bluuebunny/crossref_metadata_2025_split huggingface dataset:
Frequency shifts of resonant modes of the Sun due to near-surface convective scattering
Authors: Bhattacharya J. , Hanasoge S. M. , Antia H. M. 
Published: October 2016

AbstractMeasurements of oscillation frequencies of the Sun and stars can provide important independent constraints on their internal structure and dynamics. Seismic models of these oscillations are used to connect structure and rotation of the star to its resonant frequencies, which are then compared with observations, the goal being that of minimizing the difference between the two. Even in the case of the Sun, for which structure models are highly tuned, observed frequencies show systematic deviations from modeled frequencies, a phenomenon referred to as the “surface term.” The dominant source of this systematic effect is thought to be vigorous near-surface convection, which is not well accounted for in both stellar modeling and mode-oscillation physics. Here we bring to bear the method of homogenization, applicable in the asymptotic limit of large wavelengths (in comparison to the correlation scale of convection), to characterize the effect of small-scale surface convection on resonant-mode frequencies in the Sun. We show that the full oscillation equations, in the presence of temporally stationary 3D flows, can be reduced to an effective “quiet-Sun” wave equation with altered sound speed, Brünt–Väisäla frequency, and Lamb frequency. We derive the modified equation and relations for the appropriate averaging of 3D flows and thermal quantities to obtain the properties of this effective medium. Using flows obtained from 3D numerical simulations of near-surface convection, we quantify their effect on solar oscillation frequencies and find that they are shifted systematically and substantially. We argue therefore that consistent interpretations of resonant frequencies must include modifications to the wave equation that effectively capture the impact of vigorous hydrodynamic convection.
Cosmic Bulk Flow and the Local motions from CosmicFlows-2 dataset
Authors: Courtois H. M. 
Published: October 2016

AbstractUsing the largest and most accurate ever catalog of galaxy peculiar velocities Cosmicflows-2, the large scale structure has been reconstructed by means of the Wiener filter and constrained realizations assuming as a Bayesian prior model the LCDM standard model of cosmology. Our main result is that the estimated bulk flow is consistent with the LCDM model with the WMAP inferred cosmological parameters. At R=50 (150)Mpc/h the estimated bulk velocity is 250 ± 21 (239 ± 38) km/s. The SGX and SGY components of the CMB dipole velocity are recovered by the Wiener Filter (WF) velocity field down to a very few km/s. The SGZ component of the estimated velocity, the one that is most affected by the Zone of Avoidance, is off by 126 km/s (an almost 2 sigma discrepancy).
Filament Formation in Molecular Clouds as a Scale-Free Process
Authors: Vázquez-Semadeni Enrique , Gómez Gilberto 
Published: October 2016

AbstractWe discuss the formation of filaments in molecular clouds (MCs) as the result of large-scale collapse in the clouds. We first give arguments suggesting that self-gravity dominates the nonthermal motions, and then briefly describe the resulting structure, similar to that found in molecular-line and dust observations of the filaments in the clouds. The filaments exhibit a hierarchical structure in both density and velocity, suggesting a scale-free nature, similar to that of the cosmic web, resulting from the domination of self-gravity from the MC down to the core scale.
The linewidth-size scaling law of molecular gas revisited
Authors: Falgarone Edith , McKee Christopher F. 
Published: October 2016

AbstractThe origin of the linewidth-size (LWS) scaling law, first noticed by Larson three decades ago and ascribed to turbulence, is still a highly debated issue. Not unexpectedly, its properties depend on the environment and on the line tracer used. When the optically thick 12CO (J=1-0) line is used, a specific medium is sampled: the translucent molecular gas of moderate density that builds up the bulk of the molecular interstellar medium in galaxies like the Milky Way. The sensitivity of the 12CO line to this gas is such that the LWS is found to hold over almost five orders of magnitude in lengthscale, although with a considerable scatter (± 0.5 dex). It also appears to split into two regimes, depending on the gas mass surface density: below a given threshold that is proposed to be linked to the galactic structure, it bears the signature of a turbulent cascade, while above it, the scaling law is ascribed to virial balance. Large deviations from the LWS scaling law are observed at small scales where signatures of turbulent intermittency appear. The mass-size scaling law built with the 12CO (J=1-0) line also splits into two regimes. The mass surface density is uniform (also with a large scatter) above lengthscales ~ 10pc and increases with size at smaller scales, following turbulence predictions. The two thresholds define an average gas density nH ~ 300 cm−3.
A Self-Critique of Self-Organized Criticality in Astrophysics
Authors: Aschwanden Markus J. 
Published: October 2016

