414 research outputs found
Galaxy transmutations: The double ringed galaxy ESO 474-G26
Surface photometry and a 21cm HI line spectrum of the giant double-ringed
galaxy ESO 474-G26 are presented. The morphology of this system is unique among
the 30,000 galaxies with >B15. Two almost orthogonal optical rings with
diameters of 60 and 40 kpc surround the central body (assuming H0=70 km/s/Mpc).
The outer one is an equatorial ring, while the inner ring lies in a nearly
polar plane. The rings have blue optical colors typical of late-type spirals.
Both appear to be rotating around the central galaxy, so that this system can
be considered as a kinematically confirmed polar ring galaxy. Its observational
characteristics are typical of galaxy merger remnants. Although the central
object has a surface brightness distribution typical of elliptical galaxies, it
has a higher surface brightness for its effective radius than ordinary
ellipticals. Possible origins of this galaxy are discussed and numerical
simulations are presented that illustrate the formation of the two rings in the
merging process of two spiral galaxies, in which the observed appearance of ESO
474-G26 appears to be a transient stage.Comment: Accepted for publication in A&
Pitch angles of distant spiral galaxies
We have studied the pitch angles of spiral arms for 31 distant galaxies at
z~0.7 from three Hubble Deep Fields (HDF-N, HDF-S, HUDF). Using the pitch angle
- rotation velocity relation calibrated from nearby galaxies, we have estimated
the rotation velocities of galaxies from the deep fields. These estimates have
a low accuracy (~50 km/s), but they allow low-mass and giant galaxies to be
distinguished. The Tully-Fisher relation constructed using our velocity
estimates shows satisfactory agreement with the actually observed relations for
distant galaxies and provides evidence for the luminosity evolution of spiral
galaxies.Comment: 9 pages, 6 figure
RC J0311+0507: A Candidate for Superpowerful Radio Galaxies in the Early Universe at Redshift z=4.514
A strong emission line at 6703A has been detected in the optical spectrum for
the host galaxy (R=23.1) of the radio source RC J0311+0507 (4C+04.11). This
radio galaxy, with a spectral index of 1.31 in the frequency range 365-4850
MHz, is one of the ultrasteep spectrum objects from the deep survey of a sky
strip conducted with RATAN-600 in 1980-1981. We present arguments in favor of
the identification of this line with Ly\alpha at redshift z=4.514. In this
case, the object belongs to the group of extremely distant radio galaxies of
ultrahigh radio luminosity (P_{1400}=1.3 x 10^{29}W Hz^{-1}). Such power can be
provided only by a fairly massive black hole (~10^9M_\sun}) that formed in a
time less than the age of the Universe at the observed z(1.3 Gyr) or had a
primordial origin.Comment: 8 pages, 3 figure
Critical Pause: Athletes’ Stories of Lockdown during COVID-19
This study explored the experiences of elite athletes during the initial stages of lockdown as a result of the COVID-19 pandemic. The eight recruited participants (three females, five males) were asked to tell a story of their lockdown experience. Narrative analysis was used to explore the athletes’ stories. The athletes’ narrative is best represented in four distinct sections: a) Threat to Goals, b) On-Going Consequences, c) Overcoming COVID-19, and d) Adapting to COVID-19. Four narrative themes were also co-constructed from the athletes’ stories: a) Factors Athletes Found Challenging, b) Loss, c) Strategies that Benefitted Athletes Psychologically, and d) Silver Linings. Combined, these findings suggest that the initial stages of lockdown are best described as a critical pause. We present applied implications for athletes and sport psychology practitioners. We also recommend future research investigate the longitudinal effect of prolonged lockdown on athletes’ lives and a potential return to sport
Collins and Sivers asymmetries in muonproduction of pions and kaons off transversely polarised proton
Measurements of the Collins and Sivers asymmetries for charged pions and
charged and neutral kaons produced in semi-inclusive deep-inelastic scattering
of high energy muons off transversely polarised protons are presented. The
results were obtained using all the available COMPASS proton data, which were
taken in the years 2007 and 2010. The Collins asymmetries exhibit in the
valence region a non-zero signal for pions and there are hints of non-zero
signal also for kaons. The Sivers asymmetries are found to be positive for
positive pions and kaons and compatible with zero otherwise.Comment: 15 pages, 13 figures and 1 tabl
