We present an 8 pc \times 5 pc resolution view of the central \sim 200 pc region of the nearby starburst galaxy NGC 253 , based on ALMA Band 7 ( \lambda \simeq 0.85 mm or \nu \sim 350 GHz ) observations covering 11 GHz .
We resolve the nuclear starburst of NGC 253 into eight dusty star-forming clumps , 10 pc in scale , for the first time .
These clumps , each of which contains ( 4–10 ) \times 10 ^ { 4 } M _ { \odot } of dust ( assuming that the dust temperature is 25 K ) and up to 6 \times 10 ^ { 2 } massive ( O5V ) stars , appear to be aligned in two parallel ridges , while they have been blended in previous studies .
Despite the similarities in sizes and dust masses of these clumps , their line spectra vary drastically from clump to clump although they are separated by only \sim 10 pc .
Specifically , one of the clumps , Clump 1 , exhibits line confusion-limited spectra with at least 36 emission lines from 19 molecules ( including CH _ { 3 } OH , HNCO , H _ { 2 } CO , CH _ { 3 } CCH , H _ { 2 } CS , and H _ { 3 } O ^ { + } ) and a hydrogen recombination line ( H26 \alpha ) , while much fewer kinds of molecular lines are detected in some other clumps where fragile species , such as complex organic molecules and HNCO , completely disappear from their spectra .
We demonstrate the existence of hot molecular gas ( T _ { \mathrm { rot } } ( \mathrm { SO _ { 2 } } ) = 90 \pm 11 K ) in the former clump , which suggests that the hot and chemically rich environments are localized within a 10-pc scale star-forming clump .