Empirical Relations¶

There are a number of empirical relations contained in the SPLAT code to help convert between common parameters. These are all contained in the splat.empirical module, which should be imported separately:

>>> import splat.empirical as spemp

Examples include:

typeToColor()

Takes a spectral type and optionally a color (string) and returns the typical color of the source, currently using only the Skryzpek et al. (2015) : relations.

Example:

>>> import splat
>>> print splat.typeToColor('L3', 'J-K')
    (1.46, nan)
>>> print splat.typeToMag('M5', 'i-z', ref = 'skrzypek', unc=0.5)
    (0.91, 0.57797809947624645)
>>> print splat.typeToMag('M0', 'i-z', ref = 'skrzypek')
    Spectral type M0.0 is outside the range for reference set Skrzypek et al. (2015)
    (nan, nan)

typeToMag()

Takes a spectral type and a filter, and returns absolute magnitude, using one of several empirical relationships; you can see a list by typing print(splat.SPT_ABSMAG_SETS.keys()).

Example:

>>> import splat
>>> print splat.typeToMag('L3', '2MASS J')
    (12.730064813273996, 0.4)
>>> print splat.typeToMag(21, 'MKO K', ref = 'burgasser')
    (10.705292820099999, 0.26)
>>> print splat.typeToMag(24, '2MASS J', ref = 'faherty')
    Invalid filter given for Abs Mag/SpT relation from Faherty et al. (2012)
    (nan, nan)
>>> print splat.typeToMag('M0', '2MASS H', ref = 'dupuy')
    Spectral Type is out of range for Abs Mag/SpT relation from Dupuy & Liu (2012) Abs Mag/SpT relation
    (nan, nan)

typeToTeff()
Returns an effective temperature (Teff) and its uncertainty for a given spectral type, using one of the following empirical relationships (set by ref keyword):

Golimowski et al. (2004) : Allowed spectral type range is M6 to T8 (ref = 'golimowski')

Looper et al. (2008) : Allowed spectral type range is L0 to T8 (ref = 'looper')

Stephens et al. (2009) : Allowed spectral type range is M6 to T8 and uses alternate coefficients for L3 to T8. (ref = 'stephens')

Marocco et al. (2013) : Allowed spectral type range is M7 to T8 (ref = 'marocco')

Filippazzo et al. (2015). : Allowed spectral type range is M6 to T9 (ref = 'filippazzo')
Example:
>>> import splat >>> print splat.typeToTeff(20) (2233.4796740905499, 100.00007874571999) >>> print splat.typeToTeff(20, unc = 0.3, ref = 'golimowski') (2305.7500497902788, 127.62548366132124)
estimateDistance()
Takes the apparent magnitude in a given filter and either takes or determines the absolute magnitude from empirical relations, then uses the absolute magnitude/distance relation to estimate the distance to the object in parsecs. Returns estimated distance and uncertainty in parsecs. If given only a spectrum object, this routine will measure the apparent magnitude, classify the spectrum, estimate the absolute magnitude, and estimate the distance; any additional inputs such as mag (for apparent magnitude), spt (for spectral type), absmag (for absolute magnitude) and their uncertainties will reduce dependence on the Spectrum object. With all three parameters, this routine operates without a Spectrum object.

Example: >>> import splat >>> sp = splat.getSpectrum(shortname='1555+0954')[0] Retrieving 2 files >>> splat.estimateDistance(sp)

Please specify the filter used to determine the apparent magnitude (nan, nan)
>>> splat.estimateDistance(sp, filter='2MASS J') (212.20546914411625, 50.593458481040173) >>> sp.fluxCalibrate('2MASS J',12.83) >>> splat.estimateDistance(sp, filter='2MASS J') (6.8967647325911665, 1.7439740983732679) >>> splat.estimateDistance(sp, filter='2MASS J', mag=12.83) (6.4528658994336521, 1.6853855848066823) >>> splat.estimateDistance(sp, filter='2MASS J', mag=12.83, mag_e=0.03) (6.1292809243737336, 1.4986946706101478) >>> splat.estimateDistance(sp, filter='2MASS J', mag=12.83, mag_e=0.03, spt='L5') (6.9954039276140554, 1.1679437846129084) >>> splat.estimateDistance(filter='2MASS J', mag=12.83, mag_e=0.03, spt='L5', absmag=13.56, absmag_e = 0.2) (7.1788501442275461, 0.74878521889450711)

Useful Program Constants¶

splat.SPT_BC_SETS, splat.SPT_LBOL_SETS, splat.SPT_ABSMAG_SETS: Dictionaries containing information on the empirical relations contained in the SPLAT code

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