A deep Spitzer Infrared Spectrograph ( IRS ) map of the PKS 1138-26 galaxy protocluster reveals ultraluminous PAH emission from obscured star formation in three protocluster galaxies , including H \alpha -emitter ( HAE ) 229 , HAE 131 , and the central Spiderweb Galaxy .
Star formation rates of \sim 500 - 1100 M _ { \odot } yr ^ { -1 } are estimated from the 7.7 \mu m PAH feature .
At such prodigious formation rates , the galaxy stellar masses will double in 0.6-1.1 Gyr .
We are viewing the peak epoch of star formation for these protocluster galaxies .
However , it appears that extinction of H \alpha is much greater ( up to a factor of 40 ) in the two ULIRG HAEs compared to the Spiderweb .
This may be attributed to different spatial distributions of star formation–nuclear star formation in the HAEs versus extended star formation in accreting satellite galaxies in the Spiderweb .
We find extremely luminous mid-IR rotational line emission from warm molecular hydrogen in the Spiderweb Galaxy , with L ( H _ { 2 } 0-0 S ( 3 ) ) = 1.4 \times 10 ^ { 44 } erg s ^ { -1 } ( 3.7 \times 10 ^ { 10 } L _ { \odot } ) , \sim 20 times more luminous than any previously known H _ { 2 } emission galaxy ( MOHEG ) .
Depending on temperature , this corresponds to a very large mass of > 9 \times 10 ^ { 6 } -2 \times 10 ^ { 9 } M _ { \odot } of T > 300 K molecular gas , which may be heated by the PKS 1138-26 radio jet , acting to quench nuclear star formation .
There is > 8 times more warm H _ { 2 } at these temperatures in the Spiderweb than what has been seen in low-redshift ( z < 0.2 ) radio galaxies , indicating that the Spiderweb may have a larger reservoir of molecular gas than more evolved radio galaxies .
This is the highest redshift galaxy yet in which warm molecular hydrogen has been directly detected .