14,790 research outputs found
Studying the Molecular Ambient towards the Young Stellar Object EGO G35.04-0.47
We are performing a systematic study of the interstellar medium around
extended green objects (EGOs), likely massive young stellar objects driving
outflows. EGO G35.04-0.47 is located towards a dark cloud at the northern-west
edge of an HII region. Recently, H2 jets were discovered towards this source,
mainly towards its southwest, where the H2 1-0 S(1) emission peaks. Therefore,
the source was catalogued as the Molecular Hydrogen emission-line object MHO
2429. In order to study the molecular ambient towards this star-forming site,
we observed a region around the aforementioned EGO using the Atacama
Submillimeter Telescope Experiment in the 12CO J=3--2, 13CO J=3--2, HCO+
J=4--3, and CS J=7--6 lines with an angular and spectral resolution of 22" and
0.11 km s-1, respectively. The observations revealed a molecular clump where
the EGO is embedded at v_LSR ~ 51 km s-1, in coincidence with the velocity of a
Class I 95 GHz methanol maser previously detected. Analyzing the 12CO line we
discovered high velocity molecular gas in the range from 34 to 47 km s-1, most
likely a blueshifted outflow driven by the EGO. The alignment and shape of this
molecular structure coincide with those of the southwest lobe of MHO 2429
mainly between 46 and 47 km s-1, confirming that we are mapping its CO
counterpart. Performing a SED analysis of EGO G35.04-0.47 we found that its
central object should be an intermediate-mass young stellar object accreting
mass at a rate similar to those found in some massive YSOs. We suggest that
this source can become a massive YSO.Comment: accepted to be published in PASJ - 24 September 201
PPAK Wide-field Integral Field Spectroscopy of NGC 628: II. Emission line abundance analysis
In this second paper of the series, we present the 2-dimensional (2D)
emission line abundance analysis of NGC 628, the largest object within the PPAK
Integral Field Spectroscopy (IFS) Nearby Galaxies Survey: PINGS. We introduce
the methodology applied to the 2D IFS data in order to extract and deal with
large spectral samples, from which a 2D abundance analysis can be later
performed. We obtain the most complete and reliable abundance gradient of the
galaxy up-to-date, by using the largest number of spectroscopic points sampled
in the galaxy, and by comparing the statistical significance of different
strong-line metallicity indicators. We find features not previously reported
for this galaxy that imply a multi-modality of the abundance gradient
consistent with a nearly flat-distribution in the innermost regions of the
galaxy, a steep negative gradient along the disc and a shallow gradient or
nearly-constant metallicity beyond the optical edge of the galaxy. The N/O
ratio seems to follow the same radial behaviour. We demonstrate that the
observed dispersion in metallicity shows no systematic dependence with the
spatial position, signal-to-noise or ionization conditions, implying that the
scatter in abundance for a given radius is reflecting a true spatial physical
variation of the oxygen content. Furthermore, by exploiting the 2D IFS data, we
were able to construct the 2D metallicity structure of the galaxy, detecting
regions of metal enhancement, and showing that they vary depending on the
choice of the metallicity estimator. The analysis of axisymmetric variations in
the disc of NGC 628 suggest that the physical conditions and the star formation
history of different-symmetric regions of the galaxy have evolved in a
different manner.Comment: Accepted for publication in MNRAS, 40 pages, 22 figures, online data:
http://www.ast.cam.ac.uk/ioa/research/ping
A view of Large Magellanic Cloud HII regions N159, N132, and N166 through the 345 GHz window
We present results obtained towards the HII regions N159, N166, and N132 from
the emission of several molecular lines in the 345 GHz window. Using ASTE we
mapped a 2.4' 2.4' region towards the molecular cloud N159-W in the
CO J=3-2 line and observed several molecular lines at an IR peak very
close to a massive young stellar object. CO and CO J=3-2 were
observed towards two positions in N166 and one position in N132. The CO
J=3-2 map of the N159-W cloud shows that the molecular peak is shifted
southwest compared to the peak of the IR emission. Towards the IR peak we
detected emission from HCN, HNC, HCO, CH J=4-3, CS J=7-6, and
tentatively CO J=3-2. This is the first reported detection of these
molecular lines in N159-W. The analysis of the CH line yields more
evidence supporting that the chemistry involving this molecular species in
