Gases structures key in enabling stars’ formation: Milky Way’s cold gas clouds mapped in unprecedented detail

The MALS team is an international collaboration of researchers from around the world. The MeerKAT telescope is a facility of the National Research Foundation (NRF) in South Africa and is operated by the South African Radio Astronomy Observatory (SARAO).

The massive volume of raw survey data (1.6 petabytes) received from SARAO is hosted and processed at IUCAA using an automated pipeline built at IUCAA in collaboration with Thoughtworks Technologies India Private limited.

Gupta explained that hydrogen atoms may eventually transform into molecular gas, the basic fuel for the formation of stars. “Therefore, these cold gas structures are key to the conditions that enable star formation and are of significant interest for astronomers,” researchers said.

A hydrogen atom consists of an electron and a proton. Through their interaction it can produce a spectral line in emission or absorption at a wavelength of about 21 centimetres. The strength of this 21-cm spectral line of hydrogen in emission is insensitive to temperature and hence traces both cold and warm components of the gas. In turn, the absorption signal is more sensitive to colder phases.

“Over the last several decades, many astronomical surveys have tried to map the complex structures of the gas in the Milky Way in emission at 21-cm wavelength. Still, the absorption line measurements require more sensitive measurements and hence remained sparse. MALS changes this fundamentally with about 3,500 detections,” Gupta said.

“The simultaneous detection of this line in emission and absorption has the power to unravel the distribution of various thermal components and complex microphysics through which cold gas structures are formed,” Juergen Kerp, researcher at the University of Bonn in Germany for Multi-wavelength Studies, said in the report.

Vast volumes of MeerKAT data were processed using a sophisticated processing pipeline and data storage facility set up at IUCAA to generate the MALS catalogue. The MALS team combined this catalogue with the existing maps of 21-cm line emission, optical and far-infrared radiation to disentangle the distribution of the interwoven atomic gas phases.

“These multi-wavelength data allow us to establish relationships between the properties of the thermal components of atomic gas and the local conditions such as radiation and turbulence generated by the release of energy from stars.”, Sergei Balashev, researcher at Ioffe Institute, St. Petersburg, Russia, added.