Disk Component Research Articles

Intradural disc herniation: A case report and literature review

Background: Intradural disc herniation (IDH) is rare and is thought to be caused by posterior longitudinal ligament and posterior adhesions. MRI findings are inadequate for definitive diagnosis. We reported a patient with an L4-5 IDH and reviewed the literature.
 Case Description: A 71-year-old male patient presented with acute exacerbation of right lower extremity radiculopathy. MRI with/without contrast suggested IDH and spinal cord compression at the L4-5 spine level. While elective surgery was planned for the patient who did not have motor deficits at the time of admission, he underwent emergency surgery due to sudden urinary incontinence. At surgery, the disc herniation was appropriately resected, the dura was closed.
 Conclusion: Although MRI is helpful in the diagnosis of IDH, the definitive diagnosis is made intraoperatively. In surgery, both the extradural and intradural disc components should be removed and as small laminectomy and dura incision as possible.

Evolution of the Spin, Spectrum and Superorbital Period of the Ultraluminous X-Ray Pulsar M51 ULX7

Abstract M51 ULX7 is among a small group of known ultraluminous X-ray pulsars (ULXPs). The neutron star powering the source has a spin period of 2.8 s, orbits its companion star with a period of 2 days, and a superorbital period of 38 days is evident in its X-ray lightcurve. Here we present NuSTAR and XMM-Newton data on the source from 2019 obtained when the source was near its peak brightness. We detect the pulsations, having spun up at a rate of 3 ± 0.5 × 10−10 s s−1 since they were previously detected in 2018. The data also provide the first high-quality broadband spectrum of the source. We find it to be very similar to that of other ULXPs, with two disk-like components, and a high-energy tail. When combined with XMM-Newton data obtained in 2018, we explore the evolution of the spectral components with superorbital phase, finding that the luminosity of the hotter component drives the superorbital flux modulation. The inclination the disk components appear to change with phase, which may support the idea that these superorbital periods are caused by disk precession. We also reexamine the superorbital period with 3 yr of Swift/XRT monitoring, finding that the period is variable, increasing from 38.2 ± 0.5 days in 2018–2019 to 44.2 ± 0.9 days in 2020–2021, which rules out alternative explanations for the superorbital period.

Comparison of aero engine component lifing methods

Failure of critical engine components such as compressor, fan, and turbine disks during flight can cause the loss of the engine, aircraft, or even life. To reduce the risk of this failure during flight, different methodologies and tools have been developed to determine the safe operating life of these critical disk components. The two most widely used lifing methods, safe-life and damage tolerance, are inherently conservative, retiring all components when a predetermined operating limit is reached. Both methods retire components with theoretical useful life remaining. Additional lifing methods can be used to reduce this conservatism and extend the life of these components. Retirement for cause, developed within the United States Air Force is a lifing method that can extend the life of components by retiring a component only when there is cause to do so. Military and industry standards on lifing methodologies were reviewed. Both deterministic and probabilistic approaches to disk lifing methods are discussed as well as current tools. This paper provides a comparison of the methodologies and tools currently being used today by both the government and industry.

AstroSat View of Spectral Transition in the Changing-look Active Galaxy NGC 1566 during the Declining Phase of the 2018 Outburst

Abstract NGC 1566 is a changing-look active galaxy that exhibited an outburst during 2017–2018 with a peak in 2018 June. We triggered AstroSat observations of NGC 1566 twice in 2018 August and October during its declining phase. Using the AstroSat observations, along with two XMM-Newton observations in 2015 (pre-outburst) and 2018 June (peak outburst), we found that the X-ray power law, the soft X-ray excess, and the disk components showed extreme variability during the outburst. Especially, the soft excess was negligible in 2015 before the outburst, increased to a maximum level by a factor of >200 in 2018 June, and reduced dramatically by a factor of ∼7.4 in 2018 August and became undetectable in 2018 October. The Eddington fraction (L/L Edd) increased from ∼0.1% (2015) to ∼5% (2018 June) and then decreased to ∼1.5% (2018 August) and 0.3% (2018 October). Thus, NGC 1566 made a spectral transition from a high soft-excess state to a negligible soft-excess state at a few percent of the Eddington rate. The soft excess is consistent with warm Comptonization in the inner disk that appears to have developed during the outburst and disappeared toward the end of the outburst over a timescale comparable to the sound-crossing time. The multiwavelength spectral evolution of NGC 1566 during the outburst is most likely caused by the radiation pressure instability in the inner regions of the accretion disk in NGC 1566.

