20,504 research outputs found
Tightly Correlated HI and FUV Emission in the Outskirts of M83
We compare sensitive HI data from The HI Nearby Galaxy Survey (THINGS) and
deep far UV (FUV) data from GALEX in the outer disk of M83. The FUV and HI maps
show a stunning spatial correlation out to almost 4 optical radii (r25),
roughly the extent of our maps. This underscores that HI traces the gas
reservoir for outer disk star formation and it implies that massive (at least
low level) star formation proceeds almost everywhere HI is observed. Whereas
the average FUV intensity decreases steadily with increasing radius before
leveling off at ~1.7 r25, the decline in HI surface density is more subtle. Low
HI columns (<2 M_solar/pc^2) contribute most of the mass in the outer disk,
which is not the case within r25. The time for star formation to consume the
available HI, inferred from the ratio of HI to FUV intensity, rises with
increasing radius before leveling off at ~100 Gyr, i.e., many Hubble times,
near ~1.7 r25. Assuming the relatively short H2 depletion times observed in the
inner parts of galaxies hold in outer disks, the conversion of HI into bound,
molecular clouds seems to limit star formation in outer galaxy disks. The long
consumption times suggest that most of the extended HI observed in M83 will not
be consumed by in situ star formation. However, even these low star formation
rates are enough to expect moderate chemical enrichment in a closed outer disk.Comment: Accepted for Publication in ApJ
Reflectance of Polytetrafluoroethylene (PTFE) for Xenon Scintillation Light
Gaseous and liquid xenon particle detectors are being used in a number of
applications including dark matter search and neutrino-less double beta decay
experiments. Polytetrafluoroethylene (PTFE) is often used in these detectors
both as electrical insulator and as a light reflector to improve the efficiency
of detection of scintillation photons. However, xenon emits in the vacuum
ultraviolet wavelength region (175 nm) where the reflecting properties of PTFE
are not sufficiently known.
In this work we report on measurements of PTFE reflectance, including its
angular distribution, for the xenon scintillation light. Various samples of
PTFE, manufactured by different processes (extruded, expanded, skived and
pressed) have been studied. The data were interpreted with a physical model
comprising both specular and diffuse reflections. The reflectance obtained for
these samples ranges from about 47% to 66% for VUV light. Fluoropolymers,
namely ETFE, FEP and PFA were also measured
Neutrino mass from higher than d=5 effective operators in SUSY, and its test at the LHC
We discuss neutrino masses from higher than d=5 effective operators in a
supersymmetric framework, where we explicitly demonstrate which operators could
be the leading contribution to neutrino mass in the MSSM and NMSSM. As an
example, we focus on the d=7 operator L L H_u H_u H_d H_u, for which we
systematically derive all tree-level decompositions. We argue that many of
these lead to a linear or inverse see-saw scenario with two extra neutral
fermions, where the lepton number violating term is naturally suppressed by a
heavy mass scale when the extra mediators are integrated out. We choose one
example, for which we discuss possible implementations of the neutrino flavor
structure. In addition, we show that the heavy mediators, in this case SU(2)
doublet fermions, may indeed be observable at the LHC, since they can be
produced by Drell-Yan processes and lead to displaced vertices when they decay.
