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1
Briggs, D. S., and T. J. Cornwell. "CLEAN/MEM Deconvolution Errors: Semicompact Sources." Symposium - International Astronomical Union 158 (1994): 212–14. http://dx.doi.org/10.1017/s0074180900107612.
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We have run a number of simulations investigating the limitations of noiseless point spread deconvolution with the VLA. On-source errors of more than .01 and off-source dynamic ranges of less than 15,000 were found for some parameters typical of high precision observations. Deconvolution errors were not confined to the support of the source, and limit the dynamic range in at least one VLA observation.
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Anantharamaiah, K. R., V. Radhakrishnan, D. Morris, M. Vivekanand, D. Downes, and C. S. Shukre. "A Search for Radio Recombination Lines of Positronium Near the Galactic Center." Symposium - International Astronomical Union 136 (1989): 607–16. http://dx.doi.org/10.1017/s0074180900187108.
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Several attempts were made to detect the possible radio recombination lines of positronium near the galactic center. An absorption feature seen at λ6cm, in the D-configuration of the VLA was not confirmed by subsequent observations at λ6cm and λ20cm using the B and C configurations of the VLA. An observation at λ3mm using the IRAM 30m telescope also did not detect any line. On the basis of one recombination line photon for every positron (McClintock 1984), our non-detections imply an upper limit to the positron production rate of < 3.1 × 1043 s−1, within about 2″ of the galactic center.
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Rodríguez, Luis F., Guillem Anglada, José M. Torrelles, J. Eduardo Mendoza-Torres, Aubrey D. Haschick, and Paul T. P. Ho. "VLA observations of water maser emission associated with SVS 13." Symposium - International Astronomical Union 206 (2002): 59–62. http://dx.doi.org/10.1017/s0074180900222067.
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The young stellar object SVS 13 has been proposed as the powering source of the HH 7-11 objects. Recent observations have revealed that in the radio continuum (3.6-cm) the source is a binary separated by about 0.3 in the east-west direction. We present Very Large Array observations, made in the highest angular resolution A configuration, of H2O maser emission toward this source. Our data show that the H2O spots appear to be segregated in two velocity groups: a group with radial velocity similar to that of the ambient cloud (VLSR ⋍ 8 km s−1) that is associated with the western radio source, and a blueshifted (by ∼20 km s−1) velocity group that is associated with the eastern radio source. We discuss the possible implications of this observation.
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Inoue, M., E. Fomalont, M. Tsuboi, F. Yusef-Zadeh, M. Morris, H. Tabara, and T. Kato. "VLA Polarization Observation of the Radio Arc at 15 Ghz." Symposium - International Astronomical Union 136 (1989): 269–74. http://dx.doi.org/10.1017/s0074180900186619.
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Polarization measurements of the radio Arc were made with the VLA at 15 GHz. High frequency polarimetry made with high spatial resolution minimizes Faraday depolarization and reveals polarized filaments which correspond to the predominant filaments of the radio Arc. We notice a peculiar linear feature in the polarization map (“thorns”) which suggests the presence of a second magnetic field system. The total intensity maps show no evidence for an interaction between the two field systems, so the thorns may be foreground magnetized structures. However, if the two magnetic field systems do interact, it would allow a model in which the acceleration of relativistic particles takes place at their intersection. The accelerated particles would flow toward both ends of the radio Arc, and account for the intrinsic polarization observed along the entire length of the system. Thermal electrons responsible for the Faraday depolarization occuring at longer wavelengths may be supplied by the interaction of the streams of relativistic particles with relatively dense, ambient thermal clouds.
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Caillault, Jean-Pierre. "VLA observation of the X-ray bright Hyades M dwarfs." Astronomical Journal 97 (January 1989): 163. http://dx.doi.org/10.1086/114964.
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Zhang, B., M. J. Reid, K. M. Menten, X. W. Zheng, and A. Brunthaler. "Distance and Size of the Red Hypergiant NML Cyg." Proceedings of the International Astronomical Union 8, S287 (January 2012): 427–28. http://dx.doi.org/10.1017/s1743921312007478.
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AbstractWe present astrometric results of phase-referencing VLBI observations of 22 GHz H2O maser and 43 GHz SiO maser emission towards the red hypergiant NML Cyg using VLBA. We obtained an annual parallax of 0.62 ± 0.04 mas, corresponding to a distance of 1.61+0.13−0.11 kpc. With a VLA observation in its largest (A) configuration at 43 GHz, we barely resolve the radio photosphere of NML Cyg, and find a uniform-disk diameter of 44 ± 16 mas.
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Goto, T. "Are E+A galaxies dusty-starbursts?: VLA 20 cm radio continuum observation." Astronomy & Astrophysics 427, no. 1 (October 25, 2004): 125–30. http://dx.doi.org/10.1051/0004-6361:20041250.
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Zhi-Yao, Yu. "Stellar Pulsation: (II) Multiple Distinct Shells." International Astronomical Union Colloquium 134 (1993): 169–72. http://dx.doi.org/10.1017/s0252921100014123.
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AbstractWe can find the conclusion with our analysis for VLA observation of OH maser and CO (2–1) emission line that they are distributed on some different distinct shells in the circumstellar envelope, respectively.
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Zijlstra, A., S. R. Pottasch, and C. Bignell. "A VLA Radio Continuum Survey of Planetary Nebulae." Symposium - International Astronomical Union 131 (1989): 60. http://dx.doi.org/10.1017/s007418090013760x.
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With the Very Large Array it is now possible to make high resolution radio continuum maps with sensitivity less than a milliJansky in an observation of only 5 minutes. We have used this so-called snapshot capability to measure about 400 PN north of declination −35. Most of the measurements were carried out at 6 cm. Some of the stronger sources were observed at several frequencies. Most sources were detected, however many nebulae were too weak to map in detail. The resolution ranges from 1.5″ to 1′, depending on the size of the PN. The selected PN have sizes in the range from 4″ to 6′.
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An, Tao, Xiao-Yu Hong, Wen-Xia Feng, and Jun-Hui Zhao. "A Peculiar Broad Line Radio Galaxy 1938-155: VLA Observation at 90 cm." Chinese Journal of Astronomy and Astrophysics 4, no. 6 (December 2004): 527–32. http://dx.doi.org/10.1088/1009-9271/4/6/527.
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Kim, Soon-Wook, and Jeong-Sook Kim. "Quenching of expanding outflow in massive star-forming region W75N(B)-VLA 2." Proceedings of the International Astronomical Union 13, S336 (September 2017): 325–26. http://dx.doi.org/10.1017/s1743921317010183.
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AbstractVLBI observation of masers is a powerful mean to understand the early evolutionary phase of massive star formation. A few different scenarios of outflow evolution in the massive protostars have been proposed, and cannot be readily examined because the precise timing of appropriate maser phenomena is difficult. In particular, it has been a matter of debate whether a well-collimated or a less-collimated outflow comes first in the very early phase of the massive protostellar evolution. Long-term, multi-epoch VLBI monitoring is probably the most important method to trace the outflow evolution. Such a monitoring of a massive star-forming region W75N(B) has been very successful. Since the first detection of the expanding water maser shell associated with the star-forming region VLA 2 of W75N(B) in 1999, the observations in 2005 and 2007 displayed that the expanding water maser shell has been evolved to well-collimated from a less collimated morphology. Observations in 2012 also confirmed such a transition. It would be a major breakthrough in our knowledge of the formation and evolution of the first stages of massive protostars. We performed multi-epoch VLBI observations in mid-2014. On the contrary to its expansion for 13 years, the maser shell at VLA 2 observed in 2014 is comparable to the size observed in 2012. The quenching of the maser shell size indicates that the previously expanding outflow has been decelerated plausibly due to the interaction with surrounding interstellar medium.
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Chiuderi-Drago, F., K. Bocchialini, S. Lamartinie, J. C. Vial, T. Bastian, C. E. Alissandrakis, R. Harrison, J. P. Delaboudinière, and P. Lemaire. "EUV and Microwave Observation of a Filament." International Astronomical Union Colloquium 167 (1998): 55–58. http://dx.doi.org/10.1017/s0252921100047278.
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AbstractSimultaneous XUV and microwave (μ – ѡ) observations of a solar filament, performed by several instruments onboard SOHO and by the Very Large Array (VLA), are analyzed. The filament appears as a dark structure, very similar in shape to the optical Hα filament, in all images taken in the transition region (TR) lines observed by CDS, in the Ne VIII lines observed by SUMER at λ = 770Å and 780Å and at all radio wavelengths with 1.7 cm ≤ λ ≤ 6 cm. Contrary to that, in six TR lines observed by SUMER at λ > 1300Å no trace of the filament, either in absorption or in emission, is visible. Finally, at λ = 21 cm, as well as in all images taken in coronal lines by CDS and EIT, a dark feature is present at the filament position, although with less defined contours than in the first-mentioned TR images. The constraints imposed by all these observations are discussed and interpreted.
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Vermeulen, Monica, Françoise Le Pesteur, Marie-Claude Gagnerault, Jean-Yves Mary, Françoise Sainteny, and Françoise Lepault. "Role of Adhesion Molecules in the Homing and Mobilization of Murine Hematopoietic Stem and Progenitor Cells." Blood 92, no. 3 (August 1, 1998): 894–900. http://dx.doi.org/10.1182/blood.v92.3.894.
