arXiv subjects

Jian-Min Wang

Publications and source records attributed to Jian-Min Wang.

At least 37 records · Page 2Linked to original sources

arXiv2025

Little red dots as embryos of active galactic nuclei

As an unprecedented large population in the early universe, the JWST-discovered little red dots (LRDs) have garnered much attention for formation of massive black holes and galaxies, but their nature remains a mystery. The LRDs appearing as ``Chimeras" like both active galactic nuclei (AGNs) and galaxies have stimulated renewed interest in the roadmap of central massive black hole (cMBH) formation in AGNs. In this paper, we suggest that the LRDs contain $M_{\bullet}\lesssim 10^6\,M_{\odot}$ cMBHs as demonstrated by the Sołtan argument and there is a large population of stellar-mass black holes (sMBHs with total mass of $\mathscr{M}_{m_{\bullet}}$) embedded inside cMBH accretion disks (cMBH-disk) as motivated by anomalous reverberations of broad H$β$ line in local AGNs. This embryo structure of LRDs ($M_{\bullet}<\mathscr{M}_{m_{\bullet}}$) is formed as a consequence of gravitational collapse of primordial clouds. In this Chimera, accretion onto sMBHs powers the rest-frame optical continuum of the LRDs but the UV continuum is jointly contributed by slim parts of the cMBH-disks and nuclear starbursts in the core of collapsing clouds governing the appearance of the observed V-shaped spectral energy distributions (SEDs). Outflowing clumped-envelopes are unavoidably formed by radiation pressure leading to absorption features of the Balmer lines. The present model works very well for LRDs' SEDs and avoids the issues of overly massive cMBHs. Evolution of LRDs is briefly discussed including gravitational waves.

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arXiv2025

Detection of unexpected leading delays in broad Hβ line reverberations in the quasar PHL 1092

Delayed reverberations of broad emission lines in response to optical continuum variations have been widely observed in active galactic nuclei (AGNs). They serve as a powerful tool for probing inner structures of AGNs and estimating the masses of supermassive black holes (SMBHs). The delays exhibit a strong correlation with approximately the square root of the optical luminosity - a relationship known as the "standard structure" of AGN broad-line regions (BLRs). Here, we report the discovery of leading delays in Hβ line reverberations (LDRs) in the quasar PHL 1092 preceding variations of the 5100 Å continuum by 17-57 days, based on our eight-year continuous campaign of reverberation mapping of super Eddington AGNs. The LDRs suggest that the 5100 Å continuum regions are so extensive that they are larger than the BLRs. This phenomenon not only fundamentally disrupts the well-established BLR size-luminosity relation but also violates the principle of causality. This unprecedented LDRs challenge the conventional methods for estimating SMBH mass as well as the standard model of AGNs. A preferred scenario to explain the LDRs is that the SMBH-disk contains a population of accreting stellar-mass black holes (sMBHs) as extra heating sources of the disk. Consequently, continuum regions of the disk are efficiently stretched so that the 5100 Å regions exceed the BLRs, yielding the observed LDRs. Generally, sMBH activities there could provide new physics of AGN phenomena, which can be tested by LIGO, LISA/Tianqin and ET detections of gravitational waves from sMBH mergers.

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arXiv2025

AGN STORM 2. XI. Spectroscopic reverberation mapping of the hot dust in Mrk 817

The AGN Space Telescope and Optical Reverberation Mapping 2 (STORM 2) campaign targeted Mrk 817 with intensive multi-wavelength monitoring and found its soft X-ray emission to be strongly absorbed. We present results from 157 near-IR spectra with an average cadence of a few days. Whereas the hot dust reverberation signal as tracked by the continuum flux does not have a clear response, we recover a dust reverberation radius of $\sim 90$ light-days from the blackbody dust temperature light-curve. This radius is consistent with previous photometric reverberation mapping results when Mrk 817 was in an unobscured state. The heating/cooling process we observe indicates that the inner limit of the dusty torus is set by a process other than sublimation, rendering it a luminosity-invariant `dusty wall' of a carbonaceous composition. Assuming thermal equilibrium for dust optically thick to the incident radiation, we derive a luminosity of $\sim 6 \times 10^{44}$ erg s$^{-1}$ for the source heating it. This luminosity is similar to that of the obscured spectral energy distribution, assuming a disk with an Eddington accretion rate of $\dot{m} \sim 0.2$. Alternatively, the dust is illuminated by an unobscured lower luminosity disk with $\dot{m} \sim 0.1$, which permits the UV/optical continuum lags in the high-obscuration state to be dominated by diffuse emission from the broad-line region. Finally, we find hot dust extended on scales $> 140-350$ pc, associated with the rotating disk of ionised gas we observe in spatially-resolved [SIII] $λ9531$ images. Its likely origin is in the compact bulge of the barred spiral host galaxy, where it is heated by a nuclear starburst.

