An Observational Approach to the Problem of Spiral Structure

Dixon, M. E.

doi:10.1086/150856

“…As a result, the ridge line of bright young stars and H ii regions that "are strung out like pearls along the arms" (Baade 1963) is offset forward of the dust lanes. Our picture of how spiral density waves stimulate star formation and hence are traced by young stars is discussed in Roberts (1969); Dixon (1971); Shu et al (1973) and Roberts et al (1975) and is reviewed in Toomre (1977b).…”

Section: The Response Of Gas To a Rotating Bar: Construction Of Outer...mentioning

confidence: 99%

Secular Evolution in Disk Galaxies

Kormendy¹

2013

Preprint

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Self-gravitating systems evolve toward the most tightly bound configuration that is reachable via the evolution processes that are available to them. They do this by spreading -the inner parts shrink while the outer parts expand -provided that some physical process efficiently transports energy or angular momentum outward. The reason is that self-gravitating systems have negative specific heats. As a result, the evolution of stars, star clusters, protostellar and protoplanetary disks, black hole accretion disks and galaxy disks are fundamentally similar. How evolution proceeds then depends on the evolution processes that are available to each kind of self-gravitating system. These processes and their consequences for galaxy disks are the subjects of my lectures and of this Canary Islands Winter School.

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“…This point is mentioned by Grosbøl & Patsis (1998), but they failed to observe such a crossing. Dixon (1971) proposed that observations in the B and V bands could allow the variation of stellar age across an arm to be determined, and that corotation should correspond to the radius at which this trend reverses angular direction. Puerari & Dottori (1997) attempted to locate corotation in two galaxies by this method, performing a Fourier analysis on observations in B and I bands.…”

Section: Locating the Corotation Radius In Galaxiesmentioning

confidence: 99%

Constraining corotation from shocks in tightly wound spiral galaxies

Gittins¹,

Clarke²

2004

Monthly Notices of the Royal Astronomical Society

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We present a new method for estimating the corotation radius in tightly wound spiral galaxies, through analysis of the radial variation of the offset between arms traced by the potential (P‐arms) and those traced by dust (D‐arms). We have verified the predictions of semi‐analytical theory through hydrodynamical simulations and have examined the uniqueness of the galactic parameters that can be deduced by this method. We find that if the range of angular offsets measured at different radii in a galaxy is greater than around π/4, it is possible to locate the radius of corotation to within ∼25 per cent. We argue that the relative location of the P‐ and D‐arms provides more robust constraints on the galactic parameters than can be inferred from regions of enhanced star formation (SF‐arms), as interpretation of the latter involves uncertainties due to reddening and the assumed star formation law. We thus stress the importance of K‐band studies of spiral galaxies.

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“…As a result, the ridge line of bright young stars and H ii regions that "are strung out like pearls along the arms" (Baade 1963) is offset forward of the dust lanes. Our picture of how spiral density waves stimulate star formation and hence are traced by young stars is discussed in Roberts (1969); Dixon (1971); Shu et al (1973) and Roberts et al (1975) and is reviewed in Toomre (1977b).…”

mentioning

confidence: 99%

Secular evolution in disk galaxies

Kormendy¹

2013

Secular Evolution of Galaxies

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Self-gravitating systems evolve toward the most tightly bound configuration that is reachable via the evolution processes that are available to them. They do this by spreading -the inner parts shrink while the outer parts expand -provided that some physical process efficiently transports energy or angular momentum outward. The reason is that self-gravitating systems have negative specific heats. As a result, the evolution of stars, star clusters, protostellar and protoplanetary disks, black hole accretion disks and galaxy disks are fundamentally similar. How evolution proceeds then depends on the evolution processes that are available to each kind of self-gravitating system. These processes and their consequences for galaxy disks are the subjects of my lectures and of this Canary Islands Winter School.I begin with a review of the formation, growth and death of bars. Then I review the slow ("secular") rearrangement of energy, angular momentum, and mass that results from interactions between stars or gas clouds and collective phenomena such as bars, oval disks, spiral structure and triaxial dark halos. The "existence-proof" phase of this work is largely over: we have a good heuristic understanding of how nonaxisymmetric structures rearrange disk gas into outer rings, inner rings and stuff dumped onto the center. The results of simulations correspond closely to the morphology of barred and oval galaxies. Gas that is transported to small radii reaches high densities. Observations confirm that many barred and oval galaxies have dense central concentrations of gas and star formation. The result is to grow, on timescales of a few Gyr, dense central components that are frequently mistaken for classical (elliptical-galaxy-like) bulges but that were grown slowly out of the disk (not made rapidly by major mergers). The resulting picture of secular galaxy evolution accounts for the richness observed in galaxy structure.

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An Observational Approach to the Problem of Spiral Structure

Cited by 17 publications

References 0 publications

Secular Evolution in Disk Galaxies

Secular Evolution in Disk Galaxies

Constraining corotation from shocks in tightly wound spiral galaxies

Secular evolution in disk galaxies

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