Investigation on fundamental plane of open clusters

2017 ◽  
Vol 13 (S334) ◽  
pp. 331-332
Author(s):  
Xiao-Ying Pang ◽  
Chien-Cheng Lin
Keyword(s):  
Radial Velocity ◽  
Surface Brightness ◽  
Velocity Dispersion ◽  
Open Clusters ◽  
Fundamental Plane ◽  
Average Surface ◽  
Magnitude Diagram ◽  
Formation And Evolution

AbstractThe fundamental plane (FP) is the relation between the surface brightness (I), velocity dispersion (σ) and radius (R). The tilt of FP from the virial plane (R = σ2 I) not only tells the dynamical states of the system but also its formation and evolution. We motivate to looking for an FP in Galactic open clusters (OCs). To form a sample of OCs, we access the most recent DR 14 data from the SDSS/APOGEE2 and the Gaia-ESO survey. Membership of stars is determined via radial velocity and metallicity, plus star’s location in the color-magnitude diagram. Besides the velocity dispersion (σrv) obtained from SDSS/APOGEE2 & Gaia-ESO, the average surface brightness (IKs), and apparent radii (r2) of OCs are taken from known OC catalog. A weak relation is found: log(r2) ∝ -0.34 * log(σ) - 0.08 * IKs. An implication of this FP needs further investigation.

Open Cluster Dynamics via Fundamental Plane

2017 ◽  
Vol 12 (S330) ◽  
pp. 233-234
Author(s):  
Chien-Cheng Lin ◽  
Xiao-Ying Pang
Keyword(s):  
Radial Velocity ◽  
Surface Brightness ◽  
Velocity Dispersion ◽  
Open Cluster ◽  
Dynamical Evolution ◽  
Stellar Dynamics ◽  
Open Clusters ◽  
Fundamental Plane ◽  
Cluster Age ◽  
Internal Effect

AbstractOpen clusters (OCs) are important objects for stellar dynamics studies. The short survival timescale of OCs makes them closely related to the formation of Galactic field stars. We motivate to investigate the dynamical evolution of OCs on the aspect of internal effect and the external influence. Firstly, we make use of the known OC catalog to obtain OCs masses, effective radii. Additionally, we estimate OCs kinematics properties by OC members cross-matched with radial velocity and metallicity from SDSSIV/APOGEE2. We then establish the fundamental plane of OCs based on the radial velocity dispersion, the effective radius, and average surface brightness. The deviation of the fundamental plane from the Virial Plane, so called the tilt, and the r.m.s. dispersion of OCs around the average plane are used to indicate the dynamical status of OCs. Parameters of the fitted plane will vary with cluster age and distance.

scholarly journals The Manifold of Elliptical Galaxies

1987 ◽  
Vol 127 ◽  
pp. 79-88
Author(s):  
S. Djorgovski
Keyword(s):  
Galaxy Formation ◽  
Surface Brightness ◽  
Velocity Dispersion ◽  
Elliptical Galaxies ◽  
Morphological Parameters ◽  
Strong Regularity ◽  
Fundamental Plane ◽  
Global Properties ◽  
Error Bars ◽  
Intrinsic Scatter

Global properties of elliptical galaxies, such as the luminosity, radius, projected velocity dispersion, projected luminosity density, etc., form a two-dimensional family. This “fundamental plane” of elliptical galaxies can be defined by the velocity dispersion and mean surface brightness, and its thickness is presently given by the measurement error-bars only. This is indicative of a strong regularity in the process of galaxy formation. However, all morphological parameters which describe the shape of the distribution of light, and reflect dynamical anisotropies of stars, are completely independent from each other, and independent of the fundamental plane. The M/L ratios show only a small intrinsic scatter in a luminosity range spanning some four orders of magnitude; this suggests a constant fraction of the dark matter contribution in elliptical galaxies.

scholarly journals Redshift evolution of the Fundamental Plane relation in the IllustrisTNG simulation

2020 ◽  
Vol 492 (4) ◽  
pp. 5930-5939 ◽  
Author(s):  
Shengdong Lu ◽  
Dandan Xu ◽  
Yunchong Wang ◽  
Shude Mao ◽  
Junqiang Ge ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Gravitational Constant ◽  
Velocity Dispersion ◽  
Numerical Models ◽  
Zero Point ◽  
Dynamical Mass ◽  
Fundamental Plane ◽  
Hydrodynamical Simulations ◽  
Powerful Constraint ◽  
The Right

