Estimate of halo ellipticity as a function of radius with flexions

The cold dark matter theory predicts triaxial dark matter haloes. The radial distribution of halo ellipticity depends on baryonic processes and the nature of dark matter particles (collisionless or collisional). Here we show that we can use lensing flexion ratios to measure the halo ellipticity as a function of radius. We introduce a weight function and study the relationship between the first and second order statistics of flexion ratios, both of which can be used to reduce the bias in the estimate of ellipticity. we perform numerical tests for our method, and demonstrate that it can reduce the bias and determine the halo ellipticity as a function of radius. We also point out that the minimum mean flexion ratio can be used to trace the centres of galaxy clusters.Comment: 9 pages,9 figures, MNRAS accepte

Spatially resolved study of the molecular isotopologue 13CO in nearby galaxies

Observations of 13CO are indispensable for probing physical conditions in the molecular interstellar medium (ISM) where the most commonly used 12CO emission often saturates, at the cost of weaker emission that is difficult to observe. The line intensity ratio 12CO(1-0)/13CO(1-0) (hereafter R) can be used to trace variations in optical depths determined by the physical conditions, although it can also be influenced by chemical processes. In this thesis, I investigate the 13CO emission and the line ratio R on kiloparsec (kpc) scales for a wide variety of galaxies: 11 galaxies from the CARMA STING survey and 42 galaxies from the CARMA EDGE survey. Using the combination of millimeter-wave interferometry and rich existing auxiliary data for these surveys, I study the molecular gas properties in relation to the stellar population and other ISM components within galaxies and to the global parameters of the galaxies. Among our sample, we find that the R values are higher in the interacting galaxies in the isolated galaxies. However, we do not find a strong dependence of R on global properties such as galaxy type, stellar mass, inclination, or size of the host galaxy. On kilosparsec-scales, lower R values are usually found in regions with weaker 12CO. We attribute this apparent trend to a bias against measuring large values when 12CO is weak. Limiting our analysis to the 12CO-bright regions that are less biased, we do not find that R correlates with the galactocentric distance, velocity dispersion of the gas, or the star formation rate (SFR) measured from 24 um intensity for galaxies in the STING sample. For the EDGE sample, with available IFU optical spectroscopic data at the same resolution, we investigate the relation between R and local stellar and ionized gas properties, such as the instantaneous SFR from Ha emission, gas phase metallicity derived from optical strong line diagnostics, and star formation histories resulting from spectral modeling. For the 12CO-bright regions, we find that in isolated galaxies, R slightly decreases with stellar mass surface density and increases with gas metallicity. On the other hand, there is no significant correlation between R and line width, stellar metallicity, star formation history, SFR, or dust extinction. We also obtain azimuthally averaged R of our sample by stacking multiple 13CO and 12CO spectra in each radial bin. Roughly half of the galaxies show increased stacked R with galactocentric radius, suggesting that a greater fraction of diffuse or less abundant gas contributes to the molecular gas at large radii in general. We conclude that changes in isotopic abundance due to chemical processes or nucleosynthesis do not play a dominant role in R variations on kpc scales. The resolved R is also insensitive to temperature and velocity dispersion. A changing gas density that impacts the opacity and R could account for the general trends we observe on kpc scales. Detailed diagnostics of the properties of molecular ISM will be provided by future high resolution, multi-line molecular observations

Securing Named Data Networking: Attribute-Based Encryption and Beyond

As one of the promising information-centric networking (ICN) architectures, NDN has attracted tremendous research attention and effort in the past decade. In particular, security and privacy remain significant concerns and challenges due to the fact that most of the traditional cryptographic primitives are no longer suitable for NDN architecture. For example, the traditional cryptographic primitives aim to secure point-to-point communications, always requiring explicit descriptions of to where or whom the data packets are intended, while network addressing or locating in NDN becomes implicit. To deal with such issues, the recently developed cryptographic primitives such as ABE have been applied to NDN. Also, to efficiently solve the trust-roots problem and seamlessly deploy cryptographic infrastructures, the concept of SDN has been introduced to NDN as well. This tutorial is devoted to exploring the interesting integration between NDN, ABE, and SDN

