Publications by Michele Cappellari


The Kinematics of Core and Cusp Galaxies: Comparing HST Imaging and Integral-Field Observations

IMPACT OF HST ON EUROPEAN ASTRONOMY (2010) 127-+

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


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

Astrophysical Journal 719 (2010) 1481-1496

G Van De Ven, J Falcón-Barroso, RM McDermid, M Cappellari, BW Miller, PT De Zeeuw

We present two-dimensional line-of-sight stellar kinematics of the lens galaxy in the Einstein Cross, obtained with the GEMINI 8 m telescope, using the GMOS integral-field spectrograph. The stellar kinematics extend to a radius of 4″ (with 0.″2 spaxels), covering about two-thirds of the effective (or half-light) radius Re - 6″ of this early-type spiral galaxy at redshift zl ≃ 0.04, of which the bulge is lensing a background quasar at redshift zs ≃ 1.7. The velocity map shows regular rotation up to ∼100 km s-1 around the minor axis of the bulge, consistent with axisymmetry. The velocity dispersion map shows a weak gradient increasing toward a central (R < 1″) value of σ0 = 170 ± 9 km s-1. We deproject the observed surface brightness from Hubble Space Telescope 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 combine these independent constraints from stellar dynamics and gravitational lensing to study the total mass distribution in the inner parts of the lens galaxy. We find that the resulting luminous and total mass distribution are nearly identical around the Einstein radius Re = 0″.89, with a slope that is close to isothermal, but which becomes shallower toward the center if indeed mass follows light. The dynamical model fits to the observed kinematic maps result in a total mass-to-light ratio γdyn = 3.7 ± 0.5 γ⊙,I (in the I band). This is consistent with the Einstein mass Me = 1.54 × 1010 M⊙ divided by the (projected) luminosity within Re, which yields a total mass-to-light ratio of γE = 3.4 γ⊙,I, with an error of at most a few percent. We estimate from stellar population model fits to colors of the lens galaxy a stellar mass-to-light ratio γ* from 2.8 to 4.1 γ⊙,I. Although a constant dark matter fraction of 20% is not excluded, dark matter may play no significant role in the bulge of this ∼L* early-type spiral galaxy. © 2010. The American Astronomical Society.


Formation of slowly rotating early-type galaxies via major mergers: a resolution study

Monthly Notices of the Royal Astronomical Society 406 (2010) 2405-2420

M Bois, F Bournaud, E Emsellem, K Alatalo, L Blitz, M Bureau, M Cappellari, RL Davies, TA Davis, PT de Zeeuw, PA Duc, S Khochfar, D Krajnović, H Kuntschner, PY Lablanche, RM McDermid, R Morganti, T Naab, T Oosterloo, M Sarzi, N Scott, P Serra, A Weijmans, LM Young

We study resolution effects in numerical simulations of gas-rich and gas-poor major mergers, and show that the formation of slowly rotating elliptical galaxies often requires a resolution that is beyond the present-day standards to be properly modelled. Our sample of equal-mass merger models encompasses various masses and spatial resolutions, ranging from about 200 pc and 105 particles per component (stars, gas and dark matter), i.e. a gas mass resolution of ∼105 M⊙, typical of some recently published major merger simulations, to up to 32 pc and ∼103 M⊙ in simulations using 2.4 × 107 collisionless particles and 1.2 × 107 gas particles, among the highest resolutions reached so far for gas-rich major merger of massive disc galaxies. We find that the formation of fast-rotating early-type galaxies, that are flattened by a significant residual rotation, is overall correctly reproduced at all such resolutions. However, the formation of slow-rotating early-type galaxies, which have a low-residual angular momentum and are supported mostly by anisotropic velocity dispersions, is strongly resolution-dependent. The evacuation of angular momentum from the main stellar body is largely missed at standard resolution, and systems that should be slow rotators are then found to be fast rotators. The effect is most important for gas-rich mergers, but is also witnessed in mergers with an absent or modest gas component (0-10 per cent in mass). The effect is robust with respect to our initial conditions and interaction orbits, and originates in the physical treatment of the relaxation process during the coalescence of the galaxies. Our findings show that a high-enough resolution is required to accurately model the global properties of merger remnants and the evolution of their angular momentum. The role of gas-rich mergers of spiral galaxies in the formation of slow-rotating ellipticals may therefore have been underestimated. Moreover, the effect of gas in a galaxy merger is not limited to helping the survival/rebuilding of rotating disc components: at high resolution, gas actively participates in the relaxation process and the formation of slowly rotating stellar systems. © 2010 The Authors. Journal compilation © 2010 RAS.


