arXiv subjects

Jiejia Liu

Publications and source records attributed to Jiejia Liu.

7 recordsLinked to original sources

arXiv2026

X-ray measurements of the elemental abundances for the diffuse emission in the nuclear starburst galaxy NGC 3079

Outflows driven by feedback leave imprints on a galaxy's diffuse X-ray emission. Elemental abundances provide key diagnostics of feedback-driven chemical enrichment. We present a spectroscopic study of the diffuse X-ray emission in NGC 3079 using XMM-Newton RGS and EPIC, focusing on the nuclear region and the extended galactic-scale superbubble (GSB). We analyzed the high-resolution RGS spectrum of the central $\sim4~\rm kpc$ region, encompassing the $\sim1~\rm kpc$ nuclear superbubble (NSB), and the EPIC spectrum of the GSB out to $5'~(\sim25~\rm kpc)$. The nuclear spectrum is best described by a multi-temperature thermal-plasma model plus a charge-exchange (CX) component, which contributes approximately $13\%$ of the total observed energy flux in the $0.2-2~\rm keV$ band. The best-fit O/Fe and Ne/Fe ratios are $0.47$ and $0.77$ in solar units. Comparing these ratios with IMF-weighted core-collapse supernova (SNcc) yields gives an upper progenitor-mass cutoff of $M_{\rm u}\simeq13-15~M_{\odot}$ for pure SNcc enrichment. For the best-fit spectral model, including an SNIa contribution increases the inferred cutoff, but its $1σ$ upper limit remains below $25~M_\odot$ for SNIa fractions up to $10\%$ within the adopted yield models. The characteristic ages of the NSB and GSB are $0.92^{+0.39}_{-0.46}~\rm Myr$ and $29.6^{+1.6}_{-2.9}~\rm Myr$, respectively, suggesting episodic feedback in NGC 3079.

astro-ph.HE↗

arXiv2026

DIffuse X-ray Explorer (DIXE): Sky Survey Strategy and Collimator Response Demodulation

DIffuse X-ray Explorer (DIXE) is a proposed high-resolution X-ray spectroscopic surveyor aimed at studying large structures of hot gas in the Milky Way. Its payload is designed to have a field of view (FoV) of $10^\circ$ (half-power diameter) and an energy resolution of better than 6 eV, covering an energy range of 0.1-10 keV. It will be mounted on the China Space Station (CSS) and follow the CSS orbit to conduct the survey with fixed zenith pointing in order to optimize the coverage of key science targets. The payload will avoid the Sun passively via an operable sunshade, where a minimum $25^\circ$ angular separation between the pointing axis and the direction of the Sun is required. Two Sun-avoidance strategies are considered: one focusing on minimizing mechanical risk and the other on maximizing exposure time. The one-year exposure maps indicate that DIXE will cover approximately $72.5\%$ of the sky, with typical exposure times of 26 ks and 68 ks for the two strategies, respectively. Although mechanically collimated, the imaging performance of the payload can be enhanced with a demodulation method based on Markov Chain Monte Carlo sampling using the collimator response. Through simulation, we found that the method could achieve a localization accuracy of $1^\circ$ for point-like sources and a spatial resolution of $3^\circ$ for the extended sources of complex surface brightness distribution, both of which are significantly smaller than the FoV.

astro-ph.IM↗

arXiv2026

The SRG/eROSITA diffuse soft X-ray background II. spectra and morphology of the eROSITA bubbles in the western Galactic hemisphere

The eROSITA bubbles (eRObub) were discovered in 2020 in the first SRG/eROSITA All-Sky Survey, and are among the most extended structures in the X-ray sky. Using eROSITA all-sky maps and spatially resolved spectra, we aim to infer the three-dimensional structure and measure the hot gas properties of the eRObub. We fit spectra binned to a constant S/N and high-S/N spectra from custom regions to examine gas properties in more detail. We fit the morphology of eRObub with a parametrised geometrical model that describes a blast wave propagating into an idealised Galactic halo from the centre. We found the interior of the western eRObub is best characterised by two emission components with relatively uniform temperatures: a hotter component at $kT=0.60\pm0.02$ keV, and a colder one at $kT=0.21^{+0.03}_{-0.01}$ keV, where the latter's emission measure is about five times higher on average. Our spectra suggest sub-solar abundances ($Z=0.2\pm0.1 Z_\odot$), consistent with expectations for the Galactic halo, while we find no conclusive evidence for $α$-element enhancement. In contrast, the North Polar Spur exhibits higher abundances ($Z>0.5 Z_\odot$), which, at face value, disfavours a common origin. We spectrally confirm an apparent cool shell at $kT\sim0.18$-$0.2$ keV surrounding the northern eRObub, assuming collisional ionisation equilibrium. We found no noticeable difference in X-ray emission in regions overlapping with the Fermi Bubbles. Our geometrical model suggests that the horizontal size of both eRObub is well-constrained (semi-minor axis $\sim 6$ kpc), but their vertical extent is uncertain, as the observed X-ray emission is almost insensitive to the existence and location of a bubble cap. Additionally, a tilt ($\sim 30^{\circ}$) towards $l\sim 220^{\circ}$ is needed to reproduce the projected image of the northern eRObub, whereas the southern bubble requires little tilt.