ABSTRACT We investigate the Fundamental Plane (FP) evolution of early-type galaxies in the IllustrisTNG-100 simulation (TNG100) from redshift z = 0 to z = 2. We find that a tight plane relation already exists as early as z = 2. Its scatter stays as low as ∼0.08 dex across this redshift range. Both slope parameters b and c (where R ∝ σbIc with R, σ, and I being the typical size, velocity dispersion, and surface brightness) of the plane evolve mildly since z = 2, roughly consistent with observations. The FP residual $\rm Res$ ($\equiv \, a\, +\, b\log \sigma \, +\, c\log I\, -\, \log R$, where a is the zero-point of the FP) is found to strongly correlate with stellar age, indicating that stellar age can be used as a crucial fourth parameter of the FP. However, we find that 4c + b + 2 = δ, where δ ∼ 0.8 for FPs in TNG, rather than zero as is typically inferred from observations. This implies that a tight power-law relation between the dynamical mass-to-light ratio Mdyn/L and the dynamical mass Mdyn (where Mdyn ≡ 5σ2R/G, with G being the gravitational constant) is not present in the TNG100 simulation. Recovering such a relation requires proper mixing between dark matter and baryons, as well as star formation occurring with correct efficiencies at the right mass scales. This represents a powerful constraint on the numerical models, which has to be satisfied in future hydrodynamical simulations.

scholarly journals Open clusters: a program to analyse the color–magnitude diagram with the help of stellar kinematic data

2009 ◽  
Vol 5 (S266) ◽  
pp. 385-385
Author(s):  
Wilton S. Dias ◽  
Thiago Costa Caetano
Keyword(s):  
Radial Velocity ◽  
Proper Motion ◽  
Open Clusters ◽  
Uncertain Parameters ◽  
Kinematic Data ◽  
Magnitude Diagram ◽  
The Mean ◽  
Stellar Kinematic

AbstractWe constructed a program that allows one to use simultaneously and interactively photometric and astrometric stellar data (proper motion) to analyse color–color and color–magnitude diagrams. With this program, we are able to determine, based on photometric membership, the distance and age as well as the mean proper motion and radial velocity of several open clusters which had very uncertain parameters in previous analyses.

scholarly journals Masses of the Hyades white dwarfs

2019 ◽  
Vol 627 ◽  
pp. L8 ◽  
Author(s):  
L. Pasquini ◽  
A. F. Pala ◽  
H.-G. Ludwig ◽  
I. C. Lẽao ◽  
J. R. de Medeiros ◽  
...  
Keyword(s):  
Radial Velocity ◽  
White Dwarfs ◽  
Velocity Dispersion ◽  
Open Clusters ◽  
Gravitational Redshift ◽  
Low Velocity ◽  
Hyades Cluster ◽  
The Masses ◽  
Good Agreement

Context. It is possible to accurately measure the masses of the white dwarfs (WDs) in the Hyades cluster using gravitational redshift, because the radial velocity of the stars can be obtained independently of spectroscopy from astrometry and the cluster has a low velocity dispersion. Aims. We aim to obtain an accurate measurement of the Hyades WD masses by determining the mass-to-radius ratio (M/R) from the observed gravitational redshift, and to compare them with masses derived from other methods. Methods. We analyse archive high-resolution UVES-VLT spectra of six WDs belonging to the Hyades to measure their Doppler shift, from which M/R is determined after subtracting the astrometric radial velocity. We estimate the radii using Gaia photometry as well as literature data. Results. The M/R error associated to the gravitational redshift measurement is about 5%. The radii estimates, evaluated with different methods, are in very good agreement, though they can differ by up to 4% depending on the quality of the data. The masses based on gravitational redshift are systematically smaller than those derived from other methods, by a minimum of ∼0.02 up to 0.05 solar masses. While this difference is within our measurement uncertainty, the fact that it is systematic indicates a likely real discrepancy between the different methods. Conclusions. We show that the M/R derived from gravitational redshift measurements is a powerful tool to determine the masses of the Hyades WDs and could reveal interesting properties of their atmospheres. The technique can be improved by using dedicated spectrographs, and can be extended to other clusters, making it unique in its ability to accurately and empirically determine the masses of WDs in open clusters. At the same time we prove that gravitational redshift in WDs agrees with the predictions of stellar evolution models to within a few percent.

