implemented SuperGalCoords

JuliaAstro · Feb 24, 2023 · 917a43b · 917a43b
1 parent f69923e
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diff --git a/src/SkyCoords.jl b/src/SkyCoords.jl
@@ -8,6 +8,7 @@ using StaticArrays
 export AbstractSkyCoords, 
        ICRSCoords,
        GalCoords,
+       SuperGalCoords,
        FK5Coords,
        EclipticCoords,
        CartesianCoords,
@@ -66,6 +67,22 @@ const GAL_TO_FK5J2000 = FK5J2000_TO_GAL'
 const GAL_TO_ICRS = FK5J2000_TO_ICRS * GAL_TO_FK5J2000
 const ICRS_TO_GAL = GAL_TO_ICRS'
 
+
+# Gal --> SuperGal
+# we use the same parameters as in astropy
+sgp_l = deg2rad(47.37)
+sgp_b = deg2rad(6.32)
+# rotation matrix compared to astropy
+const GAL_TO_SUPERGAL = RotZYZ(-π / 2, sgp_b - π / 2, -sgp_l)'
+const SUPERGAL_TO_GAL = GAL_TO_SUPERGAL'
+# SuperGal --> ICRS: chain through GAL
+const SuperGal_TO_ICRS = GAL_TO_ICRS * SUPERGAL_TO_GAL
+const ICRS_TO_SuperGAL = SuperGal_TO_ICRS'
+# SuperGal --> FK5J2000: chain through GAL
+const SuperGal_TO_FK5J2000 = GAL_TO_FK5J2000 * SUPERGAL_TO_GAL
+const FK5J2000_TO_SuperGAL = SuperGal_TO_FK5J2000'
+
+
 # FK5J2000 --> FK5{epoch}
 # Computes the precession matrix from J2000 to the given Julian equinox.
 # Expression from from Capitaine et al. 2003 as expressed in the USNO
@@ -99,6 +116,8 @@ end
 
 lon(c::GalCoords) = c.l
 lat(c::GalCoords) = c.b
+lon(c::SuperGalCoords) = c.l
+lat(c::SuperGalCoords) = c.b
 lat(c::EclipticCoords) = c.lat
 lon(c::EclipticCoords) = c.lon
 lon(c::AbstractSkyCoords) = c.ra
@@ -115,6 +134,12 @@ rotmat(::Type{<:ICRSCoords}, ::Type{<:GalCoords}) = GAL_TO_ICRS
 rotmat(::Type{<:ICRSCoords}, ::Type{<:ICRSCoords}) = I
 rotmat(::Type{<:GalCoords}, ::Type{<:GalCoords}) = I
 rotmat(::Type{<:FK5Coords{e}}, ::Type{<:FK5Coords{e}}) where {e} = I
+rotmat(::Type{<:GalCoords}, ::Type{<:SuperGalCoords}) = GAL_TO_SUPERGAL
+rotmat(::Type{<:SuperGalCoords}, ::Type{<:GalCoords}) = SUPERGAL_TO_GAL
+rotmat(::Type{<:SuperGalCoords}, ::Type{<:SuperGalCoords}) = I
+rotmat(::Type{<:SuperGalCoords}, ::Type{<:ICRSCoords}) = SuperGal_TO_ICRS
+rotmat(::Type{<:ICRSCoords}, ::Type{<:SuperGalCoords}) = ICRS_TO_SuperGAL
+
 
