Publications by Michele Cappellari


Kinematics of superdense galaxies in clusters

GALAXIES IN 3D ACROSS THE UNIVERSE 10 (2014) 219-220

A Moretti, B Poggianti, D Bettoni, M Cappellari, G Fasano, WINGS Team


NGC 1266 as a local candidate for rapid cessation of star formation

Astrophysical Journal 780 (2014)

K Alatalo, K Nyland, G Graves, S Deustua, KS Griffin, PA Duc, M Cappellari, RM McDermid, TA Davis, AF Crocker, LM Young, P Chang, N Scott, SL Cales, E Bayet, L Blitz, M Bois, F Bournaud, M Bureau, RL Davies, PT De Zeeuw, E Emsellem, S Khochfar, D Krajnović, H Kuntschner, R Morganti, T Naab, T Oosterloo, M Sarzi, P Serra, AM Weijmans

We present new Spectrographic Areal Unit for Research on Optical Nebulae (SAURON) integral-field spectroscopy and Swift Ultraviolet Optical Telescope (UVOT) observations of molecular outflow host galaxy NGC 1266 that indicate NGC 1266 has experienced a rapid cessation of star formation. Both the SAURON maps of stellar population age and the Swift UVOT observations demonstrate the presence of young (<1 Gyr) stellar populations within the central 1 kpc, while existing Combined Array for Research in Millimeter-Wave Astronomy CO(1-0) maps indicate that the sites of current star formation are constrained to only the inner few hundred parsecs of the galaxy. The optical spectrum of NGC 1266 from Moustakas & Kennicutt reveal a characteristic poststarburst (K+A) stellar population, and Davis et al. confirm that ionized gas emission in the system originate from a shock. Galaxies with K+A spectra and shock-like ionized gas line ratios may comprise an important, overlooked segment of the poststarburst population, containing exactly those objects in which the active galactic nucleus (AGN) is actively expelling the star-forming material. While AGN activity is not the likely driver of the poststarburst event that occurred 500 Myr ago, the faint spiral structure seen in the Hubble Space Telescope Wide-field Camera 3 Y-, J- and H-band imaging seems to point to the possibility of gravitational torques being the culprit. If the molecular gas were driven into the center at the same time as the larger scale galaxy disk underwent quenching, the AGN might be able to sustain the presence of molecular gas for ≳ 1 Gyr by cyclically injecting turbulent energy into the dense molecular gas via a radio jet, inhibiting star formation. © 2014. The American Astronomical Society. All rights reserved.


Galaxy masses

REVIEWS OF MODERN PHYSICS 86 (2014) 47-119

S Courteau, M Cappellari, RS de Jong, AA Dutton, E Emsellem, H Hoekstra, LVE Koopmans, GA Mamon, C Maraston, T Treu, LM Widrow


KMOS Clusters and VIRIAL GTO Surveys

GALAXIES IN 3D ACROSS THE UNIVERSE 10 (2014) 293-294

D Wilman, R Bender, RL Davies, JT Mendel, J Chan, A Beifiori, R Houghton, R Saglia, NF Schreiber, S Wuyts, P van Dokkum, M Cappellari, J Stott, R Smith, M Fossati, S Kulkarni, S Seitz, M Fabricius, R Sharples, G Brammer, E Nelson, I Momcheva, M Wegner, I Lewis


Chronos: a NIR spectroscopic galaxy survey. From the formation of Galaxies to the peak of activity

Cosmic Vision ESA (2013)

I Ferreras, R Sharples, JS Dunlop, A Pasquali, FL Barbera, A Vazdekis, S Khochfar, M Cropper, M Cirasuolo, A Cimatti, R Bower, J Brinchmann, M Cappellari, B Burningham, S Charlot, CJ Conselice, E Daddi, EK Grebel, R Ivison, MJ Jarvis, D Kawata, RC Kennicutt, T Kitching, O Lahav, R Maiolino

