arXiv subjects

Richard M. McDermid

Publications and source records attributed to Richard M. McDermid.

At least 91 records · Page 5Linked to original sources

arXiv2011

The ATLAS3D Project-- VIII: Modelling the Formation and Evolution of Fast and Slow Rotator Early-Type Galaxies within $Λ$CDM

We propose a simple model for the origin of fast and slow rotator early-type galaxies (ETG) within the hierarchical $Λ$CDM scenario, that is based on the assumption that the mass fraction of stellar discs in ETGs is a proxy for the specific angular momentum expressed via $λ_R$. Within our model we reproduce the fraction of fast and slow rotators as a function of magnitude in the \atl survey, assuming that fast rotating ETGs have at least 10% of their total stellar mass in a disc component. In agreement with \atl observations we find that slow rotators are predominantly galaxies with $ M_* > 10^{10.5}$ M$_{\odot}$ contributing $\sim 20%$ to the overall ETG population. We show in detail that the growth histories of fast and slow rotators are different, supporting the classification of ETGs into these two categories. Slow rotators accrete between $\sim 50% -90%$ of their stellar mass from satellites and their most massive progenitors have on average up to 3 major mergers during their evolution. Fast rotators in contrast, accrete less than 50% and have on average less than one major merger in their past. We find that the underlying physical reason for the different growth histories is the slowing down and ultimately complete shut-down of gas cooling in massive galaxies. Once cooling and associated star formation in disc stops, galaxies grow via infall from satellites. Frequent minor mergers thereby, destroy existing stellar discs via violent relaxation and also tend to lower the specific angular momentum of the main stellar body, lowering $λ_R$ into the slow rotator regime. Abridged...

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arXiv2011

The Atlas3D project - X. On the origin of the molecular and ionised gas in early-type galaxies

We make use of interferometric CO and HI observations, and optical integral-field spectroscopy to probe the origin of the molecular and ionised interstellar medium (ISM) in local early-type galaxies (ETGs). We find that 36\pm5% of our sample of fast rotating ETGs have their ionised gas kinematically misaligned with respect to the stars, setting a strong lower limit on the importance of externally acquired gas (e.g. from mergers and cold accretion). Slow rotators have a flat distribution of misalignments, indicating that the dominant source of gas is external. The molecular, ionised and atomic gas in all the detected galaxies are always kinematically aligned, even when they are misaligned from the stars, suggesting that all these three phases of the ISM share a common origin. In addition, we find that the origin of the cold and warm gas in fast-rotating ETGs is strongly affected by environment, despite the molecular gas detection rate and mass fractions being fairly independent of group/cluster membership. Galaxies in dense groups and the Virgo cluster nearly always have their molecular gas kinematically aligned with the stellar kinematics, consistent with a purely internal origin. In the field, however, kinematic misalignments between the stellar and gaseous components indicate that >46% of local fast-rotating ETGs have their gas supplied from external sources. We discuss several scenarios which could explain the environmental dichotomy, but find it difficult to simultaneously explain the kinematic misalignment difference and the constant detection rate. Furthermore, our results suggest that galaxy mass may be an important independent factor associated with the origin of the gas, with the most massive fast-rotating galaxies in our sample (M_K<-24 mag; stellar mass of >8x10^10 Msun) always having kinematically aligned gas. (abridged)

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arXiv2011

The Atlas-3D project - IX. The merger origin of a fast and a slow rotating Early-Type Galaxy revealed with deep optical imaging: first results

