The dependence of the IR-radio correlation on the metallicity
  We have compiled a sample of 26 metal-poor galaxies with 12 + log(O/H) < 8.1
with both infrared continuum and 1.4 GHz radio continuum data. By comparing to
galaxies at higher metallicity, we have investigated the dependence on the
metallicity of the IR-radio relationship at 24 um, 70 um, 100 um and 160 um
bands as well as the integrated FIR luminosity. It is found that metal-poor
galaxies have on average lower qIR than metal-rich ones with larger offsets at
longer IR wavelengths, from -0.06 dex in q24um to -0.6 dex in q160um. The qIR
of all galaxies as a whole at 160 um show positive trends with the metallicity
and IR-to-FUV ratio, and negative trends with the IR color, while those at
lower IR wavelengths show weaker correlations. We proposed a mechanism that
invokes combined effects of low obscured-SFR/total-SFR fraction and warm dust
temperature at low metallicity to interpret the above behavior of qIR, with the
former reducing the IR radiation and the latter further reducing the IR
emission at longer IR wavelength. Other mechanisms that are related to the
radio emission including the enhanced magnetic field strength and increased
thermal radio contribution are unable to reconcile the IR-wavelength-dependent
differences of qIR between metal-poor and metal- rich galaxies. In contrast to
qIR, the mean total-SFR/radio ratio of metal-poor galaxies is the same as the
metal-rich one, indicating the 1.4 GHz radio emission is still an effective
tracer of SFRs at low metallicity.
