Using a combination of deep (574 ks) Chandra data, XMM–Newton high-resolution spectra and optical Hα+N ii images, we study the nature and spatial distribution of the multi-phase plasma in M87. Our ...results provide direct observational evidence of ‘radio-mode’ active galactic nuclei (AGN) feedback in action, stripping the central galaxy of its lowest entropy gas and therefore preventing star formation. This low entropy gas was entrained with and uplifted by the buoyantly rising relativistic plasma, forming long ‘arms’. A number of arguments suggest that these arms are oriented within 15°–30° of our line-of-sight. The mass of the uplifted gas in the arms is comparable to the gas mass in the approximately spherically symmetric 3.8 kpc core, demonstrating that the AGN has a profound effect on its immediate surroundings. The coolest X-ray emitting gas in M87 has a temperature of ∼0.5 keV and is spatially coincident with Hα+N ii nebulae, forming a multi-phase medium where the cooler gas phases are arranged in magnetized filaments. We place strong upper limits of 0.06 M⊙ yr−1 (at 95 per cent confidence) on the amount of plasma cooling radiatively from 0.5 to 0.25 keV and show that a uniform, volume-averaged heating mechanism could not be preventing the cool gas from further cooling. All of the bright Hα filaments in M87 appear in the downstream region of the <3 Myr old shock front, at smaller radii than ∼0.6 arcmin. We suggest that shocks induce shearing around the filaments, thereby promoting mixing of the cold gas with the ambient hot intra-cluster medium (ICM) via instabilities. By bringing hot thermal particles into contact with the cool, line-emitting gas, mixing can supply the power and ionizing particles needed to explain the observed optical spectra. Furthermore, mixing of the coolest X-ray emitting plasma with the cold optical line-emitting filamentary gas promotes efficient conduction between the two phases, allowing non-radiative cooling which could explain the lack of X-ray gas with temperatures under 0.5 keV.
We report the results of a multiwavelength study of the nearby galaxy group, Abell 3581 (z = 0.0218). This system hosts the most luminous cool core of any nearby group and exhibits active radio mode ...feedback from the supermassive black hole in its brightest group galaxy, IC 4374. The brightest galaxy has suffered multiple active galactic nucleus outbursts, blowing bubbles into the surrounding hot gas, which have resulted in the uplift of cool ionized gas into the surrounding hot intragroup medium. High velocities, indicative of an outflow, are observed close to the nucleus and coincident with the radio jet. Thin dusty filaments accompany the uplifted, ionized gas. No extended star formation is observed; however, a young cluster is detected just north of the nucleus. The direction of rise of the bubbles has changed between outbursts. This directional change is likely due to sloshing motions of the intragroup medium. These sloshing motions also appear to be actively stripping the X-ray cool core, as indicated by a spiralling cold front of high-metallicity, low-temperature, low entropy gas.
Bagana is a remote, highly active volcano, located on Bougainville Island in southeastern Papua New Guinea. The volcano has exhibited sustained and prodigious sulfur dioxide gas emissions in recent ...decades, accompanied by frequent episodes of lava extrusion. The remote location of Bagana and its persistent activity have made it a valuable case study for satellite observations of active volcanism. This remoteness has also left many features of Bagana relatively unexplored. Here, we present the first measurements of volcanic gas composition, achieved by unoccupied aerial system (UAS) flights through the volcano's summit plume, and a payload comprising a miniaturized MultiGAS. We combine our measurements of the molar CO2/SO2 ratio in the plume with coincident remote sensing measurements (ground‐ and satellite‐based) of SO2 emission rate to compute the first estimate of CO2 flux at Bagana. We report low SO2 and CO2 fluxes at Bagana from our fieldwork in September 2019, ∼320 ± 76 td−1 and ∼320 ± 84 td−1, respectively, which we attribute to the volcano's low level of activity at the time of our visit. We use satellite observations to demonstrate that Bagana's activity and emissions behavior are highly variable and advance the argument that such variability is likely an inherent feature of many volcanoes worldwide and yet is inadequately captured by our extant volcanic gas inventories, which are often biased to sporadic measurements. We argue that there is great value in the use of UAS combined with MultiGAS‐type instruments for remote monitoring of gas emissions from other inaccessible volcanoes.