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arXiv2025

Spectroscopic Reverberation Mapping for SARM: The Case of Mrk 1048 and Mrk 618

Robust extragalactic distance measurements are crucial for resolving the persistent discrepancy in the value of the Hubble constant (H$_0$)). Active Galactic Nuclei (AGNs), through their compact and variable broad-line regions (BLRs), enable the determination of geometric distances when reverberation mapping (RM) is combined with spectroastrometry(SA). We report results from a spectroscopic RM campaign (October 2022 to March 2023) targeting two narrow-line Seyfert 1 galaxies, Mrk 1048 and Mrk 618, using 3.6-m DOT and 2-m HCT. High-cadence spectro-photometric monitoring was carried out using onboard instruments such as ADFOSC, HFOSC, and TANSPEC, resulting in well-sampled continuum and emission line light curves. The observed fractional variability ($F_{\mathrm{var}}$) ranged from 4% to 14% across the $g$-band, H$β$, and H$α$ light curves. The time lags were measured using the interpolated cross-correlation function (ICCF), PyI$^{2}$CCF, and \textsc{JAVELIN} methods. In the rest frame, the ICCF analysis yields H$β$ lags of $10.5^{+2.6}_{-4.2}$ days for Mrk 1048 and $10.2^{+3.4}_{-2.9}$ days for Mrk 618, while the corresponding H$α$ lags are $18.7^{+5.3}_{-5.4}$ and $14.4^{+4.6}_{-10.5}$ days, respectively. The emission-line widths, measured from the rms spectra using $σ_{\mathrm{line}}$, give virial black hole mass estimates of $6.3^{+2.0}_{-2.1} \times 10^7\,M_\odot$ for Mrk 1048 and $1.2^{+0.4}_{-0.6} \times 10^7\,M_\odot$ for Mrk 618. These results will serve as a basis for absolute geometric distance calibration when combined with VLTI/GRAVITY spectro-astrometric measurements, thereby contributing to the development of AGNs as standardizable cosmological probes.

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arXiv2025

Fermi detection of $γ$-rays from the radio-quiet Seyfert galaxy NGC 3281

We report the detection of significant $γ$-ray emission with $\it Fermi$-LAT from the radio-quiet Seyfert 2 galaxy NGC 3281, with a luminosity of $5.9\,(\pm 1.7)\times10^{41}\rm\,erg\,s^{-1}$ at a significance of $6.22\,σ$ (TS = $42.81$). The power-law photon index is $2.61~(\pm 0.24)$, indicative of a soft spectrum. The star formation activity in NGC 3281 is insufficient to explain its $γ$-ray luminosity based on the empirical relation between the infrared and $γ$-ray luminosities observed in other sources. The multiwavelength spectrum can be explained as due to inverse Compton scattering by relativistic electrons in the corona or jet of seed photons from the corona, disk and torus. The source is Compton-thick and attenuation of GeV photons due to pair production in the corona is nonnegligible (with an optical depth of about 10). The intrinsic $γ$-ray luminosity is inferred to be $3.4\,\times10^{42}$ and $2.2\,\times10^{41}\rm\,erg\,s^{-1}$ for the corona and jet model, respectively. The observed $γ$-ray and radio luminosities is roughly consistent with the known correlation between the two quantities, among the lowest luminosity regime. The jet origin is valid only if the radio emission is dominated by the jet.