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Abstract Bone marrow (BM) transplantation still must overcome multiple difficulties and should benefit from better understanding of stem-cell homing and mobilization. Here, we analyzed the involvement of several adhesion molecules in the two processes by treating mice with monoclonal antibodies against these molecules. Treatment of lethally irradiated mice grafted with isogeneic BM cells showed that at least two migration pathways are important for stem-cell homing to the BM, whereas only one of them is involved in lodging of colony-forming unit–spleen (CFU-S) in the spleen. We confirm that the VLA-4/VCAM-1 adhesion pathway is important for stem-cell homing to the BM only and show that CD44 is involved in CFU-S lodging in both BM and spleen. These results show that entry of CFU-S into the spleen is regulated. The observation that when one migration pathway is altered, CFU-S do not enter the BM via the other pathway may indicate that the two mechanisms involved in CFU-S homing into the BM are linked. The adhesion molecules VLA-4 and CD44 are also implied in the mobilization of stem cells into the blood stream of mice injected once with anti–VLA-4 or anti-CD44. Anti–VLA-4 administration led to a significant increase in circulating stem cells as early as 8 hours after treatment. Stem cells mobilized by anti–VLA-4 comprise cells with high self-renewal potential and thus may be used for long-term reconstitution of the hematopoietic tissue. © 1998 by The American Society of Hematology.
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Vermeulen, Monica, Françoise Le Pesteur, Marie-Claude Gagnerault, Jean-Yves Mary, Françoise Sainteny, and Françoise Lepault. "Role of Adhesion Molecules in the Homing and Mobilization of Murine Hematopoietic Stem and Progenitor Cells." Blood 92, no. 3 (August 1, 1998): 894–900. http://dx.doi.org/10.1182/blood.v92.3.894.415k22_894_900.
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Bone marrow (BM) transplantation still must overcome multiple difficulties and should benefit from better understanding of stem-cell homing and mobilization. Here, we analyzed the involvement of several adhesion molecules in the two processes by treating mice with monoclonal antibodies against these molecules. Treatment of lethally irradiated mice grafted with isogeneic BM cells showed that at least two migration pathways are important for stem-cell homing to the BM, whereas only one of them is involved in lodging of colony-forming unit–spleen (CFU-S) in the spleen. We confirm that the VLA-4/VCAM-1 adhesion pathway is important for stem-cell homing to the BM only and show that CD44 is involved in CFU-S lodging in both BM and spleen. These results show that entry of CFU-S into the spleen is regulated. The observation that when one migration pathway is altered, CFU-S do not enter the BM via the other pathway may indicate that the two mechanisms involved in CFU-S homing into the BM are linked. The adhesion molecules VLA-4 and CD44 are also implied in the mobilization of stem cells into the blood stream of mice injected once with anti–VLA-4 or anti-CD44. Anti–VLA-4 administration led to a significant increase in circulating stem cells as early as 8 hours after treatment. Stem cells mobilized by anti–VLA-4 comprise cells with high self-renewal potential and thus may be used for long-term reconstitution of the hematopoietic tissue. © 1998 by The American Society of Hematology.
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van de Wiel-van Kemenade, E., Y. van Kooyk, AJ de Boer, RJ Huijbens, P. Weder, W. van de Kasteele, CJ Melief, and CG Figdor. "Adhesion of T and B lymphocytes to extracellular matrix and endothelial cells can be regulated through the beta subunit of VLA." Journal of Cell Biology 117, no. 2 (April 15, 1992): 461–70. http://dx.doi.org/10.1083/jcb.117.2.461.
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Investigating the regulation of very late antigen (VLA)-mediated functions, we found that TS2/16, a mAb directed against the beta chain of the VLA group of integrins, can induce binding of resting peripheral blood lymphocytes, cloned T lymphocytes, and Epstein Barr virus-transformed B cells to extracellular matrix components, fibronectin, laminin, and collagen, but not to fibrinogen. The antibody stimulates VLA-4-, VLA-5-, and VLA-6-mediated binding. Furthermore, it induces VLA-4-mediated binding to vascular cell adhesion molecule-1 expressed by rTNF-alpha-stimulated endothelial cells, but it does not stimulate homotypic aggregation of cells as described for a number of anti-VLA-4 alpha antibodies (Bednarczyk, J.L., and B. W. McIntyre. 1990. J. Immunol. 144: 777-784; Campanero, M. R., R. Pulido, M. A. Ursa, M. Rodríguez-Moya, M. O. de Landázuri, and F. Sánchez-Madrid. 1990. J. Cell Biol. 110:2157-2165). Therefore, the stimulating activity of this anti-beta 1 antibody clearly contrasts with that of the anti-VLA-4 alpha antibodies, which induce homotypic cell aggregation, but not binding of cells to extracellular matrix components or endothelial cells, indicating that TS2/16 may generate different signals. The observation that also F(ab')2 or Fab fragments of this anti-beta 1 antibody stimulate binding to extracellular matrix components and endothelial cells excludes the possibility that binding requires receptor crosslinking, or is Fc receptor mediated. Induction of this adhesion is cation and energy dependent and requires an intact cytoskeleton. Although changes in the conformation of VLA integrins induced by this antibody may regulate their functional activity, the dependence on metabolic energy indicates that intracellular processes may also play a role.
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Montes, V. A., Peter Hofner, C. Anderson, and V. Rosero. "Is there a cluster in the massive star forming region IRAS 20126+4104?" Proceedings of the International Astronomical Union 12, S316 (August 2015): 157–58. http://dx.doi.org/10.1017/s1743921315010558.
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AbstractA Chandra X-ray Observatory ACIS-I observation and a 6 cm continuum radio observation with the Karl G. Jansky Very Large Array (VLA) together with a multiwavelength study in infrared (2MASS and Spitzer) and optical (USNO-B1.0) shows an increasing surface density of X-ray sources toward the massive protostar. There are at least 43 YSOs within 1.2 pc distance from the massive protostar. This number is consistent with typical B-type stars clusters (Lada & Lada 2003).
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Byrne, P. B., and D. E. Gary. "A Flare on AD Leo observed in Optical, UV and Microwaves." International Astronomical Union Colloquium 104, no. 2 (1989): 63–66. http://dx.doi.org/10.1017/s0252921100153813.
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SummaryWe report a simultaneous IUE, VLA and ground-based photometric observation of a flare on the dMe star, AD Leo, on 2nd February 1903. The optical flare was extremely impulsive, lasting in total only about 3 mins. A relatively longlived 6 cm flare was observed with the VLA which was initially 100% polarized. An IUE spectrum, taken ≈ 8 min after the onset of the optical U band flare, shows motu than a factor of 2 increase in the Ha II λ 1640Å emission line. The other mid-transition region lines such as C IV λλ154B/52Å show almost no response.
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Sawada-Satoh, S., M. Inoue, K. M. Shibata, S. Kameno, N. Nakai, V. Migenes, and P. J. Diamond. "HI and OH Absorption of the Nuclear Region of NGC 3079." Symposium - International Astronomical Union 205 (2001): 196–97. http://dx.doi.org/10.1017/s0074180900220949.
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We conducted an observation of weak HI and OH absorption features in the parsec-scale nuclear region of NGC 3079 using a global VLBI network; the VLBA, the VLA and the Green Bank 43-m telescope of NRAO. One mas corresponds to 0.076 pc in NGC 3079.
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Dressel, L. L. "The Distribution and Kinematics of Neutral Hydrogen in NGC 807." Symposium - International Astronomical Union 127 (1987): 423–24. http://dx.doi.org/10.1017/s0074180900185559.
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I have detected 21 cm line emission from neutral hydrogen in the giant elliptical galaxy NGC 807 at Arecibo Observatory, and I have mapped this emission with the VLA. Unlike the active and dwarf ellipticals that have been mapped thus far, NGC 807 has a fairly regular disk of gas rotating about the apparent optical minor axis. Combined with observations of active ellipticals, this observation suggests that two classes of HI-rich ellipticals may exist: ellipticals which have accreted gas and become active recently, and quiescent ellipticals which have either produced gas internally or accreted it so long ago that it has reached dynamical equilibrium.
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Cully, S. L., J. Dupuis, T. Rodriguez-Bell, G. Basri, O. H. W. Siegmund, J. Lim, and S. M. White. "EUVE and VLA Observations of the Eclipsing Pre-Cataclysmic Variable V471 Tauri." International Astronomical Union Colloquium 152 (1996): 349–54. http://dx.doi.org/10.1017/s0252921100036216.
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We present observations of the eclipsing binary V471 Tauri by the Extreme Ultraviolet Explorer (EUVE) and the Very Large Array (VLA). The EUV spectrum is dominated by the continuum of the hot white dwarf and the time-averaged spectrum is fitted by a 33.1 ± 0.5 × 103 K pure hydrogen white dwarf atmosphere assuming log g = 8.5. An ISM hydrogen column density of 1.5 ± 0.4 × 1018 cm−2 is required to explain the attenuation of the white dwarf spectrum thus setting the HI column in the line of sight of the Hyades cluster. The He II λ304 Å line is in emission and varies over the orbital period of V471 Tauri following a sinusoidal modulation with the maximum reached when the K star is at inferior conjunction. Transient dips are detected at orbital phase −0.12 in the SW and MW spectrometers integrated lightcurves but are notably absent in the LW lightcurve indicating the occulting material is ionized. The VLA observation suggest the presence of a K star coronal magnetic loop between the two stars reconnecting with the white dwarf magnetic field. Such a structure could be the occulting source needed to explain the dips seen in the lightcurves of V471 Tauri in the EUV.
