Miracle-dz/UniFAR-FTUs huggingface dataset:
Massive black hole binaries from runaway collisions: the impact of metallicity

The runaway collision scenario is one of the most promising mechanisms to explain the formation of intermediate-mass black holes (IMBHs) in young dense star clusters. On the other hand, the massive stars that participate in the runaway collisions lose mass by stellar winds. In this paper, we discuss new N-body simulations of massive (6.5x10^4 Msun) star clusters, in which we added upgraded recipes for stellar winds and supernova explosion at different metallicity. We follow the evolution of the principal collision product (PCP), through dynamics and stellar evolution, till it forms a stellar remnant. At solar metallicity, the mass of the final merger product spans from few solar masses up to ~30 Msun. At low metallicity (0.01-0.1 Zsun) the maximum remnant mass is ~250 Msun, in the range of IMBHs. A large fraction (~0.6) of the PCPs are not ejected from the parent star cluster and acquire stellar or black hole (BH) companions. Most of the long-lived binaries hosting a PCP are BH-BH binaries. We discuss the importance of this result for gravitational wave detection.
Hot graphite dust and the infrared spectral energy distribution of active galactic nuclei

We present a detailed investigation of the near-infrared to far-infrared (near-IR to far-IR) spectral energy distribution (SED) of a large sample of Spitzer-observed active galactic nuclei (AGNs). We fitted the spectra of 51 narrow-line Seyfert 1 galaxies (NLS1s) and 64 broad-line Seyfert 1 galaxies (BLS1s) using a three-component model: a clumpy torus, a dusty narrow-line region and hot pure-graphite dust located in the outer part of the broad-line region (BLR). The fitting was performed on star formation (SF) subtracted SEDs using SF templates that take into account the entire range of possible host galaxy properties. We find that the mid-IR intrinsic emission of NLS1s and BLS1s is very similar, regardless of the AGN luminosity, with long-wavelength downturn at around 20–25 μm. We present a detailed model of the hot-dust component that takes into account the distribution of dust temperature within the clouds and their emission-line spectrum. The hot-dust continuum provides a very good fit to the observed near-IR continuum spectrum. Most line emission in this component is dramatically suppressed, except Mg ii λ2798 and He i lines that are still contributing significantly to the total BLR spectrum. We calculate the covering factors (CFs) of all the AGN components and show that the CF of the hot-dust clouds is about 0.15–0.35, similar to the CF of the torus, and is anticorrelated with the source luminosity and the normalized accretion rate.
On the nature of magnetic turbulence in rotating, shearing flows

The local properties of turbulence driven by the magnetorotational instability (MRI) in rotating, shearing flows are studied in the framework of a shearing-box model. Based on numerical simulations, we propose that the MRI-driven turbulence comprises two components: the large-scale shear-aligned strong magnetic field and the small-scale fluctuations resembling magnetohydrodynamic (MHD) turbulence. The energy spectrum of the large-scale component is close to $k^{-2}$, whereas the spectrum of the small-scale component agrees with the spectrum of strong MHD turbulence $k^{-3/2}$. While the spectrum of the fluctuations is universal, the outer-scale characteristics of the turbulence are not; they depend on the parameters of the system, such as the net magnetic flux. However, there is remarkable universality among the allowed turbulent states -- their intensity $v_0$ and their outer scale $\lambda_0$ satisfy the balance condition $v_0/\lambda_0\sim \mathrm d\Omega/\mathrm d\ln r$, where $\mathrm d\Omega/\mathrm d\ln r$ is the local orbital shearing rate of the flow. Finally, we find no sustained dynamo action in the $\mathrm{Pm}=1$ zero net-flux case for Reynolds numbers as high as $45\,000$, casting doubts on the existence of an MRI dynamo in the $\mathrm{Pm}\leq 1$ regime.
Continuous upflows and sporadic downflows observed in active regions

We present a study of the temporal evolution of coronal loops in active regions and its implications for the dynamics in coronal loops. We analyzed images of the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) at multiple temperatures to detect apparent motions in the coronal loops. Quasi-periodic brightness fluctuations propagate upwards from the loop footpoint in hot emission at 1MK, while sporadic downflows are seen in cool emission below 1MK. The upward motion in hot emission increases just after the cool downflows. The apparent propagating pattern suggests a hot upflow from the loop footpoints, and is considered to supply hot plasma into the coronal loop, but a wavelike phenomenon cannot be ruled out. Coronal condensation occasionally happens in the coronal loop, and the cool material flows down to the footpoint. Emission from cool plasma could have a significant contribution to hot AIA channels in the event of coronal condensation.
Landau's statistical mechanics for quasi-particle models