On the Formation of Spiral Arms in Dwarf Galaxies

Spiral structure (both flocculent and Grand Design types) is very rarely observed in dwarf galaxies because the formation of spiral arms requires special conditions. In this work we analyze the sample of about 40 dS-galaxies found by scanning by eye the images of late-type galaxies with $m_B<15^m$ and $M_B>-18^m$ and photometric diameter $D_{25}<12$~kpc. We found that apart from the lower average gas (HI) fraction the other properties of dS-galaxies including the presence of a bar and the isolation index do not differ much from those for dwarf Irr or Sm-types of similar luminosity and rotation velocity (or specific angular momentum).There are practically no dS-galaxies with rotation velocity below 50\,--\,60~km\,sec$^{-1}$. To check the conditions of formation of spiral structure in dwarf galaxies we carried out a series of N-body/hydrodynamic simulations of low-mass stellar-gaseous discy galaxies by varying the model kinematic parameters of discs, their initial thickness, relative masses and scale lengths of stellar and gaseous disc components, and stellar-to-dark halo masses. We came to conclusion that the gravitational mechanism of spiral structure formation is effective only for thin stellar discs, which are non-typical for dwarf galaxies, and for not too slowly rotating galaxies. Therefore, only a small fraction of dwarf galaxies with stellar/gaseous discs have spiral or ring structures. The thicker stellar disc, the more gas is required for the spiral structure to form. The reduced gas content in many dS-galaxies compared to non-spiral ones may be a result of more efficient star formation due to a higher volume gas density thank to the thinner stellar/gaseous discs.

XGASS: characterizing the slope and scatter of the stellar mass–angular momentum relation for nearby galaxies

ABSTRACT We present a detailed study of the stellar mass versus specific angular momentum (AM) relation (Fall relation) for a representative sample of 564 nearby galaxies in the eXtended GALEX Arecibo SDSS Survey (xGASS). We focus on the dependence of the Fall relation’s slope on galaxy type and the galaxy properties regulating its scatter. Stellar specific AM is determined by combining single-dish H i velocity widths and stellar mass profiles for all H i detections in the xGASS sample. At fixed morphology (or bulge-to-total ratio), we find that the power-law slope of the Fall relation is consistent with 2/3. However, when all galaxy types are combined, we recover a much shallower slope of ∼0.47. We show that this is a consequence of the change in galaxy morphology as a function of mass, highlighting that caution should be taken when using the slope of the Fall relation to constrain galaxy formation models without taking sample selection into account. We quantify the Fall relations scatter and show that H i gas fraction is the strongest correlated parameter for low stellar masses (Spearman correlation: ρs = 0.61), while the bulge-to-total ratio becomes slightly more dominant at higher masses (ρs = −0.29). Intriguingly, when only the disc components of galaxies are considered, H i gas fraction remains the strongest correlated parameter with the scatter of the relation (regardless of disc stellar mass). Our work provides one of the best characterizations of the Fall relation for a representative sample of galaxies in the local Universe.

Gemini NIFS survey of feeding and feedback in nearby active galaxies – V. Molecular and ionized gas kinematics

ABSTRACT We study the gas distribution and kinematics of the inner kpc of six moderately luminous (43.43 ≤ log Lbol ≤ 44.83) nearby (0.004 ≤ z ≤ 0.014) Seyfert galaxies observed with the Near-infrared Integral Field Spectrograph (NIFS) in the J ($1.25\,\mu$m) and K ($2.2\,\mu$m) bands. We analyse the most intense emission lines detected on these spectral wavebands: [Fe ii] $1.2570\, \mu$m and Paβ, which trace the ionized gas in the partially and fully ionized regions, and $\mathrm{ H}_2 \ 2.1218\, \mu$m, which traces the hot (∼2000 K) molecular gas. The dominant kinematic component is rotation in the disc of the galaxies, except for the ionized gas in NGC 5899 that shows only weak signatures of a disc component. We find ionized gas outflow in four galaxies, while signatures of H2 outflows are seen in three galaxies. The ionized gas outflows display velocities of a few hundred km s−1, and their mass outflow rates are in the range 0.005–12.49 M⊙ yr−1. Their kinetic powers correspond to 0.005–0.7 per cent of the active galactic nuclei (AGN) bolometric luminosities. Besides rotation and outflows signatures in some cases, the H2 kinematics also reveals inflows in three galaxies. The inflow velocities are 50–80 km s−1 and the mass inflow rates are in the range 1–9 × 10−4 M⊙ yr−1 for hot molecular gas. These inflows might be only the hot skin of the total inflowing gas, which is expected to be dominated by colder gas. The mass inflow rates are lower than the current accretion rates to the AGN, and the ionized outflows are apparently disturbing the gas in the inner kpc.

