DETECTION OF THE 158 μm [C II] TRANSITION AT z=1.3: EVIDENCE FOR A GALAXY-WIDE STARBURST

We report the detection of 158 mu m [C II] fine-structure line emission from MIPS J142824.0+352619, a hyperluminous (L-IR similar to 10(13) L-circle dot) starburst galaxy at z = 1.3. The line is bright, corresponding to a fraction L-[C II]/L-FIR approximate to 2 x 10(-3) of the far-IR (FIR) continuum. The [C II], CO, and FIR continuum emission may be modeled as arising from photodissociation regions (PDRs) that have a characteristic gas density of n similar to 10(4.2) cm(-3), and that are illuminated by a far-UV radiation field similar to 10(3.2) times more intense than the local interstellar radiation field. The mass in these PDRs accounts for approximately half of the molecular gas mass in this galaxy. The L-[C II]/L-FIR ratio is higher than observed in local ultraluminous infrared galaxies or in the few high-redshift QSOs detected in [C II], but the L-[C II]/L-FIR and L-CO/L-FIR ratios are similar to the values seen in nearby starburst galaxies. This suggests that MIPS J142824.0+352619 is a scaled-up version of a starburst nucleus, with the burst extended over several kiloparsecs.