<p style="text-align:justify;"> Chronos is our response to ESA's call for white papers to define the science for the future L2, L3 missions. Chronos targets the formation and evolution of galaxies, by collecting the deepest NIR spectroscopic data, from the formation of the first galaxies at z~10 to the peak of formation activity at z~1-3. The strong emission from the atmospheric background makes this type of survey impossible from a ground-based observatory. The spectra of galaxies represent the equivalent of a DNA fingerprint, containing information about the past history of star formation and chemical enrichment. The proposed survey will allow us to dissect the formation process of galaxies including the timescales of quenching triggered by star formation or AGN activity, the effect of environment, the role of infall/outflow processes, or the connection between the galaxies and their underlying dark matter haloes. To provide these data, the mission requires a 2.5m space telescope optimised for a campaign of very deep NIR spectroscopy. A combination of a high multiplex and very long integration times will result in the deepest, largest, high-quality spectroscopic dataset of galaxies from z=1 to 12, spanning the history of the Universe, from 400 million to 6 billion years after the big bang, i.e. covering the most active half of cosmic history. </p>


The ATLAS<sup>3D</sup> Project - XXIII. Angular momentum and nuclear surface brightness profiles

Monthly Notices of the Royal Astronomical Society 433 (2013) 2812-2839

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

We investigate nuclear light profiles in 135 ATLAS3D galaxies for which the Hubble Space Telescope (HST) imaging is available and compare them to the large-scale kinematics obtained with the SAURONintegral-field spectrograph. Specific angular momentum, λR, correlateswith the shape of nuclear light profiles, where, as suggested by previous studies, cores are typically found in slow rotators and core-less galaxies are fast rotators. As also shown before, cores are found only in massive galaxies and only in systems with the stellar mass (measured via dynamical models) M ≳ 8 × 1010 M· Based on our sample, we, however, see no evidence for a bimodal distribution of nuclear slopes. The best predictor for finding a core is based on the stellar velocity dispersion within an effective radius, se, and specific angular momentum, where cores are found for λR ≲ 0.25 and σe ≳ 160 kms-1. We estimate that only about 10 per cent of nearby early-type galaxies contain cores. Furthermore, we show that there is a genuine population of fast rotators with cores. We also show that core fast rotators are morphologically, kinematically and dynamically different from core slow rotators. The cores of fast rotators, however, could harbour black holes of similar masses to those in core slow rotators, but typically more massive than those found in core-less fast rotators. Cores of both fast and slow rotators are made of old stars and found in galaxies typically lacking molecular or atomic gas (with a few exceptions). Core-less galaxies, and especially core-less fast rotators, are underluminous in the diffuse X-ray emission, but the presence of a core does not imply high X-ray luminosities. Additionally, we postulate (as many of these galaxies lack HST imaging) a possible population of core-less galaxies among slow rotators, which cannot be explained as face-on discs, but comprise a genuine sub-population of slow rotators. These galaxies are typically less massive and flatter than core slow rotators, and show evidence for dynamical cold structures and exponential photometric components. Based on our findings, major nondissipative (gas-poor) mergers together with black hole binary evolution may not be the only path for formation of cores in early-type galaxies. We discuss possible processes for formation of cores and their subsequent preservation. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


The ATLAS<sup>3D</sup> project - XVIII. CARMA CO imaging survey of early-type galaxies

Monthly Notices of the Royal Astronomical Society 432 (2013) 1796-1844

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

We present the Combined Array for Research in Millimeter Astronomy (CARMA) ATLAS3D molecular gas imaging survey, a systematic study of the distribution and kinematics of molecular gas in CO-rich early-type galaxies. Our full sample of 40 galaxies (30 newly mapped and 10 taken from the literature) is complete to a 12CO(1-0) integrated flux of 18.5 Jy km s-1,1 and it represents the largest, best studied sample of its type to date. A comparison of the CO distribution of each galaxy to the g - r colour image (representing dust) shows that the molecular gas and dust distributions are in good agreement and trace the same underlying interstellar medium. The galaxies exhibit a variety of CO morphologies, including discs (50 per cent), rings (15 per cent), bars+rings (10 per cent), spiral arms (5 per cent) and mildly (12.5 per cent) and strongly (7.5 per cent) disrupted morphologies. There appear to be weak trends between galaxy mass and CO morphology, whereby the most massive galaxies in the sample tend to have molecular gas in a disc morphology. We derive a lower limit to the total accreted molecular gas mass across the sample of 2.48 × 1010Mȯ, or approximately 8.3 × 108Mȯ per minor merger within the sample, consistent with minor merger stellar mass ratios. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


