ShantanuT01/DACTYL-Pretraining huggingface dataset:
We present VLT/VIMOS IFU observations of an occulting galaxy pair previously discovered in HST observations. The foreground galaxy is a low-inclination spiral disk, which causes clear attenuation features seen against the bright bulge and disk of the background galaxy. We find redshifts of $z=0.064 \pm0.003$ and z=0.065 for the foreground and background galaxy respectively. This relatively small difference does not rule out gravitational interaction between the two galaxies. Emission line ratios point to a star-forming, not AGN-dominated foreground galaxy.   We fit the Cardelli, Clayton & Mathis (CCM) extinction law to the spectra of individual fibres to derive slope ($R_V$) and normalization ($A_V$). The normalization agrees with the HST attenuation map and the slope is lower than the Milky Way relation ($R_V<3.1$), which is likely linked to the spatial sampling of the disk. We speculate that the values of $R_V$ point to either coherent ISM structures in the disk larger than usual ($\sim9$ kpc) or higher starting values of $R_V$, indicative of recent processing of the dust.   The foreground galaxy is a low stellar mass spiral ($M_* \sim 3 \times 10^9 M_\odot$) with a high dust content ($M_{\rm dust} \sim 0.5 \times 10^6 M_\odot$). The dust disk geometry visible in the HST image would explain the observed SED properties of smaller galaxies: a lower mean dust temperature, a high dust-to-stellar mass ratio but relatively little optical attenuation. Ongoing efforts to find occulting pairs with a small foreground galaxies will show how common this geometry is.
High resolution N-body simulations of galactic cold dark matter haloes indicate that we should expect to find a few satellite galaxies around the Milky Way whose haloes have a maximum circular velocity in excess of 40 kms. Yet, with the exception of the Magellanic Clouds and the Sagittarius dwarf, which likely reside in subhaloes with significantly larger velocities than this, the bright satellites of the Milky Way all appear to reside in subhaloes with maximum circular velocities below 40 kms. As recently highlighted by Boylan-Kolchin et al., this discrepancy implies that the majority of the most massive subhaloes within a cold dark matter galactic halo are much too concentrated to be consistent with the kinematic data for the bright Milky Way satellites. Here we show that no such discrepancy exists if haloes are made of warm, rather than cold dark matter because these haloes are less concentrated on account of their typically later formation epochs. Warm dark matter is one of several possible explanations for the observed kinematics of the satellites.
We present a phenomenological analysis of the magnetoelastic properties of CeCo$_{0.85}$Fe$_{0.15}$Si at temperatures close to the N\'eel transition temperature $T_N$. Using a Landau functional we provide a qualitative description of the thermal expansion, magnetostriction, magnetization and specific heat data. We show that the available experimental results [Journal of Physics: Condensed Matter 28 346003 (2016)] are consistent with the presence of a structural transition at $T_s\gtrsim T_N$ and a strong magnetoelastic coupling. The magnetoelastic coupling presents a Janus-faced effect: while the structural transition is shifted to higher temperatures as the magnetic field is increased, the resulting striction at low temperatures decreases. The strong magnetoelastic coupling and the proximity of the structural transition to the onset temperature for magnetic fluctuations, suggest that the transition could be an analogue of the tetragonal to orthorhombic observed in Fe-based pcnictides.
Carrier dynamics in monolayer MoS2 have been investigated using broadband femtosecond transient absorption spectroscopy (FTAS). A tunable pump pulse was used while a broadband probe pulse revealed ground and excited state carrier dynamics. Interestingly, for pump wavelengths both resonant and non-resonant with the A and B excitons, we observe a broad ground state bleach around 2.9 eV, with decay components similar to A and B. Associating this bleach with the band nesting region between K and Gamma in the band structure indicates significant k-space delocalization and overlap among excitonic wave functions identified as A, B, C, and D. Comparison of time dynamics for all features in resonance and non-resonance excitation is consistent with this finding.
