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``Little Red Dots'' (LRDs) are an abundant high-redshift population newly discovered by the James Webb Space Telescope (JWST). They are characterized by a red color in the rest-frame optical band, compact morphology, and broad Balmer emission lines (${\rm FWHM} \gtrsim 1000~{\rm km\,s^{-1}}$) that suggest an AGN nature. Using a method of pixel-by-pixel color selection and relaxing the compactness criteria, we identify three of the first dual LRD candidates in the COSMOS-Web survey with projected separations of $0.\!\!^{\prime\prime}2-0.\!\!^{\prime\prime}4$ (1-2 pkpc at their photometric redshifts). A comparison between existing LRD samples and mock data reveals that the projected separations of these dual LRD candidates are unlikely to result from chance projections of objects at different redshifts. In one case (CW-B5-15958), the dual LRD includes two bright sources ($m_{\rm F444W}=24.3$ and $24.8$) with characteristic V-shape spectral energy distribution (SEDs) and photometric redshifts consistent with each other. We find that CW-B5-15958 has a faint off-centered component and a companion galaxy. In the other two dual systems, the brighter LRD exhibits a V-shape SED, while the fainter LRD ($m_{\rm F444W}\gtrsim26$) is undetected in both F115W and F150W. These discoveries suggest that the angular auto-correlation function (ACF) of LRDs exhibits a significant excess ($\sim3\times10^2$ times) on sub-arcsec (kilo-parsec) separations compared to the extrapolation of a power-law ACF of JWST-found AGNs measured over $10^{\prime\prime}-100^{\prime\prime}$. Follow-up spectroscopic confirmation of their redshifts and the construction of a larger sample are essential to advance our understanding of the evolution of supermassive black holes and the importance of mergers in the early universe., Comment: 12 pages, 5 figures, and 1 table. Comments are welcome

We introduce an improved method for decomposing the emission of active galactic nuclei (AGN) and their host galaxies using templates from principal component analysis (PCA). This approach integrates prior information from PCA with a penalized pixel fitting mechanism which improves the precision and effectiveness of the decomposition process. Specifically, we have reduced the degeneracy and over-fitting in AGN-host decomposition, particularly for those with low signal-to-noise ratios (SNR), where traditional methods tend to fail. By applying our method to 76,565 SDSS Data Release 16 quasars with $z<0.8$, we achieve a success rate of $\approx$ 94%, thus establishing the largest host-decomposed spectral catalog of quasars to date. Our fitting results consider the impact of the host galaxy on the overestimation of the AGN luminosity and black hole mass ($M_{\rm BH}$). Furthermore, we obtained stellar velocity dispersion ($\sigma_*$) measurements for 4,137 quasars. The slope of the $M_{\rm BH}-\sigma_*$ relation in this subsample is generally consistent with previous quasar studies beyond the local universe. Our method provides a robust and efficient approach to disentangle the AGN and host galaxy components across a wide range of SNRs and redshifts., Comment: 21 pages, 9 figures, 2 tables. Accepted by ApJ

The structure of the accretion flow onto supermassive black holes (SMBH) is not well understood. Standard disc models match to zeroth order in predicting substantial energy dissipation within optically-thick material producing a characteristic strong blue/UV continuum. However they fail at reproducing more detailed comparisons to the observed spectral shapes along with their observed variability. Based on stellar mass black holes within our galaxy, accretion discs should undergo a transition into an X-ray hot, radiatively inefficient flow, below a (mass scaled) luminosity of $\sim 0.02\,L_{\rm{Edd}}$. While this has been seen in limited samples of nearby low-luminosity active galactic nuclei (AGN) and a few rare changing-look AGN, it is not at all clear whether this transition is present in the wider AGN population across cosmic time. A key issue is the difficulty in disentangling a change in spectral state from increased dust obscuration and/or host galaxy contamination, effectively drowning out the AGN emission. Here we use the new eROSITA eFEDS Survey to identify unobscured AGN from their X-ray emission, matched to excellent optical imaging from Subaru's Hyper Suprime-Cam; allowing the subtraction of the host galaxy contamination. The resulting, uncontaminated, AGN spectra reveal a smooth transition from a strongly disc dominated state in bright AGN, to the collapse of the disc into an inefficient X-ray plasma in the low luminosity AGN, with the transition occurring at $\sim 0.02\,L_{\rm{Edd}}$; revealing fundamental aspects of accretion physics in AGN., Comment: 11 pages, 5 figure, 3 appendices - Accepted for publication in MNRAS

