arXiv subjects

Jiang-Tao Li

Publications and source records attributed to Jiang-Tao Li.

At least 19 recordsLinked to original sources

arXiv2026

A Possible Hidden Hot Halo Component Revealed by Joint X-ray and Sunyaev--Zel'dovich Observations

Massive galaxies are expected to host extended halos of hot gas that contain a substantial fraction of their baryons and feedback energy. X-ray observations probe the dense, X-ray-bright component of this circumgalactic medium (CGM), while the thermal Sunyaev-Zel'dovich (SZ) effect is also sensitive to lower-density gas through its integrated thermal pressure. We present the first spatially resolved joint X-ray and SZ analysis of a massive isolated disk galaxy, using deep XMM-Newton observations of NGC 4594 from the X-raying the Accretion Reservoir Transferred to the ATmosphere Orbiting a Massive Spiral (XART-ATOMS) program, together with multiple independent Planck-based SZ reconstructions. The measured SZ signal in the inner halo appears to exceed the value predicted from the X-ray-derived gas properties, even after accounting for major systematic uncertainties. Our preferred interpretation is that an additional lower-density CGM component contributes little to the observed soft X-ray emission but carries substantial thermal pressure. Under a simple two-phase model in approximate pressure equilibrium, the most probable X-ray-to-SZ ratio implies that the detected X-ray-emitting gas occupies only a small fraction of the halo volume, with a characteristic filling factor of f_X ~ (4-6)x10^-3 near r~50 kpc. Such a small filling factor implies that single-phase X-ray analyses can underestimate the baryon mass contained in the hot CGM by a factor of ~2.5, while the thermal energy content of the CGM is underestimated by about one order of magnitude. The non-detection of the additional component in the X-ray spectra requires it to be very hot and/or spatially extended, so weak in the soft X-ray emissions. These results favor the presence of a "hidden" X-ray-faint hotter halo component, while alternative interpretations, including a nonthermal contribution, are not excluded.

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arXiv2026

Energy Partition in AGN-driven Bubbles of NGC 4438: From Nuclear Bubbles to a Galaxy-scale Outflow

Jets launched by accreting supermassive black holes represent a major mode of active galactic nucleus (AGN) feedback. However, how their energy is divided among bulk kinetic motion, thermal gas, magnetic fields, cosmic rays (CRs), and radiation - and how this distribution changes with spatial scale - remains poorly constrained. NGC 4438 provides a unique laboratory for probing this evolution, hosting two 200-pc-scale nuclear bubbles and a lopsided ~10 kpc galaxy-scale outflow plausibly associated with the same AGN. We present a multi-wavelength analysis to investigate the morphology, radiation mechanisms, and energetics of these structures. Joint radio-X-ray modeling shows that the non-thermal emission in the nuclear bubbles may require two distinct populations of cosmic-ray electrons, suggesting that in addition to shock acceleration at the bubble rim, the highest-energy particles may be linked to acceleration processes closer to the unresolved central engine. A spatially resolved energy inventory reveals that bulk kinetic energy dominates the current energy budget of the nuclear bubbles, while roughly half of the injected energy has already been transformed into thermal, CR, and magnetic energy, as well as radiative losses. Across all bubble sizes, the thermal and magnetic pressures are consistent within the uncertainties, implying that magnetic fields remain dynamically significant on all examined spatial scales. Furthermore, the empirical correlation between radio luminosity and jet power, established for kiloparsec-scale jet bubbles (MerloniHeinz2007), matches the energetics of the galaxy-scale outflow but substantially overestimates the power of the 200-pc-scale nuclear bubbles, underscoring the scale dependence of jet energy dissipation.

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arXiv2026

CHANG-ES. XXXVIII. A Thin Radio Halo Shaped by Slow Cosmic-Ray Transport in the Quiescent Galaxy NGC 4565

