Publication Search Results

ID: 159643
Type: article
Authors: Elvis, Martin; Krolikowski, Alanna; Milligan, Tony
Abstract: Numerous missions planned for the next decade are likely to target a handful of small sites of interest on the Moon's surface, creating risks of crowding and interference at these locations. The Moon presents finite and scarce areas with rare topography or concentrations of resources of special value. Locations of interest to science, notably for astronomy, include the Peaks of Eternal Light, the coldest of the cold traps and smooth areas on the far side. Regions richest in physical resources could also be uniquely suited to settlement and commerce. Such sites of interest are both few and small. Typically, there are fewer than ten key sites of each type, each site spanning a few kilometres across. We survey the implications for different kinds of mission and find that the diverse actors pursuing incompatible ends at these sites could soon crowd and interfere with each other, leaving almost all actors worse off. Without proactive measures to prevent these outcomes, lunar actors are likely to experience significant losses of opportunity. We highlight the legal, policy and ethical ramifications. Insights from research on comparable sites on Earth present a path toward managing lunar crowding and interference grounded in ethical and practical near-term considerations.
This article is part of a discussion meeting issue `Astronomy from the Moon: the next decades'.

ID: 159608
Type: article
Authors: Jones, Mackenzie L.; Parker, Kieran; Fabbiano, G.; Elvis, Martin; Maksym, W. P.; Paggi, A.; Ma, Jingzhe; Karovska, M.; Siemiginowska, Aneta; Wang, Junfeng
Abstract: We present the spatial analysis of five Compton thick (CT) active galactic nuclei (AGNs), including MKN 573, NGC 1386, NGC 3393, NGC 5643, and NGC 7212, for which high-resolution Chandra observations are available. For each source, we find hard X-ray emission (>3 keV) extending to ∼kiloparsec scales along the ionization cone, and for some sources, in the cross-cone region. This collection represents the first, high-signal sample of CT AGN with extended hard X-ray emission for which we can begin to build a more complete picture of this new population of AGN. We investigate the energy dependence of the extended X-ray emission, including possible dependencies on host galaxy and AGN properties, and find a correlation between the excess emission and obscuration, suggesting a connection between the nuclear obscuring material and the galactic molecular clouds. Furthermore, we find that the soft X-ray emission extends farther than the hard X-rays along the ionization cone, which may be explained by a galactocentric radial dependence on the density of molecular clouds due to the orientation of the ionization cone with respect to the galactic disk. These results are consistent with other CT AGN with observed extended hard X-ray emission (e.g., ESO 428-G014 and the Ma et al. CT AGN sample), further demonstrating the ubiquity of extended hard X-ray emission in CT AGN.

ID: 159561
Type: article
Authors: Luminari, A.; Nicastro, Fabrizio; Elvis, Martin; Piconcelli, E.; Tombesi, F.; Zappacosta, Luca; Fiore, F.
Abstract: Context. Ultra-fast outflows (UFOs) have become an established feature in analyses of the X-ray spectra of active galactic nuclei (AGN). According to the standard picture, they are launched at accretion disc scales with relativistic velocities, up to 0.3-0.4 times the speed of light. Their high kinetic power is enough to induce an efficient feedback on a galactic scale, possibly contributing to the co-evolution between the central supermassive black hole (SMBH) and the host galaxy. It is, therefore, of paramount importance to gain a full understanding of UFO physics and, in particular, of the forces driving their acceleration and the relation to the accretion flow from which they originate.
Aims: In this paper, we investigate the impact of special relativity effects on the radiative pressure exerted onto the outflow. The radiation received by the wind decreases for increasing outflow velocity, v, implying that the standard Eddington limit argument has to be corrected according to v. Due to the limited ability of the radiation to counteract the black hole gravitational attraction, we expect to find lower typical velocities with respect to the non-relativistic scenario.
Methods: We integrated the relativistic-corrected outflow equation of motion for a realistic set of starting conditions. We concentrated on a range of ionisations, column densities, and launching radii consistent with those typically estimated for UFOs. We explore a one-dimensional, spherical geometry and a three-dimensional setting with a rotating, thin accretion disc.
Results: We find that the inclusion of special relativity effects leads to sizeable differences in the wind dynamics and that v is reduced up to 50% with respect to the non-relativistic treatment. We compare our results with a sample of UFOs from the literature and we find that the relativistic-corrected velocities are systematically lower than the reported ones, indicating the need for an additional mechanism, such as magnetic driving, to explain the highest velocity components. Finally, we note that these conclusions, derived for AGN winds, are generally applicable.

