A New Channel for the Formation of Kinematically Decoupled Cores in Early-Type Galaxies

Tsatsi, Athanasia; Macciò, Andrea V.; Ven, Glenn van de; Moster, Benjamin P.

doi:10.1088/2041-8205/802/1/l3

Cited by 41 publications

(41 citation statements)

References 36 publications

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“…This was expected: several studies have pointed out that major mergers are the most likely mechanism for generating KDC galaxies (e.g. Balcells & González 1999;McDermid et al 2006;Tsatsi et al 2015) and minor mergers can produce dynamically cold inner components such as co-and counter-rotating inner discs, bars, rings, or pseudorings (Eliche-Moral et al 2011;Mapelli et al 2015).…”

Section: Estimates Of the Maximum Rotational Velocity And Central Velmentioning

confidence: 92%

Formation of S0 galaxies through mergers

Tapia

Eliche‐Moral

Aceves

et al. 2017

A&A

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Context. Lenticular (S0) galaxies are known to derive from spiral galaxies. The fact that S0s nearly obey the Tully-Fisher relation (TFR) at z ∼ 0 (as spirals have done in the last ∼9 Gyr) is considered an argument against their major-merger origin because equal mergers of two disc galaxies produce remnants that are outliers of the TFR. Aims. We explore whether a scenario that combines an origin by mergers at z ∼ 1.8 − 1.5 with a subsequent passive evolution of the resulting S0 remnants since z ∼ 0.8-1 is compatible with observational data of S0s in the TFR both at z ∼ 0.8 and z ∼ 0. Methods. We studied a set of major and minor merger experiments from the GalMer database that generate massive S0 remnants that are dynamically relaxed and have realistic properties. We analysed the location of these remnants in the photometric and stellar TFRs assuming that they correspond to z ∼ 0.8 galaxies. We then estimated their evolution in these planes over the last ∼ 7 Gyr considering that they have evolved passively in isolation. The results were compared with data of real S0s and spirals at different redshifts. We also tested how the use of V circ or V rot,max affects the results. Results. Just after ∼ 1-2 Gyr of coalescence, major mergers generate S0 remnants that are outliers of the local photometric and stellar TFRs (as already stated in previous studies), in good agreement with observations at z ∼ 0.8. After ∼ 4 -7 Gyr of passive evolution in isolation, the S0 remnants move towards the local TFR, although the initial scatter among them persists. This scatter is sensitive to the indicator used for the rotation velocity: V circ values yield a lower scatter than when V rot,max values are considered instead. In the planes involving V rot,max , a clear segregation of the S0 remnants in terms of the spin-orbit coupling of the model is observed, in which the remnants of retrograde encounters overlap with local S0s hosting counter-rotating discs. The location of the S0 remnants at z ∼ 0 agrees well with the observed distribution of local S0 galaxies in the σ 0 -M K , V circ -σ 0 , and V rot,max -σ 0 planes. Conclusions. Massive S0 galaxies may have been formed through major mergers that occurred at high redshift and have later evolved towards the local TFR through passive evolution in relative isolation, a mechanism that would also contribute to the scatter observed in this relation.

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Section: Estimates Of the Maximum Rotational Velocity And Central Velmentioning

confidence: 92%

Formation of S0 galaxies through mergers

Tapia

Eliche‐Moral

Aceves

et al. 2017

A&A

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“…In order to connect the intrinsic mass and orbital distribution of our simulated merger remnant galaxies with observable properties, we created two-dimensional mock stellar mass and stellar kinematic maps following the method described in Tsatsi et al (2015). Stellar particles were projected along a chosen viewing angle and then binned on a regular grid centered on the baryonic center of mass of the galaxy.…”

Section: Extracting Mock Observational Datamentioning

confidence: 99%

CALIFA reveals prolate rotation in massive early-type galaxies: A polar galaxy merger origin?

Tsatsi

Lyubenova

Ven

et al. 2017

A&A

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We present new evidence for eight early-type galaxies (ETGs) from the CALIFA Survey that show clear rotation around their major photometric axis ("prolate rotation"). These are LSBCF560-04, NGC 0647, NGC 0810, NGC 2484, NGC 4874, NGC 5216, NGC 6173, and NGC 6338. Including NGC 5485, a known case of an ETG with stellar prolate rotation, as well as UGC 10695, a further candidate for prolate rotation, we report ten CALIFA galaxies in total that show evidence for such a feature in their stellar kinematics. Prolate rotators correspond to ∼9% of the volume-corrected sample of CALIFA ETGs, a fraction much higher than previously reported. We find that prolate rotation is more common (∼27%) among the most massive ETGs (M * 2 × 10 11 M ). We investigated the implications of these findings by studying N-body merger simulations, and we show that a prolate ETG with rotation around its major axis could be the result of a major polar merger, with the amplitude of prolate rotation depending on the initial bulgeto-total stellar mass ratio of its progenitor galaxies. Additionally, we find that prolate ETGs resulting from this formation scenario show a correlation between their stellar line-of-sight velocity and higher order moment h 3 , opposite to typical oblate ETGs, as well as a double peak of their stellar velocity dispersion along their minor axis. Finally, we investigated the origin of prolate rotation in polar galaxy merger remnants. Our findings suggest that prolate rotation in massive ETGs might be more common than previously expected, and can help toward a better understanding of their dynamical structure and formation origin.

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“…If one did describe the orbit with an ellipse, the parameters of the ellipse would change between every time step due to interactions with other galaxies. Therefore, the initial orbital parameters are a very poor tracer of the final orbital parameters (see also Tsatsi et al 2015). The final orbital parameters are better traced by ∆t, where a more tangential orbit has a higher value of ∆t.…”

Section: Starburst Efficiency With Hot Halomentioning

confidence: 99%

Star formation in mergers with cosmologically motivated initial conditions

Karman

Macciò

Kannan

et al. 2015

Mon. Not. R. Astron. Soc.

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We use semi-analytic models and cosmological merger trees to provide the initial conditions for multi-merger numerical hydrodynamic simulations, and exploit these simulations to explore the effect of galaxy interaction and merging on star formation (SF). We compute numerical realisations of twelve merger trees from z = 1.5 to z = 0. We include the effects of the large hot gaseous halo around all galaxies, following recent obervations and predictions of galaxy formation models. We find that including the hot gaseous halo has a number of important effects. Firstly, as expected, the star formation rate on long timescales is increased due to cooling of the hot halo and refuelling of the cold gas reservoir. Secondly, we find that interactions do not always increase the SF in the long term. This is partially due to the orbiting galaxies transferring gravitational energy to the hot gaseous haloes and raising their temperature. Finally we find that the relative size of the starburst, when including the hot halo, is much smaller than previous studies showed. Our simulations also show that the order and timing of interactions are important for the evolution of a galaxy. When multiple galaxies interact at the same time, the SF enhancement is less than when galaxies interact in series. All these effects show the importance of including hot gas and cosmologically motivated merger trees in galaxy evolution models.

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A New Channel for the Formation of Kinematically Decoupled Cores in Early-Type Galaxies

Cited by 41 publications

References 36 publications

Formation of S0 galaxies through mergers

Formation of S0 galaxies through mergers

CALIFA reveals prolate rotation in massive early-type galaxies: A polar galaxy merger origin?

Star formation in mergers with cosmologically motivated initial conditions

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