Combined effects of cyclic load and temperature fluctuation on the mechanical behavior of porous sandstones

Rocks in cold regions tend to experience exacerbated degradation under the combined effects of environmental and anthropogenic factors, which may arise from, for example, temperature fluctuation, mechanical excavation, and blasting. Activities related to rock support or open-pit slope optimization in cold regions require a complete understanding of the failure mechanisms of rock under the complex conditions. This paper quantitatively documents the impact of combined cyclic mechanical load and freeze-thaw cycles (i.e., the effect of stress “history”) on the microstructural evolution and mechanical degradation of three porous sandstones with distinct porosity values (from 3.9 to 14.1%). The three sandstone samples were collected from different geological regions in China. The microstructural evolution of the tested samples was quantitatively analyzed using the low-field Nuclear Magnetic Resonance (NMR) technique. To investigate sample degradation arising from the impact of the stress “history”, the cyclic-loaded and freeze-thaw cycled samples were eventually compressed to failure, during which an acoustic emission system was used to monitor microseismic activities. The results of the study show that the porosity of all tested sandstone samples was increased after cyclic load, with a much more rapid and further increase in porosity observed for samples being subsequently treated under the freeze-thaw cycles. More interestingly, the Chuxiong sandstone with relatively small porosity values were much more sensitive to the impact of cyclic load compared with the Linyi sandstone, exhibiting a somewhat larger increase rate in porosity. However, the Linyi sandstone with larger initial porosity values exhibited a relatively large increase rate in porosity under the multiple freeze-thaw treatments. The multiple freeze-thaw treatments mainly resulted in the development of relatively large pores. The results of the uniaxial compression tests show that the strength reduction of the samples being solely treated by freeze-thaw cycles was within the range of 5–10%, whereas it was within the range of 20–40% for those samples subjected to the combined cyclic load and freeze-thaw cycles

HI content of massive red spiral galaxies observed by FAST

A sample of 279 massive red spirals was selected optically by Guo et al. (2020), among which 166 galaxies have been observed by the ALFALFA survey. In this work, we observe HI content of the rest 113 massive red spiral galaxies using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). 75 of the 113 galaxies have HI detection with a signal-to-noise ratio (S/N) greater than 4.7. Compared with the red spirals in the same sample that have been observed by the ALFALFA survey, galaxies observed by FAST have on average a higher S/N, and reach to a lower HI mass. To investigate why many red spirals contain a significant amount of HI mass, we check color profiles of the massive red spirals using images observed by the DESI Legacy Imaging Surveys. We find that galaxies with HI detection have bluer outer disks than the galaxies without HI detection, for both ALFALFA and FAST samples. For galaxies with HI detection, there exists a clear correlation between galaxy HI mass and g-r color at outer radius: galaxies with higher HI masses have bluer outer disks. The results indicate that optically selected massive red spirals are not fully quenched, and the HI gas observed in many of the galaxies may exist in their outer blue disks.Comment: 11 pages, 9 figures, accepted by MNRAS; Table 1 is available in the source file

