Papers for Tuesday, Jan 17 2017
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The Chandra image shows a complex merger event, with at least four components belonging to different merging subclusters. We detect a density discontinuity NNE of this core which we speculate is associated with a cold front.
Our radio images reveal new details for the complex radio relic and radio halo in this cluster. In addition, we properties of the closest young binaries i df taus unequal circumstellar disk evolution several new filamentary radio sources with sizes of kpc.
A few of these seem to be connected to the main radio relic, while others are either embedded within the radio halo or projected onto it. A narrow-angled-tailed NAT radio galaxy, a cluster member, is located at the center of the radio relic. The steep spectrum tails of this AGN leads into the large radio relic where the radio spectrum flattens again. This morphological connection between the NAT radio galaxy and relic provides evidence for re-acceleration revival of fossil electrons.
Searches for stellar companions to hot Jupiters HJs have revealed that planetary systems hosting a HJ are approximately three times more likely to have a stellar companion with a semimajor axis between 50 and AU, compared to field stars. This correlation suggests that HJ formation is properties of the closest young binaries i df taus unequal circumstellar disk evolution by the stellar binary companion.
A potential model is high-eccentricity migration, in which the binary companion induces high-eccentricity Lidov-Kozai LK oscillations in the proto-HJ orbit, triggering orbital migration driven by tides. We propose a modification to the binary-LK model in which there is a second giant planet orbiting the proto-HJ at a semimajor axis of several tens of AU. Such companions are currently hidden to observations, but their presence could be manifested by a propagation of the perturbation of the stellar binary companion inwards to the proto-HJ, thereby overcoming the barrier imposed by short-range forces.
Our prediction for planetary companions to HJs in stellar binaries should be testable by future observations. Both fast and slow configurations of rotating neutron stars NSs are studied with the recently-constructed unified NS EoSs. The calculations for pure quark stars QSs and hybrid stars HSs are also done, using several updated quark matter EoSs and Gibbs construction for obtaining hadron-quark mixed phase.
All three types of EoSs fulfill the recent 2-solar-mass constrain. By confronting the glitch observations with the theoretical calculations for the crustal moment of inertia MoIwe find that the glitch crisis is still present in Vela-like pulsars. An upcoming accurate MoI measurement eg. Accepted for publication in the Astrophysical Journal; 15 pages, 5 figures, 2 tables.
The relative populations in rotational transitions of CO can be useful for inferring gas conditions and excitation mechanisms at work in the interstellar medium. These CO SLEDs are compared to those reported in other galaxies, with the intention of empirically determining which mechanisms dominate excitation in such systems. We find that CO SLEDs in Galactic star-forming cores cannot be used to reproduce those observed in other galaxies, although the discrepancies arise primarily as a result of beam filling factors.
The much larger regions sampled by the Herschel beams at distances of several Mpc contain significant amounts of cooler gas which dominate the extragalactic CO SLEDs, in contrast to observations of Galactic star-forming regions which are focused specifically on cores containing primarily hot molecular gas. Albeit radial migration must be a ubiquitous process in disk galaxies, its significance in the evolution of stellar discs is not always reflected through global simple trends e.
However, there are other key observables, such as the metallicity distribution function MDFthat may shed some light in this matter. We argue that the shape of the MDF not only tells us whether the stellar disc experienced radial migration, but it also contains important clues on the structure that triggered it. Specifically, the MDF contains information about the dynamics and morphology of the spiral pattern e.
In order to constrain the spiral parameters, we have included a detailed recipe for the chemical tagging in our simulations; this allows properties of the closest young binaries i df taus unequal circumstellar disk evolution to produce a restriction of the structural parameters of the spiral arms in the Milky Way as well as a method to constrain chemical evolution models towards the center of the Galactic disc, where properties of the closest young binaries i df taus unequal circumstellar disk evolution chemical model provides information.
We also show that a stellar disc that has evolved dynamically and chemically can preserve a global metallicity gradient despite of having suffered important heating and radial migration; this means that the presence of a metallicity gradient in a given galaxy, does not guarantee that radial mixing has not played a role in the evolution of the galaxy. We present a low-frequency view of the Perseus cluster with new observations from the Karl G.