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arXiv2025

Continuum Reverberation Mapping of Accretion Disks Surrounding Supermassive Black Hole Binaries: Observational Signatures

It has remained challenging to reliably identify sub-parsec supermassive black hole binaries (SMBHBs), despite them being expected to be ubiquitous. We propose a new method using multi-band continuum reverberation mapping to identify low-mass-ratio SMBHBs in active galactic nuclei. The basic principle is that, due to the presence of a low-density cavity between the mini-disks and the circumbinary disk, the continuum emissions show a deficit at certain wavelengths, leading to a distinguishing feature in the relation between the inter-band time lag and wavelengths $τ(λ)$. Specifically, the relation appears flat at short wavelengths because of the truncated sizes of the mini-disks and transits to a power law $λ^{4/3}$ at long wavelength stemming from the circumbinary disk. This transition feature is distinct from the uniform relation $λ^{4/3}$ of the standard accretion disk around a single black hole. Using the lamp-post scenario and assuming that only the secondary black hole is active in a low-mass-ratio SMBHB, we design a simple continuum reverberation model to calculate the transfer function of the accretion disks and the resulting $τ(λ)$ relations for various SMBHB orbital parameters. The transition wavelength typically can lie at UV/optical bands, mainly depending on the total mass and orbital separation of the SMBHB. We apply our SMBHB model to the intensive multiwavelength monitoring data of the SMBHB candidate PG1302-102 and find that the SMBHB model can reproduce the inter-band time lags. Remarkably, the inferred total mass and orbital period from the SMBHB fitting are consistent with values derived from other independent methods.

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arXiv2025

Spectroastrometry and Reverberation Mapping of Active Galactic Nuclei. II. Measuring Geometric Distances and Black Hole Masses of Four Nearby Quasars

The geometric distances of active galactic nuclei (AGNs) are challenging to measure because of their exceptionally compact structure yet vast cosmic distances. A combination of spectroastrometry and reverberation mapping (SARM) of broad-line regions (BLRs) constitutes a novel means to probe the geometric distance of AGNs, which has recently become practically feasible owing to successful interferometric observations with VLTI/GRAVITY. Here, we perform SARM analysis of four nearby quasars: Mrk 509, PDS 456, 3C 273, and NGC 3783. Results for the former two are reported for the first time and the latter two are revisited using our improved BLR dynamical modeling that includes the radial-dependent responsivity of BLRs. This allows us to self-consistently account for the emissivity weighting of the BLR in spectroastrometry and responsivity weighting in reverberation mapping. We obtain angular-diameter distances of the four quasars, from which we derive a Hubble constant of $H_0=69_{-10}^{+12}\,\rm km\,s^{-1}\,Mpc^{-1}$. Although this constitutes a large uncertainty for a measurement of $H_0$, it is anticipated that the precision will improve to a competitive level once a greater number of AGNs are accessible following the upgrade of GRAVITY in the near future. From SARM analysis, the black hole masses of the four quasars are also measured with the statistical uncertainty ranging from 0.06 to 0.23 dex, consistent with the correlations between black hole masses and properties of the host bulges.

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arXiv2025

Fermi detection of gamma-ray Emission from the Hot Coronae of Radio-quiet Active Galactic Nuclei

Relativistic jets around supermassive black holes (SMBHs) are well-known powerful $γ$-ray emitters. In absence of the jets in radio-quiet active galactic nuclei (AGNs), how the SMBHs work in $γ$-ray bands is still unknown despite of great observational efforts made in the last 3 decades. Considering the previous efforts, we carefully select an AGN sample composed of 37 nearby Seyfert galaxies with ultra-hard X-rays for the goals of $γ$-ray detections by excluding all potential contamination in this band. Adopting a stacking technique, here we report the significant $γ$-ray detection (${\rm TS}=30.6$, or $5.2\,σ$) from the sample using 15-year Fermi-Large Area Telescope (LAT) observation. We find an average $γ$-ray luminosity of the sample as $(1.5\pm1.0)\times10^{40}{\,\rm erg\,s^{-1}}$ at energies from 1-300\,GeV. Limited by the well-known pair production from the interaction of $γ$-rays with low energy photons, $\gtrsim$ several GeV $γ$-rays are found to originate from an extended corona ($\sim 2.7\times 10^6\,R_{\rm g}$), whereas the canonical much more compact X-ray corona ($\sim 10\,R_{\rm g}$) is responsible for 1 to several GeV $γ$-rays. The finding of the compact region lends to strong supports to the long-time theoretical expectations, but the extended corona is beyond all the existing models. One promising scenario is that the electron-positron pairs produced in the compact X-ray corona would expand as fireball, similar to that in $γ$-ray bursts, forming the structure of extended corona.

