2,749 research outputs found
SMASHing the LMC: A Tidally-induced Warp in the Outer LMC and a Large-scale Reddening Map
We present a study of the three-dimensional (3D) structure of the Large
Magellanic Cloud (LMC) using ~2.2 million red clump (RC) stars selected from
the Survey of the MAgellanic Stellar History. To correct for line-of-sight dust
extinction, the intrinsic RC color and magnitude and their radial dependence
are carefully measured by using internal nearly dust-free regions. These are
then used to construct an accurate 2D reddening map (165 square degrees with
~10 arcmin resolution) of the LMC disk and the 3D spatial distribution of RC
stars. An inclined disk model is fit to the 2D distance map yielding a best-fit
inclination angle i = 25.86(+0.73,-1.39) degrees with random errors of +\-0.19
degrees and line-of-nodes position angle theta = 149.23(+6.43,-8.35) degrees
with random errors of +/-0.49 degrees. These angles vary with galactic radius,
indicating that the LMC disk is warped and twisted likely due to the repeated
tidal interactions with the Small Magellanic Cloud (SMC). For the first time,
our data reveal a significant warp in the southwestern part of the outer disk
starting at rho ~ 7 degrees that departs from the defined LMC plane up to ~4
kpc toward the SMC, suggesting that it originated from a strong interaction
with the SMC. In addition, the inner disk encompassing the off-centered bar
appears to be tilted up to 5-15 degrees relative to the rest of the LMC disk.
These findings on the outer warp and the tilted bar are consistent with the
predictions from the Besla et al. simulation of a recent direct collision with
the SMC.Comment: 25 pages, 15 figures, published in Ap
IN PRAISE OF ENLIGHTENED PARTICULARITY
Autor u svojoj studiji analizira odnos opće kulture i njenih posebnih segmenata unutar jedinstvene političke zajednice te zaključuje: dok god, dakle, postoje građani, postojat će i sukob između općega i posebnog, i pritom će se uvijek iznova pokazivati da posredovanje između te dvije kategorije nikada nije konačno, nego da uvijek iznova treba određivati što je primjereno, što je ono pravo i obvezujuće. U tome se očituje snaga prosuđivanja kojoj su shematske orijentacije poput univerzalizma i partikularizma potrebne samo da bi se ukazalo na ono što nedostaje, te da bi se to nadopunilo.In this study, the author analyses the relationship between general culture and its particularistic segments within the integral political community and concludes: as long as there are citizens, there will be a conflict between the general and the singular; also, the mediation between these two categories is never final; instead, one should repeatedly define what is appropriate, right and compulsory. This is the strength of the type of reasoning to which the schematic landmarks such as universalism and particularism are necessary only as reminders of what is missing in order to fill in the gaps
Bright Stars and Recent Star Formation in the Irregular Magellanic Galaxy NGC2366
The stellar content of the Im galaxy NGC 2366 is discussed on the basis of
CCD BVR photometry. The three brightest blue and red stars have been used to
estimate its distance, obtaining a balue of 2.9 Mpc. The spatial distribution
of the young stellar population is discussed in the light of the integrated
color indices and the color-magnitude diagrams of different zones of the
galaxy. A generalized star formation burst seems to have taken place about 50
Myr ago. The youngest stars are preferentially formed in the South-West part of
the bar, where the giant HII complex NGC 2363 is located, being younger and
bluer. The bar seems to play a role favouring star formation in one of its
extremes. Self-propagation however, does not seem to be triggering star
formation at large scale. A small region, populated by very young stars has
also been found at the East of the galaxy.Comment: Astronomical Journal, accepted. This is a uuencoded, compressed, tar
file (102 Kbytes) of 1 text, 1 table postscript files. Figures are retrieved
as a separate file. One single file with all figures and tables (552Kb) also
available from http://www.ast.cam.ac.uk/~etelles/astronomy.htm
Cervical dysplasia and cancer and the use of hormonal contraceptives in Jamaican women
<p>Abstract</p> <p>Background</p> <p>This study was conducted to determine whether use of hormonal contraceptives is associated with cervical dysplasia and cancer in a population where there is widespread use of hormonal contraception and the rates of cervical cancer remain high at 27.5/100,000.</p> <p>Methods</p> <p>A case-control study was conducted among women visiting the colposcopy and gynaelogical clinics at a tertiary referral hospital. Two hundred and thirty six cases CIN I (72), II (59), III (54), cancer (51) and 102 controls, consented and were interviewed on use of contraceptives using a structured questionnaire. Logistic regression was used to determine odds ratios (ORs) and 95% confidence intervals (CIs) associated with use of hormonal contraception in cases and controls and in low and high risk cases. Recruitment was carried out from 2001–2002.</p> <p>Results</p> <p>Contraceptives used were: oral contraceptives – 35%, injections (depot medroxy progesterone acetate (Depo-provera) – 10%, Intrauterine devices – 2%, combinations of these and tubal ligation – 30%. 23% reported use of 'other' methods, barrier contraceptives or no form of contraception. Barrier contraceptive use was not significantly different between cases and controls. Current and/or past exposure to hormonal contraceptives (HC) by use of the pill or injection, alone or in combination with other methods was significantly higher in the cases. In multivariate analysis with age and number of sexual partners as co-variates, use of hormonal contraception was associated both with disease, [OR, 1.92 (CI 1.11, 3.34; p = 0.02] and severity of the disease [OR, 2.22 (CI 1.05, 4.66) p = 0.036]. When parity and alcohol consumption were added to the model, hormonal contraception was no longer significant. The significant association with high risk disease was retained when the model was controlled for age and number of sexual partners. Depo-provera use (with age and number of sexual partners as covariates) was also associated with disease [OR, 2.43 (CI 1.39, 4.57), p = 0.006] and severity of disease [OR 2.51 (1.11, 5.64) p = 0.027]. With parity and alcohol added to this model, depo-provera use retained significance. Exposure to HC > 4 years conferred more risk for disease and severity of disease.</p> <p>Conclusion</p> <p>Hormonal contraception did confer some risk of dysplasia and women using HC should therefore be encouraged to do regular Pap smear screening.</p
