tmr_kcorr.py

import numpy             as np

from   pkg_resources     import resource_filename


class tmr_kcorr():
    '''
    See: https://arxiv.org/pdf/1409.4681.pdf 
         https://arxiv.org/pdf/1701.06581.pdf
    '''

    def __init__(self):
        self.z0      = 0.0

        self.raw_dir = resource_filename('lumfn', 'data/')
        self.raw     = np.loadtxt(self.raw_dir + '/tmr_kcorr.txt')
        self.base    = 4 - np.arange(0, 5, 1)
        
        self.ncol    = len(self.raw[:,0])

    def ref_eval(self, ref_gmr, zz):
        '''
        TMR r-band kcorrection at z reference 0.0
        '''

        zz       = np.atleast_1d(zz)
        ref_gmr  = np.atleast_1d(ref_gmr)

        idx      = np.digitize(ref_gmr, bins=self.raw[:,0], right=True)        
        idx[idx >= self.ncol] = (self.ncol - 1)

        aa       = self.raw[idx, 1:]
        zz       = np.exp(np.log(zz)[:,None] * self.base[None,:])
        res      = aa * zz        
        res      = np.sum(res, axis=1)
        
        return  res
        
def plot():
    import pylab as pl
    import matplotlib.pyplot as plt


    x         = tmr_kcorr()

    ref_gmrs  = [0.158, 0.298, 0.419, 0.553, 0.708, 0.796, 0.960]
    zs        = np.arange(0.01, 0.801, 0.01)
    
    fig, axes = plt.subplots(1,2, figsize=(15,5))

    colors    = plt.rcParams['axes.prop_cycle'].by_key()['color']

    for ref_gmr, color in zip(ref_gmrs, colors):
        rks = x.ref_eval(ref_gmr, zs)

        axes[0].plot(zs, rks, '-', c=color, alpha=0.75, label='ref. $(g-r)$: {:.3f}'.format(ref_gmr))

    axes[0].set_ylabel(r"$^{0.0}K_r(z)$")
    axes[1].set_ylabel(r"$^{0.0}K_g(z)$")

    for ax in axes:
        ax.set_xlabel(r"$z$")
        ax.set_xlim(-0.01, 0.5)
        ax.set_ylim(-0.21, 1.2)

        ax.legend(loc=2, frameon=False, fontsize=8)

    pl.savefig('test.pdf')