423 research outputs found
Exploring Halo Substructure with Giant Stars. XV. Discovery of a Connection between the Monoceros Ring and the Triangulum-Andromeda Overdensity?
Thanks to modern sky surveys, over twenty stellar streams and overdensity
structures have been discovered in the halo of the Milky Way. In this paper, we
present an analysis of spectroscopic observations of individual stars from one
such structure, "A13", first identified as an overdensity using the M giant
catalog from the Two Micron All-Sky Survey. Our spectroscopic observations show
that stars identified with A13 have a velocity dispersion of 40
, implying that it is a genuine coherent structure rather
than a chance super-position of random halo stars. From its position on the
sky, distance (15~kpc heliocentric), and kinematical properties, A13 is
likely to be an extension of another low Galactic latitude substructure -- the
Galactic Anticenter Stellar Structure (also known as the Monoceros Ring) --
towards smaller Galactic longitude and farther distance. Furthermore, the
kinematics of A13 also connect it with another structure in the southern
Galactic hemisphere -- the Triangulum-Andromeda overdensity. We discuss these
three connected structures within the context of a previously proposed scenario
that one or all of these features originate from the disk of the Milky Way.Comment: 12 pages, 9 figures. Accepted for publication in Ap
Editorial: Evolution and genomics of the Mycobacterium tuberculosis complex
Publication history: Accepted - 10 February 2023; Published - 3 March 2023.AG acknowledges funding from the São Paulo Research
Foundation (FAPESP, 2016/26108-0)
Antibodies to Enteroviruses in Cerebrospinal Fluid of Patients with Acute Flaccid Myelitis.
Acute flaccid myelitis (AFM) has caused motor paralysis in >560 children in the United States since 2014. The temporal association of enterovirus (EV) outbreaks with increases in AFM cases and reports of fever, respiratory, or gastrointestinal illness prior to AFM in >90% of cases suggest a role for infectious agents. Cerebrospinal fluid (CSF) from 14 AFM and 5 non-AFM patients with central nervous system (CNS) diseases in 2018 were investigated by viral-capture high-throughput sequencing (VirCapSeq-VERT system). These CSF and serum samples, as well as multiple controls, were tested for antibodies to human EVs using peptide microarrays. EV RNA was confirmed in CSF from only 1 adult AFM case and 1 non-AFM case. In contrast, antibodies to EV peptides were present in CSF of 11 of 14 AFM patients (79%), significantly higher than controls, including non-AFM patients (1/5 [20%]), children with Kawasaki disease (0/10), and adults with non-AFM CNS diseases (2/11 [18%]) (P = 0.023, 0.0001, and 0.0028, respectively). Six of 14 CSF samples (43%) and 8 of 11 sera (73%) from AFM patients were immunoreactive to an EV-D68-specific peptide, whereas the three control groups were not immunoreactive in either CSF (0/5, 0/10, and 0/11; P = 0.008, 0.0003, and 0.035, respectively) or sera (0/2, 0/8, and 0/5; P = 0.139, 0.002, and 0.009, respectively).IMPORTANCE The presence in cerebrospinal fluid of antibodies to EV peptides at higher levels than non-AFM controls supports the plausibility of a link between EV infection and AFM that warrants further investigation and has the potential to lead to strategies for diagnosis and prevention of disease
Stellar multiplicity: an interdisciplinary nexus
Our uncertainties about binary star systems (and triples and so on) limit our
capabilities in literally every single one of the Thematic Areas identified for
Astro2020. We need to understand the population statistics of stellar
multiplicity and their variations with stellar type, chemistry, and dynamical
environment: Correct interpretation of any exoplanet experiment depends on
proper treatment of resolved and unresolved binaries; stellar multiplicity is a
direct outcome of star and companion formation; the most precise constraints on
stellar structure come from well-characterized binary systems; stellar
populations heavily rely on stellar and binary evolution modeling;
high-redshift galaxy radiation and reionization is controlled by
binary-dependent stellar physics; compact objects are the outcomes of binary
evolution; the interpretation of multi-messenger astronomy from gravitational
waves, light, and neutrinos relies on understanding the products of binary star
evolution; near-Universe constraints on the Hubble constant with Type Ia
supernovae and gravitational-wave mergers are subject to systematics related to
their binary star progenitors; local measures of dark-matter substructure
