1,111 research outputs found
All-sky Kinematics and Chemistry of Monoceros Stellar Overdensity
We explore the kinematic and chemical properties of Monoceros stellar
overdensity by combining data from 2MASS, WISE, APOGEE, and .
Monoceros is a structure located towards the Galactic anticenter and close to
the disk. We identified that its stars have azimuthal velocity in the range of
. Combining their kinematics and
spatial distribution, we designed a new method to select stars from this
overdensity. This method allows us to easily identify the structure in both
hemispheres and estimate their distances. Our analysis was supported by
comparison with simulated data from the entire sky generated by
code. Furthermore, we characterized, for the first time, the
Monoceros overdensity in several chemical-abundance spaces. Our results confirm
its similarity to stars found in the thin disk of the Galaxy and suggest an
formation. Furthermore, we demonstrate that the southern
(Mon-S) and northern (Mon-N) regions of Monoceros exhibit indistinguishable
chemical compositions.Comment: Paper accepted for publication in Ap
The Chemodynamical Nature of the Triangulum-Andromeda Overdensity
We present a chemodynamical study of the Triangulum-Andromeda overdensity
(TriAnd) employing a sample of 31 candidate stars observed with the GRACES
high-resolution (=40,000) spectrograph at the Gemini North (8.1 m)
telescope. TriAnd is a stellar substructure found toward the outer disk of the
Milky Way, located at kpc from the Sun, toward Galactic
latitude {\deg}. Most stars in our sample have dynamical properties
compatible with a disk stellar population. In addition, by applying an
eccentricity cut, we are able to detect a stellar contamination that seems to
be consistent with an accreted population. In chemical abundance space, the
majority of our TriAnd candidates are similar to the outer thin-disk
population, suggesting that the overdensity has an \textit{in situ} origin.
Finally, the found accreted halo interlopers spatially overlapping with TriAnd
should explain the historical discussion of the overdensity's nature due to its
complex chemical patterns.Comment: Published in The Astrophysical Journal (ApJ
Carbon Fiber Composites of Pure Polypropylene and Maleated Polypropylene Blends Obtained from Injection and Compression Moulding
A comparative study of the mechanical performance of PP and PP/PP-g-MAH blends reinforced with carbon fibre (CF) obtained by two different moulding techniques is presented. Three filler contents were used for fabricating the composites: 1, 3, and 5 pph (parts per hundred). The crystallisation behaviour of the composites was studied by differential scanning calorimetry. Morphological and structural features of these samples were observed by atomic field microscopy and Fourier-transform infrared spectroscopy, respectively. Mechanical properties of the injection and compression moulded composites were evaluated by means of tensile and impact resistance tests. The fracture surface of the impacted samples was observed by scanning electron microscopy. The processing method had a noticeable effect on the results obtained in these tests. Young’s modulus was enhanced up to 147% when adding 5 pph CF to a PP matrix when processed by compression moulding. Addition of PP-g-MAH and CF had a favourable effect on the tensile and impact strength properties in most samples; these composites showed improved performance as the filler content was increased
A Higher-Order Logic for Concurrent Termination-Preserving Refinement
Compiler correctness proofs for higher-order concurrent languages are difficult: they involve establishing a termination-preserving refinement between a concurrent high-level source language and an implementation that uses low-level shared memory primitives. However, existing logics for proving concurrent refinement either neglect properties such as termination, or only handle first-order state. In this paper, we address these limitations by extending Iris, a recent higher-order concurrent separation logic, with support for reasoning about termination-preserving refinements. To demonstrate the power of these extensions, we prove the correctness of an efficient implementation of a higher-order, session-typed language. To our knowledge, this is the first program logic capable of giving a compiler correctness proof for such a language. The soundness of our extensions and our compiler correctness proof have been mechanized in Coq
Physical activity, screen time and the COVID-19 school closures in Europe – an observational study in 10 countries
To date, few data on how the COVID-19 pandemic and restrictions affected children’s physical activity in Europe have been published. This study examined the prevalence and correlates of physical activity and screen time from a large sample of European children during the COVID-19 pandemic to inform strategies and provide adequate mitigation measures. An online survey was conducted using convenience sampling from 15 May to 22 June, 2020. Parents were eligible if they resided in one of the survey countries and their children aged 6–18 years. 8395 children were included (median age [IQR], 13 [10–15] years; 47% boys; 57.6% urban residents; 15.5% in self-isolation). Approximately two-thirds followed structured routines (66.4% [95%CI, 65.4–67.4]), and more than half were active during online P.E. (56.6% [95%CI, 55.5–57.6]). 19.0% (95%CI, 18.2–19.9) met the WHO Global physical activity recommendation. Total screen time in excess of 2 h/day was highly prevalent (weekdays: 69.5% [95%CI, 68.5–70.5]; weekend: 63.8% [95%CI, 62.7–64.8]). Playing outdoors more than 2 h/day, following a daily routine and being active in online P.E. increased the odds of healthy levels of physical activity and screen time, particularly in mildly affected countries. In severely affected countries, online P.E. contributed most to meet screen time recommendation, whereas outdoor play was most important for adequate physical activity. Promoting safe and responsible outdoor activities, safeguarding P.E. lessons during distance learning and setting pre-planned, consistent daily routines are important in helping children maintain healthy active lifestyle in pandemic situation. These factors should be prioritised by policymakers, schools and parents.
