1,316 research outputs found
Star formation around mid-infrared bubble N37: Evidence of cloud-cloud collision
We have performed a multi-wavelength analysis of a mid-infrared (MIR) bubble
N37 and its surrounding environment. The selected 1515 area around
the bubble contains two molecular clouds (N37 cloud; V37-43 km
s, and C25.29+0.31; V43-48 km s) along the line of
sight. A total of seven OB stars are identified towards the bubble N37 using
photometric criteria, and two of them are spectroscopically confirmed as O9V
and B0V stars. Spectro-photometric distances of these two sources confirm their
physical association with the bubble. The O9V star is appeared to be the
primary ionizing source of the region, which is also in agreement with the
desired Lyman continuum flux analysis estimated from the 20 cm data. The
presence of the expanding HII region is revealed in the N37 cloud which could
be responsible for the MIR bubble. Using the CO line data and
photometric data, several cold molecular condensations as well as clusters of
young stellar objects (YSOs) are identified in the N37 cloud, revealing ongoing
star formation (SF) activities. However, the analysis of ages of YSOs and the
dynamical age of the HII region do not support the origin of SF due to the
influence of OB stars. The position-velocity analysis of CO data reveals
that two molecular clouds are inter-connected by a bridge-like structure,
favoring the onset of a cloud-cloud collision process. The SF activities (i.e.
the formation of YSOs clusters and OB stars) in the N37 cloud are possibly
influenced by the cloud-cloud collision.Comment: 18 pages, 13 figures, 2 tables, Accepted for publication in the Ap
Multi-wavelength study of the star-formation in the S237 H II region
We present a detailed multi-wavelength study of observations from X-ray,
near-infrared to centimeter wavelengths to probe the star formation processes
in the S237 region. Multi-wavelength images trace an almost sphere-like shell
morphology of the region, which is filled with the 0.5--2 keV X-ray emission.
The region contains two distinct environments - a bell-shaped cavity-like
structure containing the peak of 1.4 GHz emission at center, and elongated
filamentary features without any radio detection at edges of the sphere-like
shell - where {\it Herschel} clumps are detected. Using the 1.4 GHz continuum
and CO line data, the S237 region is found to be excited by a radio
spectral type of B0.5V star and is associated with an expanding H{\sc ii}
region. The photoionized gas appears to be responsible for the origin of the
bell-shaped structure. The majority of molecular gas is distributed toward a
massive {\it Herschel} clump (M 260 M), which
contains the filamentary features and has a noticeable velocity gradient. The
photometric analysis traces the clusters of young stellar objects (YSOs) mainly
toward the bell-shaped structure and the filamentary features. Considering the
lower dynamical age of the H\,{\sc ii} region (i.e. 0.2-0.8 Myr), these
clusters are unlikely to be formed by the expansion of the H\,{\sc ii} region.
Our results also show the existence of a cluster of YSOs and a massive clump at
the intersection of filamentary features, indicating that the collisions of
these features may have triggered cluster formation, similar to those found in
Serpens South region.Comment: 21 pages, 14 figures, 1 table, Accepted for publication in The
Astrophysical Journa
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
Proximity-induced supercurrent through topological insulator based nanowires for quantum computation studies
Proximity induced superconducting energy gap in the surface states of
topological insulators has been predicted to host the much wanted Majorana
fermions for fault tolerant quantum computation. Recent theoretically proposed
architectures for topological quantum computation via Majoranas are based on
large networks of Kitaevs one dimensional quantum wires, which pose a huge
experimental challenge in terms of scalability of the current single nanowire
based devices. Here, we address this problem by realizing robust
superconductivity in junctions of fabricated topological insulator Bi2Se3
nanowires proximity coupled to conventional s wave superconducting W
electrodes. Milling technique possesses great potential in fabrication of any
desired shapes and structures at nanoscale level, and therefore can be
effectively utilized to scale up the existing single nanowire based design into
nanowire based network architectures. We demonstrate the dominant role of
ballistic topological surface states in propagating the long range proximity
induced superconducting order with high IcRN product in long Bi2Se3 junctions.
Large upper critical magnetic fields exceeding the Chandrasekhar Clogston limit
suggests the existence of robust superconducting order with spin triplet cooper
pairing. An unconventional inverse dependence of IcRN product on the width of
the nanowire junction was also observed.Comment: 12 page
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