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Kaufmann, R., D. Frösch, C. Westphal, L. Weber, and C. E. Klein. "Integrin VLA-3: ultrastructural localization at cell-cell contact sites of human cell cultures." Journal of Cell Biology 109, no. 4 (October 1, 1989): 1807–15. http://dx.doi.org/10.1083/jcb.109.4.1807.
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The integrin VLA-3 is a cell surface receptor, which binds to fibronectin, laminin, collagen type I and VI (Takada, Y., E. A. Wayner, W. G. Carter, and M. E. Hemler. 1988. J. Cell. Biochem. 37:385-393) and is highly expressed in substrate adherent cultures of almost all human cell types. The ligand specificity of VLA-3 and the inhibition of cell adhesion by anti-VLA-3 monoclonal antibodies suggest its involvement in cell-substrate interaction. In normal tissues, VLA-3 is restricted to few cell types, notably the kidney glomeruli and basal cells of the epidermis. In the epidermis, VLA-3 is generally strongly expressed on the entire plasma membrane of basal cells and is not polarized towards the basement membrane (Klein, C. E., C. Cardon-Cardo, R. Soehnchen, R. J. Cote, H. F. Oettgen, M. Eisinger, and L. J. Old. 1987. J. Invest. Dermatol. 89:500-507). Based on this finding we speculated that, in addition to a role of VLA-3 for adhesion of cells to substrate, it could also be relevant for cell-cell interaction. To investigate this, we ultrastructurally localized VLA-3 on the surface of cultured cells by immunoelectron microscopy. In accordance with our concept, we found VLA-3 strongly associated with intercellular contact sites. Interestingly, very little immunoreactivity was detected at the under-surface of cells which had been cultured for 18-32 h. This observation was unexpected but is consistent with previous findings (Kantor, R. R. S., M. J. Mattes, K. D. Lloyd, L. J. Old, and A. P. Albino. 1987. J. Biol. Chem. 262:15158-15165) which suggest that the association of VLA-3 with the basal surface of substrate adherent tumor cells is a late event occurring after days of culture under confluent conditions. However, we cannot formally rule out VLA-3 expression at the undersurface of cells under our experimental conditions, since VLA-3 molecules at this location could be inaccessible for in situ labeling of unfixed cells because of spatial interferences. In conclusion, our results demonstrate the expression of VLA-3 at intercellular contact sites of cultured cells supporting the concept that it may be relevant for intercellular interactions also.
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Walter, H. G., R. Hering, H. Lenhardt, Chr deVegt, D. R. Florkowski, and K. J. Johnston. "Accuracy Assessment of Hipparcos Optical and VLA Radio Positions of Stars." Symposium - International Astronomical Union 156 (1993): 377–80. http://dx.doi.org/10.1017/s007418090017353x.
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Optical positions of some 30 radio stars derived from 12 months of HIPPARCOS measurements are compared with their radio positions obtained with the Very Large Array (VLA). — Once the lengths of arcs between optical and radio positions of pairs of stars are calculated the differences of the arcs are formed. They provide an estimate of the coincidence of the optical and radio emission centres. — From the comparison of optical and radio positions infinitesimal rotation angles of the HIPPARCOS frame with respect to the VLA extragalactic reference frame are determined by rigid rotations. After taking account of the relative orientation of the frames the standard deviations of the remaining residuals are approximately of the order of the VLA observation errors, thus demonstrating the reliability of the HIPPARCOS results. However, they also indicate some data noise very likely caused by the low accuracy of optical proper motions used to bridge the HIPPARCOS-radio epoch differences up to 9 years, and possible discrepancies of radio-optical emission centres of some stars.
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Crutcher, R. M. "VLA Mapping of Magnetic Fields in W 3 and S 106." Symposium - International Astronomical Union 140 (1990): 315–17. http://dx.doi.org/10.1017/s0074180900190321.
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The importance of magnetic fields to the evolution of dense interstellar clouds and to the star formation process is now widely appreciated. Troland (this volume) has reviewed work to measure strengths of interstellar magnetic fields by observation of the Zeeman effect in radio frequency spectral lines. The next step is to map magnetic fields with radio synthesis arrays in order to obtain high spatial resolution. This abstract is a preliminary report of VIA results for two clouds - the W 3 region of massive star formation (to be published by Troland, Crutcher, Goss, and Heiles) and S 106, a biconical H II region with a confining molecular disk (to be published by Loushin, Crutcher, and Troland).
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Tissino, Erika, Chiara Caldana, Dania Benedetti, Francesca Rossi, Michele Dal Bo, Pietro Bulian, Riccardo Bomben, et al. "Retention of inside-out VLA-4 Integrin Activation upon B-Cell Receptor Triggering in in-Vitro and in-Vivo Ibrutinib Treated Chronic Lymphocytic Leukemia Cells: Clinical Implication." Blood 126, no. 23 (December 3, 2015): 1708. http://dx.doi.org/10.1182/blood.v126.23.1708.1708.
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Abstract Background. Ibrutinib (IB), an orally administered Bruton tyrosine kinase (BTK) inhibitor antagonizing B-cell receptor (BCR) signaling, has demonstrated high response rates in chronic lymphocytic leukemia (CLL). Transient lymphocytosis is a common, although variable, clinical feature during IB treatment, which has been related to the efflux of CLL cells from lymphoid organs, due to impairment of microenvironmental interactions. CD49d, a strong negative prognosticator in CLL, is the alpha-chain of the integrin heterodimer CD49d/CD29 (VLA-4), a key player of CLL microenvironmental interactions. The adhesive properties of VLA-4 can be rapidly inside-out activated by BCR signals, although the role of BCR as VLA-4 activator in CLL is largely unknown. Aim. To understand whether the inhibition of the BCR signaling by IB exposure of CLL cells affects VLA-4 activation. Methods. The study included 28 refractory/relapsed CLL patients (15 CD49d+, 23 IGHV unmutated, 22 del11q/del17p) treated with IB on a compassionate basis (IB-CLL), and 11 additional CD49d+ CLL cases (7 IGHV unmutated, 1 del17p). Levels of the active VLA-4 were assessed by flow cytometry using an LDV-containing small molecule as VLA-4 specific ligand, along with the conformation sensitive anti-CD29 HUTS-21 mAb, and measuring the VLA-4 receptor occupancy (VLA4-RO) in values ranging from 0.0 (no RO) to 1.0 (100% RO) as in Chigaev et al. (J Biol Chem, 284,14337, 2009). According to this measurement higher RO indicates larger fraction of high affinity VLA-4 receptors. BCR engagement was performed using goat F(ab′)2 anti-human IgM. CD49d, CD29, IgM expression, the phosphorylation state of ERK (pERK) and BTK (pBTK), and Ca++ release were cytometrically analysed. Adhesion assays were performed on VCAM-1-coated slides. Results. CD49d+IB-naïve cells from 18 CLL cases, including 7 pre-treatment IB-CLL, were stimulated with anti-IgM. Although with variability, in all cases cells responded to BCR triggering in terms of increased pERK (mean anti-IgM/control MFI ratio: 1.7), pBTK (mean anti-IgM/control MFI ratio: 1.3), and Ca++ release (mean Ca++ release increase: 11.9%). IgM stimulation resulted in an increased VLA-4 RO (mean 0.52, range 0.40-0.73, vs. mean 0.38, range 0.22-0.63; p=0.0002) in CLL, but not in residual T cells (mean 0.34 vs. 0.35). Consistently, VLA-4-dependent CLL cell adhesion to VCAM-1 increased upon IgM stimulation (mean values of adherent cells/control= 4.6 vs 3.7, p=0.008). IB treatment in vitro ( 1µM, 1 hour) overall impaired BCR signaling, as shown by lower increases of pERK ( mean anti-IgM/control MFI ratio: 1.1), pBTK (mean anti-IgM/control MFI ratio: 1.2) and Ca++ release (mean increase: 7.4%). However, VLA-4 RO increased from a mean of 0.37 (range 0.18-0.65) to 0.47 (range 0.15-0.65) after IgM stimulation (p=0.0007), and a parallel increased adhesion was observed (mean values of adherent cells/control= 2.4 vs 3.7). We then moved to cells collected from IB-CLL on t30 of IB treatment (n=7), which showed slightly decreased (79-86%) CD49d, CD29, and IgM MFI levels compared to pre-treatment cells. Despite an overall impaired BCR signaling (mean Ca++ release increase: 12.4% at pre-treatment, 3.6% at t30), IgM stimulation still increased both VLA-4 RO (mean 0.27, range 0.01-0.45 compared to 0.53, range 0.41-0.84, p=0.010) and CLL cell adhesion. Similarly, cells from IB-CLL on day 60-90 of treatment (n=3) kept showing an increased VLA-4 RO upon IgM stimulation (from 0.14, range 0.10-0.17 to 0.34, range 0.20-0.56), although Ca++ release was relevantly decreased (from 14.8% at pre-treatment to 4.3% at t60-90). Finally, the impact of CD49d expression on the IB-induced lymphocyte redistribution in the 28 IB-CLL was evaluated. Absolute lymphocyte count (ALC) at baseline and after 30-120 days of IB therapy were lower in CD49d+ than CD49d- CLL (see Figure), with a lower median percentage ALC rise from baseline (0% vs +132%, p=0.0044). Consistently, at day t30/t60, >50% reduction of lymph nodes/spleen from pre-treatment stage only occurred in CD49d- CLL (8/13 cases), while CD49d+ CLL usually experienced reductions <50% (11/12 cases). Conclusions. BCR triggering in CLL cells activates VLA-4 via an inside-out pathway at least in part independent to IB blockage of BTK. This observation has clinical implication in the kinetics of ALC, shrinkage of CLL masses, and should be considered in the design of IB therapies. Figure 1. Figure 1. Disclosures No relevant conflicts of interest to declare.