The ATLAS<sup>3D</sup> project - XVI. Physical parameters and spectral line energy distributions of the molecular gas in gas-rich early-type galaxies

Monthly Notices of the Royal Astronomical Society 432 (2013) 1742-1767

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

We present a detailed study of the physical properties of the molecular gas in a sample of 18 molecular gas-rich early-type galaxies (ETGs) from the ATLAS3D sample. Our goal is to better understand the star formation processes occurring in those galaxies, starting here with the dense star-forming gas. We use existing integrated 12CO (1-0, 2-1), 13CO (1-0, 2-1), HCN (1-0) and HCO+ (1-0) observations and new 12 CO (3-2) single-dish data. From these, we derive for the first time the average kinetic temperature, H2 volume density and column density of the emitting gas in a significant sample of ETGs, using a non-local thermodynamical equilibrium theoretical model. Since the CO lines trace different physical conditions than of those the HCN and HCO+ lines, the two sets of lines are treated separately. For most of the molecular gas-rich ETGs studied here, the CO transitions can be reproduced with kinetic temperatures of 10-20 K, H2 volume densities of 103-4 cm-3 and CO column densities of 1018-20 cm-2. The physical conditions corresponding to the HCN and HCO+ gas component have large uncertainties and must be considered as indicative only. We also compare for the first time the predicted CO spectral line energy distributions and gas properties of our molecular gas-rich ETGs with those of a sample of nearby well-studied disc galaxies. The gas excitation conditions in 13 of our 18 ETGs appear analogous to those in the centre of theMilky Way, hence the star formation activity driving these conditions is likely of a similar strength and nature. Such results have never been obtained before for ETGs and open a new window to explore further star-formation processes in the Universe. The conclusions drawn should nevertheless be considered carefully, as they are based on a limited number of observations and on a simple model. In the near future, with higher CO transition observations, it should be possible to better identify the various gas components present in ETGs, as well as more precisely determine their associated physical conditions. To achieve these goals, we show here from our theoretical study, that mid-J CO lines [such as the 12CO (6-5) line] are particularly useful. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


Effect of environment on galaxies mass-size distribution: unveiling the transition from outside-in to inside-out evolution

The Astrophysical Journal Letters (2013)

M Cappellari


The atlas3d project - xiv. the extent and kinematics of the molecular gas in early-type galaxies