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

2009 ◽  
Vol 5 (H15) ◽  
pp. 81-81
Author(s):  
M. Cappellari ◽  
N. Scott ◽  
K. Alatalo ◽  
L. Blitz ◽  
M. Bois ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Velocity Dispersion ◽  
Scaling Relations ◽  
Early Type ◽  
Stellar Kinematics ◽  
Fundamental Plane ◽  
The Past ◽  
Stellar Velocity ◽  
Integral Field ◽  
Significant Effort

Early-type galaxies (ETGs) satisfy a now classic scaling relation Re ∝ σ1.2eI−0.8e, the Fundamental Plane (FP; Djorgovski & Davis 1987; Dressler et al. 1987), between their size, stellar velocity dispersion and mean surface brightness. A significant effort has been devoted in the past twenty years to try to understand why the coefficients of the relation are not the ones predicted by the virial theorem Re ∝ σ2eI−1e.

scholarly journals Scaling relations of early-type galaxies in the 6dF Galaxy Survey

2009 ◽  
Vol 5 (H15) ◽  
pp. 84-84
Author(s):  
C. Magoulas ◽  
M. Colless ◽  
H. Jones ◽  
J. Mould ◽  
C. Springob
Keyword(s):  
Surface Brightness ◽  
Near Infrared ◽  
Velocity Dispersion ◽  
Three Dimensional ◽  
Gaussian Model ◽  
Early Type ◽  
Fundamental Plane ◽  
Infrared Wavelengths ◽  
Observational Errors ◽  
Intrinsic Scatter

Over 10,000 early-type galaxies from the 6dF Galaxy Survey (6dFGS) (Jones, D. H. et al. (2009), Jones et al. (2004)) have been used to determine the Fundamental Plane at optical and near-infrared wavelengths. We find that a maximum likelihood fit to an explicit three-dimensional Gaussian model for the distribution of galaxies in size, surface brightness and velocity dispersion can precisely account for selection effects, censoring and observational errors, leading to precise and unbiased parameters for the Fundamental Plane and its intrinsic scatter.

scholarly journals The Gaia-ESO Survey: a kinematical and dynamical study of four young open clusters

2018 ◽  
Vol 615 ◽  
pp. A37 ◽  
Author(s):  
L. Bravi ◽  
E. Zari ◽  
G. G. Sacco ◽  
S. Randich ◽  
R. D. Jeffries ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Velocity Dispersion ◽  
Dynamical Evolution ◽  
Young Star ◽  
Open Clusters ◽  
Dynamical Study ◽  
Wide Range ◽  
Residual Gas ◽  
Velocity Dispersions ◽  
Age Range

Context. The origin and dynamical evolution of star clusters is an important topic in stellar astrophysics. Several models have been proposed in order to understand the formation of bound and unbound clusters and their evolution, and they can be tested by examining the kinematical and dynamical properties of clusters over a wide range of ages and masses. Aims. We use the Gaia-ESO Survey products to study four open clusters (IC 2602, IC 2391, IC 4665, and NGC 2547) that lie in the age range between 20 and 50 Myr. Methods. We employ the gravity index γ and the equivalent width of the lithium line at 6708 Å together with effective temperature Teff and the metallicity of the stars in order to discard observed contaminant stars. Then we derive the cluster radial velocity dispersions σc, the total cluster mass Mtot, and the half mass radius rhm. Using the Gaia-DR1 TGAS catalogue, we independently derive the intrinsic velocity dispersion of the clusters from the astrometric parameters of cluster members. Results. The intrinsic radial velocity dispersions derived by the spectroscopic data are higher than those derived from the TGAS data, possibly due to the different masses of the considered stars. Using Mtot and rhm we derive the virial velocity dispersion σvir and we find that three out of four clusters are supervirial. This result is in agreement with the hypothesis that these clusters are dispersing, as predicted by the “residual gas expulsion” scenario. However, recent simulations show that the virial ratio of young star clustersmay be overestimated if it is determined using the global velocity dispersion, since the clusters are not fully relaxed.

