Gradients of chemical abundances in the Milky Way from HII regions:
  distances derived from Gaia EDR3 parallaxes and temperature inhomogeneities
  We present a reassessment of the radial abundance gradients of He, C, N, O,
Ne, S, Cl, and Ar in the Milky Way using the deep optical spectra of 42 HII
regions presented in Arellano-C\'ordova et al. (2020, 2021) and
M\'endez-Delgado et al. (2020) exploring the impact of: (1) new distance
determinations based on Gaia EDR3 parallaxes and (2) the use of Peimbert's
temperature fluctuations paradigm ($t ^ 2> 0$) for deriving ionic abundances.
We find that distances based on Gaia EDR3 data are more consistent with
kinematic ones based on Galactic rotation curves calibrated with radio
parallaxes, which give less dispersion and uncertainties than those calibrated
with spectrophotometric stellar distances. The distances based on the Gaia
parallaxes --DR2 or EDR3-- eliminate the internal flattening observed in
previous determinations of the Galactic gradients at smaller distances than
$\sim 7$ kpc. Abundances and gradients determined assuming $ t ^ 2> 0 $ -- not
only for O but also for the rest of elements -- are not affected by the
abundance discrepancy problem and give elemental abundances much consistent
with the solar ones for most elements. We find that our radial abundance
gradient of He is consistent with the most accurate estimates of the primordial
He abundance. We do not find evidence of azimuthal variations in the chemical
abundances of our sample. Moreover, the small dispersion in the O gradient --
indicator of metallicity in photoionized regions -- indicate that the gas of
the HII regions is well mixed in the sampled areas of the Galaxy.