ALMA Observations of a Quiescent Molecular Cloud in the Large Magellanic Cloud

We present high-resolution (sub-parsec) observations of a giant molecular cloud in the nearest star-forming galaxy, the Large Magellanic Cloud. ALMA Band 6 observations trace the bulk of the molecular gas in $^{12}$CO(2-1) and high column density regions in $^{13}$CO(2-1). Our target is a quiescent cloud (PGCC G282.98-32.40, which we refer to as the "Planck cold cloud" or PCC) in the southern outskirts of the galaxy where star-formation activity is very low and largely confined to one location. We decompose the cloud into structures using a dendrogram and apply an identical analysis to matched-resolution cubes of the 30 Doradus molecular cloud (located near intense star formation) for comparison. Structures in the PCC exhibit roughly 10 times lower surface density and 5 times lower velocity dispersion than comparably sized structures in 30 Dor, underscoring the non-universality of molecular cloud properties. In both clouds, structures with relatively higher surface density lie closer to simple virial equilibrium, whereas lower surface density structures tend to exhibit super-virial line widths. In the PCC, relatively high line widths are found in the vicinity of an infrared source whose properties are consistent with a luminous young stellar object. More generally, we find that the smallest resolved structures ("leaves") of the dendrogram span close to the full range of line widths observed across all scales. As a result, while the bulk of the kinetic energy is found on the largest scales, the small-scale energetics tend to be dominated by only a few structures, leading to substantial scatter in observed size-linewidth relationships.Comment: Accepted by ApJ; 21 pages in AASTeX two-column styl

The EDGE-CALIFA Survey: Interferometric Observations of 126 Galaxies with CARMA

We present interferometric CO observations, made with the Combined Array for Millimeter-wave Astronomy (CARMA) interferometer, of galaxies from the Extragalactic Database for Galaxy Evolution survey (EDGE). These galaxies are selected from the Calar Alto Legacy Integral Field Area (CALIFA) sample, mapped with optical integral field spectroscopy. EDGE provides good-quality CO data (3σ sensitivity before inclination correction, resolution ∼1.4 kpc) for 126 galaxies, constituting the largest interferometric CO survey of galaxies in the nearby universe. We describe the survey and data characteristics and products, then present initial science results. We find that the exponential scale lengths of the molecular, stellar, and star-forming disks are approximately equal, and galaxies that are more compact in molecular gas than in stars tend to show signs of interaction. We characterize the molecular-to-stellar ratio as a function of Hubble type and stellar mass and present preliminary results on the resolved relations between the molecular gas, stars, and star-formation rate. We then discuss the dependence of the resolved molecular depletion time on stellar surface density, nebular extinction, and gas metallicity. EDGE provides a key data set to address outstanding topics regarding gas and its role in star formation and galaxy evolution, which will be publicly available on completion of the quality assessment.Fil: Bolatto, Alberto. University of Maryland; Estados UnidosFil: Wong, Tony. University of Illinois at Urbana; Estados UnidosFil: Utomo, Dyas. University of California at Berkeley; Estados UnidosFil: Blitz, Leo. University of California at Berkeley; Estados UnidosFil: Vogel, Stuart N.. University of Maryland; Estados UnidosFil: Sánchez, Sebastián F.. Universidad Nacional Autónoma de México; MéxicoFil: Barrera-Ballesteros, Jorge. University Johns Hopkins; Estados UnidosFil: Cao, Yixian. University of Illinois; Estados UnidosFil: Colombo, Dario. Max Planck Institut Fur Radioastronomie; AlemaniaFil: Dannerbauer, Helmut. Universidad de La Laguna; EspañaFil: García-Benito, Rubén. Instituto de Astrofísica de Andalucía; EspañaFil: Herrera-Camus, Rodrigo. Max Planck Institute für Extraterrestrische Physik; AlemaniaFil: Husemann, Bernd. Max-Planck-Institut für Astronomie; AlemaniaFil: Kalinova, Veselina. Max Planck Institut für Radioastronomie; AlemaniaFil: Leroy, Adam K.. Ohio State University; Estados UnidosFil: Leung, Gigi. Max-Planck-Institut für Astronomie; AlemaniaFil: Levy, Rebecca C.. University of Maryland; Estados UnidosFil: Mast, Damian. Observatorio Astronomico de la Universidad Nacional de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Ostriker, Eve. University of Princeton; Estados UnidosFil: Rosolowsky, Erik. University of Alberta; CanadáFil: Sandstrom, Karin M.. University of California at San Diego; Estados UnidosFil: Teuben, Peter. University of Maryland; Estados UnidosFil: Van De Ven, Glenn. Max-Planck-Institut für Astronomie; AlemaniaFil: Walter, Fabian. Max-Planck-Institut für Astronomie; Alemani