genesis-metallicity 1.0.0

non-parametric gas-phase metallicity and electron temperature estimation

genesis-metallicity

non-parametric gas-phase metallicity and electron temperature estimation

• strong-line metallicity etstimation when temperature-sensitive emission lines are unavailable
• direct-method metallicity measurement when the temperature-sensetive [O III]4363 line is detected (can also include [O II]7320,30 if available)
• O⁺ electron temperature estimation from that of the O⁺⁺ zone when direct measurements of the former are unavailable
• dust reddening correction of the observed emission line fluxes when multiple Balmer lines are detected

Installation

genesis_metallicity is pip installable:

pip install genesis_metallicity

Examples

strong-line metallcitiy estimation

The following is an example of the "strong-line" metallicity estimation. The emission line measurements are imported in a python dictionary, where a python list with two items is entered for each emission line: the first item corresponds to the measured line flux and the second item corresponds to the flux uncertainty. Note that providing the object ID and redshift, as done below, are optional and only meant to assist with bookkeeping.

from genesis_metallicity.genesis_metallicity import genesis_metallicity

object = 'JADES_3675'

input_dict = {}
input_dict['redshift'] = 9.43
input_dict['OII']      = [7.269250230638606e-20, 5.7108025103430405e-21]
input_dict['Hdelta']   = [1.592676517913214e-19, 4.405126486743839e-21]
input_dict['Hgamma']   = [2.6671788939798604e-19, 5.274969458136735e-21]
input_dict['Hbeta']    = [6.447421960287729e-19, 6.48899753642406e-21]
input_dict['O4959']    = [1.0763985148795857e-18, 8.773228322203986e-21]
input_dict['O5007']    = [3.0628160287038502e-18, 1.0895841873808477e-20]
input_dict['Hbeta_EW'] = [158.728418552416, 13.991218097105634]

galaxy = genesis_metallicity(input_dict, object=object)
print(' -> strong-line metallicity:', galaxy.metallicity)
print(' -> strong-line metallicity (nominal value):', galaxy.metallicity.n)
print(' -> strong-line metallicity (standard deviation):', galaxy.metallicity.s)

direct-method metallicity measurement

If the temperature-sensitive [O III]4363 emission line is detected, the gas-phase metallicity can be measured directly. This is demonstrated in the example below, where the input emission lines remain the same as in the previous example, but with the addition of the [O III]4363 flux.

from genesis_metallicity.genesis_metallicity import genesis_metallicity

object = 'JADES_3675'

input_dict = {}
input_dict['redshift'] = 9.43
input_dict['OII']      = [7.269250230638606e-20, 5.7108025103430405e-21]
input_dict['Hdelta']   = [1.592676517913214e-19, 4.405126486743839e-21]
input_dict['Hgamma']   = [2.6671788939798604e-19, 5.274969458136735e-21]
input_dict['O4363']    = [7.1092219385595e-20, 5.0986852540807764e-21]
input_dict['Hbeta']    = [6.447421960287729e-19, 6.48899753642406e-21]
input_dict['O4959']    = [1.0763985148795857e-18, 8.773228322203986e-21]
input_dict['O5007']    = [3.0628160287038502e-18, 1.0895841873808477e-20]
input_dict['Hbeta_EW'] = [158.728418552416, 13.991218097105634]

galaxy = genesis_metallicity(input_dict, object=object)
print(' -> direct-method metallicity:', galaxy.metallicity)
print(' -> direct-method metallicity (nominal value):', galaxy.metallicity.n)
print(' -> direct-method metallicity (standard deviation):', galaxy.metallicity.s)

electron temperature estimation

It’s often desirable to estimate the O⁺ electron temperature (t2) from the directly measured O⁺⁺ electron temperature (t3). This is particularly the case at high redshifts, where the t3 can be measured directly from the [O III]4363 line, while the t2 cannot be measured directly because the [O II]7320,30 doublet is often too faint or redshifted out of coverage. In such cases, the t2 estimations are carried out automatically by genesis_metallicity; the measured electron temperatures can be accessed as shown below.

