Extremely metal-poor ( XMP ) galaxies are defined to have gas-phase metallicity smaller than a tenth of the solar value ( 12 + \log [ { O / H } ] < 7.69 ) .
They are uncommon , chemically and possibly dynamically primitive , with physical conditions characteristic of earlier phases of the Universe .
We search for new XMPs in the Sloan Digital Sky Survey ( SDSS ) in a work that complements Paper I .
This time high electron temperature objects are selected ; since metals are a main coolant of the gas , metal-poor objects contain high-temperature gas .
Using the algorithm k-means , we classify 788677 spectra to select 1281 galaxies having particularly intense [ OIII ] \lambda 4363 with respect to [ OIII ] \lambda 5007 , which is a proxy for high electron temperature .
The metallicity of these candidates was computed using a hybrid technique consistent with the direct method , rendering 196 XMPs .
A less restrictive noise constraint provides a larger set with 332 candidates .
Both lists are provided in electronic format .
The selected XMP sample have mean stellar mass around 10 ^ { 8 } { M } _ { \odot } , with dust-mass \sim 10 ^ { 3 } { M } _ { \odot } for typical star-forming regions .
In agreement with previous findings , XMPs show a tendency to be tadpole-like or cometary .
Their underlying stellar continuum corresponds to a fairly young stellar population ( < 1 { Gyr } ) , although young and aged stellar populations co-exists at the low-metallicity starbursts .
About 10 % of the XMPs shows large N/O .
Based on their location in constrained cosmological numerical simulations , XMPs have a strong tendency to appear in voids and to avoid galaxy clusters .
The puzzling 2 % -solar low-metallicity threshold exhibited by XMPs remains .