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1. Blazar jets launched with similar energy per baryon, independently of their power

   https://doi.org/10.1093/mnras/staa3925  

   Rueda-Becerril, Jesús M ; Harrison, Amanda O ; Giannios, Dimitrios ( January 2021 , Monthly Notices of the Royal Astronomical Society)

   null (Ed.)

   ABSTRACT The most extreme active galactic nuclei are the radio active ones whose relativistic jet propagates close to our line of sight. These objects were first classified according to their emission-line features into flat-spectrum radio quasars (FSRQs) and BL Lacertae objects (BL Lacs). More recently, observations revealed a trend between these objects known as the blazar sequence, along with an anticorrelation between the observed power and the frequency of the synchrotron peak. In this work, we propose a fairly simple idea that could account for the whole blazar population: all jets are launched with similar energy per baryon, independently of their power. In the case of FSRQs, the most powerful jets manage to accelerate to high-bulk Lorentz factors, as observed in the radio. As a result, they have a rather modest magnetization in the emission region, resulting in magnetic reconnection injecting a steep particle–energy distribution and, consequently, steep emission spectra in the γ-rays. For the weaker jets, namely BL Lacs, the opposite holds true; i.e. the jet does not achieve a very high bulk Lorentz factor, leading to more magnetic energy available for non-thermal particle acceleration, and harder emission spectra at frequencies ≳ GeV. In this scenario, we recover all observable properties of blazars with our simulations, including the blazar sequence for models with mild baryon loading (50 ≲ μ ≲ 80). This interpretation of the blazar population therefore tightly constrains the energy per baryon of blazar jets regardless of their accretion rate. 

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2. The Quasar Feedback Survey: revealing the interplay of jets, winds, and emission-line gas in type 2 quasars with radio polarization

   https://doi.org/10.1093/mnras/stac1044  

   Silpa, S. ; Kharb, P. ; Harrison, C. M. ; Girdhar, A. ; Mukherjee, D. ; Mainieri, V. ; Jarvis, M. E. ( April 2022 , Monthly Notices of the Royal Astronomical Society)

   We present results from a combined radio polarization and emission-line study of five type 2 quasars at z < 0.2 with the Karl G. Jansky Very Large Array (VLA) B-array at 5 GHz and Hubble Space Telescope (HST) [O iii] observations. These five sources are known to exhibit close association between radio structures and ionized gas morphology and kinematics. Four sources (J0945+1737, J1000+1242, J1356+1026, and J1430+1339) show polarization in the current data. J1010+1413 is the unpolarized source in our sample. We detect $0.5{-}1{{\ \rm per\ cent}}$ fractional polarization in the radio cores and a high fractional polarization ($10{-}30{{\ \rm per\ cent}}$) in the lobes of these sources. The morphological, spectral, and polarization properties suggest a jet origin for radio emission in J0945+1737, J1000+1242, J1010+1413, and J1430+1339 whereas the current data cannot fully discern the origin of radio emission (jet or wind) in J1356+1026. An anticorrelation between various polarized knots in the radio and [O iii] emission is observed in our sources, similar to that observed in some radio-loud AGN in the literature. This suggests that the radio emission is likely to be depolarized by the emission-line gas. By modelling the depolarization effects, we estimate the size of the emission-line gas clouds to be ∼(2.8 ± 1.7) × 10−5 parsec and the amount of thermal material mixed with the synchrotron plasma to be ∼(1.01 ± 0.08) × 106 M⊙ in the lobe of J0945+1737 (which exhibits the most prominent polarization signature in its lobe). The current work demonstrates that the interplay of jets/winds and emission-line gas is most likely responsible for the nature of radio outflows in radio-quiet AGN.

    

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3. Determining the ratio of the jet to the unbeamed luminosities for γ-ray blazars

   https://doi.org/10.1093/mnras/stad2730  

   Pei, Zhiyuan ; Li, Ziyan ; Huang, Xiulin ; Qian, Yanjun ; Huang, Danyi ; Li, Chengfeng ; Liao, Jiru ; Ye, Xiao ; Liang, Jingchao ; Chen, Guohai ; et al ( September 2023 , Monthly Notices of the Royal Astronomical Society)

   The spectacular observational phenomena lying in blazars can be well explained and described by the relativistic beaming effect that the emission in the jet is highly boosted along the line of sight to observers. Aiming to reveal the intrinsic emission core dominance in γ-ray loud blazars, we collect a large sample including 226 blazars with available superluminal motion data and radio core-dominance parameters at 5 GHz, and calculate a crucial parameter, R⊥, defined as the ratio of the luminosity in the jet to the unbeamed luminosity when the viewing angle comes up to 90°. R⊥ is a better parameter than the well-known core-dominance parameter, R, to reveal more intrinsic physical properties behind the prominent observational characteristics within blazars. We primarily ascertain the updated median value of R⊥ = 0.032 at 5 GHz, illustrating around 97 per cent of the total radio emission are dominated by the jets in γ-ray loud blazars. We also make further discussion on the physical difference in BL Lacertae objects and flat-spectrum radio quasars.