Synchronized Coevolution between Supermassive Black Holes and Galaxies over the Last Seven Billion Years as Revealed by Hyper Suprime-Cam

Abstract We measure the evolution of the  BH –  ⋆ relation using 584 uniformly selected Sloan Digital Sky Survey quasars at 0.2 &lt; z &lt; 0.8. The black hole masses (  BH ) are derived from the single-epoch virial mass estimator using the Hβ emission line and span the range 7.0 &lt; log  BH / M ⊙ &lt; 9.5 . The host-galaxy stellar masses (  ⋆ ), which cover the interval 10.0 &lt; log  ⋆ / M ⊙ &lt; 11.5 , are determined by performing two-dimensional quasar-host decomposition of the Hyper Suprime-Cam images and spectral energy distribution fitting. To quantify sample selection biases and measurement uncertainties on the mass terms, a mock quasar sample is constructed to jointly constrain the redshift evolution of the  BH –  ⋆ relation and its intrinsic scatter (σ μ ) through forward modeling. We find that the level of evolution is degenerate with σ μ , such that both a positive mild evolution (i.e.,  BH /  ⋆ increases with redshift) with a small σ μ and a negative mild evolution with a larger σ μ are consistent with our data. The posterior distribution of σ μ enables us to put a strong constraint on the intrinsic scatter of the  BH –  ⋆ relation, which has a best inference of 0.25 − 0.04 + 0.03 dex, consistent with the local value. The redshift evolution of the  BH –  ⋆ relation relative to the local relation is constrained to be 1 + z 0.12 − 0.27 + 0.28 , in agreement with no significant evolution since z ∼ 0.8. The tight and unevolving  BH –  ⋆ relation is suggestive of a coupling through active galactic nuclei feedback or/and a common gas supply at work, thus restricting the mass ratio of galaxies and their black holes to a limited range. Given the considerable stellar disk component, the  BH –  bulge relation may evolve as previously seen at higher redshifts.

Probabilistic model for dynamic galaxy decomposition

ABSTRACT In the era of precision cosmology and ever-improving cosmological simulations, a better understanding of different galaxy components such as bulges and discs will give us new insight into galactic formation and evolution. Based on the fact that the stellar populations of the constituent components of galaxies differ by their dynamical properties, we develop two simple models for galaxy decomposition using the TNG100 cosmological hydrodynamical simulation from the IllustrisTNG project. The first model uses a single dynamical parameter and can distinguish four components: thin disc, thick disc, counter-rotating disc, and bulge. The second model uses one more dynamical parameter, was defined in a probabilistic manner, and distinguishes two components: bulge and disc. We demonstrate the improved robustness of these models compared to a widely used method in literature involving cuts on the circularity parameter. The number fraction of disc-dominated galaxies at a given stellar mass obtained by our models agrees well with observations for masses exceeding log10(M*/M⊙) = 10. The galaxies classified as bulge-dominated by the second model are mostly red; however, the population classified as disc-dominated contains significant number of red galaxies alongside the blue population. The contributions of the different galaxy components to the total stellar mass budget exhibits similar trends with stellar mass compared to the observational data, although there is a quantitative disagreement at high and low masses. The Sérsic indices and half-mass radii for the bulge and disc components agree well with those of real galaxies.

