Liturgica

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The NuSTAR View of the Seyfert 2 Galaxy NGC 4388

We present analysis of NuSTAR X-ray observations in the 3-79 keV energy band of the Seyfert 2 galaxy NGC 4388, taken in 2013. The broadband sensitivity of NuSTAR, covering the Fe K$\alpha$ line and Compton reflection hump, enables tight constraints to be placed on reflection features in AGN X-ray spectra, thereby providing insight into the geometry of the circumnuclear material. In this observation, we found the X-ray spectrum of NGC 4388 to be well described by a moderately absorbed power law with non-relativistic reflection. We fit the spectrum with phenomenological reflection models and a physical torus model, and find the source to be absorbed by Compton-thin material (N$_{H} = (6.5\pm0.8)\times10^{23}$ cm$^{-2}$) with a very weak Compton reflection hump (R $<$ 0.09) and an exceptionally large Fe K$\alpha$ line (EW $= 368^{+56}_{-53}$ eV) for a source with weak or no reflection. Calculations using a thin-shell approximation for the expected Fe K$\alpha$ EW indicate that an Fe K$\alpha$ line originating from Compton-thin material presents a possible explanation.Comment: 5 pages, 2 figures. Accepted for publication in Ap

Suzaku Confirms NGC~3660 is an Unabsorbed Seyfert 2

An enigmatic group of objects, unabsorbed Seyfert 2s may have intrinsically weak broad line regions, obscuration in the line of sight to the BLR but not to the X-ray corona, or so much obscuration that the X-ray continuum is completely suppressed and the observed spectrum is actually scattered into the line of sight from nearby material. NGC 3660 has been shown to have weak broad optical/near infrared lines, no obscuration in the soft X-ray band, and no indication of "changing look" behavior. The only previous hard X-ray detection of this source by Beppo-SAX seemed to indicate that the source might harbor a heavily obscured nucleus. However, our analysis of a long-look Suzaku observation of this source shows that this is not the case, and that this source has a typical power law X-ray continuum with normal reflection and no obscuration. We conclude that NGC 3660 is confirmed to have no unidentified obscuration and that the anomolously high Beppo-SAX measurement must be due to source confusion or similar, being inconsistent with our Suzaku measurements as well as non-detections from Swift-BAT and RXTE.Comment: Accepted to PAS

A Follow-up Study of The West Marshall High School Graduates of 1964 and 1965

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Inferring Compton-thick AGN candidates at z>2 with Chandra using the >8 keV restframe spectral curvature

To fully understand cosmic black hole growth we need to constrain the population of heavily obscured active galactic nuclei (AGN) at the peak of cosmic black hole growth ($z\sim$1-3). Sources with obscuring column densities higher than $\mathrm{10^{24}}$ atoms $\mathrm{cm^{-2}}$, called Compton-thick (CT) AGN, can be identified by excess X-ray emission at $\sim$20-30 keV, called the "Compton hump". We apply the recently developed Spectral Curvature (SC) method to high-redshift AGN (2<z<5) detected with Chandra. This method parametrizes the characteristic "Compton hump" feature cosmologically redshifted into the X-ray band at observed energies <10 keV. We find good agreement in CT AGN found using the SC method and bright sources fit using their full spectrum with X-ray spectroscopy. In the Chandra deep field south, we measure a CT fraction of $\mathrm{17^{+19}_{-11}\%}$ (3/17) for sources with observed luminosity $\mathrm{>5\times 10^{43}}$ erg $\mathrm{s^{-1}}$. In the Cosmological evolution survey (COSMOS), we find an observed CT fraction of $\mathrm{15^{+4}_{-3}\%}$ (40/272) or $\mathrm{32\pm11 \%}$ when corrected for the survey sensitivity. When comparing to low redshift AGN with similar X-ray luminosities, our results imply the CT AGN fraction is consistent with having no redshift evolution. Finally, we provide SC equations that can be used to find high-redshift CT AGN (z>1) for current (XMM-Newton) and future (eROSITA and ATHENA) X-ray missions.Comment: 10 pages, 8 figure

Physically motivated X-ray obscurer models

The nuclear obscurer of Active Galactic Nuclei (AGN) is poorly understood in terms of its origin, geometry and dynamics. We investigate whether physically motivated geometries emerging from hydro-radiative simulations can be differentiated with X-ray reflection spectroscopy. For two new geometries, the radiative fountain model of Wada (2012) and a warped disk, we release spectral models produced with the ray tracing code XARS. We contrast these models with spectra of three nearby AGN taken by NuSTAR and Swift/BAT. Along heavily obscured sight-lines, the models present different 4-20keV continuum spectra. These can be differentiated by current observations. Spectral fits of the Circinus Galaxy favor the warped disk model over the radiative fountain, and clumpy or smooth torus models. The necessary reflector (NH>10^25/cm^2) suggests a hidden population of heavily Compton-thick AGN amongst local galaxies. X-ray reflection spectroscopy is a promising pathway to understand the nuclear obscurer in AGN.Comment: Accepted in A&A. X-ray spectral models can be downloaded from https://github.com/JohannesBuchner/xars/blob/master/doc/warpeddisk.rst (warped disk) and https://github.com/JohannesBuchner/xars/blob/master/doc/wada.rst (radiative fountain model). The XARS code is at https://github.com/JohannesBuchner/xars

