Junqiang Ge

We investigate the relative importance of active galactic nucleus (AGN) feedback and environmental processes using a large sample of H i galaxies from the Arecibo Legacy Fast ALFA Survey (ALFALFA) and FAST All Sky H i Survey (FASHI) surveys. By applying the optical spectroscopy from Sloan Digital Sky Survey DR7/DR8 and the Dark Energy Spectroscopic Instrument survey, we analyse the gas content and physical properties of AGN-hosting galaxies in group environments. Our results show that AGN-hosting galaxies exhibit significantly suppressed star formation rates and H i gas fraction, approximately one order of magnitude lower than star-forming counterparts, regardless of their group-centric position. AGN-hosting satellites exhibit a significant and persistent deficit in both gas fraction and star formation rate relative to normal satellites without an AGN, even at the halo virial radius ( R / R ₁₈₀ ≈ 1). This suggests that cold gas depletion is primarily driven by internal AGN feedback before these galaxies experience intense environmental interactions. The relatively flat radial profiles of gas fraction and specific star formation rate further indicate that the evolution of AGN-hosting satellites is governed by internal physical processes rather than environmental interactions. Moreover, the apparent increase in H i gas at R / R ₁₈₀ < 0.3 is identified as an artifact of beam confusion. We conclude that for the AGN-hosting population, internal feedback is likely the prior quenching mechanism, while environmental effects act as a secondary, subsequent process.

The Tremaine-Weinberg (TW) method and its variations provide the most direct means to measure the pattern speeds of galactic bars. We establish a unifying framework by deriving an integral form of the continuity equation over an arbitrary closed loop. This naturally defines a local pattern speed for any chosen region in a galactic disk (including bars and spirals). We demonstrate that this intuitive formalism recovers all standard variants of the TW method as special cases corresponding to specific choices of the integration loop. In this paper, we validate this framework and demonstrate its diagnostic power. By applying it to a diverse set of test cases from the TNG50 simulation, including face-on prototype barred galaxies and highly constrained Mock Milky Way standard configurations, we show that this formalism accurately recovers both constant global pattern speeds and radially varying profiles. Rather than relying on rigid geometric approximations, our method naturally differentiates coherent solid-body rotators (bars) from spirals. Our results validate that this unified integral framework provides a robust, geometrically flexible, and practically extensible tool for decoding complex dynamics of galactic structures.

We developed a Python package GEHONG to mock the three-dimensional spectral datacube under the observation of an ideal telescope for the Integral Field Spectrograph of the Chinese Space Station Survey Telescope. This package can generate one-dimensional spectra corresponding to local physical properties at specific positions according to a series of two-dimensional distributions of physical parameters of target sources. In this way, it can produce a spatially resolved spectral cube of the target source. Two-dimensional distributions of physical parameters, including surface brightness, stellar population, and line-of-sight velocity, can be modeled using the parametric model or based on real observational data and numerical simulation data. For the generation of one-dimensional spectra, we have considered four types of spectra, including the stellar continuum spectra, ionized gas emission lines, Active Galactic Nucleus (AGN) spectra, and stellar spectra. That makes GEHONG able to mock various types of targets, including galaxies, AGNs, star clusters, and H II regions.

Context. We compare the photometric properties and specific star formation rate (sSFR) of classical- and pseudo-bulge galaxies with M_∗ ≥ 10^9.5 M_⊙ at 0.5 ≤ z < 1.0, selected from all five CANDELS fields. We also compare these properties of bulge galaxies at lower redshift selected from MaNGA survey in previous work. Aims. This paper aims to study the properties of galaxies with classical and pseudo-bulges at intermediate redshift, to compare the differences between different bulge types, and to understand the evolution of bulges with redshift. Methods. Galaxies are classified into classical bulge and pseudo-bulge samples according to the Sérsic index n of the bulge component based on results of two-component decomposition of galaxies, as well as the position of bulges on the Kormendy diagram. For the 105 classical bulge and 86 pseudo-bulge galaxies selected, we compare their size, luminosity, and sSFR of various components. Results. At a given stellar mass, most classical bulge galaxies have smaller effective radii, larger B/T, brighter and relatively larger bulges, and less active star formation than pseudo-bulge galaxies. In addition, the two types of galaxies have larger differences in sSFR at large radii than at the central region at both low- and mid-redshifts. Conclusions. The differences between the properties of the two types of bulge galaxies are generally smaller at mid-redshift than at low-redshift, indicating that they are evolving to more distinct populations towards the local universe. Bulge type is correlated with the properties of their outer disks, and the correlation is already present at redshifts as high as 0.5 < z < 1.

Context. Periodic quasi-stellar objects (QSOs) are considered as candidates of supermassive binary black hole (BBH) systems in galactic centers. The periodicity of their light curves can be interpreted as being due to the Doppler boosting caused by the rotation of the two black holes (BHs). Further confirmation of these candidates may require different lines of observational evidence. Aims. Assuming the Doopler boosting scenario, in this paper we investigate the (coherent) variations of broad emission lines (BELs) and continuum light curves for active BBH systems surrounded by a circumbinary broad-line region (cBLR) and focus on their dependence on the eccentric orbital configuration. Methods. We calculated the variation of continuum light according to the motion of BBHs on elliptical orbits, with simplified orbital orientation for demonstration, the Doppler enhanced or weakened photoionization of each BLR cloud by the central BBH sources and its variation by assuming a shifted Γ-distribution of BLR clouds for a simple BLR geometry, and finally obtain the coherent variation of the continuum and the BELs. Results. We find that the amplitude and variation pattern of the continuum light curves and the evolution of the BEL profiles both sensitively depend on the eccentric orbital configuration of BBH systems, especially when the eccentricity is high. If only the secondary BH is active, the variation amplitudes of continuum light curves and BELs both increase with increasing BBH inclination angles and orbital eccentricities, but decrease with increasing BBH mass ratio. If both BHs are active, the asymmetry in the ionization of BLR clouds at different areas caused by the Doppler boosting effect of the secondary BH is weakened due to that of the primary BH at the opposite direction, which leads to systematically smaller variation amplitudes of both continuum light curves and BELs compared with those in the cases where only secondary the BH is activated. Conclusions. The coherent variations of the BEL profiles with the continuum light for those periodic QSOs provide an important way to confirm the existence of BBHs in their center. Future joint analysis of the light curves and multi-epoch observed BEL profiles for periodic QSOs may lead to the identification of a number of BBH systems.