The mass assembly of galaxies leaves imprints in their outskirts, such as shells and tidal tails. The frequency and properties of such fine structures depend on the main acting mechanisms - secular evolution, minor or major mergers - and on the age of the last substantial accretion event. We use this to constrain the mass assembly history of two apparently relaxed nearby Early-Type Galaxies (ETGs) selected from the Atlas-3D sample, NGC 680 and NGC 5557. Our ultra deep optical images obtained with MegaCam on the Canada-France-Hawaii Telescope reach 29 mag/arcsec^2 in the g-band. They reveal very low-surface brightness (LSB) filamentary structures around these ellipticals. Among them, a gigantic 160 kpc long tail East of NGC 5557 hosts gas-rich star-forming objects. NGC 680 exhibits two major diffuse plumes apparently connected to extended HI tails, as well as a series of arcs and shells. Comparing the outer stellar and gaseous morphology of the two ellipticals with that predicted from models of colliding galaxies, we argue that the LSB features are tidal debris, the star-forming objects near NGC 5557, long lived Tidal Dwarf Galaxies and that each of the two ETGs was assembled during a relatively recent, major wet merger, which likely occurred at a redshift below z = 0.5. The inner kinematics of NGC 680 is typical for fast rotators which make the bulk of nearby ETGs in the Atlas-3D sample. NGC 5557 belongs to the poorly populated class of massive, round, slow rotators that are predicted by semi-analytic models and cosmological simulations to be the end-product of a complex mass accretion history, involving ancient major mergers and more recent minor mergers. Our observations suggest that under specific circumstances a single binary merger may dominate the formation history of such objects and thus that at least some massive ETGs may form at relatively low redshift (abridged).

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arXiv2011

The Atlas3D Project - VI. Simulations of binary galaxy mergers and the link with Fast Rotators, Slow Rotators, and Kinematically Distinct Cores

We study the formation of early-type galaxies through mergers with a sample of 70 high-resolution (softening length < 60 pc and 12*10^6 particles) numerical simulations of binary mergers of disc galaxies and 16 simulations of ETG remergers. These simulations, designed to accompany observations and models conducted within the Atlas3D project, encompass various mass ratios (from 1:1 to 6:1), initial conditions and orbital parameters. The progenitor disc galaxies are spiral-like with bulge to disc ratios typical of Sb and Sc galaxies. We find that binary mergers of disc galaxies with mass ratios of 3:1 and 6:1 are nearly always classified as Fast Rotators according to the Atlas3D criterion (based on the lambda_R parameter): they preserve the structure of the input fast rotating spiral progenitors. They have intrinsic ellipticities larger than 0.5, cover intrinsic lambda_R values between 0.2 and 0.6, within the range of observed Fast Rotators. Major disc mergers (mass ratios of 2:1 and 1:1) lead to both Fast and Slow Rotators. Most of the Fast Rotators produced in major mergers have intermediate flattening, with ellipticities between 0.4 and 0.6. Most Slow Rotators formed in these binary disc mergers hold a stellar Kinematically Distinct Core (KDC) in their 1-3 central kilo-parsec: these KDCs are built from the stellar components of the progenitors. Besides a handful of specific observed systems -- the counter-rotating discs (2-sigma galaxies) -- these therefore cannot reproduce the observed population of Slow Rotators in the nearby Universe. The mass ratio of the progenitors is a fundamental parameter for the formation of Slow Rotators in these binary mergers, but it also requires a retrograde spin for the earlier-type (Sb) progenitor galaxy with respect to the orbital angular momentum. (Abridged)

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arXiv2011

The Atlas3D project - VII. A new look at the morphology of nearby galaxies: the kinematic morphology-density relation

We look at the morphology of fast and slow rotator early-type galaxies. Edge-on fast rotators are lenticular galaxies. They appear like spiral galaxies with the gas and dust removed, and in some cases are flat ellipticals with disky isophotes. Fast rotators are often barred and span the same full range of bulge fractions as spiral galaxies. The slow rotators are rounder and are generally consistent with being genuine, namely spheroidal-like, elliptical galaxies. We propose a revision to the tuning-fork diagram by Hubble as it gives a misleading description of ETGs. We study for the first time the kinematic morphology-density T-Sigma relation using fast and slow rotators to replace lenticulars and ellipticals. We find that our relation is cleaner than using classic morphology. Slow rotators are nearly absent at the lowest density environments [f(SR)<2%] and generally constitute a small fraction [f(SR)~4%] of the total galaxy population in the environments explored by our survey, with the exception of the densest core of the Virgo cluster [f(SR)~20%]. We find a clean log-linear relation between the fraction f(Sp) of spiral galaxies and the local galaxy surface density. The existence of a smooth kinematic T-Sigma relation in the field excludes processes related to the cluster environment as main contributors to the apparent conversion of spirals into fast-rotators in low-density environments. It shows that the segregation is driven by local effects at the small-group scale. Only at the largest densities in the Virgo core does the f(Sp) relation break down and steepens sharply, while the fraction of slow-rotators starts to significantly increase. This suggests that a different mechanism is at work there. (Abridged)