Using ion-implanted $^8$Li $\beta$-detected NMR, we study the evolution of the correlated metallic state of LaNiO$_3$ in a series of LaNiO$_3$/LaAlO$_3$ superlattices as a function of bilayer thickness. Spin-lattice relaxation measurements in an applied field of 6.55 T reveal two equal amplitude components: one with metallic ($T$-linear) $1/T_{1}$, and a second with a more complex $T$-dependence. The metallic character of the slow relaxing component is only weakly affected by the LaNiO$_3$ thickness, while the fast component is much more sensitive, exhibiting the opposite temperature dependence (increasing towards low $T$) in the thinnest, most magnetic samples. The origin of this bipartite relaxation is discussed.
We investigate the clustering of dark energy within matter overdensities and voids. In particular, we derive an analytical expression for the dark energy density perturbations, which is valid both in the linear, quasi-linear and fully non-linear regime of structure formation. We also investigate the possibility of detecting such dark energy clustering through the ISW effect. In the case of uncoupled quintessence models, if the mass of the field is of order the Hubble scale today or smaller, dark energy fluctuations are always small compared to the matter density contrast. Even when the matter perturbations enter the non-linear regime, the dark energy perturbations remain linear. We find that virialised clusters and voids correspond to local overdensities in dark energy, with $\delta_{\phi}/(1+w) \sim \Oo(10^{-5})$ for voids, $\delta_{\phi}/(1+w) \sim \Oo(10^{-4})$ for super-voids and $\delta_{\phi}/(1+w) \sim \Oo(10^{-5})$ for a typical virialised cluster. If voids with radii of $100-300 {\rm Mpc}$ exist within the visible Universe then $\delta_{\phi}$ may be as large as $10^{-3}(1+w)$. Linear overdensities of matter and super-clusters generally correspond to local voids in dark energy; for a typical super-cluster: $\delta_{\phi}/(1+w) \sim \Oo(-10^{-5})$. The approach taken in this work could be straightforwardly extended to study the clustering of more general dark energy models.
We present results on the effect of the stiffness of the equation of state on the dynamical bar-mode instability in rapidly rotating polytropic models of neutron stars in full General Relativity. We determine the change in the threshold for the emergence of the instability for a range of the adiabatic $\Gamma$ index from 2.0 to 3.0, including two values chosen to mimic more realistic equations of state at high densities.
We have developed a unified finite-size scaling method for quantum phase transitions that requires no prior knowledge of the dynamical exponent $z$. During a quantum Monte Carlo simulation, the temperature is automatically tuned by the Robbins-Monro stochastic approximation method, being proportional to the lowest gap of the finite-size system. The dynamical exponent is estimated in a straightforward way from the system-size dependence of the temperature. As a demonstration of our novel method, the two-dimensional $S=1/2$ quantum $XY$ model in uniform and staggered magnetic fields is investigated in the combination of the world-line quantum Monte Carlo worm algorithm. In the absence of the uniform magnetic field, we obtain the fully consistent result with the Lorentz invariance at the quantum critical point, $z=1$, i.e., the three-dimensional classical $XY$ universality class. Under a finite uniform magnetic field, on the other hand, the dynamical exponent becomes two, and the mean-field universality with effective dimension $(2+2)$ governs the quantum phase transition.
We studied the pure and dilute Baxter-Wu (BW) models using the Wang-Landau (WL) sampling method to calculate the Density-Of-States (DOS). We first used the exact result for the DOS of the Ising model to test our code. Then we calculated the DOS of the dilute Ising model to obtain a phase diagram, in good agreement with previous studies. We calculated the energy distribution, together with its first, second and fourth moments, to give the specific heat and the energy fourth order cumulant, better known as the Binder parameter, for the pure BW model. For small samples, the energy distribution displayed a doubly peaked shape. Finite size scaling analysis showed as expected reciprocal scaling of the positions of the peaks with L. The energy distribution yielded the expected $\alpha=2/3$ critical exponent for the specific heat. The Binder parameter minimum appeared to scale with lattice size L with an exponent $\theta_B$ equal to the specific heat exponent. Its location (temperature) showed a large correction-to-scaling term $\theta_1=0.248\pm 0.025$. For the dilute BW model we found a clear crossover to a single peak in the energy distribution even for small sizes and the expected $\alpha=0$ was recoverd.