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De Becker, M., G. Rauw, R. Blomme, W. L. Waldron, H. Sana, J. M. Pittard, P. Eenens, et al. "Quasi-simultaneous XMM-Newton and VLA observation of the non-thermal radio emitter HD 168112 (O5.5III(f$\mathsf{^+}$))." Astronomy & Astrophysics 420, no. 3 (June 2004): 1061–77. http://dx.doi.org/10.1051/0004-6361:20041030-1.
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Gelfand, Joseph D., T. Joseph, W. Lazio, and Bryan M. Gaensler. "A 330 MHz Survey for Pulsars and Supernova Remnants in M31." Symposium - International Astronomical Union 218 (2004): 91–92. http://dx.doi.org/10.1017/s0074180900180696.
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In the radio band, supernova remnants (SNRs) and pulsars are best identified at low frequencies due to their steep spectrA. Motivated by this fact, we have carried out a deep 330-MHz observation of M31 using the VLA. Achieving a sensitivity of 0.6 mJy at 6″ resolution over the entire optical disk of M31, we identified 405 distinct radio sources. While most of these are unresolved background radio galaxies, we found five SNR candidates, three pulsar wind nebula (PWN) candidates, and three pulsar candidates in our source list. The properties of these sources are discussed.
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Carignan, Claude. "Cosmic Web Research: Where are the Missing Dwarf Galaxies and the Inter-Galactic Hi Clouds." Proceedings of the International Astronomical Union 14, S344 (August 2018): 331–39. http://dx.doi.org/10.1017/s1743921318005793.
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AbstractWe know that the observed H i (and H2) content cannot explain the SFR observed in galaxies. The only way galaxies can sustain that SFR is by accreting HI-rich dwarf galaxies or Inter-Galactic HI clouds. However, no observation to detect those accretion events has been conclusive so far. Instruments having the necessary sensitivity (e.g. GBT) lack the necessary spatial resolution and those with the proper resolution (e.g. VLA) lack the sensitivity. I will show that both are necessary to detect those illusive Hi clouds. The SKA precursor MeerKAT is starting its operation as we speak and will start the Large Survey Programs at the end of 2018. FAST has started its observations in drift scan mode with CRAFTS (Commensal Radio Astronomy Fast Survey). In the near future (2019-20), the best combination to study low column density H i will be to combine the sensitivity of FAST with the spatial resolution of MeerKAT.
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Szenes, Eva, Andrea Härzschel, Erika Tissino, Pischeli Justine, Julia Gutjahr, Sandra Pennisi, Jan Höpner, et al. "BCR-Induced VLA-4 Activation in the TCL1 Transgenic Mouse Model for Chronic Lymphocytic Leukemia." Blood 134, Supplement_1 (November 13, 2019): 1730. http://dx.doi.org/10.1182/blood-2019-125634.
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Introduction. Ibrutinib, a small molecule inhibitor of Bruton's tyrosine kinase (BTK), has proven to be an efficient treatment for chronic lymphocytic leukemia (CLL). A distinct characteristic of ibrutinib therapy is transient lymphocytosis. Recently, we have demonstrated that CLL patients with high levels of CD49d show reduced lymphocytosis and inferior nodal response under ibrutinib due to residual activity of BCR-induced inside-out activation of the CD49d/CD29 integrin VLA-4 (Tissino E et al. J Exp Med. 2018;215(2):681-697). Here, we used Tcl1 transgenic (tg) mice as a model to further validate the observation of VLA-4 activation under ibrutinib and to study involved signaling pathways and the effect of VLA-4 inhibition in vivo. Methods. Surface receptor expression analysis of various receptors was performed by flow cytometry. The phosphorylation of signaling molecules was measured by phosflow and western blotting. VLA-4 affinity state was determined by a real-time kinetic assay described in Chigaev A et al. J Biol Chem. 2001;276(52):48670-8. To analyze the distribution of individual VLA-4 molecules on the cell surface, immunofluorescence approaches and superresolution microscopy (STORM, Abbelight) were employed. Mouse treatment studies were performed upon transplantation of TCL1-tg splenocytes to wild-type C57BL/6J mice using the small molecule VLA-4 inhibitor firategrast in drinking water. Tumor infiltration of different organs was measured by flow cytometry. Results. Analyzing the surface expression of CD49d and other homing receptors, we found that TCL1-tg mice correspond with the CD49d-high CLL cohort. We found that both CLL cells from TCL1-tg mice and human CD49d-high CLL show similar CD49d expression levels as the corresponding healthy B cells (human: N = 116 CD49d-high CLL and 32 healthy donor, P = 0.8717; mouse: N = 12 per group, P = 0.6845). Next, we analyzed the impact of BCR pathway inhibitors on the phosphorylation of signaling molecules involved in the BCR pathway after activation by anti-IgM (aIgM) in TCL1-tg leukemic cells. Ibrutinib and idelalisib showed specific patterns of inhibition of BTK and PI3K, respectively. The combination of ibrutinib and idelalisib proved to be the most efficient in reducing the phosphorylation of BTK, SYK, ERK1/2 and Akt upon IgM activation, compared to the phosphorylation of stimulated cells without inhibition (N = 6, P = 0.0003, 0.0305, 0.0039, 0.0019, respectively). IgM stimulation induced VLA-4 high affinity as well as a reorganization of VLA-4 molecules on the cell surface, forming areas of high VLA-4 density. BCR-induced inside-out activation of VLA-4 remained functional upon treatment with ibrutinib (N = 5, cnt vs aIgM P = 0.0017, cnt vs ibrutinib+aIgM P = 0.0499), while idelalisib reduced VLA-4 activation more effectively (N = 5, cnt vs aIgM P = 0.0014, cnt vs idelalisib+aIgM P = 0.0803), suggesting a pivotal role of PI3K in the transmission of the exogenous antigen signal to the integrin. Finally, to analyze the potential of VLA-4 blockage in a tumor setting similar to VLA-4-high CLL patients, we treated wild-type C57BL/6J mice (N = 6 mice per group), which were transplanted with TCL1-tg splenocytes, with the CD49d inhibitor firategrast. This treatment reduced the tumor load in spleen and bone marrow. Conclusion. We found that the TCL1-tg mouse model is adequate to study the activity of the BCR-VLA-4 axis in CLL. Using this model, we show that a) BCR stimulation induces both, an increase in VLA-4 affinity as well as avidity (clustering), b) that PI3K is an essential transmitter between BCR and VLA-4, and c) that VLA-4 inhibition alters tumor infiltration patterns in vivo. Synergies of VLA-4 blockage with established therapy options as a possible way of reducing microenvironment-induced resistance development are currently been investigated. Disclosures Egle: Celgene: Honoraria, Other: Advisory board and Travel support. Greil:Eisai: Honoraria; Daiichi Sankyo: Consultancy, Honoraria; Sandoz: Honoraria; Genentech: Honoraria, Research Funding; Cephalon: Consultancy, Honoraria, Research Funding; Sanofi Aventis: Honoraria; Janssen-Cilag: Honoraria; AstraZeneca: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; GSK: Research Funding; Boehringer Ingelheim: Honoraria; AbbVie: Consultancy, Honoraria, Research Funding; Roche: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; Pfizer: Honoraria, Research Funding; Bristol-Myers-Squibb: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; Merck: Consultancy, Honoraria, Research Funding; Mundipharma: Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; Celgene: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; Novartis: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; MSD: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Ratiopharm: Research Funding; Gilead: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding.
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Harris, D. B., G. D'Spain, and A. Goldner. "Regional observation of a nuclear test from a vertical hydrophone array." Bulletin of the Seismological Society of America 84, no. 4 (August 1, 1994): 1148–53. http://dx.doi.org/10.1785/bssa0840041148.
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Abstract In order to evaluate the potential of water-column vertical hydrophone arrays for the measurement of continental events at regional distances, ocean acoustic data bases were examined for arrivals from these types of events. In 1987, the nuclear test LOCKNEY (mb 5.7, 37.28°N 116.38°W) was observed in the deep-ocean water column at a range of 900 km by the Vertical Line Array (VLA) at 35° N 126° W. Although the hydrophone data were contaminated below 10 Hz by array suspension noise and ocean acoustic noise, adaptive array processing allows us to extract the P and T phases. The root-mean-square (rms) direct P-wave amplitude in the water column is 100.6 dB referenced to 1 μPa in the 4- to 8-Hz band in a 20-sec window, which suggests a detection threshold of mb 5.2 in a deep oceanic environment at this range for a single hydrophone. The arrival time of the T phase [i.e., the portion of seismic energy that has somehow coupled into, and propagated within, the deep ocean sound channel (Aki and Richards, 1980)] is consistent with a P-wave conversion at the continental margin, assuming a velocity of 6 km/sec from NTS to the continental margin and acoustic propagation at 1.5 km/sec in the water column from the continent to the array.
