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Dust Maps

Usage

julia> dustmap = SFD98Map();

julia> dustmap(0, 2)
0.020303287464050277

julia> l = range(-π, π, length=5)
-3.141592653589793:1.5707963267948966:3.141592653589793

julia> b = range(-π/2, π/2, length=5)
-1.5707963267948966:0.7853981633974483:1.5707963267948966

julia> [dustmap(l[i], b[j]) for i in 1:length(l), j in 1:length(b)]
5×5 Matrix{Float64}:
 0.0159853  0.105782    1.40486  0.0158918  0.0119615
 0.0159853  0.0268289   3.47788  0.0654852  0.0119615
 0.0159853  0.0343457  99.6976   0.103875   0.0119615
 0.0159853  0.0432165   2.60569  0.0178195  0.0119615
 0.0159853  0.105782    1.40486  0.0158918  0.0119615
Example block output

Advanced Usage

Our dust maps also have native support for Unitful.jl, Measurements.jl, and SkyCoords.jl.

julia> using Measurements, Unitful

julia> using SkyCoords: GalCoords

julia> using Unitful: °

julia> l = 45°; b = 0°;

julia> dustmap = SFD98Map();

julia> dustmap(l, b)
6.4290331211742355 mag

julia> l = l ± 0.1°; b = b ± 0.3°;

julia> dustmap(l, b)
6.4 ± 5.7 mag

julia> dustmap(GalCoords(l, b))
6.4 ± 5.7

API/Reference

DustExtinction.SFD98Map — Type
SFD98Map([mapdir])

Schlegel, Finkbeiner and Davis (1998) dust map.

The first time this is constructed, the data files required will be downloaded and stored in a directory following the semantics of DataDeps.jl. To avoid being asked to download the files, set the environment variable DATADEPS_ALWAYS_ACCEPT to true. You can also provide the directory of the two requisite files manually instead of relying on DataDeps.jl. Internally, this type keeps the FITS files defining the map open, speeding up repeated queries for E(B-V) values.

References

Schlegel, Finkbeiner and Davis (1998)

source
(dustmap::SFD98Map)(l::Real, b::Real)
(dustmap::SFD98Map)(l::Quantity, b::Quantity)
(dustmap::SFD98Map)(s::SkyCoords.AbstractSkyCoords)

Get E(B-V) value from a SFD98Map instance at galactic coordinates (l, b), given in radians. Uses bilinear interpolation between pixel values. If l and b are Unitful.Quantity they will be converted to radians and the output will be given as UnitfulAstro.mag. If a SkyCoords.AbstractSkyCoords is passed, it will be converted to galactic coordinates (requires Julia >= v1.9).

Example

julia> using DustExtinction

julia> m = SFD98Map();

julia> m(1, 2)
0.013439524544325624

And now we can use a SkyCoords type as input:

julia> using SkyCoords

julia> s = GalCoords(1, 2);

julia> m(s) == m(1, 2)
true

Use broadcasting to get E(B-V) values for multiple coordinates:

julia> l = 0:0.5:2; b = 0:0.5:2;

julia> m.(l, b)
5-element Vector{Float64}:
 99.69757461547852
  0.10180447359074371
  0.019595484241066132
  0.010238757633890877
  0.01862100327420125

And now we can add angle units:

julia> using Unitful

julia> m.(l * u"rad", b * u"rad")
5-element Vector{Gain{Unitful.LogInfo{:Magnitude, 10, -2.5}, :?, Float64}}:
 99.69757461547852 mag
  0.10180447359074371 mag
  0.019595484241066132 mag
  0.010238757633890877 mag
  0.01862100327420125 mag
source