The data reveal a multitude of new structures associated with the mini-halo. The mini-halo seems to be influenced both by the AGN activity as well as by the sloshing motion of the cool core cluster's gas. In addition, it has a filamentary structure similar to that seen in radio relics found in merging clusters. We present a detailed description of the data reduction and imaging process of the dataset. The depth and resolution of the observations allow us to conduct for the first time a detailed comparison of the mini-halo structure with the X-ray structure as seen in the Chandra X-ray images.
The resulting image shows very clearly that the mini-halo emission is mostly contained behind the cold fronts, similar to that predicted by simulations of gas sloshing in galaxy clusters. However, due to the proximity of the Perseus cluster, as well as the quality of the data at low radio frequencies and at X-ray wavelengths, we also find evidence of fine structure.
This structure includes several radial radio filaments extending in different directions, a concave radio structure associated with the southern X-ray bay and sharp edges that correlate with X-ray edges. Mini-halos are therefore not simply diffuse, uniform radio sources, but are rather filled with a rich variety of complex structures.
These results illustrate the high-quality images that can be obtained with the new JVLA at low radio-frequencies, as well as the necessity to obtain deeper, higher-fidelity radio images of mini-halos and halos in clusters to further understand their origin. Despite the complexities of baryonic physics, the simple addition of an embedded central disk potential to DMO simulations reproduces this subhalo depletion, including trends with radius, remarkably well.
Thus, the additional tidal field from the central galaxy is the primary cause of subhalo depletion. Subhalos on radial orbits that pass close to the central galaxy are preferentially destroyed, causing the surviving subhalo population to have tangentially biased orbits compared to DMO predictions. Our method of embedding a disk potential in DMO simulations provides a fast and accurate properties of the closest young binaries i df taus unequal circumstellar disk evolution to full baryonic simulations, thus enabling suites of cosmological simulations that can provide accurate and statistical predictions of substructure populations.
As early as twenty-five years ago, little was known about them, however since the first systematic survey was completed in the s, increasing amounts of resources have been devoted to their discovery and research. This book summarises for the first time the numerous techniques used for observing, analysing, and understanding the evolution and formation of these distant galaxies.
In this rapidly expanding research field, this text is an every-day companion handbook for graduate students and active researchers. It provides guidelines in sample selection, imaging, integrated spectroscopy and 3D spectroscopy, which help to avoid the numerous pitfalls of observational and analysis techniques in use in extragalactic astronomy.
It also paves the way for establishing relations between fundamental properties of distant galaxies. At each step, the reader is assisted with numerous practical examples and ready-to-use methodology to help understand and analyse research. The secular approximation of the hierarchical three body systems has been proven to be very useful in addressing many astrophysical systems, from planets, stars to black holes.
In such a system two objects are on a tight orbit, and the tertiary is on a much wider orbit. Here we study the dynamics of a system by taking the tertiary mass to zero and solve the hierarchical three body system up to the octupole level of approximation. We find a rich dynamics that the outer orbit undergoes due to gravitational perturbations from the inner binary. The nominal result of properties of the closest young binaries i df taus unequal circumstellar disk evolution precession of the nodes is mostly limited for the lowest order of approximation, however, when the octupole-level of approximation is introduced the system becomes chaotic, as expected, and the tertiary oscillates below and above 90deg, similarly to the non-test particle flip behavior e.
We provide the Hamiltonian of the system and investigate the dynamics of the system from the quadrupole to the octupole level of approximations. We also analyze the chaotic and quasi-periodic orbital evolution by studying the surfaces of sections.
Furthermore, including general relativity, we show case the long term evolution of individual debris disk particles under the influence of a far away interior eccentric planet.
We show that this dynamics can naturally result in retrograde objects and a puffy disk after a long timescale evolution few Gyr for initially aligned configuration. We examine properties of the closest young binaries i df taus unequal circumstellar disk evolution optical photometric and polarimetric variability of the luminous type 1 non-blazar quasar 3C Taking the above-mentioned photometric and polarimetric variability properties and the results from previous studies into consideration, we propose a geometrical model for the polarization source in 3C Magnetic fields play an important role in the dynamics of accretion disks, however, the origin of the fields is often obscured.
