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"Nelson, Erica"
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Marvel universe. Time and again
\"What mysteries await buried deep within the multitude of the Marvel Universe? During an advance scouting mission in World War II, Captain America and Bucky come across an old farmhouse where a group of concentration camp escapees are fending off recapture. Years ago, Spider-Man came back from an alien world with a fantastic new costume - a living alien symbiote looking to bond with him permanently! Anxious to find a world worthy enough to sate the mighty hunger of GALACTUS, Norrin Radd's early explorations as the Devourer's new Herald bear no fruit. When a Secret Invasion of Skrulls turns Manhattan upside down, Miles Morales must choose: do his great powers come with great responsibility? When Detective Misty Knight places the newest super-suit on the block, Daredevil, at the scene of a crime, sparks will fly - and not the good kind. What secrets has Kitty Pryde been keeping from her summer at Camp Maplebrook? And as World War II draws to a close, Sergeant Fury and his Howling Commandos face a mission unlike any other they've ever tackled!\"--Provided by publisher.
Book
Flying into the hurricane: A case study of UAV use in damage assessment during the 2017 hurricanes in Texas and Florida
Unmanned aerial vehicles (UAVs) or drones have been used by disaster relief organizations in the United States since 2005. However, their place in the disaster response ecosystem-the standardization, utility, ethical, and legal challenges of drone use-remains largely unstudied. This case series describes how UAVs were used by two teams of responders for damage assessment purposes during the 2017 southeastern US Hurricanes Harvey and Irma. Data streams ranged from social media, direct observation, participant-observation and semi-directed interviews. Qualitative analysis was performed for thematic content derived from field observation and from post-hoc interviews. Outcomes of the qualitative analysis emphasize the barriers to deploying drones in the disaster context, their tactical implementation, programmatic integration, and ethical and legal challenges. These observations lay the groundwork for both future research on the utilization of drones and the prudent and ethical implementation of programs that employ drones in post-disaster settings.
Journal Article
A small and vigorous black hole in the early Universe
Several theories have been proposed to describe the formation of black hole seeds in the early Universe and to explain the emergence of very massive black holes observed in the first thousand million years after the Big Bang
1
–
3
. Models consider different seeding and accretion scenarios
4
–
7
, which require the detection and characterization of black holes in the first few hundred million years after the Big Bang to be validated. Here we present an extensive analysis of the JWST-NIRSpec spectrum of GN-z11, an exceptionally luminous galaxy at
z
= 10.6, revealing the detection of the [Ne
iv
]
λ
2423 and CII*
λ
1335 transitions (typical of active galactic nuclei), as well as semi-forbidden nebular lines tracing gas densities higher than 10
9
cm
−3
, typical of the broad line region of active galactic nuclei. These spectral features indicate that GN-z11 hosts an accreting black hole. The spectrum also reveals a deep and blueshifted CIV
λ
1549 absorption trough, tracing an outflow with velocity 800−1,000 km s
−1
, probably driven by the active galactic nucleus. Assuming local virial relations, we derive a black hole mass of
log
(
M
BH
/
M
⊙
)
=
6.2
±
0.3
, accreting at about five times the Eddington rate. These properties are consistent with both heavy seeds scenarios and scenarios considering intermediate and light seeds experiencing episodic super-Eddington phases. Our finding explains the high luminosity of GN-z11 and can also provide an explanation for its exceptionally high nitrogen abundance.
An extensive analysis of the JWST-NIRSpec spectrum of GN-z11 shows a supermassive black hole of a few million solar masses in a galaxy 440 million years after the Big Bang.
Journal Article
Star formation shut down by multiphase gas outflow in a galaxy at a redshift of 2.45
Large-scale outflows driven by supermassive black holes are thought to have a fundamental role in suppressing star formation in massive galaxies. However, direct observational evidence for this hypothesis is still lacking, particularly in the young universe where star-formation quenching is remarkably rapid
1
–
3
, thus requiring effective removal of gas
4
as opposed to slow gas heating
5
,
6
. Although outflows of ionized gas are frequently detected in massive distant galaxies
7
, the amount of ejected mass is too small to be able to suppress star formation
8
,
9
. Gas ejection is expected to be more efficient in the neutral and molecular phases
10
, but at high redshift these have only been observed in starbursts and quasars
11
,
12
. Here we report JWST spectroscopy of a massive galaxy experiencing rapid quenching at a redshift of 2.445. We detect a weak outflow of ionized gas and a powerful outflow of neutral gas, with a mass outflow rate that is sufficient to quench the star formation. Neither X-ray nor radio activity is detected; however, the presence of a supermassive black hole is suggested by the properties of the ionized gas emission lines. We thus conclude that supermassive black holes are able to rapidly suppress star formation in massive galaxies by efficiently ejecting neutral gas.