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arXiv2011

Discovery of an AGN-Driven Molecular Outflow in the Local Early-Type Galaxy NGC 1266

We report the discovery of a powerful molecular wind from the nucleus of the non-interacting nearby S0 field galaxy NGC 1266. The single-dish CO profile exhibits emission to +/- 400 km/s and requires a nested Gaussian fit to be properly described. Interferometric observations reveal a massive, centrally- concentrated molecular component with a mass of 1.1x10^9 Msuns and a molecular outflow with a molecular mass of 2.4x10^7 Msuns. The molecular gas close to the systemic velocity consists of a rotating, compact nucleus with a mass of about 4.1x108 Msuns within a radius of approximately 60 pc. This compact molecular nucleus has a surface density of \approx 2.7 \times 10^4 Msuns/pc^2, more than two orders of magnitude larger than that of giant molecular clouds in the disk of the Milky Way, and it appears to sit on the Kennicutt-Schmidt relation despite its extreme kinematics and energetic activity. We interpret this nucleus as a disk that confines the outflowing wind. A mass outflow rate of 13 Msuns/yr leads to a depletion timescale of about 85 Myr. The star formation in NGC 1266 is insufficient to drive the outflow, and thus it is likely driven by the active galactic nucleus (AGN). The concentration of the majority of the molecular gas in the central 100 pc requires an extraordinary loss of angular momentum, but no obvious companion or interacting galaxy is present to enable the transfer. NGC 1266 is the first known outflowing molecular system that does not show any evidence of a recent interaction.

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arXiv2011

The ATLAS3D project - II. Morphologies, kinemetric features and alignment between photometric and kinematic axes of early-type galaxies

[Abridged] We use the ATLAS3D sample of 260 early-type galaxies (ETGs) to study the apparent kinematic misalignment angle, Psi, defined as the angle between the photometric and kinematic major axis. We find that 71% of nearby ETGs are strictly aligned systems (Psi > 5 deg), an additional 14% have 5 < Psi < 10 deg and 90% of galaxies have Psi < 15 deg. Taking into account measurement uncertainties, 90% of galaxies can be considered aligned to better than 5 deg, suggesting that only a small fraction of early-type galaxies (~10%) are not consistent with axisymmetry within the projected half-light radius. We identify morphological features such as bars and rings (30%), dust structures (16%), blue nuclear colours (6%) and evidence of interactions (8%). We use kinemetry to analyse the mean velocity maps and separate galaxies in two broad types of regular and non-regular rotators. We find 82% of regular rotators and 17% non-regular rotators, with 2 galaxies that we were not able to classify due to data quality. The non-regular rotators are typically found in dense regions and are massive. The majority of galaxies do not have any specific kinemetric features, but we highlight here the frequency of the kinematically distinct cores (7%) and the aligned double peaks in the velocity dispersion maps (4%). Most of the galaxies that are misaligned have complex kinematics and are non-regular rotators. While the trends are weak, there is a tendency that large values of Psi are found in galaxies at intermediate environmental densities and among the most massive galaxies in the sample. We suggest that the most common formation mechanism for ETGs preserves the axisymmetry of the disk progenitors. Less commonly, the formation process results in a triaxial galaxy with much lower net angular momentum.

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arXiv2011

The Atlas3D project -- IV: the molecular gas content of early-type galaxies

We have carried out a survey for 12CO J=1-0 and J=2-1 emission in the 260 early-type galaxies of the volume-limited Atlas3D sample, with the goal of connecting their star formation and assembly histories to their cold gas content. This is the largest volume-limited CO survey of its kind and is the first to include many Virgo Cluster members. Sample members are dynamically hot galaxies with a median stellar mass 3\times 10^{10} Msun; they are selected by morphology rather than colour, and the bulk of them lie on the red sequence. The overall CO detection rate is 56/259 = 0.22 \error 0.03, with no dependence on K luminosity and only a modest dependence on dynamical mass. There are a dozen CO detections among the Virgo Cluster members; statistical analysis of their H_2 mass distributions and their dynamical status within the cluster shows that the cluster's influence on their molecular masses is subtle at best, even though (unlike spirals) they seem to be virialized within the cluster. We suggest that the cluster members have retained their molecular gas through several Gyr residences in the cluster. There are also a few extremely CO-rich early-type galaxies with H_2 masses >= 10^9 Msun, and these are in low density environments. We do find a significant trend between molecular content and the stellar specific angular momentum. The galaxies of low angular momentum also have low CO detection rates, suggesting that their formation processes were more effective at destroying molecular gas or preventing its re-accretion. We speculate on the implications of these data for the formation of various sub-classes of early-type galaxies.

