We present new ALMA observations and physical properties of a Lyman Break Galaxy at z = 7.15 .
Our target , B14-65666 , has a bright ultra-violet ( UV ) absolute magnitude , M _ { UV } \approx - 22.4 , and has been spectroscopically identified in Ly \alpha with a small rest-frame equivalent width of \approx 4 Å .
Previous HST image has shown that the target is comprised of two spatially separated clumps in the rest-frame UV .
With ALMA , we have newly detected spatially resolved [ O iii ] 88 \micron , [ C ii ] 158 \micron , and their underlying dust continuum emission .
In the whole system of B14-65666 , the [ O iii ] and [ C ii ] lines have consistent redshifts of 7.1520 \pm 0.0003 , and the [ O iii ] luminosity , \textcolor black ( 34.4 \pm 4.1 ) \times 10 ^ { 8 } L _ { \odot } , is \textcolor blackabout three times higher than the [ C ii ] luminosity , ( 11.0 \pm 1.4 ) \times 10 ^ { 8 } L _ { \odot } . \textcolor blackWith our two continuum flux densities , the dust temperature is constrained to be T _ { d } \approx 50 - 60 K under the assumption of the dust emissivity index of \beta _ { d } = 2.0 - 1.5 , leading to a large total infrared luminosity of L _ { TIR } \approx 1 \times 10 ^ { 12 } L _ { \odot } .
Owing to our high spatial resolution data , \textcolor blackwe show that the [ O iii ] and [ C ii ] emission can be spatially decomposed into two clumps associated with the two rest-frame UV clumps whose spectra are kinematically separated by \approx 200 km s ^ { -1 } .
We also find these two clumps have comparable UV , infrared , [ O iii ] , and [ C ii ] luminosities .
Based on these results , we argue that B14-65666 is a starburst galaxy induced by a major-merger .
The merger interpretation is also supported by the large specific star-formation rate ( defined as the star-formation rate per unit stellar mass ) , sSFR = 260 ^ { +119 } _ { -57 } Gyr ^ { -1 } , inferred from our SED fitting .
Probably , a strong UV radiation field caused by intense star formation contributes to its high dust temperature and the [ O iii ] -to- [ C ii ] luminosity ratio .