We present the VLA C-array S-band (2--4 GHz) radio continuum observations of the nearby edge-on spiral galaxy NGC 4565, a target from the Continuum Halos in Nearby Galaxies - an EVLA (CHANG-ES) Survey. We conduct rotation measure synthesis to probe the magnetic field structure and analyze the vertical radio continuum intensity profiles using the 1-D cosmic ray transportation models. The radio continuum emission of NGC 4565 is vertically compact, with a vertical-to-radial extent ratio of $\sim 1/6$. Its vertical profile is optimally described by a two-component Gaussian distribution, yielding a mean Gaussian halo scale height of $\sim 3.0$ kpc. The magnetic field is weak, predominantly disk-parallel, with an equipartition strength of $\lesssim 5\ μ$G and a rotation measure profile indicative of an axisymmetric spiral structure. Nevertheless, we identify a localized, faint vertical magnetic field component in the northeastern region, hinting at an X-shaped structure that spatially coincides with extraplanar structures detected in H I and soft X-ray emission. The CR transport modeling favors a flux-tube advection scenario, with a slow initial velocity of $v_0 \approx 60$ km s$^{-1}$, consistent with a limited energy input from star formation. Therefore, the absence of an extended radio halo can be explained by the low star formation rate, the weak magnetic field, and the inefficient CR transport. The localized X-shaped field may trace a weak, magnetically guided outflow or a tidal perturbation induced by the nearby companion. NGC 4565 is thus a key quiescent benchmark for understanding the physical conditions required to drive large-scale outflows and generate extended radio halos.

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arXiv2026

Analytical Framework for Expanding Bubbles in a Hot Circumgalactic Medium

We develop an analytic framework for the evolution of feedback-driven bubbles expanding into a hot, volume-filling circumgalactic medium (CGM), where the ambient pressure and sound speed are non-negligible and radiative cooling is often inefficient. The evolution is organized into four stages -- free expansion, Sedov--Taylor expansion, pressure-modified/transonic transition, and post-transonic relaxation -- and we derive self-consistent scalings for the characteristic radii and timescales that delimit these stages. A central result is that, in hot halos, the end of the strong-shock evolution is frequently set by pressure confinement and transonicity rather than by the onset of catastrophic cooling, implying only a modest late-time overshoot beyond the pressure-balance/transonic point. We connect the dynamics to observable outcomes by estimating bubble sizes and lifetimes, order-of-magnitude band-limited X-ray luminosities, and high-ionization ion column densities, and we provide stitched numerical trajectories that contrast our pressure-modified model appropriate for hot CGM conditions with a classical Sedov--Taylor benchmark. We then discuss physically motivated extensions beyond the single-event baseline, including continuous or episodic energy injection relevant for AGN-driven bubbles and nuclear outflows, highlighting the much higher specific energy of AGN feedback compared to supernovae and the resulting dynamical differences in how bubbles are driven. We further outline how multiphase interaction, mass loading, anisotropic dissipation, intermittency, confinement, and non-thermal channels can increase the emergent X-ray radiation efficiency without requiring changes to the intrinsic feedback energy partition at the launching site. This framework provides a transparent bridge between idealized bubble theory and feedback signatures in hot galactic halos.

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arXiv2026

Probing Large-scale Structure and the Multi-Phase IGM at the Cosmic Noon -- Insights from a Joint Survey with Euclid, CSST, JPCam, and JUST

We present scientific and technical justifications of a potential coordinated Euclid/CSST/JPCam/JUST survey of the Euclid Deep Field North (EDF-N), aimed at probing the multi-phase circumgalactic and intergalactic medium (CGM/IGM) at the cosmic noon over ~20 deg$^2$. The survey is structured around three connected goals: (1) improving photometric redshift (photo-z) accuracy through the combination of broad- and narrow-band photometry, enabling reliable identification of large-scale structures; (2) probing extended CGM emission with dedicated narrow-band imaging; and (3) mapping foreground IGM via absorption-line spectroscopy of background galaxies. Together, these components establish an integrated observational framework to investigate galactic ecosystems -- linking galaxies to their circumgalactic and intergalactic environments -- at cosmic noon. We show that the J-PAS-like narrow-band system used in JPCam substantially improves photo-z accuracies from only the Euclid/CSST broad-band data, especially for star-forming galaxies at z~1.0-1.4. This enables the identification of galaxy groups and (proto-)clusters directly from photo-z measurements. Stacked JPCam narrow-band imaging should also detect extended [O II]-emitting CGM halos. We then construct mock 3D gas distribution model and realistic galaxy catalog, and further construct mock CSST and JUST background galaxy spectra adding Lyalpha and Mg II absorptions. The reconstructed 3D H I field from CSST Lyalpha forest reliably recovers large-scale structures; however, our simulations indicate that detecting diffuse IGM Mg II absorption with JUST is infeasible, either through spectral stacking or via the two-point correlation function method. We conclude that constraining the metallicity of the diffuse IGM will require significantly deeper and higher-resolution spectroscopy expected from future facilities such as the 39 m E-ELT.

