Proceedings of the International Astronomical Union 2 (2006) 399-403

RM McDermid, E Emsellem, KL Shapiro, R Bacon, M Bureau, M Cappellari, RL Davies, T De Zeeuw, J Falcón-Barroso, D Krajnović, H Kuntschner, RF Peletier, M Sarzi

We summarize results from McDermid et al. (2006), who present a set of follow-up observations of the sauron representative survey of early-type galaxies. We used the oasis integral-field spectrograph (while at the Canada-France-Hawaii Telescope) to obtain high spatial resolution spectra of 28 elliptical and lenticular galaxies. These seeing-limited data have on average twice the spatial resolution of the sauron data, albeit over a smaller field. These new data reveal previously unresolved features in these objects' stellar kinematics, stellar populations, and ionized gas properties. In this contribution, we focus on the discovery of a population of compact kinematically decoupled cores in a number of our sample galaxies. These compact cores are related to regions of young stars, and counter-rotate around the host galaxy's minor axis. We compare these objects to previously known decoupled components, which in contrast are composed of old stars, and which rotate around axes unrelated to the host galaxy's kinematics or shape. A key difference between these two kinds of decoupled cores are their physical size and relative mass. The compact decoupled cores are smaller than a few hundred parsec, and constitute less than a few percent of the total galaxy mass. The classical decoupled cores exist on kiloparsec scales, and comprise around a factor 10 more mass. We suggest that the small components are only found with young ages because of their low mass-to-light ratio. We show that after a few Gyrs, these components fade into the background galaxy, making them more difficult to detect. We draw the following conclusions: 1) young stars found in early-type galaxies are very often associated with centrally-concentrated counter-rotating components; 2) the small mass fraction and kinematic decoupling of these cores suggests that the star formation is associated to minor accretion events, which effectively drive the spread in luminosity-weighted ages found in early-type galaxies; and 3) such decoupled components may be common in all early-type galaxies, but not directly observed due to their small contribution to the total galaxy light at older ages. © 2007 International Astronomical Union.


Neutral hydrogen in nearby elliptical and lenticular galaxies: The continuing formation of early-type galaxies

Monthly Notices of the Royal Astronomical Society 371 (2006) 157-169

R Morganti, PT De Zeeuw, TA Oosterloo, RM McDermid, D Krajnović, M Cappellari, F Kenn, A Weijmans, M Sarzi

We present the results of deep Westerbork Synthesis Radio Telescope observations of neutral hydrogen in 12 nearby elliptical and lenticular galaxies. The selected objects come from a representative sample of nearby galaxies earlier studied at optical wavelengths with the integralfield spectrograph SAURON (Spectrographic Areal Unit for Research on Optical Nebulae). They are field galaxies, or (in two cases) located in poor group environments. We detect HI - both in regular discs as well as in clouds and tails offset from the host galaxy - in 70 per cent of the galaxies. This detection rate is much higher than in previous, shallower single-dish surveys, and is similar to that for the ionized gas. The results suggest that at faint detection levels the presence of H I is a relatively common characteristic of field early-type galaxies, confirming what was suggested twenty years ago by Jura based on IRAS observations. The observed total Hi masses range between a few times 10 6 to just over 10 9 M ⊙. The presence of regular disc-like structures is a situation as common as Hi in offset clouds and tails around early-type galaxies. All galaxies where Hi is detected also contain ionized gas, whereas no Hi is found around galaxies without ionized gas. Galaxies with regular Hi discs tend to have strong emission from ionized gas. In these cases, the similar kinematics of the neutral hydrogen and ionized gas suggest that they form one structure. The kinematical axis of the stellar component is nearly always misaligned with respect to that of the gas. We do not find a clear trend between the presence of H I and the global age of the stellar population or the global dynamical characteristics of the galaxies. More specifically, H I detections are uniformly spread through the (V/σ, ∈) diagram. If fast and slow rotators - galaxies with high and low specific angular momentum - represent the relics of different formation paths, this does not appear in the presence and characteristics of the H i. Our observations support the idea that gas accretion is common and does not happen exclusively in peculiar early-type galaxies. The links observed between the large-scale gas and the characteristics on the nuclear scale (e.g. the presence of kinematically decoupled cores, radio continuum emission etc.) suggest that for the majority of the cases the gas is acquired through merging, but the lack of correlation with the stellar population age suggests that smooth, cold accretion could be an alternative scenario, at least in some galaxies. In either case, the data suggest that early-type galaxies continue to build their mass up to the present. © 2006 RAS.


