144 research outputs found

    Superbosses feel completely unthreatened

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    In contrast, most managers claim to be comfortable hiring the best people, but they aren't, writes Sydney Finkelstei

    Investigating the growing population of massive quiescent galaxies at cosmic noon

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    We explore the build-up of quiescent galaxies using a sample of 28 469 massive (M⋆ ≄ 1011 M☉) galaxies at redshifts 1.5 < zz < 3.0, drawn from a 17.5 deg2 area (0.33 Gpc3 comoving volume at these redshifts). This allows for a robust study of the quiescent fraction as a function of mass at 1.5 < zz < 3.0 with a sample ∌40 times larger at log(M⋆/ M⊙)≄11.5M⊙)≄11.5 than previous studies. We derive the quiescent fraction using three methods: specific star formation rate, distance from the main sequence, and UVJ colour-colour selection. All three methods give similar values at 1.5 < zz < 2.0, however the results differ by up to a factor of 2 at 2.0 < zz < 3.0. At redshifts 1.5 < zz < 3.0, the quiescent fraction increases as a function of stellar mass. By zz = 2, only 3.3 Gyr after the big bang, the universe has quenched ∌25 per cent of M⋆ = 1011 M☉ galaxies and ∌45 per cent of M⋆ = 1012 M☉ galaxies. We discuss physical mechanisms across a range of epochs and environments that could explain our results. We compare our results with predictions from hydrodynamical simulations SIMBA and IllustrisTNG and semi-analytic models (SAMs) SAG, SAGE, and Galacticus. The quiescent fraction from IllustrisTNG is higher than our empirical result by a factor of 2-5, while those from SIMBA and the three SAMs are lower by a factor of 1.5-10 at 1.5 < zz < 3.0Fil: Sherman, Sydney. Department Of Astronomy; Estados UnidosFil: Jogee, Shardha. Department Of Astronomy; Estados UnidosFil: Florez, Jonathan. Department Of Astronomy; Estados UnidosFil: Stevans, Matthew L. Department Of Astronomy; Estados UnidosFil: Kawinwanichakij, Lalitwadee. Kavli Institute For The Physics And Mathematics Of The; JapĂłnFil: Wold, Isak. Nasa Goddard Space Flight Center; Estados UnidosFil: Finkelstein, Steven L. Department Of Astronomy; Estados UnidosFil: Papovich, Casey. Department Of Physics And Astronomy; Estados UnidosFil: Ciardullo, Robin. Department Of Astronomy And Astrophysics; Estados UnidosFil: Gronwall, Caryl. Department Of Astronomy And Astrophysics; Estados UnidosFil: Cora, Sofia Alejandra. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - La Plata. Instituto de AstrofĂ­sica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂ­sicas. Instituto de AstrofĂ­sica La Plata; ArgentinaFil: Hough, Tomas. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - La Plata. Instituto de AstrofĂ­sica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂ­sicas. Instituto de AstrofĂ­sica La Plata; ArgentinaFil: Vega MartĂ­nez, Cristian Antonio. Instituto de InvestigaciĂłn Multidisciplinar En Ciencia; Chil
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