Monthly Notices of the Royal Astronomical Society 429 (2013) 534-555

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

We use interferometric 12CO(1-0) observations to compare and contrast the extent, surface brightness profiles and kinematics of the molecular gas in CO-rich ATLAS3D early-type galaxies (ETGs) and spiral galaxies. We find that the molecular gas extent is smaller in absolute terms in ETGs than in late-type galaxies, but that the size distributions are similar once scaled by the galaxies optical/stellar characteristic scalelengths. Amongst ETGs, we find that the extent of the gas is independent of its kinematic misalignment (with respect to the stars), but does depend on the environment, with Virgo cluster ETGs having less extended molecular gas reservoirs, further emphasizing that cluster ETGs follow different evolutionary pathways from those in the field. Approximately half of ETGs have molecular gas surface brightness profiles that follow the stellar light profile. These systems often have relaxed gas out to large radii, suggesting they are unlikely to have had recent merger/accretion events. A third of the sample galaxies show molecular gas surface brightness profiles that fall off slower than the light, and sometimes show a truncation. These galaxies often have a low mass, and eitherhave disturbed molecular gas or are in the Virgo cluster, suggesting that recent mergers, ram pressure stripping and/or the presence of hot gas can compress/truncate the gas. The remaining galaxies have rings, or composite profiles, that we argue can be caused by the effects of bars. We investigated the kinematics of the molecular gas using position-velocity diagrams, and compared the observed kinematics with dynamical model predictions, and the observed stellar and ionized gas velocities. We confirm that the molecular gas reaches beyond the turnover of the circular velocity curve in~70 per cent of our CO-rich ATLAS3D ETGs, validating previous work on the CO Tully-Fisher relation. In general we find that in most galaxies the molecular gas is dynamically cold, and the observed CO rotation matches well model predictions of the circular velocity. In the galaxies with the largest molecular masses, dust obscuration and/or population gradients can cause model predictions of the circular velocity to disagree with observations of the molecular gas rotation; however, these effects are confined to the most star forming systems. Bars and non-equilibrium conditions can also make the gas deviate from circular orbits. In both these cases, one expects the model circular velocity to be higher than the observed CO velocity, in agreement with our observations. Molecular gas is a better direct tracer of the circular velocity than the ionized gas, justifying its use as a kinematic tracer for Tully-Fisher and similar analyses.


A black-hole mass measurement from molecular gas kinematics in NGC4526

Nature 494 (2013) 328-330

TA Davis, M Bureau, M Cappellari, M Sarzi, L Blitz

The masses of the supermassive black holes found in galaxy bulges are correlated with a multitude of galaxy properties, leading to suggestions that galaxies and black holes may evolve together. The number of reliably measured black-hole masses is small, and the number of methods for measuring them is limited, holding back attempts to understand this co-evolution. Directly measuring black-hole masses is currently possible with stellar kinematics (in early-type galaxies), ionized-gas kinematics (in some spiral and early-type galaxies) and in rare objects that have central maser emission. Here we report that by modelling the effect of a black hole on the kinematics of molecular gas it is possible to fit interferometric observations of CO emission and thereby accurately estimate black-hole masses. We study the dynamics of the gas in the early-type galaxy NGC 4526, and obtain a best fit that requires the presence of a central dark object of× 10 8 solar masses (3σ confidence limit). With the next-generation millimetre-wavelength interferometers these observations could be reproduced in galaxies out to 75 megaparsecs in less than 5 hours of observing time. The use of molecular gas as a kinematic tracer should thus allow one to estimate black-hole masses in hundreds of galaxies in the local Universe, many more than are accessible with current techniques. © 2013 Macmillan Publishers Limited. All rights reserved.


Disentangling the stellar populations in the counter-rotating disc galaxy NGC 4550

Monthly Notices of the Royal Astronomical Society 428 (2013) 1296-1302

EJ Johnston, MR Merrifield, A Araǵon-Salamanca, M Cappellari

In order to try and understand its origins, we present high-quality long-slit spectral observations of the counter-rotating stellar discs in the strange S0 galaxy NGC 4550. We kinematically decompose the spectra into two counter-rotating stellar components (plus a gaseous component), in order to study both their kinematics and their populations. The derived kinematics largely confirm what was known previously about the stellar discs, but trace them to larger radii with smaller errors; the fitted gaseous component allows us to trace the hydrogen emission lines for the first time, which are found to follow the same rather strange kinematics previously seen in the [OIII] line. Analysis of the populations of the two separate stellar components shows that the secondary disc has a significantly younger mean age than the primary disc, consistent with later star formation from the associated gaseous material. In addition, the secondary disc is somewhat brighter, also consistent with such additional star formation. However, these measurements cannot be self-consistently modelled by a scenario in which extra stars have been added to initially identical counter-rotating stellar discs, which rules out the Evans & Collett's elegant 'separatrix-crossing' model for the formation of such massive counter-rotating discs from a single galaxy, leaving some form of unusual gas accretion history as the most likely formation mechanism. © 2012 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


Simulations of Binary Galaxy Mergers and the Link with Fast Rotators, Slow Rotators, and Kinematically Distinct Cores