In the present work, two successive magneto-structural transformations (MSTs) consisting of martensitic and intermartensitic transitions have been reported in polycrystalline Ni55.8Mn18.1Ga26.1 Heusler alloy. Benefiting from the additional latent heat contributed from intermediate phase, this alloy exhibits a large transition entropy change {\Delta}Str with the value of ~28 J/kg K. Moreover, the magnetocaloric effect (MCE) has been also evaluated in terms of Maxwell relation. For the magnetic field change of 3 T, it is found that the calculated value of refrigeration capacity for Ni55.8Mn18.1Ga26.1 attains to ~72 J/kg around room temperature, which significantly surpasses those obtained in many Ni-Mn based Heusler alloys. The mechanism underlying the enhanced MCE is believed to be responsible for these multiple transformations, which can sustain the pronounced isothermal entropy change {\Delta}ST over a relatively wide temperature interval.
The subtraction method for the matching between the matrix element (ME) and parton shower (PS), that has been developed for combining 0-jet and 1-jet production processes in association with electroweak-boson production in hadron collisions, is extended to multi-jet production. In order to include multi-jet MEs, we have to address the soft-gluon divergence together with the collinear divergence. We introduce an approximation which simultaneously reproduces both divergences in a form suitable for application to our subtraction method. The alteration in the subtraction can be compensated by applying an appropriate correction to corresponding non-radiative events. We demonstrate that $W$ + 0, 1, and 2 jet production processes can be consistently combined using the developed matching method.
We performed a search of cloud-cloud collision (CCC) sites in the Sagittarius A molecular cloud (SgrAMC) based on the survey observations using the Nobeyama 45-m telescope in the C$^{32}$S $J=1-0$ and SiO $v=0~J=2-1$ emission lines. We found candidates being abundant in shocked molecular gas in the Galactic Center Arc (GCA). One of them, M0.014-0.054, is located in the mapping area of our previous ALMA mosaic observation. We explored the structure and kinematics of M0.014-0.054 in the C$^{32}$S $J=2-1$, C$^{34}$S $J=2-1$, SiO $v=0~J=2-1$, H$^{13}$CO$^+ J=1-0$, and SO $N,J=2,2-1,1$ emission lines and fainter emission lines. M0.014-0.054 is likely formed by the CCC between the vertical molecular filaments (VP) of the GCA, and other molecular filaments along Galactic longitude. The bridging features between these colliding filaments on the PV diagram are found, which are the characteristics expected in CCC sites. We also found continuum compact objects in M0.014-0.054, which have no counterpart in the H42$\alpha$ recombination line. They are detected in the SO emission line, and would be "Hot Molecular Core (HMC)"s. Because the LTE mass of one HMC is larger than the virial mass, it is bound gravitationally. This is also detected in the CCS emission line. The embedded star would be too young to ionize the surrounding molecular cloud. The VP is traced by poloidal magnetic field. Because the strength of the magnetic field is estimated to be $\sim m$Gauss using the CF method, the VP is supported against fragmentation. The star formation in the HMC of M0.014-0.054 is likely induced by the CCC between the stable filaments, which may be a common mechanism in the SgrAMC.
Excitation spectra and neutron single particle configurations of $^{33}$Mg and $^{31}$Ne are investigated by using antisymmetrized molecular dynamics combined with generator coordinate method. It is shown that both nuclei have strongly deformed $3/2^-$ ground state with a $3p2h$ configuration. The excitation spectra are qualitatively understood in terms of the Nilsson model and the calculation has shown the coexistence of different intruder configurations within small excitation energy. The calculated one neutron separation energy of $^{31}$Ne is rather small ($S_n=250$ keV) and implies a p-wave one neutron halo with a strongly deformed core.
The S=1/2 and S=1 two-dimensional quantum Heisenberg antiferromagnets on the anisotropic dimerized square lattice are investigated by the quantum Monte Carlo method. By finite-size-scaling analyses on the correlation lengths, the ground-state phase diagram parametrized by strengths of the dimerization and of the spatial anisotropy is determined much more accurately than the previous works. It is confirmed that the quantum critical phenomena on the phase boundaries belong to the same universality class as that of the classical three-dimensional Heisenberg model. Furthermore, for S=1, we show that all the spin-gapped phases, such as the Haldane and dimer phases, are adiabatically connected in the extended parameter space, though they are classified into different classes in terms of the string order parameter in the one-dimensional, i.e., the zero-interchain-coupling, case.