ID: 159625
Type: article
Authors: Ma, Jingzhe; Maksym, W. Peter; Fabbiano, G.; Elvis, Martin; Storchi-Bergmann, Thaisa; Karovska, Margarita; Wang, Junfeng; Travascio, Andrea
Abstract: We present spatially resolved Baldwin-Phillips-Terlevich (BPT) mapping of the extended narrow-line regions (ENLRs) of seven nearby Seyfert 2 galaxies, using Hubble Space Telescope narrowband filter imaging. We construct the BPT diagrams using ≤0"1 resolution emission line images of [O III] λ5007, Hα, [S II] λλ6717, 6731, and Hβ. By mapping these diagnostic lines according to the BPT classification, we dissect the ENLR into Seyfert, low-ionization nuclear emission-line (LINER), and star-forming regions. The nucleus and ionization cones are dominated by Seyfert-type emission, which can be interpreted as predominantly photoionization by the active galactic nucleus (AGN). The Seyfert nucleus and ionization cones transition to and are surrounded by a LINER cocoon, extending up to ∼250 pc in thickness. The ubiquity of the LINER cocoon in Seyfert 2 galaxies suggests that the circumnuclear regions are not necessarily Seyfert-type, and LINER activity plays an important role in Seyfert 2 galaxies. We demonstrate that spatially resolved diagnostics are crucial to understanding the excitation mechanisms in different regions and the AGN-host galaxy interactions.

ID: 157823
Type: article
Authors: Bhat, Harshitha K.; Chakravorty, Susmita; Sengupta, Dhrubojyoti; Elvis, Martin; Datta, Sudeb Ranjan; Roy, Nirupam; Bertemes, Caroline; Ferland, Gary; Ezhikode, Savithri H.
Abstract: The extreme ultraviolet region (EUV) provides most of the ionization that creates the high equivalent width (EW) broad and narrow emission lines (BELs and NELs) of quasars. Spectra of hypermassive Schwarzschild black holes (HMBHs; M_BH ≥ 10¹⁰ M_☉) with α-discs, decline rapidly in the EUV suggesting much lower EWs. Model spectra for BHs of mass 10⁶-10¹² M_☉ and accretion rates 0.03 ≤ L_bol/L_Edd ≤ 1.0 were input to the CLOUDY photoionization code. BELs become ∼100 times weaker in EW from M_BH ∼ 10⁸ M_☉ to M_BH ∼ 10¹⁰ M_☉. The high-ionization BELs (O VI 1034 Å, C IV 1549 Å, and He II 1640 Å) decline in EW from M_BH ≥ 10⁶ M_☉, reproducing the Baldwin effect, but regain EW for M_BH ≥ 10¹⁰ M_☉. The low-ionization lines (Mg II 2798 Å, H β 4861 Å, and H α 6563 Å) remain weak. Lines for maximally spinning HMBHs behave similarly. Line ratio diagrams for the BELs show that high O VI/H β and low C IV/H α may pick out HMBH, although O VI is often hard to observe. In NEL BPT diagrams, HMBHs lie among star-forming regions, except for highly spinning, high accretion rate HMBHs. In summary, the BELs expected from HMBHs would be hard to detect using the current optical facilities. From 100 to 10¹² M_☉, the emission lines used to detect active galactic nuclei (AGNs) only have high EW in the 10⁶-10⁹ M_☉ window, where most AGNs are found. This selection effect may be distorting reported distributions of M_BH.