Quantitative polarimetry of the disk around HD 169142

Context. Many scattered light images of protoplanetary disks have been obtained with the new generation of adaptive optics (AO) systems at large telescopes. The measured scattered radiation can be used to constrain the dust that forms planets in these disks. Aims. We want to constrain the dust particle properties for the bright, pole-on transition disk around HD 169142 with accurate measurements and a quantitative analysis for the polarization and intensity of the scattered radiation. Methods. We investigate high resolution imaging polarimetry of HD 169142 taken in the R′ and I′ bands with the SPHERE/ZIMPOL AO instrument. The geometry of this pole-on disk is close to rotational symmetry, and we can use azimuthally averaged radial profiles for our analysis. We describe the dependence of the disk polarimetry on the atmospheric turbulence, which strongly impacts the AO point spread function (PSF). With non-coronagraphic data we can analyze the polarimetric signal of the disk simultaneously with the stellar PSF and determine the polarization of the disk based on simulations of the PSF convolution. We also extract the disk intensity signal and derive the fractional polarization for the R′ and I′ bands. We compare the scattered flux from the inner and outer disk rings with the corresponding thermal dust emissions measured in the IR and estimate the ratio between scattered and absorbed radiation. Results. We find for the inner and outer disk rings of HD 169142 mean radii of 170 ± 3 mas and 522 ± 20 mas, respectively, and the same small deviations from a perfect ring geometry as previous studies. The AO performance shows strong temporal variation because of the mediocre seeing of about 1.1″; this produces PSF peak variations of up to a factor of four and strongly correlated changes for the measured disk polarization of about a factor of two for the inner disk ring and about 1.2 for the more extended outer disk. This variable PSF convolution effect can be simulated and accurately corrected, and we obtain ratios between the integrated disk polarization flux and total system flux (Q̂ϕ/Itot) of 0.43 ± 0.01% for the R′ band and 0.55 ± 0.01% for the I′ band. This indicates a reddish color for the light reflection by the dust. The inner disk ring contributes about 75% and the outer disk about 25% to the total disk flux. The extraction of the scattered intensity of the disk is only possible for the bright, narrow, inner disk ring, and the obtained fractional polarization p̂ for the scattered radiation is 23.6 ± 3.5% for the I′ band and 22.0 ± 5.9% for the R′ band. The ratio between scattered disk flux and star flux (Îdisk/I⋆) is about 2.3 ± 0.3%. This is much smaller than the derived IR excess FfIR/F⋆ = 17.6% for the disk components observed in scattered light. This indicates that only a small fraction of the radiation illuminating the disk is scattered; most is absorbed and reemitted in the IR. Conclusions. We demonstrate the feasibility of accurate quantitative photo-polarimetry of a circumstellar disk with a radius of less than 0.2″, observed with ground-based AO systems, if the PSF convolution effects can be properly taken into account. Accurate measurements are a pre-requisite for finding differences in the dust properties for different disks. The derived fractional polarization of about 23% in the R′ and I′ bands for the compact (20 AU) inner disk of HD 169142 is lower than the measurement for the more extended disk HD 142527 for the same wavelength range and significantly lower than the estimates for near-IR data of other extended protoplanetary disks.

Stellar Populations of Spectroscopically Decomposed Bulge–Disk for S0 Galaxies from the CALIFA Survey

Abstract We investigate the stellar population properties of bulges and disks separately for 34 S0s using integral-field spectroscopy from the Calar Alto Legacy Integral Field Area survey. The spatially resolved stellar age and metallicity of bulge and disk components are simultaneously estimated using the penalized pixel fitting method with photometrically defined weights for the two components. We find a tight correlation between age and metallicity for bulges, while the relation for disks has a larger scatter than that for bulges. This implies that the star formation histories of disks are more complicated than those of bulges. The bulges of high-mass S0s are mostly comparable in terms of metallicity, while bulges appear to be systematically more metal-rich than disks for low-mass S0s. The ages of bulges and disks in high-mass S0s appear to increase with local density. The bulge ages of low-mass S0s also increase with local density, but such a trend is not clear in the disk ages of low-mass S0s. In addition, the age difference between bulge and disk components (ΔAge) tends to increase with local density, for both high-mass and low-mass S0s. High-mass S0s have systematically greater ΔAge than low-mass S0s at a given local density. Our results indicate that the stellar mass significantly influences the evolution of S0 galaxies, but the environment also plays an important role in determining the evolution of bulges and disks at a given stellar mass.

