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Soam, A.,Kwon, Jugmi,Maheswar, G.,Tamura, Motohide,Lee, Chang Won IOP Publishing 2015 ASTROPHYSICAL JOURNAL LETTERS - Vol.803 No.2
<P>LDN 328 is cited as an example of a fairly isolated clump contracting to form multiple sub-cores, possibly through gravitational fragmentation. In one of these sub-cores, a proto-brown dwarf (L328-IRS) candidate is in the process of formation through the self-gravitating contraction, similar to the formation scenario of a low-mass star. We present results of our optical and near-infrared polarization observations of regions toward LDN 328. This is the first observational attempt to map the magnetic field geometry of a cloud harboring a proto-brown dwarf candidate associated with a sub-parsec-scale molecular outflow. On a parsec scale, the magnetic field is found to follow the curved structure of the cloud showing a head-tail morphology. The magnetic field is found to be well ordered over a 0.02-0.2 pc scale around L328-IRS. Taking into account the uncertainties in the determination of position angles, the projected angular offset between the magnetic field direction and the outflow axis is found to be in the range of 0 degrees-70 degrees. Considering outflow to be the proxy for the rotation axis, the result obtained in this study implies that the rotation axis in L328 is preferably parallel to the local magnetic field. The magnetic field strength estimated in the close vicinity of L328-IRS is similar to 20 mu G. Results from the present study suggest that the magnetic field may be playing a vital role even in the cores that are forming sub-stellar sources.</P>
Magnetic Fields toward Ophiuchus-B Derived from SCUBA-2 Polarization Measurements
Soam, Archana,Pattle, Kate,Ward-Thompson, Derek,Lee, Chang Won,Sadavoy, Sarah,Koch, Patrick M.,Kim, Gwanjeong,Kwon, Jungmi,Kwon, Woojin,Arzoumanian, Doris,Berry, David,Hoang, Thiem,Tamura, Motohide,Le American Astronomical Society 2018 The Astrophysical journal Vol.861 No.1
<P>We present the results of dust emission polarization measurements of Ophiuchus-B (Oph-B) carried out using the Submillimetre Common-User Bolometer Array 2 (SCUBA-2) camera with its associated polarimeter (POL-2) on the James Clerk Maxwell Telescope in Hawaii. This work is part of the B-fields in Star-forming Region Observations survey initiated to understand the role of magnetic fields in star formation for nearby star-forming molecular clouds. We present a first look at the geometry and strength of magnetic fields in Oph-B. The field geometry is traced over similar to 0.2 pc, with clear detection of both of the sub-clumps of Oph-B. The field pattern appears significantly disordered in sub-clump Oph-B1. The field geometry in Oph-B2 is more ordered, with a tendency to be along the major axis of the clump, parallel to the filamentary structure within which it lies. The degree of polarization decreases systematically toward the dense core material in the two sub-clumps. The field lines in the lower density material along the periphery are smoothly joined to the large-scale magnetic fields probed by NIR polarization observations. We estimated a magnetic field strength of 630 +/- 410 mu G in the Oph-B2 sub-clump using a Davis-Chandrasekhar-Fermi analysis. With this magnetic field strength, we find a mass-to-flux ratio lambda = 1.6 +/- 1.1, which suggests that the Oph-B2 clump is slightly magnetically supercritical.</P>
Magnetic fields in cometary globules – IV. LBN 437
Soam, A.,Maheswar, G.,Bhatt, H. C.,Lee, C. W.,Ramaprakash, A. N. Oxford University Press 2013 Monthly notices of the Royal Astronomical Society Vol.432 No.2
<P>We present results of our R-band polarimetry of a cometary globule, LBN 437 (Gal 96-15, l = 96 degrees, b = -15 degrees), to study the magnetic field geometry of the cloud. We estimated a distance of 360 +/- 65 pc to LBN 437 (also one additional cloud, CB 238) using a near-IR photometric method. The foreground contribution to the observed polarization values was subtracted by making polarimetric observations of stars that are located in the direction of the cloud and with known distances from the Hipparcos parallax measurements. The magnetic field geometry of LBN 437 is found to follow the curved shape of the globule head. This could be due to the drag that the magnetic field lines could have experienced because of the ionization radiation from the same exciting source that caused the cometary shape of the cloud. The orientation of the outflow from the Herbig A4e star, LkH alpha 233 (or V375 Lac), located at the head of LBN 437, is found to be parallel to both the initial (prior to the ionizing source was turned on) ambient magnetic field (inferred from a star HD 214243 located just in front of the cloud) and the Galactic plane.</P>
SOAM, ARCHANA,GOPINATHAN, MAHESWAR,LEE, CHANG WON,BHATT, HRISH The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2
We present results of our R-band polarimetry of a bright-rimmed cloud, IC1396A (with BRC 36), associated with the H II region S131 and the cometary globule LDN 1616 to study their magnetic field geometry. The distances of these clouds have been reported to be ~ 750 pc and ~ 450 pc, respectively in the literature. The young open cluster Trumpler 37 in the vicinity of IC1396A and the high mass stars in the Orion belt near L1616 are found to be responsible for the structure of these clouds. We made polarimetry of foreground stars inferred from their distances measured by the Hipparcos satellite to subtract the foreground contribution to the observed polarization results. We discuss the optical polarimetric results and compare our findings with MHD simulations towards BRCs and CGs.
Ankur Soam,Pravin Kavle,Alka Kumbhar,Rajiv O. Dusane 한국물리학회 2017 Current Applied Physics Vol.17 No.2
Fabrication of high performance micro-supercapacitor (m-SC) based on Silicon nanowires (SiNWs) at low temperatures by simple, effective and a scalable technique is always desired. In this regard, the performance of the m-SC was greatly improved by employing a novel architecture developed by coating SiNWs with Graphene (rGO) in the present work. This coating of Graphene was deposited by an easy and efficient technique, Electrophoretic Deposition (EPD), at the room temperature with no intricate steps. These rGO coated SiNWs electrodes show as much as four times larger capacitance (240 mF/cm2) than the bare SiNWs (60 mF/cm2). Moreover, the key advantage of the architecture is that both rGO and SiNWs structurally complement each other enhancing the electrode performance - EPD deposited rGO fills the empty space between SiNWs by making a bridge type structure, increasing the surface area of the electrodes whereas SiNWs prevent restacking and aggregation of the rGO nano-sheets and also provide support to rGO nano-sheets to stand vertically over the substrate. One more notable bonus of using EPD technique is that the wires are selectively coated. SiNWs were synthesized at a temperature of 320 C by the Hot-wire assisted SiNW growth technique and deposition of Graphene oxide (GO) and its reduction into reduced Graphene oxide (rGO) was carried out at the room temperature. The results suggest that rGO coated SiNWs could be a promising candidate as an electrode for on-chip integrable m-SC application.