Publications by Michele Cappellari

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


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

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


D Krajnovic, RM McDermid, M Cappellari, RL Davies

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.

Measuring the low mass end of the Mbh - sigma relation


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.

Searching for the Supermassive Black Hole in NGC 1265 (3C 83.1B)


A Beifiori, M Sarzi, RL Davies, M Cappellari, RCW Houghton

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)


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


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


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


M Bureau, MJ Williams, M Cappellari

The SAURON project - XV. Modes of star formation in early-type galaxies and the evolution of the red sequence

Monthly Notices of the Royal Astronomical Society 402 (2010) 2140-2186

KL Shapiro, J Falcón-Barroso, G van de Ven, P Tim de Zeeuw, M Sarzi, R Bacon, A Bolatto, M Cappellari, D Croton, RL Davies, E Emsellem, O Fakhouri, D Krajnović, H Kuntschner, RM McDermid, RF Peletier, RCE van den Bosch, G van der Wolk

We combine SAURON integral field data of a representative sample of local early-type, red sequence galaxies with Spitzer/Infrared Array Camera imaging in order to investigate the presence of trace star formation in these systems. With the Spitzer data, we identify galaxies hosting low-level star formation, as traced by polycyclic aromatic hydrocarbon emission, with measured star formation rates that compare well to those estimated from other tracers. This star formation proceeds according to established scaling relations with molecular gas content, in surface density regimes characteristic of disc galaxies and circumnuclear starbursts. We find that star formation in early-type galaxies happens exclusively in fast-rotating systems and occurs in two distinct modes. In the first, star formation is a diffuse process, corresponding to widespread young stellar populations and high molecular gas content. The equal presence of co- and counter-rotating components in these systems strongly implies an external origin for the star-forming gas, and we argue that these star formation events may be the final stages of (mostly minor) mergers that build up the bulges of red sequence lenticulars. In the second mode of star formation, the process is concentrated into well-defined disc or ring morphologies, outside of which the host galaxies exhibit uniformly evolved stellar populations. This implies that these star formation events represent rejuvenations within previously quiescent stellar systems. Evidence for earlier star formation events similar to these in all fast-rotating early-type galaxies suggests that this mode of star formation may be common to all such galaxies, with a duty cycle of roughly 1/10, and likely contributes to the embedded, corotating inner stellar discs ubiquitous in this population. © 2010 The Authors. Journal compilation © 2010 RAS.

Determination of masses of the central black holes in NGC 524 and 2549 using laser guide star adaptive optics

Monthly Notices of the Royal Astronomical Society 399 (2009) 1839-1857

D Krajnović, RM McDermid, M Cappellari, RL Davies

We present observations of early-type galaxies NGC 524 and 2549 with laser guide star adaptive optics (LGS AO) obtained at GEMINI North telescope using the Near-infrared Integral Field Spectrograph (NIFS) integral field unit (IFU) in the K band. The purpose of these observations is to determine high spatial resolution stellar kinematics within the nuclei of these galaxies and, in combination with previously obtained large-scale observations with the SAURON IFU, to determine the masses (M•) of the supermassive black holes (SMBH). The targeted galaxies were chosen to have central light profiles showing a core (NGC 524) and a cusp (NGC 2549), to probe the feasibility of using the galaxy centre as the natural guide source required for LGS AO. We employ an innovative technique where the focus compensation due to the changing distance to the sodium layer is made 'open loop', allowing the extended galaxy nucleus to be used only for tip-tilt correction. The data have spatial resolution of 0.23 and 0.17 arcsec full-width at half maximum (FWHM), where at least ∼40 per cent of flux comes within 0.2, showing that high quality LGS AO observations of these objects are possible. The achieved signal-to-noise ratio (S/N ∼ 50) is sufficiently high to reliably determine the shape of the line-of-sight velocity distribution. We construct axisymmetric three-integral dynamical models which are constrained with both the NIFS and SAURON data. The best-fitting models yield M• = (8.3+2.7-1.3) × 108 M⊙ and (M/L)I = 5.8 ± 0.4 for NGC 524 and M• = (1.4 +0.2-1.3) × 107 M⊙ and (M/L)R = 4.7 ± 0.2 for NGC 2549 (all errors are at the 3σ level). We demonstrate that the wide-field SAURON data play a crucial role in the M/L determination increasing the accuracy of M/L by a factor of at least 5, and constraining the upper limits on black hole masses. The NIFS data are crucial in constraining the lower limits of M• and in combination with the large-scale data reducing the uncertainty by a factor of 2 or more. We find that the orbital structure of NGC 524 shows significant tangential anisotropy, while at larger radii both galaxies are consistent with having almost perfectly oblate velocity ellipsoids. Tangential anisotropy in NGC 524 coincides with the size of SMBH sphere of influence and the core region in the light profile. This agrees with predictions from numerical simulations where core profiles are the result of SMBH binaries evacuating the centre nuclear regions following a galaxy merger. However, being a disc dominated fast rotating galaxy, NGC 524 has probably undergone through a more complex evolution. We test the accuracy to which M• can be measured using seeings obtained from typical LGS AO observations, and conclude that for a typical conditions and M• the expected uncertainty is of the order of 50 per cent. © 2009 RAS.