GALAXY MERGERS IN AN EVOLVING UNIVERSE 477 (2013) 97-+

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


The ATLAS<sup>3D</sup> project - XV. Benchmark for early-type galaxies scaling relations from 260 dynamical models: Mass-to-light ratio, dark matter, fundamental plane and mass plane

Monthly Notices of the Royal Astronomical Society 432 (2013) 1709-1741

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

We study the volume-limited and nearly mass-selected (stellar mass Mstars ≳ 6 × 109 M⊙) ATLAS3D sample of 260 early-type galaxies (ETGs, ellipticals Es and lenticulars S0s). We construct detailed axisymmetric dynamical models (Jeans Anisotropic MGE), which allow for orbital anisotropy, include a dark matter halo and reproduce in detail both the galaxy images and the high-quality integral-field stellar kinematics out to about 1Re, the projected half-light radius. We derive accurate total mass-to-light ratios (M/L)e and dark matter fractions fDM, within a sphere of radius r = Re centred on the galaxies.We alsomeasure the stellar (M/L)stars and derive a median dark matter fraction fDM = 13 per cent in our sample. We infer masses MJAM = L × (M/L)e ≈ 2 ×M1/2, where M1/2 is the total mass within a sphere enclosing half of the galaxy light. We find that the thin two-dimensional subset spanned by galaxies in the (MJAM, σe,Rmaje ) coordinates system, which we call the Mass Plane (MP) has an observed rms scatter of 19 per cent, which implies an intrinsic one of 11 per cent. Here, Rmaje is the major axis of an isophote enclosing half of the observed galaxy light, while σe is measuredwithin that isophote. The MP satisfies the scalar virial relation MJAM ∝ σ2e Rmaje within our tight errors. This show that the larger scatter in the Fundamental Plane (FP) (L, σe, Re) is due to stellar population effects [including trends in the stellar initial mass function (IMF)]. It confirms that the FP deviation from the virial exponents is due to a genuine (M/L)e variation. However, the details of how both Re and σe are determined are critical in defining the precise deviation from the virial exponents. The main uncertainty in masses or M/L estimates using the scalar virial relation is in the measurement of Re. This problem is already relevant for nearby galaxies and may cause significant biases in virial mass and size determinations at high redshift. Dynamical models can eliminate these problems.We revisit the (M/L)e-σe relation, which describes most of the deviations between the MP and the FP. The best-fitting relation is (M/L)e ∝ σ0.72e (r band). It provides an upper limit to any systematic increase of the IMF mass normalization with σe. The correlation is more shallow and has smaller scatter for slow rotating systems or for galaxies in Virgo. For the latter, when using the best distance estimates, we observe a scatter in (M/L)e of 11 per cent, and infer an intrinsic one of 8 per cent. We perform an accurate empirical study of the link between se and the galaxies circular velocity Vcirc within 1Re (where stars dominate) and find the relation max (Vcirc) ≈ 1.76 × σe, which has an observed scatter of 7 per cent. The accurate parameters described in this paper are used in the companion Paper XX (Cappellari et al.) of this series to explore the variation of global galaxy properties, including the IMF, on the projections of the MP. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


The ATLAS<sup>3D</sup> project - XXI. Correlations between gradients of local escape velocity and stellar populations in early-type galaxies

