1,519 research outputs found
NANTEN 12CO (J=1-0) observations around the star WR 55
Context: A complete study of the molecular and ionized gas in the environs of
the nebula RCW 78 around WR 55 is presented. Aims: The aim of this work is to
investigate the spatial distribution, physical characteristics, and kinematical
properties of the molecular gas linked to the galactic nebula RCW 78 to achieve
a better understanding of its interaction with the star and with the ionized
gas. Methods: This study was based on 12CO(1-0) fully sampled observations of a
region of ~0.45{\deg} in size around the star WR 55 and the nebula RCW 78
obtained with the 4-m NANTEN telescope, radio continuum archival data at 1.4
and 4.85 GHz, obtained from SGPS and PMNRAO Southern Radio Survey,
respectively, and available infrared MIPSGAL images at 24 microns. Results: A
molecular gas component in the velocity range from ~ -58 to -45 km s-1,
compatible with the velocity of the ionized gas, was found to be associated
with the optical nebula. Adopting a distance of ~ 5 kpc, the mass of this
molecular component is about 3.4 x 10^4 Msun. The analysis of the molecular
data revealed the presence of a velocity gradient, in agreement with the Halpha
line. New radiocontinuum flux density determinations confirm the thermal nature
of RCW 78. This indicates that the ionized gas in RCW 78 arises from
photoionization of the molecular gas component in the velocity range from -58
km s-1 to -45 km s-1. A molecular concentration at a velocity of -56.1 km s-1
(identified as C1) is very likely associated with the star HD 117797 and with a
collection of candidate YSOs, lying at a distance of 3.9 kpc, while the rest of
the molecular gas at velocities between -56 and -46 km s-1 constitute an
incomplete ring-like structure which expands around WR 55 at a velocity of
about ~ 5 km s-1. Mechanical energy and time requirements indicate that WR 55
is very capable of sustaining the expansion of the nebula.Comment: 14 pages, 10 figures.Accepted for publication in A&
The infrared and molecular environment surrounding the Wolf-Rayet star WR130
We present a study of the molecular CO gas and mid/far infrared radiation
arising from the environment surrounding the Wolf-Rayet (W-R) star 130. We use
the multi-wavelength data to analyze the properties of the dense gas and dust,
and its possible spatial correlation with that of Young Stellar Objects (YSOs).
We use CO J=1-0 data from the FCRAO survey as tracer of the molecular gas, and
mid/far infrared data from the recent WISE and Herschel space surveys to study
the dust continuum radiation and to identify a population of associated
candidate YSOs. The spatial distribution of the molecular gas shows a ring-like
structure very similar to that observed in the HI gas, and over the same
velocity interval. The relative spatial distribution of the HI and CO
components is consistent with a photo-dissociation region. We have identified
and characterized four main and distinct molecular clouds that create this
structure. Cold dust is coincident with the dense gas shown in the CO
measurements. We have found several cYSOs that lie along the regions with the
highest gas column density, and suggest that they are spatially correlated with
the shell. These are indicative of regions of star formation induced by the
strong wind and ionization of the WR star.Comment: 15 pages, 12 figures, 6 Tables. Accepted for publication in MNRA
The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
We present the final data release of observations of lambda 21-cm emission
from Galactic neutral hydrogen over the entire sky, merging the
Leiden/Dwingeloo Survey (LDS: Hartmann & Burton, 1997) of the sky north of
delta = -30 deg with the Instituto Argentino de Radioastronomia Survey (IAR:
Arnal et al., 2000, and Bajaja et al., 2005) of the sky south of delta = -25
deg. The angular resolution of the combined material is HPBW ~ 0.6 deg. The LSR
velocity coverage spans the interval -450 km/s to +400 km/s, at a resolution of
1.3 km/s. The data were corrected for stray radiation at the Institute for
Radioastronomy of the University of Bonn, refining the original correction
applied to the LDS. The rms brightness-temperature noise of the merged database
is 0.07 - 0.09 K. Residual errors in the profile wings due to defects in the
correction for stray radiation are for most of the data below a level of 20 -
40 mK. It would be necessary to construct a telescope with a main beam
efficiency of eta_{MB} > 99% to achieve the same accuracy. The merged and
refined material entering the LAB Survey of Galactic HI is intended to be a
general resource useful to a wide range of studies of the physical and
structural characteristices of the Galactic interstellar environment. The LAB
Survey is the most sensitive Milky Way HI survey to date, with the most
extensive coverage both spatially and kinematically.Comment: 9 pages, 5 figures, accepted for publication by Astronomy &
Astrophysic
Analysis of the application of Socrative as a tool for the learning improvement in a subject of Experimentation in Chemical Engineering
[EN] Experimentation in Chemical Engineering III is a compulsory subject of the third course, semester B of the Chemical Engineering Degree at the Universitat Politècnica de València. It is the last experimental subject of the degree, and the methodology applied is "Project Oriented Learning" (POL). Students carry out experimental sessions, obtaining data that they later use to design an industrial installation based on the laboratory equipment but at a large scale. The course is assesed through the design project and a laboratory report of each experimental session, which is corrected by the teacher and then used as study material for the exam.
