AbsLine Class¶
Notebooks¶
Overview¶
This Class is a child of the abstract SpectralLine Class Class. See that documentation for the base methods.
AbsLine is designed to organize and analyze an absorption line. In addition to the attributes defaulted to SpectralLine, this class has:
| Property | Variable | Type | Description |
|---|---|---|---|
| Doppler param. | attrib[‘b’] | Quantity | Doppler parameter |
| b sigma | attrib[‘sig_b’] | Quantity | 1 sigma uncertainty in b |
| Column density | attrib[‘N’] | Quantity | Column density |
| N sigma | attrib[‘sig_N’] | Quantity | 1 sigma uncertainty in N |
| N flag | attrib[‘flag_N’] | int | Column density flag |
Instantiation¶
from_dict¶
Instantiate from a dict. The keys ltype (‘Abs’) and trans are required.
fill_data¶
Attributes¶
See the Table above. logN and sig_logN are commonly used as well.
Plots¶
Methods¶
get_Wr_from_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.:
abslin1 = AbsLine('HI 1215')
N = [10**12.0, 10**12.1, 10**12.2, 10**14.0] / (u.cm*u.cm)
b = [20, 20, 20, 20] * u.km / u.s
Wr = abslin1.get_Wr_from_N_b(N, b)
print(Wr)
<Quantity [ 0.0053758 , 0.00674464, 0.00845469, 0.21149773] Angstrom>
get_Wr_from_N¶
It returns the approximated rest-frame equivalent width for a given N. It uses the approximation given by Draine 2011 book (eq. 9.15), which is valid for tau0<<1 where Wr is independent of Doppler parameter or gamma.:
abslin1 = AbsLine('HI 1215')
N = [10**12.0, 10**12.1, 10**12.2, 10**14.0] / (u.cm*u.cm)
Wr = abslin1.get_Wr_from_N(N)
print(Wr)
<Quantity [ 0.00544783, 0.00685842, 0.00863423, 0.5447833 ] Angstrom>
We can see how the first 4 Wr estimations are good approximation to the more exact solution given by get_Wr_from_N_b(), however, the fourth is off by a factor >2 because the approximation tau0<<1 is not satisfied.
get_N_from_Wr¶
It returns the approximated column density N, for a given rest-frame equivalent width Wr. This is an approximation only valid for tau0 << 1, where Wr is independent on Doppler parameter and gamma (see eqs. 9.14 and 9.15 of Draine 2011). This may be useful to put upper limits on non-detections.:
abslin1 = AbsLine('HI 1215')
Wr = [ 0.00544783, 0.00685842, 0.00863423, 0.5447833 ] * u.AA
N = abslin1.get_N_from_Wr(Wr)
print(np.log10(N.value))
array([ 11.99999976, 12.10000029, 12.19999983, 14. ])