AbstractThe concept of “self-organized criticality” (SOC) was originally proposed as an explanation of 1/f-noise by Bak, Tang, and Wiesenfeld (1987), but turned out to have a far broader significance for scale-free nonlinear energy dissipation processes occurring in the entire universe. Over the last 30 years, an inspiring cross-fertilization from complexity theory to solar and astrophysics took place, where the SOC concept was initially applied to solar flares, stellar flares, and magnetospheric substorms, and later extended to the radiation belt, the heliosphere, lunar craters, the asteroid belt, the Saturn ring, pulsar glitches, soft X-ray repeaters, blazars, black-hole objects, cosmic rays, and boson clouds. The application of SOC concepts has been performed by numerical cellular automaton simulations, by analytical calculations of statistical (powerlaw-like) distributions based on physical scaling laws, and by observational tests of theoretically predicted size distributions and waiting time distributions. Attempts have been undertaken to import physical models into numerical SOC toy models. The novel applications stimulated also vigorous debates about the discrimination between SOC-related and non-SOC processes, such as phase transitions, turbulence, random-walk diffusion, percolation, branching processes, network theory, chaos theory, fractality, multi-scale, and other complexity phenomena. We review SOC models applied to astrophysical observations, attempt to describe what physics can be captured by SOC models, and offer a critique of weaknesses and strengths in existing SOC models.
A Spatial Study of X-ray Properties in Superbubble 30 Dor C with XMM-Newton
Authors: Babazaki Y. , Mitsuishi I. , Sano H. , Yoshiike S. , Fukuda T. , Maruyama S. , Fujii K. , Fukui Y. , Tawara Y. , Matsumoto H 
Published: October 2016

AbstractThe superbubble (SB) 30 Dor C with the strong non-thermal X-ray emission is one of the best targets for study of the cosmic-ray (CR) acceleration. We investigated X-ray spectral properties of the SB with a high spatial resolution of ~10 pc. Consequently, the spectra in the east regions can be described with a combination of absorbed thermal and non-thermal models while the spectra in the west regions can be fitted with an absorbed non-thermal model. We found that the observed photon index and intensity in 2-10 keV show variations of 2.0-3.5 and (0.6-8.0) × 10−7 erg s−1 cm−2 str−1, respectively. The results are possibly caused by the spatial variation of the CR acceleration efficiency and/or the circumstellar environment.
Transonic galactic outflows in a dark matter halo with a central black hole
Authors: Igarashi Asuka , Mori Masao , Nitta Shin-ya 
Published: October 2016

AbstractWe study fundamental properties of transonic galactic outflows in the gravitational potential of a cold dark matter halo (DMH) with a central super-massive black hole (SMBH) assuming an isothermal, steady and spherically symmetric state. Transonic solutions of galactic outflows are classified according to their topological features. As result, we find two types of transonic solutions distinguished by a magnitude relationship between the gravity of DMH and that of SMBH. The loci of transonic points for two types are different; one transonic point is formed at a central region (< 0.01kpc) and another is at a very distant region (> 100kpc). Also, mass fluxes and outflow velocities are different for two solutions. Thus, these solutions may differently influence the evolution of galaxies and the release of metals into the intergalactic space.Furthermore, we apply our model to the Sombrero galaxy. In this galaxy, the wide-spread hot gas is detected as the trace of galactic outflows while the star-formation rate is low, and the observed gas density distribution is similar to the hydrostatic state (Li et al. 2011). To solve this discrepancy, we propose a solution that this galaxy has a slowly accelerating outflow; the transonic point forms in a very distant region (~ 120 kpc) and the wide subsonic region spreads across the stellar distribution. Thus, the gas density distribution in the observed region is similar to the hydrostatic state. Such slowly accelerating outflows are different from high-velocity outflows conventionally studied (Igarashi et al. 2014).However, this isothermal model requires an unrealistically large mass flux. Then, we apply the polytropic model to this galaxy incorporating mass flux supplied by stellar components. We find that it can reproduce the observed gas density and the temperature distributions with the realistic mass flux. Thus, our polytropic model successfully demonstrates the existence of the slowly accelerating outflow in the Sombrero galaxy (Igarashi et al. 2015).
A novel approach to gravitation from fluid theory: Titius-Bode structures, flat rotation rate of galaxies, and other predictions
Authors: Munera Hector A. 
Published: October 2016