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arXiv2026

Cosmic-ray electron propagation in NGC 3044 from radio continuum observations

Star-forming edge-on galaxies often exhibit extended halo radiation in multiple bands, providing ideal laboratories for studying the transfer of matter from the disk to the halo. We investigate the transport of cosmic-ray electrons (CREs) and the associated galactic wind, and assess their impact on the surrounding medium in NGC 3044. We obtained the NGC 3044 total intensity image at 943 MHz from the Australian SKA Pathfinder (ASKAP) observations with a resolution of 16 arcsec and an rms noise of 20 $μ$Jy beam$^{-1}$. The sensitivity is higher than the previous observations at similar frequencies. We find that the ASKAP intensity profiles perpendicular to the disk can be fit with two exponential components. The scale heights of the thin and thick disks are $0.43 \pm 0.13$ kpc and $1.91 \pm 0.26$ kpc, respectively. By jointly fitting total intensity and spectral index profiles with one-dimensional advection and diffusion models, we find that CREs are advected outward from the disk with the velocity increasing with height in a power law. Beyond $\sim3$ kpc, the velocity exceeds the escape speed of $\sim400$ km s$^{-1}$, indicating a strong wind. We further identify a possible superbubble of radius $\sim3$ kpc filled with soft X-ray emitting hot gas and surrounded by an HI shell and a bright H$α$ rim. These results demonstrate that radio continuum observations provide a powerful probe of cosmic-ray-driven winds in normal star-forming spiral galaxies.

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arXiv2026

Simulating the Formation of the Young "Fermi Bubbles" in the Circinus Galaxy

The Fermi and eROSITA bubbles in the Milky Way represent an archetypal case of galactic nucleus feedback, yet their origin remains highly debated. Here we use hydrodynamic simulations to investigate the formation of the "Fermi bubbles" in the nearby Circinus galaxy, a pair of kpc-scaled elliptical bubbles seen in both radio and X-ray observations. We find that a pair of active galactic nucleus (AGN) jets drive forward shocks in the circumgalactic medium, and after evolving for ~0.95 Myr, the shock-delineated bubble pair roughly matches the observed Circinus bubbles in size and morphology. Our mock X-ray image and spectrum reproduce the observed edge-brightened X-ray surface brightness distribution and spectrum quite well, and suggest that non-thermal emissions from the jet ejecta also contribute substantially to radio and X-ray emissions from the inner "hotspot" region. We further show that AGN winds tend to produce more spherical bubbles with a wider base near the galactic plane, inconsistent with observations. The hotspot emissions and the misalignment between the galaxy rotational axis and the bubble's axis argue against a starburst wind origin. Our study thus corroborates the AGN jet-shock model for the origin of both the Circinus bubbles and the Fermi bubbles, and suggests that AGN jet feedback may be a common origin of extended gaseous bubbles in regular disk galaxies, potentially playing an important role in their evolution.

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arXiv2025

A Deep Chandra X-ray Survey of a Luminous Quasar Sample at $z\sim$ 7

We present new Chandra observations of seven luminous quasars at $z>6.5$. Combined with archival Chandra observations of all other known quasars, they form nearly complete X-ray observations of all currently known $z\sim7$ quasars with $M_{1450}<-26.5$, except for J0313$-$1806 at $z=7.642$ and J0910$-$0414 at $z=6.636$. Together with existing ground-based NIR spectroscopy and ALMA observations, we investigate the correlations between X-ray emission (the X-ray luminosity $L_{\rm X}$ and the optical/UV-to-X-ray spectral slope $α_{\rm OX}$) and various quasar properties (rest-UV luminosity $L_{\mathrm{2500\ \mathring{A}}}$, bolometric luminosity $L_{\rm bol}$, C IV blueshift, and infrared luminosity $L_{\rm IR}$). We find most $z>6.5$ quasars follow a similar $α_{\rm OX}-L_{\mathrm{2500\ \mathring{A}}}$ relation as $z\sim1-6$ quasars, but also display a large scatter. We find a potential correlation between $α_{\rm OX}$ and the C IV blueshift, suggesting a soft optical/UV-to-X-ray SED shape is frequently associated with fast disk winds. Furthermore, we analyze the X-ray spectrum of 11 quasars at $z>6.5$ with Chandra detection, and find the best-fit photon index $Γ$ is $2.41\pm0.27$, which is likely driven by high accretion rates of $z>6.5$ quasars. In addition, we find there are no significant correlations between either $L_{\rm X}$ and $L_{\rm IR}$, nor $L_{\rm bol}$ and $L_{\rm IR}$, suggesting no strong correlations between quasar luminosity and star formation luminosity for the most luminous quasars at $z>6.5$.

