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Fundamental Plane (fundamental + plane)

Distribution by Scientific Domains

Physics and Astronomy	93%

Selected Abstracts

Cosmology and cluster halo scaling relations

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2009
Pablo A. Araya-Melo
ABSTRACT We explore the effects of dark matter and dark energy on the dynamical scaling properties of galaxy clusters. We investigate the cluster Faber,Jackson (FJ), Kormendy and Fundamental Plane (FP) relations between the mass, radius and velocity dispersion of cluster-sized haloes in cosmological N -body simulations. The simulations span a wide range of cosmological parameters, representing open, flat and closed Universes. Independently of the cosmology, we find that the simulated clusters are close to a perfect virial state and do indeed define an FP. The fitted parameters of the FJ, Kormendy and FP relationships do not show any significant dependence on ,m and/or ,,. One outstanding effect is the influence of ,m on the thickness of the FP. Following the time evolution of our models, we find slight changes of FJ and Kormendy parameters in high-,m universe, along with a slight decrease of FP fitting parameters. We also see an initial increase of the FP thickness followed by a convergence to a nearly constant value. The epoch of convergence is later for higher values of ,m, while the thickness remains constant in the low- ,m , models. We also find a continuous increase of the FP thickness in the standard cold dark matter cosmology. There is no evidence that these differences are due to the different power spectrum slopes at cluster scales. From the point of view of the FP, there is little difference between clusters that quietly accreted their mass and those that underwent massive mergers. The principal effect of strong mergers is to significantly change the ratio of the half-mass radius rhalf to the harmonic mean radius rh. [source]

The SAURON project , IV.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006
The mass-to-light ratio, lenticular galaxies, the Fundamental Plane of elliptical, the virial mass estimator
ABSTRACT We investigate the well-known correlations between the dynamical mass-to-light ratio (M/L) and other global observables of elliptical (E) and lenticular (S0) galaxies. We construct two-integral Jeans and three-integral Schwarzschild dynamical models for a sample of 25 E/S0 galaxies with SAURON integral-field stellar kinematics to about one effective (half-light) radius Re. They have well-calibrated I -band Hubble Space Telescope WFPC2 and large-field ground-based photometry, accurate surface brightness fluctuation distances, and their observed kinematics is consistent with an axisymmetric intrinsic shape. All these factors result in an unprecedented accuracy in the M/L measurements. We find a tight correlation of the form (M/L) = (3.80 ± 0.14) × (,e/200 km s,1)0.84±0.07 between the M/L (in the I band) measured from the dynamical models and the luminosity-weighted second moment ,e of the LOSVD within Re. The observed rms scatter in M/L for our sample is 18 per cent, while the inferred intrinsic scatter is ,13 per cent. The (M/L),,e relation can be included in the remarkable series of tight correlations between ,e and other galaxy global observables. The comparison of the observed correlations with the predictions of the Fundamental Plane (FP), and with simple virial estimates, shows that the ,tilt' of the FP of early-type galaxies, describing the deviation of the FP from the virial relation, is almost exclusively due to a real M/L variation, while structural and orbital non-homology have a negligible effect. When the photometric parameters are determined in the ,classic' way, using growth curves, and the ,e is measured in a large aperture, the virial mass appears to be a reliable estimator of the mass in the central regions of galaxies, and can be safely used where more ,expensive' models are not feasible (e.g. in high-redshift studies). In this case the best-fitting virial relation has the form (M/L)vir= (5.0 ± 0.1) ×Re,2e/(LG), in reasonable agreement with simple theoretical predictions. We find no difference between the M/L of the galaxies in clusters and in the field. The comparison of the dynamical M/L with the (M/L)pop inferred from the analysis of the stellar population, indicates a median dark matter fraction in early-type galaxies of ,30 per cent of the total mass inside one Re, in broad agreement with previous studies, and it also shows that the stellar initial mass function varies little among different galaxies. Our results suggest a variation in M/L at constant (M/L)pop, which seems to be linked to the galaxy dynamics. We speculate that fast-rotating galaxies have lower dark matter fractions than the slow-rotating and generally more-massive ones. If correct, this would suggest a connection between the galaxy assembly history and the dark matter halo structure. The tightness of our correlation provides some evidence against cuspy nuclear dark matter profiles in galaxies. [source]