Monthly Notices of the Royal Astronomical Society 432 (2013) 1894-1913

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

We explore the connection between the local escape velocity, Vesc, and the stellar population properties in the ATLAS3D survey, a complete, volume-limited sample of nearby early-type galaxies. We make use of ugriz photometry to construct Multi-Gaussian Expansion models of the surface brightnesses of our galaxies. We are able to fit the full range of surface brightness profiles found in our sample, and in addition we reproduce the results of state-ofthe- art photometry in the literature with residuals of 0.04 mag. We utilize these photometric models and SAURON integral-field spectroscopy, combined with Jeans dynamical modelling, to determine the local Vesc derived from the surface brightness. We find that the local Vesc is tightly correlated with the Mg b and Fe5015 line strengths and optical colours, and anticorrelated with the Hβ line strength. In the case of the Mg b and colour-Vesc relations we find that the relation within individual galaxies follows the global relation between different galaxies. We intentionally ignored any uncertain contribution due to dark matter since we are seeking an empirical description of stellar population gradients in early-type galaxies that is ideal for quantitative comparison with model predictions. We also make use of single stellar population (SSP) modelling to transform our line strength index measurements into the SSP-equivalent parameters age (t), metallicity ([Z/H]) and α-enhancement [α/Fe]. The residuals from the relation are correlated with age, [α/Fe], molecular gas mass and local environmental density. We identify a population of galaxies that occur only at low Vesc that exhibit negative gradients in the Mg b-and Colour-Vesc relations. These galaxies typically have young central stellar populations and contain significant amounts of molecular gas and dust. Combining these results with N-body simulations of binary mergers we use the Mgb-Vesc relation to constrain the possible number of dry mergers experienced by the local early-type galaxy population-a typical massive early-type galaxy can have experienced only ∼1.5 major mergers before becoming a significant outlier in the Mgb-Vesc relation. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


The ATLAS<sup>3D</sup> project - XXII. Low-efficiency star formation in early-type galaxies: Hydrodynamic models and observations

Monthly Notices of the Royal Astronomical Society 432 (2013) 1914-1927

M Martig, AF Crocker, F Bournaud, E Emsellem, JM Gabor, K Alatalo, L Blitz, M Bois, M Bureau, M Cappellari, RL Davies, TA Davis, A Dekel, PT de Zeeuw, PA Duc, J Falcón-Barroso, S Khochfar, D Krajnović, H Kuntschner, R Morganti, RM McDermid, T Naab, T Oosterloo, M Sarzi, N Scott, P Serra, KS Griffin, R Teyssier, AM Weijmans, LM Young

We study the global efficiency of star formation in high-resolution hydrodynamical simulations of gas discs embedded in isolated early-type and spiral galaxies. Despite using a universal local law to form stars in the simulations, we find that the early-type galaxies are offset from the spirals on the large-scale Kennicutt relation, and form stars two to five times less efficiently. This offset is in agreement with previous results on morphological quenching: gas discs are more stable against star formation when embedded in early-type galaxies due to the lower disc self-gravity and increased shear. As a result, these gas discs do not fragment into dense clumps and do not reach as high densities as in the spiral galaxies. Even if some molecular gas is present, the fraction of very dense gas (typically above 104 cm-3) is significantly reduced, which explains the overall lower star formation efficiency. We also analyse a sample of local early-type and spiral galaxies, measuring their CO and HI surface densities and their star formation rates as determined by their non-stellar 8 μm emission. As predicted by the simulations, we find that the early-type galaxies are offset from the Kennicutt relation compared to the spirals, with a twice lower efficiency. Finally, we validate our approach by performing a direct comparison between models and observations. We run a simulation designed to mimic the stellar and gaseous properties of NGC 524, a local lenticular galaxy, and find a gas disc structure and global star formation rate in good agreement with the observations. Morphological quenching thus seems to be a robust mechanism, and is also consistent with other observations of a reduced star formation efficiency in early-type galaxies in the COLD GASS survey. This lower efficiency of star formation is not enough to explain the formation of the whole red sequence, but can contribute to the reddening of some galaxies. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


The ATLAS<sup>3D</sup> project - XVII. Linking photometric and kinematic signatures of stellar discs in early-type galaxies

