THE VIRIAL RELATION AND INTRINSIC SHAPE OF EARLY-TYPE GALAXIES

Context. Early-type galaxies (ETGs) are found to follow a wide variety of merger and accretion histories in cosmological simulations. Aims. We characterize the photometric and kinematic properties of simulated ETG stellar halos, and compare them to the observations. Methods. We selected a sample of 1114 ETGs in the TNG100 simulation and 80 in the higher-resolution TNG50. These ETGs span a stellar mass range of 1010.3 − 1012 M⊙ and they were selected within the range of g − r colour and λ-ellipticity diagram populated by observed ETGs. We determined photometric parameters, intrinsic shapes, and kinematic observables in their extended stellar halos. We compared the results with central IFU kinematics and ePN.S planetary nebula velocity fields at large radii, studying the variation in kinematics from center to halo, and connecting it to a change in the intrinsic shape of the galaxies. Results. We find that the simulated galaxy sample reproduces the diversity of kinematic properties observed in ETG halos. Simulated fast rotators (FRs) divide almost evenly in one third having flat λ profiles and high halo rotational support, a third with gently decreasing profiles, and another third with low halo rotation. However, the peak of rotation occurs at larger R than in observed ETG samples. Slow rotators (SRs) tend to have increased rotation in the outskirts, with half of them exceeding λ = 0.2. For M* > 1011.5 M⊙ halo rotation is unimportant. A similar variety of properties is found for the stellar halo intrinsic shapes. Rotational support and shape are deeply related: the kinematic transition to lower rotational support is accompanied by a change towards rounder intrinsic shape. Triaxiality in the halos of FRs increases outwards and with stellar mass. Simulated SRs have relatively constant triaxiality profiles. Conclusions. Simulated stellar halos show a large variety of structural properties, with quantitative but no clear qualitative differences between FRs and SRs. At the same stellar mass, stellar halo properties show a more gradual transition and significant overlap between the two families, despite the clear bimodality in the central regions. This is in agreement with observations of extended photometry and kinematics.

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SDSS-IV MaNGA: The Intrinsic Shape of Slow Rotator Early-type Galaxies

The Astrophysical Journal ◽

10.3847/2041-8213/aad54b ◽

2018 ◽

Vol 863 (2) ◽

pp. L19 ◽

Cited By ~ 9

Author(s):

Hongyu Li ◽

Shude Mao ◽

Michele Cappellari ◽

Mark T. Graham ◽

Eric Emsellem ◽

...

Keyword(s):

Early Type ◽

Intrinsic Shape

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The ATLAS 3D project – XXIV. The intrinsic shape distribution of early-type galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stu1603 ◽

2014 ◽

Vol 444 (4) ◽

pp. 3340-3356 ◽

Cited By ~ 71

Author(s):

Anne-Marie Weijmans ◽

P. T. de Zeeuw ◽

Eric Emsellem ◽

Davor Krajnović ◽

Pierre-Yves Lablanche ◽

...

Keyword(s):

Early Type ◽

Shape Distribution ◽

Intrinsic Shape

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Recovering the intrinsic shape of early-type galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1111/j.1365-2966.2009.15177.x ◽

2009 ◽

Vol 398 (3) ◽

pp. 1117-1128 ◽

Cited By ~ 52

Author(s):

Remco C. E. van den Bosch ◽

Glenn van de Ven

Keyword(s):

Early Type ◽

Intrinsic Shape

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

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1064 ◽

2020 ◽

Vol 494 (4) ◽

pp. 5148-5160 ◽

Cited By ~ 1

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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Some results of the Barbier-Chalonge-Divan system of stellar classification

Symposium - International Astronomical Union ◽

10.1017/s0074180900053250 ◽

1966 ◽

Vol 24 ◽

pp. 77-90 ◽

Cited By ~ 1

Author(s):

D. Chalonge

Keyword(s):

Early Type ◽

Parameter System ◽

Early Type Stars ◽

Two Parameter

Several years ago a three-parameter system of stellar classification has been proposed (1, 2), for the early-type stars (O-G): it was an improvement on the two-parameter system described by Barbier and Chalonge (3).

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