Let $G$ be an algebraic group and let $\widetilde{\mathfrak g}$ be the corresponding affine algebra on some level. Consider the induced module $V:=Ind^{\widetilde{\mathfrak g}}_{{\mathfrak g}[[t]](O_{G[[t]]})$, where $O_{G[[t]]}$ is the ring of regular functions on the group $G[[t]]$.   In this paper we show that $V$ is naturally a vertex operator algebra, which is "responsible" for D-modules on the loop group $G((t))$. Using the techiques of VOA we show that $V$ is in fact a bimodule over the affine algebra. In addition, we show that $V$ possesses a remarkable property related to its BRST reduction with respect to $\widetilde{\mathfrak g}$.   This paper has a considerable intersection with a recent preprint of Gorbunov, Malikov and Schechtman.
We use an $N$-body+smoothed particle hydrodynamics simulation of an isolated barred galaxy to study the age dependence of bulge longitudinal proper motion ($\mu_l$) rotation curves. We show that close to the minor axis ($|l| \sim 0^\circ$) the relatively young stars rotate more rapidly than the old stars, as found by Hubble Space Telescope in the Milky Way's (MW's) bulge. This behaviour would be expected also if the MW were unbarred. At larger $|l|$ a different behaviour emerges. Because younger stars trace a strong bar, their galactocentric radial motions dominate their $\mu_l$ at $|l| \sim 6^\circ$, leading to a reversal in the sign of $\left< \mu_l \right>$. This results in a rotation curve with forbidden velocities (negative $\left< \mu_l \right>$ at positive longitudes, and positive $\left< \mu_l \right>$ at negative longitudes). The old stars, instead, trace a much weaker bar and thus their kinematics are more axisymmetric, resulting in no forbidden velocities. We develop metrics of the difference in the $\left< \mu_l \right>$ rotation curves of young and old stars, and forbidden velocities. We use these to predict the locations where rotation curve reversals can be observed by HST and the Vera Rubin Telescope. Such measurements would represent support for the amplitude of the bar being a continuous function of age, as predicted by kinematic fractionation, in which the bar strength variations are produced purely by differences in the random motions of stellar populations at bar formation.
Here we report results of an INTEGRAL-AO1 observation of the X-ray burst and atoll source Ser X-1 performed in May 2003. The object was observed for a total on-source time of 400 ks but nearly 8 degrees off-axis due to its amalgamation with an observation of SS 433, the pointing target source. Ser X-1 has been clearly detected up to 30 keV with unprecedented positional accuracy for high-energy emission. The 20-30 keV light curve showed substantial variability during the observation. Comparison with previous observations indicates that the source was in its high (`banana') state and displayed a soft spectrum during the INTEGRAL pointing. A (non simultaneous) radio-to-gamma-rays broad-band spectral energy distribution is also presented for the first time and discussed.
Recently, Heyrovsk\'y & Sasselov (1999) investigated the sensitivity of {\it single-lens} gravitational microlensing event light curves to small spots and found that during source transit events spots can cause deviations in amplification larger than 2%, and thus be detectable. In this paper, we explore the feasibility of spot detection from the observations of {\it caustic-crossing binary-lens} microlensing events instead of single-lens events. For this we investigate the sensitivity of binary-lens event light curves to spots and compare it to that of single-lens events. From this investigation, we find that during caustic crossings the fractional amplification deviations of microlensing light curves from those of spotless source events are equivalent to the deviations of single-lens events, implying that spots can also be detected with a similar photometric precision to that required for spot detection by observing single-lens events. We discuss the relative advantages of observing caustic-crossing binary-lens events over the observations of single-lens events in detecting stellar spots.
