Examinando por Autor "Bower, Richard G."
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Ítem Gemini Observations of Galaxies in Rich Early Environments (GOGREEN) I: Survey description(Oxford University Press, 2017-10) Balogh, Michael L.; Gilbank, David G.; Muzzin, Adam; Rudnick, Gregory; Cooper, Michael C.; Lidman, Chris; Biviano, Andrea; Demarco, Ricardo; McGee, Sean L.; Nantais, Julie B.; Noble, Allison; Old, Lyndsay; Wilson, Gillian; Yee, Howard K.C.; Bellhouse, Callum; Cerulo, Pierluigi; Chan, Jeffrey; Pintos-Castro, Irene; Simpson, Rane; van der Burg, Remco F.J.; Zaritsky, Dennis; Ziparo, Felicia; Alonso, María Victoria; Bower, Richard G.; Lucia, Gabriella De; Finoguenov, Alexis; Lambas, Diego Garcia; Muriel, Hernan; Parker, Laura C.; Rettura, Alessandro; Valotto, Carlos; Wetzel, AndrewWe describe a new Large Program in progress on the Gemini North and South telescopes: Gemini Observations of Galaxies in Rich Early Environments (GOGREEN). This is an imaging and deep spectroscopic survey of 21 galaxy systems at 1 < z < 1.5, selected to span a factor >10 in halo mass. The scientific objectives include measuring the role of environment in the evolution of low-mass galaxies, and measuring the dynamics and stellar contents of their host haloes. The targets are selected from the SpARCS, SPT, COSMOS, and SXDS surveys, to be the evolutionary counterparts of today's clusters and groups. The newred-sensitive Hamamatsu detectors on GMOS, coupled with the nod-and-shuffle sky subtraction, allow simultaneous wavelength coverage over λ ~ 0.6-1.05 μm, and this enables a homogeneous and statistically complete redshift survey of galaxies of all types. The spectroscopic sample targets galaxies with AB magnitudes z' < 24.25 and [3.6] μm < 22.5, and is therefore statistically complete for stellar masses M* ≳ 1010.3M⊙, for all galaxy types and over the entire redshift range. Deep, multiwavelength imaging has been acquired over larger fields for most systems, spanning u through K, in addition to deep IRAC imaging at 3.6 μm. The spectroscopy is ~50 per cent complete as of semester 17A, and we anticipate a final sample of ~500 new cluster members. Combined with existing spectroscopy on the brighter galaxies from GCLASS, SPT, and other sources, GOGREEN will be a large legacy cluster and field galaxy sample at this redshift that spectroscopically covers a wide range in stellar mass, halo mass, and clustercentric radius. © 2017 The Authors.Ítem The abundances and properties of Dual AGN and their host galaxies in the EAGLE simulations(Monthly Notices of the Royal Astronomical Society, 2019-02-21) Rosas-Guevara, Yetli M.; Bower, Richard G.; McAlpine, Stuart; Bonoli, Silvia; Tissera, Patricia B.We look into the abundance of Dual AGN (active galactic nucleus) in the largest hydrodynamical simulation from the Evolution and Assembly of GaLaxies and their Environment (EAGLE) project. We define a Dual AGN as two active black holes (BHs) with a separation below 30 kpc. We find that only 1 per cent of AGN with LHX ≥ 1042 erg s-1 are part of a Dual AGN system at z = 0.8-1. During the evolution of a typical binary BH system, the rapid variability of the hard X-ray luminosity on Myr time-scales severely limits the detectability of Dual AGN. To quantify this effect, we calculate a probability of detection, ton/t30, where t30 is the time in which the two BHs are separated at distances below 30 kpc and ton, the time that both AGNs are visible (e.g. when both AGNs have LHX ≥ 1042 erg s-1) in this period. We find that the average fraction of visible Dual systems is 3 per cent. The visible Dual AGN distribution as a function of BH separation presents a pronounced peak at ∼20 kpc that can be understood as a result of the rapid orbital decay of the host galaxies after their first encounter. We also find that 75 per cent of the host galaxies have recently undergone or are undergoing a merger with stellar mass ratio ≥0.1. Finally, we find that the fraction of visible Dual AGN increases with redshift as found in observations.Ítem The oxygen abundance gradients in the gas discs of galaxies in the EAGLE simulation(Oxford University Press, 2019) Tissera, Patricia B.; Rosas-Guevara, Yetli; Bower, Richard G.; Crain, Robert A.; Lagos, Claudia del P.; Schaller, Matthieu; Schaye, Joop; Theuns, TomWe use the EAGLE simulations to study the oxygen abundance gradients of gas discs in galaxies within the stellar mass range [109.5, 1010.8] ∼M at z = 0. The estimated median oxygen gradient is -0.011 ± 0.002 dex kpc-1, which is shallower than observed. No clear trend between simulated disc oxygen gradient and galaxy stellar mass is found when all galaxies are considered. However, the oxygen gradient shows a clear correlation with gas disc size so that shallower abundance slopes are found for increasing gas disc sizes. Positive oxygen gradients are detected for ∼40 per cent of the analysed gas discs, with a slight higher frequency in low-mass galaxies. Galaxies that have quiet merger histories show a positive correlation between oxygen gradient and stellar mass, so that more massive galaxies tend to have shallowermetallicity gradients. At high stellarmass, there is a larger fraction of rotationaldominated galaxies in low-density regions. At low stellar mass, non-merger galaxies show a large variety of oxygen gradients and morphologies. The normalization of the disc oxygen gradients in non-merger galaxies by the effective radius removes the trend with stellar mass. Conversely, galaxies that experienced mergers show a weak relation between oxygen gradient and stellar mass. Additionally, the analysed EAGLE discs show no clear dependence of the oxygen gradients on local environment, in agreement with current observational findings.