ID: 158817
Type: article
Authors: Fabbiano, Giuseppina; Paggi, A.; Karovska, Margarita; Elvis, Martin; Nardini, E.; Wang, Junfeng
Abstract: We present a reanalysis of the cumulative ACIS-S Chandra data set pointed at the double active galactic nuclei (AGNs) of the NGC 6240 merging galaxy, focusing on the hard energy bands containing the hard spectral continuum (5.5-5.9 keV), the redshifted Fe I Ka line (6.0-6.4 keV), and the redshifted Fe XXV line (6.4-6.7 keV). We have used the full Chandra telescope angular resolution and modeled the Chandra point-spread function (PSF) by comparing a preflight calibration model to the data for the two bright AGNs. With two complementary approaches-(1) studying the residuals after PSF subtraction and (2) producing reconstructed Expectation through Markov Chain Monte Carlo (EMC2) images-we are able to resolve structures extending from ˜1 kpc to <200 pc in the S AGN. The latter are within the sphere of influence of this BH. We find significant extended emission in both continuum and Fe lines in the ˜2" (˜1 kpc) region surrounding the nuclei, in the region between the N and S AGN, and in a sector of PA 120-210 deg. extending to the SE from the centroid of the S AGN surface brightness. The extended Fe I Ka emission is likely to originate from the fluorescence of X-ray photons interacting with dense molecular clouds, providing a complementary view to recent high-resolution Atacama Large Millimeter/submillimeter Array (ALMA) studies. The nonthermal emission is more prevalent in the region in between the two active X-ray nuclei and in the N AGN. We do not find strong evidence of X-ray emission associated with the third nucleus recently proposed for NGC 6240.

ID: 155843
Type: article
Authors: Feruglio, C.; Fabbiano, Giuseppina; Bischetti, M.; Elvis, Martin; Travascio, A.; Fiore, F.
Abstract: We present ALMA 230 GHz continuum and CO(2─1) observations of the nearby Compton-thick Seyfert galaxy ESO428─G14, with angular resolution 0"7 (78 pc). CO(2─1) is distributed in clumpy spiral arms, a lopsided circumnuclear ring (CNR) with ∼200 pc radius, and a transverse gas lane with size _dyn = 5 × 10⁹ M_☉ within ∼1 kpc. We detect off-plane gas motions with respect to the main disk plane which likely trace a molecular outflow with rate ${\dot{M}}_{\mathrm{of}}\approx 0.1\mbox{--}0.3\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$ , along a biconical structure with radius 700 pc. The CO outflow smoothly joins the warm molecular outflow detected in SINFONI/Very Large Telescope data in the central 170 pc, suggesting that the outflow may cool with increasing distance. Our dynamical modeling of the inner 100 pc region suggests a warped disk or bar, and of fast gas streams which may trace an inflow toward the AGN. The inner warped disk overlaps with the most obscured, CT region seen in X-rays. There, we derive a column density $N({{\rm{H}}}_{2})\approx 2\times {10}^{23}\,{\mathrm{cm}}^{-2}$ , suggesting that molecular gas may contribute significantly to the AGN obscuration. Most of the hard X-ray emitting nuclear region is deprived of cold molecular gas and shows a CO-cavity. The CO-cavity is filled with warm molecular gas traced by H₂, confirming that the 3─6 keV continuum and Fe Kα emission are due to scattering from dense ISM clouds.

ID: 156368
Type: article
Authors: Jones, Mackenzie L.; Fabbiano, Giuseppina; Elvis, Martin; Paggi, A.; Karovska, Margarita; Maksym, W. Peter; Siemiginowska, Aneta; Raymond, John
Abstract: Recent observations of nearby Compton thick (CT) active galactic nuclei (AGNs) with Chandra have resolved hard (>3 keV) X-ray emission extending out from the central supermassive black hole to kiloparsec scales, challenging the long-held belief that the characteristic hard X-ray continuum and fluorescent Fe K lines originate in the inner ∼parsec due to the excitation of obscuring material. In this paper we present the results of the most recent Chandra ACIS-S observations of NGC 7212, a CT AGN in a compact group of interacting galaxies, with a total effective exposure of ∼150 ks. We find ∼20% of the observed emission is found outside of the central kiloparsec, with ∼17% associated with the soft X-rays, and ∼3% with hard X-ray continuum and Fe K line. This emission is extended both along the ionization cone and in the cross-cone direction up to ∼3.8 kpc scales. The spectrum of NGC 7212 is best represented by a mixture of thermal and photoionization models that indicate the presence of complex gas interactions. These observations are consistent with what is observed in other CT AGN (e.g., ESO 428-G014, NGC 1068), providing further evidence that this may be a common phenomenon. High-resolution observations of extended CT AGN provide an especially valuable environment for understanding how AGN feedback impacts host galaxies on galactic scales.