Landau's formalism of statistical mechanics [following L. D. Landau and E. M. Lifshitz, Statistical Physics (Pergamon Press, Oxford, 1980)] is applied to the quasi-particle model of quark–gluon plasma. Here, one starts from the expression for pressure and develop all thermodynamics. It is a general formalism and consistent with our earlier studies [V. M. Bannur, Phys. Lett. B647, 271 (2007)] based on Pathria's formalism [following R. K. Pathria, Statistical Mechanics (Butterworth-Heinemann, Oxford, 1977)]. In Pathria's formalism, one starts from the expression for energy density and develop thermodynamics. Both the formalisms are consistent with thermodynamics and statistical mechanics. Under certain conditions, which are wrongly called thermodynamic consistent relation, we recover other formalism of quasi-particle system, like in M. I. Gorenstein and S. N. Yang, Phys. Rev. D52, 5206 (1995), widely studied in quark–gluon plasma.
RED NUGGETS AT HIGH REDSHIFT: STRUCTURAL EVOLUTION OF QUIESCENT GALAXIES OVER 10 Gyr OF COSMIC HISTORY

We present an analysis of the size growth seen in early-type galaxies over 10 Gyr of cosmic time. Our analysis is based on a homogeneous synthesis of published data from 16 spectroscopic surveys observed at similar spatial resolution, augmented by new measurements for galaxies in the Gemini Deep Deep Survey. In total, our sample contains structural data for 465 galaxies (mainly early-type) in the redshift range 0.2 < z < 2.7. The size evolution of passively evolving galaxies over this redshift range is gradual and continuous, with no evidence for an end or change to the process around z ∼ 1, as has been hinted at by some surveys which analyze subsets of the data in isolation. The size growth appears to be independent of stellar mass, with the mass-normalized half-light radius scaling with redshift as Re∝(1 + z)−1.62 ± 0.34. Surprisingly, this power law seems to be in good agreement with the recently reported continuous size evolution of UV-bright galaxies in the redshift range z ∼ 0.5–3.5. It is also in accordance with the predictions from recent theoretical models.
Transport coefficients from the Nambu-Jona-Lasinio model for SU(3)f

We calculate the shear η(T) and bulk viscosities ζ(T) as well as the electric conductivity σe(T) and heat conductivity κ(T) within the Nambu-Jona-Lasinio (NJL) model for 3 flavors as a function of temperature as well as the entropy density s(T), pressure P(T) and speed of sound c2s(T). We compare the results with other models such as the Polyakov-Nambu-Jona-Lasinio (PNJL) model and the dynamical quasiparticle model (DQPM) and confront these results with lattice QCD data whenever available. This work is based on Ref. [1].
Broad iron emission line and kilohertz quasi-periodic oscillations in the neutron star system 4U 1636–53

Both the broad iron (Fe) line and the frequency of the kilohertz quasi-periodic oscillations (kHz QPOs) in neutron star low-mass X-ray binaries (LMXBs) can potentially provide independent measures of the inner radius of the accretion disc. We use XMM-Newton and simultaneous Rossi X-ray Timing Explorer observations of the LMXB 4U 1636-53 to test this hypothesis. We study the properties of the Fe Kα emission line as a function of the spectral state of the source and the frequency of the kHz QPOs. We find that the inner radius of the accretion disc deduced from the frequency of the upper kHz QPO varies as a function of the position of the source in the colour-colour diagram, in accordance with previous work and with the standard scenario of accretion disc geometry. On the contrary, the inner disc radius deduced from the profile of the iron line is not correlated with the spectral state of the source. The values of the inner radius inferred from kHz QPOs and iron lines, in four observations, do not lead to a consistent value of the neutron star mass, regardless of the model used to fit the iron line. Our results suggest that either the kHz QPO or the standard relativistic Fe line interpretation does not apply for this system. Furthermore, the simultaneous detection of kHz QPOs and broad iron lines is difficult to reconcile with models in which the broadening of the iron line is due to the reprocessing of photons in an outflowing wind.
The stellar metallicity distribution of the Milky Way from the Beijing-Arizona-Taiwan-Connecticut survey

