NuSTAR J033202-2746.8: Direct Constraints on the Compton Reflection in a Heavily Obscured Quasar at z ≈ 2

We report Nuclear Spectroscopic Telescope Array (NuSTAR) observations of NuSTAR J033202-2746.8, a heavily obscured, radio-loud quasar detected in the Extended Chandra Deep Field-South, the deepest layer of the NuSTAR extragalactic survey (~400 ks, at its deepest). NuSTAR J033202-2746.8 is reliably detected by NuSTAR only at E > 8 keV and has a very flat spectral slope in the NuSTAR energy band ($\Gamma =0.55^{+0.62}_{-0.64}$; 3-30 keV). Combining the NuSTAR data with extremely deep observations by Chandra and XMM-Newton (4 Ms and 3 Ms, respectively), we constrain the broad-band X-ray spectrum of NuSTAR J033202-2746.8, indicating that this source is a heavily obscured quasar ($N_{\rm H}=5.6^{+0.9}_{-0.8}\times 10^{23}$ cm–2) with luminosity L 10-40 keV ≈ 6.4 × 1044 erg s–1. Although existing optical and near-infrared (near-IR) data, as well as follow-up spectroscopy with the Keck and VLT telescopes, failed to provide a secure redshift identification for NuSTAR J033202-2746.8, we reliably constrain the redshift z = 2.00 ± 0.04 from the X-ray spectral features (primarily from the iron K edge). The NuSTAR spectrum shows a significant reflection component ($R=0.55^{+0.44}_{-0.37}$), which was not constrained by previous analyses of Chandra and XMM-Newton data alone. The measured reflection fraction is higher than the R ~ 0 typically observed in bright radio-loud quasars such as NuSTAR J033202-2746.8, which has L 1.4 GHz ≈ 1027 W Hz–1. Constraining the spectral shape of active galactic nuclei (AGNs), including bright quasars, is very important for understanding the AGN population, and can have a strong impact on the modeling of the X-ray background. Our results show the importance of NuSTAR in investigating the broad-band spectral properties of quasars out to high redshift

NuSTAR unveils a Compton-thick type 2 quasar in MrK 34

We present Nuclear Spectroscopic Telescope Array (NuSTAR) 3-40 keV observations of the optically selected Type 2 quasar (QSO2) SDSS J1034+6001 or Mrk 34. The high-quality hard X-ray spectrum and archival XMM-Newton data can be fitted self-consistently with a reflection-dominated continuum and a strong Fe K? fluorescence line with equivalent width >1 keV. Prior X-ray spectral fitting below 10 keV showed the source to be consistent with being obscured by Compton-thin column densities of gas along the line of sight, despite evidence for much higher columns from multiwavelength data. NuSTAR now enables a direct measurement of this column and shows that N H lies in the Compton-thick (CT) regime. The new data also show a high intrinsic 2-10 keV luminosity of L 2-10 ~ 1044 erg s–1, in contrast to previous low-energy X-ray measurements where L 2-10 lesssim 1043 erg s–1 (i.e., X-ray selection below 10 keV does not pick up this source as an intrinsically luminous obscured quasar). Both the obscuring column and the intrinsic power are about an order of magnitude (or more) larger than inferred from pre-NuSTAR X-ray spectral fitting. Mrk 34 is thus a "gold standard" CT QSO2 and is the nearest non-merging system in this class, in contrast to the other local CT quasar NGC 6240, which is currently undergoing a major merger coupled with strong star formation. For typical X-ray bolometric correction factors, the accretion luminosity of Mrk 34 is high enough to potentially power the total infrared luminosity. X-ray spectral fitting also shows that thermal emission related to star formation is unlikely to drive the observed bright soft component below ~3 keV, favoring photoionization instead

The NuSTAR Extragalactic Survey: A First Sensitive Look at the High-energy Cosmic X-Ray Background Population

We report on the first 10 identifications of sources serendipitously detected by the Nuclear Spectroscopic Telescope Array (NuSTAR) to provide the first sensitive census of the cosmic X-ray background source population at gsim 10 keV. We find that these NuSTAR-detected sources are ≈100 times fainter than those previously detected at gsim 10 keV and have a broad range in redshift and luminosity (z = 0.020-2.923 and L 10-40 keV ≈ 4 × 1041-5 × 1045 erg s–1); the median redshift and luminosity are z ≈ 0.7 and L 10-40 keV ≈ 3 × 1044 erg s–1, respectively. We characterize these sources on the basis of broad-band ≈0.5-32 keV spectroscopy, optical spectroscopy, and broad-band ultraviolet-to-mid-infrared spectral energy distribution analyses. We find that the dominant source population is quasars with L 10-40 keV > 1044 erg s–1, of which ≈50% are obscured with N H gsim 1022 cm–2. However, none of the 10 NuSTAR sources are Compton thick (N H gsim 1024 cm–2) and we place a 90% confidence upper limit on the fraction of Compton-thick quasars (L 10-40 keV > 1044 erg s–1) selected at gsim 10 keV of lsim 33% over the redshift range z = 0.5-1.1. We jointly fitted the rest-frame ≈10-40 keV data for all of the non-beamed sources with L 10-40 keV > 1043 erg s–1 to constrain the average strength of reflection; we find R < 1.4 for Γ = 1.8, broadly consistent with that found for local active galactic nuclei (AGNs) observed at gsim 10 keV. We also constrain the host-galaxy masses and find a median stellar mass of ≈1011 M ☉, a factor ≈5 times higher than the median stellar mass of nearby high-energy selected AGNs, which may be at least partially driven by the order of magnitude higher X-ray luminosities of the NuSTAR sources. Within the low source-statistic limitations of our study, our results suggest that the overall properties of the NuSTAR sources are broadly similar to those of nearby high-energy selected AGNs but scaled up in luminosity and mass

Determination of nicarbazin as dinitrocarbanilide residues in chicken feed, breast and litter.