The Origin of Radio Emission in Black Hole X-ray Binaries

We studied the relation of accretion-jet power and disk luminosity, especially the jet efficiencies and disk radiative efficiencies for different accretion disks as well as black hole (BH) spin, in order to explore the origin of radio emission in black hole X-ray binaries (BHXBs). We found that jet efficiency increases more rapidly (efficient) than the nearly constant disk radiative efficiency for thin disk component in high accretion regime, which could account for the steep track (μ&gt;1) in the observed radio and X-ray luminosity relations (LR∝LXμ), but the thin disk component may not be able to explain the standard track (μ≈0.6) in the BHXBs. For hot accretion flows (HAF), the resulting jet efficiency changes along with the large range of accretions from quiescent state to nearly Eddington state, which could account for the standard track in the BHXBs. The BH spin-jet is discussed for the magnetic arrested disk (MAD) state; in this state, the spin-jet power might contribute to a linear correlation between jet power and mass accretion rate for a given source. More accurate observations are required to test the results.

A Comprehensive X-Ray Report on AT2019wey

Abstract Here, we present MAXI, Swift, NICER, NuSTAR, and Chandra observations of the X-ray transient AT2019wey (SRGA J043520.9+552226, SRGE J043523.3+552234). From spectral and timing analyses we classify it as a Galactic low-mass X-ray binary (LMXB) with a black hole (BH) or neutron star (NS) accretor. AT2019wey stayed in the low/hard state (LHS) from 2019 December to 2020 August 21, and the hard-intermediate state (HIMS) from 2020 August 21 to 2020 November. For the first six months of the LHS, AT2019wey had a flux of ∼1 mCrab, and displayed a power-law X-ray spectrum with photon index Γ = 1.8. From 2020 June to August, it brightened to ∼20 mCrab. Spectral features characteristic of relativistic reflection became prominent. On 2020 August 21, the source left the “hard line” on the rms–intensity diagram, and transitioned from LHS to HIMS. The thermal disk component became comparable to the power-law component. A low-frequency quasi-periodic oscillation (QPO) was observed. The QPO central frequency increased as the spectrum softened. No evidence of pulsation was detected. We are not able to decisively determine the nature of the accretor (BH or NS). However, the BH option is favored by the position of this source on the Γ–L X, L radio–L X, and L opt–L X diagrams. We find the BH candidate XTE J1752−223 to be an analog of AT2019wey. Both systems display outbursts with long plateau phases in the hard states. We conclude by noting the potential of SRG in finding new members of this emerging class of low luminosity and long-duration LMXB outbursts.

The Pristine survey XIII: uncovering the very metal-poor tail of the thin disc

ABSTRACT We evaluate the rotational velocity of stars observed by the Pristine survey towards the Galactic anticentre spanning a wide range of metallicities from the extremely metal-poor regime ([Fe/H] &amp;lt; −3) to nearly solar metallicity. In the Galactic anticentre direction, the rotational velocity (Vϕ) is similar to the tangential velocity in the galactic longitude direction (Vℓ). This allows us to estimate Vϕ from Gaia early data release 3 (Gaia EDR3) proper motions for stars without radial velocity measurements. This substantially increases the sample of stars in the outer disc with estimated rotational velocities. Our stellar sample towards the anticentre is dominated by a kinematical thin disc with a mean rotation of ∼−220 km s−1. However, our analysis reveals the presence of more stellar substructures. The most intriguing is a well-populated extension of the kinematical thin disc down to [Fe/H] ∼ −2 . A scarcer fast-rotating population reaching the extremely metal-poor regime down to [Fe/H] ∼ −3.5 is also detected but without statistical significance to unambiguously state whether this is the extremely metal-poor extension of the thin disc or the high-rotating tail of hotter structures (like the thick disc or the halo). In addition, a more slowly rotating kinematical thick disc component is also required to explain the observed Vℓ distribution at [Fe/H] &amp;gt; −1.5 . Furthermore, we detect signatures of a ‘heated disc’, the so-called Splash, at metallicities higher than ∼−1.5. Finally, at [Fe/H] &amp;lt; −1.5 our anticentre sample is dominated by a kinematical halo with a net prograde motion.