scholarly journals Fundamental Plane and Merger Scenario

1999 ◽  
Vol 186 ◽  
pp. 185-188
Author(s):  
K. Bekki
Keyword(s):  
Surface Brightness ◽  
Velocity Dispersion ◽  
Evolutionary Process ◽  
Elliptical Galaxies ◽  
Scaling Relation ◽  
Early Type ◽  
Dynamical Mass ◽  
Fundamental Plane ◽  
Apparent Deviation ◽  
The Mean

The Fundamental Plane (FP) is one of the most important universal relations in early type galaxies because it contains valuable information about the formative and evolutionary process of galaxies (Djorgovski & Davis 1987, Dressler et al. 1987). The commonly used form of the scaling relation in the FP is described as Re = σAIB, where Re, σ, and I are effective radius, central velocity dispersion, and mean surface brightness of elliptical galaxies, respectively. The exponents A, B are considered to be 1.56 ± 0.07 and −0.94 ± 0.09 in the FP derived by K band photometry, respectively, and these values deviate significantly from the values A = 2.0 and B = −1.0 expected from virial theorem (Pahre et al. 1995; Djorgovski, Pahre, & de Carvalho 1996). This apparent deviation requires that the ratio of dynamical mass (M) to luminosity of elliptical galaxies (L) depends on M as M/L ∝ Mα (α = 0.12 ± 0.03 for K band). Possible interpretations for the required dependence of M/L on M are generally considered to be divided into the following two. One is that the required dependence of M/L on M results from the fact that the mean stellar age and metalicity of elliptical galaxies depend systematically on M. The other is that the required dependence reflects the M dependence of structural and kinematical properties of elliptical galaxies (“nonhomology”). Although we should not neglect the importance of stellar populations in generating the M dependence of the M/L (Renzini & Ciotti 1993), we here consider that the origin of the required M dependence of M/L is closely associated with the structural and kinematical properties dependent on M or L in elliptical galaxies.

scholarly journals The stellar mass Fundamental Plane: the virial relation and a very thin plane for slow rotators

2020 ◽  
Vol 494 (4) ◽  
pp. 5148-5160 ◽  
Author(s):  
M Bernardi ◽  
H Domínguez Sánchez ◽  
B Margalef-Bentabol ◽  
F Nikakhtar ◽  
R K Sheth
Keyword(s):  
Dark Matter ◽  
Surface Brightness ◽  
Virial Theorem ◽  
Velocity Dispersion ◽  
Stellar Mass ◽  
Early Type ◽  
Fundamental Plane ◽  
Intrinsic Scatter ◽  
Virial Relation ◽  
Fast Rotating

ABSTRACT Early-type galaxies – slow and fast rotating ellipticals (E-SRs and E-FRs) and S0s/lenticulars – define a Fundamental Plane (FP) in the space of half-light radius Re, enclosed surface brightness Ie, and velocity dispersion σe. Since Ie and σe are distance-independent measurements, the thickness of the FP is often expressed in terms of the accuracy with which Ie and σe can be used to estimate sizes Re. We show that: (1) The thickness of the FP depends strongly on morphology. If the sample only includes E-SRs, then the observed scatter in Re is $\sim 16{{\ \rm per\ cent}}$, of which only $\sim 9{{\ \rm per\ cent}}$ is intrinsic. Removing galaxies with M* < 1011 M⊙ further reduces the observed scatter to $\sim 13{{\ \rm per\ cent}}$ ($\sim 4{{\ \rm per\ cent}}$ intrinsic). The observed scatter increases to $\sim 25{{\ \rm per\ cent}}$ usually quoted in the literature if E-FRs and S0s are added. If the FP is defined using the eigenvectors of the covariance matrix of the observables, then the E-SRs again define an exceptionally thin FP, with intrinsic scatter of only 5 per cent orthogonal to the plane. (2) The structure within the FP is most easily understood as arising from the fact that Ie and σe are nearly independent, whereas the Re−Ie and Re−σe correlations are nearly equal and opposite. (3) If the coefficients of the FP differ from those associated with the virial theorem the plane is said to be ‘tilted’. If we multiply Ie by the global stellar mass-to-light ratio M*/L and we account for non-homology across the population by using Sérsic photometry, then the resulting stellar mass FP is less tilted. Accounting self-consistently for M*/L gradients will change the tilt. The tilt we currently see suggests that the efficiency of turning baryons into stars increases and/or the dark matter fraction decreases as stellar surface brightness increases.

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