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arXiv2025

An XMM-Newton View of the ANdromeda Galaxy as Explored in a Legacy Survey (New-ANGELS) II: Luminosity Function of X-ray Sources

As part of the New-ANGELS program, we systematically investigate the X-ray luminosity functions (XLFs) of 4506 X-ray sources projected within a radius of 2.5 deg centering on M31. We construct XLFs for different regions in the disk and halo of M31, accounting for the incompleteness with an effective sensitivity map. Assuming that the halo regions contain (mostly) foreground stars and background active galactic nuclei, they are taken as "background" for deriving the XLFs of the sources in the disk. Through modeling XLFs, we decompose the X-ray sources into distinct populations for each region. We find that low-mass X-ray binaries are the dominant X-ray population throughout the disk of M31. The XLFs of M31 reveal a consistently lower integrated LMXB luminosity per stellar mass ($α_\mathrm{LMXB}$) compared to other galaxies, likely due to M31's prolonged period of quiescent star formation. Variations in the XLF shape and $α_\mathrm{LMXB}$ across different regions of M31 suggest that the relationship between integrated luminosity and stellar mass may vary within the galaxy. Additionally, the relatively low integrated luminosity observed in the inner-arm region provides crucial evidence for a rapid fading of M31's LMXBs around 1 Gyr, a finding consistent with recent observations of other nearby galaxies.

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arXiv2025

Probing the \ion{He}{2} re-Ionization ERa via Absorbing \ion{C}{4} Historical Yield (HIERACHY) IV: A complex redshifted absorption system intrinsic to quasar

High-resolution spectra provide a powerful tool in studying the associated absorption lines (AALs) in quasars. We present a case study of the quasar J014741-030247 at $z \sim$ 4.75, which hosts complex intrinsic absorption lines revealed by the high-resolution Magellan/MIKE spectrum obtained from the HIERACHY program. We focus on one of the strongest absorption systems ($z$ $\sim$ 4.7804) and determine the column densities of multiple ionization species. We find that the Apparent Optical Depth method may significantly underestimate the column densities of high ions. Decomposing the absorption into multiple components yields a better fit and reveals clear evidence of partial coverage. The variation in covering fractions among different ions suggests that high ions are distributed more extensively in this system. We estimate electron densities of different components ($630 - 4070 \ \mathrm{cm}^{-3}$), these are based on the column densities of \ion{Si}{2}* and \ion{C}{2}*. By combining these with the hydrogen number density and ionization parameter derived from photoionization modeling, we infer that the different components are located at distances of 2.3 to 9.5 kpc from the quasar. The derived $N_{\mathrm H} / n_{\mathrm e}$ and the partial coverage observed in low ions all require cloud sizes smaller than 1 pc, even down to 0.01 pc. Finally, the low kinetic luminosity of the gas ($< 0.5\% L_\mathrm{bol}$) indicates that it is insufficient to drive significant AGN feedback and may only suppress star formation via `multistage' mechanism.

