We present observations using the Atacama Large Millimeter/submillimeter Array of the CO(2−1), HCN(3−2), and HCO+(3−2) lines in the nearby radio galaxy/brightest cluster galaxy (BCG) NGC 1275 with a ...spatial resolution of ∼20 pc. In previous observations, the CO(2−1) emission was detected as radial filaments lying in the east-west direction on a kiloparsec scale. We resolved the inner filament and found that it cannot be represented by a simple infalling stream on a sub-kiloparsec scale. The observed complex nature of the filament resembles the cold gas structure predicted by numerical simulations of cold chaotic accretion. Within the central 100 pc, we detected a rotational disk of molecular gas whose mass is ∼108 M . This is the first evidence of the presence of a massive cold gas disk on this spatial scale for BCGs. A crude estimate suggests that the accretion rate of the cold gas can be higher than that of hot gas. The disk rotation axis is approximately consistent with the radio-jet axis. This probably suggests that the cold gas disk is physically connected to the innermost accretion disk, which is responsible for jet launching. We also detected absorption features in the HCN(3−2) and HCO+(3−2) spectra against the radio continuum emission mostly radiated by a jet of size ∼1.2 pc. The absorption features are blueshifted from the systemic velocity by ∼300-600 km s−1, suggesting the presence of outflowing gas from the active galactic nucleus (AGN). We discuss the relation of the AGN feeding with cold accretion, the origin of blueshifted absorption, and an estimate of the black hole mass using molecular gas dynamics.
Cosmological simulations predict that the Universe contains a network of intergalactic gas filaments, within which galaxies form and evolve. However, the faintness of any emission from these ...filaments has limited tests of this prediction. We report the detection of rest-frame ultraviolet Lyman-α radiation from multiple filaments extending more than one megaparsec between galaxies within the SSA22 protocluster at a redshift of 3.1. Intense star formation and supermassive black-hole activity is occurring within the galaxies embedded in these structures, which are the likely sources of the elevated ionizing radiation powering the observed Lyman-α emission. Our observations map the gas in filamentary structures of the type thought to fuel the growth of galaxies and black holes in massive protoclusters.
ABSTRACT We present full-polarization observations of the compact, steep-spectrum radio quasar 3C 286 made with the Atacama Large Millimeter and Submillimeter Array (ALMA) at 1.3 mm. These are the ...first full-polarization ALMA observations, which were obtained in the framework of Science Verification. A bright core and a south-west component are detected in the total intensity image, similar to previous centimeter images. Polarized emission is also detected toward both components. The fractional polarization of the core is about 17%; this is higher than the fractional polarization at centimeter wavelengths, suggesting that the magnetic field is even more ordered in the millimeter radio core than it is further downstream in the jet. The observed polarization position angle (or electric vector position angle (EVPA)) in the core is ∼39◦, which confirms the trend that the EVPA slowly increases from centimeter to millimeter wavelengths. With the aid of multi-frequency VLBI observations, we argue that this EVPA change is associated with the frequency-dependent core position. We also report a serendipitous detection of a sub-mJy source in the field of view, which is likely to be a submillimeter galaxy.
Context. Observations of chemical species can provide insights into the physical conditions of the emitting gas however it is important to understand how their abundances and excitation vary within ...different heating environments. C2H is a molecule typically found in PDR regions of our own Galaxy but there is evidence to suggest it also traces other regions undergoing energetic processing in extragalactic environments. Aims. As part of the ALCHEMI ALMA large program, we map the emission of C2H in the central molecular zone of the nearby starburst galaxy NGC 253 at 1.6″ (28 pc) resolution and characterize it to understand its chemical origins. Methods. We used spectral modeling of the N = 1−0 through N = 4−3 rotational transitions of C2H to derive the C2H column densities towards the dense clouds in NGC 253. We then use chemical modeling, including photodissociation region (PDR), dense cloud, and shock models to investigate the chemical processes and physical conditions that are producing the molecular emission. Results. We find high C2H column densities of ∼1015 cm−2 detected towards the dense regions of NGC 253. We further find that these column densities cannot be reproduced if it is assumed that the emission arises from the PDR regions at the edge of the clouds. Instead, we find that the C2H abundance remains high even in the high visual extinction interior of these clouds and that this is most likely caused by a high cosmic-ray ionization rate.
High-performance thermal insulating materials are desired especially from the viewpoint of saving energy for a sustainable society. Aerogel is the long-awaited material for extended applications due ...to its excellent thermal insulating ability. These materials are, however, seriously fragile against even small mechanical stress due to their low density, and their poor mechanical properties inhibit their practical use as superinsulators. In this paper, we report relationships between the thermal conductivity, pore size and mechanical properties of organic–inorganic hybrid polymethylsilsesquioxane (PMSQ) aerogels with improved mechanical properties and controllable pore sizes from ∼50 nm to 3 μm. The dependency of thermal conductivity on gas pressure and pore properties can be well explained by the thermal conduction theory of porous materials. These PMSQ aerogels show improved mechanical properties due to their elastic networks, which enable easier handling compared to conventional aerogels and facile production by simple ambient pressure drying. An aerogel-like “xerogel” monolithic panel has been successfully prepared via ambient pressure drying, which shows a low thermal conductivity (0.015 W m −1 K −1 ) comparable with those of the corresponding PMSQ aerogel and conventional silica aerogels. These results would open the gate for practical applications of these porous materials.
