Семинар 124 – 18 сентября 2019 г.


Ольга Сильченко

Презентация

1909.04048 HALOGAS: the properties of extraplanar HI in disc galaxies

A. Marasco, F. Fraternali, G. Heald, W. J. G. de Blok, T. Oosterloo, P. Kamphuis, G. I. G. Jozsa, C. J. Vargas, B. Winkel, R. A. M. Walterbos, R. J. Dettmar, E. Jutte

Published 2019-09-09, 27 pages, 14 figures, 4 tables. Accepted for publication in A&A

We present a systematic study of the extraplanar gas (EPG) in a sample of 15nearby late-type galaxies at intermediate inclinations using publiclyavailable, deep interferometric HI data from the HALOGAS survey. For eachsystem we mask the HI emission coming from the regularly rotating disc and usesynthetic datacubes to model the leftover "anomalous" HI flux. Our modelconsists of a smooth, axisymmetric thick component described by 3 structuraland 4 kinematical parameters, which are fit to the data via a Bayesian MCMCapproach. We find that extraplanar HI is nearly ubiquitous in disc galaxies, aswe fail to detect it in only two of the systems with the poorest spatialresolution. The EPG component encloses ~5-25% of the total HI mass, with a meanvalue of 14%, and has a typical thickness of a few kpc, incompatible withexpectations based on hydrostatic equilibrium models. The EPG kinematics isremarkably similar throughout the sample, and consists of a lagging rotationwith typical vertical gradients of about -10 km/s/kpc, a velocity dispersion of15-30 km/s and, for most galaxies, a global inflow in both the vertical andradial directions with speeds of 20-30 km/s. The EPG HI masses are in excellentagreement with predictions from simple models of the galactic fountain poweredby stellar feedback. The combined effect of photo-ionisation and interaction ofthe fountain material with the circumgalactic medium can qualitatively explainthe kinematics of the EPG, but dynamical models of the galactic fountain arerequired to fully test this framework.

1909.06712 A measurement of the Hubble constant from angular diameter distances to two gravitational lenses

Inh Jee, Sherry Suyu, Eiichiro Komatsu, Christopher D. Fassnacht, Stefan Hilbert, Léon V. E. Koopmans

Published 2019-09-15, This paper presents the measurements of angular diameter distances to two time-delay lenses, and the Hubble constant derived only from these two distances and the JLA supernova sample. One of the distance measurements is further used for the cosmological inference in the H0LiCOW XIII paper (arxiv:1907.04869). Published in Science

The local expansion rate of the Universe is parametrized by the Hubbleconstant, $H_0$, the ratio between recession velocity and distance. Differenttechniques lead to inconsistent estimates of $H_0$. Observations of Type Iasupernovae (SNe) can be used to measure $H_0$, but this requires an externalcalibrator to convert relative distances to absolute ones. We use the angulardiameter distance to strong gravitational lenses as a suitable calibrator,which is only weakly sensitive to cosmological assumptions. We determine theangular diameter distances to two gravitational lenses, $810^{+160}_{-130}$ and$1230^{+180}_{-150}$~Mpc, at redshifts of $z=0.295$ and $0.6304$. Using theseabsolute distances to calibrate 740 previously-measured relative distances toSNe, we measure the Hubble constant to be $H_0=82.4^{+8.4}_{-8.3} ~{\rmkm\,s^{-1}\,Mpc^{-1}}$.