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SDSS J083942.11+380526.3 ($z=2.315$) is a FeLoBAL quasar that exhibits visible Balmer absorption lines (H$\alpha$), implying a significant $n=2$ population. The quasar also shows an array of absorption lines, including \oi, \niii, \feii, \mgii, \aliii\, to \civ\ and \nv. The high-ionization absorption lines such as \civ\ and \siiv\ are revealed by slightly blueshifted BAL troughs. The resonance doublets such as \mgii\ and \aliii\ are saturated but did not reached zero intensity which indicates that the BLR is partially covered. Overall, however, the absorption is predominantly from low-ionization \feii\ lines, emitted from ground and excited states up to at least 3.814 eV. This implies that the absorbing gas spans the hydrogen ionization front and extends into the partially ionized zone where neutral hydrogen is certainly present. Notably, the hydrogen line spectrum of the quasar shows no signature of expected Ly$\alpha$ absorption. Instead, the line spectrum shows an unusual Ly$\alpha$ emission characterized by a fully filled emission line spectrum which is a composite of a strong narrow core superposed on a weak broad base. Taking into account the effect of partial covering to BLR, we have extracted a strong DLA trough in Ly$\alpha$ emission region. To fit the spectrum, we performed photoionized model calculations and compared them to the observations. We found that photoionization modeling using CLOUDY can successfully reproduce the main characteristics of the quasar spectrum, and the predicted neutral hydrogen column density arising from the clouds responsible for the low-ionization absorption provides a good match to the extracted DLA trough. This indicates that both the DLA and the low-ionization absorption arise from the same medium that is roughly collocated with the dusty torus., Comment: 18 pages, 7 figures, accepted for publication in MNRAS

We present a comprehensive study of Ultraluminous Infrared Galaxies (ULIRGs), leveraging data from the IRAS Faint Source Catalogue (FSC) and the spectroscopic catalog in the Sloan Digital Sky Survey (SDSS) DR16. Our meticulous cross-matching technique significantly enhances the reliability of ULIRG identification, resulting in the identification of 283 reliable ULIRGs, including 102 new detections, while discarding 120 previously reported false sources. Covering a redshift range of $z = 0.018 - 0.996$, with a median redshift of $\bar{z} = 0.259$, our uniform sample reveals apparent interaction features in approximately 40\% of ULIRGs, increasing to 92\% for those with $z < 0.1$. Through optical spectra analysis, it is indicated that over 58\% of ULIRGs host an AGN, which is twice as high as the detections based solely on infrared colors. Moreover, a pronounced excess of radio emissions associated with AGN activity results in a steeper radio-far-infrared correlation. Notably, Type I ULIRGs exhibit properties similar to those of narrow-line Seyfert 1 galaxies (NLS1s), with an elevated incidence rate of \ion{Mg}{2} BALs (16.7\%), surpassing that of typical optically selected quasars by over tenfold, consistent with current evolutionary models. We anticipate that forthcoming telescopes such as the China Space Station Telescope (CSST) and Leighton Chajnantor Telescope (LCT) will provide deeper insights into ULIRG morphology, dust distribution, molecular gas, and AGN activity., Comment: Accepted for publication in ApJS, 33 pages, 13 figures, and 1 table

Accurate photometric redshift (photo-$z$) estimation requires support from multi-band observational data. However, in the actual process of astronomical observations and data processing, some sources may have missing observational data in certain bands for various reasons. This could greatly affect the accuracy and reliability of photo-$z$ estimation for these sources, and even render some estimation methods unusable. The same situation may exist for the upcoming Chinese Space Station Telescope (CSST). In this study, we employ a deep learning method called Generative Adversarial Imputation Networks (GAIN) to impute the missing photometric data in CSST, aiming to reduce the impact of data missing on photo-$z$ estimation and improve estimation accuracy. Our results demonstrate that using the GAIN technique can effectively fill in the missing photometric data in CSST. Particularly, when the data missing rate is below 30\%, the imputation of photometric data exhibits high accuracy, with higher accuracy in the $g$, $r$, $i$, $z$, and $y$ bands compared to the $NUV$ and $u$ bands. After filling in the missing values, the quality of photo-$z$ estimation obtained by the widely used Easy and Accurate Zphot from Yale (EAZY) software is notably enhanced. Evaluation metrics for assessing the quality of photo-$z$ estimation, including the catastrophic outlier fraction ($f_{out}$), the normalized median absolute deviation ($\rm {\sigma_{NMAD}}$), and the bias of photometric redshift ($bias$), all show some degree of improvement. Our research will help maximize the utilization of observational data and provide a new method for handling sample missing values for applications that require complete photometry data to produce results.

