Models for the inner regions of the Galaxy. I

Peters, W.

doi:10.1086/153363

Cited by 79 publications

(49 citation statements)

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“…On the one hand, many lines of evidence now point to the fact that the Milky Way hosts a bar (de Vaucouleurs 1964;Peters 1975;Cohen & Few 1976;Liszt & Burton 1980;Gerhard & Vietri 1986;Mulder & Liem 1986;Binney et al 1991;Nakada et al 1991;Whitelock & Catchpole 1992;Weiland et al 1994;Paczynski et al 1994; of a peanut-shaped bulge (e.g. Li & Shen 2012).…”

Section: Introductionmentioning

confidence: 99%

Separation of stellar populations by an evolving bar: implications for the bulge of the Milky Way

Debattista

Ness

Gonzalez

et al. 2017

Monthly Notices of the Royal Astronomical Society

151

255

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We present a novel interpretation of the previously puzzling different behaviours of stellar populations of the Milky Way's bulge. We first show, by means of pure N -body simulations, that initially co-spatial stellar populations with different in-plane random motions separate when a bar forms. The radially cooler populations form a strong bar, and are vertically thin and peanut-shaped, while the hotter populations form a weaker bar and become a vertically thicker box. We demonstrate that it is the radial, not the vertical, velocity dispersion that dominates this evolution. Assuming that early stellar discs heat rapidly as they form, then both the in-plane and vertical random motions correlate with stellar age and chemistry, leading to different density distributions for metal-rich and metal-poor stars. We then use a high-resolution simulation, in which all stars form out of gas, to demonstrate that this is what happens. When we apply these results to the Milky Way we show that a very broad range of observed trends for ages, densities, kinematics and chemistries, that have been presented as evidence for contradictory paths to the formation of the bulge, are in fact consistent with a bulge which formed from a continuum of disc stellar populations which were kinematically separated by the bar. For the first time we are able to account for the bulge's main trends via a model in which the bulge formed largely in situ. Since the model is generic, we also predict the general appearance of stellar population maps of external edge-on galaxies.

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Section: Introductionmentioning

confidence: 99%

Separation of stellar populations by an evolving bar: implications for the bulge of the Milky Way

Debattista

Ness

Gonzalez

et al. 2017

Monthly Notices of the Royal Astronomical Society

151

255

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“…Among various possible explanations for the noncircular motion, de Vaucouleurs (1964) raised a possibility that the gas responds to a stellar bar potential of the Milky Way. Peters (1975) adopted a model that takes into accout gas flowing along elliptic streamlines caused by a bar-like potential and showed that the general trend of the neutral hydrogen (HI) distribution is explained by the model. Liszt & Burton (1980) developed a tilted bar model that accounts for the observed HI distributions at different latitudes.…”

Section: Introductionmentioning

confidence: 99%

Stochastic non-circular motion and outflows driven by magnetic activity in the Galactic bulge region

Suzuki

Fukui

Torii

et al. 2015

Mon. Not. R. Astron. Soc.

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By performing a global magneto-hydrodynamical simulation for the Milky Way with an axisymmetric gravitational potential, we propose that spatially dependent amplification of magnetic fields possibly explains the observed noncircular motion of the gas in the Galactic center region. The radial distribution of the rotation frequency in the bulge region is not monotonic in general. The amplification of the magnetic field is enhanced in regions with stronger differential rotation, because magnetorotational instability and field-line stretching are more effective. The strength of the amplified magnetic field reaches > ∼ 0.5 mG, and radial flows of the gas are excited by the inhomogeneous transport of angular momentum through turbulent magnetic field that is amplified in a spatially dependent manner. In addition, the magnetic pressuregradient force also drives radial flows in a similar manner. As a result, the simulated position-velocity diagram exhibits a time-dependent asymmetric parallelogram-shape owing to the intermittency of the magnetic turbulence; the present model provides a viable alternative to the bar-potential-driven model for the parallelogram-shape of the central molecular zone. This is a natural extension into the central few 100 pc of the magnetic activity, which is observed as molecular loops at radii from a few 100 pc to 1 kpc. Furthermore, the time-averaged net gas flow is directed outward, whereas the flows are highly time-dependent, which we discuss from a viewpoint of the outflow from the bulge.

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“…Kinematic and dynamical bar models which have been tailored to fit the galactic gas observations (Peters 1975;Liszt & Burton 1980;Rohlfs 1983;Mulder & Liem 1986;Binney et al 1991;Jenkins & Binney 1994;Gerhard 1996;Weiner & Sellwood 1999;Fux 1999) have some (not all) important common elements. The near end is found to occur in the first quadrant of galactic longitude and the more recent gas-dynamical models are "fast", reaching corotation at galactocentric distances of a few kpc.…”

Section: Introductionmentioning

confidence: 99%

Molecular cloud shredding in the Galactic Bar

Liszt¹

2006

A&A

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Seen just outside the innermost regions of the galactic center, the kinematics of molecular gas are dominated by a handful of compact but unusually broad-lined features of enigmatic origin. We show, using previous data, that there is a family of such features whose members are distinguished morphologically by their extreme vertical extension, perpendicular to the inclined plane of the overall gas tilt. Having isolated the features spatially, we mapped them with varying degrees of completeness at high resolution (1 ) in lines of 12 CO, 13 CO and CS. Although very broad profiles exist in some individual beams, more generally we resolved the kinematics into spatial gradients which earlier were smeared in broader beams to form wider lines. The largest apparent velocity gradients are typically with respect to galactic latitude but motions are confined to the range of velocities inside the galactic terminal velocity, indicating that it is the galactic gravitational potential which is being tapped to create the observed kinematics. We interpret the broad-lined features qualitatively in terms of recent hydrodynamical models of gas flow in strongly barred galaxies: standing shocks which occur where gas enters the Galactic dust lane can account for the presence of broad lines over small spatial volumes wherever molecular gas is actually engaged in this process. To interpret the dynamical sequencing of the complex behaviour seen within the broad-line features we discuss how the Sun must be oriented with respect to the bar. In doing so, we identify the nuclear star-forming rings seen in other galaxies with the complex of giant H II regions Sgr A, B, C etc. and show that the kinematics are as expected for a ring of radius 175 pc (for a Sun-center distance of 8.5 kpc) rotating at about 210 km s −1 . Gas having clear and strong outward-directed non-circular motion around l = 0• (the famous "expanding molecular ring") is then associated with the "spray" of incoming gas at the inner ends of the dust lane, defining a more nearly end-on viewing angle for the bar.Using the inferred geometry, we construct a narrative for the behaviour of the feature most completely mapped here, at l = 5.4• , whereby gas basically falls out of the sky and is concentrated into the observed dense, bright molecular core before being shredded and sucked into the inflow of the dust lane 100 pc or more below the nominal galactic equator. From there it is recycled and lifted back into the more nearly equatorial region of the nuclear ring. Of course, the vertical structure of this and the other features, and the overall tilt of the dust lane and inner-galaxy gas layer, all remain to be discussed theoretically.

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Models for the inner regions of the Galaxy. I

Cited by 79 publications

References 0 publications

Separation of stellar populations by an evolving bar: implications for the bulge of the Milky Way

Separation of stellar populations by an evolving bar: implications for the bulge of the Milky Way

Stochastic non-circular motion and outflows driven by magnetic activity in the Galactic bulge region

Molecular cloud shredding in the Galactic Bar

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