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- Algaba, Juan-Carlos, et al.
(författare)
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Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign
- 2021
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 911:1
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Forskningsöversikt (refereegranskat)abstract
- In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass ∼6.5 × 109 M o˙. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87's spectrum. We can exclude that the simultaneous γ-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the γ-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded.
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| 4. |
- Morokuma, Tomoki, et al.
(författare)
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OISTER optical and near-infrared monitoring observations of peculiar radio-loud active galactic nucleus SDSSJ110006.07+442144.3
- 2017
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Ingår i: Nippon Tenmon Gakkai obun kenkyu hokoku. - : Oxford University Press (OUP). - 0004-6264. ; 69:5
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Tidskriftsartikel (refereegranskat)abstract
- We present monitoring campaign observations at optical and near-infrared (NIR) wavelengths for a radio-loud active galactic nucleus (AGN) at z = 0.840, SDSSJ110006.07+442144.3 (hereafter, J1100+4421), which was identified during a flare phase in late 2014 February. The campaigns consist of three intensive observing runs from the discovery to 2015 March, mostly within the scheme of the OISTER collaboration. Optical-NIR light curves and simultaneous spectral energy distributions (SEDs) are obtained. Our measurements show the strongest brightening in 2015 March. We found that the optical-NIR SEDs of J1100+4421 show an almost steady shape despite the large and rapid intranight variability. This constant SED shape is confirmed to extend to similar to 5 mu m in the observed frame using the archival WISE data. Given the lack of absorption lines and the steep power-law spectrum of alpha(upsilon) similar to -1.4, where f(v) proportional to v(alpha upsilon), synchrotron radiation by a relativistic jet with no or small contributions from the host galaxy and the accretion disk seemsmost plausible as an optical-NIR emission mechanism. The steep optical-NIR spectral shape and the large amplitude of variability are consistent with this object being a low.peak jet-dominated AGN. In addition, sub-arcsecond resolution optical imaging data taken with Subaru Hyper Suprime-Cam does not show a clear extended component and the spatial scales are significantly smaller than the large extensions detected at radio wavelengths. The optical spectrum of a possible faint companion galaxy does not show any emission lines at the same redshift, and hence a merging hypothesis for this AGN-related activity is not supported by our observations.
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| 5. |
- Nishitsuka, Koichi, et al.
(författare)
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Hyaluronan production regulation from porcine hyalocyte cell line by cytokines
- 2007
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Ingår i: Experimental Eye Research. - : Elsevier BV. - 0014-4835 .- 1096-0007. ; 85:4, s. 539-545
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study were to establish a cell line derived from porcine hyalocytes and to investigate the regulation of hyaluronan (HA) synthesis in response to cytokines. After 50 passages of the cells derived from porcine vitreous tissue, a cell line was generated. The immortalized cells showed fibroblastic morphology. The cell doubling time was 56.9h. In the mRNA level, the cells expressed plate-derived growth factor (PDGF) alpha receptor, PDGF beta receptor, transforming growth factor-beta (TGF-beta) type I receptor, TGF-beta type II receptor, CD44, collagen type I, collagen type II, glial fibrillary acidic protein (GFAP), hyaluronan synthase (HAS) 2, HAS 3 and beta-actin. In the protein level, GFAP was expressed in this cell line. S-100 protein and cytokeratin were not detected. Stimulation with TGF-beta1 and/or PDGF-BB induced a marked increase in the expression level of HAS2 mRNA, and induced HA production. TGF-beta1 stimulated HAS2 expression through the signal transduction pathway including Smad 2,3,4. In summary, this report constitutes the first successful immortalization of porcine hyalocyte cells. The production of HA was induced from the generated porcine hyalocyte cell line under the stimulation of TGF-beta1 and/or PDGF-BB, which may be related to the pathogenesis of proliferative membrane formation in proliferative vitreo-retinal diseases.
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| 7. |
- Takahashi, Yoshinori, et al.
(författare)
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Hyaluronan fragments induce endothelial cell differentiation in a CD44- and CXCL1/GRO1-dependent manner.
- 2005
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Ingår i: J Biol Chem. - 0021-9258.
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Tidskriftsartikel (refereegranskat)abstract
- Hyaluronan is a glycosaminoglycan of the extracellular matrix. In tumors and during chronic inflammatory diseases hyaluronan is degraded to smaller fragments which are known to stimulate endothelial cell differentiation. In this study we have compared the molecular mechanisms through which hyaluronan dodecasaccharides (HA12), and the known angiogenic factor, fibroblast growth factor 2 (FGF-2), induce capillary endothelial cell sprouting in a 3D collagen gel. The gene expression profiles of unstimulated and HA12 or FGF-2 stimulated endothelial cells were compared using a microarray analysis approach. The data revealed that both FGF-2 and HA12 promoted endothelial cell morphogenesis in a process depending on the expression of ornithine decarboxylase (Odc) and ornithine decarboxylase antizyme inhibitor (Oazi) genes. Among the genes selectively upregulated in response to HA12 was the chemokine CXCL1/GRO1 gene. The notion that the induction of CXCL1/GRO1 is of importance for HA12-induced endothelial cell sprouting was supported by the fact that morphogenesis was inhibited by antibodies specifically neutralizing the CXCL1/GRO1 protein product. HA12-stimulated endothelial cell differentiation was exerted via binding to CD44, since it was inhibited by antibodies blocking CD44 function. Our data show that hyaluronan fragments and FGF-2 affect endothelial cell morphogenesis by induction of overlapping, but also distinct sets of genes.
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