The particle acceleration of blazar jets is crucial to high-energy astrophysics, yet the acceleration mechanism division in blazar subclasses and the underlying nature of these mechanisms remain elusive. In this work, we utilized the synchrotron spectral information (synchrotron peak frequency, $\log \nu_{\rm sy}$, and corresponding curvature, $b_{\rm sy}$) of 2705 blazars from the literature and studied the subject of particle acceleration in blazar jets by analysing the correlation between $\log \nu_{\rm sy}$ and $1/b_{\rm sy}$. Our results suggested that the entire sample follows an energy-dependent probability acceleration (EDPA). Specifically, the low inverse Compton peak sources (LCPs) follow the mechanism that fluctuations of fractional gain acceleration (FFGA), while the high inverse Compton peak sources (HCPs) follow an acceleration mechanism of EDPA. Our results indicated that the separation between LCPs and HCPs results from the electron peak Lorentz factor ($\gamma_{\rm p}$), and the differentiation should originate from different acceleration mechanisms. Moreover, our study revealed a transition in the acceleration mechanism from FFGA to EDPA around $\log \nu_{\rm sy} \sim 15$ through a detailed analysis of binned-$\log \nu_{\rm sy}$. The mechanism of FFGA dominates the particle acceleration in LCP jets because of stronger jets and the EDPA dominates the particle energy gain in the HCPs due to a more efficient acceleration process., Comment: Accepted to ApJ

Accurate estimation of photometric redshifts (photo-$z$) is crucial in studies of both galaxy evolution and cosmology using current and future large sky surveys. In this study, we employ Random Forest (RF), a machine learning algorithm, to estimate photo-$z$ and investigate the systematic uncertainties affecting the results. Using galaxy flux and color as input features, we construct a mapping between input features and redshift by using a training set of simulated data, generated from the Hubble Space Telescope Advanced Camera for Surveys (HST-ACS) and COSMOS catalogue, with the expected instrumental effects of the planned China Space Station Telescope (CSST). To improve the accuracy and confidence of predictions, we incorporate inverse variance weighting and perturb the catalog using input feature errors. Our results show that weighted RF can achieve a photo-$z$ accuracy of $\rm \sigma_{NMAD}=0.025$ and an outlier fraction of $\rm \eta=2.045\%$, significantly better than the values of $\rm \sigma_{NMAD}=0.043$ and $\rm \eta=6.45\%$ obtained by the widely used Easy and Accurate Zphot from Yale (EAZY) software which uses template-fitting method. Furthermore, we have calculated the importance of each input feature for different redshift ranges and found that the most important input features reflect the approximate position of the break features in galaxy spectra, demonstrating the algorithm's ability to extract physical information from data. Additionally, we have established confidence indices and error bars for each prediction value based on the shape of the redshift probability distribution function, suggesting that screening sources with high confidence can further reduce the outlier fraction.

In this paper, we study Chinese Spelling Correction (CSC) as a joint decision made by two separate models: a language model and an error model. Through empirical analysis, we find that fine-tuning BERT tends to over-fit the error model while under-fit the language model, resulting in poor generalization to out-of-distribution error patterns. Given that BERT is the backbone of most CSC models, this phenomenon has a significant negative impact. To address this issue, we are releasing a multi-domain benchmark LEMON, with higher quality and diversity than existing benchmarks, to allow a comprehensive assessment of the open domain generalization of CSC models. Then, we demonstrate that a very simple strategy, randomly masking 20\% non-error tokens from the input sequence during fine-tuning is sufficient for learning a much better language model without sacrificing the error model. This technique can be applied to any model architecture and achieves new state-of-the-art results on SIGHAN, ECSpell, and LEMON., Comment: Accepted by ACL'2023