However, the direct observation of lepton number violating processes is on the
edge at LHC.Comment: 24 pages, 5 figures, 6 table
Revisiting the Parallax of the Isolated Neutron Star RX J185635-3754 Using HST/ACS Imaging
We have redetermined the parallax and proper motion of the nearby isolated
neutron star RX~J185635-3754. We used eight observations with the high
resolution camera of the HST/ACS taken from 2002 through 2004. We performed the
astrometric fitting using five independent methods, all of which yielded
consistent results. The mean estimate of the distance is 123 (+11, -15) pc (1
sigma), in good agreement with our earlier published determination
Constraints on the Equation-of-State of neutron stars from nearby neutron star observations
We try to constrain the Equation-of-State (EoS) of supra-nuclear-density
matter in neutron stars (NSs) by observations of nearby NSs. There are seven
thermally emitting NSs known from X-ray and optical observations, the so-called
Magnificent Seven (M7), which are young (up to few Myrs), nearby (within a few
hundred pc), and radio-quiet with blackbody-like X-ray spectra, so that we can
observe their surfaces. As bright X-ray sources, we can determine their
rotational (pulse) period and their period derivative from X-ray timing. From
XMM and/or Chandra X-ray spectra, we can determine their temperature. With
precise astrometric observations using the Hubble Space Telescope, we can
determine their parallax (i.e. distance) and optical flux. From flux, distance,
and temperature, one can derive the emitting area - with assumptions about the
atmosphere and/or temperature distribution on the surface. This was recently
done by us for the two brightest M7 NSs RXJ1856 and RXJ0720. Then, from
identifying absorption lines in X-ray spectra, one can also try to determine
gravitational redshift. Also, from rotational phase-resolved spectroscopy, we
have for the first time determined the compactness (mass/radius) of the M7 NS
RBS1223. If also applied to RXJ1856, radius (from luminosity and temperature)
and compactness (from X-ray data) will yield the mass and radius - for the
first time for an isolated single neutron star. We will present our
observations and recent results.Comment: refereed NPA5 conference proceedings, in pres
Accounting: The basic for business decisions
The environment of accounting is changing fast, and this environmental changes, such as continued inflation and critical financials problem of many cities, affect the goals and the content of an introductory text in accounting. In order to function intelligently as a citizen as well as in a business of any size or type, every individual need more than ever before a clear understanding the accounting basic concept.
In this fifth edition, we have tried to reflect the impact of inflation on accounting measurements and to suggest the direction of needed changing on accounting concept and method. The importance of adequate disclosure in the system on financial reporting is stressed, and attention is drawn to the need for inprove accounting controls in all sectors of societ
Somatic embryogenesis from stem nodal sections of grapevine
Indirect somatic embryogenesis was obtained for 11 clones of 6 Vitis vinifera cultivars: Cabernet-Sauvignon, Chardonnay, Gewürztraminer, Grenache, Merlot and Sauvignon, and for the rootstock Fercal [(Vitis berlandieri x Vitis colombard) x (Vitis vinifera x Vitis berlandieri)], starting from vegetative explants of in vitro plantlets. Embryogenic callus was recovered from nodal explants of every tested clone, while leaf explants led to embryogenesis only for the rootstock Fercal. We thus showed that axillary bud microcuttings are valuable explants for inducing somatic embryogenesis in V. vinifera and Fercal. Embryogenic cell lines have been maintained through secondary embryogenesis, and some embryos were converted into whole plantlets. A complete protocol for somatic embryogenesis and plant regeneration was therefore designed, using this very simple method.
Small-scale Intensity Mapping: Extended Halos as a Probe of the Ionizing Escape Fraction and Faint Galaxy Populations during Reionization
We present a new method to quantify the value of the escape fraction of
ionizing photons, and the existence of ultra-faint galaxies clustered around
brighter objects during the epoch of cosmic reionization, using the diffuse
Ly, continuum and H emission observed around galaxies at
. We model the surface brightness profiles of the diffuse halos
considering the fluorescent emission powered by ionizing photons escaping from
the central galaxies, and the nebular emission from satellite star-forming
sources, by extending the formalisms developed in Mas-Ribas & Dijkstra (2016)
and Mas-Ribas et al. (2017). The comparison between our predicted profiles and
Ly observations at and favors a low ionizing escape
fraction, , for galaxies in the range . However, uncertainties and possible systematics in
the observations do not allow for firm conclusions. We predict H and
rest-frame visible continuum observations with JWST, and show that JWST will be
able to detect extended (a few tens of kpc) fluorescent H emission
powered by ionizing photons escaping from a bright, , galaxy.
Such observations can differentiate fluorescent emission from nebular emission
by satellite sources. We discuss how observations and stacking of several
objects may provide unique constraints on the escape fraction for faint
galaxies and/or the abundance of ultra-faint radiation sources.Comment: 9 pages, 4 figures, re-submitted after referee report to Ap
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