Miracle-dz/UniFAR-FTUs huggingface dataset:
Disk Galaxy Formation in a Λ Cold Dark Matter Universe

We describe hydrodynamic simulations of galaxy formation in a Λ cold dark matter cosmology, performed using a subresolution model for star formation and feedback in a multiphase interstellar medium (ISM). In particular, we demonstrate the formation of a well-resolved disk galaxy. The surface brightness profile of the galaxy is exponential, with a B-band central surface brightness of 21.0 mag arcsec-2 and a scale length of Rd = 2.0 h-1 kpc. We find no evidence for a significant bulge component. The simulated galaxy falls within the I-band Tully-Fisher relation, with an absolute magnitude of I = -21.2 and a peak stellar rotation velocity of Vrot = 121.3 km s-1. While the total specific angular momentum of the stars in the galaxy agrees with observations, the angular momentum in the inner regions appears to be low by a factor of ~2. The star formation rate of the galaxy peaks at ~7 M☉ yr-1 between redshifts z = 2 and 4, with the mean stellar age decreasing from ~10 Gyr in the outer regions of the disk to ~7.5 Gyr in the center, indicating that the disk did not simply form inside-out. The stars exhibit a metallicity gradient from 0.7 Z☉ at the edge of the disk to 1.3 Z☉ in the center. Using a suite of idealized galaxy formation simulations with different models for the ISM, we show that the effective pressure support provided by star formation and feedback in our multiphase model is instrumental in allowing the formation of large, stable disk galaxies. If ISM gas is instead modeled with an isothermal equation of state, or if star formation is suppressed entirely, growing gaseous disks quickly violate the Toomre stability criterion and undergo catastrophic fragmentation.
Neutrino masses in a conformal multi-Higgs-doublet model

We construct a conformal version of a general multi-Higgs-doublet model with additional right-handed neutrino gauge-singlets. Assuming a minimal extension of the scalar sector by a real singlet field, we show that the resulting model achieves the same attractive properties as the non-conformal theory, combining the seesaw mechanism and higher-order mass production to generate naturally light neutrino masses. Starting with dimensionless couplings only, all masses and energy scales in the theory (including the heavy Majorana masses and the electroweak scale) are obtained from dimensional transmutation via the Coleman-Weinberg mechanism. A characteristic feature of the conformal model is the appearance of the scalon in the scalar spectrum.The mass of this particle, which can be expressed in terms of the masses of the other particles in the theory, is produced at the one-loop level. We establish a connection between the large seesaw scale and a suppression of the scalon interactions. The positivity condition for the squared scalon mass requires sufficiently large masses of the additional Higgs bosons balancing the contributions of the heavy neutrinos.
On the Probability Density Function of Galactic Gas. I. Numerical Simulations and the Significance of the Polytropic Index

We investigate the form of the one-point probability density function (pdf) for the density field of the interstellar medium using numerical simulations that successively reduce the number of physical processes included. Two-dimensional simulations of self-gravitating supersonic MHD turbulence, of supersonic self-gravitating hydrodynamic turbulence, and of decaying Burgers turbulence produce in all cases filamentary density structures and evidence for a power-law density pdf at large densities with logarithmic slope between -1.7 and -2.3. This suggests that a power-law shape of the pdf and the general filamentary morphology are the signature of the nonlinear advection operator. These results do not support previous claims that the pdf is lognormal. A series of one-dimensional simulations of forced supersonic polytropic turbulence is used to resolve the discrepancy. They suggest that the pdf is lognormal only for effective polytropic indices γ = 1 (or nearly lognormal for γ ≠ 1 if the Mach number is sufficiently small), while power laws develop for densities larger than the mean if γ < 1. We evaluate the polytropic index for conditions relevant to the cool interstellar medium using published cooling functions and different heating sources, finding that a lognormal pdf should probably occur at densities around 103 and is possible at larger densities, depending strongly on the role of gas-grain heating and cooling. Several applications are examined. First, we question a recent derivation of the initial mass function from the density pdf by Padoan, Nordlund, & Jones because (1) the pdf does not contain spatial information and (2) their derivation produces the most massive stars in the voids of the density distribution. Second, we illustrate how a distribution of ambient densities can alter the predicted form of the size distribution of expanding shells. Finally, a brief comparison is made with the density pdfs found in cosmological simulations.
A Limit Relation between Black Hole Mass and Hβ Width: Testing Super-Eddington Accretion in Active Galactic Nuclei