Mergers between elliptical galaxies and the thickening of the Fundamental Plane

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2003
A. C. González-García
ABSTRACT We have carried out computer simulations to study the effect of merging on the Fundamental Plane (FP) relation. Initially, systems are spherical Jaffe models following a simple scaling relation (M/R2e= constant). They have been put on the FP by imposing different M/L values. Various orbital characteristics have been considered. Our results show that the merger remnants lie very close to the FP of the progenitors. Although non-homology is introduced by the merging process, mergers among homologous galaxies leave a pre-existing FP-relation intact. As a side result we find that variations in the point of view lead to non-negligible scatter about the FP. [source]

The internal structure of the lens PG1115+080: breaking degeneracies in the value of the Hubble constant

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2002
T. Treu
ABSTRACT We combine lensing, stellar kinematic and mass-to-light ratio constraints to build a two-component (luminous plus dark) mass model of the early-type lens galaxy in PG1115+080. We find a total mass density profile steeper than r,2, effectively ,,r,,, with ,,= 2.35 ± 0.1 ± 0.05 (random + systematic). The stellar mass fraction is f*= 0.67+0.20,0.25± 0.03 inside the Einstein radius (RE, 1.2 effective radii). The dynamical mass model breaks the degeneracies in the mass profile of the lens galaxy and allows us to obtain a value of the Hubble constant that is no longer dominated by systematic errors: H0= 59+12,7± 3 km s,1 Mpc,1 (68 per cent confidence level; ,m= 0.3, ,,= 0.7). The offset of PG1115+080 from the Fundamental Plane might indicate deviations from homology of the mass profile of some early-type galaxies. [source]

The evolution of cluster early-type galaxies over the past 8 Gyr

ASTRONOMISCHE NACHRICHTEN, Issue 9-10 2009
A. Fritz
Abstract We present the Fundamental Plane (FP) of early-type galaxies in the clusters of galaxies RXJ1415.1+3612 at z = 1.013. This is the first detailed FP investigation of cluster early-type galaxies at redshift z = 1. The distant cluster galaxies follow a steeper FP relation compared to the local FP. The change in the slope of the FP can be interpreted as a massdependent evolution. To analyse in more detail the galaxy population in high redshift galaxy clusters at 0.8 < z < 1, we combine our sample with a previous detailed spectroscopic study of 38 early-type galaxies in two distant galaxy clusters, RXJ0152.7,1357 at z = 0.83 and RXJ1226.9+3332 at z = 0.89. For all clusters Gemini/GMOS spectroscopy with high signal-to-noise and intermediate-resolution has been acquired to measure the internal kinematics and stellar populations of the galaxies. From HST/ACS imaging, surface brightness profiles, morphologies and structural parameters were derived for the galaxy sample. The least massive galaxies (M = 2 x 1010 M,) in our sample have experienced their most recent major star formation burst at zform , 1.1. For massive galaxies (M > 2 x 1011 M,) the bulk of their stellar populations have been formed earlier zform , 1.6. Our results confirm previous findings by Jørgensen et al. This suggests that the less massive galaxies in the distant clusters have much younger stellar populations than their more massive counterparts. One explanation is that low-mass cluster galaxies have experienced more extended star formation histories with more frequent bursts of star formation with shorter duration compared to the formation history of high-mass cluster galaxies (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

