We perform a comprehensive study of Milky Way (MW) satellite galaxies to constrain the fundamental properties of dark matter (DM). This analysis fully incorporates inhomogeneities in the spatial ...distribution and detectability of MW satellites and marginalizes over uncertainties in the mapping between galaxies and DM halos, the properties of the MW system, and the disruption of subhalos by the MW disk. Our results are consistent with the cold, collisionless DM paradigm and yield the strongest cosmological constraints to date on particle models of warm, interacting, and fuzzy dark matter. At 95% confidence, we report limits on (i) the mass of thermal relic warm DM, m_{WDM}>6.5 keV (free-streaming length, λ_{fs}≲10h^{-1} kpc), (ii) the velocity-independent DM-proton scattering cross section, σ_{0}<8.8×10^{-29} cm^{2} for a 100 MeV DM particle mass DM-proton coupling, c_{p}≲(0.3 GeV)^{-2}, and (iii) the mass of fuzzy DM, m_{ϕ}>2.9×10^{-21} eV (de Broglie wavelength, λ_{dB}≲0.5 kpc). These constraints are complementary to other observational and laboratory constraints on DM properties.
Numerous articles have recently reported on gas seepage offshore Svalbard, because the gas emission from these Arctic sediments was thought to result from gas hydrate dissociation, possibly triggered ...by anthropogenic ocean warming. We report on findings of a much broader seepage area, extending from 74° to 79°, where more than a thousand gas discharge sites were imaged as acoustic flares. The gas discharge occurs in water depths at and shallower than the upper edge of the gas hydrate stability zone and generates a dissolved methane plume that is hundreds of kilometer in length. Data collected in the summer of 2015 revealed that 0.02-7.7% of the dissolved methane was aerobically oxidized by microbes and a minor fraction (0.07%) was transferred to the atmosphere during periods of low wind speeds. Most flares were detected in the vicinity of the Hornsund Fracture Zone, leading us to postulate that the gas ascends along this fracture zone. The methane discharges on bathymetric highs characterized by sonic hard grounds, whereas glaciomarine and Holocene sediments in the troughs apparently limit seepage. The large scale seepage reported here is not caused by anthropogenic warming.
We report the results of a systematic search for ultra-faint Milky Way satellite galaxies using data from the Dark Energy Survey (DES) and Pan-STARRS1 (PS1). Together, DES and PS1 provide multi-band ...photometry in optical/near-infrared wavelengths over ∼80% of the sky. Our search for satellite galaxies targets ∼25,000 deg2 of the high-Galactic-latitude sky reaching a 10 point-source depth of 22.5 mag in the g and r bands. While satellite galaxy searches have been performed independently on DES and PS1 before, this is the first time that a self-consistent search is performed across both data sets. We do not detect any new high-significance satellite galaxy candidates, recovering the majority of satellites previously detected in surveys of comparable depth. We characterize the sensitivity of our search using a large set of simulated satellites injected into the survey data. We use these simulations to derive both analytic and machine-learning models that accurately predict the detectability of Milky Way satellites as a function of their distance, size, luminosity, and location on the sky. To demonstrate the utility of this observational selection function, we calculate the luminosity function of Milky Way satellite galaxies, assuming that the known population of satellite galaxies is representative of the underlying distribution. We provide access to our observational selection function to facilitate comparisons with cosmological models of galaxy formation and evolution.
The population of Milky Way (MW) satellites contains the faintest known galaxies and thus provides essential insight into galaxy formation and dark matter microphysics. Here we combine a model of the ...galaxy-halo connection with newly derived observational selection functions based on searches for satellites in photometric surveys over nearly the entire high Galactic latitude sky. In particular, we use cosmological zoom-in simulations of MW-like halos that include realistic Large Magellanic Cloud (LMC) analogs to fit the position-dependent MW satellite luminosity function. We report decisive evidence for the statistical impact of the LMC on the MW satellite population due to an estimated 6 2 observed LMC-associated satellites, consistent with the number of LMC satellites inferred from Gaia proper-motion measurements, confirming the predictions of cold dark matter models for the existence of satellites within satellite halos. Moreover, we infer that the LMC fell into the MW within the last 2 Gyr at high confidence. Based on our detailed full-sky modeling, we find that the faintest observed satellites inhabit halos with peak virial masses below at 95% confidence, and we place the first robust constraints on the fraction of halos that host galaxies in this regime. We predict that the faintest detectable satellites occupy halos with peak virial masses above , highlighting the potential for powerful galaxy formation and dark matter constraints from future dwarf galaxy searches.
