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<jats:title>Abstract</jats:title> <jats:p>We present a sample of Ly<jats:italic>α</jats:italic> emitters (LAEs) at <jats:italic>z</jats:italic> ≈ 6.6 from our spectroscopic survey of high-redshift galaxies using the multi-object spectrograph M2FS on the Magellan Clay telescope. The sample consists of 36 LAEs selected by the narrowband (NB921) technique over nearly 2 deg<jats:sup>2</jats:sup> in the sky. These galaxies generally have high Ly<jats:italic>α</jats:italic> luminosities spanning a range of ∼3 × 10<jats:sup>42</jats:sup>–7 × 10<jats:sup>43</jats:sup> erg s<jats:sup>−1</jats:sup>, and include some of the most Ly<jats:italic>α</jats:italic>-luminous galaxies known at this redshift. They show a positive correlation between the Ly<jats:italic>α</jats:italic> line width and Ly<jats:italic>α</jats:italic> luminosity, similar to the relation previously found in <jats:italic>z</jats:italic> ≈ 5.7 LAEs. Based on the spectroscopic sample, we calculate a sophisticated sample completeness correction and derive the Ly<jats:italic>α</jats:italic> luminosity function (LF) at <jats:italic>z</jats:italic> ≈ 6.6. We detect a density bump at the bright end of the Ly<jats:italic>α</jats:italic> LF that is significantly above the best-fit Schechter function, suggesting that very luminous galaxies tend to reside in overdense regions that have formed large ionized bubbles around them. By comparing with the <jats:italic>z</jats:italic> ≈ 5.7 Ly<jats:italic>α</jats:italic> LF, we confirm that there is a rapid LF evolution at the faint end, but a lack of evolution at the bright end. The fraction of the neutral hydrogen in the intergalactic medium at <jats:italic>z</jats:italic> ≈ 6.6 estimated from such an evolution is about 0.3 ± 0.1, supporting a rapid and rather late process of cosmic reionization.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Gravitational-wave (GW) astrophysics is a rapidly expanding field, with plans to enhance the global ground-based observatory network through the addition of larger, more sensitive observatories: the Einstein Telescope and Cosmic Explorer. These observatories will allow us to peer deeper into the sky, collecting GW events from farther away and earlier in the universe. Within our own Galaxy, there is a plethora of interesting GW sources, including core-collapse supernovae, phenomena in isolated neutron stars and pulsars, and potentially novel sources. As GW observatories are directionally sensitive, their placement on the globe will affect the observation of Galactic sources. We analyze the performance of one-, two-, and three-observatory networks, both for sources at the Galactic center, as well as for a source population distributed over the Galactic disk. We find that, for a single Cosmic Explorer or Einstein Telescope observatory, placement at near-equatorial latitudes provides the most reliable observation of the Galactic center. When a source population distributed over the Galactic disk is considered, the observatory location is less impactful, although equatorial observatories still confer an advantage over observatories at more extreme latitudes. For two- and three-node networks, the longitudes of the observatories additionally become important for consistent observation of the Galaxy.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Nancy Grace Roman Space Telescope will conduct a High Latitude Spectroscopic Survey (HLSS) over a large volume at high redshift, using the near-IR grism (1.0–1.93 <jats:italic>μ</jats:italic>m, <jats:italic>R</jats:italic> = 435–865) and the 0.28 deg<jats:sup>2</jats:sup> wide-field camera. We present a reference HLSS that maps 2000 deg<jats:sup>2</jats:sup> and achieves an emission-line flux limit of 10<jats:sup>−16</jats:sup> erg s<jats:sup>−1</jats:sup> cm<jats:sup>−2</jats:sup> at 6.5<jats:italic>σ</jats:italic>, requiring ∼0.6 yr of observing time. We summarize the flowdown of the Roman science objectives to the science and technical requirements of the HLSS. We construct a mock redshift survey over the full HLSS volume by applying a semianalytic galaxy formation model to a cosmological <jats:italic>N</jats:italic>-body simulation and use this mock survey to create pixel-level simulations of 4 deg<jats:sup>2</jats:sup> of HLSS grism spectroscopy. We find that the reference HLSS would measure ∼10 million H<jats:italic>α</jats:italic> galaxy redshifts that densely map large-scale structure at <jats:italic>z</jats:italic> = 1–2 and 2 million [O <jats:sc>iii</jats:sc>] galaxy redshifts that sparsely map structures at <jats:italic>z</jats:italic> = 2–3. We forecast the performance of this survey for measurements of the cosmic expansion history with baryon acoustic oscillations and the growth of large-scale structure with redshift-space distortions. We also study possible deviations from the reference design and find that a deep HLSS at <jats:italic>f</jats:italic> <jats:sub>line</jats:sub> &gt; 7 × 10<jats:sup>−17</jats:sup> erg s<jats:sup>−1</jats:sup> cm<jats:sup>−2</jats:sup> over 4000 deg<jats:sup>2</jats:sup> (requiring ∼1.5 yr of observing time) provides the most compelling stand-alone constraints on dark energy from Roman alone. This provides a useful reference for future optimizations. The reference survey, simulated data sets, and forecasts presented here will inform community decisions on the final scope and design of the Roman HLSS.