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Brown, Alexander, Joanna M. Brown, Rachel A. Osten, Thomas R. Ayres, and Edward Guinan. "Coronal Activity on Rapidly-Rotating Solar-Like Stars: Chandra Observations of ER Vul." Symposium - International Astronomical Union 215 (2004): 334–35. http://dx.doi.org/10.1017/s007418090019583x.
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We investigate the coronal structure of rapidly-rotating, solar-like stars using Chandra HETGS spectra of the short-period binary ER Vul, and by comparison with X-ray observations of the Sun and other dwarf stars. ER Vul consists of two solar-like (G0 + G5) dwarfs with rotation rates ~ 40 times that of the Sun. This binary is not interacting and these stars are the fastest rotating G dwarfs suitable for high resolution X-ray spectroscopy. X-ray (1.8-40 Å) spectra were obtained on 2001 March 29-30 along with 10.5 hours of simultaneous VLA monitoring at 3.6 and 20 cm. These spectra show hot, multi-temperature coronal emission with emission lines ranging in temperature from O VII (2 MK) to Fe XXIV (30 MK). ER Vul showed only low-level variability during the X-ray observation. Unlike the behaviour of longer period active binaries, no large, long-duration flares were detected, consistent with previous X-ray observations of this binary. No evidence for eclipses is seen in either the X-ray or radio emission. The coronal emission measure distribution and elemental abundances were derived for ER Vul.
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Caillault, J. P., J. Patterson, and D. Skillman. "The Radio Light Curve of V471 Tauri." International Astronomical Union Colloquium 104, no. 2 (1989): 119–21. http://dx.doi.org/10.1017/s0252921100153953.
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AbstractWe have observed the white dwarf — K dwarf eclipsing binary system V471 Tauri with the VLA. We have detected in the radio flux an interesting dip centered near phase zero (the phase of white dwarf eclipse) and a 6 mJy flare shortly after mid—eclipse at phase 0.15. The best possible explanation for the dip is the self—eclipse of a large radio—emitting cloud anchored to a particular spot on the secondary, namely the sub—white dwarf point. The 6 cm flare observation and sudden variations seen in Hα suggest that this spot is an active flaring region.
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Morrison, L. V., D. Hestroffer, D. B. Taylor, and F. Van Leeuwen. "Check on JPL DExxx Using Hipparcos and Tycho Observations." Highlights of Astronomy 11, no. 1 (1998): 554. http://dx.doi.org/10.1017/s1539299600022115.
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Obervations of the positions of Europa (J2) and Titan (S6) by Hipparcos, and Ganymede (J3) and Callisto (J4) by Tycho are analysed to give checks on the latest JPL ephemerides of the planets Jupiter and Saturn.The observed positions of the satellites are compared with DExxx, using the G5 theory of the Galilean satellites and D.B. Taylor’s theory ofTitan to calculate their offsets from the barycentres of the two systems.Each Tycho observation can be resolved into RA and Dec because the slitsare inclined to the scan direction. Hipparcos, on the other hand, which hasa uni-directional scan, requires a minimum of two (preferably orthogonal) scans to resolve the offsets into RA and Dec. We have subdivided the Hipparcos observations in time and solved for corrections to DExxx at several epochs over the period of the mission.The Hipparcos observations of J2, and Tycho of J3 and J4, put tight constraints on the orbit of Jupiter, and agree closely with the series of ground-based observations made by the Carlsberg Meridian Telescope. In particular, they help to resolve a problem in the declination of Jupiter associated with larger than expected errors in the tracking of Voyager II and radio positions from the VLA.
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Moffett, David A., and Timothy H. Hankins. "Multifrequency Radio Properties of the Crab Pulsar." International Astronomical Union Colloquium 160 (1996): 283–84. http://dx.doi.org/10.1017/s0252921100041713.
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During a single Arecibo observation in 1981 of the Crab pulsar, a profile at 4.7 GHz was recorded which appeared to contain additional components and an interpulse (IP) shifted to earlier phase. The experiment was continued at the VLA, taking advantage of its phased array mode to form a synthesized beam, which resolves out the bright Crab Nebula background. Observations were conducted between February 9 and May 27, 1994, at 0.33, 1.4, 4.9, and 8.4 GHz. Additional radio profiles presented here were recorded at Arecibo (0.43, 0.6, and 4.7GHz) and Effelsberg (2.7GHz) by Hankins & Fowler (unpublished).In Figure 1 we have plotted a summary of normalized profiles from several radio frequencies and infrared. The VLA profiles are time aligned, while the rest are aligned to the main pulse (MP). A new component (labeled LFC) appears 36° ahead of the MP between 0.6 and 4.9 GHz, not coincident with the position of the precursor, and with a spectral index similar to that of the MP. The MP disappears at 8.4 GHz, probably due to spectral effects. The IP appears to undergo a transition in phase and flux, disappearing at 2.7 GHz and reappearing 10° earlier at 4.7 GHz with a radically different spectral index. Two high radio frequency components (labeled HFC1 and HFC2) appear at 4.9 and 8.4 GHz, and possibly at the noise level at 1.4 GHz. They have flatter spectral indices than the MP and IP and their centroid phase changes with respect to the MP – moving to later phase with increasing frequency. The infrared profile exhibits a “bump”, or third component near the same phase as HFC1 and HFC2.
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Pokorny, Martin, Casey J. Law, Geoffrey C. Bower, Sarah Burke-Spolaor, Bryan J. Butler, Paul Demorest, S. E. Khudikyan, T. Joseph W. Lazio, James Robnett, and Michael Rupen. "Vys: A Protocol for Commensal Fast Transient Searches and Data Processing at the Very Large Array." Journal of Astronomical Instrumentation 07, no. 02n03 (September 2018): 1850005. http://dx.doi.org/10.1142/s2251171718500058.
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We describe a new protocol deployed at the National Radio Astronomy Observatory’s Karl G. Jansky Very Large Array (VLA) to support the distribution of data in support of commensal data analysis. The protocol, vys, is designed to provide access to a high time resolution data stream while a primary observation continues with the typical (lower) time resolution data stream. This form of dual time resolution, commensal observing has been implemented to enable the search for millisecond astrophysical transient events by a new, dedicated compute cluster located at the VLA. The fast transient detection system, realfast, performs real-time analysis in situ to detect events of interest and record relatively short duration data “cut-outs” of those events. By selectively recording high time resolution data, provided by vys at rates of up to 1.4[Formula: see text]GB[Formula: see text]s[Formula: see text], realfast will reduce the recorded data volume by an estimated factor of up to 1000. This makes it possible to search for transients commensally in a high data rate stream over the thousands of hours needed to find the rarest events.
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Tsuji, Takashi. "Warm Molecular Sphere around Red Supergiant Stars—A Missing Link between the Photosphere and Masering Water Clouds in the Circumstellar Envelope." Symposium - International Astronomical Union 205 (2001): 316–17. http://dx.doi.org/10.1017/s0074180900221347.
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Interferometry of red supergiants before 2000: The M2 supergiant Betelgeuse (α Ori) is the first star whose angular diameter was measured by the Michelson stellar interferometer (Michelson & Pease 1921). Since then, however, we had to wait half a century before we witnessed the renaissance of interferometric observations in optical astronomy with novel methods such as speckle interferometry (Laberie 1970). Michelson's classical method was also extended to the infrared regime (e.g. McCarthy et al. 1977). The initial results served not only to compare stellar temperature scale with the measured angular diameters but also to probe scattering and thermal emission in the dust envelope around red supergiant stars (e.g. Tsuji 1978,1979). Interferometry has been more active in the radio domain: In connection with our subject, VLBI observations revealed many masering water clouds around red supergiants such as VY CMa (Imai et al. 1997) and S Per (Richards et al. 1999), but their origin in unknown. Also, radio observation of Betelgeuse with the VLA (Lim et al. 1998) revealed the presence of a new component of modest temperatures (Tex ≲ 3500 K) over the same height range as the classical chromosphere (Tex ≳ 5000 K), but again the nature of the new component remains obscure.
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de Gasperin, F., G. Brunetti, M. Brüggen, R. van Weeren, W. L. Williams, A. Botteon, V. Cuciti, et al. "Reaching thermal noise at ultra-low radio frequencies." Astronomy & Astrophysics 642 (October 2020): A85. http://dx.doi.org/10.1051/0004-6361/202038663.
