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1. A Chandra survey of z ≥ 4.5 quasars

   https://doi.org/10.1093/mnras/stab1042  

   Li, Jiang-Tao; Wang, Feige; Yang, Jinyi; Bregman, Joel N; Fan, Xiaohui; Zhang, Yuchen (May 2021, Monthly Notices of the Royal Astronomical Society)

   null (Ed.)

   ABSTRACT X-ray observations provide a unique probe of the accretion disc corona of supermassive black holes (SMBHs). In this paper, we present a uniform Chandra X-ray data analysis of a sample of 152 z ≥ 4.5 quasars. We firmly detect 46 quasars of this sample in 0.5–2 keV above 3σ and calculate the upper limits of the X-ray flux of the remaining. We also estimate the power-law photon index of the X-ray spectrum of 31 quasars. 24 of our sample quasars are detected in the FIRST or NVSS radio surveys; all of them are radio-loud. We statistically compare the X-ray properties of our z ≥ 4.5 quasars to other X-ray samples of active galactic nuclei (AGNs) at different redshifts. The relation between the rest-frame X-ray luminosity and other quasar parameters, such as the bolometric luminosity, UV luminosity, or SMBH mass, shows large scatters. These large scatters can be attributed to the narrow luminosity range at the highest redshift, the large measurement error based on relatively poor X-ray data, and the inclusion of radio-loud quasars in the sample. The LX–LUV relationship is significantly sublinear. We do not find a significant redshift evolution of the LX–LUV relation, expressed either in the slope of this relation, or the departure of individual AGNs from the best-fitting αOX–LUV relation (ΔαOX). The median value of the X-ray photon index is Γ ≈ 1.79, which does not show redshift evolution from z = 0 to z ∼ 7. The X-ray and UV properties of the most distant quasars could potentially be used as a standard candle to constrain cosmological models. The large scatter of our sample on the Hubble diagram highlights the importance of future large unbiased deep X-ray and radio surveys in using quasars in cosmological studies. 

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2. Stereoselective Synthesis of ( E )- and ( Z )-Isocyanoalkenes

   https://doi.org/10.1021/acs.orglett.2c03461  

   Tian, Huan; Holyoke, Caleb W.; Fleming, Fraser F. (December 2022, Organic Letters)
3. CHILES: H   i morphology and galaxy environment at z  = 0.12 and z  = 0.17

   https://doi.org/10.1093/mnras/sty3421  

   Hess, Kelley M; Luber, Nicholas M; Fernández, Ximena; Gim, Hansung B; van Gorkom, J H; Momjian, Emmanuel; Gross, Julia; Meyer, Martin; Popping, Attila; Davies, Luke J; et al (December 2018, Monthly Notices of the Royal Astronomical Society)
4. THE CYCLIC GRAPH OF A Z -GROUP

   https://doi.org/10.1017/S0004972720001318  

   COSTANZO, DAVID G.; LEWIS, MARK L.; SCHMIDT, STEFANO; TSEGAYE, EYOB; UDELL, GABE (January 2020, Bulletin of the Australian Mathematical Society)

   null (Ed.)

   Abstract: For a group G, we define a graph Delta (G) by letting G^#=G\{1} be the set of vertices and by drawing an edge between distinct elements x,y in G^# if and only if the subgroup is cyclic. Recall that a Z-group is a group where every Sylow subgroup is cyclic. In this short note, we investigate Delta (G) for a Z-group G. 

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5. The z –DM distribution of fast radio bursts

   https://doi.org/10.1093/mnras/stab3051  

   James, C W; Prochaska, J X; Macquart, J-P; North-Hickey, F O; Bannister, K W; Dunning, A (December 2021, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We develop a sophisticated model of fast radio burst (FRB) observations, accounting for the intrinsic cosmological gas distribution and host galaxy contributions, and give the most detailed account yet of observational biases due to burst width, dispersion measure, and the exact telescope beamshape. Our results offer a significant increase in both accuracy and precision beyond those previously obtained. Using results from ASKAP and Parkes, we present our best-fitting FRB population parameters in a companion paper. Here, we consider in detail the expected and fitted distributions in redshift, dispersion measure, and signal to noise. We estimate that the unlocalized ASKAP FRBs arise from z < 0.5, with between a third and a half within z < 0.1. Our predicted source-counts (‘logN–logS’) distribution confirms previous indications of a steepening index near the Parkes detection threshold of 1 Jy ms. We find no evidence for a minimum FRB energy, and rule out Emin > 1039.0 erg at 90 per cent C.L. Importantly, we find that above a certain DM, observational biases cause the Macquart (DM–z) relation to become inverted, implying that the highest-DM events detected in the unlocalized Parkes and ASKAP samples are unlikely to be the most distant. More localized FRBs will be required to quantitatively estimate this effect, though its cause is a well-understood observational bias. Works assuming a 1–1 DM–z relation may therefore derive erroneous results. Our analysis of errors suggests that limiting factors in our analysis are understanding of FRB spectral behaviour, sensitivity response of search experiments, and the treatment of the repeating population and luminosity function. 

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