compact and/or UCHII regions in the LMC should be similar to that in Galactic
ones. A non-LTE study of the CO emission suggests the presence of both cool and
warm gas in the analysed region. The same analysis for the CS, HCO, HCN,
and HNC shows that it is very likely that their emissions arise mainly from
warm gas with a density between to some cm. The
obtained HCN/HNC abundance ratio greater than 1 is compatible with warm gas and
with an star-forming scenario. From the analysis of the molecular lines
observed towards N132 and N166 we propose that both regions should have similar
physical conditions, with densities of about 10 cm.Comment: accepted in MNRAS (October 5, 2015
PPAK Wide-field Integral Field Spectroscopy of NGC 628: I. The largest spectroscopic mosaic on a single galaxy
We present a wide-field IFS survey on the nearby face-on Sbc galaxy NGC 628,
comprising 11094 individual spectra, covering a nearly circular field-of-view
of ~6 arcmin in diameter, with a sampling of ~2.7 arcsec per spectrum in the
optical wavelength range (3700--7000 AA). This galaxy is part of the PPAK IFS
Nearby Galaxies Survey, (PINGS, Rosales-Ortega et al. 2009). To our knowledge,
this is the widest spectroscopic survey ever made in a single nearby galaxy. A
detailed flux calibration was applied, granting a spectrophotometric accuracy
of \,0.2 mag.
The age of the stellar populations shows a negative gradient from the inner
(older) to the outer (younger) regions. We found an inversion of this gradient
in the central ~1 kpc region, where a somewhat younger stellar population is
present within a ring at this radius. This structure is associated with a
circumnuclear star-forming region at ~ 500 pc, also found in similar spiral
galaxies. From the study of the integrated and spatially resolved ionized gas
we found a moderate SFR of ~ 2.4 Msun yr. The oxygen abundance shows a a
clear gradient of higher metallicity values from the inner part to the outer
part of the galaxy, with a mean value of 12~+~log(O/H) ~ 8.7. At some specific
regions of the galaxy, the spatially resolved distribution of the physical
properties show some level of structure, suggesting real point-to-point
variations within an individual \hh region. Our results are consistent with an
inside-out growth scheme, with stronger star formation at the outer regions,
and with evolved stellar populations in the inner ones.Comment: 31 pages, 22 Figuras, Accepted for Publishing in MNRAS (corrected
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The Chuacús Metamorphic Complex, central Guatemala : geochronological and geochemical constraints on its Paleozoic - Mesozoic evolution
The Chuacús Metamorphic Complex is located in Central Guatemala, between the Polochic and Motagua fault zones. It is made up of complexly intercalated, mafic and felsic high-grade gneisses, amphibolites, pelitic and quartzofeldsphatic metasediments and subordinate marbles. Mafic dikes and lenses metamorphosed to amphibolite and eclogite facies are tholeiitic and similar to mid-ocean ridge basalts. In contrast, metamorphosed intrusives (gabbro, diorite and granite) are calc-alkaline and have the geochemical signature of arc magmas. Laser Ablation Inductively Coupled Plasma Mass Spectrometry U-Pb zircon geochronology allows the recognition of three episodes of metamorphism. The first eclogite facies metamorphism (M1) is bracketed between Ordovician magmatism in the northern Chuacús Metamorphic Complex and the neighboring Rabinal granitic suite; the second corresponds to an Upper Triassic period of arc magmatism and migmatization (M2); the third high-grade metamorphic event (M3) occurred during the Late Cretaceous. The tectonic evolution of the Chuacús Metamorphic Complex began during the Early Paleozoic as a basin in the Rheic Ocean that received detrital material from the Maya Block, Acatlán and southeastern México. The Chuacús Metamorphic Complex evolved to an active margin that subducted to HP conditions during the Mid- Late Paleozoic, and then was exhumed and involved in two tectonothermal events during the Upper Triassic and Late Cretaceous. The Chuacús Metamorphic Complex was accreted to the southern Maya Block during the Late Cretaceous, as a result of the convergent tectonics between the latter and either the Greater Antillean arc or the ChortÃs Block
ASTE observations in the 345 GHz window towards the HII region N113 of the Large Magellanic Cloud
N113 is an HII region located in the central part of the Large Magellanic
Cloud (LMC) with an associated molecular cloud very rich in molecular species.