JWST observations of a massive galaxy at a redshift of 2.45 show a powerful outflow of neutral gas, with a mass outflow rate that is sufficient to shut down star formation.
Journal Article
A population of red candidate massive galaxies ~600 Myr after the Big Bang
Galaxies with stellar masses as high as roughly 10
11
solar masses have been identified
1
–
3
out to redshifts
z
of roughly 6, around 1 billion years after the Big Bang. It has been difficult to find massive galaxies at even earlier times, as the Balmer break region, which is needed for accurate mass estimates, is redshifted to wavelengths beyond 2.5 μm. Here we make use of the 1–5 μm coverage of the James Webb Space Telescope early release observations to search for intrinsically red galaxies in the first roughly 750 million years of cosmic history. In the survey area, we find six candidate massive galaxies (stellar mass more than 10
10
solar masses) at 7.4 ≤
z
≤ 9.1, 500–700 Myr after the Big Bang, including one galaxy with a possible stellar mass of roughly 10
11
solar masses. If verified with spectroscopy, the stellar mass density in massive galaxies would be much higher than anticipated from previous studies on the basis of rest-frame ultraviolet-selected samples.
James Webb Space Telescope early release observations used to search for intrinsically red galaxies from the first 750 million years of cosmic history find six candidate massive galaxies, possibly including one of roughly 10
11
solar masses.
Journal Article
Modeling pastoralist movement in response to environmental variables and conflict in Somaliland: Combining agent-based modeling and geospatial data
Pastoralism is widely practiced in arid lands and is the primary means of livelihood for approximately 268 million people across Africa. Environmental, interpersonal, and transactional variables such as vegetation and water availability, conflict, ethnic tensions, and private/public land delineation influence the movements of these populations. The challenges of climate change and conflict are widely felt by nomadic pastoralists in Somalia, where resources are scarce, natural disasters are increasingly common, and protracted conflict has plagued communities for decades. Bereft of real-time data, researchers and programmatic personnel often turn to post hoc analysis to understand the interaction between climate, conflict, and migration, and design programs to address the needs of nomadic pastoralists. By designing an Agent-Based Model to simulate the movement of nomadic pastoralists based on typologically-diverse, historical data of environmental, interpersonal, and transactional variables in Somaliland and Puntland between 2008 and 2018, this study explores how pastoralists respond to changing environments. Through subsequent application of spatial analysis such as choropleth maps, kernel density mapping, and standard deviational ellipses, we characterize the resultant pastoralist population distribution in response to these variables. Outcomes demonstrate a large scale spatio-temporal trend of pastoralists migrating to the southeast of the study area with high density areas in the south of Nugaal, the northwest of Sool, and along the Ethiopian border. While minimal inter-seasonal variability is seen, multiple analyses support the consolidation of pastoralists to specifically favorable regions. Exploration of the large-scale population, climate, and conflict trends allows for cogent narratives and associative hypotheses regarding the pastoralist migration during the study period. While this model produces compelling associations between pastoralist movements and terrestrial and conflict variables, it relies heavily on assumptions and incomplete data that are not necessarily representative of realities on the ground. Given the paucity of data regarding pastoralist decision-making and migration, validation remains challenging.
Journal Article
Quenching of star formation from a lack of inflowing gas to galaxies
Star formation in half of massive galaxies was quenched by the time the Universe was 3 billion years old
1
. Very low amounts of molecular gas seem to be responsible for this, at least in some cases
2
–
7
, although morphological gas stabilization, shock heating or activity associated with accretion onto a central supermassive black hole are invoked in other cases
8
–
11
. Recent studies of quenching by gas depletion have been based on upper limits that are insufficiently sensitive to determine this robustly
2
–
7
, or stacked emission with its problems of averaging
8
,
9
. Here we report 1.3 mm observations of dust emission from 6 strongly lensed galaxies where star formation has been quenched, with magnifications of up to a factor of 30. Four of the six galaxies are undetected in dust emission, with an estimated upper limit on the dust mass of 0.0001 times the stellar mass, and by proxy (assuming a Milky Way molecular gas-to-dust ratio) 0.01 times the stellar mass in molecular gas. This is two orders of magnitude less molecular gas per unit stellar mass than seen in star forming galaxies at similar redshifts
12
–
14
. It remains difficult to extrapolate from these small samples, but these observations establish that gas depletion is responsible for a cessation of star formation in some fraction of high-redshift galaxies.
The authors report 1.3 mm observations of dust emission from strongly lensed galaxies where star formation is quenched, demonstrating that gas depletion is responsible for the cessation of star formation in some high-redshift galaxies.
