The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform
Xiang-yu Wang - One of the best experts on this subject based on the ideXlab platform.
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Diffuse γ-ray emission from the vicinity of young massive star cluster RSGC 1
Monthly Notices of the Royal Astronomical Society, 2020Co-Authors: Xiao-na Sun, Rui-zhi Yang, Xiang-yu WangAbstract:We report the Fermi Large Area Telescope (Fermi-LAT) detection of the gamma-ray emission towards the young massive star cluster RSGC 1. Using the latest source catalog and diffuse background models, we found that the diffuse gamma-ray emission in this region can be resolved into three different components. The GeV gamma-ray emission from the region HESS J1837-069 has a photon index of 1.83 $\pm$ 0.08. Combining with the HESS and MAGIC data, we argue that the gamma-ray emission in this region likely originate from a pulsar wind nebula (PWN). The gamma-ray emission from the northwest part (region A) can be modelled by an ellipse with the semimajor and Semiminor Axis of 0.5$^{\circ}$ and 0.25$^{\circ}$, respectively. The GeV emission has a hard spectrum with a photon index of 2.05 $\pm$ 0.02 and is partially coincide with the TeV source MAGIC J1835-069. The possible origin of the gamma-ray emission in this region is the interaction of the cosmic rays (CRs) accelerated by SNR G24.7+0.6 or/and the OB cluster G25.18+0.26 with the surrounding gas clouds. The GeV gamma-ray emission from the southeast region (region B) can be modeled as an ellipse with the semimajor and Semiminor Axis of 0.9$^{\circ}$ and 0.5$^{\circ}$, respectively, and also reveals a hard gamma-ray spectrum. We argue that the most probable origin is the interaction of the accelerated protons in the young massive star cluster RSGC 1 with ambient gas clouds, and the total cosmic-ray (CR) proton energy is estimated to be as high as $\sim$ 1x10$^{50}$ erg.
Xiao-na Sun - One of the best experts on this subject based on the ideXlab platform.
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Diffuse γ-ray emission from the vicinity of young massive star cluster RSGC 1
Monthly Notices of the Royal Astronomical Society, 2020Co-Authors: Xiao-na Sun, Rui-zhi Yang, Xiang-yu WangAbstract:We report the Fermi Large Area Telescope (Fermi-LAT) detection of the gamma-ray emission towards the young massive star cluster RSGC 1. Using the latest source catalog and diffuse background models, we found that the diffuse gamma-ray emission in this region can be resolved into three different components. The GeV gamma-ray emission from the region HESS J1837-069 has a photon index of 1.83 $\pm$ 0.08. Combining with the HESS and MAGIC data, we argue that the gamma-ray emission in this region likely originate from a pulsar wind nebula (PWN). The gamma-ray emission from the northwest part (region A) can be modelled by an ellipse with the semimajor and Semiminor Axis of 0.5$^{\circ}$ and 0.25$^{\circ}$, respectively. The GeV emission has a hard spectrum with a photon index of 2.05 $\pm$ 0.02 and is partially coincide with the TeV source MAGIC J1835-069. The possible origin of the gamma-ray emission in this region is the interaction of the cosmic rays (CRs) accelerated by SNR G24.7+0.6 or/and the OB cluster G25.18+0.26 with the surrounding gas clouds. The GeV gamma-ray emission from the southeast region (region B) can be modeled as an ellipse with the semimajor and Semiminor Axis of 0.9$^{\circ}$ and 0.5$^{\circ}$, respectively, and also reveals a hard gamma-ray spectrum. We argue that the most probable origin is the interaction of the accelerated protons in the young massive star cluster RSGC 1 with ambient gas clouds, and the total cosmic-ray (CR) proton energy is estimated to be as high as $\sim$ 1x10$^{50}$ erg.
Jayanta Haldar - One of the best experts on this subject based on the ideXlab platform.