We show that there is a limit relation between the black hole mass (MBH) and the width at half-maximum (υFWHM) of Hβ for active galactic nuclei (AGNs) with super-Eddington accretion rates. When a black hole has a super-Eddington accretion rate, the empirical relation derived from reverberation mapping can be applied in two possible ways. First, it reduces to a relation between the black hole mass and the size of the broad-line region because of photon-trapping effects inside the accretion disk. For the empirical reverberation relation of Kaspi et al., we obtain the limit relation MBH = (2.9–12.6) × 106 [vFWHM/(103 km s-1)]6.67M⊙, called the Eddington limit. Second, the Eddington limit luminosity will be relaxed if the trapped photons can escape from the magnetized super-Eddington accretion disk via the photon bubble instability, and the size of the broad-line region will be enlarged according to the empirical reverberation relation, leading to a relatively narrow Hβ width. We call this the Begelman limit. Using this limit relation, we searched 164 AGNs for super-Eddington accretion. We find that most of them are well confined by the Eddington limit relation—that is, most have sub-Eddington accretion rates—but there are a handful of objects located between the Eddington and Begelman limit lines; they may be candidate super-Eddington accretors in a hybrid structure of photon trapping and photon bubble instability. The maximum Hβ width is in the range (3.0–3.8) × 10 3 km s-1 for the most massive black holes with super-Eddington accretion rates among AGNs. We suggest that the FWHM(Hβ)-MBH relation is a reliable and convenient method to test whether a source is super-Eddington and useful to probe the structure of the super-Eddington accretion process.
The dependence of halo bias on age, concentration, and spin

Halo bias is the main link between the matter distribution and dark matter halos. In its simplest form, halo bias is determined by halo mass, but there are known additional dependencies on other halo properties which are of consequence for accurate modeling of galaxy clustering. Here we present the most precise measurement of these secondary-bias dependencies on halo age, concentration, and spin, for a wide range of halo masses spanning from 10$^{10.7}$ to 10$^{14.7}$ $h^{-1}$ M$_{\odot}$. At the high-mass end, we find no strong evidence of assembly bias for masses above M$_{vir}$ $\sim10^{14}$ $h^{-1}$ M$_{\odot}$. Secondary bias exists, however, for halo concentration and spin, up to cluster-size halos, in agreement with previous findings. For halo spin, we report, for the first time, two different regimes: above M$_{vir}\sim$10$^{11.5}$ $h^{-1}$ M$_{\odot}$, halos with larger values of spin have larger bias, at fixed mass, with the effect reaching almost a factor 2. This trend reverses below this characteristic mass. In addition to these results, we test, for the first time, the performance of a multi-tracer method for the determination of the relative bias between different subsets of halos. We show that this method increases significantly the signal-to-noise of the secondary-bias measurement as compared to a traditional approach. This analysis serves as the basis for follow-up applications of our multi-tracer method to real data.
An emulator for the Lyman-α forest

We present methods for interpolating between the 1-D flux power spectrum of the Lyman-α forest, as output by cosmological hydrodynamic simulations. Interpolation is necessary for cosmological parameter estimation due to the limited number of simulations possible. We construct an emulator for the \Lya forest flux power spectrum from 21 small simulations using Latin hypercube sampling and Gaussian process interpolation. We show that this emulator has a typical accuracy of 1.5% and a worst-case accuracy of 4%, which compares well to the current statistical error of 3–5% at z < 3 from BOSS DR9. We compare to the previous state of the art, quadratic polynomial interpolation. The Latin hypercube samples the entire volume of parameter space, while quadratic polynomial emulation samples only lower-dimensional subspaces. The Gaussian process provides an estimate of the emulation error and we show using test simulations that this estimate is reasonable. We construct a likelihood function and use it to show that the posterior constraints generated using the emulator are unbiased. We show that our Gaussian process emulator has lower emulation error than quadratic polynomial interpolation and thus produces tighter posterior confidence intervals, which will be essential for future Lyman-α surveys such as DESI.
Adaptive Two Stage Designs and the Conditional Error Function

