Miracle-dz/UniFAR-FTUs huggingface dataset:
Nonlinear structure formation in the cubic Galileon gravity model

We model the linear and nonlinear growth of large scale structure in the Cubic Galileon gravity model, by running a suite of N-body cosmological simulations using the ECOSMOG code. Our simulations include the Vainshtein screening effect, which reconciles the Cubic Galileon model with local tests of gravity. In the linear regime, the amplitude of the matter power spectrum increases by ~ 20% with respect to the standard ΛCDM model today. The modified expansion rate accounts for ~ 15% of this enhancement, while the fifth force is responsible for only ~ 5%. This is because the effective unscreened gravitational strength deviates from standard gravity only at late times, even though it can be twice as large today. In the nonlinear regime (k0.1h Mpc−1), the fifth force leads to only a modest increase (8%) in the clustering power on all scales due to the very efficient operation of the Vainshtein mechanism. Such a strong effect is typically not seen in other models with the same screening mechanism. The screening also results in the fifth force increasing the number density of halos by less than 10%, on all mass scales. Our results show that the screening does not ruin the validity of linear theory on large scales which anticipates very strong constraints from galaxy clustering data. We also show that, whilst the model gives an excellent match to CMB data on small angular scales (l50), the predicted integrated Sachs-Wolfe effect is in tension with Planck/WMAP results.
THE EFFECT OF HALO MASS ON THE H i CONTENT OF GALAXIES IN GROUPS AND CLUSTERS

We combine data from the Sloan Digital Sky Survey (SDSS) and the Arecibo Legacy Fast ALFA Survey (ALFALFA) to study the cold atomic gas content of galaxies in groups and clusters in the local universe. A careful cross-matching of galaxies in the SDSS, ALFALFA, and SDSS group catalogs provides a sample of group galaxies with stellar masses 10 8.4 M ⊙ ≤ M * ≤ 10 10.6 M ⊙ ? > and group halo masses 10 12.5 h − 1 M ⊙ ≤ M h ≤ 10 15.0 h − 1 M ⊙ ? > . Controlling our sample in stellar mass and redshift, we find no significant radial variation in the galaxy H i gas-to-stellar mass ratio for the halo mass range in our sample. However, the fraction of galaxies detected in ALFALFA declines steadily toward the centers of groups, with the effect being most prominent in the most massive halos. In the outskirts of massive halos a hint of a depressed detection fraction for low-mass galaxies suggests pre-processing that decreases the H i in these galaxies before they fall into massive clusters. We interpret the decline in the ALFALFA detection of galaxies in the context of a threshold halo mass for ram pressure stripping for a given galaxy stellar mass. The lack of an observable decrease in the galaxy H i gas-to-stellar mass ratio with the position of galaxies within groups and clusters highlights the difficulty of detecting the impact of environment on the galaxy H i content in a shallow H i survey.
Thermonuclear X-ray bursts from the 401-Hz accreting pulsar IGR J17498−2921: indication of burning in confined regions

We use the 2011 Rossi X-ray Timing Explorer (RXTE) Proportional Counter Array (PCA) data of the 401-Hz accreting pulsar and burster IGR J17498−2921 to perform timing analysis and time-resolved spectroscopy of 12 thermonuclear X-ray bursts. We confirm previously reported burst oscillations from this source with a much higher significance (8.8σ ). We note that the bursts can be divided into three groups: big photospheric radius expansion (PRE) bursts are about 10 times more luminous than medium bursts, while the latter are about 10 times more luminous than small bursts. The PCA field of view of these observations contains several known bursters, and hence some of the observed bursts might not be from IGR J17498−2921. The oscillations during big bursts at the known pulsar frequency show that these bursts were definitely from IGR J17498−2921. We find that at least several of the other bursts were also likely originated from IGR J17498−2921. Spectral analysis reveals that the luminosity differences among various bursts are primarily due to differences in normalizations, and not temperatures, even when we consider the effects of colour factor. This shows burning on a fraction of the stellar surface for those small and medium bursts, which originated from IGR J17498−2921. The low values of the upper limits of burst oscillation amplitude for these bursts suggest a small angle between the spin axis and the magnetic axis. We find indications of the PRE nature of a medium burst, which likely originated from IGR J17498−2921. If true, then, to the best of our knowledge, this is the first time that two PRE bursts with a peak count rate ratio of as high as ≈12 have been detected from the same source.
Comparison of Limb-Darkening Laws from Plane-Parallel and Spherically-Symmetric Model Stellar Atmospheres