Monthly Notices of the Royal Astronomical Society 432 (2013) 1768-1795

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

We analyse the morphological structures in galaxies of the ATLAS3D sample by fitting a single Sérsic profile and decomposing all non-barred objects (180 of 260 objects) in two components parametrized by an exponential and a general Sérsic function. The aim of this analysis is to look for signatures of discs in light distributions of nearby early-type galaxies and compare them to kinematic properties. Using Sérsic index from single-component fits for a distinction between slow and fast rotators, or even late- and early-type galaxies, is not recommended. Assuming that objects with n > 3 are slow rotators (or ellipticals), there is only a 22 per cent probability to correctly classify objects as slow rotators (or 37 per cent of previously classified as ellipticals). We show that exponential sub-components, as well as light profiles fitted with only a single component of a low Sérsic index, can be linked with the kinematic evidence for discs in early-type galaxies. The median disc-to-total light ratio for fast and slow rotators is 0.41 and 0.0, respectively. Similarly, the median Sérsic indices of the bulge (general Sérsic component) are 1.7 and 4.8 for fast and slow rotators, respectively. Overall, discs or disc-like structures are present in 83 per cent of early-type galaxies which do not have bars, and they show a full range of disc-to-total light ratios. Discs in early-type galaxies contribute with about 40 per cent to the total mass of the analysed (non-barred) objects. The decomposition into discs and bulges can be used as a rough approximation for the separation between fast and slow rotators, but it is not a substitute, as there is only a 59 per cent probability to correctly recognize slow rotators. We find trends between the angular momentum and the disc-to-total light ratios and the Sérsic index of the bulge, in the sense that high angular momentum galaxies have large disc-to-total light ratios and small bulge indices, but there is none between the angular momentum and the global Sérsic index. We investigate the inclination effects on the decomposition results and confirm that strong exponential profiles can be distinguished even at low inclinations, but medium-size discs are difficult to quantify using photometry alone at inclinations lower than ∼50°. Kinematics (i.e. projected angular momentum) remains the best approach to mitigate the influence of the inclination effects.We also find weak trends with mass and environmental density, where disc-dominated galaxies are typically less massive and found at all densities, including the densest region sampled by the ATLAS3D sample. © 2012 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


The ATLAS<sup>3D</sup> project - XIX. The hot gas content of early-type galaxies: Fast versus slow rotators

Monthly Notices of the Royal Astronomical Society 432 (2013) 1845-1861

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

For early-type galaxies, the ability to sustain a corona of hot, X-ray-emitting gas could have played a key role in quenching their star formation history. A halo of hot gas may act as an effective shield against the acquisition of cold gas and can quickly absorb stellar mass loss material. Yet, since the discovery by the Einstein Observatory of such X-ray haloes around early-type galaxies, the precise amount of hot gas around these galaxies still remains a matter of debate. By combining homogeneously derived photometric and spectroscopic measurements for the early-type galaxies observed as part of the ATLAS3D integral field survey with measurements of their X-ray luminosity based on X-ray data of both low and high spatial resolution (for 47 and 19 objects, respectively) we conclude that the hot gas content of early-type galaxies can depend on their dynamical structure. Specifically, whereas slow rotators generally have X-ray haloes with luminosity LX, gas and temperature T values that are well in line with what is expected if the hot gas emission is sustained by the thermalization of the kinetic energy carried by the stellar mass loss material, fast rotators tend to display LX, gas values that fall consistently below the prediction of thismodel, with similar T values that do not scale with the stellar kinetic energy (traced by the stellar velocity dispersion) as observed in the case of slow rotators. Such a discrepancy between the hot gas content of slow and fast rotators would appear to reduce, or even disappear, for large values of the dynamical mass (above ∼3× 1011Mȯ), with younger fast rotators displaying also somewhat larger LX, gas values possibly owing to the additional energy input from recent supernovae explosions. Considering that fast rotators are likely to be intrinsically flatter than slow rotators, and that the few LX, gas-deficient slow rotators also happen to be relatively flat, the observed LX, gas deficiency in these objects would support the hypothesis whereby flatter galaxies have a harder time in retaining their hot gas, although we suggest that the degree of rotational support could further hamper the efficiency with which the kinetic energy of the stellar mass loss material is thermalized in the hot gas. We discuss the implications that a different hot gas content could have on the fate of both acquired and internally produced gaseous material, considering in particular how the LX, gas deficiency of fast rotators would make them more capable to recycle the stellar mass loss material into new stars than slow rotators. This would be consistent with the finding that molecular gas and young stellar populations are detected only in fast rotators across the entire ATLAS3D sample, and that fast rotators tend to have a larger specific dust mass content than slow rotators. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


