The phase space of boxy–peanut and X-shaped bulges in galaxies – I. Properties of non-periodic orbits

Patsis, P. A.; Katsanikas, Matthaios

doi:10.1093/mnras/stu1988

Cited by 45 publications

(50 citation statements)

References 55 publications

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“…However, it is beyond the scope of the present paper to attribute specific orbits, or sets of orbits to the observed peanut shapes encountered in edge-on galaxies or snapshots of N -body models. This was investigated thoroughly in Patsis & Katsanikas (2014b). In this study we emphasize that as long as we have the usual ellipses of the x1 family (or the x1-tree in 3D models according to Skokos et al 2002a) in a rotating bar, we can find a class of boxy 2D and 3D orbits.…”

Section: Discussionmentioning

confidence: 89%

Boxy Orbital Structures in Rotating Bar Models

Chaves-Velasquez

Patsis

Puerari

et al. 2017

ApJ

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We investigate regular and chaotic two-dimensional (2D) and three-dimensional (3D) orbits of stars in models of a galactic potential consisting in a disk, a halo and a bar, to find the origin of boxy components, which are part of the bar or (almost) the bar itself. Our models originate in snapshots of an N -body simulation, which develops a strong bar. We consider three snapshots of the simulation and for the orbital study we treat each snapshot independently, as an autonomous Hamiltonian system. The calculated corotation-to-bar-length ratios indicate that in all three cases the bar rotates slowly, while the orientation of the orbits of the main family of periodic orbits changes along its characteristic. We characterize the orbits as regular, sticky, or chaotic after integrating them for a 10 Gyr period by using the GALI 2 index. Boxiness in the equatorial plane is associated either with quasi-periodic orbits in the outer parts of stability islands, or with sticky orbits around them, which can be found in a large range of energies. We indicate the location of such orbits in diagrams, which include the characteristic of the main family. They are always found about the transition region from order to chaos. By perturbing such orbits in the vertical direction we find a class of 3D non-periodic orbits, which have boxy projections both in their face-on and side-on views.

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Section: Discussionmentioning

confidence: 89%

Boxy Orbital Structures in Rotating Bar Models

Chaves-Velasquez

Patsis

Puerari

et al. 2017

ApJ

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“…For a three-dimensional buckled bar, the backbone orbit family is the x1 tree, i.e., the x1 family with the tree of three-dimensional orbits derived from it (Pfenniger & Friedli 1991). The banana-like orbits were previously suggested as the main backbone of the Xshape and B/PS bulge Skokos et al 2002;Patsis & Katsanikas 2014). Recent work by Portail et al (2015a) classified orbital families in the peanut/X-shaped bulges and suggested brezel-like orbits, whose origin could be closely related to the x1mul2 family (Patsis & Katsanikas 2014), as the main contributor to the X-shape.…”

Section: Implications Of the X-shape In The Galactic Bulgementioning

confidence: 96%

Mapping the Three-Dimensional “X-Shaped Structure” in Models of the Galactic Bulge

Shen

2015

ApJ

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Numerical simulations have shown that the X-shaped structure in the Milky Way bulge can naturally arise from the bar instability and buckling instability. To understand the influence of the buckling amplitude on the morphology of the X-shape, we analyze three self-consistent numerical simulations of barred galaxies with different buckling amplitudes (strong, intermediate and weak). We derive the three-dimensional density with an adaptive kernel smoothing technique. The face-on iso-density surfaces are all elliptical, while in the edge-on view, the morphology of buckled bars transitions with increasing radius, from a central boxy core to a peanut bulge and then to an extended thin bar. Based on these iso-density surfaces at different density levels, we find no clear evidence for a well-defined structure shaped like a letter X. The X-shaped structure is more peanutlike, whose visual perception is probably enhanced by the pinched inner concave iso-density contours. The peanut bulge can reproduce qualitatively the observed bimodal distributions which were used as evidence for the discovery of the X-shape. The central boxy core is shaped like an oblong tablet, extending to ∼ 500 pc above and below the Galactic plane (|b| ∼ 4 • ). From the solar perspective, lines of sight passing through the central boxy core do not show bimodal distributions. This generally agrees with the observations that the double peaks merge at |b| ∼ 4 • − 5 • from the Galactic plane, indicating the presence of a possibly similar structure in the Galactic bulge.

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“…Patsis & Katsanikas (2014a, 2014b) also present a dynamical mechanism for building X-shaped peanuts with families of periodic orbits that are not bifurcations of x1 orbits. It was suggested by Portail et al (2015) that a resonant family of x W : y W : z W =3:0:−5 "brezel" orbits (bottom row of Figure 4) are the backbone of the "X-shaped" structures in their made-to-measure N-body bar models, but we found only 88 "brezels" (1.5% of the bar orbits) in both Models A and B.…”

Section: X1 Orbits and Box Orbitsmentioning

confidence: 99%

A Unified Framework for the Orbital Structure of Bars and Triaxial Ellipsoids

Valluri

Shen

Abbott

et al. 2016

ApJ

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We examine a large random sample of orbits in two self-consistent simulations of N-body bars. Orbits in these bars are classified both visually and with a new automated orbit classification method based on frequency analysis. The well-known prograde x1 orbit family originates from the same parent orbit as the box orbits in stationary and rotating triaxial ellipsoids. However, only a small fraction of bar orbits (∼4%) have predominately prograde motion like their periodic parent orbit. Most bar orbits arising from the x1 orbit have little net angular momentum in the bar frame, making them equivalent to box orbits in rotating triaxial potentials. In these simulations a small fraction of bar orbits (∼7%) are long-axis tubes that behave exactly like those in triaxial ellipsoids: they are tipped about the intermediateaxis owingto the Coriolis force, with the sense of tipping determined by the sign of their angular momentum about the long axis. No orbits parented by prograde periodic x2 orbits are found in the pure bar model, but a tiny population (∼2%) of short-axis tube orbits parented by retrograde x4 orbits are found. When a central point mass representing a supermassive black hole (SMBH) is grown adiabatically at the center of the bar, those orbits that lie in the immediate vicinity of the SMBH are transformed into precessing Keplerian orbits thatbelong to the same major families (short-axis tubes, long-axis tubes and boxes) occupying the bar at larger radii. During the growth of an SMBH,the inflow of mass and outward transport of angular momentum transformsome x1 and long-axis tube orbits into prograde short-axis tubes. This study has important implications for future attempts to constrain the masses of SMBHs in barred galaxies using orbit-based methods like the Schwarzschild orbit superposition scheme and for understanding the observed features in barred galaxies.

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The phase space of boxy–peanut and X-shaped bulges in galaxies – I. Properties of non-periodic orbits

Cited by 45 publications

References 55 publications

Boxy Orbital Structures in Rotating Bar Models

Boxy Orbital Structures in Rotating Bar Models

Mapping the Three-Dimensional “X-Shaped Structure” in Models of the Galactic Bulge

A Unified Framework for the Orbital Structure of Bars and Triaxial Ellipsoids

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