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Context. Ultra-low frequency observations (< 100 MHz) are particularly challenging because they are usually performed in a low signal-to-noise ratio regime due to the high sky temperature and because of ionospheric disturbances whose effects are inversely proportional to the observing frequency. Nonetheless, these observations are crucial for studying the emission from low-energy populations of cosmic rays. Aims. We aim to obtain the first thermal-noise limited (∼1.5 mJy beam−1) deep continuum radio map using the Low Frequency Array’s Low Band Antenna (LOFAR LBA) system. Our demonstration observation targeted the galaxy cluster RX J0603.3+4214 (known as the Toothbrush cluster). We used the resulting ultra-low frequency (39–78 MHz) image to study cosmic-ray acceleration and evolution in the post shock region considering the presence of a radio halo. Methods. We describe the data reduction we used to calibrate LOFAR LBA observations. The resulting image was combined with observations at higher frequencies (LOFAR 150 MHz and VLA 1500 MHz) to extract spectral information. Results. We obtained the first thermal-noise limited image from an observation carried out with the LOFAR LBA system using all Dutch stations at a central frequency of 58 MHz. With eight hours of data, we reached an rms noise of 1.3 mJy beam−1 at a resolution of 18″ × 11″. Conclusions. The procedure we developed is an important step towards routine high-fidelity imaging with the LOFAR LBA. The analysis of the radio spectra shows that the radio relic extends to distances of 800 kpc downstream from the shock front, larger than what is allowed by electron cooling time. Furthermore, the shock wave started accelerating electrons already at a projected distance of < 300 kpc from the crossing point of the two clusters. These results may be explained by electrons being re-accelerated downstream by background turbulence, possibly combined with projection effects with respect to the radio halo.
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Akujor, C. E., R. W. Porcas, and I. Fejes. "A World Array VLBI Image of 3C216 at 1.6GHz." Symposium - International Astronomical Union 175 (1996): 83–84. http://dx.doi.org/10.1017/s0074180900080116.
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The quasar 3C216 has the distinction of being classified as a blazar as well as a compact steep-spectrum radio source (Akujor et al, 1993). It has a grossly mis-aligned large-scale radio structure. Previous VLBI images include those of the core region (Barthel et al 1988; Venturi et al 1993) with 1 mas resolution, and the sub-kpc scale core-jet with resolution ca. 25 mas (Fejes et al, 1992; Akujor et al, 1993). In order to investigate the connection between these structures seen on different scales, we have made a 1.6 GHz observation of the core-jet region with a “World Array” VLBI network. This consisted of 20 antennas, at Effelsberg (Germany), Jodrell “Lovell” (UK), Westerbork (Netherlands), Medicina and Noto (Italy), Onsala-26m (Sweden), Torun-15m (Poland), Simeiz (Ukraine), Bear Lakes (Russia), Seshan (China), Hartebeesthoek (S. Africa), Green Bank-43m, VLA and the VLBA antennas at HN, NL, PT, KP, LA, BR, OV (USA). The observations were made on 18 November, 1992, using the Mk2 recording system, and these were amongst the last to be correlated using the JPL-Caltech Block2 processor. The NRAO AIPS package was used for the data analysis.
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Das, Barnali, Poonam Chandra, and Gregg A. Wade. "Unravelling the complex magnetosphere of the B star HD 133880 via wideband observation of coherent radio emission." Monthly Notices of the Royal Astronomical Society 499, no. 1 (August 19, 2020): 702–9. http://dx.doi.org/10.1093/mnras/staa2499.
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ABSTRACT HD 133880 is one of the six hot magnetic stars known to produce coherent pulsed radio emission by the process of electron cyclotron maser emission (ECME). In this paper, we present observations of ECME from this star over a wide frequency range, covering nearly 300–4000 MHz with the Giant Metrewave Radio Telescope (GMRT) and the Karl G. Jansky Very Large Array (VLA). This study, which is the first of its kind, has led to the discovery of several interesting characteristics of the phenomenon and also of the host star. We find that the observable properties of ECME pulses, e.g. the time lag between right and left circularly polarized pulses, the amplitudes of the pulses, and their upper cut-off frequencies, appear to be dependent on the stellar orientation with respect to the line of sight. We suggest that all these phenomena, which are beyond the ideal picture, can be attributed to a highly azimuthally asymmetric matter distribution in the magnetosphere about the magnetic field axis, which is a consequence of both the high obliquity (the angle between rotation axis and the magnetic field axis) of the star and the deviation of the stellar magnetic field from a dipolar topology.
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Maselli, A., R. P. Kraft, F. Massaro, and M. J. Hardcastle. "Focusing on the extended X-ray emission in 3C 459 with a Chandra follow-up observation." Astronomy & Astrophysics 619 (November 2018): A75. http://dx.doi.org/10.1051/0004-6361/201833332.
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Aims. We investigated the X-ray emission properties of the powerful radio galaxy 3C 459 revealed by a recent Chandra follow-up observation carried out in October 2014 with a 62 ks exposure. Methods. We performed an X-ray spectral analysis from a few selected regions on an image obtained from this observation and also compared the X-ray image with a 4.9 GHz VLA radio map available in the literature. Results. The dominant contribution comes from the radio core but significant X-ray emission is detected at larger angular separations from it, surrounding both radio jets and lobes. According to a scenario in which the extended X-ray emission is due to a plasma collisionally heated by jet-driven shocks and not magnetically dominated, we estimated its temperature to be ∼0.8 keV. This hot gas cocoon could be responsible for the radio depolarization observed in 3C 459, as recently proposed also for 3C 171 and 3C 305. On the other hand, our spectral analysis and the presence of an oxygen K edge, blueshifted at 1.23 keV, cannot exclude the possibility that the X-ray radiation originating from the inner regions of the radio galaxy could be intercepted by some outflow of absorbing material intervening along the line of sight, as already found in some BAL quasars.
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Wootten, Alwyn, Mark Claussen, Kevin Marvel, and Bruce Wilking. "Proper motion of water masers near NGC1333-SVS13." Symposium - International Astronomical Union 206 (2002): 100–103. http://dx.doi.org/10.1017/s007418090022216x.
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VLBA observations of water masers toward the region of NGC1333 near SVS13, the driving source for the well-known Herbig-Haro objects HH7-11, are reported. Maser emission was observed over four epochs spaced by three weeks during late 1998. SVS13 is associated with the millimeter continuum SED Class I source SSV13A1. High resolution CO observations have secured the association of the flow with the continuum object on arc-second scales. A 1998 Aug 12 VLA observation places the blueshifted masers within 80 AU (0.2) of the 2.7 mm position for A1 reported from BIMA. We report observations of two groups of masers, one redshifted by about 6 km s−1 and one blueshifted by about 2-3 km s−1, separated by about 100 AU in projected distance along position angle 21 degrees. Redshifted masers were present only in the latter two epochs. During all epochs, an arclike structure was present with similar morphology; over time this structure moved relative to the southernmost blue maser toward the southeast, roughly along the position angle defined by the Herbig-Haro objects, with a proper motion of about 13 km s−1. Both redshifted and blueshifted masers are clearly part of the same lobe of the flow; their observed Doppler shifts are artifacts of the opening angle of the flow. Our data suggest that the opening angle is about 10°. We measure lower expansion velocities and a wider opening angle than has been found in some other flows near Class 0 SED objects, perhaps indicating that the flows open and slow as they age.
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Lee, Minju, Kenta Suzuki, Kotaro Kohno, Yoichi Tamura, Daisuke Iono, Bunyo Hatsukade, Kouichiro Nakanishi, et al. "Jansky VLA S-band view of Hα emitters (HAEs) associated with a protocluster 4C23.56 at z = 2.5." Proceedings of the International Astronomical Union 10, S309 (July 2014): 287–88. http://dx.doi.org/10.1017/s1743921314009892.
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AbstractWe present recent results on Karl Jansky Very Large Array (JVLA) deep S-band (2-4 GHz) observation towards a protocluster 4C23.56 at redshift z ∼ 2.5. The protocluster 4C23.56 is known to have a significant over density (∼ 5 times) of star-burst galaxies selected to be Hα line-bright by a Subaru narrow band imaging. Now we have found 25 HAEs associated with the protocluster. These starburst HAEs are likely to become massive ellipticals at z = 0 in a cluster. Various other galaxy populations also reside in this field and the fact makes the field very unique as a tool to understand galaxy formation in a over dense region. Subsequent deep 1100-μm continuum surveys by the ASTE 10-m dish have discovered that several submillimeter bright galaxies (SMGs) coincide with HAEs, suggesting HAEs undergoing dusty starbursts. As star formation rates (SFRs) of HAEs might have been underestimated, we use radio being resistant to dust extinction. We investigate the correlation between SFR1.4 GHz and SFRHα for radio index α = 0.8 to see if the correlation holds for the sources and to check the number of dusty star forming galaxies. Our final results will allow us to evaluate quantitatively how the galaxy formation channel may be different under the condition of over-densities.
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Yang, Meng, Ling Zhu, Anne-Marie Weijmans, Glenn van de Ven, Nicholas Boardman, Raffaella Morganti, and Tom Oosterloo. "Mapping the dark matter halo of early-type galaxy NGC 2974 through orbit-based models with combined stellar and cold gas kinematics." Monthly Notices of the Royal Astronomical Society 491, no. 3 (November 26, 2019): 4221–31. http://dx.doi.org/10.1093/mnras/stz3293.
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ABSTRACT We present an orbit-based method of combining stellar and cold gas kinematics to constrain the dark matter profile of early-type galaxies. We apply this method to early-type galaxy NGC 2974, using Pan-STARRS imaging and SAURON stellar kinematics to model the stellar orbits, and introducing H i kinematics from VLA observation as a tracer of the gravitational potential. The introduction of the cold gas kinematics shows a significant effect on the confidence limits of especially the dark halo properties: we exclude more than $95{{\ \rm per\ cent}}$ of models within the 1σ confidence level of Schwarzschild modelling with only stellar kinematics, and reduce the relative uncertainty of the dark matter fraction significantly to $10{{\ \rm per\ cent}}$ within 5Re. Adopting a generalized Navarro–Frenk–White (NFW) dark matter profile, we measure a shallow cuspy inner slope of $0.6^{+0.2}_{-0.3}$ when including the cold gas kinematics in our model. We cannot constrain the inner slope with the stellar kinematics alone.