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arXiv2011

The Atlas3D project - V. The CO Tully-Fisher relation of early-type galaxies

We demonstrate here using both single-dish and interferometric observations that CO molecules are an excellent kinematic tracer, even in high-mass galaxies, allowing us to investigate for the first time the CO Tully-Fisher relation of early-type galaxies. We compare the Tully-Fisher relations produced using both single-dish and interferometric data and various inclination estimation methods, and evaluate the use of the velocity profile shape as a criterion for selecting galaxies in which the molecular gas extends beyond the peak of the rotation curve. We show that the gradient and zero-point of the best-fit relations are robust, independent of the velocity measure and inclination used, and agree with those of relations derived using stellar kinematics. We also show that the early-type CO Tully-Fisher (CO-TF) relation is offset from the CO-TF of spirals by 0.98 \pm 0.22 magnitude at Ks-band, in line with other results. The intrinsic scatter of the relation is found to be \approx 0.4 magnitudes, similar to the level found in the spiral galaxy population. Next generation facilities such as the Large Millimeter Telescope (LMT) and the Atacama Large Millimeter/Sub-millimeter Array (ALMA) should allow this technique to be used in higher-redshift systems, providing a simple new tool to trace the mass-to-light ratio evolution of the most massive galaxies over cosmic time.

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arXiv2011

The ATLAS3D project - III. A census of the stellar angular momentum within the effective radius of early-type galaxies: unveiling the distribution of Fast and Slow Rotators

We provide a census of the apparent stellar angular momentum within 1 Re of a volume-limited sample of 260 early-type galaxies (ETGs) in the nearby Universe, using integral-field spectroscopy obtained in the course of the ATLAS3D project. We exploit the LambdaR parameter to characterise the existence of two families of ETGs: Slow Rotators which exhibit complex stellar velocity fields and often include stellar kinematically Distinct Cores (KDCs), and Fast Rotators which have regular velocity fields. Our complete sample of 260 ETGs leads to a new criterion to disentangle Fast and Slow Rotators which now includes a dependency on the apparent ellipticity (Epsilon). It separates the two classes significantly better than the previous prescription, and than a criterion based on V/Sigma: Slow Rotators and Fast Rotators have LambdaR lower and larger than kFSxSQRT(Epsilon), respectively, where kFS=0.31 for measurements made within 1 Re. We show that the vast majority of early-type galaxies are Fast Rotators: these have regular stellar rotation, with aligned photometric and kinematic axes (Paper II, Krajnovic et al. 2011}, include discs and often bars and represent 86% (224/260) of all early-type galaxies in the volume-limited ATLAS3D sample. Fast Rotators span the full range of apparent ellipticities from 0 to 0.85, and we suggest that they cover intrinsic ellipticities from about 0.35 to 0.85, the most flattened having morphologies consistent with spiral galaxies. Only a small fraction of ETGs are Slow Rotators representing 14% (36/260) of the ATLAS3D sample of ETGs. Of all Slow Rotators, 11% (4/36) exhibit two counter-rotating stellar disc-like components and are rather low mass objects (Mdyn<10^10.5 M_Sun). All other Slow Rotators (32/36) appear relatively round on the sky (Epsilon_e<0.4), tend to be massive (Mdyn>10^10.5 M_Sun), and often (17/32) exhibit KDCs.

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arXiv2011

The SAURON project - XVIII. The integrated UV-linestrength relations of early-type galaxies

