Galactic plane

The galactic plane is the plane on which the majority of a disk-shaped galaxy's mass lies. The directions perpendicular to the galactic plane point to the galactic poles. In actual usage, the terms galactic plane and galactic poles usually refer specifically to the plane and poles of the Milky Way, in which Planet Earth is located. Some galaxies are irregular and do not have any well-defined disk. Even in the case of a barred spiral galaxy like the Milky Way, defining the galactic plane is slightly imprecise and arbitrary since the stars are not perfectly coplanar. In 1959, the IAU defined the position of the Milky Way's north galactic pole as exactly RA = , Dec = in the then-used B1950 epoch; in the currently-used J2000 epoch, after precession is taken into account, its position is RA , Dec . This position is in Coma Berenices, near the bright star Arcturus; likewise, the south galactic pole lies in the constellation Sculptor. The "zero of longitude" of galactic coordinates was a

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Overview of the DESI Legacy Imaging Surveys

Alejandro Alvarez, Paul Carter, Johan Comparat, Timothée Guy Olivier Delubac, Arjun Dey, Claudio Gorgoni, Jean-Paul Richard Kneib, Tobias Gabriel Meier, Anand Stéphane Raichoor, Abhijit Saha, Elodie Marie Charlène Savary, David Schlegel, Huanyuan Shan, Kai Zhang

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

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

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

Milky Way

The Milky Way is the galaxy that includes the Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be

Star

A star is an astronomical object comprising a luminous spheroid of plasma held together by self-gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night;

Galaxy

A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. The word is derived from

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