Abstract Limb-darkening is a fundamental constraint for modeling eclipsing binary and planetary transit light curves. As observations, for example from Kepler, CoRot, and Most, become more precise then a greater understanding of limb-darkening is necessary. However, limb-darkening is typically modeled as simple parameterizations fit to plane-parallel model stellar atmospheres that ignores stellar atmospheric extension. In this work, I compute linear, quadratic and four-parameter limb-darkening laws from grids of plane-parallel and spherically-symmetric model stellar atmospheres in a temperature and gravity range representing stars evolving on the Red Giant branch. The limb-darkening relations for each geometry are compared and are found to fit plane-parallel models much better than the spherically-symmetric models. Assuming that limb-darkening from spherically-symmetry model atmospheres are more physically representative of actual stellar limb-darkening than plane-parallel models, then these limb-darkening laws will not fit the limb of a stellar disk leading to errors in a light curve fit. This error will increase with a star's atmospheric extension.
Short note on gravity with tensor auxiliary fields

We consider gravity coupled to a second metric in the strong coupling limit, where the second kinetic term is absent. This system belongs to the recently discussed class of models of "gravity with auxiliary fields" by Pani et al. We prove that, in vacuum, these theories are always equivalent to GR with a cosmological constant, even in the case where the auxiliary field equations contain identities leaving undetermined functions. In the situation where some functions are undetermined, the actual value of the cosmological constant is dictated by an initial condition, and not by the parameters in the action.
The Stagger-grid: A grid of 3D stellar atmosphere models - III. The relation to mixing length convection theory

Aims. We investigate the relation between 1D atmosphere models that rely on the mixing length theory and models based on full 3D radiative hydrodynamic (RHD) calculations to describe convection in the envelopes of late-type stars. Methods. The adiabatic entropy value of the deep convection zone, sbot, and the entropy jump, Δs, determined from the 3D RHD models, were matched with the mixing length parameter, αMLT, from 1D hydrostatic atmosphere models with identical microphysics (opacities and equation-of-state). We also derived the mass mixing length parameter, αm, and the vertical correlation length of the vertical velocity, C vz ,v z , directly from the 3D hydrodynamical simulations of stellar subsurface convection. Results. The calibrated mixing length parameter for the Sun is α �T (sbot) = 1.98. For different stellar parameters, αMLT varies systematically in the range of 1.7−2.4. In particular, αMLT decreases towards higher effective temperature, lower surface gravity and higher metallicity. We find equivalent results for α �T (Δs). In addition, we find a tight correlation between the mixing length parameter and the inverse entropy jump. We derive an analytical expression from the hydrodynamic mean-field equations that motivates the relation to the mass mixing length parameter, αm, and find that it qualitatively shows a similar variation with stellar parameter (between 1.6 and 2.4) with the solar value of α � = 1.83. The vertical correlation length scaled with the pressure scale height yields 1.71 for the Sun, but only displays a small systematic variation with stellar parameters, the correlation length slightly increases with Teff. Conclusions. We derive mixing length parameters for various stellar parameters that can be used to replace a constant value. Within any convective envelope, αm and related quantities vary strongly. Our results will help to replace a constant αMLT.
Schwinger-Dyson equations in large-N quantum field theories and nonlinear random processes

