Search

We present a tomographic analysis of metal absorption lines arising from the circumgalactic medium (CGM) of galaxies at z ≈ 0.5–2, using Multi Unit Spectroscopic Explorer (MUSE) observations of two background quasars at z ≈ 2.2 and 2.8, which are two of the few currently known quasars with multiple images due to strong gravitational lensing by galaxy clusters at z ≈ 0.6 and 0.5, respectively. The angular separations between different pairs of quasar multiple images enable us to probe the absorption over transverse physical separations of ≈0.4–150 kpc, which are based on strong lensing models exploiting MUSE observations. The fractional difference in rest-frame equivalent width (Δ W r) of Mg  ii , Fe  ii , and C  iv absorption increases on average with physical separation, indicating that the metal-enriched gaseous structures become less coherent with distance, with a likely coherence length-scale of ≈10 kpc. However, Δ W r for all the ions vary considerably over ≈0.08–0.9, indicating a clumpy CGM over the full range of length-scales probed. At the same time, paired Mg  ii absorption is detected across ≈100–150 kpc at similar line-of-sight velocities, which could be probing cool gas clouds within the same halo. No significant dependence of Δ W r is found on the equivalent width and redshift of the absorbing gas and on the galaxy environment associated with the absorption. The high-ionization gas phase traced by C  iv shows a higher degree of coherence than the low-ionization gas phase traced by Mg  ii , with ≈90 per cent of C  iv systems exhibiting Δ W r ≤ 0.5 at separations ≤10 kpc compared to ≈50 per cent of Mg  ii systems. [ABSTRACT FROM AUTHOR]

In this work, we analyze the mass distribution of MACSJ1206.2-0847, particularly focusing on the halo properties of its cluster members. The cluster appears relaxed in its X-ray emission, but has a significant amount of intracluster light that is not centrally concentrated, suggesting that galaxy-scale interactions are still ongoing despite the overall relaxed state. The cluster lenses 12 background galaxies into multiple images and one galaxy at z = 1.033 into a giant arc and its counterimage. The multiple image positions and the surface brightness (SFB) distribution of the arc, which is bent around several cluster members, are sensitive to the cluster galaxy halo properties. We model the cluster mass distribution with a Navarro-Frenk-White profile and the galaxy halos with two parameters for the mass normalization and the extent of a reference halo assuming scalings with their observed near-infrared light. We match the multiple image positions at an rms level of 0. ''85 and can reconstruct the SFB distribution of the arc in several filters to a remarkable accuracy based on this cluster model. The length scale where the enclosed galaxy halo mass is best constrained is about 5 effective radii-a scale in between those accessible to dynamical and field strong-lensing mass estimates on the one hand and galaxy-galaxy weak-lensing results on the other hand. The velocity dispersion and halo size of a galaxy with m160W,AB = 19.2 and MB,Vega = -20.7 are σ = 150 km s-1 and r ≈ 26±6 kpc, respectively, indicating that the halos of the cluster galaxies are tidally stripped.We also reconstruct the unlensed source, which is smaller by a factor of ~5.8 in area, demonstrating the increase in morphological information due to lensing. We conclude that this galaxy likely has star-forming spiral arms with a red (older) central component. [ABSTRACT FROM AUTHOR]

ABSTRACT Strong gravitational lensing magnifies the flux from distant galaxies, allowing us to detect emission lines that would otherwise fall below the detection threshold for medium-resolution spectroscopy. Here we present the detection of temperature-sensitive oxygen emission lines from three galaxies at 2 ≲ z ≲ 3.5, which enables us to directly determine the oxygen abundances and thereby double the number of galaxies at z > 2 for which this has been possible. The three galaxies have ∼10 per cent solar oxygen abundances in agreement with strong emission-line diagnostics. Carbon and nitrogen ratios relative to oxygen are subsolar as expected for young metal-poor galaxies. Two of the galaxies are Lyman α (Lyα) emitters with rest-frame equivalent widths of 20 and 40 Å, respectively, and their high magnification factors allow us for the first time to gain insight into the physical characteristics of high-redshift Lyα emitters. Using constraints from the physical properties of the galaxies, we accurately reproduce their line profiles with radiative transfer models. The models show a relatively small outflow in agreement with the observed small velocity offsets between nebular emission and interstellar absorption lines. [ABSTRACT FROM AUTHOR]

ABSTRACT We present Very Large Telescope/X-shooter spectra of 13 galaxies in the redshift range 1 ≲ z ≲ 6, which are strongly lensed by massive galaxy clusters. Spectroscopic redshifts are measured for nine galaxies, while three sources have redshifts determined from continuum breaks in their spectra. The stellar masses of the galaxies span four orders of magnitude between 107 and 1011 M⊙ and have luminosities at 1500 Å rest frame between 0.004 and 9 L* after correcting for the magnification. This allows us to probe a variety of galaxy types from young, low-mass starburst galaxies to massive evolved galaxies. The lensed galaxies with stellar masses less than 1010 M⊙ have a large scatter compared to the fundamental relation between stellar mass, star formation rates and oxygen abundances. We provide a modified fit to the fundamental relation for low-mass, low-metallicity galaxies with a weaker dependence of the metallicity on either the star formation rate or stellar mass compared to low-redshift, high-mass and high-metallicity Sloan Digital Sky Survey galaxies. [ABSTRACT FROM AUTHOR]

ABSTRACT We show the effectiveness of strong lensing in the characterization of Lyman continuum emission from faint L≲ 0.1 L* star-forming galaxies at redshift ≳3. Past observations of L≳ L* galaxies at redshift ≳3 have provided upper limits of the average escape fraction of ionizing radiation of fesc∼ 5 per cent. Galaxies with relatively high fesc (>10 per cent) seem to be particularly rare at these luminosities; there is therefore the need to explore fainter limits. Before the advent of giant ground-based telescopes, one viable way to probe fesc down to 0.05-0.15 L* was to exploit strong lensing magnification. This is investigated with Monte Carlo simulations that take into account the current observational capabilities. Adopting a lensing cross-section of 10 arcmin2 within which the magnification is higher than 1 (achievable with about four to five galaxy clusters), with a U-band survey depth of 30 (30.5) ( AB, 1σ), it is possible to constrain fesc for z≃ 3 star-forming galaxies down to 15 (10) per cent at 3σ for L < 0.15 L* luminosities. This is particularly interesting if fesc increases at fainter luminosities, as predicted from various H i reionization scenarios and radiation transfer modelling. Ongoing observational programmes on galaxy clusters are discussed and positive prospects for the future are offered, even though from space the Hubble Space Telescope ( HST)/Wide Field Camera 3 (WFC3) instrument represents the only option we have to investigate details of the spatial distribution of the Lyman continuum emission arising from z∼ 2-4 galaxies. [ABSTRACT FROM AUTHOR]