Disk Breaks Research Articles

Varied origins of up-bending breaks in galaxy disks

Aims. Using a sample of 175 low-inclination galaxies from the S4G, we investigate the origins of up-bending (Type III) breaks in the 3.6 μm surface brightness profiles of disk galaxies. Methods. We reanalyzed a sample of previously identified Type III disk break-hosting galaxies using a new, unbiased break-finding algorithm, which uncovered many new, sometimes subtle disk breaks across the whole sample. We classified each break by its likely origin through close examination of the galaxy images across wavelengths, and compare samples of galaxies separated by their outermost identified break types in terms of their stellar populations and local environments. Results. We find that more than half of the confirmed Type III breaks in our sample can be attributed to morphological asymmetry in the host galaxies. As these breaks are mostly an artifact of the azimuthal averaging process, their status as physical breaks is questionable. Such galaxies occupy some of the highest density environments in our sample, implying that much of this asymmetry is the result of tidal disturbance. We also find that Type III breaks related to extended spiral arms or star formation often host down-bending (Type II) breaks at larger radius which were previously unidentified. Such galaxies reside in the lowest density environments in our sample, in line with previous studies that found a lack of Type II breaks in clusters. Galaxies occupying the highest density environments most often show Type III breaks associated with outer spheroidal components. Conclusions. We find that Type III breaks in the outer disks of galaxies arise most often through environmental influence: either tidal disturbance (resulting in disk asymmetry) or heating through, for example, galaxy harrassment (leading to spheroidal components). Galaxies hosting the latter break types also show bimodal distributions in central g − r color and morphological type, with more than half of such galaxies classified as Sa or earlier; this suggests these galaxies may be evolving into early-type galaxies. By contrast, we find that Type III breaks related to apparently secular features (e.g., spiral arms) may not truly define their hosts’ outer disks, as often in such galaxies additional significant breaks can be found at larger radius. Given this variety in Type III break origins, we recommend in future break studies making a more detailed distinction between break subtypes when seeking out, for example, correlations between disk breaks and environment, to avoid mixing unlike physical phenomena.

Inclined massive planets in a protoplanetary disc: gap opening, disc breaking, and observational signatures

We carry out three-dimensional hydrodynamical simulations to study planet-disc interactions for inclined high mass planets, focusing on the disc's secular evolution induced by the planet. We find that, when the planet is massive enough and the induced gap is deep enough, the disc inside the planet's orbit breaks from the outer disc. The inner and outer discs precess around the system's total angular momentum vector independently at different precession rates, which causes significant disc misalignment. We derive the analytical formulae, which are also verified numerically, for: 1) the relationship between the planet mass and the depth/width of the induced gap, 2) the migration and inclination damping rates for massive inclined planets, and 3) the condition under which the inner and outer discs can break and undergo differential precession. Then, we carry out Monte-Carlo radiative transfer calculations for the simulated broken discs. Both disc shadowing in near-IR images and gas kinematics probed by molecular lines (e.g. from ALMA) can reveal the misaligned inner disc. The relationship between the rotation rate of the disc shadow and the precession rate of the inner disc is also provided. Using our disc breaking condition, we conclude that the disc shadowing due to misaligned discs should be accompanied by deep gaseous gaps (e.g. in Pre/Transitional discs). This scenario naturally explains both the disc shadowing and deep gaps in several systems (e.g. HD 100453, DoAr 44, AA Tau, HD 143006) and these systems should be the prime targets for searching young massive planets ($>M_J$) in discs.

The prevalence of type III disc breaks in H i-rich and low-spin galaxies

We investigate the origin of the type III (up-bending) discs based on a sample of 1808 galaxies from SDSS and a sub-sample of 286 galaxies with HI data from ALFALFA. We examine how the type III fraction f3, the fraction of disc galaxies which host up-bending disc breaks, depends on other galactic properties. We confirm that f3 strongly depends on the stellar concentration of galaxies. We find that HI-rich galaxies with low spins tend to have significantly more type III disc breaks than control galaxies, which are matched in concentration and stellar mass. This trend is independent of the existence of strong bars or environment of the galaxies. This result is broadly consistent with predictions from theoretical simulations, and indicates in-situ star formation fueled by gas accretion to be an important mechanism that builds the outer discs of type III galaxies.