Plain Language Summary
Bagana is a remote and highly active volcano in southeastern Papua New Guinea (PNG). Historically, it has been among the most active volcanoes in PNG, notable for its long‐lived eruptions and sustained gas emissions. Bagana has only been infrequently studied before now. We use unoccupied aerial systems (drones) along with ground‐ and satellite‐based remote sensing data to characterize the chemical composition and flux of Bagana's gas emissions and place these in the context of global volcanic emissions. Owing to low activity during the time of our fieldwork, we report lower than anticipated emissions of carbon dioxide and sulfur dioxide from Bagana. We argue that characterizing highly variable volcanic emissions is challenging without long‐term continuous observations and that, for remote volcanoes like Bagana, both drones and satellite observations are powerful tools to undertake these observations.
Key Points
We present the first measurements of volcanic gas composition at Bagana volcano
CO2 and SO2 fluxes at Bagana vary widely with levels of unrest, from ∼102 to ∼104 td−1
Unoccupied aerial systems (drones) are of great value in monitoring emissions from inaccessible volcanic summits
We report on investigations of the interaction of light with nanoscale antennae made from crystalline GaP nanowires (NWs). Using Raman scattering, we have observed strong optical antenna effects ...which we identify with internal standing wave photon modes of the wire. The antenna effects were probed in individual NWs whose diameters are in the range 40 < d < 300 nm. The data and our calculations show that the nature of the backscattered light is critically dependent on the interplay between a photon confinement effect and bulk Raman scattering. At small diameter, d < 65 nm, the NWs are found to act like a nearly perfect dipole antenna and the bulk Raman selection rules are masked leading to a polarized scattering intensity function I R ∼ cos4 θ. Underscoring the importance of this work is the realization that a fundamental understanding of the “optical antenna effect” in semiconducting NWs is essential to the analysis of all electro-optic effects in small diameter filaments.
AIMS; It is well established that glaucoma results in a thinning of the inner retina. To investigate whether the outer retina is also involved, ultrahigh-resolution retinal imaging techniques were ...utilised.
Eyes from 10 glaucoma patients (25-78 years old), were imaged using three research-grade instruments: (1) ultrahigh-resolution Fourier-domain optical coherence tomography (UHR-FD-OCT), (2) adaptive optics (AO) UHR-FD-OCT and (3) AO-flood illuminated fundus camera (AO-FC). UHR-FD-OCT and AO-UHR-FD-OCT B-scans were examined for any abnormalities in the retinal layers. On some patients, cone density measurements were made from the AO-FC en face images. Correlations between retinal structure and visual sensitivity were measured by Humphrey visual-field (VF) testing made at the corresponding retinal locations.
All three in vivo imaging modalities revealed evidence of outer retinal changes along with the expected thinning of the inner retina in glaucomatous eyes with VF loss. AO-UHR-FD-OCT images identified the exact location of structural changes within the cone photoreceptor layer with the AO-FC en face images showing dark areas in the cone mosaic at the same retinal locations with reduced visual sensitivity.
Losses in cone density along with expected inner retinal changes were demonstrated in well-characterised glaucoma patients with VF loss.
Purpose
To assess radiation therapy (RT)-induced vasculitis in patients with non-small cell lung cancer (NSCLC) by examining changes in the uptake of
18
F-fluoro-D-deoxyglucose (
18
FFDG) by positron ...emission tomography/computed tomography (PET/CT) images of the ascending aorta (AA), descending aorta (DA), and aortic arch (AoA) before and after proton and photon RT.