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arXiv2025

Magnetic Reconnection as a Potential Driver of X-ray Variability in Active Galactic Nuclei

We present a systematic analysis on the X-ray variability in 13 bright quasars at z > 4.5, combining recent Swift observations from 2021 to 2023 and archival multi-epoch observations. Upper limits of the luminosity measurements were included in the analysis by using the Kaplan-Meier estimator method. It is found that the high-z quasars exhibit X-ray variability on both short-term (hours-to-days) and intermediate-term (weeks-to-months) timescales, with short-term variability dominating the overall variation. A linear correlation exists between the global mean ($μ_{\mathrm{L_{2-10\,keV}}}$) and standard deviation ($σ_{\mathrm{L_{2-10\,keV}}}$) of X-ray luminosities, which is independent of the X-ray photon index and optical-to-X-ray spectral slope. The localized stochastic magnetic reconnection mechanism is strongly favored, which can naturally lead to a scale-invariant power-law energy distribution and satisfactorily explain the correlation. The $σ$-$μ$ correlation parallels with the well-documented rms-flux relation of low-z active galactic nuclei (AGNs), implying the magnetic reconnection mechanism could drive short-timescale X-ray variability in both high- and low-z AGNs. The highest-z quasar in our sample, J142952+544717 (z = 6.18), shows a luminosity distribution extending to ${10}^{47}\ \rm{erg\ {s}^{-1}}$ with a not conspicuous median luminosity. On the other hand, J143023+420436 (z = 4.7), which hosts the most relativistic jet among known high-z blazars, is dominated in the high-luminosity regime (${10}^{47}\ \rm{erg\ {s}^{-1}}$ ), making it an ideal target for multi-wavelength follow-up observations. J090630+693030 is found to have a rest-frame period of 182.46 days and J143023+420436 has a period of 16.89 days, both could be explained by the global evolution of plasmoid chains, in which magnetic islands formed during reconnection may merge successively.

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arXiv2024

CO-CHANGES II: spatially resolved IRAM 30M CO line observations of 23 nearby edge-on spiral galaxies

Molecular gas, as the fuel for star formation, and its relationship with atomic gas are crucial for understanding how galaxies regulate their star forming (SF) activities. We conducted IRAM 30m observations of 23 nearby spiral galaxies from the CHANG-ES project to investigatet the distribution of molecular gas and the Kennicutt-Schmidt law. Combining these results with atomic gas masses from previous studies, we aim to investigate the scaling relations that connect the molecular and atomic gas masses with stellar masses and the baryonic Tully-Fisher relation. Based on spatially resolved observations of the three CO lines, we calculated the total molecular gas masses, the ratios between different CO lines, and derived physical parameters such as temperature and optical depth. The median line ratios for nuclear/disk regions are 8.6/6.1 (^{12}\mathrm{CO}/^{13}\mathrm{CO}\ J=1{-}0) and 0.53/0.39 (^{12}\mathrm{CO}\ J=2{-}1/J=1{-}0). Molecular gas mass derived from ^{13}\mathrm{CO} is correlated but systematically lower than that from ^{12}\mathrm{CO}. Most galaxies follow the spatially resolved SF scaling relation with a median gas depletion timescale of approximately 1 Gyr, while a few exhibit shorter timescales of approximately 0.1 Gyr. The molecular-to-atomic gas mass ratio correlates strongly with stellar mass, consistent with previous studies. Galaxies with lower stellar masses show an excess of atomic gas, indicating less efficient conversion to molecular gas. Most galaxies tightly follow the baryonic Tully-Fisher relation, but NGC 2992 and NGC 4594 deviate from the relation due to different physical factors. We find that the ratio of the cold gas (comprising molecular and atomic gas) to the total baryon mass decreases with the gravitational potential of the galaxy, as traced by rotation velocity, which could be due to gas consumption in SF or being heated to the hot phase.

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arXiv2024

CHANG-ES XXXV: Cosmic Ray Transport and Magnetic Field Structure of NGC 3556 at 3 GHz

Radio halos of edge-on galaxies are crucial for investigating cosmic ray propagation and magnetic field structures in galactic environments. We present VLA C-configuration S-band (2--4 GHz) observations of the spiral galaxy NGC 3556, a target from the Continuum Halos in Nearby Galaxies - an EVLA Survey (CHANG-ES). We estimate the thermal contribution to the radio emission from a combination of the H$α$ and mid-IR data, and employ Rotation Measure Synthesis to reveal the magnetic field structures. In our data, NGC 3556 exhibits a box-like radio halo extending nearly 7 kpc from the galactic plane. The scale height of the total S-band intensity in the halo is $1.68\pm 0.29$ kpc, while that of the non-thermal intensity is $1.93\pm 0.28$ kpc. Fitting the data to a 1-D cosmic-ray transport model, we find advection to describe the cosmic-ray propagation within the halo better than diffusion, with advection speeds of $245 \pm 15$ km s$^{-1}$ and $205 \pm 25$ km s$^{-1}$ above and below the disk, respectively. The magnetic field is detected patchily across the galaxy, displaying a toroidal configuration in the rotation measure map. The mean equipartition magnetic field strength is approximately $8.3\ μ$G in the disk and $4.5\ μ$G in the halo. In addition, a bubble-like structure extends nearly 3~kpc into the southern halo, aligned with the polarized intensity and H$α$ image, suggestive of superwinds generated by recent star formation feedback in the nuclear region.