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Aggregation Properties of Amide Bearing Cleavable Gemini Surfactants by Small Angle Neutron Scattering and Conductivity Studies
2016Co-Authors: Jiaul Hoque, Pratik Kumar, Vinod K. Aswal, Jayanta HaldarAbstract:The micellar aggregation of different amide bearing cleavable gemini surfactants with varying methylene spacer chain length (m = 2, 4, 6, 8, and 12) along with the corresponding monomeric surfactant in aqueous media has been investigated by conductometric and small angle neutron scattering (SANS) studies. The critical micellar concentration (CMC) values of gemini surfactants were found to be very low (CMC = 0.08–0.19 mM) and were 23–55 times lesser than the corresponding monomeric analogue (CMC = 4.4 mM). With increase in the spacer chain length, CMC was found to decrease whereas the degree of ionization was found to increase. SANS data have been analyzed by considering the screened Coulombic interactions between the micelles to compute the interparticle structure factor S(Q). The extent of micellar growth and the variation of shapes of the micelles formed by these new surfactants in aqueous solution have been found to depend strongly on the spacer chain length. It was observed that the extent of micellar growth and variation of micellar shapes are more pronounced for surfactants with short spacer chain length (m ≤ 4), whereas the surfactants with a long spacer chain length (m ≥ 6) showed slight variation of these properties in aqueous solution. The effects of the variation of the concentration and temperature on the SANS spectra (and hence on the microstructure) of the gemini surfactant (m = 4) were also examined. With an increase in concentration the aggregation number (N) and size of the micelles (the ratio of semimajor Axis (a) to Semiminor Axis (b = c)) increased whereas opposite phenomena was observed with an increase in temperature
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Aggregation Properties of Amide Bearing Cleavable Gemini Surfactants by Small Angle Neutron Scattering and Conductivity Studies B
The Journal of Physical Chemistry, 2012Co-Authors: Jiaul Hoque, Vinod K. Aswal, Pratik Kumar, Jayanta HaldarAbstract:The micellar aggregation of different amide bearing cleavable gemini surfactants with varying methylene spacer chain length (m = 2, 4, 6, 8, and 12) along with the corresponding monomeric surfactant in aqueous media has been investigated by conductometric and small angle neutron scattering (SANS) studies. The critical micellar concentration (CMC) values of gemini surfactants were found to be very low (CMC = 0.08–0.19 mM) and were 23–55 times lesser than the corresponding monomeric analogue (CMC = 4.4 mM). With increase in the spacer chain length, CMC was found to decrease whereas the degree of ionization was found to increase. SANS data have been analyzed by considering the screened Coulombic interactions between the micelles to compute the interparticle structure factor S(Q). The extent of micellar growth and the variation of shapes of the micelles formed by these new surfactants in aqueous solution have been found to depend strongly on the spacer chain length. It was observed that the extent of micellar growth and variation of micellar shapes are more pronounced for surfactants with short spacer chain length (m ≤ 4), whereas the surfactants with a long spacer chain length (m ≥ 6) showed slight variation of these properties in aqueous solution. The effects of the variation of the concentration and temperature on the SANS spectra (and hence on the microstructure) of the gemini surfactant (m = 4) were also examined. With an increase in concentration the aggregation number (N) and size of the micelles (the ratio of semimajor Axis (a) to Semiminor Axis (b = c)) increased whereas opposite phenomena was observed with an increase in temperature.