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Coronal loops, seen in solar coronal images, are believed to represent emission from magnetic flux tubes with compact cross sections. We examine the 3D structure of plasma above an active region in a radiative magnetohydrodynamic simulation to locate volume counterparts for coronal loops. In many cases, a loop cannot be linked to an individual thin strand in the volume. While many thin loops are present in the synthetic images, the bright structures in the volume are fewer and of complex shape. We demonstrate that this complexity can form impressions of thin bright loops, even in the absence of thin bright plasma strands. We demonstrate the difficulty of discerning from observations whether a particular loop corresponds to a strand in the volume, or a projection artifact. We demonstrate how apparently isolated loops could deceive observers, even when observations from multiple viewing angles are available. While we base our analysis on a simulation, the main findings are independent from a particular simulation setup and illustrate the intrinsic complexity involved in interpreting observations resulting from line-of-sight integration in an optically thin plasma. We propose alternative interpretation for strands seen in Extreme Ultraviolet images of the corona. The “coronal veil” hypothesis is mathematically more generic, and naturally explains properties of loops that are difficult to address otherwise—such as their constant cross section and anomalously high density scale height. We challenge the paradigm of coronal loops as thin magnetic flux tubes, offering new understanding of solar corona, and by extension, of other magnetically confined bright hot plasmas.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report the robust detection of coherent, localized deviations from Keplerian rotation possibly associated with the presence of two giant planets embedded in the disk around HD 163296. The analysis is performed using the <jats:sc>discminer</jats:sc> channel map modeling framework on <jats:sup>12</jats:sup>CO <jats:italic>J</jats:italic> = 2–1 DSHARP data. Not only orbital radius but also azimuth of the planets are retrieved by our technique. One of the candidate planets, detected at <jats:italic>R</jats:italic> = 94 ± 6 au, <jats:italic>ϕ</jats:italic> = 50° ± 3° (P94), is near the center of one of the gaps in dust continuum emission and is consistent with a planet mass of 1 <jats:italic>M</jats:italic> <jats:sub>Jup</jats:sub>. The other planet, located at <jats:italic>R</jats:italic> = 261 ± 4 au, <jats:italic>ϕ</jats:italic> = 57° ± 1° (P261), is in the region where a velocity kink was previously observed in <jats:sup>12</jats:sup>CO channel maps. Also, we provide a simultaneous description of the height and temperature of the upper and lower emitting surfaces of the disk and propose the line width as a solid observable to track gas substructure. Using azimuthally averaged line width profiles, we detect gas gaps at <jats:italic>R</jats:italic> = 38, 88, and 136 au, closely matching the location of their dust and kinematical counterparts. Furthermore, we observe strong azimuthal asymmetries in line widths around the gas gap at <jats:italic>R</jats:italic> = 88 au, possibly linked to turbulent motions driven by the P94 planet. Our results confirm that the <jats:sc>discminer</jats:sc> is capable of finding localized, otherwise unseen velocity perturbations thanks to its robust statistical framework, but also that it is well suited for studies of the gas properties and vertical structure of protoplanetary disks.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We consider a magnetar flare model for fast radio bursts (FRBs). We show that millisecond bursts of sufficient power can be generated by synchrotron maser emission ignited at the reverse shock propagating through the weakly magnetized material that forms the magnetar flare. If the maser emission is generated in an anisotropic regime (due to the geometry of the production region or presence of an intense external source of stimulating photons), the duration of the maser flashes is similar to the magnetar flare duration even if the shock front radius is large. Our scenario allows for relaxing the requirements for several key parameters: the magnetic field strength at the production site, luminosity of the flare, and the production site bulk Lorentz factor. To check the feasibility of this model, we study the statistical relation between powerful magnetar flares and the rate of FRBs. The expected ratio is derived by convoluting the redshift-dependent magnetar density with its flare luminosity function above the energy limit determined by the FRB detection threshold. We obtain that only a small fraction, ∼10<jats:sup>−5</jats:sup>, of powerful magnetar flares trigger FRBs. This ratio agrees surprisingly well with our estimates: we obtained that 10% of magnetars should be in the evolutionary phase suitable for the production of FRBs, and only 10<jats:sup>−4</jats:sup> of all flares are expected to be weakly magnetized, which is a necessary condition for the high-frequency maser emission.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The majority of studies on multi-scale vortex motions employ a two-dimensional geometry by using a variety of observational and numerical data. This approach limits the understanding the nature of physical processes responsible for vortex dynamics. Here, we develop a new methodology to extract essential information from the boundary surface of vortex tubes. 