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We study the projected spatial offset between the ultraviolet continuum and Ly α emission for 65 lensed and unlensed galaxies in the Epoch of Reionization (5 ≤ z ≤ 7), the first such study at these redshifts, in order to understand the potential for these offsets to confuse estimates of the Ly α properties of galaxies observed in slit spectroscopy. While we find that ∼40 per cent of galaxies in our sample show significant projected spatial offsets ($|\Delta {\rm {Ly}\alpha -\rm {UV}}|$), we find a relatively modest average projected offset of $|\widetilde{\Delta }{\rm {Ly}\alpha -\rm {UV}}|$ = 0.61 ± 0.08 proper kpc for the entire sample. A small fraction of our sample, ∼10 per cent, exhibit offsets in excess of 2 proper kpc, with offsets seen up to ∼4 proper kpc, sizes that are considerably larger than the effective radii of typical galaxies at these redshifts. An internal comparison and a comparison to studies at lower redshift yielded no significant evidence of evolution of $|\Delta {\rm {Ly}\alpha -\rm {UV}}|$ with redshift. In our sample, ultraviolet (UV)-bright galaxies ($\widetilde{L{\mathrm{ UV}}}/L{\ast }{\mathrm{ UV}}=0.67$) showed offsets a factor of three greater than their fainter counterparts ($\widetilde{L{\mathrm{ UV}}}/L{\ast }{\mathrm{ UV}}=0.10$), 0.89 ± 0.18 versus 0.27 ± 0.05 proper kpc, respectively. The presence of companion galaxies and early stage merging activity appeared to be unlikely causes of these offsets. Rather, these offsets appear consistent with a scenario in which internal anisotropic processes resulting from stellar feedback, which is stronger in UV-brighter galaxies, facilitate Ly α fluorescence and/or backscattering from nearby or outflowing gas. The reduction in the Ly α flux due to offsets was quantified. It was found that the differential loss of Ly α photons for galaxies with average offsets is not, if corrected for, a limiting factor for all but the narrowest slit widths (

We present a new mass function of galaxy clusters and groups using optical/near-infrared (NIR) wavelength spectroscopic and photometric data from the Observations of Redshift Evolution in Large-Scale Environments (ORELSE) survey. At z ∼ 1, cluster mass function studies are rare regardless of wavelength and have never been attempted from an optical/NIR perspective. This work serves as a proof of concept that z ∼ 1 cluster mass functions are achievable without supplemental X-ray or Sunyaev-Zel’dovich data. Measurements of the cluster mass function provide important contraints on cosmological parameters and are complementary to other probes. With ORELSE, a new cluster finding technique based on Voronoi tessellation Monte Carlo (VMC) mapping, and rigorous purity and completeness testing, we have obtained ∼240 galaxy overdensity candidates in the redshift range 0.55 < z < 1.37 at a mass range of 13.6 < log (M/M⊙) < 14.8. This mass range is comparable to existing optical cluster mass function studies for the local universe. Our candidate numbers vary based on the choice of multiple input parameters related to detection and characterization in our cluster finding algorithm, which we incorporated into the mass function analysis through a Monte Carlo scheme. We find cosmological constraints on the matter density, Ω_m, and the amplitude of fluctuations, σ₈, of Ω_m = 0.250−0.099+0.104 and σ₈ = 1.150−0.163+0.260⁠. While our Ω_m value is close to concordance, our σ₈ value is ∼2σ higher because of the inflated observed number densities compared to theoretical mass function models owing to how our survey targeted overdense regions. With Euclid and several other large, unbiased optical surveys on the horizon, VMC mapping will enable optical/NIR cluster cosmology at redshifts much higher than what has been possible before.