ID: 158791
Type: article
Authors: Lusso, E.; Risaliti, G.; Nardini, E.; Bargiacchi, G.; Benetti, M.; Bisogni, S.; Capozziello, S.; Civano, Francesca; Eggleston, L.; Elvis, Martin; Fabbiano, Giuseppina; Gilli, R.; Marconi, A.; Paolillo, M.; Piedipalumbo, E.; Salvestrini, F.; Signorini, M.; Vignali, C.
Abstract: We present a new catalogue of ˜2400 optically selected quasars with spectroscopic redshifts and X-ray observations from either Chandra or XMM-Newton. The sample can be used to investigate the non-linear relation between the ultraviolet (UV) and X-ray luminosity of quasars as well as to build a Hubble diagram up to a redshift of z ˜ 7.5. We selected sources that are neither reddened by dust in the optical and UV nor obscured by gas in the X-rays, and whose X-ray fluxes are free from flux-limit-related biases. After checking for any possible systematics, we confirm, in agreement with our previous works, that the X-ray to UV relation provides distance estimates matching those from supernovae up to z ˜ 1.5, and its slope shows no redshift evolution up to z ˜ 5. We provide a full description of the methodology for testing cosmological models, further supporting a trend whereby the Hubble diagram of quasars is well reproduced by the standard flat cold dark matter model up to z ˜ 1.5-2, but strong deviations emerge at higher redshifts. Since we have minimised all non-negligible systematic effects and proven the stability of the L_X - L_UV relation at high redshifts, we conclude that an evolution of the expansion rate of the Universe should be considered as a possible explanation for the observed deviation, rather than some systematic (redshift-dependent) effect associated with high-redshift quasars.
Full Table 3 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/642/A150

ID: 157684
Type: article
Authors: Ma, Jingzhe; Elvis, Martin; Fabbiano, Giuseppina; Baloković, Mislav; Maksym, W. Peter; Jones, Mackenzie L.; Risaliti, Guido
Abstract: The recent Chandra discovery of extended ∼kiloparsec-scale hard (>3 keV) X-ray emission in nearby Compton-thick (CT) active galactic nuclei (AGN) opens a new window to improving AGN torus modeling and investigating how the central supermassive black hole interacts with and impacts the host galaxy. Since there are only a handful of detections so far, we need to establish a statistical sample to determine the ubiquity of the extended hard X-ray emission in CT AGN and quantify the amount and extent of this component. In this paper, we present the spatial analysis results of a pilot Chandra imaging survey of seven nearby ( $0.006\lt z\lt 0.013$ ) CT AGN selected from the Swift-BAT spectroscopic AGN survey. We find that five out of the seven CT AGN show extended emission in the 3-7 keV band detected at >3σ above the Chandra point-spread function (PSF), with ∼12%-22% of the total emission in the extended components. ESO 137-G034 and NGC 3281 display biconical ionization structures with extended hard X-ray emission reaching kiloparsec scales (∼1.9 and 3.5 kpc in diameter). The other three show extended hard X-ray emission above the PSF out to at least ∼360 pc in radius. We find a trend that a minimum 3-7 keV count rate of 0.01 counts s^-1 and total excess fraction >20% are required to detect a prominent extended hard X-ray component. Given that this extended hard X-ray component appears to be relatively common in this uniformly selected CT AGN sample, we further discuss the implications for torus modeling and AGN feedback.

ID: 158809
Type: article
Authors: Maksym, W. Peter; Schmidt, Judy; Keel, William C.; Fabbiano, Giuseppina; Fischer, Travis C.; Bland-Hawthorn, Joss; Barth, Aaron J.; Elvis, Martin; Oosterloo, Tom; Ho, Luis C.; Kim, Minjin; Hwang, Hyunmo; Mayer, Evan
Abstract: On Earth near sunset, the Sun may cast "crepuscular rays" such that clouds near the horizon obscure the origin of light scattered in bright rays. In principle, active galactic nuclei (AGN) should be able to produce similar effects. Using new Hubble Space Telescope (HST) near-infrared and optical observations, we show that the active galaxy IC 5063 contains broad radial rays extending to ?11 kpc from the nucleus. We argue that the bright rays may arise from dusty scattering of continuum emission from the active nucleus, while the dark rays are due to shadowing near the nucleus, possibly by a warped torus. We also consider alternative AGN-related and stellar origins for the extended light. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. These observations are associated with programs #15444 and #15609.

