Publications by Michele Cappellari

The SAURON project - IV. The mass-to-light ratio, the virial mass estimator and the Fundamental Plane of elliptical and lenticular galaxies

Monthly Notices of the Royal Astronomical Society 366 (2006) 1126-1150

M Cappellari, Bacon, R., Bureau, M., Damen, M. C.

Morphology and kinematics of the ionised gas in early-type galaxies

NEW ASTRON REV 49 (2006) 515-520

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

We present results of our ongoing study of the morphology and kinematics of the ionised gas in 48 representative nearby elliptical and lenticular galaxies using the SAURON integral-field spectrograph on the 4.2m William Herschel Telescope. Making use of a recently developed technique, emission is detected in 75% of the galaxies. The ionised-gas distributions display varied morphologies, ranging from regular gas disks to filamentary structures. Additionally, the emission-line kinematic maps show, in general, regular motions with smooth variations in kinematic position angle. In most of the galaxies, the ionised-gas kinematics is decoupled from the stellar counterpart, but only some of them present signatures of recent accretion of gaseous material. The presence of dust is very common in our sample and is usually accompanied by gas emission. Our analysis of the [Om]/H beta emission-line ratios, both across the whole sample as well as within the individual galaxies, suggests that there is no unique mechanism triggering the ionisation of the gas. (c) 2005 Elsevier B.V. All rights reserved.

Late-type galaxies observed with SAURON: two-dimensional stellar and emission-line kinematics of 18 spirals


K Ganda, J Falcon-Barroso, RF Peletier, M Cappellari, E Emsellem, RM McDermid, PT de Zeeuw, CM Carollo, DR Andersen, RA Swaters

VLT diffraction-limited imaging and spectroscopy in the NIR: Weighing the black hole in Centaurus A with NACO

ASTROPHYSICAL JOURNAL 643 (2006) 226-237

N Haring-Neumayer, M Cappellari, H-W Rix, M Hartung, MA Prieto, K Meisenheimer, R Lenzen

The SAURON project - V. Integral-field emission-line kinematics of 48 elliptical and lenticular galaxies

Monthly Notices of the Royal Astronomical Society 366 (2006) 1151-1200

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

We present the emission-line fluxes and kinematics of 48 representative elliptical and lenticular galaxies obtained with our custom-built integral-field spectrograph, SAURON, operating on the William Herschel Telescope. Hβ, [O III] λλ.4959,5007 and [N I] λλ5198,5200 emission lines were measured using a new procedure that simultaneously fits both the stellar spectrum and the emission lines. Using this technique we can detect emission lines down to an equivalent width of 0.1 Å set by the current limitations in describing galaxy spectra with synthetic and real stellar templates, rather than by the quality of our spectra. Gas velocities and velocity dispersions are typically accurate to within 14 and 20 km s -1, respectively, and at worse to within 25 and 40 km s~L. The errors on the flux of the [O III] and Hβ lines are on average 10 and 20 per cent, respectively, and never exceed 30 per cent. Emission is clearly detected in 75 per cent of our sample galaxies, and comes in a variety of resolved spatial distributions and kinematic behaviours. A mild dependence on the Rubble type and galactic environment is observed, with higher detection rates in lenticular galaxies and field objects. More significant is the fact that only 55 per cent of the galaxies in the Virgo cluster exhibit clearly detected emission. The ionized-gas kinematics is rarely consistent with simple coplanar circular motions. However, the gas almost never displays completely irregular kinematics, generally showing coherent motions with smooth variations in angular momentum. In the majority of the cases, the gas kinematics is decoupled from the stellar kinematics, and in half of the objects this decoupling implies a recent acquisition of gaseous material. Over the entire sample however, the distribution of the mean misalignment values between stellar and gaseous angular momenta is inconsistent with a purely external origin. The distribution of kinematic misalignment values is found to be strongly dependent on the apparent flattening and the level of rotational support of galaxies, with flatter, fast rotating objects hosting preferentially corotating gaseous and stellar systems. In a third of the cases, the distribution and kinematics of the gas underscore the presence of nonaxisymmetric perturbations of the gravitational potential. Consistent with previous studies, the presence of dust features is always accompanied by gas emission while the converse is not always true. A considerable range of values for the [O III]/Hβ ratio is found both across the sample and within single galaxies. Despite the limitations of this ratio as an emission-line diagnostic, this finding suggests either that a variety of mechanisms is responsible for the gas excitation in E and S0 galaxies or that the metallicity of the interstellar material is quite heterogeneous. © 2006 RAS.