The evolution of spheroidal galaxies in different environments

ASTRONOMISCHE NACHRICHTEN, Issue 9-10 2009
A. Fritz
Abstract We analyse the kinematic and chemical evolution of 203 distant spheroidal (elliptical and S0) galaxies at 0.2 < z < 0.8 which are located in different environments (rich clusters, low-mass clusters and in the field). VLT/FORS and CAHA/MOSCA spectra with intermediate-resolution have been acquired to measure the internal kinematics and stellar populations of the galaxies. From HST/ACS and WFPC2 imaging, surface brightness profiles and structural parameters were derived for half of the galaxy sample. The scaling relations of the Faber-Jackson relation and Kormendy relation as well as the Fundamental Plane indicate a moderate evolution for the whole galaxy population in each density regime. In all environments, S0 galaxies show a faster evolution than elliptical galaxies. For the cluster galaxies a slight radial dependence of the evolution out to one virial radius is found. Dividing the samples with respect to their mass, a mass dependent evolution with a stronger evolution of lower-mass galaxies (M < 2 × 1011 M,) is detected. Evidence for recent star formation is provided by blue colours and weak [OII] emission or strong H, absorption features in the spectra. The results are consistent with a down-sizing formation scenario which is independent from the environment of the galaxies (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Thermophoresis of axisymmetric aerosol particles along their axes of revolution

AICHE JOURNAL, Issue 1 2009
Yu C. Chang
Abstract The axisymmetric thermophoretic motion of an aerosol particle of revolution in a uniformly prescribed temperature gradient is studied theoretically. The Knudsen number is assumed to be small so that the fluid flow is described by a continuum model. A method of distribution of a set of spherical singularities along the axis of revolution within a prolate particle or on the fundamental plane within an oblate particle is used to find the general solutions for the temperature distribution and fluid velocity field. The jump/slip conditions on the particle surface are satisfied by applying a boundary-collocation technique to these general solutions. Numerical results for the thermophoretic velocity of the particle are obtained with good convergence behavior for various cases. For the axisymmetric thermophoresis of an aerosol spheroid with no temperature jump and frictional slip at its surface, the agreement between our results and the available analytical solutions is very good. The thermophoretic velocity of a spheroid along its axis of revolution in general increases with an increase in its axial-to-radial aspect ratio, but there are exceptions. For most practical cases of a spheroid with a specified aspect ratio, its thermophoretic mobility is not a monotonic function of its relative jump/slip coefficients and thermal conductivity. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source]

Structures in the fundamental plane of early-type galaxies

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2010
D. Fraix-Burnet
ABSTRACT The fundamental plane of early-type galaxies is a rather tight three-parameter correlation discovered more than 20 yr ago. It has resisted both a global and precise physical interpretation despite a consequent number of works, observational, theoretical or using numerical simulations. It appears that its precise properties depend on the population of galaxies in study. Instead of selecting a priori these populations, we propose to objectively construct homologous populations from multivariate analyses. We have undertaken multivariate cluster and cladistic analyses of a sample of 56 low-redshift galaxy clusters containing 699 early-type galaxies, using four parameters: effective radius, velocity dispersion, surface brightness averaged over effective radius and Mg2 index. All our analyses are consistent with seven groups that define separate regions on the global fundamental plane, not across its thickness. In fact, each group shows its own fundamental plane, which is more loosely defined for less diversified groups. We conclude that the global fundamental plane is not a bent surface, but made of a collection of several groups characterizing several fundamental planes with different thicknesses and orientations in the parameter space. Our diversification scenario probably indicates that the level of diversity is linked to the number and the nature of transforming events and that the fundamental plane is the result of several transforming events. We also show that our classification, not the fundamental planes, is universal within our redshift range (0.007,0.053). We find that the three groups with the thinnest fundamental planes presumably formed through dissipative (wet) mergers. In one of them, this(ese) merger(s) must have been quite ancient because of the relatively low metallicity of its galaxies, Two of these groups have subsequently undergone dry mergers to increase their masses. In the k-space, the third one clearly occupies the region where bulges (of lenticular or spiral galaxies) lie and might also have formed through minor mergers and accretions. The two least diversified groups probably did not form by major mergers and must have been strongly affected by interactions, some of the gas in the objects of one of these groups having possibly been swept out. The interpretation, based on specific assembly histories of galaxies of our seven groups, shows that they are truly homologous. They were obtained directly from several observables, thus independently of any a priori classification. The diversification scenario relating these groups does not depend on models or numerical simulations, but is objectively provided by the cladistic analysis. Consequently, our classification is more easily compared to models and numerical simulations, and our work can be readily repeated with additional observables. [source]