    

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4. MOJAVE – XX. Persistent linear polarization structure in parsec-scale AGN jets

   https://doi.org/10.1093/mnras/stad525  

   Pushkarev, A. B. ; Aller, H. D. ; Aller, M. F. ; Homan, D. C. ; Kovalev, Y. Y. ; Lister, M. L. ; Pashchenko, I. N. ; Savolainen, T. ; Zobnina, D. I. ( February 2023 , Monthly Notices of the Royal Astronomical Society)

   We analysed the parsec-scale linear polarization properties of 436 active galactic nuclei (AGNs) based on 15 GHz polarimetric Very Long Baseline Array observations. We present polarization and total intensity images averaged over at least five epochs since 1996 January 19 through 2019 August 4. Stacking improves the image sensitivity down to ∼30 μJy beam−1 and effectively fills out the jet cross-section both in total intensity and linear polarization. It delineates the long-term persistent magnetic field configuration and its regularity by restoring spatial distributions of the electric vector position angle (EVPA) and fractional polarization, respectively. On average, about 10 yr of stacking period is needed to reveal the stable and most-complete polarization distribution of a source. We find that the degree of polarization significantly increases down and across the jet towards its edges, typically manifesting U or W-shaped transverse profiles, suggesting a presence of a large-scale helical magnetic field associated with the outflow. In some AGN jets, mainly BL Lacs, we detect quasi-constant fractional polarization profiles across the jet, accompanied by EVPAs that closely follow the outflow. BL Lacs show higher fractional polarization values in their cores and jets than those in quasars up to hectoparsec de-projected scales, while on larger scales, they become comparable. High-synchrotron-peaked BL Lac jets are found to be less polarized than intermediate and low-synchrotron-peaked BL Lacs. The spatial distribution of the EVPAs in BL Lacs tend to align with the local jet direction, while quasars show an excess of orthogonal polarization orientation.

    

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5. Quasar feedback survey: molecular gas affected by central outflows and by ∼10-kpc radio lobes reveal dual feedback effects in ‘radio quiet’ quasars

   https://doi.org/10.1093/mnras/stad3453  

   Girdhar, A. ; Harrison, C. M. ; Mainieri, V. ; Fernández Aranda, R. ; Alexander, D. M. ; Arrigoni Battaia, F. ; Bianchin, M. ; Calistro Rivera, G. ; Circosta, C. ; Costa, T. ; et al ( November 2023 , Monthly Notices of the Royal Astronomical Society)

   We present a study of molecular gas, traced via CO (3–2) from Atacama Large Millimeter/submillimeter Array data, of four z < 0.2, ‘radio quiet’, type 2 quasars (Lbol ∼ 1045.3–1046.2 erg s−1; L$_{\mathrm{1.4\, GHz}}\sim 10^{23.7}\!-\!10^{24.3}$ W Hz−1). Targets were selected to have extended radio lobes (≥ 10 kpc), and compact, moderate-power jets (1–10 kpc; Pjet ∼ 1043.2–1043.7 erg s−1). All targets show evidence of central molecular outflows, or injected turbulence, within the gas discs (traced via high-velocity wing components in CO emission-line profiles). The inferred velocities (Vout = 250–440 km s−1) and spatial scales (0.6–1.6 kpc), are consistent with those of other samples of luminous low-redshift active galactic nuclei. In two targets, we observe extended molecular gas structures beyond the central discs, containing 9–53  per cent of the total molecular gas mass. These structures tend to be elongated, extending from the core, and wrap-around (or along) the radio lobes. Their properties are similar to the molecular gas filaments observed around radio lobes of, mostly ‘radio loud’, brightest cluster galaxies. They have the following: projected distances of 5–13 kpc; bulk velocities of 100–340 km s−1; velocity dispersion of 30–130 km s−1; inferred mass outflow rates of 4–20 M⊙ yr−1; and estimated kinetic powers of 1040.3–1041.7 erg s−1. Our observations are consistent with simulations that suggest moderate-power jets can have a direct (but modest) impact on molecular gas on small scales, through direct jet–cloud interactions. Then, on larger scales, jet-cocoons can push gas aside. Both processes could contribute to the long-term regulation of star formation.

    

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