M Cappellari, SDS Alighieri, A Cimatti, E Daddi, A Renzini, JD Kurk, P Cassata, M Dickinson, A Franceschini, M Mignoli, L Pozzetti, G Rodighiero, P Rosati, G Zamorani

The SAURON Project - XIV. No escape from V<inf>esc</inf>: A global and local parameter in early-type galaxy evolution

Monthly Notices of the Royal Astronomical Society 398 (2009) 1835-1857

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

We present the results of an investigation of the local escape velocity (Vesc) - line strength index relationship for 48 early-type galaxies from the SAURON sample, the first such study based on a large sample of galaxies with both detailed integral field observations and extensive dynamical modelling. Values of Vesc are computed using multi-Gaussian expansion (MGE) photometric fitting and axisymmetric, anisotropic Jeans' dynamical modelling simultaneously on Hubble Space Telescope and ground-based images. We determine line strengths and escape velocities at multiple radii within each galaxy, allowing an investigation of the correlation within individual galaxies as well as amongst galaxies. We find a tight correlation between Vesc and the line-strength indices. For Mgb, we find that this correlation exists not only between different galaxies but also inside individual galaxies - it is both a local and global correlation. The Mgb-Vesc relation has the form: log(Mgb/4 Å) = (0.32 ± 0.03) log(Vesc/500 km s-1) - (0.031 ± 0.007) with an rms scatter σ = 0.033. The relation within individual galaxies has the same slope and offset as the global relation to a good level of agreement, though there is significant intrinsic scatter in the local gradients. We transform our line strength index measurements to the single stellar population (SSP) equivalent ages (t), metallicity ([Z/H]) and enhancement ([α/Fe]) and carry out a principal component analysis of our SSP and Vesc data. We find that in this four-dimensional parameter space the galaxies in our sample are to a good approximation confined to a plane, given by log (V esc/500 km s -1) = 0.85 [Z/H] + 0.43 log (t/Gyr) - 0.29. It is surprising that a combination of age and metallicity is conserved; this may indicate a 'conspiracy' between age and metallicity or a weakness in the SSP models. How the connection between stellar populations and the gravitational potential, both locally and globally, is preserved as galaxies assemble hierarchically may provide an important constraint on modelling. © 2009 RAS.

Stellar populations of early-type galaxies in the ATLAS<sup>3D</sup> sample

AIP Conference Proceedings 1111 (2009) 111-114

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

ATLAS3D is a multi-wavelength, volume-limited survey of 263 morphologicallyselected early-type galaxies within a distance of 42 Mpc and complete to MK ≤ -21.5. Here we present the ATLAS3D project and our first results on the stellar populations of galaxies in the ATLAS3Dsample based on SAURON integral-field spectroscopy. We show relations between integrated line-strength indices and stellar velocity dispersion o in the range 55 ≤ Σ(km/s) ≤ 350. We derive simple-stellar-population-equivalent age, metallicity and α/Fe abundance ratio and discuss their relation to stellar velocity dispersion, environment and galaxy internal kinematics. These preliminary results indicate that slow rotators tend to be older and have less variation in age than fast rotators. We also find that galaxies in lower density environments are on average younger than those in denser environments, as found by other authors. © 2009 American Institute of Physics.

