CMWAVECLOUDS

Cm-wave continuum emission from molecular clouds

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 Obiettivo del progetto (Objective)

'The anomalous foreground was detected 10 years ago as an unexpected Galactic screen at cm-wavelengths in experiments designed to map the Cosmic Microwave Background (CMB), seen in the direction of cirrus interstellar dust clouds and ubiquitous at high Galactic latitudes. A joint Universidad de Chile (U. Ch.) and Caltech effort led to the discovery of surprisingly bright radio emission from canonical dark (i.e. dusty) clouds: rho Oph and M78, as well as translucent LDN1780 and zeta Oph. What is the nature of the cm-wave emitters? Do the dark clouds and the cirrus clouds radiate by the same emission mechanisms? The identification of the cm-wave sources is required to inform the subtraction of diffuse Galactic foregrounds from CMB polarization experiments. It may also provide a new diagnostic of the interstellar medium (ISM). The data on well studied local clouds can bring information on the environments giving rise to cm-wave radiation. The U. Ch. participant seeks to collaborate with the ISM team at the LUTh laboratory of the Observatoire de Paris, who has an established expertise on the theoretical modelling of ISM physical conditions. We aim at distinguishing between two broad interpretations of the cm-wave emission, based either on unexpected physical conditions, or a new astrophysical process: 1- Cold plasma radiation due to residual charges in molecular gas, such as CI continuum from the external layers (the photo-dissociation-regions) of clouds exposed to interstellar soft-UV radiation. If confirmed the CI continuum would trace unexpectedly dense and clumpy molecular gas in regions of intermediate-mass star formation. 2-The exciting possibility of spinning dust emission, which may provide the first direct probe of interstellar very small grains (such as polycyclic aromatic ydrocarbons). These poorly understood dust grains play a crucial role in the thermal and chemical balance of the atomic/molecular ISM.'

Introduzione (Teaser)

Bright emissions from interstellar space are baffling scientists and challenging the mapping of space. New observations and tests may help explain the phenomenon.

Descrizione progetto (Article)

While mapping the cosmic microwave background (CMB) a decade ago, scientists discovered unknown galactic radio emissions from molecular clouds. The exact source and mechanism behind these luminous emissions that emerge from interstellar dust clouds has been puzzling scientists for years.

The EU-funded 'Cm-wave continuum emission from molecular clouds' (CMwaveclouds) project focused on finding out more about these emissions, as well as about signals coming from the CMB.

The project has compared advanced astronomical observations that have already been documented with astrophysical models to help understand the phenomenon. CMwaveclouds is collecting information such as radio images of interstellar space through the Australia Telescope Compact Array interferometer (ATCA) and European Southern Observatory (ESO), among other facilities.

The datasets contain information that sheds light on the phenomenon. For example, the project found that radio emissions vary significantly in an interstellar region known as the Rho Ophiuchi cloud (ROPH). Also, no radio signal is emanating from the brightest infrared source in ROPH. Other observations include radio spectrum peaks under certain conditions, correlations between radio and infrared emissions, and energy release during hydrogen formation.

In another important undertaking, CMwaveclouds developed a physical model of ROPH that gives insight into radiation intensity fields, gas-phase density and temperature. The results of the observations and ROPH model are being published in the scientific community and serve to illuminate our understanding of interstellar emissions. This will allow scientists to map space more accurately, help explain its oddities and yield a novel diagnostic tool to explain interstellar environments more clearly.