The 25 April 2015, Mw7.8 Gorkha, Nepal, earthquake ruptured a shallow section of the Indian‐Eurasian plate boundary by reverse faulting with NNE‐SSW compression, consistent with the direction of ...current Indian‐Eurasian continental collision. The Gorkha main shock and aftershocks were recorded by permanent global and regional arrays and by a temporary local broadband array near the China‐Nepal border deployed prior to the Gorkha main shock. We relocate 272 earthquakes with Mw>3.5 by applying a multiscale double‐difference earthquake relocation technique to arrival times of direct and depth phases recorded globally and locally. We determine a well‐constrained depth of 18.5 km for the main shock hypocenter which places it on the Main Himalayan Thrust (MHT). Many of the aftershocks at shallower depths illuminate faulting structure in the hanging wall with dip angles that are steeper than the MHT. This system of thrust faults of the Lesser Himalaya may accommodate most of the elastic strain of the Himalayan orogeny.
Key Points
We relocate the 2015 Gorkha earthquakes using teleseismic and regional waveforms
The main shock is located on the horizontal Main Himalaya Thrust (MHT) at a depth of 18.5 km
Aftershocks show faulting structure in the hanging wall above the MHT
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Abstract
Quasar feedback may regulate the growth of supermassive black holes, quench coeval star formation, and impact galaxy morphology and the circumgalactic medium. However, direct evidence for ...quasar feedback in action at the epoch of peak black hole accretion at
z
≈ 2 remains elusive. A good case in point is the
z
= 1.6 quasar WISEA J100211.29+013706.7 (XID 2028), where past analyses of the same ground-based data have come to different conclusions. Here, we revisit this object with the integral-field unit of the Near Infrared Spectrograph on board the JWST as part of Early Release Science program Q3D. The excellent angular resolution and sensitivity of the JWST data reveal new morphological and kinematic substructures in the outflowing gas plume. An analysis of the emission-line ratios indicates that photoionization by the central quasar dominates the ionization state of the gas with no obvious sign for a major contribution from hot young stars anywhere in the host galaxy. The rest-frame near-UV emission aligned along the wide-angle cone of outflowing gas is interpreted as a scattering cone. The outflow has cleared a channel in the dusty host galaxy, through which some of the quasar ionizing radiation is able to escape and heat the surrounding interstellar and circumgalactic media. Although the warm ionized outflow is not powerful enough to impact the host galaxy via mechanical feedback, radiative feedback by the active galactic nucleus, aided by the outflow, may help to explain the unusually small molecular gas mass fraction in the galaxy host.
Abstract Dual quasars—two active supermassive black holes at galactic scales—represent crucial objects for studying the impact of galaxy mergers and quasar activity on the star formation rate (SFR) ...within their host galaxies, particularly at cosmic noon when SFR peaks. We present JWST/MIRI mid-infrared integral field spectroscopy of J074922.96+225511.7, a dual quasar with a projected separation of 3.8 kpc at a redshift z = 2.17. We detect spatially extended Fe ii 5.34 μ m and polycyclic aromatic hydrocarbon (PAH) 3.3 μ m emissions from the star formation activity in its host galaxy. We derive the SFR of 10 3.0±0.2 M ⊙ yr −1 using PAH 3.3 μ m, which is 5 times higher than that derived from the knee of the infrared luminosity function for galaxies at z ∼ 2. While the SFR of J0749+2255 agrees with that of star-forming galaxies of comparable stellar mass at the same redshifts, its molecular gas content falls short of expectations based on the molecular Kennicutt–Schmidt law. This discrepancy may result from molecular gas depletion due to the longer elevated stage of star formation, even after the molecular gas reservoir is depleted. We do not observe any quasar-driven outflow that impacts PAH and Fe ii in the host galaxy based on the spatially resolved maps. From the expected flux in PAH-based star formation, the Fe ii line likely originates from the star-forming regions in the host galaxy. Our study highlights the extreme stardust nature of J0749+2255, indicating a potential connection between the dual quasar phase and intense star formation activities.
