arXiv subjects

X. Y. Zheng

Publications and source records attributed to X. Y. Zheng.

5 recordsLinked to original sources

arXiv2026

EP-FXT observations of the cool-core cluster Abell 478 out to R200: Thermodynamic properties and azimuthal asymmetry

We use deep observations from the Einstein Probe Follow-up X-ray Telescope (EP-FXT) to investigate the gas distribution and thermodynamic properties of the cool-core galaxy cluster Abell 478 (A478) from the center out to $R_{200}$, and to examine its azimuthal asymmetry and the influence of local dynamical disturbances on hydrostatic mass estimates. We derive the surface-brightness, temperature, electron-density, pressure, entropy, and total mass profiles. The surface-brightness distribution is well described by a double-$β$ model, while the temperature profile shows the characteristic cool-core behavior, with a cool center, a rise toward intermediate radii, and a gradual decline in the outskirts. The hydrostatic mass profile is well fitted by a Navarro-Frenk-White model, yielding $R_{200}=2082\pm95$ kpc and $M_{200}=(1.12\pm0.15)\times10^{15}\,M_\odot$, indicating that the cluster is close to quasi-static equilibrium on global scales. Despite the globally regular structure, clear azimuthal asymmetry is present. The SW sector shows lower temperatures, higher densities, and lower entropies at intermediate and large radii, together with signatures consistent with a cold-front candidate. Combined with the two-dimensional temperature distribution, these features suggest local dynamical disturbance, likely associated with gas sloshing. A478 is therefore globally relaxed but locally disturbed, demonstrating that nonequilibrium structures can still affect thermodynamic measurements and hydrostatic mass estimates even in an apparently regular cool-core cluster.

astro-ph.GA↗

arXiv2026

EP-FXT Observations of Abell 1795: X-ray properties and structure out to $R_{200}$

We present deep X-ray observations of the nearby X-ray-luminous galaxy cluster Abell 1795 obtained with the Einstein Probe Follow-up X-ray Telescope EP-FXT, with a total exposure time of $\sim 480$ ks. Exploiting the large field of view and low particle background of EP-FXT, we directly measured the radial temperature profile of A1795 out to $R_{200}$ with full azimuthal coverage, which was shown to increase in line with the radius within 6' and then gradually decline toward larger radii. The surface-brightness residual map and 2D thermodynamic maps reveal a clockwise spiral structure extending from the cluster core towards the south-east, which traces low-temperature and low-entropy gas, which is also consistent with sloshing-induced cold fronts. In the north-west, the surface-brightness-enhanced region exhibits an arc-like high-temperature feature and both the temperature-derived and density-derived Mach numbers support the assumption that it is a weak shock. These substructures can be explained by a binary merger scenario: the perturbing subcluster induces sloshing during its first passage past the primary core and its subsequent return passage through the ICM might drive the shock towards the north-west. Our results indicate that relaxed galaxy clusters such as A1795 might still retain signatures of dynamical activity.

astro-ph.HE↗

arXiv2024

Inelastic neutron scattering and muon spin relaxation investigations of the deuterated Kondo lattices CeNiSnD$ _x $

CeNiSn is a Kondo semimetal where a gap opens at low temperatures due to hybridization between 4$f$ and conduction electrons, but a full insulating state fails to develop. Upon the insertion of hydrogen, long range magnetic order is induced. Here we report zero-field muon-spin relaxation and inelastic neutron scattering measurements of polycrystalline samples of the deuterides CeNiSnD$_x$ ($x$=1.0, 1.8). The muon-spin relaxation results confirm magnetic ordering in the whole sample of CeNiSnD below around 4.7 K, while inelastic neutron scattering reveals two well-defined crystalline-electric field (CEF) excitations at around 13 meV and 34 meV in CeNiSnD, and 5 meV and 27 meV for CeNiSnD$_{1.8}$. These results suggest that hydrogenation leads to the localization of the Ce-4$f$ electrons, giving rise to long-range magnetic order. We propose CEF level schemes for both systems, which predict a ground state moment of 0.96$μ_{\rm B}$/Ce within the $ab$-plane for CeNiSnD$_{1.8}$ and a saturated moment of 1.26$μ_{\rm B}$/Ce along the easy $c$ axis for CeNiSnD, that account for the observed magnetic properties.

cond-mat.str-el↗

arXiv2022

Semimetallic Kondo lattice behavior in YbPdAs with a distorted kagome structure

We have synthesized YbPdAs with the hexagonal ZrNiAl-type structure, in which the Yb-atoms form a distorted kagome sublattice in the hexagonal basal plane. Magnetic, transport, and thermodynamic measurements indicate that YbPdAs is a low-carrier Kondo lattice compound with an antiferromagnetic transition at $T_\mathrm{N}$ = 6.6 K, which is slightly suppressed in applied magnetic fields up to 9 T. The magnetic entropy at $T_\mathrm{N}$ recovers only 33\% of $R\ln{2}$, the full entropy of the ground state doublet of the Yb-ions. The resistivity displays a $-\ln T$ dependence between 30 and 15 K, followed by a broad maximum at $T\rm_{coh}$ = 12 K upon cooling. Below $T\rm_{coh}$, the magnetoresistance changes from negative to positive, suggesting a crossover from single-ion Kondo scattering processes at intermediate temperatures to coherent Kondo lattice behaviors at low temperatures. Both the Hall resistivity measurements and band structure calculations indicate a relatively low carrier concentration in YbPdAs. Our results suggest that YbPdAs could provide an opportunity for examining the interplay of Kondo physics and magnetic frustration in low carrier systems.

cond-mat.str-el↗

arXiv2021

Complex magnetic phase diagram in noncentrosymmetric EuPtAs

We report the observation of multiple magnetic transitions in single crystals of EuPtAs using magnetization, transport, and thermodynamic measurements. EuPtAs crystallizes in the noncentrosymmetric tetragonal LaPtSi-type structure (space group I41md) and undergoes a second-order antiferromagnetic transition at 14.8 K, which is followed by a first-order transition at about 7.5 K. Both transitions are suppressed by magnetic fields applied parallel and perpendicular to the c axis, and multiple field-induced transitions are observed for both field directions, leading to complex temperature-field diagrams with a dome-like magnetic phase for fields parallel to the c axis. Moreover, the dependence of the low temperature resistivity on the application of a training field, but the lack of remanent magnetization, suggests the presence of multiple antiferromagnetic domains in zero-field.

cond-mat.mtrl-sci↗