2,037 research outputs found
Double Bubbles Minimize
The classical isoperimetric inequality in R^3 states that the surface of
smallest area enclosing a given volume is a sphere. We show that the least area
surface enclosing two equal volumes is a double bubble, a surface made of two
pieces of round spheres separated by a flat disk, meeting along a single circle
at an angle of 120 degrees.Comment: 57 pages, 32 figures. Includes the complete code for a C++ program as
described in the article. You can obtain this code by viewing the source of
this articl
The Real Estate Investment Trust: State Law Problems
We present a map of the three-dimensional (3D) distribution of dust in the Orion complex. Orion is the closest site of high-mass star formation, making it an excellent laboratory for studying the interstellar medium and star formation. We used data from the Gaia-TGAS catalogue combined with photometry from 2MASS and WISE to get the distances and extinctions of individual stars in the vicinity of the Orion complex. We use a Gaussian process and adopt a non-parametric method to infer the probability distribution function of the dust densities at arbitrary points throughout the region. We map the dust distribution towards different parts of the Orion complex. We find that the distance and depth of the cloud are compatible with other recent works, which show that the method can be applicable to local molecular clouds to map their 3D dust distribution. We also demonstrate the danger of only using colours of stars to derive their extinctions without considering further physical constraints, such as the colour-magnitude diagram (CMD)
An Empirical Relation between Sodium Absorption and Dust Extinction
Dust extinction and reddening are ubiquitous in astronomical observations and
are often a major source of systematic uncertainty. We present here a study of
the correlation between extinction in the Milky Way and the equivalent width of
the NaI D absorption doublet. Our sample includes more than 100 high resolution
spectra from the KECK telescopes and nearly a million low resolution spectra
from the Sloan Digital Sky Survey (SDSS). We measure the correlation to
unprecedented precision, constrain its shape, and derive an empirical relation
between these quantities with a dispersion of order 0.15 magnitude in E(B-V).
From the shape of the curve of growth we further show that a typical sight line
through the Galaxy, as seen within the SDSS footprint, crosses about three dust
clouds. We provide a brief guide on how to best estimate extinction to
extragalactic sources such as supernovae, using the NaI D absorption feature,
under a variety of circumstances.Comment: MNRAS accepte
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