Using the stellar atmospheric parameters such as effective temperature and metallicity derived from Sloan Digital Sky Survey spectra (SDSS) for ∼2200 main sequence (MS) stars which were also observed by Beijing–Arizona–Taiwan–Connecticut (BATC) photometric system, we develop the polynomial photometric calibration method to evaluate the stellar effective temperature and metallicity for BATC multicolour photometric data. This calibration method has been applied to about 160 000 MS stars from 67 BATC observed fields. Those stars have colours and magnitudes in the ranges 0.1 5 kpc which corresponds to the halo component and a peak at [Fe/H] ∼− 0.7 in the region 2 < |Z |≤ 5 kpc which is dominated by the thick disc stars. The mean stellar metallicity smoothly decreases from −0.65 to −0.78 in the interval 0.5 < |Z |≤ 2 kpc. Metallicity distributions in the halo and the thick disc seem invariant with the distance from the Galactic plane.
Recent results from T2K

The T2K long-baseline neutrino oscillation experiment has produced the first observation of $\nu_{e}$ appearance and the most precise measurement of the mixing angle $\theta_{23}$ from $6.57 \times 10^{20}$ protons-on-target (POT) of neutrino beam data. We present here the results of T2K antineutrino oscillation analyses searching for $\bar{\nu}_{e}$ appearance and measuring the dominant oscillation parameters for $\bar{\nu}_{\mu}$ disappearance, including the results from the T2K near detector fit. Using $4.01 \times 10^{20}$ POT of antineutrino beam data T2K measured $\sin^{2}(\bar{\theta}_{23}) = 0.45^{+0.29}_{-0.12}$ and $|\Delta \bar{m}^{2}_{32}| = 2.51\pm0.28 \times 10^{-3} (eV^{2})$, consistent with previous existing $\nu_{\mu}$ and $\bar{\nu}_{\mu}$ disappearance measurements. From the same dataset 3 $\bar{\nu}_{e}$ candidate events were selected at the far detector, which did not provide evidence either for or against the $\bar{\nu}_{e}$ appearance hypothesis.
INTERMEDIATE-AGE STELLAR POPULATIONS IN CLASSICAL QUASI-STELLAR OBJECT HOST GALAXIES

Although mergers and starbursts are often invoked in the discussion of quasi-stellar object (QSO) activity in the context of galaxy evolution, several studies have questioned their importance or even their presence in QSO host galaxies. Accordingly, we are conducting a study of z ∼ 0.2 QSO host galaxies previously classified as passively evolving elliptical galaxies. We present deep Keck/LRIS spectroscopy of a sample of 15 hosts and model their stellar absorption spectra using stellar synthesis models. The high signal-to-noise ratio of our spectra allows us to break various degeneracies that arise from different combinations of models, varying metallicities, and contamination from QSO light. We find that none of the host spectra can be modeled by purely old stellar populations and that the majority of the hosts (14/15) have a substantial contribution from intermediate-age populations with ages ranging from 0.7 to 2.4 Gyr. An average host spectrum is strikingly well fit by a combination of an old population and a 2.1 (+0.5, −0.7) Gyr population. The morphologies of the host galaxies suggest that these aging starbursts were induced during the early stages of the mergers that resulted in the elliptical-shaped galaxies that we observe. The current active galactic nucleus activity likely corresponds to the late episodes of accretion predicted by numerical simulations, which occur near the end of the mergers, whereas earlier episodes may be more difficult to observe due to obscuration. Our off-axis observations prevent us from detecting any current star formation or young stellar populations that may be present in the central few kiloparsecs.
Self-gravitating spheres of anisotropic fluid in geodesic flow

The fluid models mentioned in the title are classified. All characteristics of the fluid are expressed through a master potential, satisfying an ordinary second order differential equation. Different constraints are imposed on this core of relations, finding new solutions and deriving the classical results for perfect fluids and dust as particular cases. Many uncharged and charged anisotropic solutions, all conformally flat and some uniform density solutions are found. A number of solutions with linear equation among the two pressures are derived, including the case of vanishing tangential pressure.
Resistance of helical edges formed in a semiconductor heterostructure

