2,420 research outputs found
The ionizing sources of luminous compact HII regions in the RCW106 and RCW122 clouds
Given the rarity of young O star candidates, compact HII regions embedded in
dense molecular cores continue to serve as potential sites to peer into the
details of high-mass star formation. To uncover the ionizing sources of the
most luminous and compact HII regions embedded in the RCW106 and RCW122 giant
molecular clouds, known to be relatively nearby (2-4 kpc) and isolated, thus
providing an opportunity to examine spatial scales of a few hundred to a
thousand AU in size. High spatial resolution (0.3"), mid-infrared spectra
(R=350), including the fine structure lines [ArIII] and [NeII], were obtained
for four luminous compact HII regions, embedded inside the dense cores within
the RCW106 and RCW122 molecular cloud complexes. At this resolution, these
targets reveal point-like sources surrounded by nebulosity of different
morphologies, uncovering details at spatial dimensions of <1000AU. The
point-like sources display [ArIII] and [NeII] lines - the ratios of which are
used to estimate the temperature of the embedded sources. The derived
temperatures are indicative of mid-late O type objects for all the sources with
[ArIII] emission. Previously known characteristics of these targets from the
literature, including evidence of disk or accretion suggest that the identified
sources may grow more to become early-type O stars by the end of the star
formation process
Molecular line and continuum study of the W40 cloud
The dense cloud associated with W40, one of the nearby H II regions, has been
studied in millimeter-wave molecular lines and in 1.2 mm continuum. Besides,
1280 MHz and 610 MHz interferometric observations have been done. The cloud has
complex morphological and kinematical structure, including a clumpy dust ring
and an extended dense core. The ring is probably formed by the "collect and
collapse" process due to the expansion of neighboring H II region. Nine dust
clumps in the ring have been deconvolved. Their sizes, masses and peak hydrogen
column densities are: pc, and cm, respectively. Molecular lines are observed
at two different velocities and have different spatial distributions implying
strong chemical differentiation over the region. The CS abundance is enhanced
towards the eastern dust clump 2, while the NH, NH, and
HCO abundances are enhanced towards the western clumps. HCN and
HCO do not correlate with the dust probably tracing the surrounding gas.
Number densities derived towards selected positions are: cm. Two western clumps have kinetic temperatures 21 K and 16 K and
are close to virial equilibrium. The eastern clumps 2 and 3 are more massive,
have higher extent of turbulence and are probably more evolved than the western
ones. They show asymmetric CS(2--1) line profiles due to infalling motions
which is confirmed by model calculations. An interaction between ionized and
neutral material is taking place in the vicinity of the eastern branch of the
ring and probably trigger star formation.Comment: 16 pages, 6 figure
Star formation activity in the southern Galactic HII region G351.63-1.25
The southern Galactic high mass star-forming region, G351.6-1.3, is a HII
region-molecular cloud complex with a luminosity of 2.0 x 10^5 L_sun, located
at a distance of 2.4 kpc. In this paper, we focus on the investigation of the
associated HII region, embedded cluster and the interstellar medium in the
vicinity of G351.6-1.3. We address the identification of exciting source(s) as
well as the census of stellar populations. The ionised gas distribution has
been mapped using the Giant Metrewave Radio Telescope (GMRT), India at three
continuum frequencies: 1280, 610 and 325 MHz. The HII region shows an elongated
morphology and the 1280 MHz map comprises six resolved high density regions
encompassed by diffuse emission spanning 1.4 pc x 1.0 pc. The zero age
main-sequence (ZAMS) spectral type of the brightest radio core is O7.5. We have
carried out near-infrared observations in the JHKs bands using the SIRIUS
instrument on the 1.4 m Infrared Survey Facility (IRSF) telescope. The
near-infrared images reveal the presence of a cluster embedded in nebulous
fan-shaped emission. The log-normal slope of the K-band luminosity function of
the embedded cluster is found to be 0.27 +- 0.03 and the fraction of the
near-infrared excess stars is estimated to be 43%. These indicate that the age
of the cluster is consistent with 1 Myr. The champagne flow model from a flat,
thin molecular cloud is used to explain the morphology of radio emission with
respect to the millimetre cloud and infrared brightness.Comment: 18 pages, 8 figures, To be published in MNRA
Emotional Appraisal : A Computational Perspective
Research on computational modelling of emotions has received significant attention in the last few decades. As such, several computational models of emotions have been proposed which have provided an unprecedented insight into the implications of the emotion theories emerging from cognitive psychology studies. Yet the existing computational models of emotion have distinct limitations namely:(i) low replicability - difficult to implement the given computational model by reading the description of the model, (ii) domain dependence - model only applicable in one or more predefined scenarios or domains, (iii) low scalability and integrability - difficult to use the system in larger or different domains and difficult to integrate the model in wide range of other intelligent systems. In this paper, we propose a completely domain-independent mathematical representation for computational modelling of emotion that provides better replicability and integrability. The implementation of our model is inspired by appraisal theory - an emotion theory which assumes that emotions result from the cognitive evaluation of a situation
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