def logN_b_to_Wr(logN, b, wa0, fosc, gamma):
"""I will use the approximation given by Draine book (eq. 9.27),
whic comes from atomic physics considerations + Rodgers & Williams
1974 (I couldn't find the reference though)
Inputs
------
logN: log10 of the column density in cm^-2.
b: Doppler parameter in km/s.
wa0: rest-frame wavelenght of the transition in A.
fosc: oscillator strenght for the transition.
gamma: Gamma parameter for the transition in s^-1.
Returns
-------
Wr: rest-frame equivalent width in A
"""
# give units
wa0 = wa0 * u.AA
N = 10**logN * (1 / u.cm * u.cm)
b = b * u.km / u.s
gamma = gamma * (1 / u.s)
# call linetools function
return ltaa.Wr_from_N_b(N, b, wa0, fosc, gamma)
def get_Wr_from_N_b(self, N, b):
"""It returns the rest-frame equivalent width for a given
N and b. It uses the approximation given by Draine 2011 book
(eq. 9.27), which comes from atomic physics considerations
See also Rodgers & Williams 1974 (NT: could not find the reference
given by Draine)
Parameters
----------
N : Quantity or Quantity array
Column density
b : Quantity or Quantity array of same shape as N
Doppler parameter
Returns
-------
Wr : Quantity
Rest-frame equivalent width
Notes
-----
This is a wrapper to linetools.analysis.absline.Wr_from_N_b().
See also linetools.analysis.absline.Wr_from_N_b_transition().
"""
try:
fosc = self.data['f']
except KeyError:
raise NotImplementedError(
'AbsLine {} has not set its oscillator strength.'.format(
self.__repr__))
try:
gamma = self.data['gamma']
except KeyError:
raise NotImplementedError(
'AbsLine {} has not set its gamma value.'.format(
self.__repr__))
return laa.Wr_from_N_b(N, b, self.wrest, fosc, gamma)