2,228 research outputs found
WISE morphological study of Wolf-Rayet nebulae
We present a morphological study of nebulae around Wolf-Rayet (WR) stars
using archival narrow-band optical and Wide-field Infrared Survey Explorer
(WISE) infrared images. The comparison among WISE images in different bands and
optical images proves to be a very efficient procedure to identify the nebular
emission from WR nebulae, and to disentangle it from that of the ISM material
along the line of sight. In particular, WR nebulae are clearly detected in the
WISE W4 band at 22 m. Analysis of available mid-IR Spitzer spectra shows
that the emission in this band is dominated by thermal emission from dust
spatially coincident with the thin nebular shell or most likely with the
leading edge of the nebula. The WR nebulae in our sample present different
morphologies that we classified into well defined WR bubbles (bubble -type nebulae), clumpy and/or disrupted shells (clumpy/disrupted -type nebulae), and material mixed with the diffuse medium (mixed -type nebulae). The variety of morphologies presented by WR nebulae shows a
loose correlation with the central star spectral type, implying that the
nebular and stellar evolutions are not simple and may proceed according to
different sequences and time-lapses. We report the discovery of an obscured
shell around WR35 only detected in the infrared.Comment: 11 pages, 6 figures, plus 23 appendix figures; to appear in Astronomy
and Astrophysic
Scalar Field Dark Matter: behavior around black holes
We present the numerical evolution of a massive test scalar fields around a
Schwarzschild space-time. We proceed by using hyperboloidal slices that
approach future null infinity, which is the boundary of scalar fields, and also
demand the slices to penetrate the event horizon of the black hole. This
approach allows the scalar field to be accreted by the black hole and to escape
toward future null infinity. We track the evolution of the energy density of
the scalar field, which determines the rate at which the scalar field is being
diluted. We find polynomial decay of the energy density of the scalar field,
and use it to estimate the rate of dilution of the field in time. Our findings
imply that the energy density of the scalar field decreases even five orders of
magnitude in time scales smaller than a year. This implies that if a
supermassive black hole is the Schwarzschild solution, then scalar field dark
matter would be diluted extremely fastComment: 15 pages, 21 eps figures. Appendix added, accepted for publication in
JCA
The IRAM-30m line survey of the Horsehead PDR: III. High abundance of complex (iso-)nitrile molecules in UV-illuminated gas
Complex (iso-)nitrile molecules, such as CH3CN and HC3N, are relatively
easily detected in our Galaxy and in other galaxies. We constrain their
chemistry through observations of two positions in the Horsehead edge: the
photo-dissociation region (PDR) and the dense, cold, and UV-shielded core just
behind it. We systematically searched for lines of CH3CN, HC3N, C3N, and some
of their isomers in our sensitive unbiased line survey at 3, 2, and 1mm. We
derived column densities and abundances through Bayesian analysis using a large
velocity gradient radiative transfer model. We report the first clear detection
of CH3NC at millimeter wavelength. We detected 17 lines of CH3CN at the PDR and
6 at the dense core position, and we resolved its hyperfine structure for 3
lines. We detected 4 lines of HC3N, and C3N is clearly detected at the PDR
position. We computed new electron collisional rate coefficients for CH3CN, and
we found that including electron excitation reduces the derived column density
by 40% at the PDR position. While CH3CN is 30 times more abundant in the PDR
than in the dense core, HC3N has similar abundance at both positions. The
isomeric ratio CH3NC/CH3CN is 0.15+-0.02. In the case of CH3CN, pure gas phase
chemistry cannot reproduce the amount of CH3CN observed in the UV-illuminated
gas. We propose that CH3CN gas phase abundance is enhanced when ice mantles of
grains are destroyed through photo-desorption or thermal-evaporation in PDRs,
and through sputtering in shocks. (abridged)Comment: Accepted for publication in Astronomy & Astrophysic
Agronomic, economic and ecological aspects of the papaya (Carica papaya) production in Tabasco, Mexico