Observational searches for intermediate-mass black holes (IMBHs; $10^2 - 10^6$ $M_\odot$) include relatively isolated dwarf galaxies. For those that host active galactic nuclei (AGNs), the IMBH nature may be discerned through the accretion - jet activity. We present radio observations of four AGN-hosting dwarf galaxies (which potentially harbor IMBHs). Very large array (VLA) observations indicate steep spectra (indices of $-$0.63 to $-$1.05) between 1.4 and 9 GHz. A comparison with the 9 GHz in-band spectral index however shows a steepening for GH047 and GH158 (implying older/relic emission) and flattening for GH106 and GH163 (implying recent activity). Overlapping emission regions in the VLA 1.4 GHz and our very long baseline array (VLBA) 1.5 GHz observations, and possibly symmetric pc-scale extensions are consistent with recent activity in the latter two. Using the compact VLBA radio luminosity, X-ray luminosity (probing the accretion activity) and the black hole masses, all AGNs are found to lie on the empirical fundamental plane relation. The four AGN are radio quiet with relatively higher Eddington ratios ($0.04 - 0.32$) and resemble the X-ray binaries during spectral state transitions that entail an outflow ejection. Furthermore, the radio to X-ray luminosity ratio $\log{R_\mathrm{X}}$ of $-3.9$ to $-5.6$ in these four sources support the scenarios including corona mass ejection from accretion disk and wind activity. The growth to kpc-scales likely proceeds along a trajectory similar to young AGNs and peaked spectrum sources. The above complex clues can thus aid in the detection and monitoring of IMBHs in the nearby Universe., Comment: 21 pages, 3 figures, 5 tabels, accepted for publication in ApJ

It is known that the blazar jet emissions are dominated by non-thermal radiation while the accretion disk jets are normally dominated by thermal emission. In this work, our aim is to study the connection between the two types of emission by investigating the correlation between the blazar emission line intensity property, which embodies the nature of accretion disk, and the $\gamma$-ray flux property, which is the representative of jet emission. We compiled a sample of 656 blazars with available emission line equivalent widths ($EW$), the GeV $\gamma$-ray flux, and the SED information from the literature. In this work, we found 55 previous BCUs are now identified as FSRQs, and found 52 Changing-look blazars based on their $EW$ and 45 of them are newly confirmed. These Changing-look blazars have a larger accretion ratio (${\dot M}/{\dot M}_{\rm Edd}$) than BL Lac objects. In addition, we suggest that the lower synchrotron peak blazars (LSPs) could be the source of Changing-look blazars because 90.7\% of the Changing-look blazars in this work are confirmed as LSPs. An anti-correlation between $EW$ and continuum intensity, the so-called global Baldwin effect (BEff) has been confirmed. We suggest the steeper global BEff observed for blazar than for radio-quiet active galactic nuclei (RQ-AGNs) is caused by the inverse Compton scattering of broad-emission-line photons. This interpretation is further supported by the positive correlation between the emission line $EW$ and intrinsic inverse Compton luminosity., Comment: Accepted to ApJ

We present a detailed study of the optical and NIR emission and absorption line spectrum of the quasar SDSS J163345.22+512748.4. We discovered on the newly acquired NIR spectrum a highly meta-stable neutral helium broad absorption line (BAL) \heiozetz\ with a width of $\sim$ 2000 \kmps\ and a blueshift of $\sim$ 7000 \kmps\ in the velocity space. The BAL system is also significantly detected in \mgii\ and \heiteen. We estimate a column density of $(5.0 \pm 1.7) \times 10^{14}$ cm$^{-2}$ for the HeI*(2~$^3$S) level, and infer an ionization parameter of $U_{A} = 10^{-1.9\pm 0.2}$ for the BAL outflow assuming that the BAL region is thick enough for a full development of an ionization front. The total column density of the BAL outflow is constrained in the range N$\rm _{H}$ $\sim$ 10$^{21}$-10$^{21.4}$ cm$^{-2}$. We also found that the bulk of both MgII and UV FeII, as well as H$\alpha$ broad emission lines (BELs) are blueshifted with a velocity of $\sim$ 2200 \kmps\ with respect to the quasar systemic redshift. We constrain that the blueshifted BEL region has a covering factor $C_{f}\approx 16\%$, a density n$\rm _{H}$ $\sim $ 10$^{10.6}$-10$^{11.3}$ cm$^{-3}$, a column density N$\rm _{H}\gtrsim 10^{23}$ cm$^{-2}$, and an ionization parameter $U_{E}\sim 10^{-2.1}-10^{-1.5}$. The outflow gas is located at $\sim$0.1 pc away from the central ionization source, at a scale comparable to the BLR. A toy kinetic model has been proposed to reproduce the profile of MgII BEL well if assuming a partial obscured axisymmetric geometry of the outflow with a radial velocity as observed by the BALs.

