The Host in Blue Compact Galaxies: Structural Properties and Scaling
  Relations
  We have characterized the underlying stellar host in a sample of 28 blue
compact galaxies (BCGs), by fitting their 2D light distributions. Their
structural parameters were related with galaxy properties such as colours and
gas content. These properties were also compared with those of other galaxy
types. All the BCG hosts but one show low Sersic indexes (0.5 < n < 2), with
mean effective radius <$r_{e,B}$>=1.11$\pm$0.74 kpc, and mean surface
brightness <$\mu_{e,B}$> = 22.59$\pm$0.68 mag arcsec$^{-2}$. Host effective
radii scale linearly with their luminosity, while n and $\mu_{\rm e}$ do not.
In addition, host colours and structural parameters are not linearly
correlated. Overall,the flux enhancement caused by the starburst is about 0.8
mag while their B-R colours decrease by about 0.2 mag. Galaxies with more
luminous and extended hosts show larger and luminous starburst components. BCG
hosts show B-R=0.95$\pm$0.26 in median. Overall, BCG hosts are more compact (by
a factor ~2) and have higher central surface brightnesses (by about ~2 mag)
than dIs and most dEs. BCG hosts and dIs are indistinguishable in the B-band
Tully-Fisher relation (TFR). We found that about 50-60 % of the galaxies are
more underluminous than those late-type discs with the same circular velocity.
This feature is more important when luminosities are converted into stellar
masses, while it tends to diminish when the HI gas mass is added. Deviations
among host masses for a given circular velocity from the stellar TFR correlate
with their HI mass-to-luminosity ratio, whereas deviations from the gas+stellar
TFR, do not. Overall, our findings suggest that the baryonic mass in BCGs tends
to normal values but BCGs tend to be inefficient producing stars, especially
toward the low-mass, gas-rich and bluest hosts, in a similar way to dIs.
