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    We investigate the possible presence of quasi-periodic oscillation (QPO) signals in 2103 blazars from the Zwicky Transient Facility (ZTF) time-domain survey. We detect a low-frequency QPO signal in five blazars observed over these 3.8-yr-long optical r-band ZTF light curves. These periods range from 144 to 196 d detected at ≳4σ significance levels in both the Lomb–Scargle periodogram and weighted wavelet Z-transform analyses. We find consistent results using the phase dispersion minimization technique. A similar peak is detected in the g-band light curves at a slightly lower significance of 3σ. Such nearly periodic signals on these time-scales in optical wavebands most likely originate from a precessing jet with high Lorentz factor, closely aligned to the observer’s line of sight or the movement of plasma blobs along a helical structure in the jet.

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    The cosmological inflow of a galaxy is speculated to be able to enter the galaxy and enhance the star formation rate (SFR) and black hole accretion rate (BHAR). In this paper, by performing high-resolution hydrodynamic simulations in the framework of macer, we investigate the fate of the inflow and its impacts on the evolution of a massive elliptical galaxy. The inflow properties are adopted from the cosmological simulation IllustrisTNG. We find that the inflow gas hardly enters but is blocked beyond ∼20 kpc from the central galaxy and becomes part of the circumgalactic medium (CGM). The gas pressure gradient, mainly contributed by the thermalized stellar wind and subdominant contributed by the energy input from the active galactic nuclei (AGNs), balances gravity and prevents the inflow from entering the galaxy. The SFR and BHAR are almost not affected by the normal inflow. However, if the rate of cosmological inflow were increased by a factor of 3, a small fraction of the inflow would enter the galaxy and contribute about 10 per cent of the gas in the galaxy. In this case, the gas density in the galaxy would increase by a factor of $\gtrsim$20. This increase is not because of the additional gas supply by the inflow but due to the increase of gas density and pressure in the CGM caused by the inflow. Consequently, the SFR and BHAR would increase by a factor of ∼5 and ∼1000, respectively. Finally, AGN feedback can perturb the motion of the inflow and heat the CGM through its intermittent outbursts.

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  3. Abstract

    We present 0.″22-resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations of CO(2−1) emission from the circumnuclear gas disk in the red nugget relic galaxy PGC 11179. The disk shows regular rotation, with projected velocities near the center of 400 km s−1. We assume the CO emission originates from a dynamically cold, thin disk and fit gas-dynamical models directly to the ALMA data. In addition, we explore systematic uncertainties by testing the impacts of various model assumptions on our results. The supermassive black hole (BH) mass (MBH) is measured to beMBH= (1.91 ± 0.04 [1σstatistical]0.51+0.11[systematic]) × 109M, and theH-band stellar mass-to-light ratioM/LH= 1.620 ± 0.004 [1σstatistical]0.107+0.211[systematic]M/L. ThisMBHis consistent with the BH mass−stellar velocity dispersion relation but over-massive compared to the BH mass−bulge luminosity relation by a factor of 3.7. PGC 11179 is part of a sample of local compact early-type galaxies that are plausible relics ofz∼ 2 red nuggets, and its behavior relative to the scaling relations echoes that of three relic galaxy BHs previously measured with stellar dynamics. These over-massive BHs could suggest that BHs gain most of their mass before their host galaxies do. However, our results could also be explained by greater intrinsic scatter at the high-mass end of the scaling relations, or by systematic differences in gas- and stellar-dynamical methods. AdditionalMBHmeasurements in the sample, including independent cross-checks between molecular gas- and stellar-dynamical methods, will advance our understanding of the co-evolution of BHs and their host galaxies.

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  4. Abstract

    We explore reprocessing models for a sample of 17 hypervariable quasars, taken from the Sloan Digital Sky Survey Reverberation Mapping project, which all show coordinated optical luminosity hypervariability with amplitudes of factors ≳2 between 2014 and 2020. We develop and apply reprocessing models for quasar light curves in simple geometries that are likely to be representative of quasar inner environments. In addition to the commonly investigated thin-disk model, we include the thick-disk and hemisphere geometries. The thick-disk geometry could, for instance, represent a magnetically elevated disk, whereas the hemisphere model can be interpreted as a first-order approximation for any optically thick out-of-plane material caused by outflows/winds, warped/tilted disks, and so on. Of the 17 quasars in our sample, 11 are best-fitted by a hemisphere geometry, five are classified as thick disks, and both models fail for just one object. We highlight the successes and shortcomings of our thermal reprocessing models in case studies of four quasars that are representative of the sample. While reprocessing is unlikely to explain all of the variability that we observe in quasars, we present our classification scheme as a starting point for revealing the likely geometries of reprocessing for quasars in our sample and hypervariable quasars in general.