Quiescent galaxies generally possess denser cores than star-forming galaxies with similar mass. As a measurement of the core density, the central stellar mass surface density within a radius of 1 kpc (Σ₁) was thus suggested to be closely related to galaxy quenching. Massive star-forming galaxies with high Σ₁ do not fit into this picture. To understand the origin of such galaxies, we compare the spatially resolved stellar population and star formation properties of massive (>10^10.5 M _⊙) blue spiral galaxies with high and low Σ₁, divided by Σ₁ = 10^9.4 M _⊙ kpc⁻², based on the final release of MaNGA integral field unit data. We find that both high-Σ₁ and low-Σ₁ blue spirals show large diversities in stellar population and star formation properties. Despite the diversities, high-Σ₁ blue spirals are statistically different from the low-Σ₁ ones. Specifically, the radial profiles of the luminosity-weighted age and Mgb/〈Fe〉 show that high-Σ₁ blue spirals consist of a larger fraction of galaxies with younger and less α-element-enhanced centers than their low-Σ₁ counterparts, ∼55% versus ∼30%. The galaxies with younger centers mostly have higher central specific star formation rates, which still follow the spaxel-based star formation main-sequence relation. Examinations of the Hα velocity field and the optical structures suggest that galactic bars or galaxy interactions should be responsible for the rejuvenation of these galaxies. The remaining ∼45% of high-Σ₁ blue spirals are consistent with the inside-out growth scenario.

Cosmic hydrogen reionization and cosmic production of the first metals are major phase transitions of the Universe occurring during the first billion years after the Big Bang; however, these are still underexplored observationally. Using the JWST/NIRSpec prism spectroscopy, we report the discovery of a sub-L _* galaxy at z _spec = 8.1623 ± 0.0007, dubbed RX J2129–z8He II, via the detection of a series of strong rest-frame UV/optical nebular emission lines and the clear Lyman break. RX J2129–z8He II shows a pronounced UV continuum with an extremely steep (i.e., blue) spectral slope of β = − 2.53 − 0.07 + 0.06 , the steepest among all spectroscopically confirmed galaxies at z _spec ≳ 7, in support of its very hard ionizing spectrum that could lead to a significant leakage of its ionizing flux. Therefore, RX J2129–z8He II is representative of the key galaxy population driving the cosmic reionization. More importantly, we detect a strong He II λ1640 emission line in its spectrum, one of the highest redshifts at which such a line is robustly detected. Its high rest-frame equivalent width (EW = 21 ± 4 Å) and extreme flux ratios with respect to UV metal and Balmer lines raise the possibility that part of RX J2129–z8He II’s stellar population could be Pop III (Pop III)-like. Through careful photoionization modeling, we show that the physically calibrated phenomenological models of the ionizing spectra of Pop III stars with strong mass loss can successfully reproduce the emission line flux ratios observed in RX J2129–z8He II. Assuming the Eddington limit, the total mass of the Pop III stars within this system is estimated to be 7.8 ± 1.4 × 10⁵ M _⊙. To date, this galaxy presents the most compelling case in the early Universe where trace Pop III stars might coexist with metal-enriched populations.

Context. Periodic QSOs are considered as candidates of supermassive binary black hole (BBH) systems in galactic centers. Further confirmation of these candidates may require different lines of observational evidences. Aims. Assuming the Doopler boosting scenario, in this paper we investigate the (coherent) variations of both broad emission lines (BELs) and continuum light curves for active BBH systems surrounding by a circumbinary broad line region (cBLR) and focus on their dependence on the eccentric orbital configuration. Methods. We calculate the variation of continuum light and the Doppler enhanced/weakened photoionization of each BLR cloud according to the motion of BBHs in elliptical orbits, and finally obtain the coherent variation of the continuum and BELs. Results. We find that both the amplitude and variation pattern of the continuum light curves and the evolution of the BEL profiles sensitively depend on the eccentric orbital configuration of BBH systems. If only the secondary BH is active, both the variation amplitudes of continuum light curves and BELs increase with increasing BBH inclination angles and orbital eccentricities, but decrease with increasing BBH mass ratio. If both BHs are active, the asymmetry in the ionization of BLR clouds at different areas caused by the Doppler boosting effect of the secondary BH is weakened due to that of the primary BH at the opposite direction, which leads to systematically smaller variation amplitudes of both continuum light curves and BELs than the cases with only secondary BH activated. Conclusions. The coherent variations of the BEL profiles with the continuum light for those periodic QSOs provide an important way to confirm the existence of BBHs in their center. Future joint analysis of the light curves and multi-epoch observed BEL profiles for periodic QSOs may lead to the identification of a number of BBH systems.