A z=1.82 ANALOG OF LOCAL ULTRA-MASSIVE ELLIPTICAL GALAXIES

ASTROPHYSICAL JOURNAL LETTERS 715 (2010) L6-L11

M Onodera, E Daddi, R Gobat, M Cappellari, N Arimoto, A Renzini, Y Yamada, HJ McCracken, C Mancini, P Capak, M Carollo, A Cimatti, M Giavalisco, O Ilbert, X Kong, S Lilly, K Motohara, K Ohta, DB Sanders, N Scoville, N Tamura, Y Taniguchi


Testing mass determinations of supermassive black holes via stellar kinematics

AIP Conference Proceedings 1240 (2010) 211-214

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

We investigate the accuracy of mass determinations MBH of supermassive black holes in galaxies using dynamical models of the stellar kinematics. We compare 10 of our MBH measurements, using integral-field OASIS kinematics, to published values. For a sample of 25 galaxies we confront our new MBH derived using two modeling methods on the same OASIS data. © 2010 American Institute of Physics.


Measuring the Low Mass End of the M center dot - sigma Relation

HUNTING FOR THE DARK: THE HIDDEN SIDE OF GALAXY FORMATION 1240 (2010) 215-+

D Krajnovic, RM McDermid, M Cappellari, RL Davies


Nuclear star clusters &amp; black holes

AIP Conference Proceedings 1240 (2010) 227-230

A Seth, M Cappellari, N Neumayer, N Caldwell, N Bastian, K Olsen, R Blum, VP Debattista, R McDermid, T Puzia, A Stephens

We summarize the recent results of our survey of the nearest nuclear star clusters. The purpose of the survey is to understand nuclear star cluster formation mechanisms and constrain the presence of black holes using adaptive optics assisted integral field spectroscopy, optical spectroscopy, and HST imaging in 13 galaxies within 5 Mpc. We discuss the formation history of the nuclear star cluster and possible detection of an intermediate mass BH in NGC 404, the nearest S0 galaxy. © 2010 American Institute of Physics.


Structural and kinematical constraints on the formation of stellar nuclear clusters

AIP Conference Proceedings 1240 (2010) 243-244

M Hartmann, VP Debattista, A Seth, M Cappellari, T Quinn

We study the formation of stellar nuclear clusters (NC) with two types of N-body simulations: mergers of star clusters (SC) at the centre of disk galaxies and the accretion of a SC onto a previous NC. The merging of SCs produces systems consistent with observed scaling relations, they have shapes comparable with those observed and rotation consistent with that observed in the NCs of NGC 4244 and M 33. © 2010 American Institute of Physics.


The ATLAS<sup>3D</sup> project: A paradigm shift for early-type galaxies

AIP Conference Proceedings 1240 (2010) 335-338

E Emsellem, K Alatalo, L Blitz, M Bois, F Bournaud, M Bureau, M Cappellari, RL Davies, TA Davis, PT De Zeeuw, S Khochfar, D Krajnović, H Kuntschner, PY Lablanche, RM McDermid, R Morganti, T Naab, T Oosterloo, M Sarzi, N Scott, P Serra, A Weijmans, LM Young

In this short paper, we present a few preliminary results from the ambitious ATLAS3D project, which intends to probe the first volume-limited sample of early-type galaxies observed via multi-band photometry, integral-field spectroscopy, radio and millimeter observations, and supported by a large library of numerical simulations and models. We more specifically address the existence of two main families of early-type galaxies, the slow and fast rotators. © 2010 American Institute of Physics.