The SAURON project - VII. Integral-field absorption and emission-line kinematics of 24 spiral galaxy bulges

Monthly Notices of the Royal Astronomical Society 369 (2006) 529-566

J Falcón-Barroso, R Bacon, M Bureau, M Cappellari, RL Davies, PT De Zeeuw, E Emsellem, K Fathi, D Krajnović, H Kuntschner, RM McDermid, RF Peletier, M Sarzi

We present observations of the stellar and gas kinematics for a representative sample of 24 Sa galaxies obtained with our custom-built integral-field spectrograph SAURON operating on the William Herschel Telescope. The data have been homogeneously reduced and analysed by means of a dedicated pipeline. All resulting data cubes were spatially binned to a minimum mean signal-to-noise ratio of 60 per spatial and spectral resolution element. Our maps typically cover the bulge-dominated region. We find a significant fraction of kinematically decoupled components (12/24), many of them displaying central velocity dispersion minima. They are mostly aligned and co-rotating with the main body of the galaxies, and are usually associated with dust discs and rings detected in unsharp-masked images. Almost all the galaxies in the sample (22/24) contain significant amounts of ionized gas which, in general, is accompanied by the presence of dust. The kinematics of the ionized gas are consistent with circular rotation in a disc co-rotating with respect to the stars. The distribution of mean misalignments between the stellar and gaseous angular momenta in the sample suggests that the gas has an internal origin. The [O III]/Hβ ratio is usually very low, indicative of current star formation, and shows various morphologies (ring-like structures, alignments with dust lanes or amorphous shapes). The star formation rates (SFRs) in the sample are comparable with that of normal disc galaxies. Low gas velocity dispersion values appear to be linked to regions of intense star formation activity. We interpret this result as stars being formed from dynamically cold gas in those regions. In the case of NGC 5953, the data suggest that we are witnessing the formation of a kinematically decoupled component from cold gas being acquired during the ongoing interaction with NGC 5954. © 2006 RAS.


Star formation in nearby early-type galaxies: Mapping in UV, optical and CO

Proceedings of the International Astronomical Union 2 (2006) 304-

M Bureau, R Bacon, M Cappellari, F Combes, RL Davies, PT De Zeeuw, E Emsellem, J Falcn-Barroso, H Jeong, D Krajnovi, H Kuntschner, RM McDermid, RF Peletier, M Sarzi, KL Shapiro, G Van De Ven, SK Yi, LM Young

The SAURON integral-field survey reveals that small (∼0.1,Re) kinematically decoupled cores (KDCs) in early-type galaxies are increasingly young toward the center and are typically found in fast-rotating galaxies, while large KDCs (∼0.5 Re) have homogeneously old stars and are present in non-rotating galaxies (McDermid et al. 2006). GALEX UV imaging further allows the direct identification of regions of recent star formation (0.5 Gyr). In NGC 2974 for example, young stars are identified in the center and an outer ring Jeong et al. 2006). Nuclear and inner ionised-gas rings (Sarzi et al. 2006) then suggest that current star formation is bar-driven. The CO detection rate of SAURON early-type galaxies is 40% (Combes et al. in prep.). Synthesis imaging reveals that it is generally contained in a well-ordered central disk, both in galaxies with a (young) central stellar disk (e.g. NGC 4459, NGC 4526) or a (young) KDC (e.g. NGC 3032, NGC 4150) (Young et al. in prep.). CO also traces well the young stellar populations and ionised gas distribution and kinematics, but in KDCs not always the stellar kinematics Emsellem et al. 2004; Sarzi et al. 2006; Kuntschner et al. 2006). © 2007 International Astronomical Union.