Method
Thirty-five consecutive locally advanced NSCLC patients were definitively treated with proton (
n
= 27) or photon (
n
= 8) RT and concurrent chemotherapy. The patients were prospectively enrolled to undergo
18
FFDG-PET/CT imaging before and 3 months after RT. An adaptive contrast-oriented thresholding algorithm was applied to generate mean standardized uptake values (SUVmean) for regions of interest (ROIs) 3 mm outside and 3 mm inside the outer perimeter of the AA, DA, and AoA. These ROIs were employed to exclusively select the aortic wall and remove the influence of blood pool activity. SUVmeans before and after RT were compared using two-tailed paired
t
-tests.
Results
RT treatments were associated with increased SUVmeans in the AA, DA, and AoA—1.9%, 0.3%, and 1.3% for proton and 15.8%, 9.5%, and 15.5% for photon, respectively. There was a statistically significant difference in the ∆SUVmean (post-RT SUVmean − pre-RT SUVmean) in patients treated with photon RT when compared to ∆SUVmean in patients treated with proton RT in the AA (
p
= 0.043) and AoA (
p
= 0.015). There was an average increase in SUVmean that was related to dose for photon patients (across structures), but that was not seen for proton patients, although the increase was not statistically significant.
Conclusion
Our results suggest that patients treated with photon RT for NSCLC may exhibit significantly more RT-induced inflammation (measured as ∆SUVmean) in the AA and AoA when compared to patients who received proton RT. Knowledge gained from further analyses in larger cohorts could aid in treatment planning and help prevent the significant morbidity and mortality associated with RT-induced vascular complications.
Trial registration
NCT02135679.
We present the first in a series of papers discussing the thermodynamic properties of M87 and the central regions of the Virgo Cluster in unprecedented detail. Using a deep Chandra exposure (574 ks), ...we present high-resolution thermodynamic maps created from the spectra of ∼16 000 independent regions, each with ∼1000 net counts. The excellent spatial resolution of the thermodynamic maps reveals the dramatic and complex temperature, pressure, entropy and metallicity structure of the system. The ‘X-ray arms’, driven outwards from M87 by the central active galactic nuclei (AGN), are prominent in the brightness, temperature and entropy maps. Excluding the ‘X-ray arms’, the diffuse cluster gas at a given radius is strikingly isothermal. This suggests either that the ambient cluster gas, beyond the arms, remains relatively undisturbed by AGN uplift or that conduction in the intracluster medium (ICM) is efficient along azimuthal directions, as expected under action of the heat-flux-driven buoyancy instability (HBI). We confirm the presence of a thick (∼40 arcsec or ∼3 kpc) ring of high-pressure gas at a radius of ∼180 arcsec (∼14 kpc) from the central AGN. We verify that this feature is associated with a classical shock front, with an average Mach number M= 1.25. Another, younger shock-like feature is observed at a radius of ∼40 arcsec (∼3 kpc) surrounding the central AGN, with an estimated Mach number M≳ 1.2. As shown previously, if repeated shocks occur every ∼10 Myr, as suggested by these observations, then AGN-driven weak shocks could produce enough energy to offset radiative cooling of the ICM. A high significance enhancement of Fe abundance is observed at radii 350–400 arcsec (27–31 kpc). This ridge is likely formed in the wake of the rising bubbles filled with radio-emitting plasma that drag cool, metal-rich gas out of the central galaxy. We estimate that at least ∼1.0 × 106 solar masses of Fe has been lifted and deposited at a radius of 350–400 arcsec; approximately the same mass of Fe is measured in the X-ray bright arms, suggesting that a single generation of buoyant radio bubbles may be responsible for the observed Fe excess at 350–400 arcsec.