Arctic amplification of global warming has led to increased summer sea ice retreat, which influences gas exchange between the Arctic Ocean and the atmosphere where sea ice previously acted as a ...physical barrier. Indeed, recently observed enhanced atmospheric methane concentrations in Arctic regions with fractional sea-ice cover point to unexpected feedbacks in cycling of methane. We report on methane excess in sea ice-influenced water masses in the interior Arctic Ocean and provide evidence that sea ice is a potential source. We show that methane release from sea ice into the ocean occurs via brine drainage during freezing and melting i.e. in winter and spring. In summer under a fractional sea ice cover, reduced turbulence restricts gas transfer, then seawater acts as buffer in which methane remains entrained. However, in autumn and winter surface convection initiates pronounced efflux of methane from the ice covered ocean to the atmosphere. Our results demonstrate that sea ice-sourced methane cycles seasonally between sea ice, sea-ice-influenced seawater and the atmosphere, while the deeper ocean remains decoupled. Freshening due to summer sea ice retreat will enhance this decoupling, which restricts the capacity of the deeper Arctic Ocean to act as a sink for this greenhouse gas.
Phosphine is a small redox-active gas that is used to protect global grain reserves, which are threatened by the emergence of phosphine resistance in pest insects. We find that polymorphisms ...responsible for genetic resistance cluster around the redox-active catalytic disulfide or the dimerization interface of dihydrolipöamide dehydrogenase (DLD) in insects (Rhyzopertha dominica and Tribolium castaneum) and nematodes (Caenorhabditis elegans). DLD is a core metabolic enzyme representing a new class of resistance factor for a redox-active metabolic toxin. It participates in four key steps of core metabolism, and metabolite profiles indicate that phosphine exposure in mutant and wild-type animals affects these steps differently. Mutation of DLD in C elegans increases arsenite sensitivity. This specific vulnerability may be exploited to control phosphine-resistant insects and safeguard food security.
The bacterially mediated aerobic methane oxidation (MOx) is a key mechanism in controlling methane (CH4) emissions from the world's oceans to the atmosphere. In this study, we investigated MOx in the ...Arctic fjord Storfjorden (Svalbard) by applying a combination of radio-tracer-based incubation assays (3H-CH4 and 14C-CH4), stable C-CH4 isotope measurements, and molecular tools (16S rRNA gene Denaturing Gradient Gel Electrophoresis (DGGE) fingerprinting, pmoA- and mxaF gene analyses). Storfjorden is stratified in the summertime with melt water (MW) in the upper 60 m of the water column, Arctic water (ArW) between 60 and 100 m, and brine-enriched shelf water (BSW) down to 140 m. CH4 concentrations were supersaturated with respect to the atmospheric equilibrium (about 3–4 nM) throughout the water column, increasing from ∼20 nM at the surface to a maximum of 72 nM at 60 m and decreasing below. MOx rate measurements at near in situ CH4 concentrations (here measured with 3H-CH4 raising the ambient CH4 pool by <2 nM) showed a similar trend: low rates at the sea surface, increasing to a maximum of ∼2.3 nM day−1 at 60 m, followed by a decrease in the deeper ArW/BSW. In contrast, rate measurements with 14C-CH4 (incubations were spiked with ∼450 nM of 14C-CH4, providing an estimate of the CH4 oxidation at elevated concentration) showed comparably low turnover rates (<1 nM day−1) at 60 m, and peak rates were found in ArW/BSW at ∼100 m water depth, concomitant with increasing 13C values in the residual CH4 pool. Our results indicate that the MOx community in the surface MW is adapted to relatively low CH4 concentrations. In contrast, the activity of the deep-water MOx community is relatively low at the ambient, summertime CH4 concentrations but has the potential to increase rapidly in response to CH4 availability. A similar distinction between surface and deep-water MOx is also suggested by our molecular analyses. The DGGE banding patterns of 16S rRNA gene fragments of the surface MW and deep water were clearly different. A DGGE band related to the known type I MOx bacterium Methylosphaera was observed in deep BWS, but absent in surface MW. Furthermore, the Polymerase Chain Reaction (PCR) amplicons of the deep water with the two functional primers sets pmoA and mxaF showed, in contrast to those of the surface MW, additional products besides the expected one of 530 base pairs (bp). Apparently, different MOx communities have developed in the stratified water masses in Storfjorden, which is possibly related to the spatiotemporal variability in CH4 supply to the distinct water masses.