Comparison of the Orbital Properties of the Milky Way Globular Clusters from the Data of the Gaia DR2 and EDR3 Catalogs

We provide new values of the orbital parameters of 152 globular clusters, which are calculated using the new mean proper motions obtained from the Gaia EDR3 catalog data. The orbits were integrated 5 Gyr back in an axisymmetric three-component potential with a spherical bulge, disk component, and spherical dark halo in the Navarro-Frenk-White form, which we refined using the rotation curve of objects with large galactocentric distances up to 200 kpc. The obtained orbital parameters were compared with the orbital parameters of the same globular clusters calculated earlier in the same gravitational potential using proper motions from the Gaia DR2 catalog data. The objects whose orbits underwent significant changes were identified.

Exploring the 100 au Scale Structure of the Protobinary System NGC 2264 CMM3 with ALMA

Abstract We have observed the young protostellar system NGC 2264 CMM3 in the 1.3 mm and 2.0 mm bands at a resolution of about 0.″1 (70 au) with ALMA. The structures of two distinct components, CMM3A and CMM3B, are resolved in the continuum images of both bands. CMM3A has an elliptical structure extending along the direction almost perpendicular to the known outflow, while CMM3B reveals a round shape. We have fitted two 2D Gaussian components to the elliptical structure of CMM3A and CMM3B and have separated the disk and envelope components for each source. The spectral index α between 2.0 and 0.8 mm is derived to be 2.4–2.7 and 2.4–2.6 for CMM3A and CMM3B, respectively, indicating optically thick dust emission and/or grain growth. A velocity gradient in the disk/envelope direction is detected for CMM3A in the CH3CN, CH3OH, and 13CH3OH lines detected in the 1.3 mm band, which can be interpreted as the rotation of the disk/envelope system. From this result, the protostellar mass of CMM3A is roughly evaluated to be 0.1–0.5 M ⊙ by assuming Keplerian rotation. The mass accretion rate is thus estimated to be 5 × 10−5 − 4 × 10−3 M ⊙ yr−1, which is higher than the typical mass accretion rate of low-mass protostars. The OCS emission line shows a velocity gradient in both outflow direction and disk/envelope direction. A hint of outflow rotation is found, and the specific angular momentum of the outflow is estimated to be comparable to that of the disk. These results provide us with novel information on the initial stage of a binary/multiple system.

Axial and para‑axial loading response evaluation on human cadaver‑harvested lumbar vertebral blocks: In vitro experiment with possible clinical implications for clinical practice

The aim of the present study conducted on the lumbar spine was to confirm that the pronounced decrease in resistance in the system is a phenomenon that can be eminently affected by the adaptive changes that occur at the level of the intervertebral disc at axial mechanical stresses. The biomechanical trial was carried out on 11 lumbar segments L1-L5, gathered from adult human cadavers. The dissection considered the complete keeping of all bone, disc, articulated and ligamentous components in their anatomical position. All 11 samples were frozen 24 h prior to the performance of the biomechanical measurement. The specimens were placed in the testing device, their placement being conditioned by the estimated dimensional values. Thus, to calculate the load and axial resistance, the models were placed vertically, central between the test machine ferries. The testing was carried out by applying variable forces and displacement supervision. The displacement interval was represented by a segment of 0-10 mm with surveillance every 2 mm. Mobility in the sagittal plane (flexion earlier in our case) was much higher than that in the frontal plane, obviously limiting mobility via the intervertebral disc and articular complex through the presence of arches. Statistical analysis demonstrated the lack of any correlation values between the two types of movements (R2=0.005507), underlining the absence of any prediction elements. A noteworthy aspect is that the correlations appeared low, statistically insignificant, even within the same movement in the sagittal plane between the two levels, L1-L3 and L3-L5 (R2=0.610427), which may lead to the possibility of the emergence of significant differences in mobility between respective levels. The behavior type of the monitored specimens and the results obtained allowed the mapping of objective parallelism between the values obtained and the behavior in vivo of the lumbar vertebral segment.

Testing gravity with the Milky Way: Yukawa potential

We test a Yukawa correction to the Newtonian potential, making use of our own Galaxy - the Milky Way - as a testbed. We include as free parameter the Yukawa strength and range and the dark matter profile parameters, and compare several morphologies for the bulge, gas, and disk components, also using Bayesian model selection criteria. We employ up-to-date datasets for both the visible (baryonic) component of the Milky Way, and for the tracers of the gravitational potential (the Rotation Curve). We find that the data are consistent with the Newtonian potential, and constrain the Yukawa coupling $\beta$ to be negative and $\lambda$ to range along the curve $\lambda = a|\beta|^{c}$ with $a = (0.77 \pm 0.06)$ kpc and $c = -0.503\substack{+0.016 \\ -0.019}$.

