1,726,288 research outputs found
Messier 106 - NGC 4258
No full textEsta imagem apresenta a galáxia Messier 106, também conhecida como NGC 4258. Ela está na constelação Cana Venatici, há cerca de 23 milhões de anos-luz de distância do planeta TerraComponente Curricular::Educação Superior::Ciências Exatas e da Terra::Astronomi
Messier 106 - NGC 4258
No full textEsta imagem apresenta a galáxia Messier 106, também conhecida como NGC 4258. Ela está na constelação Cana Venatici, há cerca de 23 milhões de anos-luz de distância do planeta TerraComponente Curricular::Educação Superior::Ciências Exatas e da Terra::Astronomi
Messier 106 - NGC 4258
No full textEsta imagem apresenta a galáxia Messier 106, também conhecida como NGC 4258. Ela está na constelação Cana Venatici, há cerca de 23 milhões de anos-luz de distância do planeta TerraComponente Curricular::Educação Superior::Ciências Exatas e da Terra::Astronomi
Messier 106 - NGC 4258
No full textEsta imagem apresenta a galáxia Messier 106, também conhecida como NGC 4258. Ela está na constelação Cana Venatici, há cerca de 23 milhões de anos-luz de distância do planeta TerraComponente Curricular::Educação Superior::Ciências Exatas e da Terra::Astronomi
Block Card 4258 Foxglove Road
No full textThis image was produced by the Auditor's Office in Lucas County, Ohio for tax assessment purposes. Associated dates are approximate. Descriptive terms related to this photograph include: Ranch houses | Dwelling | Harvest Lane Home Sites (Toledo, Ohio) | Franklin Park Area (Toledo, Ohio) | Trilby Area (Toledo, Ohio)) | 4258 Foxglove Road (Toledo, Ohio
NGC 4258: a jet-dominated low-luminosity AGN?
No full textLow-luminosity AGNs (LLAGNs) are a very important class of sources since they occupy a significant fraction of local galaxies. Their spectra differ significantly from the canonical luminous AGNs, most notably by the absence of the "big blue bump". In the present paper, taking a typical LLAGN-NGC-4258 as an example, we investigate the origin of their spectral emission. The observational data of NGC 4258 is extremely abundant, including water maser emission, putting very strict constraints to its theoretical models. The infrared (IR) spectrum is well described by a steep power-law form f / , and may extend to the optical/UV band. Up until now there is no model which can explain such a steep spectrum, and we here propose a coupled jet plus accretion disk model for NGC 4258. The accretion disk is composed of an inner ADAF (or radiatively inefficient accretion flow) and an outer standard thin disk. A shock occurs when the accretion ow is ejected out of the ADAF to form the jet near the black hole, accelerating the electrons into a power-law energy distribution. The synchrotron and self-Comptonized emission from these electrons greatly dominates over the underlying accretion disk and can well explain the spectrum ranging from IR to X-ray bands. The further propagation of the shocked gas in the jet can explain the at radio spectrum of NGC 4258. Several predictions of our model are presented for testing against future observations, and we briefly discuss the application of the model to other LLAGNs
Decreto n. 4258, 21 jan. 1929, RS.
No full textO original deste item encontra-se depositado na Biblioteca da Assembleia Legislativa do Rio Grande do SUl (ALERGS). Item digitalizado por Janine Garcia dos Santos.Decreto n. 4258, de 21 de janeiro de 1929. Approva o regulamento da Directoria Geral de Instrução Pública
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
NGC 4258 : A jet-dominated low-luminosity AGN?
No full textLow-luminosity AGNs (LLAGNs) are a very important class of sources since they occupy a significant fraction of local galaxies. Their spectra differ significantly from the canonical luminous AGNs, most notably by the absence of the "big blue bump". In the present paper, taking a typical LLAGN-NGC 4258-as an example, we investigate the origin of their spectral emission. The observational data of NGC 4258 is extremely abundant, including water maser emission, putting very strict constraints to its theoretical models. The infrared (IR) spectrum is well described by a steep power-law form f(nu) proportional to nu(-1.4), and may extend to the optical/UV band. Up until now there is no model which can explain such a steep spectrum, and we here propose a coupled jet plus accretion disk model for NGC 4258. The accretion disk is composed of an inner ADAF (or radiatively inefficient accretion flow) and an outer standard thin disk. A shock occurs when the accretion flow is ejected out of the ADAF to form the jet near the black hole, accelerating the electrons into a power-law energy distribution. The synchrotron and self-Comptonized emission from these electrons greatly dominates over the underlying accretion disk and can well explain the spectrum ranging from IR to X-ray bands. The further propagation of the shocked gas in the jet can explain the flat radio spectrum of NGC 4258. Several predictions of our model are presented for testing against future observations, and we briefly discuss the application of the model to other LLAGNs
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