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Borkowska, Sylwia, Agata Poniewierska-Baran, Gabriela Schneider, Daniel Pedziwiatr, Malwina Suszynska, Janina Ratajczak, Magdalena Kucia, and Mariusz Z. Ratajczak. "Novel Evidence That, in Addition to Proteolytic Enzymes, Lipolytic Enzymes Are Involved in Mobilization of Hematopoietic Stem/Progenitor Cells (HSPCs) - an Important Pro-Mobilizing Role Identified for Hematopoietic-Specific Phospholipase C (PLCβ2)." Blood 124, no. 21 (December 6, 2014): 2448. http://dx.doi.org/10.1182/blood.v124.21.2448.2448.
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Abstract Background . Hematopoietic stem/progenitor cells (HSPCs) express the chemokine receptor CXCR4 and the very late antigen 4 receptor (VLA-4, also known as alpha4beta1 integrin) on their cell surface and are retained in bone marrow (BM) niches by interaction of these receptors with their respective ligands, α-chemokine stromal-derived growth factor 1 (SDF-1) and vascular adhesion molecule 1 (VCAM-1, also known as CD106), which are expressed by cells in the BM microenvironment (e.g., osteoblasts and fibroblasts). Mobilization studies employing small molecule antagonists of CXCR4 or VLA-4 indicate the importance of both axes in retention of HSPCs in the BM microenvironment. Furthermore, it has been postulated that a crucial role in the mobilization process plays activation of a proteolytic microenvironment (J Clin Invest. 2003;111:187-96) and complement cascade (ComC) (Blood 2004;103:2071-8) in the BM microenvironment. However, to our surprise no attention has been paid so far to the role of lipolytic enzymes. Phospholipase C (PLC) is an enzyme released by neutrophils that cleaves the phosphoglycerol bond in glycosylphospahtidylinositol (GPI anchor), a glycolipid that is attached to the C-termini of several important proteins during posttranslational modification. GPI-linked proteins are thought to be preferentially located in lipid rafts. The most important GPI-anchored proteins include VCAM-1, complement inhibitors CD55 and CD59, and uPAR. We have reported that for retention of HSPCs in BM, both CXCR4 and VLA-4 have to be incorporated into membrane lipid rafts (Blood 2005;105:40-48). Hypothesis . Based on our previous observation that the HSPCs of paroxysmal nocturnal hemoglobinuria patients show defective retention in BM due to lack of functional GPI anchor (Leukemia 2012; 26:1722—5) we have hypothesized that PLC in normal BM may facilitate mobilization of HSPCs by perturbing expression of GPI anchor, which is so crucial for proper retention of HSPCs in BM. Materials and Methods . PLC activity has been measured by ELISA in the BM of mobilized mice as well in conditioned media from neutrophils exposed to several pro-mobilizing factors (G-CSF, AMD3100, C3a, C5a, desArgC5a, and S1P). We also tested the effect of PLC on the expression of VCAM-1 on BM-derived stroma and CD55 and CD59 antigens on BM mononuclear cells. The effect of PLC on incorporation of CXCR4 and VLA-4 into membrane lipid rafts has been studied by confocal microscopy employing murine Sca-1+ and human CD34+ cells. Here, to test our hypothesis, mobilization studies using AMD3100 and G-CSF have been performed in PLCβ2-KO (PLCβ2–/–) mice and their wild type (WT) littermates. Results . Our data indicate that the PLC level increases in BM during mobilization and is released from neutrophils in response to several pro-mobilization factors (G-CSF, AMD3100, C3a, C5a, desArgC5a, and S1P). PLC efficiently cleaves VCAM-1 expressed on BM stromal cells and thus perturbs the VCAM-1–VLA4 interaction as well as removes CD55 and CD59 from BM mononuclear cells, which enhances the pro-mobilizing effects of the ComC. PLC also inhibits lipid raft formation on HSPCs and by this means impairs the normal BM-retention function of CXCR4 and VLA-4. Finally, what is most important, we observed a mobilization defect in PLCβ2–/– mice, as evaluated by the number of mobilized leucocytes, SKL cells, and CFU-GM. Conclusions . We have established for the first time that, in addition to proteolytic enzymes, lipolytic enzymes, including LPC, are upregulated in the BM microenvironment, and that PLC promotes mobilization of HSPCs by perturbing the BM-retention function of GPI-anchored proteins. These data support an important role for GPI anchor-dependent proteins in the retention of HSPCs in BM niches. Disclosures No relevant conflicts of interest to declare.
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Belladitta, S., A. Moretti, A. Caccianiga, C. Spingola, P. Severgnini, R. Della Ceca, G. Ghisellini, et al. "The first blazar observed at z > 6." Astronomy & Astrophysics 635 (March 2020): L7. http://dx.doi.org/10.1051/0004-6361/201937395.
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We present the discovery of PSO J030947.49+271757.31, the radio brightest (23.7 mJy at 1.4 GHz) active galactic nucleus (AGN) at z > 6.0. It was selected by cross-matching the NRAO VLA Sky Survey and the Panoramic Survey Telescope and Rapid Response System PS1 databases and its high-z nature was confirmed by a dedicated spectroscopic observation at the Large Binocular Telescope. A pointed Neil Gehrels Swift Observatory XRT observation allowed us to measure a flux of ∼3.4 × 10−14 erg s−1 cm−2 in the [0.5–10] keV energy band, which also makes this object the X-ray brightest AGN ever observed at z > 6.0. Its flat radio spectrum (ανr < 0.5), very high radio loudness (R > 103), and strong X-ray emission, compared to the optical, support the hypothesis of the blazar nature of this source. Assuming that this is the only blazar at this redshift in the surveyed area of sky, we derive a space density of blazars at z ∼ 6 and with M1450 Å < −25.1 of 5.5+11.2−4.6 × 10−3 Gpc−3. From this number, and assuming a reasonable value of the bulk velocity of the jet (Γ = 10), we can also infer a space density of the entire radio-loud AGN population at z ∼ 6 with the same optical/UV absolute magnitude of 1.10+2.53−0.91 Gpc−3. Larger samples of blazars will be necessary to better constrain these estimates.
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Michail, Joseph M., Farhad Yusef-Zadeh, and Mark Wardle. "Detection of a 20-min time lag observed from Sgr A* between 8 and 10 GHz with the VLA." Monthly Notices of the Royal Astronomical Society 505, no. 3 (May 27, 2021): 3616–23. http://dx.doi.org/10.1093/mnras/stab1529.
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ABSTRACT We report the detection and analysis of a radio flare observed on 17 April 2014 from Sgr A* at 9 GHz using the VLA in its A-array configuration. This is the first reported simultaneous radio observation of Sgr A* across 16 frequency windows between 8 and 10 GHz. We cross-correlate the lowest and highest spectral windows centred at 8.0 and 9.9 GHz, respectively, and find the 8.0 GHz light-curve lagging $18.37^{+2.17}_{-2.18}$ min behind the 9.9 GHz light curve. This is the first time lag found in Sgr A*’s light curve across a narrow radio frequency bandwidth. We separate the quiescent and flaring components of Sgr A* via flux offsets at each spectral window. The emission is consistent with an adiabatically expanding synchrotron plasma, which we fit to the light curves to characterize the two components. The flaring emission has an equipartition magnetic field strength of 2.2 Gauss, size of 14 Schwarzschild radii, average speed of 12 000 km s−1, and electron energy spectrum index (N(E) ∝ E−p), p = 0.18. The peak flare flux at 10 GHz is approximately 25 per cent of the quiescent emission. This flare is abnormal as the inferred magnetic field strength and size are typically about 10 Gauss and few Schwarzschild radii. The properties of this flare are consistent with a transient warm spot in the accretion flow at a distance of 10–100 Schwarzschild radii from Sgr A*. Our analysis allows for independent characterization of the variable and quiescent components, which is significant for studying temporal variations in these components.
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Nandakumar, Meera, and Prasun Dutta. "Evidence of large-scale energy cascade in the spiral galaxy NGC 5236." Monthly Notices of the Royal Astronomical Society 496, no. 2 (June 13, 2020): 1803–10. http://dx.doi.org/10.1093/mnras/staa1651.
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ABSTRACT Turbulence plays an important role in the structure and dynamics of the galaxy and influences various processes therein including star formation. In this work, we investigate the large-scale turbulence properties of the external spiral galaxy NGC 5236. We combine the Very Large Array (VLA) multiconfiguration archival data with the new GMRT observation to estimate the column density and line-of-sight velocity fluctuation power spectra for this galaxy over almost two decades of length scales. The energy input scale to the interstellar medium turbulence is found to be around 6 kpc. Power spectra of the two-dimensional turbulence in the galaxy’s disc follow a power law with a slope −1.23 ± 0.06 for the column density and −1.91 ± 0.08 for the line-of-sight velocity. The measured power spectra slopes strongly suggest in favour of a compressive forcing with a steady energy input of ∼7 × 10−11 erg cm −2 s−1. We conclude that much of these originate from the gravitational instabilities and self-gravity in the disc. This is the first and most comprehensive study of turbulence statistics for any external spiral galaxy.