Time-reversal symmetry prohibits elastic backscattering of electrons propagating within a helical edge of a two-dimensional topological insulator. However, small band gaps in these systems make them sensitive to doping disorder, which may lead to the formation of electron and hole puddles. Such a puddle -- a quantum dot -- tunnel-coupled to the edge may significantly enhance the inelastic backscattering rate, due to the long dwelling time of an electron in the dot. The added resistance is especially strong for dots carrying an odd number of electrons, due to the Kondo effect. For the same reason, the temperature dependence of the added resistance becomes rather weak. We present a detailed theory of the quantum dot effect on the helical edge resistance. It allows us to make specific predictions for possible future experiments with artificially prepared dots in topological insulators. It also provides a qualitative explanation of the resistance fluctuations observed in short HgTe quantum wells. In addition to the single-dot theory, we develop a statistical description of the helical edge resistivity introduced by random charge puddles in a long heterostructure carrying helical edge states. The presence of charge puddles in long samples may explain the observed coexistence of a high sample resistance with the propagation of electrons along the sample edges.
Adventures of a tidally induced bar

Using N-body simulations, we study the properties of a bar induced in a discy dwarf galaxy as a result of tidal interaction with the Milky Way. The bar forms at the first pericentre passage and survives until the end of the evolution at 10 Gyr. Fourier decomposition of the bar reveals that only even modes are significant and preserve a hierarchy so that the bar mode is always the strongest. They show a characteristic profile with a maximum, similar to simulated bars forming in isolated galaxies and observed bars in real galaxies. We adopt the maximum of the bar mode as a measure of the bar strength and we estimate the bar length by comparing the density profiles along the bar and perpendicular to it. The bar strength and the bar length decrease with time, mainly at pericentres, as a result of tidal torques acting at those times and not to secular evolution. The pattern speed of the bar varies significantly on a time-scale of 1 Gyr and is controlled by the orientation of the tidal torque from the Milky Way. The bar is never tidally locked, but we discover a hint of a 5/2 orbital resonance between the third and fourth pericentre passage. The speed of the bar decreases in the long run so that the bar changes from initially rather fast to slow in the later stages. The boxy/peanut shape is present for some time and its occurrence is preceded by a short period of buckling instability.
Transport properties of the Coulomb–Majorana junction

We provide a comprehensive theoretical description of low-energy quantum transport for a Coulomb–Majorana junction, where several helical Luttinger liquid nanowires are coupled to a joint mesoscopic superconductor with finite charging energy. Including the Majorana bound states formed near the ends of superconducting wire parts, we derive and analyze the Keldysh phase action describing non-equilibrium charge transport properties of the junction. The low-energy physics corresponds to a two-channel Kondo model with symmetry group SO(M), where M is the number of leads connected to the superconductor. Transport observables, such as the conductance tensor or current noise correlations, display non-trivial temperature or voltage dependences reflecting non-Fermi liquid behavior.
Superconducting gap structure of CeIrIn 5 from field-angle-resolved measurements of its specific heat

In order to identify the gap structure of CeIrIn${}_{5}$, we measured field-angle-resolved specific heat $C(\ensuremath{\varphi})$ by conically rotating the magnetic field $H$ around the $c$ axis at low temperatures down to 80 mK. We revealed that $C(\ensuremath{\varphi})$ exhibits a fourfold angular oscillation, whose amplitude decreases monotonically by tilting $H$ out of the $ab$ plane. Detailed microscopic calculations based on the quasiclassical Eilenberger equation confirm that the observed features are uniquely explained by assuming the ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$-wave gap. These results strongly indicate that CeIrIn${}_{5}$ is a ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$-wave superconductor and suggest the universal pairing mechanism in Ce$M$In${}_{5}$ ($M=\text{Co}$, Rh, and Ir).
Chemical Abundances in Star-Forming Galaxies at High Redshift