Using far (FUV) and near (NUV) ultraviolet photometry from guest investigator programmes on the Galaxy Evolution Explorer (GALEX) satellite, optical photometry from the MDM Observatory and optical integral-field spectroscopy from SAURON, we explore the UV-linestrength relations of the 48 nearby early-type galaxies in the SAURON sample. Identical apertures are used for all quantities, avoiding aperture mismatch. We show that galaxies with purely old stellar populations show well-defined correlations of the integrated FUV-V and FUV-NUV colours with the integrated Mgb and Hbeta absorption linestrength indices, strongest for FUV-NUV. Correlations with the NUV-V colour, Fe5015 index and stellar velocity dispersion are much weaker. These correlations put stringent constraints on the origin of the UV-upturn phenomenon in early-type galaxies, and highlight its dependence on age and metallicity. In particular, despite recent debate, we recover the negative correlation between FUV-V colour and Mg linestrength originally publicised by Burstein et al. (1988), which we refer to as the "Burstein relation", suggesting a positive dependence of the UV-upturn on metallicity. We argue that the scatter in the correlations is real, and present mild evidence that a strong UV excess is preferentially present in slow-rotating galaxies. We also demonstrate that most outliers in the correlations are galaxies with current or recent star formation, some at very low levels. We believe that this sensitivity to weak star formation, afforded by the deep and varied data available for the SAURON sample, explains why our results are occasionally at odds with other recent but shallower surveys. This is supported by the analysis of a large, carefully-crafted sample of more distant early-type galaxies from the Sloan Digital Sky Survey (SDSS), more easily comparable with current and future large surveys.

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arXiv2010

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

[Abridged] We present two-dimensional line-of-sight stellar kinematics of the lens galaxy in the Einstein Cross, obtained with the GEMINI 8m telescope, using the GMOS integral-field spectrograph. The velocity map shows regular rotation up to ~100 km/s around the minor axis of the bulge, consistent with axisymmetry. The velocity dispersion map shows a weak gradient increasing towards a central (R<1") value of sigma_0=170+/-9 km/s. We deproject the observed surface brightness from HST 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 find that the resulting luminous and total mass distribution are nearly identical around the Einstein radius R_E = 0.89", with a slope that is close to isothermal, but which becomes shallower towards the center if indeed mass follows light. The dynamical model fits to the observed kinematic maps result in a total mass-to-light ratio (M/L)_dyn=3.7+/-0.5 M_sun/L_sun,I (in the I-band). This is consistent with the Einstein mass M_E = 1.54 x 10^10 M_sun divided by the (projected) luminosity within R_E, which yields a total mass-to-light ratio of (M/L)_E=3.4 M_sun/L_sun,I, with an error of at most a few per cent. We estimate from stellar populations model fits to colors of the lens galaxy a stellar mass-to-light ratio (M/L)_* from 2.8 to 4.1 M_sun/L_sun,I. Although a constant dark matter fraction of 20 per cent is not excluded, dark matter may play no significant role in the bulge of this ~L* early-type spiral galaxy.

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arXiv2010

The Atlas3D project -- I. A volume-limited sample of 260 nearby early-type galaxies: science goals and selection criteria

The Atlas3D project is a multi-wavelength survey combined with a theoretical modeling effort. The observations span from the radio to the millimeter and optical, and provide multi-colour imaging, two-dimensional kinematics of the atomic (HI), molecular (CO) and ionized gas (Hbeta, [OIII] and [NI]), together with the kinematics and population of the stars (Hbeta, Fe5015 and Mgb), for a carefully selected, volume-limited (1.16*10^5 Mpc^3) sample of 260 early-type (elliptical E and lenticular S0) galaxies (ETGs). The models include semi-analytic, N-body binary mergers and cosmological simulations of galaxy formation. Here we present the science goals for the project and introduce the galaxy sample and the selection criteria. The sample consists of nearby (D<42 Mpc) morphologically-selected ETGs extracted from a parent sample of 871 galaxies (8% E, 22% S0 and 70% spirals) brighter than M_K<-21.5 mag (stellar mass M_Star>6*10^9 M_Sun). We analyze possible selection biases and we conclude that the parent sample is essentially complete and statistically representative of the nearby galaxy population. We present the size-luminosity relation for the spirals and ETGs and show that the ETGs in the Atlas3D sample define a tight red sequence in a colour-magnitude diagram, with few objects in the transition from the blue cloud. We describe the strategy of the SAURON integral-field observations and the extraction of the stellar kinematics with the pPXF method. We give an overview of the characteristics of the other main datasets already available for our sample and of the ongoing modelling projects.

