Star formation and accretion rates within 500 pc as traced by <i>Gaia</i> DR3 XP spectra
L. Delfini, Miguel Vioque, Álvaro Ribas, S. T. Hodgkin
Abstract
Context. Accretion rates from protoplanetary discs onto forming stars are a key ingredient in star formation and protoplanetary disc evolution. Extensive efforts surveying different individual star-forming regions with spectroscopy and narrow-band photometry have been made to derive accretion rates on large populations of young stellar objects (YSOs). Aims. We use Gaia DR3 XP spectra to perform the first all-sky homogeneous analysis of YSO accretion properties within 500 pc. Methods. We characterise the H line emission of YSOs within 500 pc by using the H pseudo-equivalent widths and XP spectra provided by Gaia DR3. We derive accretion luminosities and mass accretion rates, together with stellar parameters, for 145 975 all-sky candidate YSO H emitters. We describe filtering strategies to select specific sub-samples of YSOs from this catalogue. Results. We identify a large population of low-accreting YSO candidates untraced by previous accretion rates surveys. We find previous surveys have mostly focused on YSO populations with significant infrared excess from disc emission. The population of low-accreting YSOs is mostly spatially dispersed, away from star-forming regions or the more clustered environments of star formation. Many YSOs appear entirely disconnected from young populations, and they are reminiscent of the long-lived ‘Peter Pan’ YSOs. We find L acc ∝ L ⋆ 1.41 ± 0.02 and Ṁ acc ∝ M ⋆ 2.4 ± 0.1 for the purest all-sky sample of YSO candidates. By fitting an exponential function to the fraction of accreting stars in clusters of different ages in the Sco-Cen complex, we obtain an accretion timescale of τ acc = 2.7 ± 0.4 Myr. The percentage of accretors found by fitting a power law function is 70% at 2 Myr and 2.8% at 10 Myr. Conclusions. With this new catalogue of H emitters, we significantly increase the number of YSO candidates with accretion rate estimations in the local neighbourhood. This allows us to study accretion timescales and the spatial and physical properties of YSO accretion from a large, all-sky, and homogeneous sample for the first time.