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

TL;DR

This study uses Herschel observations to analyze the physical conditions and external radiation environment of the Class I protostar GSS30-IRS1 in Ophiuchus, revealing external heating effects and detailed molecular line emissions.

Contribution

First detailed Herschel/PACS spectral analysis of GSS30-IRS1 highlighting external UV radiation influence and physical structure modeling.

Findings

Detected over 70 spectral lines including CO, H2O, OH, [O I], and [C II]

External UV radiation field is 3 to 20 G0, heating the protostar's envelope

Internal luminosity of GSS30-IRS1 is approximately 10 Lsun

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 (PACS). More than 70 lines were detected within a wavelength range from 50 micron to 200 micron, including CO, H2O, OH, and two atomic [O I] lines at 63 and 145 micron. The [C II] line, known as a tracer of externally heated gas by the interstellar radiation field, is also detected at 158 micron. All lines, except [O I] and [C II], are detected only at the central spaxel of 9.4" X 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 external PDR. The total [C II] intensity around GSS30 reveals that the far-ultraviolet radiation field is in the range of 3 to 20 G0, where G0 is in units of the Habing Field, 1.6 X 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 Lsun, and the region is externally heated by a radiation field enhanced by a factor of 130 compared to the standard local interstellar radiation field.