The Galaxy Activity, Torus, and Outflow Survey (GATOS)

We compare high angular resolution mid-infrared (mid-IR) and Atacama Large Millimeter/submillimeter Array (ALMA) far-infrared (far-IR) images of twelve nearby (median 21 Mpc) Seyfert galaxies selected from the Galaxy Activity, Torus, and Outflow Survey (GATOS). The mid-IR unresolved emission contributes more than 60% of the nuclear (diameters of 1.5″ ∼ 150 pc) emission in most galaxies. By contrast, the ALMA 870 μm continuum emission is mostlyresolved with a median diameter of 42 pc and typically along the equatorial direction of the torus (Paper I). The Eddington ratios and nuclear hydrogen column densities (NH) of half the sample are favorable to launching polar and/or equatorial dusty winds, according to numerical simulations. Six of these show mid-IR extended emission approximately in the polar direction as traced by the narrow line region and perpendicular to the ALMA emission. In a few galaxies, the nuclear NH might be too high to uplift large quantities of dusty material along the polar direction. Five galaxies have low NH and/or Eddington ratios and thus polar dusty winds are not likely. We generated new radiative transfer CAT3D-WIND disk+wind models and model images at 8, 12, and 700 μm. We tailored these models to the properties of the GATOS Seyferts in this work. At low wind-to-disk cloud ratios, the far-IR model images have disk- and ring-like morphologies. The characteristic “X”-shape associated with dusty winds is seen better in the far-IR at intermediate-high inclinations for the extended-wind configurations. In most of the explored models, the mid-IR emission mainly comes from the inner part of the disk and cone. Extended biconical and one-sided polar mid-IR emission is seen in extended-wind configurations and high wind-to-disk cloud ratios. When convolved to the typical angular resolution of our observations, the CAT3D-WIND model images reproduce qualitative aspects of the observed mid- and far-IR morphologies. However, low to intermediate values of the wind-to-disk ratio are required to account for the observed large fractions of unresolved mid-IR emission in our sample. This work and Paper I provide observational support for the torus+wind scenario. The wind component is more relevant at high Eddington ratios and/or active galactic nucleus luminosities, and polar dust emission is predicted at nuclear column densities of up to ∼1024 cm−2. The torus or disk component, on the other hand, prevails at low luminosities and/or Eddington ratios.

Witnessing history: sky distribution, detectability, and rates of naked-eye Milky Way supernovae

ABSTRACT The Milky Way hosts on average a few supernova explosions per century, yet in the past millennium only five supernovae have been identified confidently in the historical record. This deficit of naked-eye supernovae is at least partly due to dust extinction in the Galactic plane. We explore this effect quantitatively, developing a formalism for the supernova probability distribution in space and on the sky, accounting for dust and for the observer’s flux limit. We then construct a fiducial axisymmetric model for the spatial supernova and dust densities, featuring an exponential dependence on galactocentric radius and height, with core-collapse events in a thin disc and Type Ia events including a thick disc component. When no flux limit is applied, our model predicts that on the sky, supernovae are intrinsically concentrated in the Galactic plane, with Type Ia events extending to higher latitudes. We then apply a flux limit and include dust effects, to predict the sky distribution of historical supernovae. We use well-observed supernovae as light-curve templates, and introduce naked-eye discovery criteria. The resulting sky distributions are strikingly inconsistent with the locations of confident historical supernovae, none of which lie near our model’s central peaks. Indeed, SN 1054 lies off the plane almost exactly in the anticentre, and SN 1181 is in the second Galactic quadrant. We discuss possible explanations for these discrepancies. We calculate the percentage of all supernovae bright enough for historical discovery: $\simeq 13{{\ \rm per\ cent}}$ of core-collapse and $\simeq 33{{\ \rm per\ cent}}$ of Type Ia events. Using these and the confident historical supernovae, we estimate the intrinsic Galactic supernova rates, finding general agreement with other methods. Finally, we urge searches for supernovae in historical records from civilizations in the Southern hemisphere.