“Dust, Ice, and Gas In Time” (DIGIT) Herschel Observations of GSS30-IRS1 in Ophiuchus

Abstract

As a part of the “Dust, Ice, and Gas In Time” (DIGIT) key program on Herschel, we observed GSS30-IRS1, a Class I protostar located in Ophiuchus (d = 120 pc), with Herschel/Photodetector Array Camera and Spectrometer. More than 70 lines were detected within a wavelength range from 50 to 200 μ m, including CO, H₂O, OH, and two atomic [O i] lines at 63 and 145 μ m. The [C ii] line, known as a tracer of externally heated gas by the interstellar radiation field (ISRF), is also detected at 158 μ m. All lines, except [O i] and [C ii], are detected only at the central spaxel of 9.″4 × 9.″4. The [O i] emissions are extended along a NE-SW orientation, and the [C ii] line is detected over all spaxels, indicative of an external photodissociation region. The total [C ii] intensity around GSS30 reveals that the far-ultraviolet radiation field is in the range of 3 to 20 {{G}₀}, where {{G}₀} is in units of the Habing Field, 1.6 × 10^-3 erg cm^-2 s^-1. This enhanced external radiation field heats the envelope of GSS30-IRS1, causing the continuum emission to be extended, unlike the molecular emission. The best-fit continuum model of GSS30-IRS1 with the physical structure including flared disk, envelope, and outflow shows that the internal luminosity is 10 {{L}_⊙ }, and the region is externally heated by a radiation field enhanced by a factor of 130 compared to the standard local ISRF.