NGC 7679: an anomalous, composite Seyfert 1 galaxy whose X-ray luminous AGN vanishes at optical wavelengths

ASTRONOMY & ASTROPHYSICS 447 (2006) 441-451

LM Buson, M Cappellari, EM Corsini, EV Held, J Lim, A Pizzella

Stellar populations in KDCs of Sa galaxies

Proceedings of the International Astronomical Union 2 (2006) 470-474

J Falcn-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

We present integral-field observations of kinematically decoupled components (KDCs) in a sample of 24 Sa galaxies part of the SAURON Survey. We show how the V/ maps can be used to highlight the presence of the KDC and investigate their stellar populations (i.e. age) to understand their origin (i.e. secular vs hierarchical scenarios). We find that KDCs can be long-lived and are typically well aligned with the galaxies kinematical major axis, supporting mounting evidence that secular evolution becomes important at intermediate redshifts. Dynamically colder ones seem to host younger stellar populations. We also relate these features to the ones found in our sample of 48 elliptical and lenticular galaxies. We find that there is no age vs size relation for these decoupled components in Sa galaxies, suggesting that the dominant factor determining their size is the amount of star formation they have been subject to during their life time. © 2007 International Astronomical Union.

Stellar kinematics and populations of early-type galaxies with the SAURON and OASIS integral-field spectrographs

NEW ASTRON REV 49 (2006) 521-535

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

We summarise the results and achievements of integral-field spectroscopy of early-type galaxies.. observed as part of a survey using both the SAURON and OASIS spectrographs. From the perspective of integral-field spectroscopy, these otherwise smooth and featureless objects show a wealth of structure, both in their stellar kinematics and populations. We focus on the stellar content, and examine properties on both kiloparsec scales with SAURON, and scales of 100's of parsecs with OASIS. These complementary studies reveal two types of kinematically distinct components (KDCs), differing primarily in their intrinsic sizes. In previous studies, KDCs and their host galaxies have generally been found to be unremarkable in other aspects. We show that large KDCs, typical of the well-studied cases, indeed show little or no age differences with their host galaxy. The KDCs detected with the higher spatial-resolution of OASIS are intrinsically smaller and include, in contrast, a significant fraction of young stars. We speculate on the relationship between KDCs and their host galaxies, and the implications for young populations in early-type galaxies. (c) 2005 Elsevier B.V. All rights reserved.

Kinemetry: A generalization of photometry to the higher moments of the line-of-sight velocity distribution

Monthly Notices of the Royal Astronomical Society 366 (2006) 787-802

D Krajnović, M Cappellari, PT De Zeeuw, Y Copin

We present a generalization of surface photometry to the higher-order moments of the line-of-sight velocity distribution of galaxies observed with integral-field spectrographs. The generalization follows the approach of surface photometry by determining the best-fitting ellipses along which the profiles of the moments can be extracted and analysed by means of harmonic expansion. The assumption for the odd moments (e.g. mean velocity) is that the profile along an ellipse satisfies a simple cosine law. The assumption for the even moments (e.g. velocity dispersion) is that the profile is constant, as it is used in surface photometry. We test the method on a number of model maps and discuss the meaning of the resulting harmonic terms. We apply the method to the kinematic moments of an axisymmetric model elliptical galaxy and probe the influence of noise on the harmonic terms. We also apply the method to SAURON observations of NGC 2549, NGC 2974, NGC 4459 and NGC 4473 where we detect multiple co- and counter-rotating (NGC 2549 and NGC 4473, respectively) components. We find that velocity profiles extracted along ellipses of early-type galaxies are well represented by the simple cosine law (with 2 per cent accuracy), while possible deviations are carried in the fifth harmonic term which is sensitive to the existence of multiple kinematic components, and has some analogy to the shape parameter of photometry. We compare the properties of the kinematic and photometric ellipses and find that they are often very similar, but a study on a larger sample is necessary. Finally, we offer a characterization of the main velocity structures based only on the kinemetric parameters which can be used to quantify the features in velocity maps. © 2006 RAS.

