Explore the vast range of titles available.

Observations at submillimetre and X-ray wavelengths show that rapid star formation was common in the host galaxies of active galactic nuclei when the Universe was 2–6 Gyr old, but that the most vigorous star formation is not observed around powerful black holes, thereby confirming a key prediction of models in which an active galactic nucleus expels the interstellar medium of its host galaxy. Star formation blocked by powerful black holes Radiation from active galactic nuclei (AGNs) outshines that produced by star formation at most wavelengths, but in the far-infrared to millimetre waveband AGNs emit comparatively little radiation in comparison with strongly star-forming galaxies. A combination of deep X-ray observations from the Chandra catalogue and submillimetre observations from the SPIRE instrument on the Herschel Space Observatory shows that rapid star formation was common in the host galaxies of AGNs when the Universe was between two billion and six billion years old, but that vigorous star formation is not seen around the more luminous black holes. This suppression of star formation in galaxies that host a powerful AGN is a key prediction of models in which the AGN expels the interstellar medium of its host galaxy when it becomes sufficiently powerful. The old, red stars that constitute the bulges of galaxies, and the massive black holes at their centres, are the relics of a period in cosmic history when galaxies formed stars at remarkable rates and active galactic nuclei (AGN) shone brightly as a result of accretion onto black holes. It is widely suspected, but unproved, that the tight correlation between the mass of the black hole and the mass of the stellar bulge 1 results from the AGN quenching the surrounding star formation as it approaches its peak luminosity 2 , 3 , 4 . X-rays trace emission from AGN unambiguously 5 , whereas powerful star-forming galaxies are usually dust-obscured and are brightest at infrared and submillimetre wavelengths 6 . Here we report submillimetre and X-ray observations that show that rapid star formation was common in the host galaxies of AGN when the Universe was 2–6 billion years old, but that the most vigorous star formation is not observed around black holes above an X-ray luminosity of 10 44 ergs per second. This suppression of star formation in the host galaxy of a powerful AGN is a key prediction of models in which the AGN drives an outflow 7 , 8 , 9 , expelling the interstellar medium of its host and transforming the galaxy’s properties in a brief period of cosmic time.

Observations at low redshift have begun to tease out the star formation rate in active galaxies (AGN), which marks the beginning of the black hole-star formation connection over cosmic time. Star formation appears to depend on AGN type, cluster richness, and black hole accretion, but in ways that are not direct and have yet to be understood. Much of the confusion is that while some AGN appear to enhance star formation, others seem to suppress it. By implementing simplified, yet informed assumptions about AGN feedback on star formation, we show how AGN with jets might be dominated by two phases in which star formation is first enhanced, then suppressed. With this new element incorporated into our model, we make sense of radio and quasar mode behavior in the star formation rate–stellar mass (SFR-SM) plane for AGN. Due to jet feedback on star formation, jetted AGN tends to move upwards and rightward in the SFR-SM plane and then downward and to the right, past both the star-forming main sequence as well as the radio-quiet AGN. This picture allows us to predict the black hole connection to star formation as a function of the environment over the history of the universe.

We present the multiwavelength analysis of a heavily obscured active galactic nucleus (AGN) in NGC 449. We first constructed a broadband X-ray spectrum using the latest NuSTAR and XMM-Newton data. Its column density (≃10 24 cm −2 ) and photon index (Γ ≃ 2.4) were reliably obtained by analyzing the broadband X-ray spectrum. However, the scattering fraction and the intrinsic X-ray luminosity could not be well constrained. Combined with the information obtained from the mid-infrared spectrum and spectral energy distribution fitting, we derived its intrinsic X-ray luminosity (≃8.54 × 10 42 erg s −1 ) and scattering fraction ( f scat ≃ 0.26%). In addition, we also derived the following results. (1) The mass accretion rate of the central AGN is about 2.54 × 10 −2 M ⊙ yr −1 , and the Eddington ratio is 8.39 × 10 −2 . (2) The torus of this AGN has a high gas-to-dust ratio ( N H / A V = 8.40 × 10 22 cm −2 mag −1 ). (3) The host galaxy and central AGN are both in the early stage of coevolution.

In this review, the third one in the series focused on a small two-band UV-photometry mission, we assess possibilities for a small UV two-band photometry mission in studying accreting supermassive black holes (SMBHs; mass range ∼ 10 6 – 10 10 M ⊙ ). We focus on the following observational concepts: (i) dedicated monitoring of selected type-I Active Galactic Nuclei (AGN) in order to measure the time delay between the far-UV, the near-UV, and other wavebands (X-ray and optical), (ii) nuclear transients including (partial) tidal disruption events and repetitive nuclear transients, and (iii) the study of peculiar sources, such as changing-look AGN, hollows and gaps in accretion disks, low-luminosity AGN, and candidates for Intermediate-Mass Black Holes (IMBHs; mass range ∼ 10 2 – 10 5 M ⊙ ) in galactic nuclei. The importance of a small UV mission for the observing program (i) is to provide intense, high-cadence monitoring of selected sources, which will be beneficial for, e.g. reverberation-mapping of accretion disks and subsequently confronting accretion-disk models with observations. For program (ii), a relatively small UV space telescope is versatile enough to start monitoring a transient event within ≲ 20 minutes after receiving the trigger; such a moderately fast repointing capability will be highly beneficial. Peculiar sources within the program (iii) will be of interest to a wider community and will create an environment for competitive observing proposals. For tidal disruption events (TDEs), high-cadence UV monitoring is crucial for distinguishing among different scenarios for the origin of the UV emission. The small two-band UV space telescope will also provide information about the near- and far-UV continuum variability for rare transients, such as repetitive partial TDEs and jetted TDEs. We also discuss the possibilities to study and analyze sources with non-standard accretion flows, such as AGN with gappy disks, low-luminosity active galactic nuclei with intermittent accretion, and SMBH binaries potentially involving intermediate-mass black holes.

