The initial mass function based on the full-sky 20 pc census of ~3600 stars and brown dwarfs
A complete accounting of nearby objects—from the highest-mass white dwarf progenitors down to low-mass brown dwarfs—is now possible, thanks to an almost complete set of trigonometric parallax determinations from Gaia, ground-based surveys, and Spitzer follow-up. We create a census of objects within...
| Autores: | , , , , , , , , , , , , , , |
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| Formato: | artículo |
| Fecha de publicación: | 2024 |
| País: | España |
| Recursos: | Universitat Politècnica de Catalunya (UPC) |
| Repositorio: | UPCommons. Portal del coneixement obert de la UPC |
| Idioma: | inglés |
| OAI Identifier: | oai:upcommons.upc.edu:2117/429187 |
| Acesso em linha: | https://hdl.handle.net/2117/429187 https://dx.doi.org/10.3847/1538-4365/ad24e2 |
| Access Level: | acceso abierto |
| Palavra-chave: | Nearby objects White dwarf progenitors Brown dwarfs Trigonometric parallax Gaia data Ground-based surveys Spitzer follow-up Sun-centered sphere Binary systems Higher-order systems Volume-limited census Star formation products Initial mass function Stellar regime Substellar regime Mass function divergence Space densities Quadripartite power law Mass intervals Production rate Low-mass stars High-mass brown dwarfs Low-mass brown dwarfs Completeness correction Star to brown dwarf ratio Average mass per object. |
| Resumo: | A complete accounting of nearby objects—from the highest-mass white dwarf progenitors down to low-mass brown dwarfs—is now possible, thanks to an almost complete set of trigonometric parallax determinations from Gaia, ground-based surveys, and Spitzer follow-up. We create a census of objects within a Sun-centered sphere of 20 pc radius and check published literature to decompose each binary or higher-order system into its separate components. The result is a volume-limited census of ~3600 individual star formation products useful in measuring the initial mass function across the stellar (<8M¿) and substellar (¿5MJup) regimes. Comparing our resulting initial mass function to previous measurements shows good agreement above 0.8M¿ and a divergence at lower masses. Our 20 pc space densities are best fit with a quadripartite power law, , with long-established values of a = 2.3 at high masses (0.55 < M < 8.00M¿), and a = 1.3 at intermediate masses (0.22 < M < 0.55M¿), but at lower masses, we find a = 0.25 for 0.05 < M < 0.22M¿, and a = 0.6 for 0.01 < M < 0.05M¿. This implies that the rate of production as a function of decreasing mass diminishes in the low-mass star/high-mass brown dwarf regime before increasing again in the low-mass brown dwarf regime. Correcting for completeness, we find a star to brown dwarf number ratio of, currently, 4:1, and an average mass per object of 0.41 M¿. |
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