Multi-color ($B$ $V$ $R_c$ $I_c$) CCD photometric light curves of the contact binary V502 Oph are analyzed using the Wilson-Devinney (W-D) program. The solutions reveal that V502 Oph is a W-subtype contact ($f = 35.3\,\%$) binary system. The temperature difference between its two components is $240K$ and the more massive star has a lower surface temperature. A cool spot is added in our model to account for the light curves' asymmetry (O'Connell effect) and third light is detected for the first time in the light curves' modeling. Combining the orbital inclination ($i = 76.4^{\circ}$) with the published mass function of V502 Oph, the absolute physical parameters of the two components are determined, which are $M_1= 0.46(\pm0.02)M_\odot, M_2=1.37(\pm0.02)M_\odot, R_1=0.94(\pm0.01)R_\odot, R_2=1.51(\pm0.01)R_\odot, L_1=1.13(\pm0.02)L_\odot$ and $L_2=2.49(\pm0.03)L_\odot$. The formation and evolutionary status of V502 Oph are discussed. All photoelectric and CCD times of light minimum about V502 Oph are gathered and its orbital period variations are analyzed. The results show that the orbital period of V502 Oph is decreasing continuously at a rate of $dP/dt=-1.69\times{10^{-7}}day\cdot year^{-1}$, which corresponds to a conservative mass transfer rate of $\frac{dM_{2}}{dt}=-3.01\times{10^{-8}}M_\odot/year$. The light-travel time effect (LTTE) is due to the presence of a close-in tertiary component with a period of $P_3=18.7$ years and an amplitute of 0.00402days. V502 Oph is an ideal target to test the formation and evolution theories of binary and multiple systems in which the light curves, $O - C$ curve and spectroscopic observations are comprehensively researched.
In the Entropic Dynamics (ED) derivation of the Schroedinger equation the physical input is introduced through constraints that are implemented using Lagrange multipliers. There is one constraint involving a "drift" potential that correlates the motions of different particles and is ultimately responsible for entanglement. The purpose of this work is to deepen our understanding of the corresponding multiplier. Its main effect is to control the strength of the drift relative to the fluctuations. We show that ED exhibits a symmetry: models with different values of the multiplier can lead to the same Schroedinger equation; different "microscopic" or sub-quantum models lead to the same "macroscopic" or quantum behavior. As the multiplier tends to infinity the drift prevails over the fluctuations and the particles tend to move along the smooth probability flow lines. Thus ED includes the causal or Bohmian form of quantum mechanics as a special limiting case.
To investigate chemical reactivity of Cu atomic-scale structures, we performed simulations based on the generalized gradient approximation in the density functional theory. An atomic layer of Cu forming a triangular lattice (TL) was found to give a stable structure. The nitrogen monoxide molecule (NO) was adsorbed on some atomic sites of TL or on an atomic step structure (ASS) of Cu. The molecular adsorption energy on TL was -0.83 eV. Our data suggested that dissociative adsorption of NO with a dissociation energy of -1.08 eV was possible with an energy barrier of order 1.4 eV. In this optimized structure, the nitrogen and oxygen atoms were embedded in the Cu layer. On the step, NO adsorbed at a bridge site and the formation energy of Cu-(NO)-Cu local bond connections was estimated to be around -1.32 eV. Molecular dissociation of NO with a dissociation energy of -0.37 eV was also possible around ASS.
An insulating ferromagnetic (FM) phase exists in the quasi-one-dimensional iron chalcogenide Ce$_2$O$_2$FeSe$_2$ but its origin is unknown. To understand the FM mechanism, here a systematic investigation of this material is provided, analyzing the competition between ferromagnetic and antiferromagnetic tendencies and the interplay of hoppings, Coulomb interactions, Hund's coupling, and crystal-field splittings. Our intuitive analysis based on second-order perturbation theory shows that large entanglements between doubly-occupied and half-filled orbitals play a key role in stabilizing the FM order in Ce$_2$O$_2$FeSe$_2$. In addition, via many-body computational techniques applied to a multi-orbital Hubbard model, the phase diagram confirms the proposed FM mechanism, in agreement with experiments.
In this paper we investigate the transport of energetic particles in turbulent plasmas. A numerical approach is used to simulate the effect of the background plasma on the motion of energetic protons. The background plasma is in a dynamically turbulent state found from numerical MHD simulations, where we use parameters typical for the heliosphere. The implications for the transport parameters (i.e. pitch-angle diffusion coefficients and mean free path) are calculated and deviations from the quasi-linear theory are discussed.