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arXiv2024

Probing the He II re-Ionization ERa via Absorbing C IV Historical Yield (HIERACHY) II: Project Design, Current Status, and Examples of Initial Data Products

The He II reionization epoch is expected to take place at $z\sim3-5$. In this stage, the helium and metals in the inter-galactic medium (IGM) are further ionized with additional contributions from harder non-stellar sources, and some large-scale gravitationally bound systems approach virialization. The "Probing the He II re-Ionization ERa via Absorbing C IV Historical Yield (HIERACHY)" program utilizes high- and medium-resolution spectra of bright background quasars at $z\approx3.9-5.2$ to investigate Ly$α$, C IV, and other metal absorption lines during this epoch. Additionally, we employ narrow-band imaging to search for Ly$α$ emitters associated with C IV absorbers, alongside multi-wavelength observations to identify and study particularly intriguing cases. In this paper, we present the design of the HIERACHY program, its current status, major scientific goals, and examples of initial data products from completed Magellan/MIKE, MagE spectroscopy, and MDM imaging observations. We also provide a brief outlook on future multi-wavelength observations that may significantly impact the related science.

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arXiv2024

eDIG-CHANGES III: the lagging eDIG revealed by multi-slit spectroscopy of NGC 891

The kinematic information of the extraplanar diffuse ionized gas (eDIG) around galaxies provides clues to the origin of the gas. The eDIG-CHANGES project studies the physical and kinematic properties of the eDIG around the CHANG-ES sample of nearby edge-on disk galaxies. We use a novel multi-slit narrow-band spectroscopy technique to obtain the spatial distribution of spectral properties of the ionized gas around NGC 891, which is often regarded as an analog of the Milky Way. We developed specific data reduction procedures for the multi-slit narrow-band spectroscopy data taken with the MDM 2.4m telescope. The data presented in this paper covers the H$α$ and [N II]$λλ$6548,6583Åemission lines. The eDIG traced by the H$α$ and [N II] lines shows an obvious asymmetric morphology, being brighter in the northeastern part of the galactic disk and extending a few kpc above and below the disk. Global variations in the [N II]/H$α$ line ratio suggest additional heating mechanisms for the eDIG at large heights beyond photoionization. We also construct position-velocity (PV) diagrams of the eDIG based on our optical multi-slit spectroscopy data and compare them to similar PV diagrams constructed with the H I data. The dynamics of the two gas phases are generally consistent with each other. Modeling the rotation curves at different heights from the galactic mid-plane suggests a vertical negative gradient in turnover radius and maximum rotation velocity, with magnitudes of approximately $3$ kpc kpc$^{-1}$ and $22-25$ km s$^{-1}$ kpc$^{-1}$, respectively. Measured vertical gradients of the rotation curve parameters suggest significant differential rotation of the ionized gas in the halo, or often referred to as the lagging eDIG. Systematic study of the lagging eDIG in our eDIG-CHANGES project, will help us to better understand the dynamics of the ionized gas in the halo.