Supermassive black hole mass functions at intermediate redshifts from spheroid and AGN luminosity functions

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2006
Naoyuki Tamura
ABSTRACT Redshift evolution of supermassive black hole mass functions (BHMFs) is investigated up to z, 1. BHMFs at intermediate redshifts are calculated in two ways. One way is from early-type galaxy luminosity functions (LFs); we assume an MBH,Lsph correlation at a redshift by considering a passive evolution of Lsph in the local relationship. The resultant BHMFs (spheroid-BHMFs) from LFs of red-sequence galaxies indicate a slight decrease of number density with increasing redshift at MBH, 107.5,8 M,. Since a redshift evolution in slope and zeropoint of the MBH,Lsph relation is unlikely to be capable of making such an evolution in BHMF, the evolution of the spheroid-BHMFs is perhaps due mainly to the decreasing normalization in the galaxy LFs. We also derive BHMFs from LFs of morphologically selected early-type galaxies. The resultant BHMFs are similar to those from the red-sequence galaxies, but show a small discrepancy at z, 1 corresponding to an increase of supermassive black hole (SMBH) number density by ,0.3 dex. We also investigate how spheroid-BHMFs are affected by uncertainties existing in the derivation in detail. The other way of deriving a BHMF is based on the continuity equation for number density of SMBHs and LFs of active galactic nucleus (AGN). The resultant BHMFs (AGN-BHMFs) show no clear evolution out to z= 1 at MBH, 108 M,, but exhibit a significant decrease with redshift in the lower mass range. Interestingly, these AGN-BHMFs are quite different in the range of MBH, 108 M, from those derived by Merloni (2004), where the fundamental plane of black hole activity is exploited. Comparison of the spheroid-BHMFs with the AGN-BHMFs suggests that at MBH, 108 M,, the spheroid-BHMFs are broadly consistent with the AGN-BHMFs out to z, 1. Although the decrease of SMBH number density with redshift suggested by the spheroid-BHMFs is slightly faster than that suggested by the AGN-BHMFs, we presume this to be due at least partly to a selection effect on the LFs of red-sequence galaxies; the colour selection could miss spheroids with blue colours. The agreement between the spheroid-BHMFs and the AGN-BHMFs appears to support that most of the SMBHs are already hosted by massive spheroids at z, 1 and they evolve without significant mass growth since then. [source]

Simulations of the formation and evolution of dwarf galaxies

ASTRONOMISCHE NACHRICHTEN, Issue 9-10 2009
S. Valcke
Abstract We present models of the formation and evolution of isolated dwarf galaxies. The models follow the evolution of an initially homogeneous gas cloud collapsing in a pre-existing dark-matter halo. These simplified initial conditions are supported by the merger trees of isolated dwarf galaxies extracted from the milli-Millennium Simulation. An extensive comparison of the models to observations was made. The models' surface brightness profiles are well fitted by Sérsic profiles and the correlations between the models' Sérsic parameters and luminosity agree with the observations. We have also compared model predictions for the half-light radius Re, central velocity dispersion ,c, broad band colour B , V, metallicity [Z/Z,] versus luminosity relations and for the location relative to the fundamental plane with the available data. In all cases the models give the correct slope, in most cases we also get the zero-point right (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]