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  5. Abstract

    We measure the correlation between black hole massMBHand host stellar massM*for a sample of 38 broad-line quasars at 0.2 ≲z≲ 0.8 (median redshiftzmed= 0.5). The black hole masses are derived from a dedicated reverberation mapping program for distant quasars, and the stellar masses are derived from two-band optical+IR Hubble Space Telescope imaging. Most of these quasars are well centered within ≲1 kpc from the host galaxy centroid, with only a few cases in merging/disturbed systems showing larger spatial offsets. Our sample spans two orders of magnitude in stellar mass (∼109–1011M) and black hole mass (∼107–109M) and reveals a significant correlation between the two quantities. We find a best-fit intrinsic (i.e., selection effects corrected)MBHM*,hostrelation oflog(MBH/M)=7.010.33+0.23+1.740.64+0.64log(M*,host/1010M), with an intrinsic scatter of0.470.17+0.24dex. Decomposing our quasar hosts into bulges and disks, there is a similarMBHM*,bulgerelation with slightly larger scatter, likely caused by systematic uncertainties in the bulge–disk decomposition. TheMBHM*,hostrelation atzmed= 0.5 is similar to that in local quiescent galaxies, with negligible evolution over the redshift range probed by our sample. With direct black hole masses from reverberation mapping and the large dynamical range of the sample, selection biases do not appear to affect our conclusions significantly. Our results, along with other samples in the literature, suggest that the locally measured black hole mass–host stellar mass relation is already in place atz∼ 1.

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  6. Abstract

    We measure optical colors for the bulges of 312 disk galaxies from the Carnegie-Irvine Galaxy Survey and convert their previously availableR-band structural parameters to stellar-mass parameters. We also measure their average stellar-mass surface density in the central 1 kpc (Σ1). Comparing the mass-based Kormendy relation with the original one based on flux, we find that the majority of the classifications into classical and pseudo bulges, as well as their overall statistical properties, remain essentially unchanged. While the bulge-type classifications of the Kormendy relation are robust against stellar population effects, the mass-based classification criteria do produce better agreement between bulge structural properties and their stellar populations. Moreover, the mass-based Kormendy relation reveals a population of ultradense bulges akin to high-zcompact early-type galaxies, which are otherwise hidden in the original Kormendy relation. These bulges are probably relics of spheroids assembled in the early universe, although for some we cannot rule out some contribution from secular growth. We confirm previous studies that Σ1correlates well with bulge surface densities.

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  7. Abstract

    Dual active galactic nuclei (AGNs), which are the manifestation of two actively accreting supermassive black holes (SMBHs) hosted by a pair of merging galaxies, are a unique laboratory for studying the physics of SMBH feeding and feedback during an indispensable stage of galaxy evolution. In this work, we present NOEMA CO(2–1) observations of seven kiloparsec-scale dual-AGN candidates drawn from a recent Chandra survey of low redshift, optically classified AGN pairs. These systems are selected because they show unexpectedly low 2–10 keV X-ray luminosities for their small physical separations signifying an intermediate-to-late stage of merger. Circumnuclear molecular gas traced by the CO(2–1) emission is significantly detected in six of the seven pairs and 10 of the 14 nuclei, with an estimated mass ranging between (0.2–21) × 109M. The primary nuclei, i.e., the ones with the higher stellar velocity dispersion, tend to have a higher molecular gas mass than the secondary. Most CO-detected nuclei show a compact morphology, with a velocity field consistent with a kiloparsec-scale rotating structure. The inferred hydrogen column densities range between 5 × 1021–2 × 1023cm−2, but mostly at a few times 1022cm−2, in broad agreement with those derived from X-ray spectral analysis. Together with the relatively weak mid-infrared emission, the moderate column density argues against the prevalence of heavily obscured, intrinsically luminous AGNs in these seven systems, but favors a feedback scenario in which AGN activity triggered by a recent pericentric passage of the galaxy pair can expel circumnuclear gas and suppress further SMBH accretion.

