Tool functions

Functions that perform most of the math.

spookyspec.tools.calc_snr(x, y, ycont, w1, w2)

Calculate SNR

Calculate the signal-to-noise ratio of a spectrum.

Parameters

• x (np.array) – wavelength values of the spectrum

• y (np.array) – flux values of the spectrum

• ycont (np.array) – flux values of the continuum

• w1 (float) – starting wavelength with same units as x

• w2 (float) – ending wavelength with same units as x

Returns

the SNR of the spectrum

Return type

(float)

spookyspec.tools.convert_line(x, y, ycont, lam)

change coordinate system so line center is at zero, continuum is zero, and absorption is positive this is to make fitting easier

spookyspec.tools.ddx(x, y)

Derivative

Numerical derivitive with np.gradient

Parameters

• x (array-like) – x values

• y (array-like) – y values

Returns

x values (np.array): derivative of x and y

Return type

(np.array)

spookyspec.tools.equivalent_width(x, y, ycont, w1, w2, unit, plot=False)

Equivalent width

Measure the equivalent width of a region of the spectrum

Parameters

• x (np.array) – wavelength values of the spectrum

• y (np.array) – flux values of the spectrum

• ycont (np.array) – flux values of the continuum

• w1 (float) – starting wavelength

• w2 (float) – ending wavelength

• unit (astropy.units.Unit) – units of x, w1, and w2

Keyword Arguments

plot (bool) – whether or not to plot the spectrum

Returns

equivalent width of region

Return type

(astropy.Quantity)

spookyspec.tools.equivalent_width_error(x, y, ycont, W1, W2, unit)

Equivalent width error

Estimate the uncertainty in the equivalent width of a region

Parameters

• x (np.array) – wavelength values of the spectrum

• y (np.array) – flux values of the spectrum

• ycont (np.array) – flux values of the continuum

• W1 (float) – starting wavelength

• W2 (float) – ending wavelength

• unit (astropy.units.Unit) – units of x, W1, and W2

Returns

equivalent width uncertainty of region

Return type

(astropy.Quantity)

spookyspec.tools.get_continuum(x, y, w1, w2, **kwargs)

Get continuum

Fit the continuum of a spectrum

Parameters

x –

fit a polynomial f to the continuum and return the array f(x) between the wavelengths w1,w2

spookyspec.tools.get_continuum_points(x, y, **kwargs)

Get continuum points

Get a boolean array indicating which points are part of the continuum

Parameters

• x (np.array) – wavelength values of the spectrum

• y (np.array) – flux values of the spectrum

Keyword Arguments

• pct (float in range [0,1]) – residual cutoff percentile. Default 0.85

• box (int) – radius of surrounding points to check. Default 5

• degree (int) – fitting degree. Default 1

• cutoff (float) – second derivitive cutoff for fitting a model continuum. Default 1e-12

• stype (str) – data or model. Type of spectrum to fit continuum. Default data

Returns

points that part of the spectral continuum

Return type

(np.array of bool)

spookyspec.tools.poly_x(x, coeffs)

Polynomial

Transform an array of x values given coefficients of a polynomial function

Parameters

• x (np.array) – values to be transformed

• coeffs (array-like) – coefficents of the polynomical function starting with the highest order

Returns

y values of the polynomial function

Return type

(np.array)

spookyspec.tools.redshift(l, v)

Redshift

Get the doppler shifted wavelength of a line given the linecenter wavelength and radial velocity

Parameters

• l (astropy.Quantity) – wavelength to be shifted

• v (astropy.Quantity) – radial velocity

Returns

red/blue shifted wavelength

Return type

(astropy.Quantity)

spookyspec.tools.reject(x, y, **kwargs)

Reject Rejection procedure for finding the continuum of a spectrum works best if y has some noise

Parameters

• x (np.array) – wavelength values of the spectrum

• y (np.array) – flux values of the spectrum

Keyword Arguments

• pct (float in range [0,1]) – residual cutoff percentile. Default 0.85

• box (int) – radius of surrounding points to check. Default 5

• degree (int) – fitting degree. Default 1

Returns

points that part of the spectral continuum

Return type

(np.array of bool)

spookyspec.tools.to_air(vac)

To air

Convert from vacuum to air wavelengths

Parameters

vac (astropy.Quantity) – wavelength(s) to be shifted

Returns

wavelength(s) in air

Return type

(astropy.Quantity)

spookyspec.tools.trap_rule(x, f)

Trapazoid rule

Integrate using Trapizoid rule.

Parameters

• x (array-like) – x values to integrate over

• f (array-like) – y values to integrate over

Returns

(float) integral of f over the domain of x