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arXiv2010

The SAURON project - XVII. Stellar population analysis of the absorption line strength maps of 48 early-type galaxies

(Abridged) We present a stellar population analysis of the absorption line strength maps for 48 early-type galaxies from the SAURON sample. Using the line strength index maps of Hbeta, Fe5015, and Mgb, measured in the Lick/IDS system and spatially binned to a constant signal-to-noise, together with predictions from up-to-date stellar population models, we estimate the simple stellar population-equivalent (SSP-equivalent) age, metallicity and abundance ratio [alpha/Fe] over a two-dimensional field extending up to approximately one effective radius. We find a large range of SSP-equivalent ages in our sample, of which ~40% of the galaxies show signs of a contribution from a young stellar population. The most extreme cases of post-starburst galaxies, with SSP-equivalent ages of <=3 Gyr observed over the full field-of-view, and sometimes even showing signs of residual star-formation, are restricted to low mass systems(sigma_e <= 100 k/ms or ~2x10^10 M_sol). Spatially restricted cases of young stellar populations in circumnuclear regions can almost exclusively be linked to the presence of star-formation in a thin, dusty disk/ring, also seen in the near-UV or mid-IR. The flattened components with disk-like kinematics previously identified in all fast rotators (Krajnović et al.) are shown to be connected to regions of distinct stellar populations. These range from the young, still star-forming circumnuclear disks and rings with increased metallicity preferentially found in intermediate-mass fast rotators, to apparently old structures with extended disk-like kinematics, which are observed to have an increased metallicity and mildly depressed [alpha/Fe] ratio compared to the main body of the galaxy. The slow rotators generally show no stellar population signatures over and above the well known metallicity gradients and are largely consistent with old (>=10 Gyr) stellar populations.

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arXiv2010

Measuring the low mass end of the Mbh - sigma relation

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 (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.

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arXiv2010

Testing Mass Determinations of Supermassive Black Holes via Stellar Kinematics

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

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arXiv2009

The SAURON project XVI: On the Sources of Ionisation for the Gas in Elliptical and Lenticular Galaxies

Following our study on the incidence, morphology and kinematics of the ionised 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, 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 [OIII]/Hb and [NI]/Hb line ratios. We find a tight correlation between the stellar surface brightness and the flux of the Hb recombination line across our sample, which points to a diffuse and old stellar source as the main contributor of ionising photons in early-type galaxies, with post-asymptotic giant branch (pAGB) stars being still the best candidate based on ionising-balance arguments. Other ionising sources such as a central AGN, OB-stars, shocks or the interaction between the hot and warm phases of the interestellar medium are found to play only a limited or localised role in powering the diffuse nebular emission observed in our sample galaxies. These results lead us to investigate the relative importance of stellar and AGN photoionisation in explaining the ionised-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 early-type galaxies that display modest values for the equivalent width of the [OIII] line (less than ~2.4Å) and LINER-like [OIII]/Hb values, the nebular emission is truly powered by an AGN.

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arXiv2009

Determination of masses of the central black holes in NGC524 and NGC2549 using Laser Guide Star Adaptive Optics

[abridged] We present observations of NGC524 and NGC2549 with LGS AO obtained at GEMINI North telescope using the NIFS IFU in the K band. The purpose of these observations, together with previously obtained observations with the SAURON IFU, is to determine the masses (Mbh) of the supermassive black holes (SMBH). The targeted galaxies were chosen to have central light profiles showing a core (NGC524) and a cusp (NGC2549), to probe the feasibility of using the galaxy centre as the NGS required for LGS AO. We employ an innovative `open loop' technique. The data have spatial resolution of 0.23" and 0.17" FWHM, showing that high quality LGS AO observations of these objects are possible. We construct axisymmetric three-integral dynamical models which are constrained with both the NIFS and SAURON data. The best fitting models yield Mbh=(8.3 +2.7 -1.3) x 10^8 Msun for NGC524 and Mbh=(1.4 +0.2 -1.3) x 10^7 Msun for NGC2549 (all errors are at the 3 sigma CL). 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 Mbh. The NIFS data are crucial in constraining the lower limits of Mbh 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 NGC524 shows significant tangential anisotropy, while at larger radii both galaxies are consistent with having almost perfectly oblate velocity ellipsoids. Tangential anisotropy in NGC524 coincides with the size of SMBH sphere of influence and the core region in the light profile. We test the accuracy to which Mbh can be measured using seeings obtained from typical LGS AO observations, and conclude that for a typical conditions and Mbh the expected uncertainty is of the order of 50%.

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