AbstractFollowing the discovery of quantum phenomena at laboratory scale (Couder & Fort 2006), de Broglie pilot wave theory (De Broglie 1962) has been revived under a hydrodynamic guise (Bush 2015). Theoretically, it boils down to solving the transport equations for the energy and linear momentum densities of a postulated fundamental fluid in terms of classical wave equations, which inherently are Lorentz-invariant and scale-invariant. Instead of the conventional harmonic solutions, for astronomical and gravitational problems the novel solutions for the homogeneous wave equation in spherical coordinates are more suitable (Munera et al. 1995, Munera & Guzman 1997, and Munera 2000). Two groups of solutions are particularly relevant: (a) The inherently-quantized helicoidal solutions that may be applicable to describe spiral galaxies, and (b) The non-harmonic solutions with time (t) and distance (r) entangled in the single variable q = Ct/r (C is the two-way local electromagnetic speed). When these functions are plotted against 1/q they manifestly depict quantum effects in the near field, and Newtonian-like gravity in the far-field. The near-field predicts quantized effects similar to ring structures and to Titius-Bode structures, both in our own solar system and in exoplanets, the correlation between predicted and observed structures being typically larger than 99 per cent. In the far-field, some non-harmonic functions have a rate of decrement with distance slower than inverse-square thus explaining the flat rotation rate of galaxies. Additional implications for Trojan orbits, and quantized effects in photon deflection were also noted.
Scale-free convection theory
Authors: Pasetto Stefano , Chiosi Cesare , Cropper Mark , Grebel Eva K. 
Published: October 2016

AbstractConvection is one of the fundamental mechanisms to transport energy, e.g., in planetology, oceanography, as well as in astrophysics where stellar structure is customarily described by the mixing-length theory, which makes use of the mixing-length scale parameter to express the convective flux, velocity, and temperature gradients of the convective elements and stellar medium. The mixing-length scale is taken to be proportional to the local pressure scale height of the star, and the proportionality factor (the mixing-length parameter) must be determined by comparing the stellar models to some calibrator, usually the Sun. No strong arguments exist to claim that the mixing-length parameter is the same in all stars and all evolutionary phases. Because of this, all stellar models in the literature are hampered by this basic uncertainty. In a recent paper (Pasetto et al. 2014) we presented the first fully analytical scale-free theory of convection that does not require the mixing-length parameter. Our self-consistent analytical formulation of convection determines all the properties of convection as a function of the physical behaviour of the convective elements themselves and the surrounding medium (be it a star, an ocean, or a primordial planet). The new theory of convection is formulated starting from a conventional solution of the Navier-Stokes/Euler equations, i.e. the Bernoulli equation for a perfect fluid, but expressed in a non-inertial reference frame co-moving with the convective elements. In our formalism, the motion of convective cells inside convective-unstable layers is fully determined by a new system of equations for convection in a non-local and time dependent formalism. We obtained an analytical, non-local, time-dependent solution for the convective energy transport that does not depend on any free parameter. The predictions of the new theory in astrophysical environment are compared with those from the standard mixing-length paradigm in stars with exceptional results for atmosphere models of the Sun and all the stars in the Hertzsprung-Russell diagram.
X-raying the Hubble Frontier Fields cluster Abell 2744
Authors: Eckert Dominique 
Published: October 2016

