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Haloes at the ragged edge: the importance of the splashback radius
Snaith, O. N.,Bailin, J.,Knebe, A.,Stinson, G.,Wadsley, J.,Couchman, H. Oxford University Press 2017 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.472 No.3
<P>We have explored the outskirts of dark matter haloes out to 2.5 times the virial radius using a large sample of haloes drawn from Illustris, along with a set of zoom simulations (MUGS). Using these, we make a systematic exploration of the shape profile beyond Rvir. In the mean sphericity profile of Illustris haloes, we identify a dip close to the virial radius, which is robust across a broad range of masses and infall rates. The inner edge of this feature may be related to the virial radius and the outer edge with the splashback radius. Due to the high halo-to-halo variation, this result is visible only on average. However, in four individual haloes in the MUGS sample, a decrease in the sphericity and a subsequent recovery is evident close to the splashback radius. We find that this feature persists for several Gyr, growing with the halo. This feature appears at the interface between the spherical halo density distribution and the filamentary structure in the environment. The shape feature is strongest when there is a high rate of infall, implying that the effect is due to the mixing of accreting and virializing material. The filamentary velocity field becomes rapidlymixed in the halo region inside the virial radius, with the area between this and the splashback radius serving as the transition region. We also identify a long-lasting and smoothly evolving splashback region in the radial density gradient in many of the MUGS haloes.</P>
Haywood, Misha,Di Matteo, Paola,Lehnert, Matthew,Snaith, Owain,Fragkoudi, Francesca,Khoperskov, Sergey Springer-Verlag 2018 Astronomy and astrophysics Vol.618 No.-
<P>We show that the bulge and the disk of the Milky Way (MW) at <I>R</I> ≲ 7 kpc are well described by a unique chemical evolution and a two-phase star formation history (SFH). We argue that the populations within this inner disk, not the entire disk, are the same, and that the outer Lindblad resonance (OLR) of the bar plays a key role in explaining this uniformity. In our model of a two-phase SFH, the metallicity, [<I>α</I>/Fe] and [<I>α</I>/H] distributions, and age-metallicity relation are all compatible with the observations of both the inner disk and bulge. The dip at [Fe/H] ∼ 0 dex seen in the metallicity distributions of the bulge and inner disk reflects the quenching episode in the SFH of the inner MW at age ∼8 Gyr, and the common evolution of the bulge and inner disk stars. Our results for the inner region of the MW, <I>R</I> ≲ 7 kpc, are consistent with a rapid build-up of a large fraction of its total baryonic mass within a few billion years. We show that at <I>z</I> ≤ 1.5, when the MW was starting to quench, transitioning between the end of the <I>α</I>-enhanced thick disk formation to the start of the thin disk, and yet was still gas rich, the gas accretion rate could not have been significant. The [<I>α</I>/Fe] abundance ratio before and after this quenching phase would be different, which is not observed. The decrease in the accretion rate and gas fraction at <I>z</I> ≤ 2 was necessary to stabilize the disk allowing the transition from thick to thin disks, and for beginning the secular phase of the MW’s evolution. This possibly permitted a stellar bar to develop which we hypothesize is responsible for quenching the star formation. The present analysis suggests that MW history, and in particular at the transition from the thick to the thin disk - the epoch of the quenching - must have been driven by a decrease of the star formation efficiency. We argue that the decline in the intensity of gas accretion, the formation of the bar, and the quenching of the star formation rate (SFR) at the same epoch may be causally connected thus explaining their temporal coincidence. Assuming that about 20% of the gas reservoir in which metals are diluted is molecular, we show that our model is well positioned on the Schmidt-Kennicutt relation at all times.</P>
Song, S.,Horantner, M.,Choi, K.,Snaith, H.,Park, T. Royal Society of Chemistry 2017 Journal of materials chemistry. A, Materials for e Vol.5 No.8
<P>We introduce 1 step pin-hole free CH(3)NH(3)PbI(3-x)C(l)x perovskite layers by using heated airflow during the nucleation stage of the perovskite. Upon employing heated air, we stimulate uniformly distributed nuclei growth, resulting in a pin-hole free planar perovskite layer. We find an optimized heated airflow of 100 degrees C as the optimized condition. The resulting planar device employing a conventional TiO2 electron transporting layer exhibits 17.6% average power conversion efficiency with 14.3% maximum powerpoint (MPP) efficiency. In addition, our method gives a very reproducible perovskite layer. Thus, our pin-hole free perovskite layer allows for 14.9% efficiency in a larger area device (0.71 cm(2)) that is generally prone to shunting paths.</P>