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arXiv2025

A Composite Broad-Line Region in SDSS J1609+4902: a Double-Peaked Disk component and a Gaussian Component

The profiles of broad emission lines in active galactic nuclei (AGNs) provide critical insights into the geometry and kinematics of the broad-line region (BLR), which in turn influence the uncertainties in estimating the masses of central supermassive black holes. In this study, we report the discovery of a low-luminosity AGN, SDSS J1609+4902, in which the H$α$ line exhibits two distinct BLR components: a Gaussian component and an extremely broad double-peaked component. Follow-up observations conducted at the Lijiang Observatory in 2025 reveal that the line profile remains roughly unchanged, suggesting that this BLR structure may remain stable over a timescale of $\sim$10 years. We find that the size of the central Gaussian (Full Width at Half Maximum, FWHM$\sim 3000\,{\rm km\, s^{-1}}$) component is consistent with the classical reverberation mapping correlation. In contrast, the asymmetric double-peaked wing (FWHM$\sim 23,000\,{\rm km\, s^{-1}}$) likely originates from a disk-like BLR with an inner radius of approximately 70 gravitational radii. These results provide new constraints on the structure and dynamics of BLRs in AGNs and highlight the potential for long-term stability in such systems.

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arXiv2025

Numerical modeling the mass feeding rates onto accretion-modified stars embedded within AGN disks

Accretion disks surrounding supermassive black holes can potentially form stars within the self-gravitating region. These stars undergo high accretion rates because of the dense environment of the active galactic nuclei (AGN) accretion disk. The vorticity of the AGN disk may influence the ultimate mass feeding rate toward the star. In our study, we simulate mass feeding rates onto stars at different AGN disk thicknesses through 3D numerical models to explore the relationship between feeding rates and the thermal mass of the star ($q_{\rm th}$), defined as the ratio of the star's Bondi radius to the AGN disk thickness. Our findings indicate that disk shearing with angular momentum can notably decrease the feeding rate, and we provide an approximate formula that links the feeding rate based on the angular momentum of the surrounding gas and the thermal mass $q_{\rm th}$. Lastly, we examine the potential feedback of the rapidly accreting stars on the AGN disk and their subsequent evolution.

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arXiv2025

Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. XII. Reverberation Mapping Results for 15 PG Quasars from a Long-Duration High-Cadence Campaign

We present the first results from long-term high-cadence spectroscopic monitoring of 15 PG quasars with relatively strong Fe II emission as a part of a broader reverberation mapping campaign performed with the Calar Alto Observatory 2.2m telescope. The $V$-band, 5100 Å continuum, and H$β$ broad emission line light curves were measured for a set of quasars for between dozens to more than a hundred epochs from May 2017 to July 2020. Accurate time lags between the variations of the H$β$ broad line fluxes and the optical continuum strength are obtained for all 15 quasars, ranging from $17.0_{-3.2}^{+2.5}$ to $95.9_{-23.9}^{+7.1}$ days in the rest frame. The virial masses of the central supermassive black holes are derived for all 15 quasars, ranging between $0.50_{-0.19}^{+0.18}$ and $19.17_{-2.73}^{+2.98}$ in units of $10^7 M_\odot$. For 11 of the objects in our sample, this is the first reverberation analysis published. Of the rest, two objects have been the subject of previous reverberation studies, but we determine time lags for these that are only half as long as found in the earlier investigations, which had only been able to sample much more sparsely. The remaining two objects have previously been monitored with high sampling rates. Our results here are consistent with the earlier findings in the sense that the time lag and the line width vary inversely consistent with virialization.