Research into active galactic nuclei (AGN) – the compact, luminous hearts of many galaxies – is at the forefront of modern astrophysics. Understanding these objects requires extensive knowledge in many different areas: accretion disks, the physics of dust and ionized gas, astronomical spectroscopy, star formation, and the cosmological evolution of galaxies and black holes. This new text by Hagai Netzer, a renowned astronomer and leader in the field, provides a comprehensive introduction to the theory underpinning our study of AGN and the ways that we observe them. It emphasizes the basic physics underlying AGN, the different types of active galaxies and their various components, and the complex interplay between them and other astronomical objects. Recent developments regarding the evolutionary connections between active galaxies and star-forming galaxies are explained in detail. Both graduate students and researchers will benefit from Netzer's authoritative contributions to this exciting field of research.

In this paper, we construct the slowly rotating case of an asymptotically flat supermassive black hole embedded in dark matter using Newman–Janis procedure. Our analysis is carried with respect to the involved parameters including the halo total mass M and the galaxy’s lengthscale a 0 . Concretly, we investigate the dark matter impact on the effective potential and the photon sphere. In particular, we find that the lengthscale a 0 controles such potential values. Indeed, for low a 0 values, we find that the halo total mass M decreases the potential values significantly while for high a 0 values such impact is diluted. Regarding the shadow aspects, we show that the shadow size is much smaller for high values of a 0 while the opposite effect is observed when the halo total mass M is increased. By comparing our case to the slowly rotating case, we notice that the former exhibits a shadow shifted from its center to the left side. Finally, we compute the deflection angle in the weak-limit approximation and inspect the dark matter parameters influence. By ploting such quantity, we observe that one should expect lower bending angle values for black holes in galactic nuclei.

Originally developed to image the shadow region of the central black hole in Sagittarius A* and in the nearby galaxy M87, the Event Horizon Telescope (EHT) provides deep, very high angular resolution data on other active galactic nucleus (AGN) sources too. The challenges of working with EHT data have spurred the development of new image reconstruction algorithms. This work briefly reviews the status of the EHT and its utility for observing AGN sources, with emphasis on novel imaging techniques that offer the promise of better reconstructions at 1.3 mm and other wavelengths.

Based on spectropolarimetry for 47 type 1 active galactic nuclei observed with the 6-m BTA telescope, we have estimated the spins of the supermassive black holes at the centers of these galaxies. We have determined the spins based on the standard Shakura–Sunyaev accretion disk model. About 70% of the investigated active galactic nuclei are shown to have Kerr supermassive black holes with a dimensionless spin greater than 0.9.

In this paper, we use the distributions of two-component radio emissions to investigate the consequences of relativistic beaming on the unified scheme of blazar populations and radio galaxies. Our results show remarkable continuity in the distributions of source luminosities (radio core and extended luminosities, LC and LE respectively as well as γ-ray luminosity Lγ) from radio galaxies at low luminosities to FSRQs at high luminosities through BL subclasses as expected in the blazar unification scheme in a sense suggesting that the sequence of BL Lacs, FSRQs and radio galaxies represents progressively misaligned populations of AGNs. Distribution of radio core-dominance is consistent with average projection angles of 13.5∘, 14.8∘, 16.8∘, 20.4∘ and 28.2∘ for ISPs, LSPs, FSRQs, HSPs, and radio galaxies, respectively. Linear regression analyses of our data yield significant anti-correlation (r>0.60) between core-dominance parameter (C) and LE in each individual subsample: the correlation is significant only when individual subsamples are considered. There is a systematic sequence of the distribution of the different subclasses on the C−LE plane. Nevertheless, little or no correlation between C and LC or between C and Lγ (r<0.50) was observed. There is a clear dichotomy between high synchrotron-peaking BL Lacs and other BL Lac subclasses. The results are consistent with a unified view for blazars and can be understood in terms of relativistic beaming persisting at largest scales.

We present a sample of 4388 AGNs with available radio core-dominance parameters—defined as the ratio of the core flux densities to the extended ones, R = S core / S ext .—which includes 630 Fermi -detected AGNs from the fourth source catalog (4FGL) of the Fermi Large Area Telescope ( Fermi /LAT); the rest are non- Fermi -detected AGNs. In our sample, 584 blazars are Fermi -detected and 1310 are not. The sample also contains other subclasses, such as Seyferts, Fanaroff-Riley I/II galaxies, and normal galaxies. We investigate various properties of the Fermi -detected and non- Fermi -detected AGNs by using core-dominance parameters, capitalizing on a previous study which showed that R is a good indicator of beaming. We then calculate radio spectral indices for the whole sample, and adopt γ -ray-photon indices for the Fermi AGNs from the 4FGL catalog to discuss the properties of different subclasses. We obtain a relation between the core-dominance parameters and the radio spectral indices for both Fermi and non- Fermi sources, assuming a two-component model in the radio band. Our previous study ruled out the assumption that the core-dominance parameters and radio spectral indices are quite different for different AGN subclasses. This holds not only for Fermi sources but also for non- Fermi sources. In particular, R is, on average, greater for the former AGNs than for the latter. In this study, we enlarge our sample with available values of R to 4388 AGNs, and the obtained conclusions are consistent with our previous study. We assume that the same two-component model holds for the γ -ray band as for the radio band, and therefore, adopt the same relation between the core-dominance parameters and the γ -ray-photon indices for Fermi AGNs. Our fitting results indicate that the γ -ray emissions of Fermi blazars originate mainly from the jet, and therefore, we conclude that the Fermi blazars are beamed.