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  8. Abstract We present Atacama Large Millimeter/submillimeter Array (ALMA) imaging of molecular gas across the full star-forming disk of the barred spiral galaxy M83 in CO( J = 1–0). We jointly deconvolve the data from ALMA’s 12 m, 7 m, and Total Power arrays using the MIRIAD package. The data have a mass sensitivity and resolution of 10 4 M ⊙ (3 σ ) and 40 pc—sufficient to detect and resolve a typical molecular cloud in the Milky Way with a mass and diameter of 4 × 10 5 M ⊙ and 40 pc, respectively. The full disk coverage shows that the characteristics of molecular gas change radially from the center to outer disk, with the locally measured brightness temperature, velocity dispersion, and integrated intensity (surface density) decreasing outward. The molecular gas distribution shows coherent large-scale structures in the inner part, including the central concentration, offset ridges along the bar, and prominent molecular spiral arms. However, while the arms are still present in the outer disk, they appear less spatially coherent, and even flocculent. Massive filamentary gas concentrations are abundant even in the interarm regions. Building up these structures in the interarm regions would require a very long time (≳100 Myr). Instead, they must have formed within stellar spiral arms and been released into the interarm regions. For such structures to survive through the dynamical processes, the lifetimes of these structures and their constituent molecules and molecular clouds must be long (≳100 Myr). These interarm structures host little or no star formation traced by H α . The new map also shows extended CO emission, which likely represents an ensemble of unresolved molecular clouds. 
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    Free, publicly-accessible full text available June 1, 2024
  9. ABSTRACT We study the demographics of z ∼ 6 broad-line quasars in the black hole (BH) mass–luminosity plane using a sample of more than 100 quasars at 5.7 < z < 6.5. These quasars have well-quantified selection functions and nearly one-third of them also have virial BH masses estimated from near-IR spectroscopy. We use forward modelling of parametrized intrinsic distributions of BH masses and Eddington ratios, and account for the sample flux limits and measurement uncertainties of the BH masses and luminosities. We find significant differences between the intrinsic and observed distributions of the quantities due to measurement uncertainties and sample flux limits. There is also marginal evidence that the virial BH masses are susceptible to a positive luminosity-dependent bias (BH mass is overestimated when luminosity is above the average), and that the mean Eddington ratio increases with BH mass. Our models provide reliable constraints on the z ∼ 6 BH mass function at $M_{\rm BH}\gt 10^{8.5}\, M_\odot$, with a median 1σ uncertainty of ∼0.5 dex in abundance. The intrinsic Eddington ratio distribution of $M_{\rm BH}\gt 10^{8.5}\, M_\odot$ quasars can be approximated by a mass-dependent Schechter model, with a broad peak around log (Lbol/LEdd) ∼ −0.9. We also find that, at 4.5 ≲ z ≲ 6, the number densities of more massive BHs tend to decline more rapidly with increasing redshift, contrary to the trend at 2.5 ≲ z ≲ 4.5 reported previously. 
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  10. Shocks and torques produced by non-axisymmetric structures such as spiral arms and bars may transport gas to galaxy central regions. We test this hypothesis by studying the dependence of the concentration of CO luminosity ( C CO ) and molecular gas ( C mol ) and the star formation rate ( C SFR ) in the central ∼2 kpc on the strength of non-axisymmetric disk structure using a sample of 57 disk galaxies selected from the EDGE-CALIFA survey. The C mol is calculated using a CO-to-H 2 conversion factor that decreases with higher metallicity and higher stellar surface density. We find that C mol is systematically 0.22 dex lower than C CO . We confirm that high C mol and strong non-axisymmetric disk structure are more common in barred galaxies than in unbarred galaxies. However, we find that spiral arms also increase C mol . We show that there is a good correlation between C mol and the strength of non-axisymmetric structure (which can be due to a bar, spiral arms, or both). This suggests that the stronger the bars and spirals, the more efficient the galaxy is at transporting cold gas to its center. Despite the small subsample size, the C mol of the four Seyferts are not significantly reduced compared to inactive galaxies of similar disk structure, implying that the active galactic nucleus feedback in Seyferts may not notably affect the molecular gas distribution in the central ∼2 kpc. We find that C SFR tightly correlates with C mol in both unbarred and barred galaxies. Likewise, elevated C SFR is found in galaxies with strong disk structure. Our results suggest that the disk structure, either spirals or bars, can transport gas to the central regions, with higher inflow rates corresponding to stronger structure, and consequently boost central star formation. Both spirals and bars play, therefore, an essential role in the secular evolution of disk galaxies. 
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