The coordinated radio and infrared survey for high-mass star formation

III. A catalogue of northern ultra-compact H II regions^★

¹ School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
e-mail: pyiek@leeds.ac.uk
² Centre for Astrophysics and Planetary Science, University of Kent, Canterbury CT2 7NH, UK
³ Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, 58089 Morelia, Michoacán, Mexico
⁴ Research Centre for Astronomy, Astrophysics, and Astrophotonics, Macquarie University, NSW 2109, Australia
⁵ Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006, Australia
⁶ Jodrell Bank Centre for Astrophysics, Alan Turing Building, School of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester M13 9PL, UK

Received: 30 January 2018
Accepted: 21 March 2018

Abstract

A catalogue of 239 ultra-compact H II  regions (UCHIIs) found in the CORNISH survey at 5 GHz and 1.5″ resolution in the region 10° < l < 65°,  |b| < 1° is presented. This is the largest complete and well-selected sample of UCHIIs to date and provides the opportunity to explore the global and individual properties of this key state in massive star formation at multiple wavelengths. The nature of the candidates was validated, based on observational properties and calculated spectral indices, and the analysis is presented in this work. The physical sizes, luminosities and other physical properties were computed by utilising literature distances or calculating the distances whenever a value was not available. The near- and mid-infrared extended source fluxes were measured and the extinctions towards the UCHIIs were computed. The new results were combined with available data at longer wavelengths and the spectral energy distributions (SEDs) were reconstructed for 177 UCHIIs. The bolometric luminosities obtained from SED fitting are presented. By comparing the radio flux densities to previous observational epochs, we find about 5% of the sources appear to be time variable. This first high-resolution area survey of the Galactic plane shows that the total number of UCHIIs in the Galaxy is ~750 – a factor of 3–4 fewer than found in previous large area radio surveys. It will form the basis for future tests of models of massive star formation.