Metal-enriched, subkiloparsec gas clumps in the circumgalactic medium of a faint z = 2.5 galaxy

We report the serendipitous detection of a 0.2 L*, Lyα emitting galaxy at redshift 2.5 at an impact parameter of 50 kpc from a bright background QSO sightline. A high-resolution spectrum of the QSO reveals a partial Lyman-limit absorption system (NHi=1016.94±0.10 cm−2) with many associated metal absorption lines at the same redshift as the foreground galaxy. Using photoionization models that carefully treat measurement errors and marginalize over uncertainties in the shape and normalization of the ionizing radiation spectrum, we derive the total hydrogen column density NH=1019.4±0.3cm−2, and show that all the absorbing clouds are metal enriched, with Z = 0.1–0.6 Z⊙. These metallicities and the system's large velocity width (436 km s− 1) suggest the gas is produced by an outflowing wind. Using an expanding shell model we estimate a mass outflow rate of ∼5 M⊙ yr−1. Our photoionization model yields extremely small sizes (<100–500 pc) for the absorbing clouds, which we argue is typical of high column density absorbers in the circumgalactic medium (CGM). Given these small sizes and extreme kinematics, it is unclear how the clumps survive in the CGM without being destroyed by hydrodynamic instabilities. The small cloud sizes imply that even state-of-the-art cosmological simulations require more than a 1000-fold improvement in mass resolution to resolve the hydrodynamics relevant for cool gas in the CGM

Clustering of galaxies around quasars at z~4

Large scale structure and cosmolog

Improving IGM temperature constraints using wavelet analysis on high-redshift quasars

Large scale structure and cosmolog

Paving the way for Euclid and JWST via probabilistic selection of high-redshift quasars

Galaxie

ALMA reveals a large overdensity and strong clustering of galaxies in quasar environments at z ~ 4

Galaxie

Dynamic Evolution of a Quasi-Spherical General Polytropic Magnetofluid with Self-Gravity

In various astrophysical contexts, we analyze self-similar behaviours of magnetohydrodynamic (MHD) evolution of a quasi-spherical polytropic magnetized gas under self-gravity with the specific entropy conserved along streamlines. In particular, this MHD model analysis frees the scaling parameter $n$ in the conventional polytropic self-similar transformation from the constraint of $n+\gamma=2$ with $\gamma$ being the polytropic index and therefore substantially generalizes earlier analysis results on polytropic gas dynamics that has a constant specific entropy everywhere in space at all time. On the basis of the self-similar nonlinear MHD ordinary differential equations, we examine behaviours of the magnetosonic critical curves, the MHD shock conditions, and various asymptotic solutions. We then construct global semi-complete self-similar MHD solutions using a combination of analytical and numerical means and indicate plausible astrophysical applications of these magnetized flow solutions with or without MHD shocks.Comment: 21 pages, 7 figures, accepted for publication in APS

A multiwavelength study of ELAN environments (AMUSE^2). Mass budget, satellites spin alignment, and gas infall in a massive z ~ 3 quasar host halo

Galaxie

Weak lensing, dark matter and dark energy

Weak gravitational lensing is rapidly becoming one of the principal probes of dark matter and dark energy in the universe. In this brief review we outline how weak lensing helps determine the structure of dark matter halos, measure the expansion rate of the universe, and distinguish between modified gravity and dark energy explanations for the acceleration of the universe. We also discuss requirements on the control of systematic errors so that the systematics do not appreciably degrade the power of weak lensing as a cosmological probe.Comment: Invited review article for the GRG special issue on gravitational lensing (P. Jetzer, Y. Mellier and V. Perlick Eds.). V3: subsection on three-point function and some references added. Matches the published versio

Probing early supermassive black hole growth and quasar evolution with near-infrared spectroscopy of 37 reionization-era quasars at 6.3 < z < 7.64

Galaxie

Discovery of 24 radio-bright quasars at 4.9 <= z <= 6.6 using low-frequency radio observations

Galaxie