The Simultaneous Formation of Cored, Tangentially Biased, and Kinematically Decoupled Centers in Massive Early-type Galaxies

Rantala, Antti; Johansson, Peter H.; Naab, Thorsten; Thomas, Jens; Frigo, Matteo

doi:10.3847/2041-8213/ab04b1

Cited by 40 publications

(66 citation statements)

References 53 publications

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“…In general, massive early-type galaxies, like these two galaxies, show negative orbital anisotropy parameters in their central regions, indicating tangential orbits; on the contrary, in the outer regions, the orbits appear radial (Thomas et al 2014;Rantala et al 2019). Numerical simulations show that this difference in the stellar orbits might originate if massive elliptical galaxies form from the merging of two progenitors with mass ratios larger than 1{3 (Rantala et al 2019): at the centre of the newborn galaxy, the gravitational torques caused by the merging of the SMBHs of the two parent galaxies cause a reversal of the orbit behaviour, from radial to tangential. Therefore, because we assume below an orbital anisotropy parameter β independent of radius r, we exclude the innermost 2 arcsec in the kinematic profiles of NGC 4486 and NGC 5846.…”

Section: Ngc 4486 and Ngc 5846mentioning

confidence: 89%

Dynamics of DiskMass Survey galaxies in refracted gravity

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Diaferio

Matsakos

et al. 2020

A&A

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We test if Refracted Gravity (RG) can describe the dynamics of disk galaxies without resorting to the presence of dark matter. RG is a classical theory of gravity where the standard Poisson equation is modified with the introduction of the gravitational permittivity, a universal monotonic function of the local mass density. We use the rotation curves and the radial profiles of the stellar velocity dispersion perpendicular to the galactic disks of 30 disk galaxies from the DiskMass Survey (DMS) to determine the gravitational permittivity. RG describes the rotation curves and the vertical velocity dispersions by requiring galaxy mass-to-light ratios in agreement with stellar population synthesis models, and disk thicknesses in agreement with observations, once observational biases are taken into account. Our results rely on setting the three free parameters of the gravitational permittivity for each individual galaxy. However, we show that the differences of these parameters from galaxy to galaxy can in principle be ascribed to statistical fluctuations. We adopt an approximate procedure to estimate a single set of parameters that might properly describe the kinematics of the entire sample and suggest that the gravitational permittivity is indeed a universal function. We finally show that the RG models of the individual rotation curves can only partly describe the radial acceleration relation (RAR), between the observed centripetal acceleration derived from the rotation curve and the Newtonian gravitational acceleration originating from the baryonic mass distribution. Evidently, the RG models underestimate the observed accelerations by 0.1 to 0.3 dex at low Newtonian accelerations. An additional serious problem is the strong correlations, at largely more than 5σ, between the residuals of the RAR models and three radially-dependent properties of the galaxies, whereas the DMS data show considerably less significant correlations, at more than 4σ, for only two of these quantities. These correlations might originate the non-null intrinsic scatter of the RG models, at odds with the observed intrinsic scatter of galaxy samples, different from DMS, which is consistent with zero. Further investigations are required to assess if these discrepancies in the RAR originate from the DMS sample, which might not be ideal for deriving the RAR, or if they are genuine failures of RG.

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Section: Ngc 4486 and Ngc 5846mentioning

confidence: 89%

Dynamics of DiskMass Survey galaxies in refracted gravity

Cesare

Diaferio

Matsakos

et al. 2020

A&A

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“…Tsatsi et al (2015) showed that kpc-sized KDCs can also form in a prograde merger of two disk galaxies during which reactive forces create short-lived reversal of the orbital spin. Rantala et al (2019) shows that KDCs may also arise from orbit reversals of the central SMBH caused by gravitational torques from expelled material in the dissipationless merger of two massive ETGs. For binary mergers of massive ETGs (each M * > 8 × 10 10 M ) with very massive SMBHs (each > 10 9 M ), they even find multiple KDCs, similar to what we found in FCC 47, however, the simulated KDCs still share a single rotation axis aligned with the minor axis of the galaxy.…”

Section: Evidence For Merger History Of Fcc 47mentioning

confidence: 99%

“…Large IFS surveys such as SAURON (Bacon et al 2001) or ATLAS3D have revealed that a significant fraction of ETGs have a KDC, especially slow-rotators ). Simulations suggest that the formation of KDCs is triggered by major mergers (Jesseit et al 2007;Bois et al 2011;Tsatsi et al 2015), but once formed, a KDC can be stable over a long time in a triaxial galaxy (van den Bosch et al 2008;Rantala et al 2019). KDCs are not rare in slow-rotating galaxies like FCC 47, however two decoupled components certainly are.…”