astro-ph.HE↗

arXiv2026

Simulation of non X-ray background for the DIffuse X-ray Explorer (DIXE) mission

DIffuse X-ray Explorer (DIXE) is a proposed high-resolution spectroscopic survey mission onboard the China Space Station. Equipped with microcalorimeters based on the Transition-edge sensor technology, it aims to survey the hot gas in the Milky Way. The performance of DIXE depends on the understanding of non X-ray background (NXB), which can strongly affect observations of diffuse X-ray emission. In this work, we simulated the NXB of DIXE in a low-earth orbit (LEO) using \textsc{Geant4}. A detailed mass model of the payload was constructed, and the major sources of NXB were identified, including cosmic rays, albedo neutrons and albedo photons. These components were implemented in \textsc{Geant4} with realistic angular and spectral distributions. We simulated the relevant physical processes of space radiation interacting with the instrument and calculated the resulting NXB. We also evaluated the delayed background from trapped protons in the South Atlantic Anomaly (SAA). Our simulations show that, at the geomagnetic equator and under solar minimum conditions, the NXB is on average $4.46 \times 10^{-2} ~\mathrm{counts~s^{-1}~cm^{-2}~keV^{-1}}$ in 0.1--10 keV energy band, with dominant contributions from the induced particles generated by primary cosmic protons. The NXB increases toward higher geomagnetic latitudes, reaching a maximum of $1.55 \times 10^{-1} ~\mathrm{counts~s^{-1}~cm^{-2}~keV^{-1}}$. The delayed background induced by the SAA decays rapidly after exiting the anomaly and becomes negligible within approximately 5 minutes. The simulated NXB is consistent with that of similar X-ray observatories in LEOs.

astro-ph.IM↗

arXiv2025

Probing ALP-Photon Mixing with High-Resolution X-ray Spectroscopy

Axion-like particles (ALPs) provide a compelling avenue for exploring physics beyond the Standard Model. In astrophysical magnetized plasmas an ALP-photon coupling $g_{aγ}$ induces energy-dependent oscillations in the photon survival probability that imprint modulations on emission spectra. X-ray observations of bright spectrally-smooth sources can provide particularly sensitive probes of ultralight ALPs with masses $m_a \lesssim 10^{-11}$ eV due to long propagation distances, strong magnetic fields and high photon statistics. We present a comprehensive forecast of ALP-photon conversion in three representative systems: (i) background active galactic nuclei (AGNs) observed through foreground intracluster magnetic fields, (ii) central AGNs within their host cluster halos and (iii) Galactic X-ray binaries viewed through the Milky Way field. Using detailed simulations we assess the prospective sensitivity of high-resolution X-ray missions including XRISM, Athena, and Arcus. For typical magnetic field configurations a 5 Ms XRISM observation of the Perseus Cluster AGN NGC 1275 can reach down to $g_{aγ} \sim 3 \times 10^{-13}$ GeV$^{-1}$ at $m_a \lesssim 10^{-12}$ eV, while Athena's superior energy resolution improves this reach by a factor of $\sim 3$. We quantify the impact of magnetic field modeling, photon statistics, and spectral binning strategies. Our results demonstrate the scientific potential of high-resolution X-ray observations to probe photon-ALP coupling in previously inaccessible parameter space, offering a powerful window into physics beyond the Standard Model.

astro-ph.HE↗

arXiv2024

Diffuse X-ray Explorer: a high-resolution X-ray spectroscopic sky surveyor on the China Space Station

DIffuse X-ray Explorer (DIXE) is a proposed high-resolution X-ray spectroscopic sky surveyor on the China Space Station (CSS). DIXE will focus on studying hot baryons in the Milky Way. Galactic hot baryons like the X-ray emitting Milky Way halo and eROSITA bubbles are best observed in the sky survey mode with a large field of view. DIXE will take advantage of the orbital motion of the CSS to scan a large fraction of the sky. High-resolution X-ray spectroscopy, enabled by superconducting microcalorimeters based on the transition-edge sensor (TES) technology, will probe the physical properties (e.g., temperature, density, elemental abundances, kinematics) of the Galactic hot baryons. This will complement the high-resolution imaging data obtained with the eROSITA mission. Here we present the preliminary design of DIXE. The payload consists mainly of a detector assembly and a cryogenic cooling system. The key components of the detector assembly are a microcalorimeter array and frequency-domain multiplexing readout electronics. To provide a working temperature for the detector assembly, the cooling system consists of an adiabatic demagnetization refrigerator and a mechanical cryocooler system.

astro-ph.IM↗

arXiv2024

Preliminary Design of Detector Assembly for DIXE

Diffuse X-ray Explorer (DIXE) is a proposed X-ray spectroscopic survey experiment for the China Space Station. Its detector assembly (DA) contains the transition edge sensor (TES) microcalorimeter and readout electronics based on the superconducting quantum interference device (SQUID) on the cold stage. The cold stage is thermally connected to the ADR stage, and a Kevlar suspension is used to stabilize and isolate it from the 4 K environment. TES and SQUID are both sensitive to the magnetic field, so a hybrid shielding structure consisting of an outer Cryoperm shield and an inner niobium shield is used to attenuate the magnetic field. In addition, IR/optical/UV photons can produce shot noise and thus degrade the energy resolution of the TES microcalorimeter. A blocking filter assembly is designed to minimize the effects. In it, five filters are mounted at different temperature stages, reducing the probability of IR/optical/UV photons reaching the detector through multiple reflections between filters and absorption. This paper will describe the preliminary design of the detector assembly and its optimization.

astro-ph.IM↗