Abstract
The DECam Local Volume Exploration survey (DELVE) is a 126-night survey program on the 4 m Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile. DELVE seeks to understand ...the characteristics of faint satellite galaxies and other resolved stellar substructures over a range of environments in the Local Volume. DELVE will combine new DECam observations with archival DECam data to cover ∼15,000 deg
2
of high Galactic latitude (∣
b
∣ > 10°) southern sky to a 5
σ
depth of
g
,
r
,
i
,
z
∼ 23.5 mag. In addition, DELVE will cover a region of ∼2200 deg
2
around the Magellanic Clouds to a depth of
g
,
r
,
i
∼ 24.5 mag and an area of ∼135 deg
2
around four Magellanic analogs to a depth of
g
,
i
∼ 25.5 mag. Here, we present an overview of the DELVE program and progress to date. We also summarize the first DELVE public data release (DELVE DR1), which provides point-source and automatic aperture photometry for ∼520 million astronomical sources covering ∼5000 deg
2
of the southern sky to a 5
σ
point-source depth of
g
= 24.3 mag,
r
= 23.9 mag,
i
= 23.3 mag, and
z
= 22.8 mag. DELVE DR1 is publicly available via the NOIRLab Astro Data Lab science platform.
We present the discovery of a faint, resolved stellar system, BLISS J0321+0438 (BLISS 1), found in Dark Energy Camera data from the first observing run of the Blanco Imaging of the Southern Sky ...(BLISS) survey. BLISS J0321+0438 (BLISS 1) is located at with a heliocentric distance of . It is a faint, , and compact, , system consistent with previously discovered faint halo star clusters. Using data from the second data release of the Gaia satellite, we measure a proper motion of mas yr−1. Combining the available positional and velocity information with simulations of the accreted satellite population of the Large Magellanic Cloud (LMC), we find that it is unlikely that BLISS J0321+0438 (BLISS 1) originated with the LMC.
Abstract
We present the discovery of DELVE 6, an ultra-faint stellar system identified in the second data release of the DECam Local Volume Exploration (DELVE) survey. Based on a maximum-likelihood ...fit to its structure and stellar population, we find that DELVE 6 is an old (
τ
> 9.8 Gyr at 95% confidence) and metal-poor (Fe/H < −1.17 dex at 95% confidence) stellar system with an absolute magnitude of
M
V
=
−
1.5
−
0.6
+
0.4
mag and an azimuthally averaged half-light radius of
r
1
/
2
=
10
−
3
+
4
pc. These properties are consistent with the population of ultra-faint star clusters uncovered by recent surveys. Interestingly, DELVE 6 is located at an angular separation of ∼10° from the center of the Small Magellanic Cloud (SMC), corresponding to a 3D physical separation of ∼20 kpc given the system’s observed distance (
D
⊙
= 80 kpc). This also places the system ∼35 kpc from the center of the Large Magellanic Cloud (LMC), lying within recent constraints on the size of the LMC’s dark matter halo. We tentatively measure the proper motion of DELVE 6 using data from Gaia, which we find supports a potential association between the system and the LMC/SMC. Although future kinematic measurements will be necessary to determine its origins, we highlight that DELVE 6 may represent only the second or third ancient (
τ
> 9 Gyr) star cluster associated with the SMC, or one of fewer than two dozen ancient clusters associated with the LMC. Nonetheless, we cannot currently rule out the possibility that the system is a distant Milky Way halo star cluster.
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