ID: 158859
Type: article
Authors: Murchikova, Lena; Murphy, Eric J.; Lis, Dariusz C.; Armus, Lee; de Mink, Selma; Sheth, Kartik; Zakamska, Nadia; Tramper, Frank; Bongiorno, Angela; Elvis, Martin; Kewley, Lisa; Sana, Hugues
Abstract: The extreme ultraviolet (EUV) spectra of distant star-forming regions cannot be probed directly using either ground- or space-based telescopes due to the high cross section for interaction of EUV photons with the interstellar medium. This makes EUV spectra poorly constrained. The millimeter/submillimeter recombination lines of H and He, which can be observed from the ground, can serve as a reliable probe of the EUV. Here we present a study based on ALMA observations of three Galactic ultracompact H II regions and the starburst region Sgr B2(M), in which we reconstruct the key parameters of the EUV spectra using millimeter recombination lines of H I, He I, and He II. We find that in all cases the EUV spectra between 13.6 and 54.4 eV have similar frequency dependence: ${L}_{\nu }\propto {\nu }^{-4.5\pm 0.4}.$ We compare the inferred values of the EUV spectral slopes with the values expected for a purely single stellar evolution model (Starburst99) and the Binary Population and Spectral Synthesis code (BPASS). We find that the observed spectral slope differs from the model predictions. This may imply that the fraction of interacting binaries in H II regions is substantially lower than assumed in BPASS. The technique demonstrated here allows one to deduce the EUV spectra of star-forming regions, providing critical insight into photon production rates at $\lambda \leqslant 912\mathring{{\rm{A}}}$ , and can serve as calibration to starburst synthesis models, improving our understanding of star formation in the distant universe and the properties of ionizing flux during reionization.

ID: 156989
Type: article
Authors: Quera-Bofarull, Arnau; Done, Chris; Lacey, Cedric; McDowell, Jonathan C.; Risaliti, Guido; Elvis, Martin
Abstract: Ultraviolet (UV) line-driven winds may be an important part of the active galactic nucleus (AGN) feedback process, but understanding their impact is hindered by the complex nature of the radiation hydrodynamics. Instead, we have taken the approach pioneered by Risaliti & Elvis, calculating only ballistic trajectories from radiation forces and gravity but neglecting gas pressure. We have completely rewritten their Qwind code using more robust algorithms and can now quickly model the acceleration phase of these winds for any AGN spectral energy distribution spanning UV and X-ray wavebands. We demonstrate the code using an AGN with black hole mass $10^8\, \text{M}_\odot$ emitting at half the Eddington rate and show that this can effectively eject a wind with velocities ${\simeq}(0.1-0.2)\, c$ . The mass loss rates can be up to ≃0.3M_☉ per year, consistent with more computationally expensive hydrodynamical simulations, though we highlight the importance of future improvements in radiation transfer along the multiple different lines of sight illuminating the wind. The code is fully public and can be used to quickly explore the conditions under which AGN feedback can be dominated by accretion disc winds.

ID: 158869
Type: article
Authors: Serjeant, Stephen; Elvis, Martin; Tinetti, Giovanna
Abstract: The number of small satellites has grown hugely in the past decade, from tens of satellites per year in the mid-2010s to a projection of tens of thousands in orbit by the mid-2020s. This presents both problems and opportunities for observational astronomy. Small satellites offer complementary cost-effective capabilities to both ground-based astronomy and larger space missions. Compared with ground-based astronomy, these advantages are not just in the accessibility of wavelength ranges where the Earth's atmosphere is opaque, but also in stable, high-precision photometry, long-term monitoring and improved areal coverage. Astronomy has a long history of new observational parameter spaces leading to major discoveries. Here we discuss the potential for small satellites to explore new parameter spaces in astrophysics, drawing on examples from current and proposed missions, and spanning a wide range of science goals from binary stars, exoplanets and Solar System science to the early Universe and fundamental physics.

