255 research outputs found

    A Tale of Two Narrow-Line Regions: Ionization, Kinematics, and Spectral Energy Distributions for a Local Pair of Merging Obscured Active Galaxies

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    We explore the gas ionization and kinematics, as well as the optical--IR spectral energy distributions for UGC 11185, a nearby pair of merging galaxies hosting obscured active galactic nuclei (AGNs), also known as SDSS J181611.72+423941.6 and J181609.37+423923.0 (J1816NE and J1816SW, z≈0.04z \approx 0.04). Due to the wide separation between these interacting galaxies (∼23\sim 23 kpc), observations of these objects provide a rare glimpse of the concurrent growth of supermassive black holes at an early merger stage. We use BPT line diagnostics to show that the full extent of the narrow line emission in both galaxies is photoionized by an AGN and confirm the existence of a 10-kpc-scale ionization cone in J1816NE, while in J1816SW the AGN narrow-line region is much more compact (1--2 kpc) and relatively undisturbed. Our observations also reveal the presence of ionized gas that nearly spans the entire distance between the galaxies which is likely in a merger-induced tidal stream. In addition, we carry out a spectral analysis of the X-ray emission using data from {\em XMM-Newton}. These galaxies represent a useful pair to explore how the [\ion{O}{3}] luminosity of an AGN is dependent on the size of the region used to explore the extended emission. Given the growing evidence for AGN "flickering" over short timescales, we speculate that the appearances and impact of these AGNs may change multiple times over the course of the galaxy merger, which is especially important given that these objects are likely the progenitors of the types of systems commonly classified as "dual AGNs."Comment: 15 pages, 10 figures, accepted by the Astrophysical Journa

    The X-Ray and Mid-infrared Luminosities in Luminous Type 1 Quasars

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    Several recent studies have reported different intrinsic correlations between the AGN mid-IR luminosity (LMIR) and the rest-frame 2-10 keV luminosity (LX) for luminous quasars. To understand the origin of the difference in the observed LX−LMIR relations, we study a sample of 3,247 spectroscopically confirmed type 1 AGNs collected from Bo\ {o}tes, XMM-COSMOS, XMM-XXL-North, and the SDSS quasars in the Swift/XRT footprint spanning over four orders of magnitude in luminosity. We carefully examine how different observational constraints impact the observed LX−LMIR relations, including the inclusion of X-ray non-detected objects, possible X-ray absorption in type 1 AGNs, X-ray flux limits, and star formation contamination. We find that the primary factor driving the different LX−LMIR relations reported in the literature is the X-ray flux limits for different studies. When taking these effects into account, we find that the X-ray luminosity and mid-IR luminosity (measured at rest-frame 6μm, or L6μm) of our sample of type 1 AGNs follow a bilinear relation in the log-log plane: logLX=(0.84±0.03)×logL6μm/1045ergs−1+(44.60±0.01) for L6μm\u3c1044.79ergs−1, and logLX=(0.40±0.03)×logL6μm/1045ergs−1+(44.51±0.01) for L6μm≥1044.79ergs−1. This suggests that the luminous type 1 quasars have a shallower LX−LMIR correlation than the approximately linear relations found in local Seyfert galaxies. This result is consistent with previous studies reporting a luminosity-dependent LX−LMIR relation, and implies that assuming a linear LX−LMIR relation to infer the neutral gas column density for X-ray absorption might overestimate the column densities in luminous quasar

    The X-Ray and Mid-infrared Luminosities in Luminous Type 1 Quasars

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    Several recent studies have reported different intrinsic correlations between the AGN mid-IR luminosity (LMIR) and the rest-frame 2-10 keV luminosity (LX) for luminous quasars. To understand the origin of the difference in the observed LX−LMIR relations, we study a sample of 3,247 spectroscopically confirmed type 1 AGNs collected from Bo\ {o}tes, XMM-COSMOS, XMM-XXL-North, and the SDSS quasars in the Swift/XRT footprint spanning over four orders of magnitude in luminosity. We carefully examine how different observational constraints impact the observed LX−LMIR relations, including the inclusion of X-ray non-detected objects, possible X-ray absorption in type 1 AGNs, X-ray flux limits, and star formation contamination. We find that the primary factor driving the different LX−LMIR relations reported in the literature is the X-ray flux limits for different studies. When taking these effects into account, we find that the X-ray luminosity and mid-IR luminosity (measured at rest-frame 6μm, or L6μm) of our sample of type 1 AGNs follow a bilinear relation in the log-log plane: logLX=(0.84±0.03)×logL6μm/1045ergs−1+(44.60±0.01) for L6μm\u3c1044.79ergs−1, and logLX=(0.40±0.03)×logL6μm/1045ergs−1+(44.51±0.01) for L6μm≥1044.79ergs−1. This suggests that the luminous type 1 quasars have a shallower LX−LMIR correlation than the approximately linear relations found in local Seyfert galaxies. This result is consistent with previous studies reporting a luminosity-dependent LX−LMIR relation, and implies that assuming a linear LX−LMIR relation to infer the neutral gas column density for X-ray absorption might overestimate the column densities in luminous quasar