To investigate the properties of dust in the nuclear region of quasars, we explored the extinction curves of the iron low-ionization broad absorption line (FeLoBAL) quasar SDSS J163004.29+311957.6 and its two analogues. The parameterized extinction curves indicated the Milky Way-like 2175 \AA~ bump features in underlying extinction, which are similar to those seen in the Local Group and a subset of high-redshift star-forming galaxies. Compared to the bump features in the Large Magellanic Clouds (LMC), the detections in this work are much closer to those in the Milky Way (MW). These bump features, as well as those in the high- and low-ionization broad absorption line (BAL) quasars of Zhang et al., are probably the counterpart of the 2175 \AA~ bump features in the quasar environment. This type of dust grain is generally small, easily disrupted by high-energy photons and has difficulty surviving in the radiation field of the active galactic nucleus (AGN). However, due to the presence of absorption-line outflows, the 2175 \AA~ bump feature in quasars, which should be rare, is seen many times in BAL quasars. The shielding effect of outflow clouds allows the MW-like dust grains to be assembled or extends the survival period in the quasar nuclear region. The process, and physical and chemical conditions deserve further observational study and investigation., Comment: 13 pages, 10 figures. Accepted by Astronomy & Astrophysics

The question of radio dichotomy in the active galactic nuclei (AGNs) is still in debate even it has been proposed for more than forty years. In order to solve the old riddle, we collect a sample of AGNs with optical $B$ band and radio 6cm wavelength data to analyze the radio loudness ${\rm log}R$. Our results indicate a separation of ${\rm log}R = \langle 1.37 \pm 0.02 \rangle$ between radio-loud (RL) AGNs and radio-quiet (RQ) AGNs, suggest the existence of an RL/RQ dichotomy. For the first time, we suggest combining radio luminosity and radio loudness as a double-criterion to divide AGNs into RLs and RQs to avoid misclassification problems that may happen in the single-criterion scenario, we propose the double-criterion dividing line ${\rm log}L_{\rm 6cm} = -2.7{\rm log}R +44.3$ by using a machine learning method. In addition, the key point of the RL/RQ dichotomy is the origin of radio emission for the two classes, we suggest the radio emission from RLs and RQs share the same origin, e.g. jets and mini-jets (aborted-jet or outflow), through a correlation study between radio 6cm luminosity and optical $B$ band luminosity., Comment: 17 pages, 5 figures. Published in PASJ

Jet origination is one of the most important questions of AGN, yet it stays obscure. In this work, we made use of information of emission lines, spectral energy distributions (SEDs), \textit{Fermi}-LAT $\gamma$-ray emission, construct a blazar sample that contains 667 sources. We notice that jet power originations are different for BL Lacs and for FSRQs. The correlation between jet power $P_{\rm jet}$ and the normalized disk luminosity $L_{\rm Disk}/L_{\rm Edd}$ shows a slope of -1.77 for BL Lacs and a slope of 1.16 for FSRQs. The results seem to suggest that BL Lac jets are powered by extracting blackhole rotation energy, while FSRQ jets are mostly powered by accretion disks. Meanwhile, we find the accretion ratio $\dot{M} / \dot{M}_{\rm Edd}$ increase with the normalized $\gamma$-ray luminosity. Base on this, we propose a dividing line, ${\rm log} (L_{\rm BLR}/L_{\rm Edd}) = 0.25 \ {\rm log} (L_{\rm \gamma}/L_{\rm Edd}) - 2.23$, to separate FSRQs and BL Lacs in the diagram of $L_{\rm BLR}/L_{\rm Edd}$ against $L_{\rm \gamma}/L_{\rm Edd}$ through using the machine learning method, the method gives an accuracy of 84.5\%. In addition, we propose an empirical formula, $M_{\rm BH}/M_{\rm \odot} \simeq L_{\rm \gamma}^{0.65}/21.46$, to estimate blackhole mass based on a strong correlation between $\gamma$-ray luminosity and blackhole mass. Strong $\gamma$-ray emission is typical in blazars, and the emission is always boosted by a Doppler beaming effect. In this work, we generate a new method to estimate a lower-limit of Doppler factor $\delta$ and give $\delta_{\rm BL Lac} = 7.94$ and $\delta_{\rm FSRQ} = 11.55$., Comment: Accepted to ApJ