We present ALMA observations of a merging system at z ~ 4.57, observed as a part of the ALMA Large Program to INvestigate [CII] at Early times (ALPINE) survey. Combining ALMA [CII] 158 micron and far-infrared continuum data with multi-wavelength ancillary data we find that the system is composed of two massive (Mstar >~ 10^10 Msun) star-forming galaxies experiencing a major merger (stellar mass ratio r_mass ~ 0.9) at close spatial (~13 kpc; projected) and velocity (delta_v < 300 km/s) separations, and two additional faint narrow [CII]-emitting satellites. The overall system belongs to a larger-scale protocluster environment and is coincident to one of its overdensity peaks. ALMA reveals also the presence of [CII] emission arising from a circumgalactic gas structure, extending up to a diameter-scale of ~30 kpc. Our morpho-spectral decomposition analysis shows that about 50% of the total flux resides between the individual galaxy components, in a metal-enriched gaseous envelope characterized by a disturbed morphology and complex kinematics. Similarly to observations of shock-excited [CII] emitted from tidal tails in local groups, our results can be interpreted as a possible signature of interstellar gas stripped by strong gravitational interactions, with a possible contribution from material ejected by galactic outflows and emission triggered by star formation in small faint satellites. Our findings suggest that mergers could be an efficient mechanism of gas mixing in the circumgalactic medium around high-z galaxies, and thus play a key role in the galaxy baryon cycle at early epochs., 12 pages, 7 figures. Accepted for publication in A&A

The quest for imaging protocols with ever-reduced dose is one of the most powerful motivators driving the currently exploding field of ghost imaging (GI). Ghost tomography (GT) using single-pixel detection extends the burgeoning field of GI to 3D, with the use of penetrating radiation. For hard x-rays, GT has the potential to relax the constraints that dose rate and detector performance impose on image quality and resolution. In this work, spatially random x-ray intensity patterns illuminate a specimen from various view-angles; in each case, the total transmitted intensity is recorded by a single-pixel (or bucket) detector. These readings, combined with knowledge of the corresponding 2D illuminating patterns and specimen orientations, are sufficient for 3D specimen reconstruction. The experimental demonstration of GT is presented here using synchrotron hard x-rays. This result significantly expands the scope of GI to encompass volumetric imaging (i.e., tomography), of optically opaque objects using penetrating radiation.

International audience; Microbeam radiation therapy (MRT) is a preclinical treatment under development on the Imaging and Medical Beamline (IMBL), Australian Synchrotron. It uses spatially fractionated x-ray microbeams with a width of 50 μm and 400 μm pitch. The x-ray beam, which has a mean energy of approximately 100 keV in the treatment enclosure, is generated by a wiggler source and collimated by a tungsten multislit collimator. Preclinical studies on other synchrotron beamlines have previously demonstrated preferential tumour damage and sparing of surrounding normal tissue [1-3]. A synchrotron source is necessary to produce the high dose rates, high dose gradients and minimal beam divergence required for MRT to maintain a highly collimated, spatially fractionated array of microbeams. The ratio between the dose in the microbeams and the dose between the microbeams, known as the peak-tovalley dose ratio (PVDR) is thought to be of therapeutic importance, with the valley dose believed to be a primary factor influencing the normal tissue tolerance [3]. It is thus important to be able to perform absolute dosimetry and accurately measure the PVDR.Dosimetry for MRT is challenging due to the inherent beam properties of MRT. Small field sizes and large dose gradients can produce large uncertainties caused largely by the partial volume effect. Additionally, a number of dosimeters exhibit energy dependence for keV x-rays and ionrecombination effects at high dose rates. The PTW microDiamond detector has been identified as a potential MRT dosimeter due to its small 2.2 mm × 1 μm cylindrical sensitive volume. The purpose of the study was to characterise the microDiamond detector in broadbeam and microbeams to determine its suitability for MRT dosimetry. The energy dependence has been investigated and characterised and the dose rate dependence was found to be minimal over the dose range 1—600 Gy. Preliminary measurements of microbeam profiles and PVDR were also promising. Measurements will be repeated using the recently commissioned dedicated MRT system to optimise the procedure with a view towards developing an absolute dosimetry protocol. Results will be discussed in the presentation.References[1] – J. A. Laissue, et al., Int. J. Cancer, 78, 654—660 (1998).[2] – A. Bouchet, et al., Int, J. Radiat. Oncol.Biol. Phys.78, 1503—1512 (2010).[3] – R. Serduc, et al. Phys. Med. Biol., 53, 3609—3622 (2008).