Instability of warped discs

Accretion discs are generally warped. If a warp in a disc is too large, the disc can `break' apart into two or more distinct planes, with only tenuous connections between them. Further if an initially planar disc is subject to a strong differential precession, then it can be torn apart into discrete annuli that precess effectively independently. In previous investigations, torque-balance formulae have been used to predict where and when the disc breaks into distinct parts. In this work, focusing on discs with Keplerian rotation and where the shearing motions driving the radial communication of the warp are damped locally by turbulence (the `diffusive' regime), we investigate the stability of warped discs to determine the precise criterion for an isolated warped disc to break. We find and solve the dispersion relation, which in general yields three roots. We provide a comprehensive analysis of this viscous-warp instability and the emergent growth rates and their dependence on disc parameters. The physics of the instability can be understood as a combination of (1) a term which would generally encapsulate the classical Lightman-Eardley instability in planar discs (given by $\partial(\nu\Sigma)/\partial\Sigma < 0$) but is here modified by the warp to include $\partial(\nu_1|\psi|)/\partial|\psi| < 0$ and (2) a similar condition acting on the diffusion of the warp amplitude given in simplified form by $\partial(\nu_2|\psi|)/\partial|\psi| < 0$. We discuss our findings in the context of discs with an imposed precession, and comment on the implications for different astrophysical systems.

Досвід оперативного лікування собак при зміщеннях міжхребцевих дисків

Досвід оперативного лікування собак при зміщеннях міжхребцевих дисків

Signatures of broken protoplanetary discs in scattered light and in sub-millimetre observations

Spatially resolved observations of protoplanetary discs are revealing that their inner regions can be warped or broken from the outer disc. A few mechanisms are known to lead to such 3D structures; among them, the interaction with a stellar companion. We perform a 3D SPH simulation of a circumbinary disc misaligned by $60^\circ$ with respect to the binary orbital plane. The inner disc breaks from the outer regions, precessing as a rigid body, and leading to a complex evolution. As the inner disc precesses, the misalignment angle between the inner and outer discs varies by more than $100^\circ$. Different snapshots of the evolution are post-processed with a radiative transfer code, in order to produce observational diagnostics of the process. Even though the simulation was produced for the specific case of a circumbinary disc, most of the observational predictions hold for any disc hosting a precessing inner rim. Synthetic scattered light observations show strong azimuthal asymmetries, where the pattern depends strongly on the misalignment angle between inner and outer disc. The asymmetric illumination of the outer disc leads to azimuthal variations of the temperature structure, in particular in the upper layers, where the cooling time is short. These variations are reflected in asymmetric surface brightness maps of optically thick lines, as CO $J$=3-2. The kinematical information obtained from the gas lines is unique in determining the disc structure. The combination of scattered light images and (sub-)mm lines can distinguish between radial inflow and misaligned inner disc scenarios.

An Optimal Strategy for Accurate Bulge-to-disk Decomposition of Disk Galaxies

Abstract The development of two-dimensional (2D) bulge-to-disk decomposition techniques has shown their advantages over traditional one-dimensional (1D) techniques, especially for galaxies with non-axisymmetric features. However, the full potential of 2D techniques has yet to be fully exploited. Secondary morphological features in nearby disk galaxies, such as bars, lenses, rings, disk breaks, and spiral arms, are seldom accounted for in 2D image decompositions, even though some image-fitting codes, such as GALFIT, are capable of handling them. We present detailed, 2D multi-model and multi-component decomposition of high-quality R-band images of a representative sample of nearby disk galaxies selected from the Carnegie-Irvine Galaxy Survey, using the latest version of GALFIT. The sample consists of five barred and five unbarred galaxies, spanning Hubble types from S0 to Sc. Traditional 1D decomposition is also presented for comparison. In detailed case studies of the 10 galaxies, we successfully model the secondary morphological features. Through a comparison of best-fit parameters obtained from different input surface brightness models, we identify morphological features that significantly impact bulge measurements. We show that nuclear and inner lenses/rings and disk breaks must be properly taken into account to obtain accurate bulge parameters, whereas outer lenses/rings and spiral arms have a negligible effect. We provide an optimal strategy to measure bulge parameters of typical disk galaxies, as well as prescriptions to estimate realistic uncertainties of them, which will benefit subsequent decomposition of a larger galaxy sample.

How do spiral arm contrasts relate to bars, disc breaks and other fundamental galaxy properties?