masses are distorted by binary populations. In order to realize the scientific
goals in each of these themes over the next decade, we therefore need to
understand how binary stars and stellar multiplets are formed and distributed
in the space of masses, composition, age, and orbital properties, and how the
distribution evolves with time. This white paper emphasizes the
interdisciplinary importance of binary-star science and advocates that
coordinated investment from all astrophysical communities will benefit almost
all branches of astrophysics.Comment: Submitted to the Astro2020 Decadal Survey White Paper cal
Spectroscopy of the Young Stellar Association Price-Whelan 1: Origin in the Magellanic Leading Arm and Constraints on the Milky Way Hot Halo
We report spectroscopic measurements of stars in the recently discovered
young stellar association Price-Whelan 1 (PW 1), which was found in the
vicinity of the Leading Arm (LA) of the Magellanic Stream. We obtained
Magellan+MIKE high-resolution spectra of the 28 brightest stars in PW 1 and
used The Cannon to determine their stellar parameters. We find that the mean
metallicity of PW 1 is [Fe/H]=-1.23 with a small scatter of 0.06 dex and the
mean radial velocity is Vhelio=276.7 km/s with a dispersion of 11.0 km/s. Our
results are consistent in Teff, logg, and [Fe/H] with the young and metal-poor
characteristics (116 Myr and [Fe/H]=-1.1) determined for PW 1 from our
discovery paper. We find a strong correlation between the spatial pattern of
the PW 1 stars and the LA II gas with an offset of -10.15 deg in L_MS and +1.55
deg in B_MS. The similarity in metallicity, velocity, and spatial patterns
indicates that PW 1 likely originated in LA II. We find that the spatial and
kinematic separation between LA II and PW 1 can be explained by ram pressure
from Milky Way gas. Using orbit integrations that account for the LMC and MW
halo and outer disk gas, we constrain the halo gas density at the orbital
pericenter of PW 1 to be n_halo (17 kpc) = 2.7 (3) x 10^-3 atoms/cm^3 and the
disk gas density at the midplane at 20 kpc to be n_disk (20 kpc,0) = 6.0 (1.8)
x 10^-2 atoms/cm^3. We, therefore, conclude that PW 1 formed from the LA II of
the Magellanic Stream, making it a powerful constraint on the Milky
Way-Magellanic interaction.Comment: 18 pages, 13 figures, 1 table, submitted to Ap
Informed design of educational technology for teaching and learning? Towards an evidence-informed model of good practice
The aim of this paper is to model evidence-informed design based on a selective critical analysis of research articles. We draw upon findings from an investigation into practitioners’ use of educational technologies to synthesise and model what informs their designs. We found that practitioners’ designs were often driven by implicit assumptions about learning. These shaped both the design of interventions and the methods sought to derive evaluations and interpret the findings. We argue that interventions need to be grounded in better and explicit conceptualisations of what constitutes learning in order to have well-informed designs that focus on improving the quality of student learning
Two chemically similar stellar overdensities on opposite sides of the plane of the Galaxy
Our Galaxy is thought to have undergone an active evolutionary history
dominated by star formation, the accretion of cold gas, and, in particular,
mergers up to 10 gigayear ago. The stellar halo reveals rich fossil evidence of
these interactions in the form of stellar streams, substructures, and
chemically distinct stellar components. The impact of dwarf galaxy mergers on
the content and morphology of the Galactic disk is still being explored. Recent
studies have identified kinematically distinct stellar substructures and moving
groups, which may have extragalactic origin. However, there is mounting
evidence that stellar overdensities at the outer disk/halo interface could have
been caused by the interaction of a dwarf galaxy with the disk. Here we report
detailed spectroscopic analysis of 14 stars drawn from two stellar
overdensities, each lying about 5 kiloparsecs above and below the Galactic
plane - locations suggestive of association with the stellar halo. However, we
find that the chemical compositions of these stars are almost identical, both
within and between these groups, and closely match the abundance patterns of
the Milky Way disk stars. This study hence provides compelling evidence that
these stars originate from the disk and the overdensities they are part of were
created by tidal interactions of the disk with passing or merging dwarf
galaxies.Comment: accepted for publication in Natur
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