Proschan and Hunsberger (1995) suggest the use of a conditional error function to construct a two stage test that meets the α level and allows a very flexible reassessment of the sample size after the interim analysis. In this note we show that several adaptive designs can be formulated in terms of such an error function. The conditional power function defined similarly provides a simple method for sample size reassessment in adaptive two stage designs.
Relativistic O VIII Emission and Ionized Outflow in NGC 4051 Measured with XMM-Newton

We present XMM-Newton Reflection Grating Spectrometer observations of the soft X-ray spectrum of NGC 4051 and explore their implications for the inner accretion disk and ionized outflow in the active galactic nucleus. We fit the soft X-ray excess with a relativistically broadened O VIII recombination spectrum, including the entire line series and recombination continuum. This plus an underlying power-law continuum provides a much better fit to the soft X-ray spectrum than a single temperature or disk blackbody plus power law. The emission-line profiles, computed for a Kerr metric around a maximally rotating black hole, reveal a sharply peaked disk emissivity law and inner radius smaller than 1.7RG. The spectrum also includes narrow absorption and emission lines from C, N, O, Ne, and Fe in an ionized outflow. Outflow column densities are relatively low and do not create significant edges in the spectrum. The small amount of absorption bolsters confidence in the detection of relativistic emission-line features. The narrow-line emitter has a large (76%) global covering fraction, leading to strong forbidden lines and filling in of the resonance absorption lines. We also find broad C VI Lyα and very broad O VII emission from the broad-line region. The narrow- and broad-line regions span large ranges in ionization parameter and may arise in a disk outflow. The ionized absorber has a large ionization range, which is inconsistent with pressure equilibrium in a multiphase medium. The mass outflow rate exceeds the accretion rate by a factor of 1000.
Lyman Alpha Constraints on Very Low Luminosity AGN

Recent surveys have detected Lya emission from z=4.5-6.5 at luminosities as low as 10^41 erg/s. There is good evidence that low numbers of AGN are among observed faint Lya emitters. Combining these observations with an empirical relation between the intrinsic Lya and B-band luminosities of AGN, we obtain an upper limit on the number density of AGN with absolute magnitudes M_B=[-16,-19] at z=4.5-6.5. These AGN are up to two orders of magnitude fainter than those discovered in the Chandra Deep Field, resulting in the faintest observational constraints to date at these redshifts. At z=4.5, the powerlaw slope of the very faint end of the luminosity function of AGN is shallower than the slope observed at lower redshifts, beta -20 is lower than expected from the M_BH-sigma relation by one-two orders of magnitude. Extrapolating from reverberation-mapping studies suggests that these black holes would have M_BH=10^6-10^7 Msun. To facilitate the identification of AGN among observed Lya emitters, we derive observational properties of faint AGN in the Lya line, as well as in the X-ray and optical bands.
Line-driven disc wind in near-Eddington active galactic nuclei: decrease of mass accretion rate due to powerful outflow

Based on recent X-ray observations, ultrafast outflows from supermassive black holes are expected to have enough energy to dramatically affect their host galaxy but their launch and acceleration mechanisms are not well understood. We perform two-dimensional radiation hydrodynamics simulations of UV line-driven disc winds in order to calculate the mass-loss rates and kinetic power in these models. We develop a new iterative technique that reduces the mass accretion rate through the inner disc in response to the wind mass-loss. This makes the inner disc less UV bright, reducing the wind power compared to previous simulations which assumed a constant accretion rate with radius. The line-driven winds in our simulations are still extremely powerful, with around half the supplied mass accretion rate being ejected in the wind for black holes with mass 108–$10^{10}\, \mathrm{ M}_\odot$ accreting at L/LEdd = 0.5–0.9. Our results open up the way for estimating the growth rate of supermassive black hole and evaluating the kinetic energy ejected into the interstellar medium (active galactic nuclei feedback) based on a physical model of line-driven disc winds.
Superconducting pairing in Sr 2 RuO 4 from weak to intermediate coupling

