A census of OB stars within 1 kpc and the star formation and core-collapse supernova rates of the Milky Way

A census of OB stars within 1 kpc and the star formation and core-collapse supernova rates of the Milky Way

OB stars are vital tools to study Galactic structure, star formation, stellar feedback and multiplicity. The availability of modern astronomical surveys, and particularly Gaia, offers an opportunity to provide more extensive and accurate 3D maps of OB stars than ever, which can then serve as targets for spectroscopic follow-up and to locate gravitational wave progenitors. In this work, I have compiled a census of 24,706 O- and B-type stars within 1 kpc of the Sun, by applying evolutionary and atmospheric model fits to observed SEDs compiled from astro-photometric survey data. I have characterized and mapped out these OB stars, finding overdensities that correspond to known OB associations and massive star-forming regions such as Sco-Cen, Orion OB1, Vela OB2, Cepheus and Circinus. To check the quality of this new catalogue, I have compared it with spectroscopic samples (such as the Apsis modules from Gaia DR3), as well as with similar catalogues of OB(A) stars, OB

associations, star-forming regions and young open clusters. I have also exploited this list of OB stars to estimate their scale height, the local star formation rate and the local core-collapse supernova rate. I extrapolated these rates to the entire Milky Way, allowing me to derive a Galactic star formation rate of 0.67 solar masses per year and a core-collapse supernova rate of 0.4-0.5 per century. These are slightly

lower than previous estimates, that I attribute to improvements in the census of OB stars and stellar evolutionary models. Finally, I have found a near-Earth core collapse supernova rate of 1 every 400 million years. This value is consistent with the scenario of a nearby supernova explosion causing one of the recorded mass extinction events on Earth.