 @generated rotmat(::Type{<:EclipticCoords{e}}, ::Type{<:FK5Coords{e}}) where {e} = RotX(-ecliptic_obliquity(e))
 @generated rotmat(::Type{<:FK5Coords{e}}, ::Type{<:EclipticCoords{e}}) where {e} = RotX(ecliptic_obliquity(e))
@@ -127,10 +152,14 @@ rotmat(::Type{<:FK5Coords{e}}, ::Type{<:FK5Coords{e}}) where {e} = I
     precess_from_j2000(e1) * ICRS_TO_FK5J2000
 @generated rotmat(::Type{<:FK5Coords{e1}}, ::Type{<:GalCoords}) where {e1} =
     precess_from_j2000(e1) * GAL_TO_FK5J2000
+@generated rotmat(::Type{<:FK5Coords{e1}}, ::Type{<:SuperGalCoords}) where {e1} =
+    precess_from_j2000(e1) * SuperGal_TO_FK5J2000
 @generated rotmat(::Type{<:ICRSCoords}, ::Type{<:FK5Coords{e2}}) where {e2} =
     FK5J2000_TO_ICRS * precess_from_j2000(e2)'
 @generated rotmat(::Type{<:GalCoords}, ::Type{<:FK5Coords{e2}}) where {e2} =
     FK5J2000_TO_GAL * precess_from_j2000(e2)'
+@generated rotmat(::Type{<:SuperGalCoords}, ::Type{<:FK5Coords{e2}}) where {e2} =
+    FK5J2000_TO_SuperGAL * precess_from_j2000(e2)'
 @generated rotmat(::Type{<:FK5Coords{e1}}, ::Type{<:FK5Coords{e2}}) where {e1,e2} =
     precess_from_j2000(e1) * precess_from_j2000(e2)'
 

diff --git a/src/types.jl b/src/types.jl
@@ -48,6 +48,29 @@ GalCoords(l::Real, b::Real) = GalCoords(promote(float(l), float(b))...)
 GalCoords(c::T) where {T<:AbstractSkyCoords} = convert(GalCoords, c)
 GalCoords{F}(c::T) where {F,T<:AbstractSkyCoords} = convert(GalCoords{F}, c)
 
+"""
+    SuperGalCoords(l, b)
+
+[Supergalactic Coordinate System](https://en.wikipedia.org/wiki/Supergalactic_coordinate_system)
+
+The supergalactic plane is part of a reference frame for the supercluster of galaxies that contains the Milky Way galaxy.
+The supergalactic plane as so-far observed is more or less perpendicular to the plane of the Milky Way, the angle is 84.5 degrees. Viewed from the Earth, the plane traces a great circle across the sky through the constellations 
+
+# Coordinates
+- `l` - SuperGalCoords longitude in radians (-π, π)
+- `b` - SuperGalCoords latitude in radians (-π/2, π/2)
+"""
+struct SuperGalCoords{T<:AbstractFloat} <: AbstractSkyCoords
+    l::T
+    b::T
+    SuperGalCoords{T}(l, b) where {T<:AbstractFloat} = new(mod2pi(l), b)
+end
+SuperGalCoords(l::T, b::T) where {T<:AbstractFloat} = SuperGalCoords{T}(l, b)
+SuperGalCoords(l::Real, b::Real) = SuperGalCoords(promote(float(l), float(b))...)
+SuperGalCoords(c::T) where {T<:AbstractSkyCoords} = convert(SuperGalCoords, c)
+SuperGalCoords{F}(c::T) where {F,T<:AbstractSkyCoords} = convert(SuperGalCoords{F}, c)
+
+
 """
     FK5Coords{equinox}(ra, dec)
 
@@ -107,5 +130,6 @@ end
 Base.:(==)(a::T, b::T) where {T<:AbstractSkyCoords} = lon(a) == lon(b) && lat(a) == lat(b)
 Base.isapprox(a::ICRSCoords, b::ICRSCoords; kwargs...) = isapprox(SVector(lon(a), lat(a)), SVector(lon(b), lat(b)); kwargs...)
 Base.isapprox(a::GalCoords, b::GalCoords; kwargs...) = isapprox(SVector(lon(a), lat(a)), SVector(lon(b), lat(b)); kwargs...)
+Base.isapprox(a::SuperGalCoords, b::SuperGalCoords; kwargs...) = isapprox(SVector(lon(a), lat(a)), SVector(lon(b), lat(b)); kwargs...)
 Base.isapprox(a::FK5Coords{e}, b::FK5Coords{e}; kwargs...) where {e} = isapprox(SVector(lon(a), lat(a)), SVector(lon(b), lat(b)); kwargs...)
 Base.isapprox(a::EclipticCoords{e}, b::EclipticCoords{e}; kwargs...) where {e} = isapprox(SVector(lon(a), lat(a)), SVector(lon(b), lat(b)); kwargs...)