Kinematic constraints on the stellar and dark matter content of spiral and S0 galaxies

Monthly Notices of the Royal Astronomical Society 400 (2009) 1665-1689

MJ Williams, M Bureau, M Cappellari

We present mass models of a sample of 14 spiral and 14 S0 galaxies that constrain their stellar and dark matter content. For each galaxy, we derive the stellar mass distribution from near-infrared photometry under the assumptions of axisymmetry and a constant KS-band stellar mass-to-light ratio. To this we add a dark halo assumed to follow a spherically symmetric Navarro, Frenk and White profile and a correlation between concentration and dark mass within the virial radius, MDM. We solve the Jeans equations for the corresponding potential under the assumption of constant anisotropy in the meridional plane, βz. By comparing the predicted second velocity moment to observed long-slit stellar kinematics, we determine the three best-fitting parameters of the model: and βz. These simple axisymmetric Jeans models are able to accurately reproduce the wide range of observed stellar kinematics, which typically extend to ≈2-3Re or, equivalently, ≈0.5-1R25. Although our sample contains barred galaxies, we argue a posteriori that the assumption of axisymmetry does not significantly bias our results. We find a median stellar mass-to-light ratio at KS-band of with an rms scatter of 0.31. We present preliminary comparisons between this large sample of dynamically determined stellar mass-to-light ratios and the predictions of stellar population models. The stellar population models predict slightly lower mass-to-light ratios than we measure. The mass models contain a median of 15 per cent dark matter by mass within an effective radius Re (defined here as the semimajor axis of the ellipse containing half the KS-band light) and 49 per cent within the optical radius R25. Dark and stellar matter contribute equally to the mass within a sphere of radius 4.1Re or 1.0 R25. There is no evidence of any significant difference in the dark matter content of the spirals and S0s in our sample. Models without dark matter are also able to satisfactorily reproduce the observed kinematics in most cases. The improvement when a halo is added is statistically significant, however, and the stellar mass-to-light ratios of mass models with dark haloes match the independent expectations of stellar population models better. © 2009 RAS.

Stellar velocity profiles and line strengths out to four effective radii in the early-type galaxies NGC 3379 and 821

Monthly Notices of the Royal Astronomical Society 398 (2009) 561-574

AM Weijmans, M Cappellari, R Bacon, PT De Zeeuw, E Emsellem, J Falcón-Barroso, H Kuntschner, RM McDermid, RCE Van Den Bosch, G Van De Ven

We use the integral-field spectrograph SAURON to measure the stellar line-of-sight velocity distribution and absorption line strengths out to four effective radii (Re) in the early-type galaxies NGC 3379 and 821. With our newly developed observing technique, we can now probe these faint regions in galaxies that were previously not accessible with traditional long-slit spectroscopy. We make optimal use of the large field-of-view and high throughput of the spectrograph: by adding the signal of all ∼1400 lenslets into one spectrum, we obtain sufficient signal-to-noise in a few hours of observing time to reliably measure the absorption line kinematics and line strengths out to large radius. We find that the line strength gradients previously observed within 1 Re remain constant out to at least 4 Re, which puts constraints on the merger histories of these galaxies. The stellar halo populations are old and metal poor. By constructing orbit-based Schwarzschild dynamical models, we find that dark matter is necessary to explain the observed kinematics in NGC 3379 and 821, with 30-50 per cent of the total matter being dark within 4 Re. The radial anisotropy in our best-fitting halo models is less than in our models without halo, due to differences in orbital structure. The halo also has an effect on the Mg b-Vesc relation: its slope is steeper when a dark matter halo is added to the model. © 2009 RAS.

Specific angular momentum of disc merger remnants and the λ <inf>r</inf> -parameter

Monthly Notices of the Royal Astronomical Society 397 (2009) 1202-1214

R Jesseit, M Cappellari, T Naab, E Emsellem, A Burkert

We use two-dimensional kinematic maps of simulated binary disc mergers to investigate the λ R -parameter, which is a luminosity-weighted measure of projected angular momentum per unit mass. This parameter was introduced to subdivide the SAURON sample of early-type galaxies in so-called fast λ R > 0.1 and slow rotators λ R < 0.1. Tests on merger remnants reveal that λ R is a robust indicator of the true angular momentum content in elliptical galaxies. We find the same range of λ R values in our merger remnants as in the SAURON galaxies. The merger mass ratio is decisive in transforming fast rotators into slow rotators in a single binary merger, the latter being created mostly in an equal-mass merger. Slow rotators have a λ R which does not vary with projection. The confusion rate with face-on fast rotators is very small. Mergers with a gas component form slow rotators with smaller ellipticities than collisionless merger remnants have, and are in much better agreement with the SAURON slow rotators. Remergers of merger remnants are slow rotators, but tend to have too high ellipticities. Fast rotators maintain the angular momentum content from the progenitor disc galaxy if merger mass ratio is high. Some SAURON galaxies have values of λ R as high as our progenitor disc galaxies. © 2009 RAS.