Highlights
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To our knowledge, our data provide the first multi-national estimates on physical activity and total screen time in European children roughly two months after COVID-19 was declared a global pandemic.
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Only 1 in 5 children met the WHO Global physical activity recommendations.
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Under pandemic conditions, parents should set pre-planned, consistent daily routines and integrate at least 2-hours outdoor activities into the daily schedule, preferable on each day. Schools should make P.E. lessons a priority. Decision makers should mandate online P.E. be delivered by schools during distance learning. Closing outdoor facilities for PA should be considered only as the last resort during lockdowns
The physical properties of star forming galaxies in the low redshift universe
(modified) We present a comprehensive study of the physical properties of
\~10^5 galaxies with measurable star formation in the SDSS. By comparing
physical information extracted from the emission lines with continuum
properties, we build up a picture of the nature of star-forming galaxies at
z<0.2. We take out essentially all aperture bias using resolved imaging,
allowing an accurate estimate of the total SFRs in galaxies. We determine the
SFR density to be 1.915^{+0.02}_{-0.01}(rand.)^{+0.14}_{-0.42} (sys.) h70
10^{-2} Msun/yr/Mpc^3 at z=0.1 (for a Kroupa IMF) and we study the distribution
of star formation as a function of various physical parameters. The majority of
the star formation in the low redshift universe takes place in moderately
massive galaxies (10^10-10^11 Msun), typically in HSB disk galaxies. Roughly
15% of all star formation takes place in galaxies that show some sign of an
active nucleus. About 20% occurs in starburst galaxies. We show that the
present to past-average star formation rate, the Scalo b-parameter; is almost
constant over almost three orders of magnitude in mass, declining only at
M*>10^10 Msun. The volume averaged b parameter is 0.408^{+0.005}_{-0.002}
(rand).^{+0.029}_{-0.090} (sys.) h70^{-1}. We use this value constrain the star
formation history of the universe. In agreement with other work we find a
correlation between and morphological type, as well as a tight correlation
between the 4000AA break (D4000) and b. We discuss how D4000 can be used to
estimate b parameters for high redshift galaxies.Comment: Accepted for MNRAS. Replaced with accepted version. A section on
comparison with other methods of SFR estimation added and various updates
have been made. The main results are almost unchange
Astrobiological Complexity with Probabilistic Cellular Automata
Search for extraterrestrial life and intelligence constitutes one of the
major endeavors in science, but has yet been quantitatively modeled only rarely
and in a cursory and superficial fashion. We argue that probabilistic cellular
automata (PCA) represent the best quantitative framework for modeling
astrobiological history of the Milky Way and its Galactic Habitable Zone. The
relevant astrobiological parameters are to be modeled as the elements of the
input probability matrix for the PCA kernel. With the underlying simplicity of
the cellular automata constructs, this approach enables a quick analysis of
large and ambiguous input parameters' space. We perform a simple clustering
analysis of typical astrobiological histories and discuss the relevant boundary
conditions of practical importance for planning and guiding actual empirical
astrobiological and SETI projects. In addition to showing how the present
framework is adaptable to more complex situations and updated observational
databases from current and near-future space missions, we demonstrate how
numerical results could offer a cautious rationale for continuation of
practical SETI searches.Comment: 37 pages, 11 figures, 2 tables; added journal reference belo
Planck 2015 results. XXVII. The second Planck catalogue of Sunyaev-Zeldovich sources
Catalogs and data.