We investigate how the properties of spiral arms relate to other fundamental galaxy properties, including bars and disc breaks. We use previously published measurements of those properties, and our own measurements of arm and bar contrasts for a large sample of galaxies, using $3.6 \mathrm{\mu m}$ images from the Spitzer Survey of Stellar Structure in Galaxies (S4G). Flocculent galaxies are clearly distinguished from other spiral arm classes, especially by their lower stellar mass and surface density. Multi-armed and grand-design galaxies are similar in most of their fundamental parameters, excluding some bar properties and the bulge-to-total ratio. Based on these results, we revisit the sequence of spiral arm classes, and discuss classical bulges as a necessary condition for standing spiral wave modes in grand-design galaxies. We find a strong correlation between bulge-to-total ratio and bar contrast, and a weaker correlation between arm and bar contrasts. Barred and unbarred galaxies exhibit similar arm contrasts, but the highest arm contrasts are found exclusively in barred galaxies. Interestingly, the bar contrast, and its increase from flocculent to grand-design galaxies, is systematically more significant than that of the arm contrast. We corroborate previous findings concerning a connection between bars and disc breaks. In particular, in grand-design galaxies the bar contrast correlates with the normalised disc break radius. This does not hold for other spiral arm classes or the arm contrast. Our measurements of arm and bar contrast and radial contrast profiles are publicly available.

INTERNET OF VEHICLES-BASED REAL-TIME VEHICLE TRACKING

The leading-edge vehicle tracking and scanning system based on embedded board is intended and executed to observe any vehicle from different locations. Every year, many numbers of vehicles are stolen. To prohibit thievery, a phenomenal type of negator is preowned, like padlock, disk break lock and more which is a defensive motion, but it is not safe for all designs. The main impartial is to initiate a control entity that shows the locale spot of a vehicle proving by global position system (GPS) to find the position. Here, global system for mobile (GSM) is accepting for communicating with the vehicle that easily finding a steal. The entity is built for trying out the mastery of the locale spot that transmits to the user when the motion is in exciting direction and stable in the city and some other areas. This whole entity is built by bringing together a Raspberry Pi with GPS, general packetradio service (GPRS), and GSM. The preferred entity makes better use of unique automation that based on the Raspberry Pi. This entity works on the GPS and GSM SIM 900A modules which consists all the three things for communication. GPS and GPRS circulate the chasing information to the server to transmit the message to the mobile number which is saved in this sector for communicating through GSM. This preferred entity also acquires the traveler’s protection by testing liquefied petroleum gas effused gas sensor MQ135 and temperature DS18B20 sensor.

Identifying Cause of Rupture Disk Breaks at Alberta Capital Region Wastewater Commission Parkland Pump Station

Identifying Cause of Rupture Disk Breaks at Alberta Capital Region Wastewater Commission Parkland Pump Station

Influence of galaxy stellar mass and observed wavelength on disc breaks in S4G, NIRS0S, and SDSS data

Breaks in the surface brightness profiles in the outer regions of galactic discs are thought to have formed by various internal and external processes, and by studying the breaks we aim to better understand what processes are responsible for the evolution of the outer discs. We use a large well-defined sample to study how common the breaks are, and whether their properties depend on galaxy stellar mass or observed wavelength. We study radial surface brightness profiles of 753 galaxies, obtained from the $3.6 \mu m$ images of the Spitzer Survey of Stellar Structure in Galaxies (S$^4$G), and the $K_s$-band data from the Near InfraRed S0-Sa galaxy Survey (NIRS0S), covering a wide range of galaxy morphologies and stellar masses. Optical SDSS or Liverpool telescope data was used for 480 of these galaxies. We find that in low-mass galaxies the single exponential discs (Type I) are most common, and that their fraction decreases with increasing galaxy stellar mass. The fraction of down-bending (Type II) discs increases with stellar mass, possibly due to more common occurrence of bar resonance structures. The up-bending (Type III) discs are also more common in massive galaxies. The observed wavelength affects the scalelength of the disc of every profile type. Especially the scalelength of the inner disc of Type II profiles increases from infrared to u-band on average by a factor of $\sim 2.2$. Consistent with the previous studies, we find that Type II outer disc scalelengths ($h_o$) in late-type and low-mass galaxies are shorter in bluer wavelengths, possibly due to stellar radial migration populating the outer discs with old stars. In Type III discs $h_o$ are larger in the u-band, hinting to the presence of young stellar population in the outer disc. While the observed wavelength affects the disc parameters, it does not significantly affect the profile type in our sample. (Abridged)

Three-dimensional, global, radiative GRMHD simulations of a thermally unstable disc