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arXiv2025

Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. XIV. Long-Duration High-Cadence Reverberation Mapping Results for 11 PG Quasars

We report the results of a long-duration high-cadence reverberation mapping campaign of a second batch of 11 PG quasars using the 2.2m telescope at the Calar Alto Observatory. This follows a similar earlier study of another sample of 15 objects reported by Hu et al. (2021). Among the 11 PG quasars, 8 objects have the H$β$ time lags measured for the first time, while the other 3 objects were observed in previous campaigns, but only had highly uncertain H$β$-lag measurements. Long-term light curves are presented of photometric $V$-band, spectroscopic 5100 Å continuum, and the H$β$ emission line, lasting for $\sim$3--6 years with a cadence of $\sim$6--14 days. Accurate H$β$ time lags ranging from $\sim$20 to 150 days in the rest frame are obtained. The estimated virial masses of the central supermassive black holes range from $\sim$(3--300)$\times10^7 M_\odot$. Combining these results with those reported in Hu et al. (2021), we now have 26 PG quasars, with representative properties, having reliable H$β$ time-lag measurements from our long-duration high-cadence campaign. A tentative fit to the relation between the H$β$ time lag and the continuum luminosity for these 26 objects gives a slope of 0.53.

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arXiv2025

Monitoring AGNs with H$β$ Asymmetry. V. Long-term Variation and Evolution of the Broad H$β$ Emission-Line Profiles

The physical origins of the diverse emission-line asymmetries observed in the spectra of active galactic nuclei (AGNs) remain incompletely understood. Monitoring the temporal variations of line profiles offers a promising approach to investigating the underlying physics. In this study, we present an analysis of the broad H$β$ emission line profiles of eight AGNs observed from the end of 2016 to May 2023 as part of the reverberation mapping campaign titled "Monitoring AGNs with H$β$ Asymmetry" (MAHA), utilizing data obtained from the Wyoming Infrared Observatory (WIRO) 2.3-meter telescope. We measure the temporal variations of line asymmetry, width, and central velocity shift for the eight objects. Our findings reveal that the variation in asymmetry is positively correlated with H$β$ flux in five of the eight objects, while the remaining objects exhibit negative or complex correlations. Furthermore, we observe anti-correlations between line width and H$β$ flux for most objects, indicating the presence of the "breathing" phenomenon in their H$β$ emission lines. In contrast, two objects demonstrate an "anti-breathing" phenomenon or complex behavior. We discuss the physical origins of the temporal variations in line profiles and propose the possibility of decomposing the variations in H$β$ asymmetry and width into components: one that corresponds to short-term variations in H$β$ flux and another that reflects long-term variations in continuum light curves, perhaps driven by radiation pressure.

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arXiv2025

New theoretical Fe II templates for bright quasars

We present a set of new theoretical Fe II templates for bright quasars covering a wavelength range of 1000-10000 Å\, based on the recent atomic database available in the C23.00 version of the photoionization code CLOUDY. We compute a grid of models for a range of incident photon flux, gas density, and multiple microturbulence velocities. We examine the equivalent widths (EWs) and the ratios of Fe II emission over various wavebands and compare them with observations. Our key results are: (1) The flux generated from the shielded side of the cloud is insufficient to describe the measured Fe II emission. (2) Despite using the newest atomic data we still confirm the long-standing problem that the predicted Fe II UV/optical ratio is significantly larger than that observed in the AGN spectra. (3) The Fe II UV/optical ratio is not significantly affected by the variations in the microturbulence and the metallicity. (4) The microturbulence can create an additional apparent velocity shift of up to 1000 km/s in the spectra. (5) There is no Fe II template based on a single set of physical parameters that can fit the observed UV to optical Fe II emission spectra. We shortly discuss the most likely effects responsible for the Fe II UV/optical mismatch problem: the assumption of the constant density clouds and the heating mechanism for Fe II emitting clouds.