Abstract A galaxy's metallicity provides a record of star formation, gas accretion, and gas outflow, and is therefore one of the most informative measurements that can be made at high redshift. It is also one of the most difficult. I review methods of determining chemical abundances in distant star-forming galaxies, and summarize results for galaxies at 1 ≲ z ≲ 3. I then focus on the mass-metallicity relation, its evolution with redshift, and its uses in constraining inflows and outflows of gas, and conclude with a brief discussion of future prospects for metallicity measurements at high redshift.
Herschel-SPIRE Fourier transform spectroscopy of the nearby spiral galaxy IC 342

We present observations of the nearby spiral galaxy IC342 with the Herschel Spectral and Photometric Imaging Receiver (SPIRE) Fourier Transform Spectrometer. The spectral range afforded by SPIRE, 196-671 m, allows us to access a number of 12 CO lines from J=4‐3 to J=13‐12 with the highest J transitions observed for the first time. In addition we present measurements of 13 CO, [CI] and [NII]. We use a radiative transfer code coupled with Bayesian likelihood analysis to model and constrain the temperature, density and column density of the gas. We find two 12 CO components, one at 35 K and one at 400 K with CO column densities of 6.3 10 17 cm 2 and 0.4 10 17 cm 2 and CO gas masses of 1.26 10 7 M and 0.15 10 7 M , for the cold and warm components, respectively. The inclusion of the high-J 12 CO line observations, indicate the existence of a much warmer gas component ( 400 K) confirming earlier findings from H2 rotational line analysis from ISO and Spitzer. The mass of the warm gas is 10% of the cold gas, but it likely dominates the CO luminosity. In addition, we detect strong emission from [NII] 205 m and the 3 P1! 3 P0 and 3 P2! 3 P1 [CI] lines at 370 and 608 m, respectively. The measured 12 CO line ratios can be explained by Photon-dominated region (PDR) models although additional heating by e.g. cosmic rays cannot be excluded. The measured [CI] line ratio together with the derived [C] column density of 2.1 10 17 cm 2 and the fact that [CI] is weaker than CO emission in IC342 suggests that [CI] likely arises in a thin layer on the outside of the CO emitting molecular clouds consistent with PDRs playing an important role.
Astronomical relativistic reference systems with multipolar expansion: the global one

With the rapid development of techniques for astronomical observations, the precision of measurements has been significantly increasing. Theories describing astronomical relativistic reference systems, which are the foundation for processing and interpreting these data now and in the future, may require extensions to satisfy the needs of these trends. Besides building a framework compatible with alternative theories of gravity and the pursuit of higher order post-Newtonian approximation, it will also be necessary to make the first order post-Newtonian multipole moments of celestial bodies be explicitly expressed in the astronomical relativistic reference systems. This will bring some convenience into modeling the observations and experiments and make it easier to distinguish different contributions in measurements. As a first step, the global solar system reference system is expressed as a multipolar expansion and the post-Newtonian mass and spin moments are shown explicitly in the metric which describes the coordinates of the system. The full expression of the global metric is given.
Chemical evolution of the Galactic Centre

In recent years, the Galactic Centre (GC) region (200 pc in radius) has been studied in detail with spectroscopic stellar data as well as an estimate of the ongoing star formation rate. The aims of this paper are to study the chemical evolution of the GC region by means of a detailed chemical evolution model and to compare the results with high-resolution spectroscopic data in order to impose constraints on the GC formation history. The chemical evolution model assumes that the GC region formed by fast infall of gas and then follows the evolution of a-elements and Fe. We test different initialmass functions (IMFs), efficiencies of star formation and gas infall time-scales. To reproduce the currently observed star formation rate, we assume a late episode of star formation triggered by gas infall/accretion. We find that, in order to reproduce the [alpha/Fe] ratios as well as the metallicity distribution function observed in GC stars, the GC region should have experienced a main early strong burst of star formation, with a star formation efficiency as high as similar to 25 Gyr(-1), occurring on a time-scale in the range similar to 0.1-0.7 Gyr, in agreement with previous models of the entire bulge. Although the small amount of data prevents us from drawing firm conclusions, we suggest that the best IMF should contain more massive stars than expected in the solar vicinity, and the last episode of star formation, which lasted several hundred million years, should have been triggered by a modest episode of gas infall/accretion, with a star formation efficiency similar to that of the previous main star formation episode. This last episode of star formation produces negligible effects on the abundance patterns and can be due to accretion of gas induced by the bar. Our results exclude an important infall event as a trigger for the last starburst. (Less)