NuSTAR Spectroscopy of Multi-Component X-ray Reflection from NGC 1068

We report on observations of NGC1068 with NuSTAR, which provide the best constraints to date on its > 10 keV spectral shape. The NuSTAR data are consistent with past instruments, with no strong continuum or line variability over the past two decades, consistent with its classification as a Compton-thick AGN. The combined NuSTAR, Chandra, XMM-Newton, and Swift BAT spectral dataset offers new insights into the complex secondary emission seen instead of the completely obscured transmitted nuclear continuum. The critical combination of the high signal-to-noise NuSTAR data and the decomposition of the nuclear and extranuclear emission with Chandra allow us to break several model degeneracies and greatly aid physical interpretation. When modeled as a monolithic (i.e., a single N_H) reflector, none of the common Compton-reflection models are able to match the neutral fluorescence lines and broad spectral shape of the Compton reflection without requiring unrealistic physical parameters (e.g., large Fe overabundances, inconsistent viewing angles, poor fits to the spatially resolved spectra). A multi-component reflector with three distinct column densities (e.g., with best-fit values of N_H = 1.5×10^(23), 5×10^(24), and 10^(25) cm^(-2)) provides a more reasonable fit to the spectral lines and Compton hump, with near-solar Fe abundances. In this model, the higher N_H component provides the bulk of the flux to the Compton hump while the lower N_H component produces much of the line emission, effectively decoupling two key features of Compton reflection. We also find that ≈ 30% of the neutral Fe Kɑ line flux arises from >2" (≈140 pc) and is clearly extended, implying that a significant fraction of the <10 keV reflected component arises from regions well outside of a parsec-scale torus. These results likely have ramifications for the interpretation of Compton-thick spectra from observations with poorer signal-to-noise and/or more distant objects

The effect of different homogenization processes on the physical properties of an ice cream mixture and the resulting ice cream when the percentage of fat is varied and the solids not fat remain constant

Publication authorized February 12, 1930."The data presented in this bulletin were taken from a thesis submitted by the junior author in partial fulfillment of the requirements for the degree of Master of Arts in the Graduate School of the University of Missouri, 1928"--P. [5].Digitized 2007 AES.Includes bibliographical references (page 40)

Investigating the evolution of the dual AGN system ESO~509-IG066

We analyze the evolution of the dual AGN in ESO 509-IG066, a galaxy pair located at z=0.034 whose nuclei are separated by 11 kpc. Previous observations with XMM-Newton on this dual AGN found evidence for two moderately obscured ($N_H\sim10^{22}$ cm$^{-2}$) X-ray luminous ($L_X\sim10^{43}$ erg/s) nuclear sources. We present an analysis of subsequent Chandra, NuSTAR and Swift/XRT observations that show one source has dropped in flux by a factor of 10 between 2004 and 2011, which could be explained by either an increase in the absorbing column or an intrinsic fading of the central engine possibly due to a decrease in mass accretion. Both of these scenarios are predicted by galaxy merger simulations. The source which has dropped in flux is not detected by NuSTAR, which argues against absorption, unless it is extreme. However, new Keck/LRIS optical spectroscopy reveals a previously unreported broad H-alpha line which is highly unlikely to be visible under the extreme absorption scenario. We therefore conclude that the black hole in this nucleus has undergone a dramatic drop in accretion rate. From AO-assisted near-infrared integral-field spectroscopy of the other nucleus, we find evidence that the galaxy merger is having a direct effect on the kinematics of the gas close to the nucleus of the galaxy, providing a direct observational link between the galaxy merger and the mass accretion rate on to the black hole.Comment: Accepted for publication in Ap

Broadband Observations of the Compton-thick Nucleus of NGC 3393

We present new NuSTAR and Chandra observations of NGC 3393, a galaxy reported to host the smallest separation dual AGN resolved in the X-rays. While past results suggested a 150 pc separation dual AGN, three times deeper Chandra imaging, combined with adaptive optics and radio imaging suggest a single, heavily obscured, radio-bright AGN. Using VLA and VLBA data, we find an AGN with a two-sided jet rather than a dual AGN and that the hard X-ray, UV, optical, NIR, and radio emission are all from a single point source with a radius <0.2". We find that the previously reported dual AGN is most likely a spurious detection resulting from the low number of X-ray counts (<160) at 6-7 keV and Gaussian smoothing of the data on scales much smaller than the PSF (0.25" vs. 0.80" FWHM). We show that statistical noise in a single Chandra PSF generates spurious dual peaks of the same separation (0.55$\pm$0.07" vs. 0.6") and flux ratio (39$\pm$9% vs. 32% of counts) as the purported dual AGN. With NuSTAR, we measure a Compton-thick source (NH=$2.2\pm0.4\times10^{24}$ cm$^{-2}$) with a large torus half-opening angle, {\theta}=79 which we postulate results from feedback from strong radio jets. This AGN shows a 2-10 keV intrinsic to observed flux ratio of 150. Using simulations, we find that even the deepest Chandra observations would severely underestimate the intrinsic luminosity of NGC 3393 above z>0.2, but would detect an unobscured AGN of this luminosity out to high redshift (z=5).Comment: Accepted for publication in ApJ. 15 Figures and 4 table