In this work, we revisit the relationship between [O III] line width $w_{\rm 90}$ (as the indicator of AGN outflow velocity) and the radio emission in RQQs by employing a large sample of Type I quasars ($\sim 37,000$) selected from the Sloan Digital Sky Survey (SDSS) Data Release Sixteen. By median stacking the radio images (to include the dominant fraction of individually radio non-detected RQQs) of Karl G. Jansky Very Large Array (VLA) Sky Survey (VLASS) for subsamples of RQQs with different $w_{\rm 90}$, our study demonstrates that, the correlation between $w_{\rm 90}$ and radio emission in our SDSS RQQs is significant, and remains solid after controlling the effects of black hole mass, quasar luminosity, Eddington ratio and redshift. This intrinsic link supports that the [O III] outflows in quasars, most likely resulted from wide-angled sub-relativistic quasar winds launched from the accretion disc, could make a dominant contribution to radio emission in the general RQQs. Alternatively, the correlation may be attributed to low-power jets in RQQs if they are ubiquitous and could efficiently enhance the [O III] width through interacting with the ISM. Meanwhile, the star-formation rates traced by the flux ratio of [Ne V]/[O II] emission lines display no dependence on $w_{\rm 90}$ after controlling the effects of black hole mass, quasar luminosity, Eddington ratio and redshift. This suggests that the stronger radio emission in RQQs with larger $w_{\rm 90}$ could not be attributed to outflow enhanced (positive feedback) star formation in the hosts. However, this also indicates the outflows, though exhibiting robust correlation with radio power, produce neither positive nor negative feedback to the star formation in their hosts., Comment: 9 pages, 4 figures, accepted by MNRAS

We previously built a sample of 14,012 extremely variable quasars (EVQs) based on SDSS and Pan-STARRS1 photometric observations. In this work we present the spectral fitting to their SDSS spectra, and study the spectral variation in 1,259 EVQs with multi-epoch SDSS spectra (after prudently excluding spectra with potentially unreliable spectroscopic photometry). We find clear "bluer-when-brighter" trend in EVQs, consistent with previous findings of normal quasars and AGNs. We detect significant intrinsic Baldwin effect (iBeff, i.e., smaller line EW at higher continuum flux in individual AGNs) in the broad MgII and CIV lines of EVQs. Meanwhile, no systematical iBeff is found for the broad Hb line, which could be attributed to strong host contamination at longer wavelengths. Remarkably, by comparing the iBeff slope of EVQs with archived changing-look quasars (CLQs), we show that the CLQs identified in literature are mostly likely a biased (due to its definition) sub-population of EVQs, rather than a distinct population of quasars. We also found no significant broad line breathing of either Hb, MgII or CIV, suggesting the broad line breathing in quasars may disappear at longer timescales ($\sim$ 3000 days)., Comment: 20 pages and 9 figures; Accepted for publication in ApJ

Extremely variable quasars (EVQs) are a population of sources showing large optical photometric variability revealed by time-domain surveys. The physical origin of such extreme variability is yet unclear. In this first paper of a series, we construct the largest-ever sample of 14,012 EVQs using photometric data spanning over $>$ 15 years from SDSS and Pan-STARRS1. We divide them into five sub-samples according to the relative brightness of an EVQ during SDSS spectroscopic observation compared to the mean brightness from photometric observations. Corresponding control samples of normal quasars are built with matched redshift, bolometric luminosity and supermassive black hole mass. We obtain the composite SDSS spectra of EVQs in various states and their corresponding control samples. We find EVQs exhibit clearly bluer (redder) SDSS spectra during bright (dim) states, consistent with the "bluer-when-brighter" trend widely seen in normal quasars. We further find the line EWs of broad MgII, CIV and OIII (but not broad Hb which is yet puzzling) gradually decrease from dim state to bright state, similar to the so-called intrinsic Baldwin effect commonly seen in normal AGNs. Meanwhile, EVQs have systematically larger line EWs compared with the control samples. We also see that EVQs exhibit subtle excess in the very broad line component compared with control samples. Possible explanations for the discoveries are discussed. Our findings support the hypothesis that EVQs are in the tail of a broad distribution of quasar properties, but not a distinct population., Comment: 25 pages and 21 figures; Accepted for publication in ApJ