We extend the result in Nakanishi and Schlag (J Differ Equ 250:2299–2333,
2011
) on the nonlinear Klein–Gordon equation to the nonlinear Schrödinger equation with the focusing cubic nonlinearity in ...three dimensions, for radial data of energy at most slightly above that of the ground state. We prove that the initial data set splits into nine nonempty, pairwise disjoint regions which are characterized by the distinct behaviors of the solution for large time: blow-up, scattering to 0, or scattering to the family of ground states generated by the phase and scaling freedom. Solutions of this latter type form a smooth center-stable manifold, which contains the ground states and separates the phase space locally into two connected regions exhibiting blow-up and scattering to 0, respectively. The special solutions found by Duyckaerts and Roudenko (Rev Mater Iberoam 26(1):1–56,
2010
), following the seminal work on threshold solutions by Duyckaerts and Merle (Funct Anal 18(6):1787–1840,
2009
), appear here as the unique one-dimensional unstable/stable manifolds emanating from the ground states. In analogy with Nakanishi and Schlag (J Differ Equ 250:2299–2333,
2011
), the proof combines the hyperbolic dynamics near the ground states with the variational structure away from them. The main technical ingredient in the proof is a “one-pass” theorem which precludes “almost homoclinic orbits”, i.e., those solutions starting in, then moving away from, and finally returning to, a small neighborhood of the ground states. The main new difficulty compared with the Klein–Gordon case is the lack of finite propagation speed. We need the radial Sobolev inequality for the error estimate in the virial argument. Another major difference between Nakanishi and Schlag (J Differ Equ 250:2299–2333,
2011
) and this paper is the need to control two modulation parameters.
Transparent organic–inorganic hybrid aerogels and xerogels are prepared by using a sol–gel synthesis from a single trifunctional precursor, methyltrimethoxysilane (see figure). Obtained aerogels show ...a reversible shrinkage–recovery response against uniaxial compression. Aerogel‐like xerogels are successfully obtained by evaporation drying under ambient pressure because the gels recover from the temporal shrinkage caused by the capillary force of a drying solvent. Pore properties and nanotextures are well‐preserved in the resultant xerogels.
Galaxies in the early Universe that are bright at submillimetre wavelengths (submillimetre-bright galaxies) are forming stars at a rate roughly 1,000 times higher than the Milky Way. A large fraction ...of the new stars form in the central kiloparsec of the galaxy
, a region that is comparable in size to the massive, quiescent galaxies found at the peak of cosmic star-formation history
and the cores of present-day giant elliptical galaxies. The physical and kinematic properties inside these compact starburst cores are poorly understood because probing them at relevant spatial scales requires extremely high angular resolution. Here we report observations with a linear resolution of 550 parsecs of gas and dust in an unlensed, submillimetre-bright galaxy at a redshift of z = 4.3, when the Universe was less than two billion years old. We resolve the spatial and kinematic structure of the molecular gas inside the heavily dust-obscured core and show that the underlying gas disk is clumpy and rotationally supported (that is, its rotation velocity is larger than the velocity dispersion). Our analysis of the molecular gas mass per unit area suggests that the starburst disk is gravitationally unstable, which implies that the self-gravity of the gas is stronger than the differential rotation of the disk and the internal pressure due to stellar-radiation feedback. As a result of the gravitational instability in the disk, the molecular gas would be consumed by star formation on a timescale of 100 million years, which is comparable to gas depletion times in merging starburst galaxies
.
One of the applications of single-photon emission computed tomography (SPECT) and positron emission tomography (PET) is myocardial imaging. Myocardial perfusion imaging with PET (MPI-PET) is ...gradually becoming an alternative to MPI-SPECT due to its higher image quality. Although Rb-82 is the most common tracer for MPI-PET, Rb-82 emits high-energy positrons with a long stopping range, resulting in blurring of the spatial resolution of the PET image. Due to the limitations of spatial resolution, imaging of Rb-82 in mice has not been reported. In this study, we propose a new method to achieve higher resolution imaging of Rb-82 in small animals than possible with PET imaging by detecting bremsstrahlung X-rays emitted by the positrons, and we validated the feasibility of this method using Monte Carlo simulation. We simulated a small field of view (FOV) pinhole X-ray camera based on a thin YAlO3:Ce (YAP(Ce)) plate and analyzed the basic performance of the simulated camera for bremsstrahlung X-rays. The spatial resolution of a 0.5 mm-thick YAP(Ce) plate-based camera with a 1.0 mm pinhole collimator was 2.6 mm full width at half maximum (FWHM) at a distance of 17.5 mm from the surface of the collimator. Furthermore, we simulated imaging of a mouse heart phantom filled with Rb-82 of 67 MBq per milliliter. We observed the shape of the phantom in the image for a 10 - 45 keV energy window in a simulated measurement time of 4 minutes. We conclude that imaging of high-energy positron emitters at a higher resolution than by PET imaging is possible through detection of the bremsstrahlung X-rays emitted from the positrons.
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