Examinando por Autor "Grisdale, K."

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Acceso Abierto
Integral field spectroscopy of luminous infrared main-sequence galaxies at cosmic noon
(Oxford Academics: Oxford University Press, 2021-02-26) Hogan, L.; Rigopoulou, D.; Magdis, Georgios E.; Pereira Santaella, M.; García Bernete, I.; Thatte, N.; Grisdale, K.; Huang, J. S.; Science and Technology Facilities Council (STFC); Villum Fonden; Comunidad de Madrid; Magdis, G. E. [0000-0002-4872-2294]; Pereira Santaella, M. [0000-0002-4005-9619]; Grisdale, K. [0000-0003-0375-5997]
We present the results of an integral field spectroscopy survey of a sample of dusty (ultra) luminous infrared galaxies (U/LIRGs) at 2 < z < 2.5 using KMOS on the Very Large Telescope. The sample has been drawn from Herschel deep field surveys and benefits from ancillary multiwavelength data. Our goal is to investigate the physical characteristics, kinematics, and the drivers of star formation in the galaxies whose contribution dominates the peak of the cosmic star formation density. Two-thirds of the sample are main-sequence galaxies in contrast to the starburst nature of local U/LIRGs. Our kinematic study, unique in its focus on z ∼ 2 dusty star-forming galaxies, uses the H α emission line to find that ∼40 per cent appear to be isolated discs based on the ratio of rotational velocity to the velocity dispersion, suggesting steady-state mechanisms are sufficient to power the large star formation rates (SFRs). The ratio of obscured to unobscured star formation indicates the sample of galaxies experiences less dust obscuration compared to intermediate and local counterparts, while also hosting cooler dust than local U/LIRGs. In addition to H α we detect [N II] 6583 Å in our targets and show the gas-phase metallicities do not exhibit the metal deficiency of local U/LIRGs. These results indicate that, despite their extreme IR luminosity, the underlying mechanisms driving the massive SFRs found at cosmic noon are due to scaled up disc galaxies as opposed to mergers.
Restringido
Predicting the observability of population III stars with ELT-HARMONI via the helium 1640 Å emission line
(Oxford Academics: Oxford University Press, 2021-01-08) Grisdale, K.; Thatte, N.; Devriendt, J.; Pereira Santaella, M.; Slyz, A.; Kimm, T.; Dubois, Y.; Yi, S. K.; Science and Technology Facilities Council (STFC); National Research Foundation of Korea (NRF); 0000-0003-0375-5997
Population III (Pop. III) stars, as of yet, have not been detected, however as we move into the era of extremely large telescopes this is likely to change. One likely tracer for Pop. III stars is the He IIλ1640 emission line, which will be detectable by the HARMONI spectrograph on the European Extremely Large Telescope (ELT) over a broad range of redshifts (2 ≤ z ≤ 14). By post-processing galaxies from the cosmological, AMR-hydrodynamical simulation NEWHORIZON with theoretical spectral energy distributions (SED) for Pop. III stars and radiative transfer (i.e. the Yggdrasil Models and CLOUDY look-up tables, respectively) we are able to compute the flux of He IIλ1640 for individual galaxies. From mock 10 h observations of these galaxies we show that HARMONI will be able to detect Pop. III stars in galaxies up to z ∼ 10 provided Pop. III stars have a top heavy initial mass function (IMF). Furthermore, we find that should Pop. III stars instead have an IMF similar to those of the Pop. I stars, the He IIλ1640 line would only be observable for galaxies with Pop. III stellar masses in excess of 107M⊙⁠, average stellar age <1Myr at z = 4. Finally, we are able to determine the minimal intrinsic flux required for HARMONI to detect Pop. III stars in a galaxy up to z = 10.