3D high-resolution magneto-convection MURaM numerical data has been used to analyze photospheric intergranular velocity vortices. The Lagrangian averaged vorticity deviation technique was applied to define the centers of vortex structures and their boundary surfaces based on the advection of fluid elements. These surfaces were mapped onto a constructed envelope grid that allows the study of the key plasma parameters as functions of space and time. Quantities that help in understanding the dynamics of the plasma, e.g., Lorentz force, pressure force, and plasma-<jats:italic>β</jats:italic> were also determined. Our results suggest that, while density and pressure have a rather global behavior, the other physical quantities undergo local changes, with their magnitude and orientation changing in space and time. At the surface, the mixing in the horizontal direction is not efficient, leading to appearance of localized regions with higher/colder temperatures. In addition, the analysis of the MHD Poynting flux confirms that the majority of the energy is directed in the horizontal direction. Our findings also indicate that the pressure and magnetic forces that drive the dynamics of the plasma on vortex surfaces are unbalanced and therefore the vortices do not rotate as a rigid body.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present results of a multiwavelength analysis of SDSS J025214.67−002813.7, a system that has been previously classified as a binary active galactic nucleus (AGN) candidate based on periodic signals detected in the optical light curves. We use available radio−X-ray observations of the system to investigate the true accretion nature. Analyzing new observations from XMM-Newton and NuSTAR, we characterize the X-ray emission and search for evidence of circumbinary accretion. Although the 0.5–10 keV spectrum shows evidence of an additional soft emission component, possibly due to extended emission from hot nuclear gas, we find the spectral shape is consistent with that of a single AGN. Compiling a full multiwavelength spectral energy distribution (SED), we also search for signs of circumbinary accretion, such as a “notch” in the continuum due to the presence of minidisks. We find that the radio–optical emission agrees with the SED of a standard, radio-quiet, AGN; however, there is a large deficit in emission blueward of ∼1400 Å. Although this deficit in emission can plausibly be attributed to a binary AGN system, we find that the SED of SDSS J0252−0028 is better explained by emission from a reddened, single AGN. However, future studies of the expected hard X-ray emission associated with binary AGNs (especially in the unequal-mass regime) will allow for more rigorous analyses of the binary AGN hypothesis.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a model-independent method of reconstructing scale factor against lookback time from the Observational Hubble parameter Data (OHD). The reconstruction method is independent of dynamical models and is only based on the Friedmann–Robertson–Walker metric. We also calculate the propagation of error in the reconstruction process. The reconstruction data errors mainly come from trapezoidal rule approximation and the uncertainty from OHD. Furthermore, the model discrimination ability of original OHD and reconstructed <jats:italic>a</jats:italic>–<jats:italic>t</jats:italic> data is discussed under a dimensionless standard method. The <jats:italic>a</jats:italic>–<jats:italic>t</jats:italic> data can present the differences between cosmology models more clearly than <jats:italic>H</jats:italic>–<jats:italic>z</jats:italic> data by comparing their coefficients of variations. Finally, we add 50 simulated <jats:italic>H</jats:italic>(<jats:italic>z</jats:italic>) data to estimate the influence of future observation. More Hubble measurements in the future will help constrain cosmological parameters more accurately.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report the discoveries of a nuclear ring of diameter 10″ (∼1.5 kpc) and a potential low-luminosity active galactic nucleus (LLAGN) in the radio continuum emission map of the edge-on barred spiral galaxy NGC 5792. These discoveries are based on the Continuum Halos in Nearby Galaxies—an Expanded Very Large Array (VLA) Survey, as well as subsequent VLA observations of subarcsecond resolution. Using a mixture of H<jats:italic>α</jats:italic> and 24 <jats:italic>μ</jats:italic>m calibrations, we disentangle the thermal and nonthermal radio emission of the nuclear region and derive a star formation rate (SFR) of ∼0.4 <jats:italic>M</jats:italic> <jats:sub>☉</jats:sub> yr<jats:sup>−1</jats:sup>. We find that the nuclear ring is dominated by nonthermal synchrotron emission. The synchrotron-based SFR is about three times the mixture-based SFR. This result indicates that the nuclear ring underwent more intense star-forming activity in the past, and now its star formation is in the low state. The subarcsecond VLA images resolve six individual knots on the nuclear ring. The equipartition magnetic field strength <jats:italic>B</jats:italic> <jats:sub>eq</jats:sub> of the knots varies from 77 to 88 <jats:italic>μ</jats:italic>G. The radio ring surrounds a point-like faint radio core of <jats:italic>S</jats:italic> <jats:sub>6 GHz</jats:sub> = (16 ± 4) <jats:italic>μ</jats:italic>Jy with polarized lobes at the center of NGC 5792, which suggests an LLAGN with an Eddington ratio of ∼10<jats:sup>−5</jats:sup>. This radio nuclear ring is reminiscent of the Central Molecular Zone of the Galaxy. Both of them consist of a nuclear ring and LLAGN.</jats:p>