15,241 research outputs found
Interstellar H2 toward HD 37903
We present an analysis of interstellar H2 toward HD 37903, which is a hot, B
1.5 V star located in the NGC 2023 reflection nebula. Meyer et al. (2001) have
used a rich spectrum of vibrationally excited H2 observed by the HST to
calculate a model of the interstellar cloud toward HD 37903. We extend Mayer's
analysis by including the v"=0 vibrational level observed by the FUSE
satellite.
The T01 temperature should not be interpreted as a rotational temperature,
but rather as a temperature of thermal equilibrium between the ortho and para
H2. The ortho to para H2 ratio is lower for collisionally populated levels than
for the levels populated by fluorescence.
The PDR model of the cloud located in front of HD 37903 points to a gas
temperature Tkin=110-377 K, hydrogen density nH=1874-544 cm^-3 and the
star-cloud distance of 0.45 pc
Metastable states of a driven flux lattice in a superconductor with strong pins
The flux lattice driven by a uniform driving force in a superconductor with
hot, strong, sharp and randomly distributed pinning centers, with applied
magnetic field half the matching field is simulated. At low temperature both a
non activated regime, where flux motion occurs within a robust percolative flux
flow channel, and an activated regime are obtained depending on the sample
preparation. These two regimes exhibit distinct resistivity and magnetic
induction. In the non activated regime, a clear fingerprint is observed in the
autocorrelation function of the longitudinal resitivity, which oscillates at a
frequency close to the inverse lattice diffusion time.Comment: 6 figure
Economic Instruments and the Pollution Impact of the 2006-2010 Vietnam Socio-Economic Development Plan
The current study derives optimal growth paths for pollution emission charges, in order to control future water pollution emissions in the Vietnamese manufacturing sector. The study builds on a prior study, which estimated the manufacturing sector pollution impact of the 2006- 2010 SEDP development plan for Vietnam (Jensen et al.; 2008). The current study demonstrates that effective implementation and moderate expansion of optimal emission charges, under certain conditions, could have been used, as part of the 2006-2010 SEDP development plan, to control pollution emissions at 2005 levels. Moreover, such a scenario would have been accompanied by a moderate expansion in fiscal revenues and a relatively minor economy-wide efficiency loss. The current study, therefore, suggests that effective implementation and gradual expansion of pollution emission charges should be incorporated into future SEDP development plans, in order to control pollution emissions as development progresses in Vietnam.Vietnam, manufacturing, CGE
Angle-resolved photoemission study of the role of nesting and orbital orderings in the antiferromagnetic phase of BaFe2As2
We present a detailed comparison of the electronic structure of BaFe2As2 in
its paramagnetic and antiferromagnetic (AFM) phases, through angle-resolved
photoemission studies. Using different experimental geometries, we resolve the
full elliptic shape of the electron pockets, including parts of dxy symmetry
along its major axis that are usually missing. This allows us to define
precisely how the hole and electron pockets are nested and how the different
orbitals evolve at the transition. We conclude that the imperfect nesting
between hole and electron pockets explains rather well the formation of gaps
and residual metallic droplets in the AFM phase, provided the relative parity
of the different bands is taken into account. Beyond this nesting picture, we
observe shifts and splittings of numerous bands at the transition. We show that
the splittings are surface sensitive and probably not a reliable signature of
the magnetic order. On the other hand, the shifts indicate a significant
redistribution of the orbital occupations at the transition, especially within
the dxz/dyz system, which we discuss
The Central Regions of M31 in the 3 - 5 micron Wavelength Region
Images obtained with NIRI on the Gemini North telescope are used to
investigate the photometric properties of the central regions of M31 in the 3 -
5 micron wavelength range. The light distribution in the central arcsecond
differs from what is seen in the near-infrared in the sense that the difference
in peak brigh tness between P1 and P2 is larger in M' than in K'; no obvious
signature of P3 is dete cted in M'. These results can be explained if there is
a source of emission that contributes ~ 20% of the peak M' light of P1 and has
an effective temperature of no more than a few hundred K that is located
between P1 and P2. Based on the red K-M' color of this source, it is suggested
that the emission originates in a circumstellar dust shell surrounding a single
bright AGB star. A similar bright source that is ~ 8 arcsec from the center of
the galaxy is also detected in M'. Finally, the (L', K-L') color-magnitude
diagram of unblended stars shows a domin ant AGB population with photometric
characteristics that are similar to those of the most luminous M giants in the
Galactic bulge.Comment: To appear in the Astronomical Journa
An easy proof of Jensen's theorem on the uniqueness of infinity harmonic functions
We present a new, easy, and elementary proof of Jensen's Theorem on the
uniqueness of infinity harmonic functions. The idea is to pass to a finite
difference equation by taking maximums and minimums over small balls.Comment: 4 pages; comments added, proof simplifie
Spitzer bright, UltraVISTA faint sources in COSMOS: the contribution to the overall population of massive galaxies at z=3-7
We have analysed a sample of 574 Spitzer 4.5 micron-selected galaxies with
[4.5]24 (AB) over the UltraVISTA ultra-deep COSMOS field. Our
aim is to investigate whether these mid-IR bright, near-IR faint sources
contribute significantly to the overall population of massive galaxies at
redshifts z>=3. By performing a spectral energy distribution (SED) analysis
using up to 30 photometric bands, we have determined that the redshift
distribution of our sample peaks at redshifts z~2.5-3.0, and ~32% of the
galaxies lie at z>=3. We have studied the contribution of these sources to the
galaxy stellar mass function (GSMF) at high redshifts. We found that the
[4.5]24 galaxies produce a negligible change to the GSMF
previously determined for Ks_auto<24 sources at 3=<z<4, but their contribution
is more important at 4=~50% of the galaxies with stellar
masses Mst>~6 x 10^10 Msun. We also constrained the GSMF at the highest-mass
end (Mst>~2 x 10^11 Msun) at z>=5. From their presence at 5=<z<6, and virtual
absence at higher redshifts, we can pinpoint quite precisely the moment of
appearance of the first most massive galaxies as taking place in the ~0.2 Gyr
of elapsed time between z~6 and z~5. Alternatively, if very massive galaxies
existed earlier in cosmic time, they should have been significantly
dust-obscured to lie beyond the detection limits of current, large-area, deep
near-IR surveys.Comment: 18 pages, 15 figures, 4 tables. Updated to match version in press at
the Ap
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