Section: Galaxy Lightmentioning

confidence: 99%

Constraining nuclear star cluster formation using MUSE-AO observations of the early-type galaxy FCC 47

Fahrion

Lyubenova

Ven

et al. 2019

A&A

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Context. Nuclear star clusters (NSCs) are found in at least 70% of all galaxies, but their formation path is still unclear. In the most common scenarios, NSCs form in-situ from the galaxy's central gas reservoir, through merging of globular clusters (GCs), or through a combination of the two. Aims. As the scenarios pose different expectations for angular momentum and stellar population properties of the NSC in comparison to the host galaxy and the GC system, it is necessary to characterise the stellar light, NSC and GCs simultaneously. The large NSC (r eff = 66 pc) and rich GC system of the early-type Fornax cluster galaxy FCC 47 (NGC 1336) render this galaxy an ideal laboratory to constrain NSC formation. Methods. Using MUSE science verification data assisted by adaptive optics, we obtained maps for the stellar kinematics and for stellar-population properties of FCC 47. We extracted the spectra of the central NSC and determined line-of-sight velocities of 24 GCs and metallicities of five. Results. FCC 47 shows two decoupled components (KDCs): a rotating disk and the NSC. Our orbit-based dynamical Schwarzschild model revealed that the NSC is a distinct kinematic feature and it constitutes the peak of metallicity and old ages in the galaxy. The main body consists of two counter-rotating populations and is dominated by a more metal-poor population. The GC system is bimodal with a dominant metal-poor population and the total GC system mass is ∼ 17% of the NSC mass (∼ 7 × 10 8 M ). Conclusions. The rotation, high metallicity and high mass of the NSC cannot be uniquely explained by GC-inspiral and most likely requires additional, but quickly quenched, in-situ formation. The presence of two KDCs most probably are evidence of a major merger that has altered the structure of FCC 47 significantly, indicating the important role of galaxy mergers in forming the complex kinematics in the galaxy-NSC system.

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“…A more readily observable kinematic consequence is a possibility of KDC formation from the interaction between the SMBHs and the surrounding stellar body. As SMBHs pass and exert torques on each other, there is a switch of the angular momentum between the SMBHs (and stars under their direct gravitational influence) and the rest of the galaxy, possibly producing nested KDCs (Rantala et al 2019). Because the core formation is enhanced if the SMBHs are massive, and because such SMBHs live in massive galaxies (e.g.…”

Section: Formation Of Stellar Coresmentioning

confidence: 99%

Formation channels of slowly rotating early-type galaxies

Krajnović

Ural

Küntschner

et al. 2020

A&A

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We study the evidence for a diversity of formation processes in early-type galaxies by presenting the first complete volume-limited sample of slow rotators with both integral-field kinematics from the ATLAS 3D Project and high spatial resolution photometry from the Hubble Space Telescope. Analysing the nuclear surface brightness profiles of 12 newly imaged slow rotators, we classify their light profiles as core-less, and place an upper limit to the core size of about 10 pc. Considering the full magnitude and volumelimited ATLAS 3D sample, we correlate the presence or lack of cores with stellar kinematics, including the proxy for the stellar angular momentum (λ Re ) and the velocity dispersion within one half-light radius (σ e ), stellar mass, stellar age, α-element abundance, and age and metallicity gradients. More than half of the slow rotators have core-less light profiles, and they are all less massive than 10 11 M . Core-less slow rotators show evidence for counter-rotating flattened structures, have steeper metallicity gradients, and a larger dispersion of gradient values (∆[Z/H] = −0.42 ± 0.18) than core slow rotators (∆[Z/H] = −0.23 ± 0.07). Our results suggest that core and core-less slow rotators have different assembly processes, where the former, as previously discussed, are the relics of massive dissipation-less merging in the presence of central supermassive black holes. Formation processes of core-less slow rotators are consistent with accretion of counter-rotating gas or gas-rich mergers of special orbital configurations, which lower the final net angular momentum of stars, but support star formation. We also highlight core fast rotators as galaxies that share properties of core slow rotators (i.e. cores, ages, σ e , and population gradients) and core-less slow rotators (i.e. kinematics, λ Re , mass, and larger spread in population gradients). Formation processes similar to those for core-less slow rotators can be invoked to explain the assembly of core fast rotators, with the distinction that these processes form or preserve cores.

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The Simultaneous Formation of Cored, Tangentially Biased, and Kinematically Decoupled Centers in Massive Early-type Galaxies

Cited by 40 publications

References 53 publications

Dynamics of DiskMass Survey galaxies in refracted gravity

Dynamics of DiskMass Survey galaxies in refracted gravity

Constraining nuclear star cluster formation using MUSE-AO observations of the early-type galaxy FCC 47

Formation channels of slowly rotating early-type galaxies

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