921 research outputs found
Interstellar Extinction Law toward the Galactic Center II: V, J, H, and Ks Bands
We have determined the ratios of total to selective extinction directly from
observations in the optical V band and near-infrared J band toward the Galactic
center. The OGLE (Optical Gravitational Lensing Experiment) Galactic bulge
fields have been observed with the SIRIUS camera on the IRSF telescope, and we
obtain A(V)/E(V-J)=1.251+-0.014 and A(J)/E(V-J)=0.225+-0.007. From these
ratios, we have derived A(J)/A(V) = 0.188+-0.005; if we combine A(J)/A(V) with
the near-infrared extinction ratios obtained by Nishiyama et al. for more
reddened fields near the Galactic center, we get A(V) : A(J) : A(H) : A(Ks) = 1
: 0.188 : 0.108 : 0.062, which implies steeply declining extinction toward the
longer wavelengths. In particular, it is striking that the Ks band extinction
is \approx 1/16 of the visual extinction A(V) much smaller than one tenth of
A(V) so far employed.Comment: 8 pages, 7 figures, Accepted for publication in Ap
Phase transitions in crowd dynamics of resource allocation
We define and study a class of resources allocation processes where
agents, by repeatedly visiting resources, try to converge to optimal
configuration where each resource is occupied by at most one agent. The process
exhibits a phase transition, as the density of agents grows, from an
absorbing to an active phase. In the latter, even if the number of resources is
in principle enough for all agents (), the system never settles to a
frozen configuration. We recast these processes in terms of zero-range
interacting particles, studying analytically the mean field dynamics and
investigating numerically the phase transition in finite dimensions. We find a
good agreement with the critical exponents of the stochastic fixed-energy
sandpile. The lack of coordination in the active phase also leads to a
non-trivial faster-is-slower effect.Comment: 7 pages, 7 fig
Wide-Field Infrared Imaging Polarimetry of the NGC 6334 Region: A Nest of Infrared Reflection Nebulae
We report the detection of eighteen infrared reflection nebulae (IRNe) in the
, , & linear polarimetric observations of the NGC 6334 massive
star-formation complex, of which 16 IRNe are new discoveries. Our images cover
180 square arcminutes, one of the widest near-infrared polarization data
in star-formation regions so far. These IRNe are most likely associated with
embedded young OB stars at different evolutionary phases, showing a variety of
sizes, morphologies, and polarization properties, which can be divided into
four categories. We argue the different nebula characteristics to be a possible
evolutionary sequence of circumstellar structures around young massive stars.Comment: 4 pages, 1 figur
Strategy abundance in 2x2 games for arbitrary mutation rates
We study evolutionary game dynamics in a well-mixed populations of finite
size, N. A well-mixed population means that any two individuals are equally
likely to interact. In particular we consider the average abundances of two
strategies, A and B, under mutation and selection. The game dynamical
interaction between the two strategies is given by the 2x2 payoff matrix
[(a,b), (c,d)]. It has previously been shown that A is more abundant than B, if
(N-2)a+Nb>Nc+(N-2)d. This result has been derived for particular stochastic
processes that operate either in the limit of asymptotically small mutation
rates or in the limit of weak selection. Here we show that this result holds in
fact for a wide class of stochastic birth-death processes for arbitrary
mutation rate and for any intensity of selection.Comment: version 2 is the final published version that contains minor changes
in response to referee comment
Viable tax constitutions
Taxation is only sustainable if the general public complies with it. This observation is uncontroversial with tax practitioners but has been ignored by the public finance tradition, which has interpreted tax constitutions as binding contracts by which the power to tax is irretrievably conferred by individuals to government, which can then levy any tax it chooses. However, in the absence of an outside party enforcing contracts between members of a group, no arrangement within groups can be considered to be a binding contract, and therefore the power of tax must be sanctioned by individuals on an ongoing basis. In this paper we offer, for the first time, a theoretical analysis of this fundamental compliance problem associated with taxation, obtaining predictions that in some cases point to a re-interptretation of the theoretical constructions of the public finance tradition while in others call them into question
Five-Year Optical and Near Infrared Observations of the Extremely Slow Nova V1280 Scorpii
