Metastudy of the Spiral Structure of Our Home Galaxy

Vallée, J. P.

doi:10.1086/337988

Cited by 113 publications

(120 citation statements)

References 20 publications

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“…Specifically, regarding the Milky Way Galaxy, its general structure has been extensively studied and the latest determinations seem to agree with two grand design symmetric spiral arms, seen on IR and optical, and some other weaker arms, detectable mainly in optical observations (Drimmel & Spergel 2001;Benjamin et al 2005;Drimmel 2000;Drimmel & Spergel 2001;Vallée 2013Vallée , 2002. The weaker arms (branches) have been explained through hydrodynamic simulations as the response to the two-armed stellar pattern.…”

Section: Introductionmentioning

confidence: 86%

The galactic branches as a possible evidence for transient spiral arms

Pérez-Villegas¹,

Gómez²,

Pichardo³

2015

Monthly Notices of the Royal Astronomical Society

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With the use of a background Milky-Way-like potential model, we performed stellar orbital and magnetohydrodynamic (MHD) simulations. As a first experiment, we studied the gaseous response to a bisymmetric spiral arm potential: the widely employed cosine potential model and a self-gravitating tridimensional density distribution based model called PERLAS. Important differences are noticeable in these simulations, while the simplified cosine potential produces two spiral arms for all cases, the more realistic density based model produces a response of four spiral arms on the gaseous disk, except for weak arms -i.e. close to the linear regime-where a two-armed structure is formed. In order to compare the stellar and gas response to the spiral arms, we have also included a detailed periodic orbit study and explored different structural parameters within observational uncertainties. The four armed response has been explained as the result of ultra harmonic resonances, or as shocks with the massive bisymmetric spiral structure, among other. From the results of this work, and comparing the stellar and gaseous responses, we tracked down an alternative explanation to the formation of branches, based only on the orbital response to a self-gravitating spiral arms model. The presence of features such as branches, might be an indication of transiency of the arms.

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Section: Introductionmentioning

confidence: 86%

The galactic branches as a possible evidence for transient spiral arms

Pérez-Villegas¹,

Gómez²,

Pichardo³

2015

Monthly Notices of the Royal Astronomical Society

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“…The interarm spacing at the Sun's location is 2.5 ± 0.3 kpc (Vallée, 2002). The Sun is presently located 0.20 kpc inside its mean Galactic orbital radius and about 0.14 kpc from its perigalactic radius (Sellwood and Binney, 2002).…”

Section: Galactic Dynamicsmentioning

confidence: 97%

Habitable Zones in the Universe

González

2005

Orig Life Evol Biosph

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Abstract. Habitability varies dramatically with location and time in the universe. This was recognized centuries ago, but it was only in the last few decades that astronomers began to systematize the study of habitability. The introduction of the concept of the habitable zone was key to progress in this area. The habitable zone concept was first applied to the space around a star, now called the Circumstellar Habitable Zone. Recently, other, vastly broader, habitable zones have been proposed. We review the historical development of the concept of habitable zones and the present state of the research. We also suggest ways to make progress on each of the habitable zones and to unify them into a single concept encompassing the entire universe.

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“…As a basis we take the same spiral arm model as mentioned above, i.e. the model established by Vallée (2002Vallée ( , 2005, which consists of four logarithmic and symmetrically positioned arms. Around these, we take a Gaussian shape (analogous to the approach in Shaviv 2003) to yield an analytic expression for the source term Q, by summing up over all four arms (n ∈ {1, 2, 3, 4}): with r n = r 0 exp(k(ϕ + ϕ n )), where ϕ n introduces the symmetric rotation of each arm by 90 • , i.e.…”

Section: Source Distributionmentioning

confidence: 99%

Anisotropic diffusion of Galactic cosmic ray protons and their steady-state azimuthal distribution

Effenberger

Fichtner

Scherer

et al. 2012

A&A

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Galactic transport models for cosmic rays involve the diffusive motion of these particles in the interstellar medium. Owing to the large-scale structured Galactic magnetic field, this diffusion is anisotropic with respect to the local field direction. We included this transport effect along with continuous loss processes in a quantitative model of Galactic propagation for cosmic ray protons that is based on stochastic differential equations. We calculated energy spectra at different positions along the Sun's Galactic orbit and compared them to the isotropic diffusion case. The results show that a larger amplitude of variation and different spectral shapes are obtained in the introduced anisotropic diffusion scenario, which in turn emphasizes the need for accurate Galactic magnetic field models.

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Metastudy of the Spiral Structure of Our Home Galaxy

Cited by 113 publications

References 20 publications

The galactic branches as a possible evidence for transient spiral arms

The galactic branches as a possible evidence for transient spiral arms

Habitable Zones in the Universe

Anisotropic diffusion of Galactic cosmic ray protons and their steady-state azimuthal distribution

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