Feature story – Detection of an Anomalous Hot Gas Component in a Low Mass Star-Forming Region
By Andy Pon (2014 Plaskett medal recipient; Leeds University)
Using HIFI on Herschel, the CO (5-4) and CO (6-5) transitions were observed towards the centre of Perseus B1-E5, a starless condensation in the Perseus molecular cloud, which is a nearby low mass star-forming region. HIFI obtained strong detections of two separate velocity components in both transitions.
Photodissociation region (PDR) models from the Kaufman et al. (1996), KOSMA-tau, and Meudon codes were compared to a spectral energy diagram composed of the HIFI data and archival data of lower J CO lines. The PDR models were able to account for the emission in the CO (1-0), (3-2) and (5-4) lines, but every model that fit these lower lines significantly underpredicted the integrated intensity of the (6-5) line. This inability
of the PDR models to consistently account for the CO (6-5) emission implies that there is a warm gas component within B1-E5 that is not included in standard PDR models.
Given the lack of any protostars or protostellar outflows in the vicinity of B1-E5, the most plausible source of this warm gas is the dissipation of turbulence in low velocity shocks. The observed emission is consistent with the turbulent energy dissipating on a timescale a factor of three larger than the turbulent crossing time. Only 0.15% of the gas within B1-E5 would need to be shock heated by 3 km/s shocks to explain the observed CO (6-5) integrated intensities.
This work is described in more detail in Pon et al. (2014, MNRAS, 445, 1508).
Herschel Interactive Processing Environment (HIPE)
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Conferences, workshops and webinars related to Herschel
- ALMA/Herschel Archival Workshop
ESO-Garching, Germany, 15-17 April 2015
- From interstellar clouds to star-forming galaxies: Universal processes?
IAU Symposium 315, Honolulu, HI, USA, 3-7 August 2015