Multi-Wavelength Observations of the Blazar 1ES 1011+496 in Spring 2008
The BL Lac object 1ES 1011+496 was discovered at Very High Energy gamma-rays
by MAGIC in spring 2007. Before that the source was little studied in different
wavelengths. Therefore a multi-wavelength (MWL) campaign was organized in
spring 2008. Along MAGIC, the MWL campaign included the Metsahovi radio
observatory, Bell and KVA optical telescopes and the Swift and AGILE
satellites. MAGIC observations span from March to May, 2008 for a total of 27.9
hours, of which 19.4 hours remained after quality cuts. The light curve showed
no significant variability. The differential VHE spectrum could be described
with a power-law function. Both results were similar to those obtained during
the discovery. Swift XRT observations revealed an X-ray flare, characterized by
a harder when brighter trend, as is typical for high synchrotron peak BL Lac
objects (HBL). Strong optical variability was found during the campaign, but no
conclusion on the connection between the optical and VHE gamma-ray bands could
be drawn. The contemporaneous SED shows a synchrotron dominated source, unlike
concluded in previous work based on nonsimultaneous data, and is well described
by a standard one zone synchrotron self Compton model. We also performed a
study on the source classification. While the optical and X-ray data taken
during our campaign show typical characteristics of an HBL, we suggest, based
on archival data, that 1ES 1011+496 is actually a borderline case between
intermediate and high synchrotron peak frequency BL Lac objects.Comment: 13 pages, accepted for publication in MNRA
The major upgrade of the MAGIC telescopes, Part II: A performance study using observations of the Crab Nebula
MAGIC is a system of two Imaging Atmospheric Cherenkov Telescopes located in
the Canary island of La Palma, Spain. During summer 2011 and 2012 it underwent
a series of upgrades, involving the exchange of the MAGIC-I camera and its
trigger system, as well as the upgrade of the readout system of both
telescopes. We use observations of the Crab Nebula taken at low and medium
zenith angles to assess the key performance parameters of the MAGIC stereo
system. For low zenith angle observations, the standard trigger threshold of
the MAGIC telescopes is ~50GeV. The integral sensitivity for point-like sources
with Crab Nebula-like spectrum above 220GeV is (0.66+/-0.03)% of Crab Nebula
flux in 50 h of observations. The angular resolution, defined as the sigma of a
2-dimensional Gaussian distribution, at those energies is < 0.07 degree, while
the energy resolution is 16%. We also re-evaluate the effect of the systematic
uncertainty on the data taken with the MAGIC telescopes after the upgrade. We
estimate that the systematic uncertainties can be divided in the following
components: < 15% in energy scale, 11-18% in flux normalization and +/-0.15 for
the energy spectrum power-law slope.Comment: 21 pages, 25 figures, accepted for publication in Astroparticle
Physic
Probing the very-high-energy gamma-ray spectral curvature in the blazar PG 1553+113 with the MAGIC telescopes
PG 1553+113 is a very-high-energy (VHE, ) -ray
emitter classified as a BL Lac object. Its redshift is constrained by
intergalactic absorption lines in the range . The MAGIC telescopes
have monitored the source's activity since 2005. In early 2012, PG 1553+113 was
found in a high-state, and later, in April of the same year, the source reached
its highest VHE flux state detected so far. Simultaneous observations carried
out in X-rays during 2012 April show similar flaring behaviour. In contrast,
the -ray flux at observed by Fermi-LAT is
compatible with steady emission. In this paper, a detailed study of the flaring
state is presented. The VHE spectrum shows clear curvature, being well fitted
either by a power law with an exponential cut-off or by a log-parabola. A
simple power-law fit hypothesis for the observed shape of the PG 1553+113 VHE
-ray spectrum is rejected with a high significance (fit probability
P=2.6 ). The observed curvature is compatible with the
extragalactic background light (EBL) imprint predicted by current generation
EBL models assuming a redshift . New constraints on the redshift are
derived from the VHE spectrum. These constraints are compatible with previous
limits and suggest that the source is most likely located around the optical
lower limit, , based on the detection of Ly absorption. Finally,
we find that the synchrotron self-Compton (SSC) model gives a satisfactory
description of the observed multi-wavelength spectral energy distribution
during the flare.Comment: 13 pages, 7 figures, accepted for publication in MNRA
Measurement of the cross-section and charge asymmetry of bosons produced in proton-proton collisions at TeV with the ATLAS detector
This paper presents measurements of the and cross-sections and the associated charge asymmetry as a
function of the absolute pseudorapidity of the decay muon. The data were
collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with
the ATLAS experiment at the LHC and correspond to a total integrated luminosity
of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements
varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the
1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured
with an uncertainty between 0.002 and 0.003. The results are compared with
predictions based on next-to-next-to-leading-order calculations with various
parton distribution functions and have the sensitivity to discriminate between
them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables,
submitted to EPJC. All figures including auxiliary figures are available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13
Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector
A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13 TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV
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