The unconventional superconductivity in Sr$_2$RuO$_4$ continues to attract considerable interest. While many measurements can be interpreted on the basis of chiral $p$-wave pairing with intriguing topological character, a number of exceptions hinder an unambiguous verification of such pairing. The pairing mechanism also remains under debate. In this paper, with effects of the sizable spin-orbit coupling accounted for, we reexamine the superconducting instabilities in Sr$_2$RuO$_4$ through systematic microscopic analysis within random phase approximation. Our calculations show that the odd-parity $p$-wave pairing is favored in the regime of extremely weak interactions, but that highly anisotropic even-parity pairings become most leading over a broad range of stronger interactions. These results could shed light on the nature of the enigmatic superconductivity in Sr$_2$RuO$_4$.
Physical Properties of Large-scale Galactic Filaments

The characterization of our Galaxy’s longest filamentary gas features has been the subject of several studies in recent years, producing not only a sizable sample of large-scale filaments, but also confusion as to whether all these features (e.g., “Bones,” “Giant Molecular Filaments”) are the same. They are not. We undertake the first standardized analysis of the physical properties (H2 column densities, dust temperatures, morphologies, radial column density profiles) and kinematics of large-scale filaments in the literature. We expand and improve upon prior analyses by using the same data sets, techniques, and spiral arm models to disentangle the filaments’ inherent properties from selection criteria and methodology. Our results suggest that the myriad filament-finding techniques are uncovering different physical structures, with length (11–269 pc), width (1–40 pc), mass ( ), aspect ratio (3:1–117:1), and high column density fraction (0.2%–100%) varying by over an order of magnitude across the sample of 45 filaments. We develop a radial profile-fitting code, RadFil, which is publicly available. We also perform a position–position–velocity (p–p–v) analysis on a subsample and find that while 60%–70% lie spatially in the plane of the Galaxy, only 30%–45% concurrently exhibit spatial and kinematic proximity to spiral arms. In a parameter space defined by aspect ratio, dust temperature, and column density, we broadly distinguish three filament categories, which could indicate different formation mechanisms or histories. Highly elongated “Bone-like” filaments show the most potential for tracing gross spiral structure (e.g., arms, spurs), while other categories could be large concentrations of molecular gas (giant molecular clouds, core complexes).
An Accurate Physical Model for Halo Concentrations

The relation between halo mass, M, and concentration, c, is a critical component in our understanding of the structure of dark matter halos. While numerous models for this relation have been proposed, almost none of them attempt to derive the evolution of the relation analytically. We build on previous efforts to model the c–M relation as a function of physical parameters such as the peak height, ν, and the effective power spectrum slope, , which capture the dependence of c on halo mass, redshift, and cosmology. We present three major improvements over previous models. First, we derive an analytical expression for the c–M relation that is valid under the assumption of pseudo-evolution, i.e., assuming that the density profiles of halos are static in physical coordinates while the definition of their boundary evolves. We find that this ansatz is highly successful in describing the evolution of the low-mass end of the c–M relation. Second, we employ a new physical variable, the effective exponent of linear growth, , to parameterize deviations from an Einstein–de Sitter expansion history. Third, we combine an updated definition of with the additional dependence on and propose a phenomenological extension of our analytical framework to include all halo masses. This semianalytical model matches simulated concentrations in both scale-free models and ΛCDM to 5% accuracy with very few exceptions and differs significantly from all previously proposed models. We present a publicly available code to compute the predictions of our model in the python toolkit Colossus, including updated parameters for the model of Diemer and Kravtsov.
Optimal tracking performance of MIMO discrete‐time systems with communication constraints