    A Tale of Two Narrow-Line Regions: Ionization, Kinematics, and Spectral Energy Distributions for a Local Pair of Merging Obscured Active Galaxies

    Get PDF
    We explore the gas ionization and kinematics, as well as the optical-IR spectral energy distributions for UGC 11185, a nearby pair of merging galaxies hosting obscured active galactic nuclei (AGNs), also known as SDSS J181611.72+423941.6 and J181609.37+423923.0 (J1816NE and J1816SW, z ≈ 0.04). Due to the wide separation between these interacting galaxies (~23 kpc), observations of these objects provide a rare glimpse of the concurrent growth of supermassive black holes at an early merger stage. We use BPT line diagnostics to show that the full extent of the narrow-line emission in both galaxies is photoionized by an AGN, and confirm the existence of a 10 kpc-scale ionization cone in J1816NE, while in J1816SW the AGN narrow-line region is much more compact (1–2 kpc) and relatively undisturbed. Our observations also reveal the presence of ionized gas that nearly spans the entire distance between the galaxies, which is likely in a merger-induced tidal stream. In addition, we carry out a spectral analysis of the X-ray emission using data from XMM-Newton. These galaxies represent a useful pair to explore how the [O iii] luminosity of an AGN is dependent on the size of the region used to explore the extended emission. Given the growing evidence for AGN flickering over short timescales, we speculate that the appearances and impacts of these AGNs may change multiple times over the course of the galaxy merger, which is especially important given that these objects are likely the progenitors of the types of systems commonly classified as dual AGNs

    HyCon - a virtual reality design support tool for hybrid concrete structural frames

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    Hybrid concrete can provide high quality, cost effective structural frames in a variety of situations when compared to other, more conventional, solutions such as in-situ concrete and steel frames. The key players in the design and construction supply chain process for hybrid concrete are lead frame contractors and design engineers. The use of hybrid concrete, however, is sometimes not considered by contractors and designers during the initial stages of design. This is often because of a lack of reliable and accessible hybrid concrete cost and production time information. Without this information, contractors and designers may disregard hybrid concrete as a design alternative, potentially omitting the most appropriate solution before it has even been considered. This paper reports on a collaborative research project in the United Kingdom which has developed HyCon - a prototype design support tool which allows contractors and designers at the conceptual design stage to carry out "what if?" analysis in a virtual reality environment to consider various hybrid concrete alternatives against a range of 'hard' and 'soft' performance criteria. The 'hard' criteria allow contractors and designers to assess initial and whole life cycle cost and production duration implications. The 'soft' criteria encourage the whole project team to assess and prioritise the importance and performance of design alternatives against criteria such as physical form and space

    Single Gene Deletions of Orexin, Leptin, Neuropeptide Y, and Ghrelin Do Not Appreciably Alter Food Anticipatory Activity in Mice

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    Timing activity to match resource availability is a widely conserved ability in nature. Scheduled feeding of a limited amount of food induces increased activity prior to feeding time in animals as diverse as fish and rodents. Typically, food anticipatory activity (FAA) involves temporally restricting unlimited food access (RF) to several hours in the middle of the light cycle, which is a time of day when rodents are not normally active. We compared this model to calorie restriction (CR), giving the mice 60% of their normal daily calorie intake at the same time each day. Measurement of body temperature and home cage behaviors suggests that the RF and CR models are very similar but CR has the advantage of a clearly defined food intake and more stable mean body temperature. Using the CR model, we then attempted to verify the published result that orexin deletion diminishes food anticipatory activity (FAA) but observed little to no diminution in the response to CR and, surprisingly, that orexin KO mice are refractory to body weight loss on a CR diet. Next we tested the orexigenic neuropeptide Y (NPY) and ghrelin and the anorexigenic hormone, leptin, using mouse mutants. NPY deletion did not alter the behavior or physiological response to CR. Leptin deletion impaired FAA in terms of some activity measures, such as walking and rearing, but did not substantially diminish hanging behavior preceding feeding time, suggesting that leptin knockout mice do anticipate daily meal time but do not manifest the full spectrum of activities that typify FAA. Ghrelin knockout mice do not have impaired FAA on a CR diet. Collectively, these results suggest that the individual hormones and neuropepetides tested do not regulate FAA by acting individually but this does not rule out the possibility of their concerted action in mediating FAA