We present results of a set of three-dimensional, general relativistic radiation magnetohydrodynamics simulations of thin accretion discs around a non-rotating black hole to test their thermal stability. We consider two cases, one that is initially radiation pressure dominated and expected to be thermally unstable and another that is initially gas-pressure dominated and expected to remain stable. Indeed, we find that cooling dominates over heating in the radiation pressure dominated model, causing the disc to collapse vertically on roughly the local cooling timescale. We also find that heating and cooling within the disc have a different dependence on the mid-plane pressure, a prerequisite of thermal instability. Comparison of our data with the relevant thin-disc thermal equilibrium curve suggests that our disc may be headed for the thermally stable, gas-pressure-dominated branch. However, because the disc collapses to the point that we are no longer able to resolve it, we had to terminate the simulation. On the other hand, the gas pressure dominated model, which was run for twice as long as the radiation pressure dominated one, remains stable, with heating and cooling roughly in balance. Finally, the radiation pressure dominated simulation shows some evidence of viscous instability. The strongest evidence is in plots of surface density, which show the disc breaking up into rings.

A COMPARISON OF SPH ARTIFICIAL VISCOSITIES AND THEIR IMPACT ON THE KEPLERIAN DISK

ABSTRACT Hydrodynamical simulations of rotating disks play important roles in the field of astrophysical and planetary science. Smoothed particle hydrodynamics (SPH) has been widely used for such simulations. However, it has been known that when using SPH, a cold and thin Kepler disk breaks up due to the unwanted angular momentum transfer. Two possible reasons have been suggested for this breaking up of the disk; the artificial viscosity (AV) and the numerical error in the evaluation of pressure gradient in SPH. Which one is dominant is still unclear. In this paper, we investigate the reason for this rapid breaking up of the disk. We implemented most of the popular formulations of AV and switches, and measured the angular momentum transfer due to both AV and the error of SPH’s estimate of the pressure gradient. We found that the angular momentum transfer due to AV at the inner edge triggers the breaking up of the disk. We also found that the classical von Neumann–Richtmyer–Landshoff type AV with a high-order estimate for can maintain the disk for ∼100 orbits even when used with the standard formulation of SPH.

Begging in India: Barricading the Sustainable Financial Development

&lt;div&gt;&lt;p&gt;&lt;em&gt;India is the most powerful country in terms of economy. The rapid growth in economy and population is also increases the poverty in the Indian country. This increasing population is causing disc breaks to the development of economy, with problems such as supply of food and demand of food, begging is one of them which is affecting the Indian economic system in a most serious manner as in the human resource is getting unutilised.&lt;/em&gt;&lt;/p&gt;&lt;p&gt;&lt;em&gt;Begging is most serious social issue in India. Begging is a problem for society is as much as large no. of beggars means not utilization of human resources and available resources in existing environment. This paper tries to examines the reasons causes of begging and the awareness of government schemes run for the people of such kind who are involved in begging at Allahabad.&lt;/em&gt;&lt;/p&gt;&lt;/div&gt;

Erratum: Morphology and environment of galaxies with disc breaks in the S4G and NIRS0S

Erratum: Morphology and environment of galaxies with disc breaks in the S⁴G and NIRS0S

Apsidal precession, disc breaking and viscosity in warped discs

Abstract We demonstrate the importance of general relativistic apsidal precession in warped black hole accretion discs by comparing three-dimensional smoothed particle hydrodynamic simulations in which this effect is first neglected, and then included. If apsidal precession is neglected, we confirm the results of an earlier magnetohydrodynamic simulation which made this assumption, showing that at least in this case the α viscosity model produces very similar results to those of simulations where angular momentum transport is due to the magnetorotational instability. Including apsidal precession significantly changes the predicted disc evolution. For moderately inclined discs thick enough that tilt is transported by bending waves, we find a disc tilt which is non-zero at the inner disc edge and oscillates with radius, consistent with published analytic results. For larger inclinations, we find disc breaking.