Abstract
Massive galaxies formed most actively at redshifts
z
= 1–3 during the period known as “cosmic noon.” Here we present an emission-line study of the extremely red quasar ...SDSSJ165202.64+172852.3’s host galaxy at
z
= 2.94, based on observations with the Near Infrared Spectrograph integral field unit on board JWST. We use standard emission-line diagnostic ratios to map the sources of gas ionization across the host and a swarm of companion galaxies. The quasar dominates the photoionization, but we also discover shock-excited regions orthogonal to the ionization cone and the quasar-driven outflow. These shocks could be merger-induced or—more likely, given the presence of a powerful galactic-scale quasar outflow—these are signatures of wide-angle outflows that can reach parts of the galaxy that are not directly illuminated by the quasar. Finally, the kinematically narrow emission associated with the host galaxy presents as a collection of 1 kpc–scale clumps forming stars at a rate of at least 200
M
⊙
yr
−1
. The interstellar medium within these clumps shows high electron densities, reaching up to 3000 cm
−3
, with metallicities ranging from half to a third solar with a positive metallicity gradient, and
V
-band extinctions up to 3 mag. The star formation conditions are far more extreme in these regions than in local star-forming galaxies but consistent with those of massive galaxies at cosmic noon. The JWST observations simultaneously reveal an archetypal rapidly forming massive galaxy undergoing a merger, a clumpy starburst, an episode of obscured near-Eddington quasar activity, and an extremely powerful quasar outflow.
Abstract
Quasar-driven galactic outflows are a major driver of the evolution of massive galaxies. We report observations of a powerful galactic-scale outflow in a
z
= 3 extremely red and ...intrinsically luminous (
L
bol
≃ 5 × 10
47
erg s
−1
) quasar SDSSJ1652 + 1728 with the Near-infrared Spectrograph on board JWST. We analyze the kinematics of rest-frame optical emission lines and identify the quasar-driven outflow extending out to ∼10 kpc from the quasar with a velocity offset of (
v
r
= ± 500 km s
−1
) and high velocity dispersion (FWHM = 700–2400 km s
−1
). Due to JWST’s unprecedented surface brightness sensitivity in the near-infrared, we unambiguously show that the powerful high velocity outflow in an extremely red quasar encompasses a large swath of the host galaxy’s interstellar medium. Using the kinematics and dynamics of optical emission lines, we estimate the mass outflow rate—in the warm ionized phase alone—to be at least 2300 ± 1400
M
⊙
yr
−1
. We measure a momentum flux ratio between the outflow and the quasar accretion disk of ∼1 on a kpc scale, indicating that the outflow was likely driven in a relatively high (>10
23
cm
−2
) column density environment through radiation pressure on dust grains. We find a coupling efficiency between the bolometric luminosity of the quasar and the outflow of 0.1%, matching the theoretical prediction of the minimum coupling efficiency necessary for negative quasar feedback. The outflow has sufficient energetics to drive the observed turbulence seen in shocked regions of the quasar host galaxy, which are likely directly responsible for prolonging the time that it takes for gas to cool efficiently.
Abstract
The O
iii
5007 Å emission line is the most common tracer of warm, ionized outflows in active galactic nuclei across cosmic time. JWST newly allows us to use mid-IR spectral features at both ...high spatial and spectral resolution to probe these same winds. Here we present a comparison of ground-based, seeing-limited O
iii
and space-based, diffraction-limited S
iv
10.51
μ
m maps of the powerful, kiloparsec-scale outflow in the Type 1 red quasar SDSS J110648.32+480712.3. The JWST data are from the Mid-InfraRed Instrument. There is a close match in resolution between the data sets (∼0.″6), in ionization potential of the O
+2
and S
+3
ions (35 eV) and in line sensitivity (1–2 × 10
−17
erg s
−1
cm
−2
arcsec
−2
). The O
iii
and S
iv
line shapes match in velocity and line width over much of the 20 kpc outflowing nebula, and S
iv
is the brightest line in the rest-frame 3.5–19.5
μ
m range, demonstrating its usefulness as a mid-IR probe of quasar outflows. O
iii
is nevertheless intrinsically brighter and provides better contrast with the point-source continuum, which is strong in the mid-IR. There is a strong anticorrelation of O
iii
/S
iv
with average velocity, which is consistent with a scenario of differential obscuration between the approaching (blueshifted) and receding (redshifted) sides of the flow. The dust in the wind may also obscure the central quasar, consistent with models that attribute red quasar extinction to dusty winds.