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arXiv2024

Optical observations of the Galactic SNR HB9 and H II region G159.2+3.3

Context. We present multi-wavelength observations of the Galactic SNR HB9 and the H II region G159.2+3.3 apparently projected nearby, in order to study their properties and potential physical connections. Results. HB9 is bright in $γ$-rays, but the $γ$-ray morphology is centrally filled and most of it is not clearly associated with the surrounding molecular clouds. There is a weak apparent connection of HB9 to the IR bright enclosing shell of G159.2+3.3 in $γ$-ray. The diffuse Balmer line has almost identical morphology as the radio emission in G159.2+3.3, indicating they two are thermal in origin. Using medium-band high-resolution optical spectra from selected regions of the southeast (SE) shell of HB9 and G159.2+3.3, we found the radial velocity dispersion of HB9 along the slit is significantly higher than the FWHM of the lines. In contrast, these two values are both smaller and comparable to each other in G159.2+3.3. This indicates that the gas in HB9 may have additional global motion triggered by the SNR shock. The [N II] $λ$6583A/H$α$ line ratio of both objects can be interpreted with photo-ionisation by hot stars or low velocity shocks, except for the post-shock region in the SE shell of HB9, where the elevated [N II]/H$α$ line ratio suggests contribution from shock ionisation. The measured electron density from the [S II] 6716/6730 line ratio is significantly lower in the brighter G159.2+3.3 compared to the SE shell of HB9. Conclusions. Our density estimate suggests that G159.2+3.3, although appearing brighter and more compact, is likely located at a much larger distance than HB9, so the two objects have no physical connections, unless the shock compressed gas in HB9 has a significantly lower filling factor.

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arXiv2024

A Spatially Resolved [CII] Survey of 31 $z\sim7$ Massive Galaxies Hosting Luminous Quasars

The [CII] 158 $μ$m emission line and the underlying far-infrared (FIR) dust continuum are important tracers for studying star formation and kinematic properties of early galaxies. We present a survey of the [CII] emission lines and FIR continua of 31 luminous quasars at $z>6.5$ using the Atacama Large Millimeter Array (ALMA) and the NOrthern Extended Millimeter Array (NOEMA) at sub-arcsec resolution. This survey more than doubles the number of quasars with [CII] and FIR observations at these redshifts and enables statistical studies of quasar host galaxies deep into the epoch of reionization. We detect [CII] emission in 27 quasar hosts with a luminosity range of $L_{\rm [CII]}=(0.3-5.5)\times10^9~L_\odot$ and detect the FIR continuum of 28 quasar hosts with a luminosity range of $L_{\rm FIR}=(0.5-13.0)\times10^{12}~L_\odot$. Both $L_{\rm [CII]}$ and $L_{\rm FIR}$ are correlated ($ρ\simeq0.4$) with the quasar bolometric luminosity, albeit with substantial scatter. The quasar hosts detected by ALMA are clearly resolved with a median diameter of $\sim$5 kpc. About 40% of the quasar host galaxies show a velocity gradient in [CII] emission, while the rest show either dispersion-dominated or disturbed kinematics. Basic estimates of the dynamical masses of the rotation-dominated host galaxies yield $M_{\rm dyn}=(0.1-7.5)\times10^{11}~M_\odot$. Considering our findings alongside those of literature studies, we found that the ratio between $M_{\rm BH}$ and $M_{\rm dyn}$ is about ten times higher than that of local $M_{\rm BH}-M_{\rm dyn}$ relation on average but with substantial scatter (the ratio difference ranging from $\sim$0.6 to 60) and large uncertainties.

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arXiv2024

eDIG-CHANGES II: Project Design and Initial Results on NGC 3556

The extraplanar diffuse ionized gas (eDIG) represents ionized gases traced by optical/UV lines beyond the stellar extent of galaxies. We herein introduce a novel multi-slit narrow-band spectroscopy method to conduct spatially resolved spectroscopy of the eDIG around a sample of nearby edge-on disk galaxies (eDIG-CHANGES). In this paper, we introduce the project design and major scientific goals, as well as a pilot study of NGC 3556 (M108). The eDIG is detected to a vertical extent of a few kpc above the disk, comparable to the X-ray and radio images. We do not see significant vertical variation of the [N II]/H$α$ line ratio. A rough examination of the pressure balance between different circum-galactic medium (CGM) phases indicates the magnetic field is in a rough pressure balance with the X-ray emitting hot gas, and may play an important role in the global motion of both the eDIG and the hot gas in the lower halo. At the location of an HST/COS observed UV bright background AGN $\sim29\rm~kpc$ from the center of NGC 3556, the magnetic pressure is much lower than that of the hot gas and the ionized gas traced by UV absorption lines, although the extrapolation of the pressure profiles may cause some biases in this comparison. By comparing the position-velocity diagrams of the optical and CO lines, we also find the dynamics of the two gas phases are consistent with each other, with no evidence of a global inflow/outflow and a maximum rotation velocity of $\sim150\rm~km~s^{-1}$.

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