Although the development of the subject is satisfactory, the teachers do not know the level that the students have about the experiment to be developed at the beginning of the experimental session and, in most of the cases, mistakes or errors of interpretation that they have had during the practice are detected during correction of the report. Therefore, last year teachers decided to introduce the use of the Socrative tool to conduct surveys to students at the beginning and the end of each session, in order to have real-time feedback on the points that should be most emphasized during the practice, as well as the degree of improvement achieved after the session. Socrative allows to carry out surveys in a simple way through the mobile phone, and to know at the same time the results of the assessment. Thus, students know their mistakes in the test before starting the experimental session, which also is useful to them to assess their level about the topic to develop and pay attention to find out those questions asked in the test in which they have obtained worse results.
This work describes the implementation of this teaching innovation in the laboratory, as well as the results obtained and the degree of improvement achieved by comparing the results at the beginning and end of each experimental session. Finally, it is analysed the usefulness of the innovation, as well as the necessary improvements to continue its application in the future academic courses.GarcĂa-Fayos, B.; Sancho, M.; Arnal Arnal, JM.; Zuriaga Agusti, E.; LĂłpez-Hernández, I. (2021). Analysis of the application of Socrative as a tool for the learning improvement in a subject of Experimentation in Chemical Engineering. IATED. 3727-3733. https://doi.org/10.21125/inted.2021.0773S3727373
Ultrarobust calibration of an optical lattice depth based on a phase shift
We report on a new method to calibrate the depth of an optical lattice. It
consists in triggering the intrasite dipole mode of the cloud by a sudden phase
shift. The corresponding oscillatory motion is directly related to the
intraband frequencies on a large range of lattice depths. Remarkably, for a
moderate displacement, a single frequency dominates this oscillation for the
zeroth and first order interference pattern observed after a sufficiently long
time-of-flight. The method is robust against atom-atom interactions and the
exact value of the extra external confinement of the initial trapping
potential.Comment: 7 pages, 6 figure
Automatic Detection of Expanding HI Shells Using Artificial Neural Networks
The identification of expanding HI shells is difficult because of their
variable morphological characteristics. The detection of HI bubbles on a global
scale therefore never has been attempted. In this paper, an automatic detector
for expanding HI shells is presented. The detection is based on the more stable
dynamical characteristics of expanding shells and is performed in two stages.
The first one is the recognition of the dynamical signature of an expanding
bubble in the velocity spectra, based on the classification of an artificial
neural network. The pixels associated with these recognized spectra are
identified on each velocity channel. The second stage consists in looking for
concentrations of those pixels that were firstly pointed out, and to decide if
they are potential detections by morphological and 21-cm emission variation
considerations. Two test bubbles are correctly detected and a potentially new
case of shell that is visually very convincing is discovered. About 0.6% of the
surveyed pixels are identified as part of a bubble. These may be false
detections, but still constitute regions of space with high probability of
finding an expanding shell. The subsequent search field is thus significantly
reduced. We intend to conduct in the near future a large scale HI shells
detection over the Perseus Arm using our detector.Comment: 39 pages, 11 figures, accepted by PAS
HII Shells Surrounding Wolf-Rayet stars in M31
We present the results of an ongoing investigation to provide a detailed view
of the processes by which massive stars shape the surrounding interstellar
medium (ISM), from pc to kpc scales. In this paper we have focused on studying
the environments of Wolf-Rayet (WR) stars in M31 to find evidence for WR
wind-ISM interactions, through imaging ionized hydrogen nebulae surrounding
these stars.
We have conducted a systematic survey for HII shells surrounding 48 of the 49
known WR stars in M31. There are 17 WR stars surrounded by single shells, or
shell fragments, 7 stars surrounded by concentric limb brightened shells, 20
stars where there is no clear physical association of the star with nearby
H-alpha emission, and 4 stars which lack nearby H-alpha emission. For the 17+7
shells above, there are 12 which contain one or two massive stars (including a
WR star) and that are <=40 pc in radius. These 12 shells may be classical WR
ejecta or wind-blown shells. Further, there may be excess H-alpha point source
emission associated with one of the 12 WR stars surrounded by putative ejecta
or wind-blown shells. There is also evidence for excess point source emission
associated with 11 other WR stars. The excess emission may arise from
unresolved circumstellar shells, or within the extended outer envelopes of the
stars themselves.
In a few cases we find clear morphological evidence for WR shells interacting
with each other. In several H-alpha images we see WR winds disrupting, or
punching through, the walls of limb-brightened HII shells.Comment: 20 pages, 4 figures (in several parts: some .jpg and others .ps),
accepted to AJ (appearing Oct, 1999
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