AbstractAbell 2744 was the first HFF cluster completed. It displays a fascinating complexity in its distribution of dark and luminous matter, which led to its nickname of the Pandora cluster. In late 2014 we obtained a deep (110 ks) observation of this cluster with XMM-Newton, with the aim of making a detailed comparison between the optical, X-ray and lensing properties of this system. The new X-ray observation unveiled the presence of three hot gas filaments extending on scales of several Mpc and connected to the cluster core. The X-ray structures coincide spatially with the distribution of galaxies and dark matter and provide strong evidence for the existence of the elusive warm-hot intergalactic medium (WHIM). The new observation also reveals the complexity of the thermodynamic structure of the cluster core and a probable shock front associated with the radio relic located 1 Mpc NW of the cluster core.
The MUSE view of the Frontier Field clusters
Authors: Richard Johan , Mahler Guillaume , Clément Benjamin , Lagattuta David , Patriício Vera , Pelló Roser , Bina David ,   the MUSE consortium
Published: October 2016

AbstractStrong gravitational magnification in the core of lensing clusters allows to probe the faint-end of the galaxy luminosity function up to very high redshift. In particular, the Frontier Fields have allowed us to identify a large number of faint dropouts and constrain the Lyman-break luminosity function at z~5-7. I present here the results of an ongoing program with MUSE, a new integral field spectrograph on the Very Large Telescope having a large field of view (1 arcmin2), to confirm these candidate high redshift dropouts through Lyman-α emission and identify additional emitters with high equivalent width, fainter than the depth of the Frontier Fields Hubble images. Combined with similar deep exposures taken with MUSE in blank fields, this gives us the best opportunity to probe the Lyman-α luminosity function over a wide range in luminosity.
Automatic Selection of Multiple Images in the Frontier Field Clusters
Authors: Mahler Guillaume , Richard Johan , Clément Benjamin , Lagattuta David , Patricio Vera 
Published: October 2016

AbstractProbing the central mass distribution of massive galaxy clusters is an important step towards mapping the overall distribution of their dark matter content. Thanks to gravitational lensing and the appearance of multiple images, we can constrain the inner region of galaxy clusters with a high precision. The Frontier Fields (FF) provide us with the deepest HST data ever in such clusters. Currently, most multiple-image systems are found by eye, yet in the FF, we expect hundreds to exist. Thus, in order to deal with such huge amounts of data, we need to develop an automated detection method. I present a new tool to perform this task, MISE (Multiple Image SEarcher), a program which identifies multiple images by combining their specific properties. MISE allows us to confirm or reject multiple images identified visually, but also detect new multiple-image candidates in MACS0416 and A2744, giving us additional constraints on the mass distribution in these clusters. A spectroscopic follow-up of these candidates is currently underway with MUSE.
Strong Lensing Mass Reconstruction: from Frontier Fields to the Typical Lensing Clusters of Future Surveys
Authors: Sharon Keren , Gladders Michael D. , Rigby Jane R. , Bayliss Matthew B. , Wuyts Eva , Dahle Håkon , Johnson Traci L. , Florian Michael K. , Dunham Samuel , Murray Katherine , Whitaker Kate , Li Nan 
Published: October 2016

AbstractDriven by the unprecedented wealth of high quality data that is accumulating for the Frontier Fields, they are becoming some of the best-studied strong lensing clusters to date, and probably the next few years. As will be discussed intensively in this focus meeting, the FF prove transformative for many fields: from studies of the high redshift Universe, to the assembly and structure of the clusters themselves. The FF data and the extensive collaborative effort around this program will also allow us to examine and improve upon current lens modeling techniques. Strong lensing is a powerful tool for mass reconstruction of the cores of galaxy clusters of all scales, providing an estimate of the total (dark and seen) projected mass density distribution out to 0.5 Mpc. Though SL mass may be biased by contribution from structures along the line of sight, its strength is that it is relatively insensitive to assumptions on cluster baryon astrophysics and dynamical state. Like the Frontier Fields clusters, the most “famous” strong lensing clusters are at the high mass end; they lens dozens of background sources into multiple images, providing ample lensing constraints. In this talk, I will focus on how we can leverage what we learn from modeling the FF clusters in strong lensing studies of the hundreds of clusters that will be discovered in upcoming surveys. In typical clusters, unlike the Frontier Fields, the Bullet Cluster and A1689, we observe only one to a handful of background sources, and have limited lensing constraints. I will describe the limitations that such a configuration imposes on strong lens modeling, highlight measurements that are robust to the richness of lensing evidence, and address the sources of uncertainty and what sort of information can help reduce those uncertainties. This category of lensing clusters is most relevant to the wide cluster surveys of the future.
Substructure in the Frontier Fields from weak lensing flexion
Authors: Rexroth Markus 
Published: October 2016