Minimum inhibitory concentration values and problematic disk break points of tigecycline against vancomycin and/or high-level aminoglycoside-resistant enterococci

BackgroundTigecycline is a new, semisynthetic glycylcycline. It is active against important multidrug resistant pathogens. AimThe purpose of this study was to investigate the sensitivity of multidrug-resistant enterococci to tigecycline, and to test the correlation between the minimal inhibitory concentration (MIC) and disk diffusion methods. Materials and methodsThe antimicrobial sensitivity of 108 multidrug-resistant isolates, which included 52 vancomycin-resistant enterococci (VRE) and 56 high-level aminoglycoside-resistant (HLAR) enterococci, was tested by the E test, broth microdilution test and disk diffusion methods. ResultsAll of the isolates were sensitive to tigecycline, as determined by the E test and broth microdilution test. The MIC 90 value (0.19μg/mL) of tigecycline for HLAR enterococci was higher than that for VRE (0.094μg/mL). When results were evaluated according to species, the MIC values of tigecycline for Enterococcus faecalis were higher than those for the other species. Eleven (10.1%) isolates produced false resistance results (zone diameter ⩽15mm) by the disk diffusion method. These cases were classified as major errors. Eight (7.4%) isolates had intermediate sensitivity (sensitivity zone of 16 or 17mm), which were classified as minor errors. The major and minor error percentages of HLAR enterococci (14.2% major, 10.7% minor error) were higher than those of VRE (5.7% major, 3.8% minor error). These results indicate that tigecycline is effective against multidrug-resistant enterococci. The sensitivity of multidrug-resistant enterococci to tigecycline should be investigated by MIC methods. The disk diffusion method causes major errors, especially for HLAR enterococci.

Tearing up a misaligned accretion disc with a binary companion

Accretion discs are common in binary systems, and they are often found to be misaligned with respect to the binary orbit. The gravitational torque from a companion induces nodal precession in misaligned disc orbits. We calculate whether this precession is strong enough to overcome the internal disc torques communicating angular momentum. For typical parameters precession wins: the disc breaks into distinct planes that precess effectively independently. We run hydrodynamical simulations to check these results, and confirm that disc breaking is widespread and generally enhances accretion on to the central object. This applies in many cases of astrophysical accretion, e.g. supermassive black hole binaries and X--ray binaries.

A COMMON STOCHASTIC PROCESS RULES GAMMA-RAY BURST PROMPT EMISSION AND X-RAY FLARES

Prompt γ-ray and early X-ray afterglow emissions in gamma-ray bursts (GRBs) are characterized by a bursty behavior and are often interspersed with long quiescent times. There is compelling evidence that X-ray flares are linked to prompt γ-rays. However, the physical mechanism that leads to the complex temporal distribution of γ-ray pulses and X-ray flares is not understood. Here we show that the waiting time distribution (WTD) of pulses and flares exhibits a power-law tail extending over four decades with an index of about two and can be the manifestation of a common time-dependent Poisson process. This result is robust and is obtained on different catalogs. Surprisingly, GRBs with many () γ-ray pulses are very unlikely to be accompanied by X-ray flares after the end of the prompt emission (3.1σ Gaussian confidence). These results are consistent with a simple interpretation: a hyperaccreting disk breaks up into one or a few groups of fragments, each of which is independently accreted with the same probability per unit time. Prompt γ-rays and late X-ray flares are nothing but different fragments being accreted at the beginning and at the end, respectively, following the very same stochastic process and likely the same mechanism.

The environmental dependence of the structure of galactic discs in STAGES S0 galaxies: implications for S0 formation

We present an analysis of V-band radial surface brightness {\mu}(r) profiles for S0s in different environments using HST/ACS imaging and data from the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). Using a sample of ~280 field and cluster S0s, we find that in both environments, ~25 per cent have a pure exponential disc (Type I) and ~50 per cent exhibit an up-bending disc break (antitruncation, Type III). However, we find hardly any (< 5 per cent) down-bending disc breaks (truncations, Type II) in our S0s and many cases (~20 per cent) where no exponential component was observed. We also find no evidence for an environmental dependence on the disc scalelength or break strength (outer-to-inner scalelength ratio), implying that the galaxy environment does not affect the stellar distribution in S0 stellar discs. Comparing disc structure between these S0s and the spirals from our previous studies, we find: i) no evidence for the Type I scalelength being dependent on morphology; and ii) some evidence suggesting the Type II/III break strength is smaller (weaker) in S0s compared to spirals. Taken together, these results suggest that the stellar distribution in S0s is not drastically affected by the galaxy environment. However, some process inherent to the morphological transformation of spirals into S0s does affect the stellar disc causing a weakening of {\mu}(r) breaks and may even eliminate truncations from S0s. In further tests, we perform analytical bulge-disc decompositions on our S0s and compare the results to those for spirals from our previous studies. For Type III galaxies, we find that bulge light can account for the excess light at large radii in up to ~50 per cent of S0s but in only ~15 per cent of spirals. We propose that this result is consistent with a fading stellar disc (evolving bulge-to-disc ratio) being an inherent process in the transformation of spirals into S0s.