Stellar Populations in KDCs of Sa Galaxies

Proceedings of the International Astronomical Union Cambridge University Press (CUP) 2 (2006)

J Falcón-Barroso, R Bacon, M Cappellari, R Davies, PT de Zeeuw, E Emsellem, D Krajnović, H Kuntschner, RM McDermid, RF Peletier, M Sarzi, G van de Ven


The SAURON project - VIII. OASIS/CFHT integral-field spectroscopy of elliptical and lenticular galaxy centres

Monthly Notices of the Royal Astronomical Society 373 (2006) 906-958

RM Mcdermid, E Emsellem, KL Shapiro, R Bacon, M Bureau, M Cappellari, RL Davies, T De Zeeuw, J Falcón-Barroso, D Krajnović, H Kuntschner, RF Peletier, M Sarzi

We present high spatial resolution integral-field spectroscopy of 28 elliptical (E) and lenticular (SO) galaxies from the SAURON representative survey obtained with the OASIS spectrograph during its operation at the Canada-France-Hawaii Telescope. These seeing-limited observations explore the central 8 × 10 arcsec 2 (typically 1 kpc diameter) regions of these galaxies using a spatial sampling four times higher than SAURON (0.27-arcsec versus 0.94-arcsec spatial elements), resulting in almost a factor of 2 improvement in the median point spread function. These data allow accurate study of the central regions to complement the large-scale view provided by SAURON. Here we present the stellar and gas kinematics, stellar absorption-line strengths and nebular emission-line strengths for this sample. We also characterize the stellar velocity maps using the 'kinemetry' technique, and derive maps of the luminosity-weighted stellar age, metallicity and abundance ratio via stellar population models. We give a brief review of the structures found in our maps, linking also to larger-scale structures measured with SAURON. We present two previously unreported kinematically decoupled components (KDCs) in the centres of NGC 3032 and NGC 4382. We compare the intrinsic size and luminosity-weighted stellar age of all the visible KDCs in the full SAURON sample, and find two types of components: kiloparsec-scale KDCs, which are older than 8 Gyr, and are found in galaxies with little net rotation; and compact KDCs, which have intrinsic diameters of less than a few hundred parsec, show a range of stellar ages from 0.5 to 15 Gyr (with 5/6 younger than 5 Gyr), are found exclusively in fast-rotating galaxies, and are close to counter-rotating around the same axis as their host. Of the seven galaxies in the SAURON sample with integrated luminosity-weighted ages less than 5 Gyr, five show such compact KDCs, suggesting a link between counter-rotation and recent star formation. We show that this may be due to a combination of small sample size at young ages, and an observational bias, since young KDCs are easier to detect than their older and/or corotating counterparts. © 2006 RAS.


Triaxial orbit-based model of NGC 4365

Proceedings of the International Astronomical Union 2 (2006) 331-332

RCE Van Den Bosch, G Van De Ven, M Cappellari, PT De Zeeuw

We have developed an orbit-based method for constructing triaxial models of elliptical galaxies, which fit their observed surface brightness and kinematics (van den Bosch et al). We have tested this extended Schwarzschild method (1979) against analytical models with general distribution functions (DF) and find that we can recover the DF (van de Ven et al). Here, we present a model of NGC 4365. © 2007 International Astronomical Union.


The nature of galactic bulges from SAURON absorption line strength maps

Proceedings of the International Astronomical Union 2 (2006) 485-488

RF Peletier, J Falcón-Barroso, K Ganda, R Bacon, M Cappellari, RL Davies, PT De Zeeuw, E Emsellem, D Krajnović, H Kuntschner, RM McDermid, M Sarzi, G Van De Ven

We discuss SAURON absorption line strength maps of a sample of 24 early-type spirals, mostly Sa. From the Lick indices H, Mgb and Fe 5015 we derive SSP-ages and metallicities. By comparing the scaling relations of Mg b and H and central velocity dispersion with the same relation for the edge-on sample of Falcn-Barroso et al. (2002) we derive a picture in which the central regions of Sa galaxies contain at least 2 components: one (or more) thin, disc-like component, often containing recent star formation, and another, elliptical-like component, consisting of old stars and rotating more slowly, dominating the light above the plane. If one defines a bulge to be the component responsible for the light in excess of the outer exponential disc, then many Sa-bulges are dominated by a thin, disc-like component containing recent star formation. © 2007 International Astronomical Union.

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