Dr James Urquhart, Head of the Centre for Astrophysics and Planetary Sciences at the School of Physical Sciences, has co-led international research exploring the molecular gas content of the Milky Way.
The research team used an APEX1 submillimeter telescope in 5100 m altitude in Chile to map an extended part of the Southern Galactic plane covering an area of more than 80 square degrees. With a velocity resolution of 0.25 km/s, this provided the morphology, distance information and kinematics of all Galactic molecular clouds in approximately 2/3 of the inner Milky Way disk.
The resulting survey, called SEDIGISM (Structure, Excitation and Dynamics of the Inner Galactic Interstellar Medium), reveals a wide range of structures, from individual star-forming clumps to giant molecular clouds and complexes. SEDIGISM allowed the international team of around 50 astronomers to study the distribution of cold molecular clouds and the amount of star formation in the inner region of the Milky Way in unprecedented detail.
A set of three publications have been published in Monthly Notices of the Royal Astronomical Society detailing the findings of the survey, which represent a significant step forward in understanding the structure of the Galaxy. The three publications were led by Drs Frederic Schuller (Max Planck Institute for Radio Astronomy (MPIfR)), Ana Duarte-Cabral (Cardiff University) and James Urquhart (Kent) respectively. Data was collected during the period of 2013-2017.
Dr Urquhart said: ‘In conjunction with the previous survey of cold dust emission in the Galaxy (ATLASGAL2), the fraction of clouds associated with dense gas could be estimated: only 10% of the clouds are sites of ongoing star formation. Molecular clouds consist of the raw material from which new stars form. Imaging these clouds is therefore significant in deriving important parameters such as the star formation efficiency in our Galaxy. Our data will add value to a number of recent Galactic plane surveys by providing insight into the formation and evolution of molecular clouds and will contribute to the ongoing process of understanding the structure and dynamics of the Milky Way.’
Dr Urquhart was supported by two Kent undergraduates, Molly Wells and Joe Cross, who are co-authored on his research paper ‘SEDIGISM-ATLASGAL: Dense Gas Fraction and Star Formation Efficiency Across the Galactic Disk.’
The three research papers published as a series by the Monthly Notices of the Royal Astronomical Society are:
‘The SEDIGISM survey: first data release and overview of the Galactic structure’ – Dr Frederic Schuller et al. DOI: 10.1093/mnras/staa2369
‘The SEDIGISM survey: Molecular clouds in the inner Galaxy’ – Dr Ana Duarte-Cabral et al. DOI: 10.1093/mnras/staa2480
‘SEDIGISM-ATLASGAL: Dense Gas Fraction and Star Formation Efficiency Across the Galactic Disk’ – Dr James Urquhart et al. DOI: 10.1093/mnras/staa2512
 APEX, the Atacama Pathfinder Experiment, is a collaboration between the Max Planck Institute for Radio Astronomy (MPIfR), the European Southern Observatory (ESO) and the Onsala Space Observatory (OSO) to construct and operate, since 2005, a single dish telescope on the Chajnantor plateau at an altitude of 5,100 metres above sea level (Atacama Desert, Chile).
 ATLASGAL, the APEX Telescope Large Area Survey of the Galaxy, is a collaboration between the Max Planck Institute for Radio Astronomy (MPIfR), the Max Planck Institute for Astronomy (MPIA), and scientists from the ESO community and the University of Chile.