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Unusual micellar properties of multiheaded cationic surfactants in the presence of strong charge neutralizing salts
Journal of colloid and interface science, 2005Co-Authors: Jayanta Haldar, Vinod K. Aswal, Prem S. Goyal, Santanu BhattacharyaAbstract:The aggregation properties of single-chain surfactants bearing one (H1), two (H2), and three (H3) trimethylammonium head groups have been studied by small-angle neutron scattering (SANS). Growth of aggregates was observed to decrease dramatically with an increase in the number of head groups in the surfactants. The micelles grow progressively smaller with every increase in the number of head groups of the surfactants. Aggregation number (N) continuously decreases and the fractional charge (α) gradually increases with the increase in the number of head groups. The Semiminor Axis (a) and semimajor Axis (b=c) of the micelle decrease strongly with the increase in the number of head groups. In the case of H1, dramatic micellar growth is observed on addition of salts such as KBr and sodium salicylate, but this type of micellar growth is not observed in the cases of H2 and H3 when the above salts are added to their micellar solutions. Aggregation number and size of the micelles remain almost the same, even after addition of KBr at a concentration as high as 100 mM. This observation with multiheaded cationic surfactants is unusual. Clearly, the charge density at the head group level of surfactants markedly influences their micellar aggregation properties.
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Small-angle neutron scattering study of aggregate structures of multi-headed pyridinium surfactants in aqueous solution
Pramana, 2004Co-Authors: Jayanta Haldar, Vinod K. Aswal, Prem S. Goyal, Santanu BhattacharyaAbstract:The aggregate structures of a set of novel single-chain surfactants bearing one, two and three pyridinium headgroups have been studied using small-angle neutron scattering (SANS). It is found that the nature of aggregate structures of these cationic surfactants depend on the number of headgroups present in the surfactants. The single-headed pyridinium surfactant forms the lamellar structure, whereas surfactants with double and triple headgroups form micelles in water. The aggregates shrink in size with increase in the number of headgroups in the surfactants. The aggregation number (N) continually decreases and the fractional charge (α) increases with more number of headgroups on the surfactants. The semimajor Axis (a) and Semiminor Axis (b = c) of the micelle also decrease with the increase in the number of headgroups in the surfactants. This indicates that hydrocarbon chains in such micelles prepared from multiheaded surfactants adopt bent conformation and no longer stay in extended conformation.
Rui-zhi Yang - One of the best experts on this subject based on the ideXlab platform.
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Diffuse γ-ray emission from the vicinity of young massive star cluster RSGC 1
Monthly Notices of the Royal Astronomical Society, 2020Co-Authors: Xiao-na Sun, Rui-zhi Yang, Xiang-yu WangAbstract:We report the Fermi Large Area Telescope (Fermi-LAT) detection of the gamma-ray emission towards the young massive star cluster RSGC 1. Using the latest source catalog and diffuse background models, we found that the diffuse gamma-ray emission in this region can be resolved into three different components. The GeV gamma-ray emission from the region HESS J1837-069 has a photon index of 1.83 $\pm$ 0.08. Combining with the HESS and MAGIC data, we argue that the gamma-ray emission in this region likely originate from a pulsar wind nebula (PWN). The gamma-ray emission from the northwest part (region A) can be modelled by an ellipse with the semimajor and Semiminor Axis of 0.5$^{\circ}$ and 0.25$^{\circ}$, respectively. The GeV emission has a hard spectrum with a photon index of 2.05 $\pm$ 0.02 and is partially coincide with the TeV source MAGIC J1835-069. The possible origin of the gamma-ray emission in this region is the interaction of the cosmic rays (CRs) accelerated by SNR G24.7+0.6 or/and the OB cluster G25.18+0.26 with the surrounding gas clouds. The GeV gamma-ray emission from the southeast region (region B) can be modeled as an ellipse with the semimajor and Semiminor Axis of 0.9$^{\circ}$ and 0.5$^{\circ}$, respectively, and also reveals a hard gamma-ray spectrum. We argue that the most probable origin is the interaction of the accelerated protons in the young massive star cluster RSGC 1 with ambient gas clouds, and the total cosmic-ray (CR) proton energy is estimated to be as high as $\sim$ 1x10$^{50}$ erg.