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Schulz, R., R. Morganti, K. Nyland, Z. Paragi, E. K. Mahony, and T. Oosterloo. "Mapping the neutral atomic hydrogen gas outflow in the restarted radio galaxy 3C 236." Astronomy & Astrophysics 617 (September 2018): A38. http://dx.doi.org/10.1051/0004-6361/201833108.
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The energetic feedback that is generated by radio jets in active galactic nuclei (AGNs) has been suggested to be able to produce fast outflows of atomic hydrogen (H I) gas, which can be studied in absorption at high spatial resolution. We have used the Very Large Array (VLA) and a global very long baseline interferometry (VLBI) array to locate and study in detail the H I outflow discovered with the Westerbork Synthesis Radio Telescope (WSRT) in the restarted radio galaxy 3C 236. Based on the VLA data, we confirm a blueshifted wing of the H I with a width of ~1000 km s−1. This H I outflow is partially recovered by the VLBI observation. In particular, we detect four clouds with masses of 0.28 − 1.5 × 104M⊙ with VLBI that do not follow the regular rotation of most of the H I. Three of these clouds are located, in projection, against the nuclear region on scales of ≲40 pc, while the fourth is cospatial to the southeast lobe at a projected distance of ~270 pc. Their velocities are between 150 and 640 km s−1 blueshifted with respect to the velocity of the disk-related H I. These findings suggest that the outflow is at least partly formed by clouds, as predicted by some numerical simulations, and that it originates already in the inner (few tens of pc) region of the radio galaxy. Our results indicate that the entire outflow might consist of many clouds, possibly with comparable properties as those clearly detected, but distributed at larger radii from the nucleus where the lower brightness of the lobe does not allow us to detect them. However, we cannot rule out a diffuse component of the outflow. Because 3C 236 is a low-excitation radio galaxy, it is less likely that the optical AGN is able to produce strong radiative winds. This leaves the radio jet as the main driver for the H I outflow.
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Keto, Eric, and William Jeffrey. "The three dimensional structure of astronomical sources through optimal inversion." International Astronomical Union Colloquium 131 (1991): 228–32. http://dx.doi.org/10.1017/s0252921100013361.
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AbstractWe explore the application of optimal inversion techniques to astronomical data with a goal of developing a set of procedures for the determination of the three dimensional structure of astronomical sources. Astronomical data present a particularly difficult problem in inversion because: In any observation, 3 of 6 spatial and velocity dimensions are lost in projection onto the plane of the sky and the line of sight velocity. In any inversion, we would like to solve for a number of physical parameters. Generally, these parameters are closely related in their effect on the single observable, the sky brightness.The dimensional deficiency leaves us with an unavoidably large degree of ambiguity (non-uniqueness) in any solution, while the inter-related parameters lead to a high probability of correlated errors and hence instability in the presence of to noise.We show how constraints of symmetry and smoothness source allow us to handle an inversion with an insufficiently sampled data base and mutually dependent solution parameters (mathematically ill-posed and ill-conditioned). The constraints represent a priori information incorporated into the solution; thus very highly constrained inversions are similar to model fitting. In any case the inversion procedure provides us with quantitative statistics on the goodness of fit which may be used to assess the degree of ambiguity in a particular model, and the expected errors and cross-correlated errors on the parameters defining the source structure.We briefly discuss the background and motivation, and outline the procedure in general terms. We refer to papers published in the Ap. J. where different aspects of the inversion are applied to observational data bases collected at the VLA.
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Thölken, Sophia, Thomas H. Reiprich, Martin W. Sommer, and Naomi Ota. "Discovery of large scale shock fronts correlated with the radio halo and radio relic in the A2163 galaxy cluster." Astronomy & Astrophysics 619 (November 2018): A68. http://dx.doi.org/10.1051/0004-6361/201834053.
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Context. Galaxy clusters form at the intersections of the filamentary large scale structure in merging events and by the accretion of matter along these filaments. Imprints of these formation processes should be visible in the intracluster medium and can arise in shock fronts, which are detectable via discontinuities in, for example, the gas temperature and density profiles. However, relatively few observational examples of prominent shocks have been detected in X-rays so far. Aims. In this study, we investigate the X-ray properties of the intracluster gas and the radio morphology of the extraordinary cluster A2163. This cluster shows an irregular morphology in various wavelengths and has one of the most luminous and extended radio halos known. Additionally, it is one of the hottest clusters known. We aim to measure the temperature and density profiles in two azimuthal directions to search for the presence of shock fronts. Methods. We performed a spectral analysis of data from two Suzaku observations, one in the north-east (NE) and one in the southwest (SW) direction of A2163, and used archival XMM-Newton data to remove point sources in the field of view. We deprojected the temperature and density profiles and accounted for the Suzaku point spread function. From the detected discontinuities in the density and temperature profiles, we estimated the Mach numbers and velocities of the shock fronts. To compare our findings in the X-ray regime with the radio emission, we obtained radio images of the cluster from an archival Very Large Array (VLA) observation at 20 cm. Results. We identify three shock fronts in A2163 in our spectral X-ray study. A clear shock front lies in the NE direction at a distance of 1.4 Mpc from the center, with a Mach number of M = 1.7+0.3−0.2, estimated from the temperature discontinuity. This shock coincides with the position of a known radio relic. We identify two additional shocks in the SW direction, one with M = 1.5+0.5−0.3 at a distance of 0.7 Mpc, which is likely related to a cool core remnant, and a strong shock with M = 3.2+0.6−0.7 at a distance of 1.3 Mpc, which also closely matches the radio contours. The complex structure of A2163 as well as the different Mach numbers and shock velocities suggest a merging scenario with two unequal merging constituents, where two shock fronts emerged at an early stage of the merger and traveled outwards while an additional shock front developed in front of the merging cluster cores.
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Wang, Jianhua, Russell Taichman, Younghun Jung, Aaron Havens, Yanxi Sun, Jingcheng Wang, and Taocong Jin. "Cell-to-Cell Contact Is Critical for the Survival of Hematopoietic Progenitor Cells on Osteoblasts." Blood 104, no. 11 (November 16, 2004): 1285. http://dx.doi.org/10.1182/blood.v104.11.1285.1285.
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Abstract Osteoblasts constitute part of the stromal cell support system in marrow for hematopoiesis, however little is known as to how they interact with hematopoietic stem cells (HSCs). In vitro studies have demonstrated that the survival of HSCs in co-culture with osteoblasts requires intimate cell-to-cell contact. This suggests that the osteoblast-derived factor(s) that supports stem cell activities are either produced in very small quantities, are rapidly turned over, may be membrane-anchored and/or requires the engagement of cell-cell adhesion molecules yet to be determined. In the present report we found that survival of hematopoietic progenitor cells on osteoblasts is dependent upon the engagement of VLA-4 (α4β1) and VLA-5 (α5ß1) receptors using function blocking antibodies. Surprisingly, cell-to-cell contact is not absolutely required to support progenitor activity, but does not require receptor-ligand engagement of the VLA-4 and LFA-1 complexes, which can in part be replaced through the use of recombinant ligands (fibronectin, ICAM-1, VCAM-1). Moreover conditioned once these receptors were engaged, medium derived from HSCs grown on osteoblasts ligands supported significantly greater hematopoietic progenitors in vitro than did osteoblast-conditioned or HSC-conditioned medium alone. As an initial attempt to identify the activity we examined which genes are activated following the establishment of osteoblast-CD34+ cell co-cultures nine separate co-cultures were establsihed and the RNA was pooled and analyized on Affymetrix HG-U133A chips at 24 hours. Initially our analysis revealed that there were 259 genes that are up regulated at 24 hours, and 14 genes that are down regulated. Inspection revealed that 30 of these signals were repeated at least once suggesting that 206 genuine gene candidates were differentially expressed resulting from the co-culture. A significant proportion of the differentially expressed cDNAs represent intracellular signaling ligands 16.5% (n=34) and cell surface receptors 13.5% (n=28). Molecules associated with assembly of the extra cellular matrix or its degradation comprised 7.2% (n=15) of the differentially up regulated molecules. Molecules associated with intracellular signaling, novel sequences and intermediate metabolism comprised the majority of the remaining activities. Amoung the candidates of extra cellular signaling molecules, we noted that IL-6, LIF, MIP-1alpha and SDF-1 were identified in the microarray analysis. This observation was most gratifying as we had previously reported that IL-6, LIF and MIP-1α activities are critical components of an HSC-osteoblast microenvironment. Other notable cytokine messages for BMP-2, CCL7, FGF2b, GRO1α, GRO3, IGF1, IL1ß, IL-8, IL-11, LIF, PDGF-D and the receptors for CCL7 (CCR7). Elevations in mRNA for fibronectin, lysine hydroxylase-like proteins, laminin and Type I collagen suggest that the presence of hematopoietic cells also induces osteoblastic activities. While the identity of those molecules present in the co-cultured medium remain to be identified, the data suggests that hematopoietic cells cooperate with osteoblasts to assemble the various marrow microenvironments by directing the synthesis of osteoblast-derived cytokines to improve HSC survival.