The cultivation of papaya is important in the tropic because it provides source of income to the farmer within a short time. Statistical data were obtained from farmers located in the Chontalpa, Rios and Centro-Sierra regions; the size of the survey was 67 farmers. The study shows the results of the farmers’ problem in a drastic reduction of their productivity because of the virosis and low prices in commercialization. The farmers were classified into three levels of technology, “low”, “middle” and “high”. The first one covers 88% of the farmers in seasonal conditions in contrast with the high technology that concentrates 4.5% in irrigation conditions. According to the technology used, the fertilizer shows more yields. Economically, the high technology had an internal tax return of 0.43 in comparison with the low technology of 0.25, which means that the investment is recovered with different yields. However, the use of high technology makes the system more competitive. Key words
Pillars of creation amongst destruction: Star formation in molecular clouds near R136 in 30 Doradus
New sensitive CO(2-1) observations of the 30 Doradus region in the Large
Magellanic Cloud are presented. We identify a chain of three newly discovered
molecular clouds we name KN1, KN2 and KN3 lying within 2--14 pc in projection
from the young massive cluster R136 in 30 Doradus. Excited H 2.12m
emission is spatially coincident with the molecular clouds, but ionized
Br emission is not. We interpret these observations as the tails of
pillar-like structures whose ionized heads are pointing towards R136. Based on
infrared photometry, we identify a new generation of stars forming within this
structure.Comment: Accepted for publication in ApJ (includes 13 pages, 8 figures). For
higher resolution figures please see
http://www.das.uchile.cl/~vkalari/staplervk.pd
Chemistry of the High-Mass Protostellar Molecular Clump IRAS 16562-3959
We present molecular line observations of the high-mass molecular clump IRAS
165623959 taken at 3 mm using the Atacama Large Millimeter/submillimeter
Array (ALMA) at 1.\!\!^{\prime\prime}7 angular resolution ( pc spatial
resolution). This clump hosts the actively accreting high-mass young stellar
object (HMYSO) G345.4938+01.4677, associated with a hypercompact HII region. We
identify and analyze emission lines from 22 molecular species (encompassing 34
isomers) and classify them into two groups, depending on their spatial
distribution within the clump. One of these groups gathers shock tracers (e.g.,
SiO, SO, HNCO) and species formed in dust grains like methanol (CHOH),
ethenone or ketene (HCCO), and acetaldehyde (CHCHO). The second group
collects species resembling the dust continuum emission morphology and which
are formed mainly in the gas-phase, like hydrocarbons (CCH, c-CH,
CHCCH), cyanopolyynes (HCN and HCN) and cyanides (HCN and
CHCN). Emission from complex organic molecules (COMs) like CHOH,
propanenitrile (CHCHCN), and methoxymethane (CHOCH) arise from
gas in the vicinity of a hot molecular core ( K) associated with
the HMYSO. Other COMs such as propyne (CHCCH), acrylonitrile (CHCHCN),
and acetaldehyde seem to better trace warm ( K) dense gas. In
addition, deuterated ammonia (NHD) is detected mostly in the outskirts of
IRAS 165623959, associated with near-infrared dark globules, probably
gaseous remnants of the clump's prestellar phase. The spatial distribution of
molecules in IRAS 165623959 supports the view that in protostellar clumps,
chemical tracers associated with different evolutionary stages --- starless to
hot cores/HII regions --- exist coevally.Comment: 97 pages, Accepted in The Astrophysical Journal Supplement Series.
Journal file version have better quality figure
The hyperfine structure in the rotational spectrum of CF+
Context. CF+ has recently been detected in the Horsehead and Orion Bar
photo-dissociation regions. The J=1-0 line in the Horsehead is double-peaked in
contrast to other millimeter lines. The origin of this double-peak profile may
be kinematic or spectroscopic. Aims. We investigate the effect of hyperfine
interactions due to the fluorine nucleus in CF+ on the rotational transitions.
Methods. We compute the fluorine spin rotation constant of CF+ using high-level
quantum chemical methods and determine the relative positions and intensities
of each hyperfine component. This information is used to fit the theoretical
hyperfine components to the observed CF+ line profiles, thereby employing the
hyperfine fitting method in GILDAS. Results. The fluorine spin rotation
constant of CF+ is 229.2 kHz. This way, the double-peaked CF+ line profiles are
well fitted by the hyperfine components predicted by the calculations. The
unusually large hyperfine splitting of the CF+ line therefore explains the
shape of the lines detected in the Horsehead nebula, without invoking intricate
kinematics in the UV-illuminated gas.Comment: 2 pages, 1 figure, Accepted for publication in A&
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