M. Fukagawa - One of the best experts on this subject based on the ideXlab platform.
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Subaru Imaging of Asymmetric Features in a Transitional Disk in Upper Scorpius
2014Co-Authors: M. Fukagawa, M. Dong, R. Takami, J. P. Follette, Seeds K. TeamAbstract:polarized intensity images of the circumstellar disk around the star 2MASS J16042165-2130284 obtained with HiCIAO mounted on the Subaru 8.2 m telescope [1]. We present our H-band data, which clearly exhibits a resolved, face-on disk with a large inner hole for the first time at infrared wavelengths (Figure 1). We detect the centrosymmetric polarization pattern in the circumstellar material as has been observed in other disks. Elliptical fitting gives the semimajor Axis, Semiminor Axis, and position angle of the disk as 63 AU, 62 AU, and −14°, respectively. The disk is asymmetric, with one dip located at position angles of ~85°. Our observed disk size agrees well with a previous study of dust and CO emission at submm wavelength with SMA. Hence, the near-infrared light is interpreted as scattered light reflected from th
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Subaru Imaging of Asymmetric Features in a Transitional Disk in Upper Scorpius
The Astrophysical Journal, 2012Co-Authors: Satoshi Mayama, Jun Hashimoto, Takayuki Muto, Takashi Tsukagoshi, Nobuhiko Kusakabe, Masayuki Kuzuhara, Yasuhiro H. Takahashi, Tomoyuki Kudo, Ruobing Dong, M. FukagawaAbstract:We report high-resolution (0.07 arcsec) near-infrared polarized intensity images of the circumstellar disk around the star 2MASS J16042165–2130284 obtained with HiCIAO mounted on the Subaru 8.2 m telescope. We present our H-band data, which clearly exhibit a resolved, face-on disk with a large inner hole for the first time at infrared wavelengths. We detect the centrosymmetric polarization pattern in the circumstellar material as has been observed in other disks. Elliptical fitting gives the semimajor Axis, Semiminor Axis, and position angle (P.A.) of the disk as 63 AU, 62 AU, and –14°, respectively. The disk is asymmetric, with one dip located at P.A.s of ~85°. Our observed disk size agrees well with a previous study of dust and CO emission at submillimeter wavelength with Submillimeter Array. Hence, the near-infrared light is interpreted as scattered light reflected from the inner edge of the disk. Our observations also detect an elongated arc (50 AU) extending over the disk inner hole. It emanates at the inner edge of the western side of the disk, extending inward first, then curving to the northeast. We discuss the possibility that the inner hole, the dip, and the arc that we have observed may be related to the existence of unseen bodies within the disk.
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Subaru Imaging of Asymmetric Features in a Transitional Disk in a Transitional Disk in Upper Scorpius
2012Co-Authors: Satoshi Mayama, Jun Hashimoto, Takayuki Muto, Takashi Tsukagoshi, Nobuhiko Kusakabe, Masayuki Kuzuhara, Tomoyuki Kudo, Ruobing Dong, Y. Takahashi, M. FukagawaAbstract:We report high-resolution (0.07 arcsec) near-infrared polarized intensity images of the circumstellar disk around the star 2MASS J160421652130284 obtained with HiCIAO mounted on the Subaru 8.2 m telescope. We present our H-band data, which clearly exhibit a resolved, face-on disk with a large inner hole for the first time at infrared wavelengths.We detect the centrosymmetric polarization pattern in the circumstellar material as has been observed in other disks. Elliptical fitting gives the semimajor Axis, Semiminor Axis, and position angle (P.A.) of the disk as 63 AU, 62 AU, and 14, respectively. The disk is asymmetric, with one dip located at P.A.s of 85. Our observed disk size agrees well with a previous study of dust and CO emission at submillimeter wavelength with Submillimeter Array. Hence, the near-infrared light is interpreted as scattered light reflected from the inner edge of the disk. Our observations also detect an elongated arc (50 AU) extending over the disk inner hole. It emanates at the inner edge of the western side of the disk, extending inward first, then curving to the northeast. We discuss the possibility that the inner hole, the dip, and the arc that we have observed may be related to the existence of unseen bodies within the disk