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arXiv2025

A New Interpretation for the Hot Corona in Active Galactic Nuclei

This work attempts to provide a new interpretation for the hot corona in active galactic nuclei (AGNs). A thin parabolic magnetic reconnection layer, anchored at the innermost disk and extending along the boundary of the magnetic tower for a few tens of gravitational radii, serves as a hard-X-ray source above the disk. Within this reconnection layer, the tearing instability leads to the formation of a chain of plasmoids, which contain relativistic electrons that generate X-ray radiation through inverse-Compton (IC) scattering of soft photons emitted by the accretion disk. Based on previous theoretical works and numerical simulations, we develop a heuristic framework to parameterize the geometry and magnetization of the reconnection layer, as well as to compute both the power of the IC-scattering radiation and the height of the reconnection layer. Our model allows for a quantitative investigation of the relation between the height of the corona and the X-ray radiation luminosity, which can be directly compared against the observed relation from X-ray reverberation mapping of individual AGNs. The theoretical results are in good agreement with the observations of IRAS 13224-3809, indicating the validation of our model.

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arXiv2024

Bulge Oscillation Driven by Outflows of Active Galactic Nuclei. I. Fast Outflow Case

There is growing evidence for star formation inside outflows of active galactic nuclei (AGNs). The formed stars are injected into bulges and give rise to perturbation of bulges. In this paper, we investigate the issues of non-rotating, spherically symmetric bulges under the perturbation of fast, massive outflows with stars formed inside. We show that the potential perturbation of outflows together with injection and dynamical friction of these stars could drive bulge oscillations. Still, we find non-zero radial velocity of bulges will be driven by the episodic outflows of AGNs and after the AGN quenched, the radial velocity will tend to zero within a timescale $\simτ_{\rm AGN}$, which is the AGN's lifetime. For some typical values of bulges and AGNs, we find the expansion and contraction velocities are of a few $10\,\rm km\,s^{-1}$ for $10^{10}\,M_\odot$ bulges and mass outflowing rate $500\,M_\odot/\rm yr$, which would give observational signatures.

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arXiv2024

Warped accretion disks and quasars with episodic periodicity of long-term variations

It has been found that some quasars are undergoing quasi-periodic variations (most of them with damped amplitudes) in optical bands from long-term monitoring campaigns, but how to explain the origin of such light curve variations still remains an open question. In this paper, we use the warped accretion disks model to explain the quasi-periodical variations. This model employs a free-bending wave traveling in an accretion disk which causes the orientation of the central part of the disk to oscillate from the line of sight, resulting in a quasi-periodical variation. We numerically solve the governing equation of warp propagation and calculate the simulated R-band light curves, finding that the periodical light curves generated by this model have damped amplitudes. To compare with observations, we select SDSSJ134820.42+194831.5 as a preliminary example from a sample of periodic quasar candidates by combining CRTS with other public survey data, and fitted its light curve with different observational angles. Our result gives a reduced $χ^{2}\simeq 2.4$, implying that the model might give insights to future application of warped disk model.

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arXiv2024

Radial-dependent Responsivity of Broad-line Regions in Active Galactic Nuclei: Observational Consequences for Reverberation Mapping and Black Hole Mass Measurements

The reverberation mapping (RM) technique has seen wide applications in probing geometry and kinematics of broad-line regions (BLRs) and measuring masses of supermassive black holes (SMBHs) in active galactic nuclei. However, the key quantities in RM analysis like emissivity, responsivity, transfer functions, and mean and root-mean-square (RMS) spectra are fragmentally defined in the literature and largely lack a unified formulation. Here, we establish a rigorous framework for BLR RM and include a locally dependent responsivity according to photoionization calculations. The mean and RMS spectra are analytically expressed with emissivity- and responsivity-weighted transfer functions, respectively. We demonstrate that the RMS spectrum is proportional to the responsivity-weighted transfer function only when the continuum variation timescale is much longer than the typical extension in time delay of the BLR, otherwise, biases arise in the obtained RMS line widths. The long-standing phenomenon as to the different shapes between mean and RMS spectra can be explained by a radial-increasing responsivity of BLRs. The debate on the choice of emission line widths for SMBH mass measurements is explored and the virial factors are suggested to also depend on the luminosity states, in addition to the geometry and kinematics of BLRs.

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