We propose a stochastic method for solving Schwinger-Dyson equations in large-N quantum field theories. Expectation values of single-trace operators are sampled by stationary probability distributions of the so-called nonlinear random processes. The set of all the histories of such processes corresponds to the set of all planar diagrams in the perturbative expansions of the expectation values of singlet operators. We illustrate the method on examples of the matrix-valued scalar field theory and the Weingarten model of random planar surfaces on the lattice. For theories with compact field variables, such as sigma models or non-Abelian lattice gauge theories, the method does not converge in the physically most interesting weak-coupling limit. In this case one can absorb the divergences into a self-consistent redefinition of expansion parameters. A stochastic solution of the self-consistency conditions can be implemented as a 'memory' of the random process, so that some parameters of the process are estimated from its previous history. We illustrate this idea on the two-dimensional O(N) sigma model. The extension to non-Abelian lattice gauge theories is discussed.
Test item response time and the response likelihood

Test takers do not give equally reliable responses. They take different responding strategies and they do not make the same effort to solve the problem and answer the question correctly. The consequences of differential test takers' behavior are numerous: the test item parameters could be biased, there might emerge differential item functioning for certain subgroups, estimation of test taker's ability might have greater error, etc. All the consequences are becoming more prominent at low-stakes tests where test takers' motivation is additionally decreased. We had analyzed a computer based test in Physics and tried to find and describe relationship between the item response time and the item response likelihood. We have found that magnitude of such relationship depends on the item difficulty parameter. We have also noticed that boys, who respond faster, in average, give responses with greater likelihood than the boys who respond slower. The same trend was not detected for girls.
Properties of star-forming galaxies in a cluster and its surrounding structure at z=1.46

We conduct a wide-field narrow-band imaging survey of [O ii] emitters in and around the XMMXCS J2215.9−1738 cluster at z= 1.46 with Subaru/Suprime-Cam. In a 32 × 23 arcmin2 area, we select 380 [O ii] emitting galaxies down to 1.4 × 10−17 erg s−1 cm−2. Among them, 16 [O ii] emitters in the central region of the cluster are confirmed by near-infrared spectroscopy with Subaru/MOIRCS, suggesting that our photometric selection is valid for sample [O ii] emitters at z= 1.46. We find that [O ii] emitters are distributed along filamentary large-scale structures around the cluster, which are among the largest structures of star-forming galaxies ever identified at 1.3 ≲z≲ 3.0. We define several environments such as cluster core, outskirts, filament and field in order to investigate the environment dependence of star-forming galaxies at z= 1.46. The colour–magnitude diagram of z′−K versus K for the [O ii] emitting galaxies shows that a significantly higher fraction of [O ii] emitters with red z′−K colours is seen in the cluster core than in other environments. It seems that the environment that hosts such red star-forming galaxies shifts from the core region at z= 1.46 to the outskirts of clusters at lower redshifts. A multicolour analysis of the red emitters indicates that these galaxies are more like nearly passively evolving galaxies which host [O ii] emitting active galactic nuclei (AGNs), rather than dust-reddened star-forming [O ii] emitters. We argue therefore that AGN feedback may be one of the critical processes to quench star formation in massive galaxies in high-density regions. The emission line ratios of [O iii]/Hβ and [N ii]/Hα of the [O ii] emitters in the cluster core support the inference that there is a moderate contribution of AGN to the emitters. We also find that the cluster has experienced high star formation activities at rates comparable to that in the field at z= 1.46 in contrast to lower redshift clusters, and that star formation activity in galaxy clusters on average increases with redshift up to z= 1.46. In addition, line ratios of [N ii]/Hα and [O iii]/Hβ indicate that a mass–metallicity relation exists in the cluster at z= 1.46, which is similar to that of star-forming galaxies in the field at z∼ 2. These results all suggest that at z∼ 1.5 star formation activity in the cluster core becomes as high as those in low-density environments and that there is apparently not yet a strong environmental dependence, except for the red emitters.
Embryo impacts and gas giant mergers – II. Diversity of hot Jupiters’ internal structure