Dynamical modelling of stars and gas in NGC 2974: determination of mass-to-light ratio, inclination and orbital structure using the Schwarzschild method


D Krajnovic, M Cappellari, E Emsellem, RM McDermid, PT de Zeeuw

A bar signature and central disc in the gaseous and stellar velocity fields of NGC 5448


K Fathi, G van de Ven, RF Peletier, E Emsellem, J Falcon-Barroso, M Cappellari, T de Zeeuw

The nuclear orbital distribution in galaxies as a fossil record of black hole formation from integral-field spectroscopy

CLASSICAL QUANT GRAV 22 (2005) S347-S353

M Cappellari, RM McDermid

In the past decade, most effort in the study of supermassive black holes (BHs) has been devoted to measuring their masses. This led to the finding of the tight M-BH-sigma relation, which indicates the existence of strong links between the formation of the BHs and of their host spheroids. Many scenarios have been proposed to explain this relation, and all agree on the key role of BHs' growth and feedback in shaping their host galaxies. However, the currently available observational constraints, essentially BH masses and galaxy photometry, are not sufficient to conclusively select among the alternatives. A crucial piece of information on black-hole formation is recorded in the orbital distribution of the stars, which can only be extracted from high-resolution integral-field (IF) stellar kinematics. The introduction of IF spectrographs with adaptive optics on large telescopes opens a new era in the study of BHs by finally allowing this key element to be uncovered. This information will be complementary to what will be provided by the LISA gravitational wave satellite, which can directly detect coalescing BHs. Here, an example is presented for the recovery of the orbital distribution in the centre of the giant elliptical galaxy M87, which has a well-resolved BH sphere of influence, using SAURON IF kinematics.

Formation and evolution of S0 galaxies: A SAURON case study of NGC 7332

Monthly Notices of the Royal Astronomical Society 350 (2004) 35-46

J Falcón-Barroso, RF Peletier, E Emsellem, H Kuntschner, K Fathi, M Bureau, R Bacon, M Cappellari, Y Copin, RL Davies, T De Zeeuw

We present SAURON integral-field observations of the S0 galaxy NGC 7332. Existing broadband ground-based and Hubble Space Telescope (HST) photometry reveals a double-disc structure and a boxy bulge interpreted as a bar viewed close to edge-on. The SAURON two-dimensional stellar kinematic maps confirm the existence of the bar and inner disc but also uncover the presence of a cold counter-rotating stellar component within the central 250 pc. The Hβ and [O III] emission line maps show that the ionized gas has a complex morphology and kinematics, including both a component counter-rotating with respect to the stars and a fainter corotating one. Analysis of the absorption line-strength maps show that NGC 7332 is young everywhere. The presence of a large-scale bar can explain most of those properties, but the fact that we see a significant amount of unsettled gas, together with a few peculiar features in the maps, suggests that NGC 7332 is still evolving. Interactions as well as bar-driven processes must thus have played an important role in the formation and evolution of NGC 7332, and presumably of S0 galaxies in general.

The second generation VLT instrument MUSE: Science drivers and instrument design

P SOC PHOTO-OPT INS 5492 (2004) 1145-1149

R Bacon, S Bauer, R Bower, S Cabrit, M Cappellari, M Carollo, FO Combes, R Davies, B Delabre, H Dekker, J Devriendt, S Djidel, M Duchateau, JP Dubois, E Emsellem, P Ferruit, M Franx, G Gilmore, B Guiderdoni, F Henault, N Hubin, B Jungwiert, A Kelz, M Le Louarn, I Lewis, JL Lizon, R Mc Dermid, S Morris, U Laux, O Le Fevre, B Lantz, S Lilly, J Lynn, L Pasquin, A Pecontal, PPD Popovic, A Quirrenbach, R Reiss, M Roth, M Steinmetz, R Stuik, L Wisotzki, T de Zeeuw

