TheGaia-ESO survey: Discovery of a spatially extended low-mass population in the Vela OB2 association

Abstract

The nearby (distance ∼ 350-400 pc), rich Vela OB2 association, includes γ 2 Velorum, one of the most massive binaries in the solar neighbourhood and an excellent laboratory for investigating the formation and early evolution of young clusters. Recent Gaia-ESO survey observations have led to the discovery of two kinematically distinct populations in the young (10-15 Myr) cluster immediately surrounding γ 2 Velorum. Here we analyse the results of Gaia-ESO survey observations of NGC 2547, a 35 Myr cluster located two degrees south of γ 2 Velorum. The radial velocity distribution of lithium-rich pre-main sequence stars shows a secondary population that is kinematically distinct from and younger than NGC 2547. The radial velocities, lithium absorption lines, and the positions in a colour-magnitude diagram of this secondary population are consistent with those of one of the components discovered around γ 2 Velorum. This result shows that there is a young, low-mass stellar population spread over at least several square degrees in the Vela OB2 association. This population could have originally been part of a cluster around γ 2 Velorum that expanded after gas expulsion or formed in a less dense environment that is spread over the whole Vela OB2 region.

Unbound Young Stellar Systems: Star Formation on the Loose

“…The first stellar component is found to be 1 to 2 Myr older, and is probably more centrally concentrated around g 2 Vel. A kinematically distinct component was also found in the young (∼35 Myr) cluster NGC 2547, also in Vela OB2, which appears more similar to one of the g 2 Vel components (Sacco et al 2015). These studies depict a young, low-mass stellar population spread over several square degrees in the Vela OB2 association.…”

“…The first, studied by Jeans (1902), 8 addresses the balance between self-gravity and thermal pressure. The second scale results from the analysis by Toomre (1964), originally studied by Safronov (1960), which considers also shear forces from differential rotation in addition to gravity and pressure. In a galaxy with a global stellar spiral density wave or a stellar ring, large scale dynamics lead to gaseous structures like the so-called beads on a string and spurs (e.g., Renaud et al 2014;Schinnerer et al 2013).…”

The C12(α,γ)O16deBoer1, Görres2, Wiescher3 et al. 2017Rev. Mod. Phys.19981431View full textAdd to dashboardCite

“…This bonanza of physical puzzles is closely linked with compact object formation by corecollapse supernovae (e.g., Eldridge and Tout, 2004;Özel et al, 2010;Perego et al, 2015;Sukhbold et al, 2016;Suwa et al, 2015;Timmes et al, 1996) and the diversity of observed massive star transients (e.g., Ofek et al, 2014;Smith et al, 2016;Van Dyk et al, 2000). Recent observational clues that challenge conventional wisdom (Boggs et al, 2015;Jerkstrand et al, 2015;Strotjohann et al, 2015;Vreeswijk et al, 2014;Zavagno et al, 2010), coupled with the expectation of large quantities of data from upcoming surveys (e.g., Creevey et al, 2015;Papadopoulos et al, 2015;Sacco et al, 2015;Yuan et al, 2015), new measurements of key nuclear reaction rates and techniques for assessing reaction rate uncertainties Wiescher et al, 2012), and advances in 3D pre-SN modeling (Couch et al, 2015;Jones et al, 2017;Müller et al, 2016), offer significant improvements in our quantitative understanding of the end states of massive stars.…”

Solar and stellar photospheric abundances

“…The observations started at the end of 2012, the raw spectra are quickly made public on the ESO archive, and the advanced data products (fully reduced spectra, radial velocities and stellar parameters including abundances) are following on a fastpaced schedule. There are plenty of examples of science results from this project (e.g., Magrini et al 2015;Lind et al 2015;Sacco et al 2015).…”