| Name | GT2_apon_1 |
| Title | High J Lines of CO as Tracers of Low Velocity Turbulent Shocks in Molecular Clouds |
| URL | http://archives.esac.esa.int/hsa/whsa-tap-server/data?retrieval_type=OBSERVATION&observation_id=1342248900&instrument_name=HIFI&product_level=LEVEL0&compress=true |
| DOI | https://doi.org/10.5270/esa-c3qg7u4 |
| Author | pon, a. |
| Description | Molecular clouds contain supersonic turbulence. Simulations of supersonic turbulence, which include magnetic fields, show that the turbulent energy decays rapidly via shocks. Although these simulations do not explicitly follow how the energy escapes a molecular cloud, shock heated gas will cool through line radiation, thereby altering the resulting molecular spectrum of the cloud. Thus, observations of the dominant molecular coolants provide observable tracers of the turbulent energy dissipation. We have computed models of low velocity, MHD shocks to determine which molecular species and transitions dominate the cooling and radiative energy release associated with shock cooling. By combining these models with an estimate for the turbulent energy dissipation rate from molecular clouds, we predict the strengths of these shock tracers. We find that the majority of the turbulent energy dissipated is emitted via CO rotational transitions. However, the observed low J transitions from CO in these clouds are dominated by emission from the surface layer PDR and the ambient, cool CO located throughout the cloud. The shock signature is only separable at the higher rotational transitions, J = 5-4 and up, where the emission from shock heated gas becomes dominant. The shock emission at these higher transitions is relatively weak, as these transitions are already past the emission peak of the CO ladder. Thus, to detect this unique turbulent energy dissipation signature, we require Herschel.s exceptional sensitivity. We propose to use HIFI to observe the CO J = 5-4 and 6-5 transitions towards a nearby low mass star forming region, Perseus B1-E, to verify whether shocked gas is actually present in the region. By observing multiple lines, we can determine both the temperature of the shocked gas and the characteristic shock strength. We will therefore be able to observationally constrain the turbulent energy dissipation rate in Perseus B1-E and compare this value against the predictions of supersonic turbulence decay. |
| Publication |
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| Instrument | HIFI_HifiPoint_fs |
| Temporal Coverage | 2012-07-31T01:26:46Z/2012-08-10T20:38:41Z |
| Version | SPG v14.1.0 |
| Mission Description | Herschel was launched on 14 May 2009! It is the fourth cornerstone mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities. |
| Creator Contact | https://support.cosmos.esa.int/h®erschel/ |
| Date Published | 2013-02-10T19:29:44Z |
| Keywords | Herschel, HSC, submillimetre, far-infrared, HIFI, PACS, SPIRE |
| Publisher And Registrant | European Space Agency |
| Credit Guidelines | European Space Agency, pon et al., 2013, 'High J Lines of CO as Tracers of Low Velocity Turbulent Shocks in Molecular Clouds', SPG v14.1.0, European Space Agency, https://doi.org/10.5270/esa-c3qg7u4 |