We consider the origin of compact, short-period, Jupiter-mass planets. We propose that their diverse structure is caused by giant impacts of embryos and super-Earths or mergers with other gas giants during the formation and evolution of these hot Jupiters. Through a series of numerical simulations, we show that typical head-on collisions generally lead to total coalescence of impinging gas giants. Although extremely energetic collisions can disintegrate the envelope of gas giants, these events seldom occur. During oblique and moderately energetic collisions, the merger products retain higher fraction of the colliders' cores than their envelopes. They can also deposit considerable amount of spin angular momentum to the gas giants and desynchronize their spins from their orbital mean motion. We find that the oblateness of gas giants can be used to infer the impact history. Subsequent dissipation of stellar tide inside the planets' envelope can lead to runaway inflation and potentially a substantial loss of gas through Roche-lobe overflow. The impact of super-Earths on parabolic orbits can also enlarge gas giant planets' envelope and elevates their tidal dissipation rate over $\sim $ 100 Myr time scale. Since giant impacts occur stochastically with a range of impactor sizes and energies, their diverse outcomes may account for the dispersion in the mass-radius relationship of hot Jupiters.
Double-Peaked Profiles: Ubiquitous Signatures of Disks in the Broad Emission Lines of Active Galactic Nuclei

Broad (∼10,000 km s−1), double-peaked emission-line profiles of Balmer lines emitted by active galactic nuclei (AGN) are thought to originate in the outer parts of an accretion disk surrounding a nuclear supermassive black hole (SMBH), at ∼1000 gravitational radii, and are most frequently observed in the nuclear spectra of low-luminosity AGN (LLAGN) and radio galaxies. In the present paper we argue that broad double-peaked profiles are present also in the spectra of other type 1 AGN, such as Seyfert 1 galaxies, suggesting that the inner part of the broad-line region (BLR) is also the outer part of the accretion disk. We use the Palomar spectral survey of nearby galaxies to show that the only difference between Seyfert 1 BLR line profiles and “bona fide” double-peakers is that, in most cases, besides a disk component, we need an additional Gaussian component attributed to nondisk clouds. The recognition that the inner and most variable part of the BLR has a disk geometry suggests that the factor f in the expression to obtain the SMBH mass in type 1 AGN, , is for the disk-dominated sources. Our median i = 27° implies f = 4.5, very close to the most recent value of f = 4.3 ± 1.05, obtained from independent studies. We derive a relation between f and the FWHM of the broad profile that may help to reduce the uncertainties in the SMBH mass determinations of AGN.
Theoretical lower limits on sizes of ultrafaint dwarf galaxies from dynamical friction

Dwarf spheroidal galaxies are the smallest known stellar systems where under Newtonian interpretations, a significant amount of dark matter is required to explain observed kinematics. In fact, they are in this sense the most heavily dark matter dominated objects known. That, plus the increasingly small sizes of the newly discovered ultra faint dwarfs, puts these systems in the regime where dynamical friction on individual stars starts to become relevant. We calculate the dynamical friction timescales for pressure supported isotropic spherical dark matter dominated stellar systems, yielding $\tau_{DF} =0.93 (r_{h}/10 pc)^{2} (\sigma/ kms^{-1}) Gyr$, { where $r_{h}$ is the half-light radius}. For a stellar velocity dispersion value of $3 km/s$, as typical for the smallest of the recently detected ultra faint dwarf spheroidals, dynamical friction timescales becomes smaller than the $10 Gyr$ typical of the stellar ages for these systems, for $r_{h}<19 pc$. Thus, this becomes a theoretical lower limit below which dark matter dominated stellar systems become unstable to dynamical friction. We present a comparison with structural parameters of the smallest ultra faint dwarf spheroidals known, showing that these are already close to the stability limit derived, any future detection of yet smaller such systems would be inconsistent with a particle dark matter hypothesis.
HIGH-LATITUDE, TRANSLUSCENT MOLECULAR CLOUDS AS PROBES OF LOCAL COSMIC RAYS