Abstract: To control coccidiosis, a common disease in commercial broiler production, anticoccidials are added to feed. However, concerns about the deposition of anticoccidial residues in chicken breast do exist. Brazilian law allows 200 &#956;g kg-1 of nicarbazin (main chicken anticoccidial) residue in chicken breast, but demands its withdrawal from feed 10 days before slaughter, to avoid its presence in chicken breast. The present research aimed at raising chickens for 42 days and subject them to three treatments with anticoccidials by analyzing nicarbazin residues as dinitrocarbanilide (DNC) in feed, breast and poultry litter. The results showed that feed and breast had DNC levels within the legislation, therefore chicken breast is safe for human consumption. Also, shortly after nicarbazin removal from feed, DNC concentration dropped in poultry litter by about 50% in all treatments. Resumo ? Para controlar a coccidiose, doença comum na produção comercial de frangos de corte, são adicionados anticoccidianos à ração. No entanto, preocupações sobre a deposição de resíduos de anticoccidianos no peito de frango existem. A legislação brasileira permite 200 &#956;g kg-1 de resíduo de nicarbazina (principal anticoccidiano) no peito de frango, porém exige que seja retirado da ração 10 dias antes do abate, para evitar sua presença no peito de frango. A presente pesquisa objetivou criar frangos por 42 dias e submete-los a três tratamentos com anticoccidianos, analisando resíduos de nicarbazina na forma de dinitrocarbanilida (DNC) na ração, peito e cama de aviário. Os resultados mostraram que na ração e no peito, todos níveis de DNC se mantiveram dentro da legislação, sendo o peito de frango seguro para consumo humano. Ainda, logo após a retirada da nicarbazina da ração, a concentração de DNC na cama de aviário caiu cerca de 50% em todos tratamentos.bitstream/item/219013/1/final9387.pd

NuSTAR Observations of Heavily Obscured Quasars at z ~ 0.5

We present NuSTAR hard X-ray observations of three Type 2 quasars at z ≈ 0.4-0.5, optically selected from the Sloan Digital Sky Survey. Although the quasars show evidence for being heavily obscured, Compton-thick systems on the basis of the 2-10 keV to [O III] luminosity ratio and multiwavelength diagnostics, their X-ray absorbing column densities (N H) are poorly known. In this analysis, (1) we study X-ray emission at >10 keV, where X-rays from the central black hole are relatively unabsorbed, in order to better constrain N H. (2) We further characterize the physical properties of the sources through broad-band near-UV to mid-IR spectral energy distribution analyses. One of the quasars is detected with NuSTAR at >8 keV with a no-source probability of <0.1%, and its X-ray band ratio suggests near Compton-thick absorption with N H gsim 5 × 1023 cm–2. The other two quasars are undetected, and have low X-ray to mid-IR luminosity ratios in both the low-energy (2-10 keV) and high-energy (10-40 keV) X-ray regimes that are consistent with extreme, Compton-thick absorption (N H gsim 1024 cm–2). We find that for quasars at z ~ 0.5, NuSTAR provides a significant improvement compared to lower energy (<10 keV) Chandra and XMM-Newton observations alone, as higher column densities can now be directly constrained

The NuSTAR View of Nearby Compton-thick Active Galactic Nuclei: The Cases of NGC 424, NGC 1320, and IC 2560

We present X-ray spectral analyses for three Seyfert 2 active galactic nuclei (AGNs), NGC 424, NGC 1320, and IC 2560, observed by NuSTAR in the 3-79 keV band. The high quality hard X-ray spectra allow detailed modeling of the Compton reflection component for the first time in these sources. Using quasi-simultaneous NuSTAR and Swift/XRT data, as well as archival XMM-Newton data, we find that all three nuclei are obscured by Compton-thick material with column densities in excess of ~5 × 1024 cm–2, and that their X-ray spectra above 3 keV are dominated by reflection of the intrinsic continuum on Compton-thick material. Due to the very high obscuration, absorbed intrinsic continuum components are not formally required by the data in any of the sources. We constrain the intrinsic photon indices and the column density of the reflecting medium through the shape of the reflection spectra. Using archival multi-wavelength data we recover the intrinsic X-ray luminosities consistent with the broadband spectral energy distributions. Our results are consistent with the reflecting medium being an edge-on clumpy torus with a relatively large global covering factor and overall reflection efficiency of the order of 1%. Given the unambiguous confirmation of the Compton-thick nature of the sources, we investigate whether similar sources are likely to be missed by commonly used selection criteria for Compton-thick AGNs, and explore the possibility of finding their high-redshift counterparts