Journal Article
Most of the photons that reionized the Universe came from dwarf galaxies
The identification of sources driving cosmic reionization, a major phase transition from neutral hydrogen to ionized plasma around 600–800 Myr after the Big Bang
1
–
3
, has been a matter of debate
4
. Some models suggest that high ionizing emissivity and escape fractions (
f
esc
) from quasars support their role in driving cosmic reionization
5
,
6
. Others propose that the high
f
esc
values from bright galaxies generate sufficient ionizing radiation to drive this process
7
. Finally, a few studies suggest that the number density of faint galaxies, when combined with a stellar-mass-dependent model of ionizing efficiency and
f
esc
, can effectively dominate cosmic reionization
8
,
9
. However, so far, comprehensive spectroscopic studies of low-mass galaxies have not been done because of their extreme faintness. Here we report an analysis of eight ultra-faint galaxies (in a very small field) during the epoch of reionization with absolute magnitudes between
M
UV
≈ −17 mag and −15 mag (down to 0.005
L
⋆
(refs.
10
,
11
)). We find that faint galaxies during the first thousand million years of the Universe produce ionizing photons with log[
ξ
ion
(Hz erg
−1
)] = 25.80 ± 0.14, a factor of 4 higher than commonly assumed values
12
. If this field is representative of the large-scale distribution of faint galaxies, the rate of ionizing photons exceeds that needed for reionization, even for escape fractions of the order of 5%.
An analysis of eight ultra-faint galaxies during the epoch of reionization with absolute magnitudes between −17 mag and −15 mag shows that most of the photons that reionized the Universe come from dwarf galaxies.
Journal Article
A recently quenched galaxy 700 million years after the Big Bang
Local and low-redshift (
z
< 3) galaxies are known to broadly follow a bimodal distribution: actively star-forming galaxies with relatively stable star-formation rates and passive systems. These two populations are connected by galaxies in relatively slow transition. By contrast, theory predicts that star formation was stochastic at early cosmic times and in low-mass systems
1
–
4
. These galaxies transitioned rapidly between starburst episodes and phases of suppressed star formation, potentially even causing temporary quiescence—so-called mini-quenching events
5
,
6
. However, the regime of star-formation burstiness is observationally highly unconstrained. Directly observing mini-quenched galaxies in the primordial Universe is therefore of utmost importance to constrain models of galaxy formation and transformation
7
,
8
. Early quenched galaxies have been identified out to redshift
z
< 5 (refs.
9
–
12
) and these are all found to be massive (
M
⋆
> 10
10
M
⊙
) and relatively old. Here we report a (mini-)quenched galaxy at
z
= 7.3, when the Universe was only 700 Myr old. The JWST/NIRSpec spectrum is very blue (
U
–
V
= 0.16 ± 0.03 mag) but exhibits a Balmer break and no nebular emission lines. The galaxy experienced a short starburst followed by rapid quenching; its stellar mass (4–6 × 10
8
M
⊙
) falls in a range that is sensitive to various feedback mechanisms, which can result in perhaps only temporary quenching.
Analysis of the JWST/NIRSpec spectrum of the recently observed Lyman-break galaxy JADES-GS+53.15508-27.80178 revealed a redshift of
z
= 7.3, a Balmer break and a complete absence of nebular emission lines, indicating that quenching occurred only 700 million years after the Big Bang.
Journal Article
A high black-hole-to-host mass ratio in a lensed AGN in the early Universe
Early JWST observations have uncovered a population of red sources that might represent a previously overlooked phase of supermassive black hole growth
1
–
3
. One of the most intriguing examples is an extremely red, point-like object that was found to be triply imaged by the strong lensing cluster Abell 2744 (ref.
4
). Here we present deep JWST/NIRSpec observations of this object, Abell2744-QSO1. The spectroscopy confirms that the three images are of the same object, and that it is a highly reddened (
A
V
≃ 3) broad emission line active galactic nucleus at a redshift of
z
spec
= 7.0451 ± 0.0005. From the width of Hβ (full width at half-maximum = 2,800 ± 250 km s
−1
), we derive a black hole mass of
M
BH
=
4
−
1
+
2
×
1
0
7
M
⊙
. We infer a very high ratio of black-hole-to-galaxy mass of at least 3%, an order of magnitude more than that seen in local galaxies
5
and possibly as high as 100%. The lack of strong metal lines in the spectrum together with the high bolometric luminosity (
L
bol
= (1.1 ± 0.3) × 10
45
erg s
−1
) indicate that we are seeing the black hole in a phase of rapid growth, accreting at 30% of the Eddington limit. The rapid growth and high black-hole-to-galaxy mass ratio of Abell2744-QSO1 suggest that it may represent the missing link between black hole seeds
6
and one of the first luminous quasars
7
.
JWST/NIRSpec observations of Abell2744-QSO1 show a high black-hole-to-host mass ratio in the early Universe, which indicates that we are seeing the black hole in a phase of rapid growth, accreting at 30% of the Eddington limit.
Journal Article