-- et al.We present the all-sky Planck catalogue of Sunyaev-Zeldovich (SZ) sources detected from the 29 month full-mission data. The catalogue (PSZ2) is the largest SZ-selected sample of galaxy clusters yet produced and the deepest systematic all-sky surveyof galaxy clusters. It contains 1653 detections, of which 1203 are confirmed clusters with identified counterparts in external data sets, and is the first SZ-selected cluster survey containing >103 confirmed clusters. We present a detailed analysis of the survey selection function in terms of its completeness and statistical reliability, placing a lower limit of 83% on the purity. Using simulations, we find that the estimates of the SZ strength parameter Y5R500are robust to pressure-profile variation and beam systematics, but accurate conversion to Y500 requires the use of prior information on the cluster extent. We describe the multi-wavelength search for counterparts in ancillary data, which makes use of radio, microwave, infra-red, optical, and X-ray data sets, and which places emphasis on the robustness of the counterpart match. We discuss the physical properties of the new sample and identify a population of low-redshift X-ray under-luminous clusters revealed by SZ selection. These objects appear in optical and SZ surveys with consistent properties for their mass, but are almost absent from ROSAT X-ray selected samples.The Planck Collaboration acknowledges the support of: ESA; CNES and CNRS/INSU-IN2P3-INP (France); ASI, CNR, and INAF (Italy); NASA and DoE (USA); STFC and UKSA (UK); CSIC, MINECO, JA, and RES (Spain); Tekes, AoF, and CSC (Finland); DLR and MPG (Germany); CSA (Canada); DTU Space (Denmark); SER/SSO (Switzerland); RCN (Norway); SFI (Ireland); FCT/MCTES (Portugal); ERC and PRACE (EU).Peer Reviewe
Planck 2015 results. XXIII. The thermal Sunyaev-Zeldovich effect--cosmic infrared background correlation
We use Planck data to detect the cross-correlation between the thermal
Sunyaev-Zeldovich (tSZ) effect and the infrared emission from the galaxies that
make up the the cosmic infrared background (CIB). We first perform a stacking
analysis towards Planck-confirmed galaxy clusters. We detect infrared emission
produced by dusty galaxies inside these clusters and demonstrate that the
infrared emission is about 50% more extended than the tSZ effect. Modelling the
emission with a Navarro--Frenk--White profile, we find that the radial profile
concentration parameter is . This indicates
that infrared galaxies in the outskirts of clusters have higher infrared flux
than cluster-core galaxies. We also study the cross-correlation between tSZ and
CIB anisotropies, following three alternative approaches based on power
spectrum analyses: (i) using a catalogue of confirmed clusters detected in
Planck data; (ii) using an all-sky tSZ map built from Planck frequency maps;
and (iii) using cross-spectra between Planck frequency maps. With the three
different methods, we detect the tSZ-CIB cross-power spectrum at significance
levels of (i) 6 , (ii) 3 , and (iii) 4 . We model the
tSZ-CIB cross-correlation signature and compare predictions with the
measurements. The amplitude of the cross-correlation relative to the fiducial
model is . This result is consistent with
predictions for the tSZ-CIB cross-correlation assuming the best-fit
cosmological model from Planck 2015 results along with the tSZ and CIB scaling
relations.Comment: 18 pages, 16 figure
Planck Intermediate Results. IV. The XMM-Newton validation programme for new Planck galaxy clusters
We present the final results from the XMM-Newton validation follow-up of new
Planck galaxy cluster candidates. We observed 15 new candidates, detected with
signal-to-noise ratios between 4.0 and 6.1 in the 15.5-month nominal Planck
survey. The candidates were selected using ancillary data flags derived from
the ROSAT All Sky Survey (RASS) and Digitized Sky Survey all-sky maps, with the
aim of pushing into the low SZ flux, high-z regime and testing RASS flags as
indicators of candidate reliability. 14 new clusters were detected by XMM,
including 2 double systems. Redshifts lie in the range 0.2 to 0.9, with 6
clusters at z>0.5. Estimated M500 range from 2.5 10^14 to 8 10^14 Msun. We
discuss our results in the context of the full XMM validation programme, in
which 51 new clusters have been detected. This includes 4 double and 2 triple
systems, some of which are chance projections on the sky of clusters at
different z. We find that association with a RASS-BSC source is a robust
indicator of the reliability of a candidate, whereas association with a FSC
source does not guarantee that the SZ candidate is a bona fide cluster.
Nevertheless, most Planck clusters appear in RASS maps, with a significance
greater than 2 sigma being a good indication that the candidate is a real
cluster. The full sample gives a Planck sensitivity threshold of Y500 ~ 4 10^-4
arcmin^2, with indication for Malmquist bias in the YX-Y500 relation below this
level. The corresponding mass threshold depends on z. Systems with M500 > 5
10^14 Msun at z > 0.5 are easily detectable with Planck. The newly-detected
clusters follow the YX-Y500 relation derived from X-ray selected samples.
Compared to X-ray selected clusters, the new SZ clusters have a lower X-ray
luminosity on average for their mass. There is no indication of departure from
standard self-similar evolution in the X-ray versus SZ scaling properties.
(abridged)Comment: accepted by A&
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