We present optical (, , , and ) and near
infrared (, and ) photometric and spectroscopic observations
of a classical nova V1280 Scorpii for five years from 2007 to 2011. Our
photometric observations show a declining event in optical bands shortly after
the maximum light which continues 250 days. The event is most probably
caused by a dust formation. The event is accompanied by a short ( 30
days) re-brightening episode ( 2.5 mag in ), which suggests a
re-ignition of the surface nuclear burning. After 2008, the band
observations show a very long plateau at around = 10.5 for more than 1000
days until April 2011 ( 1500 days after the maximum light). The nova had
taken a very long time ( 50 months) before entering the nebular phase
(clear detection of both [\ion{O}{iii}] 4959 and 5007) and is still continuing
to generate the wind caused by H-burning. The finding suggests that V1280 Sco
is going through the historically slowest evolution. The interval from the
maximum light (2007 February 16) to the beginning of the nebular phase is
longer than any previously known slow novae: V723 Cas (18 months), RR Pic (10
months), or HR Del (8 months). It suggests that the mass of a white dwarf in
the V1280 Sco system might be 0.6 M_\mathrm{\sun} or smaller. The distance,
based on our measurements of the expansion velocity combined with the directly
measured size of the dust shell, is estimated to be 1.1 0.5 kpc.Comment: 17 pages, 14 figures, accepted for publication in A&
A 2MASS Analysis of the Stability of Southern Bok Globules
We used near-infrared 2MASS data to construct visual extinction maps of a
sample of Southern Bok globules utilizing the NICE method. We derived radial
extinction profiles of dense cores identified in the globules and analyzed
their stability against gravitational collapse with isothermal Bonnor-Ebert
spheres. The frequency distribution of the stability parameter xi_max of these
cores shows that a large number of them are located in stable states, followed
by an abrupt decrease of cores in unstable states. This decrease is steeper for
globules with associated IRAS point sources than for starless globules.
Moreover, globules in stable states have a Bonnor-Ebert temperature of T = 15
+- 6 K, while the group of critical plus unstable globules has a different
temperature of T = 10 +- 3 K. Distances were estimated to all the globules
studied in this work and the spectral class of the IRAS sources was calculated.
No variations were found in the stability parameters of the cores and the
spectral class of their associated IRAS sources. On the basis of 13CO J = 1-0
molecular line observations, we identified and modeled a blue-assymetric line
profile toward a globule of the sample, obtaining an upper limit infall speed
of 0.25 km/s.Comment: 53 pages, 15 figures, accepted for publication in Ap
AKARI observations of ice absorption bands towards edge-on YSOs
To investigate the composition and evolution of circumstellar ice around
low-mass YSOs, we observed ice absorption bands in the near infrared (NIR)
towards eight YSOs ranging from class 0 to class II, among which seven are
associated with edge-on disks. We performed slit-less spectroscopic
observations using the grism mode of the Infrared Camera (IRC) on board AKARI,
which enables us to obtain full NIR spectra from 2.5 m to 5 m. The
spectra were fitted with polynomial baselines to derive the absorption spectra.
The molecular absorption bands were then fitted with the laboratory database of
ice absorption bands, considering the instrumental line profile and the
spectral resolution of the grism dispersion element. Towards the class 0-I
sources (L1527, IRC-L1041-2, and IRAS04302), absorption bands of HO,
CO, CO, and XCN are clearly detected. Column density ratios of CO ice
and CO ice relative to HO ice are 21-28% and 13-46%, respectively. If XCN
is OCN, its column density is as high as 2-6% relative to HO ice. The
HDO ice feature at 4.1 m is tentatively detected towards the class 0-I
sources and HV Tau. Non-detections of the CH-stretching mode features around
3.5 m provide upper limits to the CHOH abundance of 26% (L1527) and
42% (IRAS04302) relative to HO. We tentatively detect OCS ice absorption
towards IRC-L1041-2. Towards class 0-I sources, the detected features should
mostly originate in the cold envelope, while CO gas and OCN could originate
in the region close to the protostar, where there are warm temperatures and UV
radiation. We detect HO ice band towards ASR41 and 2MASSJ1628137-243139,
which are edge-on class II disks. We also detect HO ice and CO ice
towards HV Tau, HK Tau, and UY Aur, and tentatively detect CO gas features
towards HK Tau and UY Aur.Comment: Accepted to A&
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