The Multi Unit Spectroscopic Explorer (MUSE) is a second generation VLT panoramic integral-field spectrograph operating in the visible wavelength range. MUSE has a field of 1x1 arcmin(2) sampled at 0.20.2 arcsec(2) and is assisted by a ground layer adaptive optics system using four laser guide stars. The simultaneous spectral range is 0.465-0.93 mum, at a resolution of Rsimilar to3000. MUSE couples the discovery potential of a large imaging device to the measuring capabilities of a high-quality spectrograph, while taking advantage of the increased spatial resolution provided by adaptive optics. This makes MUSE a unique and tremendously powerful instrument for discovering and characterizing objects that lie beyond the reach of even the deepest imaging surveys. MUSE has also a high spatial resolution mode with 7.5x7.5 arcsec(2) field of view sampled at 25 milli-arcsec. In this mode MUSE should be able to get diffraction limited data-cube in the 0.6-1 mum wavelength range. Although MUSE design has been optimized for the study of galaxy formation and evolution, it has a wide range of possible applications; e.g. monitoring of outer planets atmosphere, young stellar objects environment, supermassive black holes and active nuclei in nearby galaxies or massive spectroscopic survey of stellar fields.

The SAURON project - III. Integral-field absorption-line kinematics of 48 elliptical and lenticular galaxies

Monthly Notices of the Royal Astronomical Society 352 (2004) 721-743

E Emsellem, M Cappellari, RF Peletier, RM McDermid, R Bacon, M Bureau, Y Copin, RL Davies, D Krajnović, H Kuntschner, BW Miller, PT De Zeeuw

We present the stellar kinematics of 48 representative elliptical and lenticular galaxies obtained with our custom-built integral-field spectrograph SAURON operating on the William Herschel Telescope. The data were homogeneously processed through a dedicated reduction and analysis pipeline. All resulting SAURON data cubes were spatially binned to a constant minimum signal-to-noise ratio. We have measured the stellar kinematics with an optimized (penalized pixel-fitting) routine which fits the spectra in pixel space, via the use of optimal templates, and prevents the presence of emission lines to affect the measurements. We have thus generated maps of the mean stellar velocity V, the velocity dispersion σ, and the Gauss-Hermite moments h 3 and h 4 of the line-of-sight velocity distributions. The maps extend to approximately one effective radius. Many objects display kinematic twists, kinematically decoupled components, central stellar discs, and other peculiarities, the nature of which will be discussed in future papers of this series.

Orbital structure of triaxial galaxies

IAU SYMP (2004) 179-180

G van de Ven, E Verolme, M Cappellari, T de Zeeuw

We have developed a method to construct realistic triaxial dynamical models for elliptical galaxies, allowing us to derive best-fitting parameters, such as the mass-to-light ratio and the black hole mass, and to study the orbital structure. We use triaxial theoretical Abel models to investigate the robustness of the method.

OASIS high-resolution integral field spectroscopy of the SAURON ellipticals and lenticulars

ASTRON NACHR 325 (2004) 100-103

R McDermid, E Emsellem, M Cappellari, H Kuntschner, R Bacon, M Bureau, Y Copin, RL Davies, J Falcon-Barroso, P Ferruit, D Krajnovic, RF Peletier, K Shapiro, F Wernli, PT de Zeeuw

We present a summary of high-spatial resolution follow-up observations of the elliptical (E) and lenticular (SO) galaxies in the SAURON survey using the OASIS integral field spectrograph. The OASIS observations explore the central 8" x 10" regions of these galaxies using a spatial sampling four times higher than SAURON, often revealing previously undiscovered features. Around 75% (31/48) of the SAURON E/SOs with central velocity dispersion greater than or similar to 120 kin s(-1) were observed with OASIS, covering well the original SAURON representative sample. We present here an overview of this follow-up survey, and some preliminary results on individual objects, including a previously unreported counter-rotating core in NGC4382; the decoupled stellar and gas velocity fields of NGC 2768; and the strong age gradient towards the centre of NGC 3489.

Parametric recovery of line-of-sight velocity distributions from absorption-line spectra of galaxies via penalized likelihood


M Cappellari, E Emsellem

SAURON dynamical modeling of NGC 2974

IAU SYMP (2004) 305-306

D Krajnovic, M Cappellari, E Emsellem, R McDermid

We present a three-integral orbit superposition Schwarschild model of NGC 2974, observed with the integral-field unit SAURON. We explore the dynamical structure of the stars and gas.

Is the giant elliptical galaxy NGC 5018 a post-merger remnant?

ASTRONOMY & ASTROPHYSICS 423 (2004) 965-968

LM Buson, F Bertola, A Bressan, D Burstein, M Cappellari