ID: 154438
Type: article
Authors: Elvis, Martin; Milligan, Tony
Abstract: "How much of the Solar System should we reserve as wilderness, off- limits to human development?" We make a general argument that, as a matter of fixed policy, development should be limited to one eighth, with the remainder set aside. We argue that adopting a "one-eighth principle" is far less restrictive, overall, than it might seem. One eighth of the iron in the asteroid belt is more than a million times greater than all of the Earth's currently estimated iron ore reserves, and it may well suffice for centuries. A limit of some sort is necessary because of the problems associated with exponential growth. We note that humans are poor at estimating the pace of such growth and, as a result, the limitations of a resource are hard to recognize before the final three doubling times. These three doublings take utilization successively from an eighth to a quarter, then to a half, and then to the point of exhaustion. Population growth and climate change are instances of unchecked exponential growth. Each places strains upon our available resources, each is a recognized problem that we would like to control, but attempts to do so at this comparatively late stage in their development have not been encouraging. Our limited ability to see ahead until such processes are far advanced, suggests that we should set ourselves a "tripwire" that gives us at least 3 doubling times as leeway. This tripwire would be triggered when one eighth of the Solar System's resources are close to being exploited. The timescale on which we might hit this tripwire, for several assumed growth rates, is long. At a 3.5% growth rate for the space economy, comparable to that of the use of iron from the beginning of the Industrial Revolution until now, the 1/8th point would be reached after 400 years. At that point, the 20-year doubling time associated with a 3.5% growth rate would mean that only 60 years would remain in which to transition the economic system to new "steady state" conditions. The rationale for adopting the one-eighth principle so far in advance is that it may be far easier to implement in-principle restrictions at an early stage, rather than later, when vested and competing interests have come into existence under conditions of diminishing opportunity.

ID: 154627
Type: article
Authors: Fabbiano, Giuseppina; Elvis, Martin
Abstract: We report the detection in Chandra Advanced CCD Imaging Spectrometer archival data of an elongated soft (⁴⁰ erg s^-1. We infer an [O III]/soft-X-ray ratio in the range of ̃200, consistent with the highest values measured in some of the clouds of NGC 4151. Overall, given the uncertainties, Hanny's Voorwerp appears to be a feature consistent with the ionization cone emission of nearby AGNs. We estimate an X-ray recombination time of ̃2 × 10⁷ yr, longer than the [O III] recombination time (̃8000 yr). This suggests that extended soft X-ray components may be a better diagnostic of overall long-term activity, while detection of an [O III] HV would point to a time-limited activity burst.

ID: 155158
Type: article
Authors: Fabbiano, Giuseppina; Paggi, A.; Elvis, Martin
Abstract: A recent Atacama Large Millimeter/submillimeter Array study of the Seyfert 2 active galactic nucleus (AGN) NGC 2110 by Rosario et al. has reported a remarkable lack of CO 2-1 emission from the circumnuclear region, where optical lines and H₂ emission are observed, leading to the suggestion of excitation of the molecular clouds by the AGN. As interaction with X-ray photons could be the cause of this excitation, we have searched the archival Chandra data for corroborating evidence. We report the discovery of an extra-nuclear ∼1″ (∼170 pc) feature in the soft ( emission are observed, leading to the suggestion of excitation of the molecular clouds by the AGN. As interaction with X-ray photons could be the cause of this excitation, we have searched the archival Chandra data for corroborating evidence. We report the discovery of an extra-nuclear ∼1″ (∼170 pc) feature in the soft (₂ emission in this region, which is devoid of CO 2-1 emission. The Chandra image completes the emerging picture of a multiphase circumnuclear medium excited by the X-rays from the AGN, with dense warm molecular clouds emitting in H₂ but depleted of CO 2-1 line emission.

