Return true E(B-V) for filter=E(B-V) (#36)

.github/workflows/build.yml

@@ -21,7 +21,7 @@ jobs:
       uses: actions/cache@v3
       with:
         path: ${{github.workspace}}/data/
-        key: sfd-green19-${{ runner.os }}-
+        key: sfd-green19-marshall06-combined15-${{ runner.os }}-
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v4
       with:

HISTORY.txt

@@ -4,6 +4,8 @@ v1.4 (XXXX-XX-XX)
 - Allowed array inputs to dust maps derived from HierarchicalHealpixMap
   (GreenX and CombinedX maps) and use vectorization to speed these up signficantly.
 
+- Allow filter=E(B-V) to get the true color excess E(B-V).
+
 v1.3 (2023-03-07)
 ==================
 

README.rst

@@ -146,20 +146,11 @@ Note that this requires ``healpy`` to be installed, so this does not work on Win
 Supported bandpasses
 ---------------------
 
-Currently only a few filters are supported; if no filter is supplied,
-*E(B-V)* is returned on the SFD scale if the object is initialized
-with ``sf10=True`` (which tells the code to use re-scalings from
-`Schlafly & Finkbeiner 2011
-<http://adsabs.harvard.edu/abs/2011ApJ...737..103S>`__). ``sf10=True``
-is the default initialization for every map, so be careful in
-interpreting the raw *E(B-V)* that come out of the code. *Only use*
-``sf10=False`` *when you have an extinction map in true E(B-V)*, **not**
-*SFD E(B-V)*. No map currently included in this package is in this
-situation, so using ``sf10=False`` is never recommended.
-
-To check what bandpasses are supported on the ``sf10=True`` scale do
+Currently only a few filters are supported. 
+To obtain E(B-V), specify ``filter=E(B-V)``.
+To check what bandpasses are supported on the ``sf10=True`` scale
 (these are all the bandpasses from Table 6 in `Schlafly & Finkbeiner
-2011 <http://adsabs.harvard.edu/abs/2011ApJ...737..103S>`__)
+2011 <http://adsabs.harvard.edu/abs/2011ApJ...737..103S>`__), do
 
 ..  code-block:: python
 
@@ -195,6 +186,18 @@ which gives
       'SDSS r', 'SDSS u', 'SDSS z', 'SDSS g', 'SDSS i', '2MASS Ks',
       '2MASS J'], dtype='|S14')
 
+
+If no filter is supplied, *E(B-V)* is returned on the SFD scale if the object is initialized
+with ``sf10=True`` (which tells the code to use re-scalings from
+`Schlafly & Finkbeiner 2011
+<http://adsabs.harvard.edu/abs/2011ApJ...737..103S>`__). ``sf10=True``
+is the default initialization for every map, so be careful in
+interpreting the raw *E(B-V)* that come out of the code when 
+not setting ``filter`` or when setting ``filter=None``. *Only use*
+``sf10=False`` *when you have an extinction map in true E(B-V)*, **not**
+*SFD E(B-V)*. No map currently included in this package is in this
+situation, so using ``sf10=False`` is never recommended.
+
 Acknowledging ``mwdust`` and its data
 ---------------------------------------
 

mwdust/util/extCurves.py

@@ -52,10 +52,13 @@ def aebv(filter,sf10=True):
     HISTORY:
        2013-11-24 - Written - Bovy (IAS)
     """
+    if filter.lower() == 'e(b-v)':
+        return 0.884
     if sf10:
         if not filter in avebvsf:
             raise ValueError("Requested filter is not supported")
-        return avebvsf[filter]
+        else:
+            return avebvsf[filter]
     else:
         if not filter in avebv:
             raise ValueError("Requested filter is not supported")

tests/test_ebv.py

@@ -0,0 +1,65 @@
+# Test that asking for E(B-V) returns the correct value for all dust maps
+import numpy
+import mwdust
+
+def test_SFD():
+    sfd_ebv= mwdust.SFD(filter='E(B-V)')
+    sfd_b= mwdust.SFD(filter='Landolt B')
+    sfd_v= mwdust.SFD(filter='Landolt V')
+    l,b,d= 10., 1., 2.
+    assert numpy.fabs(sfd_ebv(l,b,d)-(sfd_b(l,b,d)-sfd_v(l,b,d))) \
+         < 10.**-12., \
+        'SFD E(B-V) does not agree with A(B)-A(V)'
+    return None
+
+def test_Drimmel03():
+    drim_ebv= mwdust.Drimmel03(filter='E(B-V)')
+    drim_b= mwdust.Drimmel03(filter='Landolt B')
+    drim_v= mwdust.Drimmel03(filter='Landolt V')
+    l,b,d= 10., 1., 2.
+    assert numpy.fabs(drim_ebv(l,b,d)-(drim_b(l,b,d)-drim_v(l,b,d))) \
+         < 10.**-12., \
+        'Drimmel03 E(B-V) does not agree with A(B)-A(V)'
+    return None
+
+def test_Marshall06():
+    mar_ebv= mwdust.Marshall06(filter='E(B-V)')
+    mar_b= mwdust.Marshall06(filter='Landolt B')
+    mar_v= mwdust.Marshall06(filter='Landolt V')
+    l,b,d= 10., 1., 2.
+    assert numpy.fabs(mar_ebv(l,b,d)-(mar_b(l,b,d)-mar_v(l,b,d))) \
+         < 10.**-12., \
+        'Marshall06 E(B-V) does not agree with A(B)-A(V)'
+    return None
+
+def test_Green19():
+    # Need to preserve memory
+    l,b,d= 10., 1., 2.
+    green_ebv= mwdust.Green19(filter='E(B-V)')
+    ebv= green_ebv(l,b,d)
+    del green_ebv
+    green_b= mwdust.Green19(filter='Landolt B')
+    ab= green_b(l,b,d)
+    del green_b
+    green_v= mwdust.Green19(filter='Landolt V')
+    av= green_v(l,b,d)
+    assert numpy.fabs(ebv-(ab-av)) \
+         < 10.**-12., \
+        'Green19 E(B-V) does not agree with A(B)-A(V)'
+    return None
+
+def test_Combined15():
+    # Need to preserve memory
+    l,b,d= 10., 1., 2.
+    combined_ebv= mwdust.Combined15(filter='E(B-V)')
+    ebv= combined_ebv(l,b,d)
+    del combined_ebv
+    combined_b= mwdust.Combined15(filter='Landolt B')
+    ab= combined_b(l,b,d)
+    del combined_b
+    combined_v= mwdust.Combined15(filter='Landolt V')
+    av= combined_v(l,b,d)
+    assert numpy.fabs(ebv-(ab-av)) \
+         < 10.**-12., \
+        'Combined15 E(B-V) does not agree with A(B)-A(V)'
+    return None