from genesis_metallicity.genesis_metallicity import genesis_metallicity

object = 'JADES_3675'

input_dict = {}
input_dict['redshift'] = 9.43
input_dict['OII']      = [7.269250230638606e-20, 5.7108025103430405e-21]
input_dict['Hdelta']   = [1.592676517913214e-19, 4.405126486743839e-21]
input_dict['Hgamma']   = [2.6671788939798604e-19, 5.274969458136735e-21]
input_dict['O4363']    = [7.1092219385595e-20, 5.0986852540807764e-21]
input_dict['Hbeta']    = [6.447421960287729e-19, 6.48899753642406e-21]
input_dict['O4959']    = [1.0763985148795857e-18, 8.773228322203986e-21]
input_dict['O5007']    = [3.0628160287038502e-18, 1.0895841873808477e-20]
input_dict['Hbeta_EW'] = [158.728418552416, 13.991218097105634]

galaxy = genesis_metallicity(input_dict, object=object)
print('--------------------------------------------------------------------------')
print(' -> O++ electron temperature' )
print(' -> direct-method te(OIII) [K]:', galaxy.t3)
print(' -> direct-method te(OIII) [K] (nominal value):', galaxy.t3.n)
print(' -> direct-method te(OIII) [K] (standard deviation):', galaxy.t3.s)
print('--------------------------------------------------------------------------')
print(' -> O+ electron temperature' )
print(' -> direct-method te(OII) [K]:', galaxy.t2)
print(' -> direct-method te(OII) [K] (nominal value):', galaxy.t2.n)
print(' -> direct-method te(OII) [K] (standard deviation):', galaxy.t2.s)
print('--------------------------------------------------------------------------')

dust reddening correction

By default, genesis_metallicity assumes that the input emission line fluxes are the observed values without any reddening correction (this behavior can be modified by the user; see the end of the next paragraph). As such, the input line fluxes are automatically corrected for dust reddening. The meaured V-band attenuation as well as the reddening-corrected emission line fluxes can be accessed as shown below. If the line of interest is included in the data/lines.py script, its flux can be included in the input dictionary for reddening correction. Otherwise, the line ID and rest-wavelength have to be added to data/lines.py by the user.

Note that the galaxy.reddening_corrected_lines outpout is a dictionary, where the reddening-corrected line fluxes are stored. For instance, the reddening-corrected flux and flux uncertainty of Hbeta can be accessed as galaxy.reddening_corrected_lines['Hbeta'].n and galaxy.reddening_corrected_lines['Hbeta'].s, respectively. If the input emission lines are already reddening-corrected, the reddening correction can be switched off by setting correct_extinction=False in the main genesis_metallicity function call; i.e., by calling the main routine as genesis_metallicity(input_dict, object=object, correct_extinction=False).

from genesis_metallicity.genesis_metallicity import genesis_metallicity

object = 'JADES_3675'

input_dict = {}
input_dict['redshift'] = 9.43
input_dict['OII']      = [7.269250230638606e-20, 5.7108025103430405e-21]
input_dict['Hdelta']   = [1.592676517913214e-19, 4.405126486743839e-21]
input_dict['Hgamma']   = [2.6671788939798604e-19, 5.274969458136735e-21]
input_dict['O4363']    = [7.1092219385595e-20, 5.0986852540807764e-21]
input_dict['Hbeta']    = [6.447421960287729e-19, 6.48899753642406e-21]
input_dict['O4959']    = [1.0763985148795857e-18, 8.773228322203986e-21]
input_dict['O5007']    = [3.0628160287038502e-18, 1.0895841873808477e-20]
input_dict['Hbeta_EW'] = [158.728418552416, 13.991218097105634]

galaxy = genesis_metallicity(input_dict, object=object)
print(' -> Av:', galaxy.Av)
print(' -> reddening-corrected line fluxes:')
print(galaxy.reddening_corrected_lines)