AbstractFlexion is the second order weak gravitational lensing effect responsible for the arclike appearance of sources. It is highly sensitive to dark matter substructure and can greatly increase the resolution of mass maps, but it is very hard to measure. We present an automated flexion measurement pipeline for Hubble Space Telescope data and a preliminary application to the Frontier Fields cluster MACSJ0416.1-2403.
Strong Lensing Cosmography in the Frontier Fields
Authors: Jullo Eric , Acebron Ana , Limousin Marceau , Giocoli Carlo , Despali Giulia , Bonamigo Mario ,   the CATS team
Published: October 2016

AbstractThe wealth of strong lensing features observed in the Frontier Fields clusters offers insights on the nature of dark energy. The large number of multiple-images systems with redshifts allows to simultaneously estimate the lens model parameters and the cosmological parameters involved in the distances calculations. In particular for the ΛCDM model, it is possible to estimate the matter density Ωm and the dark energy equations parameters wX. In this talk, I will present recent analyses of systematic errors based on Frontier Fields observed and simulated data.
Crystal structures of the ATP-binding and ADP-release dwells of the V1 rotary motor
Authors: Suzuki Kano , Mizutani Kenji , Maruyama Shintaro , Shimono Kazumi , Imai Fabiana L. , Muneyuki Eiro , Kakinuma Yoshimi , Ishizuka-Katsura Yoshiko , Shirouzu Mikako , Yokoyama Shigeyuki , Yamato Ichiro , Murata Takeshi 
Published: October 2016

AbstractV1-ATPases are highly conserved ATP-driven rotary molecular motors found in various membrane systems. We recently reported the crystal structures for the Enterococcus hirae A3B3DF (V1) complex, corresponding to the catalytic dwell state waiting for ATP hydrolysis. Here we present the crystal structures for two other dwell states obtained by soaking nucleotide-free V1 crystals in ADP. In the presence of 20 μM ADP, two ADP molecules bind to two of three binding sites and cooperatively induce conformational changes of the third site to an ATP-binding mode, corresponding to the ATP-binding dwell. In the presence of 2 mM ADP, all nucleotide-binding sites are occupied by ADP to induce conformational changes corresponding to the ADP-release dwell. Based on these and previous findings, we propose a V1-ATPase rotational mechanism model.
Sulfur mass-independent fractionation in subsurface fracture waters indicates a long-standing sulfur cycle in Precambrian rocks
Authors: Li L. , Wing B. A. , Bui T. H. , McDermott J. M. , Slater G. F. , Wei S. , Lacrampe-Couloume G. , Lollar B. Sherwood 
Published: October 2016

AbstractThe discovery of hydrogen-rich waters preserved below the Earth’s surface in Precambrian rocks worldwide expands our understanding of the habitability of the terrestrial subsurface. Many deep microbial ecosystems in these waters survive by coupling hydrogen oxidation to sulfate reduction. Hydrogen originates from water–rock reactions including serpentinization and radiolytic decomposition of water induced by decay of radioactive elements in the host rocks. The origin of dissolved sulfate, however, remains unknown. Here we report, from anoxic saline fracture waters ∼2.4 km below surface in the Canadian Shield, a sulfur mass-independent fractionation signal in dissolved sulfate. We demonstrate that this sulfate most likely originates from oxidation of sulfide minerals in the Archaean host rocks through the action of dissolved oxidants (for example, HO·and H2O2) themselves derived from radiolysis of water, thereby providing a coherent long-term mechanism capable of supplying both an essential electron donor (H2) and a complementary acceptor (sulfate) for the deep biosphere.