The emission from the relativistic jets in blazars usually outshines their host galaxies , challenging the determination of their distances and the characterization of the stellar population .
The situation becomes more favorable in the case of the extreme blazars ( EHBLs ) , for which the bulk of the emission of the relativistic jets is emitted at higher energies , unveiling the optical emission from the host galaxy .
The distance determination is fundamental for the study of the intrinsic characteristics of the blazars , especially to estimate the intrinsic gamma-ray spectra distorted due to the interaction with the Extragalactic Background Light .
In this work we report on the properties of 2WHSP J073326.7+515354 host galaxy in the optical band , which is one of the few EHBLs detected at TeV energies .
We present the first measurement of the distance of the source , \mathrm { z } = 0.06504 \pm 0.00002 ( velocity dispersion \sigma = 237 \pm 9 \mathrm { kms ^ { -1 } } ) .
We also perform a detailed study of the stellar population of its host galaxy .
We find that the mass-weighted mean stellar age is 11.72 \pm 0.06 \mathrm { Gyr } and the mean metallicity [ M / H ] = 0.159 \pm 0.016 .
In addition , a morphological study of the host galaxy is also carried out .
The surface brightness distribution is modelled by a composition of a dominant classical bulge ( R _ { e } = 3.77 \pm 1 \arcsec or equivalently 4.74 kpc ) plus an unresolved source which corresponds to the active nucleus .
The black hole mass is estimated using both the mass relation with the velocity dispersion and the absolute magnitude from the bulge yielding comparable results : ( 4.8 \pm 0.9 ) \times 10 ^ { 8 } M _ { \odot } and ( 3.7 \pm 1.0 ) \times 10 ^ { 8 } M _ { \odot } , respectively .