Most of the previously observed molecular lines cover the frequency range
85-270 GHz. Thus, a survey and study of lines at the 345 GHz window is required
in order to have a more complete understanding of the chemistry and excitation
conditions of the region. We mapped a region of 2.5' x 2.5' centered at N113
using the Atacama Submillimeter Telescope Experiment in the 13CO J=3-2 line
with an angular and spectral resolution of 22" and 0.11 km/s, respectively. In
addition, we observed 16 molecular lines as single pointings towards its
center. For the molecular cloud associated with N113, from the 13CO J=3-2 map
we estimate LTE and virial masses of about 1x10^4 and 4.5x10^4 M_sun,
respectively. Additionally, from the dust continuum emission at 500 micron we
obtain a mass of gas of 7x10^3 M_sun. Towards the cloud center we detected
emission from: 12CO, 13CO, C18O (3-2), HCN, HNC, HCO+, C2H (4-3), and CS (7-6);
being the first reported detection of HCN, HNC, and C2H (4-3) lines from this
region. The CS (7-6) which was previously tentatively detected is confirmed in
this study. By analyzing the HCN, HNC, and C2H, we suggest that their emission
may arise from a photodissociation region (PDR). Moreover, we suggest that the
chemistry involving the C2H in N113 can be similar to that in Galactic PDRs.
Using the HCN J=4-3, J=3-2, and J=1-0 lines in a RADEX analysis we conclude
that we are observing very high density gas, between some 10^5 and 10^7 cm-3.Comment: accepted for publication in A&A, September 9, 201
A survey on managing users' preferences in ambient intelligence
Understanding the importance of preference management in ambient intelligent environments is key to providing systems that are better prepared to meet users' expectations. This survey provides an account of the various ways that preferences have been handled in Artificial Intelligence. Our analysis indicates that most of those techniques lack the ability to handle ambiguity and the evolution of preferences over time. Further exploration shows that argumentation can provide a feasible solution to complement existing work. We illustrate our claim by using an intelligent environment case study
Cyclic Coverings of genus 2 curves of Sophie Germain type
We consider cyclic unramified coverings of degree d of irreducible complex
smooth genus 2 curves and their corresponding Prym varieties. They provide
natural examples of polarized abelian varieties with automorphisms of order d.
The rich geometry of the associated Prym map, has been studied in several
papers, and the cases d=2, 3, 5, 7 are quite well-understood. Nevertheless,
very few is known for higher values of d. In this article we investigate if the
covering can be reconstructed from its Prym variety, that is, if the generic
Prym Torelli Theorem holds for these coverings. We prove this is so for the
so-called Sophie Germain prime numbers, that is, for prime such that
is also prime. We use results of arithmetic nature on -type
abelian varieties combined with theta-duality techniques
Ethnic variability in the treatment of pain
Ethnicity has been shown to be an important determinant of behavior during illness, particularly when a painful condition is present. Studies have shown that pain may be undertreated among different ethnic groups of patients. Whereas individual variations in the reaction to pain occur, available data do not support racial and/or ethnic differences in the perception of pain, leaving no justification for this discrepancy in treatment. Regardless of ethnicity, inadequate treatment of pain has been known for some time and has been referred to in recent literature as oligoanalgesia. Lack of understanding of different ethnic and cultural groups can lead to inaccurate pain assessment and has been repeatedly shown to result in suboptimal pain control. Additional research is needed to determine the reasons for discrepancies in pain treatment between ethnic groups. The purpose of the present article is to increase awareness among anesthesiologists about ethnic and cultural issues that may influence their assessment and treatment of pain
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