A global view on star formation: The GLOSTAR Galactic plane survey. IV. Radio continuum detections of young stellar objects in the Galactic Centre region

Context. The Central Molecular Zone (CMZ), a ∼200 pc size region around the Galactic Centre, is peculiar in that it shows a star formation rate (SFR) that is suppressed with respect to the available dense gas. To study the SFR in the CMZ, young stellar objects (YSOs) can be investigated. Here we present radio observations of 334 2.2 µm infrared sources that have been identified as YSO candidates.Aims. Our goal is to investigate the presence of centimetre wavelength radio continuum counterparts to this sample of YSO candidates which we use to constrain the current SFR in the CMZ.Methods. As part of the GLOSTAR survey, D-configuration VLA data was obtained for the Galactic Centre, covering −2◦ < l < 2◦and−1◦ < b < 1◦ with a frequency coverage of 4–8 GHz. We match YSOs with radio continuum sources based on selection criteria and classify these radio sources as potential Hii regions and determine their physical properties.Results. Of the 334 YSO candidates, we found 35 with radio continuum counterparts. We find that 94 YSOs are associated with dense dust condensations identified in the 870 µm ATLASGAL survey, of which 14 have a GLOSTAR counterpart. Of the 35 YSOs with radio counterparts, 11 are confirmed as Hii regions, based on their spectral indices and literature. We estimate their Lyman continuum photon flux in order to estimate the mass of the ionising star. Combining these with known sources, the present day star formation rate in the CMZ is calculated to be ∼0.068 M� yr−1 which is ∼6.8% of the Galactic SFR. Candidate YSOs that lack radio counterparts may not have yet evolved to the stage of exhibiting an Hii region or, conversely, are older and have dispersed their natal clouds. Since manylack dust emission, the latter is more likely. Our SFR estimate in the CMZ is in agreement with previous estimates in the literature.