ID: 150426
Type: article
Authors: Fabbiano, Giuseppina; Siemiginowska, Aneta; Paggi, Alessandro; Elvis, Martin; Volonteri, M.; Mayer, L.; Karovska, Margarita; Maksym, W. Peter; Risaliti, G.; Wang, Junfeng
Abstract: We report the results of high-resolution subpixel imaging of the hard continuum and Fe Kα line of the Compton-thick (CT) active galactic nucleus (AGN) ESO 428-G014, observed with Chandra ACIS. While the 3–4 keV emission is dominated by an extended component, a single nuclear point source is prominent in the 4–6 keV range. Instead, two peaks of similar intensity, separated by ∼36 pc in projection on the plane of the sky are detected in the Fe Kα emission. The SE knot could be marginally associated with the heavily obscured hard continuum source. We discuss four possible interpretations of the nuclear morphology. (1) Given the bolometric luminosity and likely black hole mass of ESO 428-G014, we may be imaging two clumps of the CT obscuring torus in the Fe Kα line. (2) The Fe Kα knots may be connected with the fluorescent emission from the dusty bicone, or (3) with the light echo of a nuclear outburst. (4) We also explore the less likely possibility that we may be detecting the rare signature of merging nuclei. Considering the large-scale kiloparsec-size extent of the hard continuum and Fe Kα emission (Papers I and II), we conclude that the AGN in ESO 428-G014 has been active for at least 10⁴ yr. Comparison with the models of Czerny et al. suggests high accretion rates during this activity.

ID: 150511
Type: article
Authors: Maksym, W. Peter; Fabbiano, Giuseppina; Elvis, Martin; Karovska, Margarita; Paggi, Alessandro; Raymond, John; Wang, Junfeng; Storchi-Bergmann, Thaisa; Risaliti, Guido
Abstract: We present spatially resolved Chandra narrow-band imaging and imaging spectroscopy of NGC 3393. This galaxy hosts a Compton-thick Seyfert 2 active galactic nucleus (AGN) with sub-kpc bipolar outflows that are strongly interacting with the circumnuclear gas. We identify narrow-band excess emission associated with the Ne IX 0.905 keV transition (with likely contributions due to intermediate-state iron emission) that points to strong shocks driven by AGN feedback. Imaging spectroscopy resolves outflow-interstellar medium (ISM) interaction sites and the surrounding ISM at ∼100 pc scales, and suggests the presence of a hot AGN wind above the plane at radii beyond the shock sites. The cross-cone shows evidence for reprocessing of photoionization that has passed through gaps in the torus, and also for collisionally excited plasma that may be powered by a shock-confined equatorial outflow. Deep X-ray observations at subarcsecond resolution (such as may be performed very efficiently by Lynx, which would also energetically resolve the complex line emission) are necessary to eliminate model degeneracies and reduce uncertainties in local feedback properties.

ID: 154262
Type: article
Authors: Muñoz-Vergara, Dania; Nagar, Neil M.; Ramakrishnan, Venkatessh; Finlez, Carolina; Storchi-Bergmann, Thaisa; Slater, Roy; Firpo, Veronica; Humire, Pedro K.; Soto-Pinto, Pamela; Kraemer, Steven B.; Lena, Davide; Robinson, Andrew; Riffel, Rogemar A.; Crenshaw, D. Michael; Elvis, Martin S.; Fischer, T. C.; Schnorr-Müller, Allan; Schmitt, Henrique R.
Abstract: As part of a high-resolution observational study of feeding and feedback processes occurring in the vicinity of the active galactic nucleus in 40 galaxies, we observed the inner 3{^''_.}5 × 5 arcsec of the nearby spiral and Seyfert 2 galaxy UGC 2024 with the integral field unit of the Gemini-South Telescope. The observations enabled a study of the stellar and gas kinematics in this region at a spatial resolution of 0{^''_.}5 (218 pc), and a spectral resolution of 36 km s^-1 over the wavelength range 4100-7300 Å. For the strongest emission-lines (H β, [{O III}] λ5007 Å, H α, [{N II}] λ6584 Å, and [{S II}] λλ6717,6731 Å) we derived maps of the flux, radial velocity, and velocity dispersion. The flux distribution and kinematics of the [{O III}] emission line are roughly symmetric around the nucleus: the radial velocity is close to systemic over the full field of view. The kinematics of the other strong emission lines trace both this systemic velocity component, and ordered rotation (with kinematic centre 0{^''_.}2 north-west of the nucleus). The stellar continuum morphology and kinematics are, however, asymmetrical around the nucleus. We interpret these unusual kinematics as the superposition of a component of gas rotating in the galaxy disc plus a `halo' component of highly ionized gas. This halo either traces a quasi-spherical fountain with average radial velocity 200 km s^-1, in which case the total nuclear outflow mass and momentum are 2 × 10⁵ M_☉ and 4 × 10⁷ M_☉ km s^-1, respectively, or a dispersion supported halo created by a past nuclear starburst.