Here we show that magnetic fields can be generated in an initially non-magnetized accretion disks through the Biermann battery mechanism, where the radial temperature profile and the vertical density profile of these systems provide the necessarily conditions for this process to operate naturally.
We consider the generation of fields in a protoplanetary disks and disks around Black Holes BHs. The generated seeds have toroidal structure with opposite sign in the upper and lower half of the disk. The same pattern exists in a thin accretion disk around a rotating BH, where the field generation rate increases for larger BH's spin parameters in a co-rotating disk and spin configuration.
In addition, we test this mechanism in GRMHD simulations and find it to be in a good agreement with our analytical estimates. The fact that the battery works in the limit of zero accretion rate, it makes this mechanism a viable candidate to provide the seed fields from an initially non-magnetized accretion disk such that later on Magneto Rotational Instability MRI takes over.
Accepted to New Astronomy. In time domain astronomy, recurrent transients present a special problem: Monitoring properties of the closest young binaries i df taus unequal circumstellar disk evolution may give a biassed view of the underlying population due to limitations on observing time, visibility and instrumental sensitivity.
A similar problem exists in the life sciences, where animal populations such as migratory birds or disease prevalence, must be estimated from sparse and incomplete data. The class of methods termed Capture-Recapture is used to reconstruct population estimates from time-series records of encounters with the study population. This paper investigates the performance of Capture-Recapture methods in astronomy via a series of numerical simulations.
The Blackbirds code simulates monitoring of populations of transients, in this case accreting binary stars neutron star or black hole accreting from a stellar companion under a range of observing strategies. We first generate realistic light-curves for populations of binaries with contrasting orbital period distributions.
These models are then randomly sampled at observing cadences typical of existing and planned monitoring surveys. The classical capture-recapture methods, Lincoln-Peterson, Schnabel estimators, related techniques, and newer methods implemented in the Rcapture package are compared. Capture-Recapture is a promising addition to the toolbox of time domain astronomy, and methods implemented in R by the biostats community can be readily called from within Python.
In young starburst galaxies, the X-ray population is expected to be dominated by the relics of the most massive and short-lived stars, black-hole and neutron-star high mass X-ray binaries XRBs. In the closest such galaxy, IC 10, we have made a multi-wavelength census of these objects. Employing a novel statistical correlation technique, we have matched our list of X-ray point sources, derived from a decade of Chandra observations, against published photometric data.
We report an 8 sigma correlation between the celestial coordinates of the properties of the closest young binaries i df taus unequal circumstellar disk evolution catalogs, with 42 X-ray sources having an optical counterpart. Applying an optical color-magnitude selection to isolate blue supergiant SG stars in IC 10, we find 16 matches.
Both cases show a statistically significant overabundance versus the expectation value for chance alignments. Blue SG-XRBs include a major class of progenitors of double-degenerate binaries, hence their numbers are an important factor in modeling the rate of gravitational wave sources.
We suggest that the anomalous features of the IC 10 stellar population are explained if the age of the IC 10 starburst is close to the time of the peak of interaction for massive binaries. We describe the structural, stellar population and gas properties of the nearest Ultra Diffuse Galaxy UDG discovered so far: This galaxy, located at a distance of If the object were to stop forming stars at this moment, after a passive evolution, its surface brightness would become extremely faint: Such faintness would make it almost undetectable to most present-day surveys.
We report the discovery of a multi-planet system orbiting HDa rapidly rotating mid F-type star, using data from the K2 mission.
The projected rotational velocity of HD The eccentricities of both planets were constrained to be consistent with 0, following a global modeling of the system that includes a GAIA distance and dynamical properties of the closest young binaries i df taus unequal circumstellar disk evolution. The HD system is one of few multi-planet systems hosting Neptunes and super-Earths for which orbital obliquity measurements are possible, making it an excellent test-case for formation mechanisms of warm-Neptunian systems.
The brightness of the host star also makes HD c a candidate for future transmission spectroscopic follow-up studies. We present new optical broad-band UBVRI aperture polarimetric observations of 53 post-asymptotic giant branch AGB stars selected to exhibit a large near-infrared excess.
A statistical analysis shows four distinctive groups of polarized post-AGB stars: