Deep XMM-Newton Observations of an X-ray Weak Broad Absorption Line Quasar at z = 6.5

We report X-ray observations of the most distant known gravitationally lensed quasar, J0439+1634 at z = 6.52, which is also a broad absorption line (BAL) quasar, using the XMM-Newton Observatory. With a 130 ks exposure, the quasar is significantly detected as a point source at the optical position with a total of 358 − 19 + 19 net counts using the EPIC instrument. By fitting a power law plus Galactic absorption model to the observed spectra, we obtain a spectral slope of Γ = 1.45 − 0.09 + 0.10 . The derived optical-to-X-ray spectral slope α ox is − 2.07 − 0.01 + 0.01 , suggesting that the X-ray emission of J0439+1634 is weaker by a factor of 18 than the expectation based on its 2500 Å luminosity and the average α ox versus luminosity relationship. This is the first time that an X-ray weak BAL quasar at z > 6 has been observed spectroscopically. Its X-ray weakness is consistent with the properties of BAL quasars at lower redshift. By fitting a model including an intrinsic absorption component, we obtain intrinsic column densities of N H = 2.8 − 0.6 + 0.7 × 10 23 cm − 2 and N H = 4.3 − 1.5 + 1.8 × 10 23 cm − 2 , assuming a fixed Γ of 1.9 and a free Γ, respectively. The intrinsic rest-frame 2–10 keV luminosity is derived as (9.4–15.1) × 1043 erg s−1, after correcting for lensing magnification (μ = 51.3). The absorbed power-law model fitting indicates that J0439+1634 is the highest redshift obscured quasar with a direct measurement of the absorbing column density. The intrinsic high column density absorption can reduce the X-ray luminosity by a factor of 3–7, which also indicates that this quasar could be a candidate intrinsically X-ray weak quasar.

The contribution of quasar absorption outflows to AGN feedback

ABSTRACT Determining the distance of quasar absorption outflows from the central source (R) and their kinetic luminosity ($\dot{E}_\mathrm{\scriptstyle k}$) is crucial for understanding their contribution to active galactic nucleus (AGN) feedback. Here, we summarize the results for a sample of nine luminous quasars that were observed with the Hubble Space Telescope. We find that the outflows in more than half of the objects are powerful enough to be the main agents for AGN feedback, and that most outflows are found at R > 100 pc. The sample is representative of the quasar absorption outflow population as a whole and is unbiased towards specific ranges of R and $\dot{E}_\mathrm{\scriptstyle k}$. Therefore, the analysis results can be extended to the majority of such objects, including broad absorption line quasars. We find that these results are consistent with those of another sample (seven quasars) that is also unbiased towards specific ranges of R and $\dot{E}_\mathrm{\scriptstyle k}$. Assuming that all quasars have absorption outflows, we conclude that most luminous quasars produce outflows that can contribute significantly to AGN feedback. We also discuss the criterion for whether an outflow is energetic enough to cause AGN feedback effects.

Ferromagnetic properties of ZnO:Mn nanocrystals obtained by the freeze-drying method

In the work, the nanocrystals ZnO and ZnO:Mn with a concentration of Mn 2 and 4 at.% were obtained by the low-temperature freeze-drying method. For this purpose, solutions of zinc acetate Zn(CH3COO)2∙2H2O and manganese one Mn(CH3COO)2∙4H2O were used. By means of XRD, it is established that nanocrystals (NC’s) have a pure phase and wurtzite-type hexagonal lattice, their size is d ~ 65 nm. The EPR spectra of the samples have a broad absorption line. It is due to the presence of a large number of intrinsic and impurity defects in the NC’s. These defects are the result of the destructive action of hydrogen, which is a product of the thermal decomposition of zinc and manganese acetates. It is shown that there is a relationship between the number of crystal lattice defects in the ZnO:Mn NC’s and their ferromagnetic properties at room temperature. Samples of ZnO:Mn with a concentration of Mn 2 and 4 at.%. have a specific magnetization value of Мs equal to 0.089 and 0.045 emu/g, respectively. The results can have great potential in spintronic devices and spin-based electronics.

Detecting neutral hydrogen at z ≳ 3 in large spectroscopic surveys of quasars

ABSTRACT We present a pipeline based on a random forest classifier for the identification of high column density clouds of neutral hydrogen (i.e. the Lyman limit systems, LLSs) in absorption within large spectroscopic surveys of z ≳ 3 quasars. We test the performance of this method on mock quasar spectra that reproduce the expected data quality of the Dark Energy Spectroscopic Instrument and the WHT (William Herschel Telescope) Enhanced Area Velocity Explorer surveys, finding ${\gtrsim}90{{\ \rm per\ cent}}$ completeness and purity for $N_{\rm H\,\rm{\small I}} \gtrsim 10^{17.2}~\rm cm^{-2}$ LLSs against quasars of g < 23 mag at z ≈ 3.5–3.7. After training and applying our method on 10 000 quasar spectra at z ≈ 3.5–4.0 from the Sloan Digital Sky Survey (Data Release 16), we identify ≈6600 LLSs with $N_{\rm H\,\rm{\small I}} \gtrsim 10^{17.5}~\rm cm^{-2}$ between z ≈ 3.1 and 4.0 with a completeness and purity of ${\gtrsim}90{{\ \rm per\ cent}}$ for the classification of LLSs. Using this sample, we measure a number of LLSs per unit redshift of ℓ(z) = 2.32 ± 0.08 at z = [3.3, 3.6]. We also present results on the performance of random forest for the measurement of the LLS redshifts and H i column densities, and for the identification of broad absorption line quasars.

The origin of radio emission in broad absorption line quasars: Results from the LOFAR Two-metre Sky Survey (Corrigendum)

We report an erratum in Morabito et al. (2019, A&A, 622, A15). When calculating radio powers from observed flux densities, the wrong sign convention was used. This resulted in an underestimation of the radio powers by a median value of 0.6 dex and a maximum of 1 dex. The conclusions of the paper are unchanged.

Successive line-locked C iv doublets in quasar SDSS J115122.14+020426.3

ABSTRACT Rodríguez Hidalgo et al. (2013, ApJ, 775, 14) have reported the transition of a C iv mini-broad absorption line (mini-BAL) into a BAL in quasar SDSS J115122.14+020426.3 (hereafter J1151+0204). Based on the two-epoch spectra obtained from the Sloan Digital Sky Survey, we further investigate the three BAL systems (systems A, B and C) in J1151+0204. First, we confirm that the absorption-line variability in J1151+0204 is most likely caused by the change in ionization in response to the continuum variation, according to at least the following observational factors: coordinated strengthening is detected between multiple absorption troughs, and the continuum shows obvious weakening. According to photoionization simulations, asynchronized variability between the continuum and absorption lines indicates that the mini-BAL (system A) of J1151+0204 actually represents the state of a higher ionization level and lower C iv column density of the outflow, while its BAL identifies the state of a lower ionization level and higher C iv column density. Second, we find a rare case of a quintuple, which is due to four successive line-locked C iv doublets, within system C. This indicates that these outflow clouds have achieved a high degree of clumpiness, and that the radiative forces play a significant role in the acceleration process of these clumpy outflow clouds.