pyspectools.astro package

Submodules

pyspectools.astro.analysis module

pyspectools.astro.analysis.calculate_L(W, frequency, S)[source]

Calculate L, which is subsequently used to perform rotational temperature analysis.

Parameters

  • - float (S) – Integrated flux of a line

  • - float – Frequency of a transition in MHz

  • - float – Intrinsic linestrength of the transition

Returns

Return type

L - float

pyspectools.astro.analysis.lineprofile_analysis(fit, I, Q, T, E_lower)[source]

Low-level function to provide some analysis based on a fitted line profile and some theoretical parameters.

Basically a collection of various parameters that are of interest to astronomy.

fit - lmfit ModelResult object I - log10(theoretical intensity) Q - rotational partition function T - temperature in K E - lower state energy in K

data_dict - dict results of lineprofile analysis

pyspectools.astro.analysis.rotational_temperature_analysis(L, E_upper)[source]

Function that will perform a rotational temperature analysis. This will perform a least-squares fit of log(L), which is related to the theoretical line strength and integrated flux, and the upper state energy for the same transition.

Parameters

  • - 1D array (E_upper) – Value L related to the line and theoretical line strength

  • - 1D array – The upper state energy in wavenumbers.

Returns

Result of the least-squares fit

Return type

ModelResult - object

pyspectools.astro.analysis.simulate_catalog(catalogpath, N, Q, T, doppler=10.0)[source]

Function for simulating what the expected flux would be for a given molecule and its catalog file from SPCAT. Returns a spectrum of Gaussian line shapes, predicted by either a supplied Doppler width or session-wide value (self.doppler), and the parameters required to calculate the flux in Jy.

Parameters

  • catalogpath – path to the SPCAT catalog file

  • N – column density in cm^-2

  • Q – rotational partition function

  • T – temperature in Kelvin

  • doppler – Doppler width in km/s

Returns

simulated_df; pandas dataframe with frequency/intensity

pyspectools.astro.conversions module

pyspectools.astro.conversions.N2flux(N, S, v, Q, E, T)[source]

Calculate the expected integrated flux based on column density. This can be used to simulate a spectrum purely from theoretical terms.

N - column density in cm^-2 S - intrinsic line strength; Su^2 v - transition frequency in MHz Q - rotational partition function E - state energy T - temperature

flux - the integrated flux in Jy

pyspectools.astro.conversions.flux2N(W, Q, E, T, S, v)[source]

Calculate the column density (1/cm^2) based on theoretical intensities for rotational transitions, and the observed flux per beam (Jy/beam)

W - integrated area of line profile; Jy Q - rotational partition function at given temperature E - upper state energy; Kelvin T - temperature; Kelvin S - formally Su^2; intrinsic linestrength v - transition frequency in MHz

N - column density in 1/cm^2

pyspectools.astro.radiative module

radiative.py

Routines for calculating quantities useful for radiative transfer, such as Einstein coefficients

pyspectools.astro.radiative.I2S(I, Q, frequency, E_lower, T=300.0)[source]

Function for converting intensity (in nm^2 MHz) to the more standard intrinsic linestrength, S_ij mu^2.

Parameters

  • - float (T) – The log of the transition intensity, typically given in catalog files

  • - float – Partition function at specified temperature T

  • - float – Frequency of the transition in MHz

  • - float – Energy of the lower state in wavenumbers

  • - float – Temperature in Kelvin

Returns

Value of the intrinsic linestrength

Return type

siju - float

pyspectools.astro.radiative.approx_Q_linear(B, T)[source]

Approximate rotational partition function for a linear molecule.

Parameters

  • - float (T) – Rotational constant in MHz.

  • - float – Temperature in Kelvin.

Returns

Rotational partition function at temperature T.

Return type

Q - float

pyspectools.astro.radiative.approx_Q_top(A, B, T, sigma=1, C=None)[source]

Approximate expression for the (a)symmetric top partition function. The expression is adapted from Gordy and Cook, p.g. 57 equation 3.68. By default, the prolate top is used if the C constant is not specified, where B = C. Oblate case can also be specified if A = C.

Parameters

  • - float (T) – Rotational constant for the A principal axis, in MHz.

  • - float – Rotational constant for the B principal axis, in MHz.

  • - float – Temperature in Kelvin

  • - int (sigma) – Rotational level degeneracy; i.e. spin statistics

  • - float, optional (C) – Rotational constant for the C principal axis, in MHz. Defaults to None, which will reduce to the prolate top case.

Returns

Partition function for the molecule at temperature T

Return type

Q - float

pyspectools.astro.radiative.boltzmann_factor(E, T)[source]

Calculate the Boltzmann weighting for a given state and temperature.

Parameters

  • - float (T) – State energy in wavenumbers

  • - float – Temperature in Kelvin

Returns

Unitless Boltzmann factor for the state

Return type

boltzmann_factor - float

pyspectools.astro.radiative.calc_E_upper(frequency, E_lower)[source]

Calculate the upper state energy, for a given lower state energy and the frequency of the transition.

Parameters

  • - float (E_lower) – Frequency of the transition in MHz

  • - float – Lower state energy in wavenumbers

Returns

Upper state energy in wavenumbers

Return type

E_upper - float

pyspectools.astro.radiative.calc_einstein(str_filepath)[source]

High-level function for calculating Einstein A coefficients for a given .str file output from SPCAT.

pyspectools.astro.radiative.einsteinA(S, frequency)[source]
pyspectools.astro.radiative.parse_str(filepath)[source]

Module contents