On February 6, 2023, two earthquakes with magnitudes of MW 7.8 and MW 7.5 struck southeastern Turkey, causing significant casualties and economic losses. These seismic events occurred along the East ...Anatolian Fault Zone, a convergent boundary between the Arabian Plate and the Anatolian Subplate. In this study, we analyze the MW 7.8 and MW 7.5 earthquakes by comparing their aftershock relocations, tomographic images, and stress field inversions. The earthquakes were localized in the upper crust and exhibited steep dip angles. Furthermore, the aftershocks occurred either close to the boundaries of low and high P-wave velocity anomaly zones or within the low P-wave velocity anomaly zones. The East Anatolia Fault, associated with the MW 7.8 earthquake, and the Sürgü Fault, related to the MW 7.5 earthquake, predominantly experienced shear stress. However, their western sections experienced a combination of strike-slip and tensile stresses in addition to shear stress. The ruptures of the MW 7.8 and MW 7.5 earthquakes appear to have bridged a seismic gap that had seen sparse seismicity over the past 200 years prior to the 2023 Turkey earthquake sequence.
We present the design, implementation, and on-ground performance measurements of the Ionospheric Connection Explorer EUV spectrometer,
ICON EUV
, a wide field (
17
∘
×
12
∘
) extreme ultraviolet ...(EUV) imaging spectrograph designed to observe the lower ionosphere at tangent altitudes between 100 and 500 km. The primary targets of the spectrometer, which has a spectral range of 54–88 nm, are the O
ii
emission lines at 61.6 nm and 83.4 nm. Its design, using a single optical element, permits a
0
.
∘
26
imaging resolution perpendicular to the spectral dispersion direction with a large (
12
∘
) acceptance parallel to the dispersion direction while providing a slit-width dominated spectral resolution of
R
∼
25
at 58.4 nm. Pre-flight calibration shows that the instrument has met all of the science performance requirements.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
On January 1, 2024 at 16:10:09 JST, an Mj 7.6 earthquake struck the Noto Peninsula in the southern part of the Sea of Japan. This location has been experiencing an earthquake swarm for more than ...three years. Here, we provide an overview of this earthquake, focusing on the slip distribution of the mainshock and its relationship with the preceding swarm. We also reexamined the source areas of other large earthquakes that occurred around the Sea of Japan in the past and compared them with the Matsushiro earthquake swarm in central Japan from 1964 to 1968. The difference between the Matsushiro earthquake swarm and the Noto earthquake swarm is the surrounding stress field. The Matsushiro earthquake swarm was a strike-slip stress field, so the cracks in the crust were oriented vertically. This allowed fluids seeped from the depths to rise and flow out to the surface. On the other hand, the Noto area was a reverse fault stress field. Therefore, the cracks in the earth's crust were oriented horizontally. Fluids flowing underground in deep areas could not rise and spread over a wide area in the horizontal plane. This may have caused a large amount of fluid to accumulate underground, triggering a large earthquake. Although our proposed mechanism does not take into account other complex geological conditions into consideration, it may provide a simple way to explain why the Noto swarm is followed by a large earthquake while other swarms are not.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
The seismogenic layer thickness correlates with surface heat flow beneath the Japanese islands. However, this correlation is shown at restricted area, where seismic activity is high. In order to ...overcome this spatial limitation, we used another approach to estimate the regional thermal structure in the crust beneath the Japanese islands with more uniform coverage. The bottom depths of the magnetized crust determined from the spectral analysis of residual magnetic anomalies is generally interpreted as the level of the Curie point isotherm. We applied this method to estimate the crustal thermal structure in square windows of 2.125°
×
2.125°. The obtained depths ranging from 11 to 30
km with average value of 18
km, correlate with the seismogenic layer thickness. It suggests that the Curie point depth is a useful indicator of the crustal thermal structure in these regions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
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