The planetary nebulae population in the nuclear regions of M31: the SAURON view

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 430 (2013) 1219-1229

N Pastorello, M Sarzi, M Cappellari, E Emsellem, GA Mamon, R Bacon, RL Davies, PT de Zeeuw


The ATLAS<sup>3D</sup> project-XX. Mass-size and mass-σ distributions of early-type galaxies: Bulge fraction drives kinematics, mass-to-light ratio, molecular gas fraction and stellar initial mass function

Monthly Notices of the Royal Astronomical Society 432 (2013) 1862-1893

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

In the companion Paper XV of this series, we derive accurate total mass-to-light ratios (M/L)JAM ≈ (M/L)(r = Re) within a sphere of radius r = Re centred on the galaxy, as well as stellar (M/L)stars (with the dark matter removed) for the volume-limited and nearly massselected (stellarmassM* ≲ 6 × 109M⊙)ATLAS3D sample of 260 early-type galaxies (ETGs, ellipticals Es and lenticulars S0s). Here, we use those parameters to study the two orthogonal projections (MJAM, σe) and (MJAM,R maje ) of the thin Mass Plane (MP) (MJAM, σe,Rmaje ) which describes the distribution of the galaxy population, where MJAM = L × (M/L)JAM ≈ M*. The distribution of galaxy properties on both projections of the MP is characterized by: (i) the same zone of exclusion (ZOE), which can be transformed from one projection to the other using the scalar virial equation. The ZOE is roughly described by two power laws, joined by a break at a characteristic mass MJAM ≈ 3 × 1010M⊙, which corresponds to the minimum Re and maximum stellar density. This results in a break in the meanMJAM-σe relation with trends MJAM α σ2.3e and MJAM α σ4.7e at small and large σe, respectively; (ii) a characteristic mass MJAM ≈ 2 × 1011M⊙ which separates a population dominated by flat fast rotator with discs and spiral galaxies at lower masses, from one dominated by quite round slow rotators at larger masses; (iii) below that mass the distribution of ETGs' properties on the two projections of the MP tends to be constant along lines of roughly constant se, or equivalently along lines with Rmaje α MJAM, respectively (or even better parallel to the ZOE: Rmaje α M0.75JAM); (iv) it forms a continuous and parallel sequence with the distribution of spiral galaxies; (v) at even lower masses, the distribution of fast-rotator ETGs and late spirals naturally extends to that of dwarf ETGs (Sph) and dwarf irregulars (Im), respectively. We use dynamical models to analyse our kinematic maps. We show that σe traces the bulge fraction, which appears to be the main driver for the observed trends in the dynamical (M/L)JAM and in indicators of the (M/L)pop of the stellar population like Hβ and colour, as well as in the molecular gas fraction. A similar variation along contours of σe is also observed for the mass normalization of the stellar initial mass function (IMF), which was recently shown to vary systematically within the ETGs' population. Our preferred relation has the form log10[(M/L)stars/(M/L)Salp] = a + b × log10(σe/130 km s-1) with a=-0.12 ± 0.01 and b = 0.35 ± 0.06. Unless there are major flaws in all stellar population models, this trend implies a transition of the mean IMF from Kroupa to Salpeter in the interval log10(σe/km s-1) ≈ 1.9-2.5 (or σe ≈ 90-290 km s-1), with a smooth variation in between, consistently with what was shown in Cappellari et al. The observed distribution of galaxy properties on the MP provides a clean and novel view for a number of previously reported trends, which constitute special two-dimensional projections of the more general four-dimensional parameters trends on the MP. We interpret it as due to a combination of two main effects: (i) an increase of the bulge fraction, which increases σe, decreases Re, and greatly enhance the likelihood for a galaxy to have its star formation quenched, and (ii) dry merging, increasing galaxy mass and Re by moving galaxies along lines of roughly constant σe (or steeper), while leaving the population nearly unchanged. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

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