We analyze the gamma ray emission from nine high latitude, translucent molecular clouds taken with the Fermi Large Area Telescope between 250 MeV and 10 GeV. Observations of gamma rays allow us to probe the density and spectrum of cosmic rays in the solar neighborhood. The clouds studied lie within ∼270 pc from the Sun and are selected from the Planck all-sky CO map. Gamma rays in this energy range mostly result from cosmic-ray interactions with the interstellar medium, which is traced with three components: H i, CO, and dark gas. Every cloud is detected and shows significant, extended gamma ray emission from molecular gas. The gamma ray emission is dominated by the CO-emitting gas in some clouds, but by the CO-dark gas in others. The average emissivity and gamma ray power law index from H i above 1 GeV shows no evidence of a systematic variation. The CO-to- H 2 ? > conversion factor shows no variation between clouds over this small spatial range, but shows significant variations within each cloud. The average CO-to- H 2 ? > conversion factor suggests that the CO-dark gas is molecular as opposed to optically thick H i.
Stable branched electron flow

The pattern of branched electron flow revealed by scanning gate microscopy shows the distribution of ballistic electron trajectories. The details of the pattern are determined by the correlated potential of remote dopants with an amplitude far below the Fermi energy. We find that the pattern persists even if the electron density is significantly reduced such that the change in Fermi energy exceeds the background potential amplitude. The branch pattern is robust against changes in charge carrier density, but not against changes in the background potential caused by additional illumination of the sample.
Thomson backscattering diagnostics of nanosecond electron bunches in high space charge regime

The intra-beam repulsions play a significant role in determining the performances of free-electron devices when an high brilliance of the beam is required. The transversal and longitudinal spread of the beam, its energy and density are fundamental parameters in any beam experiment and different beam diagnostics are available to measure such parameters. A diagnostic method based on the Thomson backscattering of a laser beam impinging on the particle beam is proposed in this work for the study of nanosecond electron bunches in high space charge regime. This diagnostics, aimed to the measurement of density, energy and energy spread, was set-up in a Malmberg-Penning trap (generally used for the electron/ion confinment) in two different configurations designed to optimize sensitivity, spatial resolution and electron-beam coincidence in space and time. To this purpose an electron bunch (pulse time <4ns), produced by a photocathode source, was preliminary characterized with different electrostatic diagnostics and used to test the diagnostics systems. The solutions are detailed, which were devised for both the laser and bunch injection in the vacuum chamber, space and time coincidence of electron and laser pulses, photon detection, optimization of the geometry in the laser-beam interaction. The results are then summarized with an estimate of the minimum sensitivity of the set-up.
Mass-loss rates and the mass evolution of star clusters

We describe the interplay between stellar evolution and dynamical mass loss of evolving star clusters, based on the principles of stellar evolution and cluster dynamics and on the details of a grid of N-body simulations of Galactic cluster models. The cluster models have different initial masses, different orbits, including elliptical ones, and different initial density profiles. We use two sets of cluster models: one set of Roche lobe filling models and a new set of cluster models that are initially underfilling their tidal radius. We identify four distinct mass-loss effects: (1) mass loss by stellar evolution, (2) loss of stars induced by stellar evolution and (3) relaxation-driven mass loss before and (4) after core collapse. At young ages the mass loss is dominated by stellar evolution, followed by the evolution-induced loss of stars. This evolution-induced mass loss is important if a cluster is immersed in the tidal field. Both the evolution-induced loss of stars and the relaxation-driven mass loss need time to build up. This is described by a delay function that has a characteristic time-scale of a few crossing times for Roche lobe filling clusters and a few half-mass relaxation times for initially Roche lobe underfilling clusters. The relaxation-driven mass loss (called ‘dissolution’ in this paper) can be described by a simple power-law dependence of the mass d(M/M )/dt = −(M/M )1−γ /t0, where t0 depends on the orbit and environment of the cluster. The index γ is 0.65 for clusters with a King parameter W0 = 5 for the initial density distribution, and 0.80 for more concentrated clusters with W0 = 7. For initially Roche lobe underfilling clusters the dissolution is described by the same γ =0.80, independent of the initial density distribution. The values of the constant t0 are derived for the models and described by simple formulae that depend on the orbit of the cluster. The mass-loss rate increases by about a factor of 2 at core collapse and the mass dependence of the relaxation-driven mass loss changes to γ = 0.70 after core collapse. We also present a simple recipe for predicting the mass evolution of individual star clusters with various metallicities and in different environments, with an accuracy of a few per cent in most cases. This can be used to predict the mass evolution of cluster systems.