Search for exclusive photoproduction of Z(3900) at COMPASS
A search for the exclusive production of the hadron by
virtual photons has been performed in the channel . The data cover the range from 7 GeV to 19 GeV in the
centre-of-mass energy of the photon-nucleon system. The full set of the COMPASS
data set collected with a muon beam between 2002 and 2011 has been used. An
upper limit for the ratio of has been established at the confidence
level of 90%.Comment: 8 pages, 3 figures, 1 tabl
Measurement of the charged-pion polarisability
The COMPASS collaboration at CERN has investigated pion Compton scattering,
, at centre-of-mass energy below 3.5 pion
masses. The process is embedded in the reaction
, which is initiated by
190\,GeV pions impinging on a nickel target. The exchange of quasi-real photons
is selected by isolating the sharp Coulomb peak observed at smallest momentum
transfers, \,(GeV/). From a sample of 63\,000 events the
pion electric polarisability is determined to be $\alpha_\pi\ =\ (\,2.0\ \pm\
0.6_{\mbox{\scriptsize stat}}\ \pm\ 0.7_{\mbox{\scriptsize syst}}\,) \times
10^{-4}\,\mbox{fm}^3\alpha_\pi=-\beta_\pi$, which
relates the electric and magnetic dipole polarisabilities. It is the most
precise measurement of this fundamental low-energy parameter of strong
interaction, that has been addressed since long by various methods with
conflicting outcomes. While this result is in tension with previous dedicated
measurements, it is found in agreement with the expectation from chiral
perturbation theory. An additional measurement replacing pions by muons, for
which the cross-section behavior is unambigiously known, was performed for an
independent estimate of the systematic uncertainty.Comment: Published version: 9 pages, 3 figures, 1 tabl
Spin alignment and violation of the OZI rule in exclusive and production in pp collisions
Exclusive production of the isoscalar vector mesons and is
measured with a 190 GeV proton beam impinging on a liquid hydrogen target.
Cross section ratios are determined in three intervals of the Feynman variable
of the fast proton. A significant violation of the OZI rule is found,
confirming earlier findings. Its kinematic dependence on and on the
invariant mass of the system formed by fast proton
and vector meson is discussed in terms of diffractive
production of resonances in competition with central
production. The measurement of the spin density matrix element of
the vector mesons in different selected reference frames provides another
handle to distinguish the contributions of these two major reaction types.
Again, dependences of the alignment on and on are
found. Most of the observations can be traced back to the existence of several
excited baryon states contributing to production which are absent in
the case of the meson. Removing the low-mass resonant
region, the OZI rule is found to be violated by a factor of eight,
independently of .Comment: 23 pages, 13 figures and 5 table
First Measurement of Chiral Dynamics in \pi^- \gamma -> \pi^- \pi^- \pi^+
The COMPASS collaboration at CERN has investigated the \pi^- \gamma -> \pi^-
\pi^- \pi^+ reaction at center-of-momentum energy below five pion masses,
sqrt(s) < 5 m(\pi), embedded in the Primakoff reaction of 190 GeV pions
impinging on a lead target. Exchange of quasi-real photons is selected by
isolating the sharp Coulomb peak observed at smallest momentum transfers, t' <
0.001 (GeV/c)^2. Using partial-wave analysis techniques, the scattering
intensity of Coulomb production described in terms of chiral dynamics and its
dependence on the 3\pi-invariant mass m(3\pi) = sqrt(s) were extracted. The
absolute cross section was determined in seven bins of with an
overall precision of 20%. At leading order, the result is found to be in good
agreement with the prediction of chiral perturbation theory over the whole
energy range investigated.Comment: 10 pages, 5 figure
Longitudinal double spin asymmetries in single hadron quasi-real photoproduction at high
We measured the longitudinal double spin asymmetries for single
hadron muo-production off protons and deuterons at photon virtuality <
1(GeV/) for transverse hadron momenta in the range 0.7
GeV/ to 4 GeV/ . They were determined using COMPASS data taken
with a polarised muon beam of 160 GeV/ or 200 GeV/ impinging on
polarised or targets. The experimental
asymmetries are compared to next-to-leading order pQCD calculations, and are
sensitive to the gluon polarisation inside the nucleon in the range
of the nucleon momentum fraction carried by gluons
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