The optimal tracking problem for multiple‐input multiple‐output linear‐time‐invariant discrete‐time systems with communication constraints in the feedback path is studied in this paper. The tracking performance is measured by the energy of the error signal between the output of the plant and the reference signal. The objective is to obtain an optimal tracking performance, attainable by all possible stabilizing compensators. It is shown that the optimal tracking performance consists of two parts, one depends on the nonminimum phase zeros and zero direction of the given plant, as well as the reference input signal direction, and the other depends on the nonminimum phase zeros, unstable poles, and pole direction of the given plant, as well as the bandwidth and additive white Gaussian noise of the communication channel. It is also shown that, if the constraint of the communication channel does not exist, the optimal tracking performance reduces to the existing tracking performance of the control system without communication constraints. A typical example is given to illustrate the theoretical results. Copyright © 2011 John Wiley & Sons, Ltd.
Spin-based all-optical quantum computation with quantum dots: Understanding and suppressing decoherence

We present an all-optical implementation of quantum computation using semiconductor quantum dots. Quantum memory is represented by the spin of an excess electron stored in each dot. Two-qubit gates are realized by switching on trion-trion interactions between different dots. State selectivity is achieved via conditional laser excitation exploiting Pauli exclusion principle. Read out is performed via a quantum-jump technique. We analyze the effect on our scheme's performance of the main imperfections present in real quantum dots: exciton decay, hole mixing, and phonon decoherence. We introduce an adiabatic gate procedure that allows one to circumvent these effects and evaluate quantitatively its fidelity.
Discrete breathers in classical spin lattices.

Discrete breathers ~nonlinear localized modes! have been shown to exist in various nonlinear Hamiltonian lattice systems. In the present paper, we study the dynamics of classical spins interacting via the Heisenberg exchange on spatial d-dimensional lattices ~with and without presence of single-ion anisotropy! We show that discrete breathers exist for the cases when the continuum theory does not allow for their presence ~easy-axis ferromagnets with anisotropic exchange and easy-plane ferromagnets! We prove the existence of localized excitations, using the implicit function theorem, and obtain necessary conditions for this existence. The most interesting case is the easy-plane one, which yields excitations with locally tilted magnetization. There is no continuum analog for such a solution and there exists an energy threshold for it, which is estimated analytically. We support our analytical results with numerical high-precision computations, including also a stability analysis for the excitations.
ORFEUS II Far-Ultraviolet Observations of 3C 273: Interstellar and Intergalactic Absorption Lines

We present the first intermediate-resolution (λ/Δλ = 3000) spectrum of the bright quasi-stellar object 3C 273 at wavelengths between 900 and 1200 Å. Observations were performed with the Berkeley spectrograph aboard the ORFEUS II mission. We detect Lyβ counterparts to intergalactic Lyα features identified by Morris and coworkers at cz = 19,900, 1600, and 1000 km s−1; counterparts to other putative Lyα clouds along the sight line are below our detection limit. The strengths of the two very low redshift Lyβ features, which are believed to arise in Virgo intracluster gas, exceed preflight expectations (Weymann and coworkers), suggesting that the previous determination of the cloud parameters may underestimate the true column densities. A curve-of-growth analysis sets a minimum H I column density of 4 × 1014 cm−2 for the 1600 km s−1 cloud. We find marginally significant evidence for Galactic H2 along the sight line, with a total column density of about 1015 cm−2. We detect the stronger interstellar O VI doublet member unambiguously; the weaker member is blended with other features. If the Doppler b-value for O VI is comparable to that determined for N V by Sembach and collaborators, then the O VI column density is (7 ± 2) × 1014 cm−2, significantly above the only previous estimate, by Davidsen. The O VI/N V ratio is about 10, consistent with the low end of the range observed in the disk, as shown in the compilation by Hurwitz & Bowyer. Additional interstellar species detected for the first time toward 3C 273 (at modest statistical significance) include P II, Fe III, Ar I, and S III.