The aim of this study is to understand the trade-off between crystal thickness and scanner axial field-of-view FOV (AFOV) for clinical PET imaging. Clinical scanner design has evolved towards 20-25 ...mm thick crystals and 16-22 cm long scanner AFOV, as well as time-of-flight (TOF) imaging. While Monte Carlo studies demonstrate that longer AFOV and thicker crystals will lead to higher scanner sensitivity, cost has prohibited the building of commercial scanners with >22 cm AFOV. In this study, we performed a series of system simulations to optimize the use of a given amount of crystal material by evaluating the impact on system sensitivity and noise equivalent counts (NEC), as well as image quality in terms of lesion detectability. We evaluated two crystal types (LSO and LaBr3) and fixed the total crystal volume used for each type (8.2 L of LSO and 17.1 L of LaBr3) while varying the crystal thickness and scanner AFOV. In addition, all imaging times were normalized so that the total scan time needed to scan a 100 cm long object with multiple bed positions was kept constant. Our results show that the highest NEC cm(-1) in a 35 cm diameter ×70 cm long line source cylinder is achieved for an LSO scanner with 10 mm long crystals and AFOV of 36 cm, while for LaBr3 scanners, the highest NEC cm(-1) is obtained with 20 mm long crystals and an AFOV of 38 cm. Lesion phantom simulations show that the best lesion detection performance is achieved in scanners with long AFOV (≥36 cm) and using thin crystals (≤10 mm of LSO and ≤20 mm of LaBr3). This is due to a combination of improved NEC, as well as improved lesion contrast estimation due to better spatial resolution in thinner crystals. Alternatively, for lesion detection performance similar to that achieved in standard clinical scanner designs, the long AFOV scanners can be used to reduce the total scan time without increasing the amount of crystal used in the scanner. In addition, for LaBr3 based scanners, the reduced lesion contrast relative to LSO based scanners requires improved timing resolution and longer scan times in order to achieve lesion detectability similar to that achieved in an LSO scanner with similar NEC cm(-1).
We report on a deep, multiwavelength study of the galaxy cluster MACS J1931.8−2634 using Chandra X-ray, Subaru optical and Very Large Array 1.4-GHz radio data. This cluster (z= 0.352) harbours one of ...the most X-ray luminous cool cores yet discovered, with an equivalent mass, cooling rate within the central
is ∼700 M⊙ yr−1. Unique features observed in the central core of MACS J1931.8−2634 hint to a wealth of past activity that has greatly disrupted the original cool core. The X-ray and optical data suggest oscillatory motion of the cool core along a roughly north-south direction. We also observe a spiral of relatively cool, dense, X-ray emitting gas connected to the cool core, as well as highly elongated intracluster light (ICL) surrounding the cD galaxy. For a cluster with such a high-nominal cooling rate, this cluster is missing the central metallicity peak almost always seen in the cool-core clusters, which suggest bulk transport of cool gas out to large distances from the centre. Extended radio emission is observed surrounding the central active galactic nucleus (AGN), elongated in the east-west direction, spatially coincident with X-ray cavities. The power input required to inflate these 'bubbles' is estimated from both the X-ray and radio emission to reside between P
jet∼ 4-14 × 1045 erg s−1, putting it among the most powerful jets ever observed. This combination of a powerful AGN outburst and bulk motion of the cool core has resulted in two X-ray bright ridges to form to the north and south of the central AGN at a distance of approximately 25 kpc. The northern ridge has spectral characteristics typical of cool cores: it contains low-temperature high-density metal-rich gas and is consistent with being a remnant of the cool core after it was disrupted by the AGN and bulk motions. It is also the site of Hα filaments and young stars. The X-ray spectroscopic cooling rate associated with this ridge is ∼165 M⊙ yr−1, which agrees with the estimate of the star formation rate from broad-band optical imaging (∼170 M⊙ yr−1). MACS J1931.8−2634 appears to harbour one of the most profoundly disrupted low-entropy cores observed in a cluster, and offers new insights into the survivability of cool cores in the context of hierarchical structure formation.
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