We report on the experimental realization of propagation-based x-ray microscopy with laboratory sources equipped with waveguides. We discuss about the experimental setup, the fabrication steps, and the characterization procedures of the waveguide optics. We demonstrate that the system enables high resolution attenuation imaging of poorly absorbing biological specimens. Furthermore, we report the successful realization of propagation-based phase contrast x-ray microscopy, enabling quantitative thickness estimation in homogeneous objects. Advantages and major limitations of the experimental scheme are presented and discussed.

We report the performance of an X-ray phase contrast microscope for laboratory sources with 300 nm spatial resolution. The microscope is based on a commercial X-ray microfocus source equipped with a planar X-ray waveguide able to produce a sub-micrometer x-ray beam in one dimension. Phase contrast images of representative samples are reported. The achieved contrast and resolution is discussed for different configurations. The proposed approach could represent a simple, inexpensive, solution for sub-micrometer resolution imaging with small laboratory setups. (C) 2010 Optical Society of America

In the hard x-ray region, the cross sections for the phase shift of low-Z elements are about 1000 times larger than the absorption ones. As a consequence, phase contrast is detectable even when absorption contrast is minimal or absent. Therefore, phase-contrast imaging could become a valid alternative to absorption contrast without delivering high dose to tissue/human body parts.To enhance the quality of phase-contrast images without increasing the dose, a possible approach could be the partial deconvolution of the finite source size effects by experimental phase-contrast images. The deconvolution procedure, the authors propose, employs the acquisition of two images on a suitable well-known test sample, one in contact and the other in phase-contrast conditions. Both acquired images are used along with a simulated phase-contrast image (obtained from the test sample in ideal conditions of pointlike source illumination) to correctly retrieve the experimental source distribution function. This information allows a generic experimental phase-contrast image, acquired in the same conditions, to be partially deconvolved by finite source size effects.The performed experimental tests indicate that deconvolved images are equivalent to those which would be obtained with a source 40% smaller than the actual size. In turn, this finding is equivalent to an increase of the "effective" lateral spatial coherence length. The corresponding quality improvement of the phase-contrast imaging is directly deducible by the presence of many Fresnel fringes, much better visible with respect to the original experimental phase-contrast images.The use of a test standard sample, always possible in every experimental setup, to partially deconvolve the finite-size-source blurring effects shows that higher quality phase-contrast images could be readily available, making easier diagnoses and tissue/sample analyses. The method could give, in the future, the possibility to further lower the delivered dose to patients, organs, and tissues when compact room-sized and brilliant microfocus x-ray sources will be available for clinical applications in hospitals.

A Fresnel coherent diffraction imaging experiment with hard x rays is here presented, using two planar crossed waveguides as optical elements, leading to a virtual pointlike source. The coherent wave field obtained with this setup is used to illuminate a micrometric single object having the shape of a butterfly. A digital two-dimensional in-line holographic reconstruction of the unknown object at low resolution 200 nm has been obtained directly via fast Fourier transform FFT of the raw data. The object and its twin image are well separated because suitable geometrical conditions are satisfied. A good estimate of the incident wave field phase has been extracted directly from the FFT of the raw data. A partial object reconstruction with 50 nm spatial resolution was achieved by fast iterative phase retrieval, the major limitation for a full reconstruction being the nonideal structure of the guided beam. The method offers a route for fast and reliable phase retrieval in x-ray coherent diffraction.