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ABSTRACT Galaxy clusters grow primarily through the continuous accretion of group-scale haloes. Group galaxies experience preprocessing during their journey into clusters. A star-bursting compact group, the Blue Infalling Group (BIG), is plunging into the nearby cluster A1367. Previous optical observations reveal rich tidal features in the BIG members, and a long H α trail behind. Here, we report the discovery of a projected ∼250 kpc X-ray tail behind the BIG using Chandra and XMM–Newton observations. The total hot gas mass in the tail is ∼7 × 1010 M⊙ with an X-ray bolometric luminosity of ∼3.8 × 1041 erg s−1. The temperature along the tail is ∼1 keV, but the apparent metallicity is very low, an indication of the multi-T nature of the gas. The X-ray and H α surface brightnesses in the front part of the BIG tail follow the tight correlation established from a sample of stripped tails in nearby clusters, which suggests the multiphase gas originates from the mixing of the stripped interstellar medium (ISM) with the hot intracluster medium (ICM). Because thermal conduction and hydrodynamic instabilities are significantly suppressed, the stripped ISM can be long lived and produce ICM clumps. The BIG provides us a rare laboratory to study galaxy transformation and preprocessing. 

Metal-insulator-semiconductor (MIS) structures are widely used in Si-based solar water-splitting photoelectrodes to protect the Si layer from corrosion. Typically, there is a tradeoff between efficiency and stability when optimizing insulator thickness. Moreover, lithographic patterning is often required for fabricating MIS photoelectrodes. In this study, we demonstrate improved Si-based MIS photoanodes with thick insulating layers fabricated using thin-film reactions to create localized conduction paths through the insulator and electrodeposition to form metal catalyst islands. These fabrication approaches are low-cost and highly scalable, and yield MIS photoanodes with low onset potential, high saturation current density, and excellent stability. By combining this approach with a p⁺n-Si buried junction, further improved oxygen evolution reaction (OER) performance is achieved with an onset potential of 0.7 V versus reversible hydrogen electrode (RHE) and saturation current density of 32 mA/cm²under simulated AM1.5G illumination. Moreover, in stability testing in 1 M KOH aqueous solution, a constant photocurrent density of ~22 mA/cm²is maintained at 1.3 V versus RHE for 7 days.

 

Abell 407 (A407) is a unique galaxy cluster hosting a central compact group of nine galaxies (named as ‘Zwicky’s Nonet’; G1–G9 in this work) within a 30 kpc radius region. The cluster core also hosts a luminous radio active galactic nucleus (AGN), 4C 35.06 with helically twisted jets extending over 200 kpc. With a 44 ks Chandra observation of A407, we characterize the X-ray properties of its intracluster medium and central galaxies. The mean X-ray temperature of A407 is 2.7 keV and the M200 is $1.9 \times 10^{14}\, {\mathrm{M}_{\odot }}$. We suggest that A407 has a weak cool core at r < 60 kpc scales and at its very centre, <1–2 kpc radius, a small galaxy corona associated with the strong radio AGN. We also conclude that the AGN 4C 35.06 host galaxy is most likely G3. We suggest that the central group of galaxies is undergoing a ‘slow merge’ procedure. The range of the merging time-scale is 0.3 ∼ 2.3 Gyr and the stellar mass of the future brightest cluster galaxy (BCG) will be $7.4\times 10^{11} \, \mathrm{M}_{\odot }$. We find that the regions that overlap with the radio jets have higher temperature and metallicity. This is consistent with AGN feedback activity. The central entropy is higher than that for other clusters, which may be due to the AGN feedback and/or merging activity. With all these facts, we suggest that A407 is a unique and rare system in the local universe that could help us to understand the formation of a massive BCG.

 

Wafer-scale synthesis of p-type TMD films is critical for its commercialization in next-generation electro/optoelectronics. In this work, wafer-scale intrinsic n-type WS₂films and in situ Nb-doped p-type WS₂films were synthesized through atomic layer deposition (ALD) on 8-inchα-Al₂O₃/Si wafers, 2-inch sapphire, and 1 cm²GaN substrate pieces. The Nb doping concentration was precisely controlled by altering cycle number of Nb precursor and activated by postannealing. WS₂n-FETs and Nb-doped p-FETs with different Nb concentrations have been fabricated using CMOS-compatible processes. X-ray photoelectron spectroscopy, Raman spectroscopy, and Hall measurements confirmed the effective substitutional doping with Nb. The on/off ratio and electron mobility of WS₂n-FET are as high as 10⁵and 6.85 cm² V^-1 s^-1, respectively. In WS₂p-FET with 15-cycle Nb doping, the on/off ratio and hole mobility are 10 and 0.016 cm² V^-1 s^-1, respectively. The p-n structure based on n- and p- type WS₂films was proved with a 10⁴rectifying ratio. The realization of controllablein situNb-doped WS₂films paved a way for fabricating wafer-scale complementary WS₂FETs.

 

Electrodeposition of Si films from a Si‐containing electrolyte is a cost‐effective approach for the manufacturing of solar cells. Proposals relying on fluoride‐based molten salts have suffered from low product quality due to difficulties in impurity control. Here we demonstrate the successful electrodeposition of high‐quality Si films from a CaCl₂‐based molten salt. Soluble Si^IV−O anions generated from solid SiO₂are electrodeposited onto a graphite substrate to form a dense film of crystalline Si. Impurities in the deposited Si film are controlled at low concentrations (both B and P are less than 1 ppm). In the photoelectrochemical measurements, the film shows p‐type semiconductor character and large photocurrent. A p–n junction fabricated from the deposited Si film exhibits clear photovoltaic effects. This study represents the first step to the ultimate goal of developing a cost‐effective manufacturing process for Si solar cells based on electrodeposition.