Formation of slowly rotating elliptical galaxies in major mergers. A resolution study

AIP Conference Proceedings 1240 (2010) 405-406

M Bois, F Bournaud, E Emsellem, K Alatalo, L Blitz, M Bureau, M Cappellari, RL Davies, TA Davis, PT De Zeeuw, J Falcón-Barroso, S Khochfar, D Krajnović, H Kuntschner, PY Lablanche, RM McDermid, R Morganti, T Naab, M Sarzi, N Scott, P Serra, RCE Van Den Bosch, G Van De Ven, A Weijmans, LM Young

We study resolution effects in numerical simulations of gas-rich (20% of the total baryonic mass) major mergers, and show that the formation of slowly-rotating elliptical galaxies requires a resolution that is beyond the present-day standards to be properly modelled. Our findings show that a high-enough resolution is required to accurately model the global properties of merger remnants and the evolution of their angular momentum. The role of wet mergers of spiral galaxies in the formation of slow-rotating ellipticals may therefore have been underestimated. © 2010 American Institute of Physics.


Dark matter and the Tully-Fisher relations of spiral and S0 galaxies

AIP Conference Proceedings 1240 (2010) 431-432

MJ Williams, M Bureau, M Cappellari

We construct mass models of 28 S0-Sb galaxies. The models have an axisymmetric stellar component and a NFW dark halo and are constrained by observed KS-band photometry and stellar kinematics. The median dark halo virial mass is 1012.8 M⊙, and the median dark/total mass fraction is 20% within a sphere of radius r1/2, the intrinsic half-light radius, and 50% within R25. We compare the Tully-Fisher relations of the spirals and S0s in the sample and find that S0s are 0.5 mag fainter than spirals at KS-band and 0.2 dex less massive for a given rotational velocity. We use this result to rule out scenarios in which spirals are transformed into S0s by processes which truncate star formation without affecting galaxy dynamics or structure, and raise the possibility of a break in homology between spirals and S0s. © 2010 American Institute of Physics.


Measuring the low mass end of the Mbh - sigma relation

(2010)

D Krajnovic, M Cappellari, RM McDermid, R Davies

We show that high quality laser guide star (LGS) adaptive optics (AO) observations of nearby early-type galaxies are possible when the tip-tilt correction is done by guiding on nuclei while the focus compensation due to the changing distance to the sodium layer is made 'open loop'. We achieve corrections such that 40% of flux comes from R&lt;0.2 arcsec. To measure a black hole mass (Mbh) one needs integral field observations of both high spatial resolution and large field of view. With these data it is possible to determine the lower limit to Mbh even if the spatial resolution of the observations are up to a few times larger than the sphere of influence of the black hole.


A z = 1.82 analog of local ultra-massive elliptical galaxies

Astrophysical Journal Letters 715 (2010)

M Onodera, E Daddi, R Gobat, M Cappellari, N Arimoto, A Renzini, Y Yamada, HJ McCracken, C Mancini, P Capak, M Carollo, A Cimatti, M Giavalisco, O Ilbert, X Kong, S Lilly, K Motohara, K Ohta, DB Sanders, N Scoville, N Tamura, Y Taniguchi

