Plan galactique

Résumé

En astronomie, le plan galactique est un plan situé au milieu de la zone (appelée disque) où se trouve la plus grande partie des étoiles d'une galaxie de forme aplatie, comme le sont les galaxies spirales. Ce plan passe par le centre de masse de la galaxie. Ce plan galactique est orienté, avec un côté nord et un côté sud. Dans le cas de la Voie lactée :

le pôle nord galactique correspond à la direction de la constellation de la Chevelure de Bérénice, près de l'étoile α Bootis (Arcturus) ;
le pôle sud galactique correspond à la direction de la constellation du Sculpteur, près de l'étoile β Ceti (Deneb Kaitos, de la Baleine).

Annexes Articles connexes *Système de coordonnées galactiques Lien externe

Images du plan galactique sur différentes longueurs d'onde

Catégorie:Galaxie

Source officielle

https://fr.wikipedia.org/wiki/Plan_galactique

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The DESI Legacy Imaging Surveys (http://legacysurvey.org/) are a combination of three public projects (the Dark Energy Camera Legacy Survey, the Beijing-Arizona Sky Survey, and the Mayall z-band Legacy Survey) that will jointly image approximate to 14,000 deg(2) of the extragalactic sky visible from the northern hemisphere in three optical bands (g, r, and z) using telescopes at the Kitt Peak National Observatory and the Cerro Tololo Inter-American Observatory. The combined survey footprint is split into two contiguous areas by the Galactic plane. The optical imaging is conducted using a unique strategy of dynamically adjusting the exposure times and pointing selection during observing that results in a survey of nearly uniform depth. In addition to calibrated images, the project is delivering a catalog, constructed by using a probabilistic inference-based approach to estimate source shapes and brightnesses. The catalog includes photometry from the grz optical bands and from four mid-infrared bands (at 3.4, 4.6, 12, and 22 mu m) observed by the Wide-field Infrared Survey Explorer satellite during its full operational lifetime. The project plans two public data releases each year. All the software used to generate the catalogs is also released with the data. This paper provides an overview of the Legacy Surveys project.

IOP PUBLISHING LTD2019

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Stellar kinematics using a third integral of motion: method and application on the Andromeda galaxy

Olga Tihhonova

We probe the feasibility of describing the structure of a multicomponent axisymmetric galaxy with a dynamical model based on the Jeans equations while taking into account a third integral of motion. We demonstrate that using the third integral in the form derived by G. Kuzmin, it is possible to calculate the stellar kinematics of a galaxy from the Jeans equations by integrating the equations along certain characteristic curves. In the cases where the third integral ofmotion does not describe the system exactly, the derived kinematics would describe the galaxy only approximately. We apply our method to the Andromeda galaxy, for which the mass distribution is relatively firmly known. We are able to reproduce the observed stellar kinematics of the galaxy rather well. The calculated model suggests that the velocity dispersion ratios sigma(2)(z) /sigma(2)(R) of M31 decrease with increasing R. Moving away from the galactic plane, sigma(2)(z) /sigma(2)(R) remains the same. The velocity dispersions sigma(2)(theta) and sigma(2)(R) are roughly equal in the galactic plane.

Oxford Univ Press2016

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Low-l CMB analysis and inpainting

Anaïs Marie Rassat, Jean-Luc Starck

Reconstructing the cosmic microwave background (CMB) in the Galactic plane is extremely difficult due to the dominant foreground emissions such as dust, free-free or synchrotron. For cosmological studies, the standard approach consists in masking this area where the reconstruction is insufficient. This leads to difficulties for the statistical analysis of the CMB map, especially at very large scales (to study for instance the low quadrupole, integrated Sachs Wolfe effect, axis of evil, etc.). We investigate how well some inpainting techniques can recover the low-l spherical harmonic coefficients. We introduce three new inpainting techniques based on three different kinds of priors: sparsity, energy, and isotropy, which we compare. We show that sparsity and energy priors can lead to extremely high-quality reconstruction, within 1% of the cosmic variance for a mask with a sky coverage larger than 80%.

Edp Sciences S A2013

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