    The X-ray and mid-infrared luminosities in luminous type 1 quasars

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    Several recent studies have reported different intrinsic correlations between the active galactic nucleus (AGN) mid-IR luminosity (LMIR{L}_{\mathrm{MIR}}) and the rest-frame 2–10 keV luminosity (L X) for luminous quasars. To understand the origin of the difference in the observed {L}_{{\rm{X}}}\mbox{--}{L}_{\mathrm{MIR}} relations, we study a sample of 3247 spectroscopically confirmed type 1 AGNs collected from Boötes, XMM-COSMOS, XMM-XXL-North, and the Sloan Digital Sky Survey quasars in the Swift/XRT footprint spanning over four orders of magnitude in luminosity. We carefully examine how different observational constraints impact the observed {L}_{{\rm{X}}}\mbox{--}{L}_{\mathrm{MIR}} relations, including the inclusion of X-ray-nondetected objects, possible X-ray absorption in type 1 AGNs, X-ray flux limits, and star formation contamination. We find that the primary factor driving the different {L}_{{\rm{X}}}\mbox{--}{L}_{\mathrm{MIR}} relations reported in the literature is the X-ray flux limits for different studies. When taking these effects into account, we find that the X-ray luminosity and mid-IR luminosity (measured at rest-frame 6 μm6\,\mu {\rm{m}}, or L6μm{L}_{6\mu {\rm{m}}}) of our sample of type 1 AGNs follow a bilinear relation in the log–log plane: logLX=(0.84±0.03)×logL6μm/1045\mathrm{log}{L}_{{\rm{X}}}=(0.84\pm 0.03)\times \mathrm{log}{L}_{6\mu {\rm{m}}}/{10}^{45} erg s−1 + (44.60 ± 0.01) for L6μm<1044.79{L}_{6\mu {\rm{m}}}\lt {10}^{44.79} erg s−1, and logLX=(0.40±0.03)×logL6μm/1045\mathrm{log}{L}_{{\rm{X}}}=(0.40\pm 0.03)\times \mathrm{log}{L}_{6\mu {\rm{m}}}/{10}^{45} erg s−1 + (44.51 ± 0.01) for L6μm ⩾1044.79{L}_{6\mu {\rm{m}}}\,\geqslant {10}^{44.79} erg s−1. This suggests that the luminous type 1 quasars have a shallower {L}_{{\rm{X}}}\mbox{--}{L}_{6\mu {\rm{m}}} correlation than the approximately linear relations found in local Seyfert galaxies. This result is consistent with previous studies reporting a luminosity-dependent {L}_{{\rm{X}}}\mbox{--}{L}_{\mathrm{MIR}} relation and implies that assuming a linear {L}_{{\rm{X}}}\mbox{--}{L}_{6\mu {\rm{m}}} relation to infer the neutral gas column density for X-ray absorption might overestimate the column densities in luminous quasars

    The Chandra Deep Wide-field Survey: A New Chandra Legacy Survey in the Boötes Field. I. X-Ray Point Source Catalog, Number Counts, and Multiwavelength Counterparts

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    We present a new, ambitious survey performed with the Chandra X-ray Observatory of the 9.3 deg2 Boötes field of the NOAO Deep Wide-Field Survey. The wide field probes a statistically representative volume of the universe at high redshift. The Chandra Deep Wide-field Survey exploits the excellent sensitivity and angular resolution of Chandra over a wide area, combining 281 observations spanning 15 yr, for a total exposure time of 3.4 Ms, and detects 6891 X-ray point sources down to limiting fluxes of 4.7 × 10−16, 1.5 × 10−16, and 9 ×10−16 erg cm−2 s−1 in the 0.5–7, 0.5–2, and 2–7 keV bands, respectively. The robustness and reliability of the detection strategy are validated through extensive, state-of-the-art simulations of the whole field. Accurate number counts, in good agreement with previous X-ray surveys, are derived thanks to the uniquely large number of point sources detected, which resolve 65.0% ± 12.8% of the cosmic X-ray background between 0.5 and 2 keV and 81.0% ± 11.5% between 2 and 7 keV. Exploiting the wealth of multiwavelength data available on the field, we assign redshifts to ~94% of the X-ray sources, estimate their obscuration, and derive absorption-corrected luminosities. We provide an electronic catalog containing all of the relevant quantities needed for future investigations
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