We present observations of a very massive galaxy at z = 1.82 that show that its morphology, size, velocity dispersion, and stellar population properties are fully consistent with those expected for passively evolving progenitors of today's giant ellipticals. These findings are based on a deep optical rest-frame spectrum obtained with the Multi-Object InfraRed Camera and Spectrograph on the Subaru Telescope of a high-z passive galaxy candidate (pBzK) from the COSMOS field, for which we accurately measure its redshift of z = 1.8230 and obtain an upper limit on its velocity dispersion σ* < 326 km s-1. By detailed stellar population modeling of both the galaxy broadband spectral energy distribution and the rest-frame optical spectrum, we derive a star formation-weighted age and formation redshift of tsf ≃ 1-2 Gyr and zform ≃ 2.5-4, and a stellar mass of M * ≃ (3-4) × 1011 M⊙. This is in agreement with a virial mass limit of Mvir < 7 × 1011 M⊙, derived from the measured σ* value and stellar half-light radius, as well as with the dynamical mass limit based on the Jeans equations. In contrast to previously reported super-dense passive galaxies at z ∼ 2, the present galaxy at z = 1.82 appears to have both size and velocity dispersion similar to early-type galaxies in the local universe with similar stellar mass. This suggests that z 2 massive and passive galaxies may exhibit a wide range of properties, then possibly following quite different evolutionary histories from z ∼ 2 to z = 0. © 2010 The American Astronomical Society. All rights reserved.


Early-type Galaxies in Isolation: an H I Perspective with ATLAS(3D)

GALAXIES IN ISOLATION: EXPLORING NATURE VERSUS NURTURE 421 (2010) 49-+

P Serra, R Morganti, TA Oosterloo, K Alatalo, L Blitz, M Bois, RCE van den Bosch, F Bournaud, M Bureau, M Cappellari, RL Davies, TA Davis, P Duc, E Emsellem, J Falcon-Barroso, S Khochfar, D Krajnovic, H Kuntschner, PY Lablanche, RM McDermid, T Naab, M Sarzi, N Scott, G van de Ven, A Weijmans, LM Young, PT de Zeeuw


Weighing black holes using open-loop focus corrections for LGS-AO observations of galaxy nuclei at Gemini Observatory

ADAPTIVE OPTICS SYSTEMS II 7736 (2010) UNSP 77365W

RM McDermid, D Krajnovic, M Cappellari, C Trujillo, J Christou, RL Davies


The NGC 404 nucleus: Star cluster and possible intermediate-mass black hole

Astrophysical Journal 714 (2010) 713-731

AC Seth, M Cappellari, N Neumayer, N Caldwell, N Bastian, K Olsen, RD Blum, VP Debattista, R McDermid, T Puzia, A Stephens

We examine the nuclear morphology, kinematics, and stellar populations in nearby S0 galaxy NGC 404 using a combination of adaptive optics assisted near-IR integral-field spectroscopy, optical spectroscopy, and Hubble Space Telescope imaging. These observations enable study of the NGC 404 nucleus at a level of detail possible only in the nearest galaxies. The surface brightness profile suggests the presence of three components: a bulge, a nuclear star cluster (NSC), and a central light excess within the cluster at radii < 3 pc. These components have distinct kinematics with modest rotation seen in the NSC and counter-rotation seen in the central excess. Molecular hydrogen emission traces a disk with rotation nearly orthogonal to that of the stars. The stellar populations of the three components are also distinct, with half of the mass of the NSC having ages of ∼ 1 Gyr (perhaps resulting from a galaxy merger), while the bulge is dominated by much older stars. Dynamical modeling of the stellar kinematics gives a total NSC mass of 1.1 × 107 M ⊙. Dynamical detection of a possible intermediate-mass black hole (BH) is hindered by uncertainties in the central stellar mass profile. Assuming a constant mass-to-light ratio, the stellar dynamical modeling suggests a BH mass of <1 × 105 M ⊙, while the molecular hydrogen gas kinematics are best fitted by a BH with a mass of 4.5+3.5-2.0 × 105 M ⊙. Unresolved and possibly variable dust emission in the near-infrared and active galactic nucleus-like molecular hydrogen emission-line ratios do suggest the presence of an accreting BH in this nearby LINER galaxy. © 2010. The American Astronomical Society. All rights reserved.


Scaling relations in early-type galaxies from integral-field stellar kinematics

HIGHLIGHTS OF ASTRONOMY, VOL 15 15 (2010) 81-81

M Cappellari, N Scott, K Alatalo, L Blitz, M Bois, F Bournaud, M Bureau, RL Davies, TA Davis, PT de Zeeuw, E Emsellem, J Falcon-Barroso, S Khochfar, D Krajnovic, H Kuntschner, P-Y Lablanche, RM McDermid, R Morganti, T Naab, M Sarzi, P Serra, RCE van den Bosch, G van de Ven, A Weijmansm, LM Young


Lenticular vs spiral galaxies: dark matter content and the Tully-Fisher relation

HIGHLIGHTS OF ASTRONOMY, VOL 15 15 (2010) 82-82

M Bureau, MJ Williams, M Cappellari


The SAURON project - XVI. On the sources of ionization for the gas in elliptical and lenticular galaxies

Monthly Notices of the Royal Astronomical Society 402 (2010) 2187-2210

M Sarzi, JC Shields, K Schawinski, H Jeong, K Shapiro, R Bacon, M Bureau, M Cappellari, RL Davies, P Tim de Zeeuw, E Emsellem, J Falcón-Barroso, D Krajnović, H Kuntschner, RM McDermid, RF Peletier, RCE van den Bosch, G van de Ven, SK Yi

Following our study on the incidence, morphology and kinematics of the ionized gas in early-type galaxies, we now address the question of what is powering the observed nebular emission. To constrain the likely sources of gas excitation, we resort to a variety of ancillary data we draw from complementary information on the gas kinematics, stellar populations and galactic potential from the sauron data, and use the sauron-specific diagnostic diagram juxtaposing the [O iii]λ5007/Hβ and [N i]λλ5197, 5200/Hβ line ratios. We find a tight correlation between the stellar surface brightness and the flux of the Hβ recombination line across our sample, which points to a diffuse and old stellar source as the main contributor of ionizing photons in early-type galaxies, with post-asymptotic giant branch (pAGB) stars being still the best candidate based on ionizing balance arguments. The role of AGN photoionization is confined to the central 2-3 arcsec of an handful of objects with radio or X-ray cores. OB-stars are the dominant source of photoionization in 10 per cent of the sauron sample, whereas for another 10 per cent the intense and highly ionized emission is powered by the pAGB population associated to a recently formed stellar subcomponent. Fast shocks are not an important source of ionization for the diffuse nebular emission of early-type galaxies since the required shock velocities can hardly be attained in the potential of our sample galaxies. Finally, in the most massive and slowly or non-rotating galaxies in our sample, which can retain a massive X-ray halo, the finding of a spatial correlation between the hot and warm phases of the interstellar medium (ISM) suggests that the interaction with the hot ISM provides an additional source of ionization besides old ultraviolet-bright stars. This is also supported by a distinct pattern towards lower values of the [O iii]/Hβ ratio. These results lead us to investigate the relative role of stellar and AGN photoionization in explaining the ionized gas emission observed in early-type galaxies by the Sloan Digital Sky Survey (SDSS). By simulating how our sample galaxies would appear if placed at further distance and targeted by the SDSS, we conclude that only in very few, if any, of the SDSS galaxies which display modest values for the equivalent width of the [O iii] line (less than ∼2.4 Å) and low-ionization nuclear emission-line region like [O iii]/Hβ values the nebular emission is truly powered by an AGN. © 2010 The Authors. Journal compilation © 2010 RAS.


Measuring the low mass end of the M<inf>•</inf> - σ relation

AIP Conference Proceedings 1240 (2010) 215-218

D Krajnović, RM McDermid, M Cappellari, RL Davies

We show that high quality laser guide star (LGS) adaptive optics (AO) observations of nearby early-type galaxies are possible when the tip-tilt correction is done by guiding on nuclei while the focus compensation due to the changing distance to the sodium layer is made 'open loop'. We achieve corrections such that 40% of flux comes from R<0.2 arcsec. To measure a black hole mass (M•) one needs integral field observations of both high spatial resolution and large field of view. With these data it is possible to determine the lower limit to M• even if the spatial resolution of the observations are up to a few times larger than the sphere of influence of the black hole. © 2010 American Institute of Physics.

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