Active Galactic Nuclei Export

@incollection{citeulike:3790138, abstract = {The light of normal galaxies in the optical and near infrared part of the spectrum is dominated by stars, with small contributions by gas and dust. This is thermal radiation since the emitting plasma in stellar atmospheres is basically in thermodynamical equilibrium. To a first approximation, the spectral properties of a star can be described by a Planck spectrum whose temperature depends on the stellar mass and the evolutionary state of the star. As we have seen in Sect. 3.9, the spectrum of galaxies can be described quite well as a superposition of stellar spectra. The temperature of stars varies over a relatively narrow range. Only few stars are found with T ≳ 40 000 K, and those with T ≲ 3000 K hardly contribute to the spectrum of a galaxy, due to their low luminosity. Therefore, as a rough approximation, the light distribution of a galaxy can be described by a superposition of Planck spectra from a temperature range that covers about one decade. Since the Planck spectrum has a very narrow energy distribution around its maximum at h Pν ∼ 3k BT, the spectrum of a galaxy is basically confined to a range between ∼ 4000 \r{A} and ∼ 20 000 \r{A}. If the galaxy is actively forming stars, young hot stars extend this frequency range to higher frequency, and the thermal radiation from dust, heated by these new-born stars, extends the emission to the far-infrared.}, citeulike-article-id = {3790138}, citeulike-linkout-0 = {http://dx.doi.org/10.1007/978-3-540-33175-9_5}, citeulike-linkout-1 = {http://www.springerlink.com/content/h2l836u706w44353}, doi = {10.1007/978-3-540-33175-9_5}, journal = {Extragalactic Astronomy and Cosmology}, keywords = {agn, book, review}, pages = {175--222}, posted-at = {2008-12-15 19:07:45}, priority = {2}, title = {Active Galactic Nuclei}, url = {http://dx.doi.org/10.1007/978-3-540-33175-9_5}, year = {2006} }

TY - CHAP ID - citeulike:3790138 L3 - citeulike-article-id:3790138 N2 - The light of normal galaxies in the optical and near infrared part of the spectrum is dominated by stars, with small contributions by gas and dust. This is thermal radiation since the emitting plasma in stellar atmospheres is basically in thermodynamical equilibrium. To a first approximation, the spectral properties of a star can be described by a Planck spectrum whose temperature depends on the stellar mass and the evolutionary state of the star. As we have seen in Sect. 3.9, the spectrum of galaxies can be described quite well as a superposition of stellar spectra. The temperature of stars varies over a relatively narrow range. Only few stars are found with T ≳ 40 000 K, and those with T ≲ 3000 K hardly contribute to the spectrum of a galaxy, due to their low luminosity. Therefore, as a rough approximation, the light distribution of a galaxy can be described by a superposition of Planck spectra from a temperature range that covers about one decade. Since the Planck spectrum has a very narrow energy distribution around its maximum at h Pν ∼ 3k BT, the spectrum of a galaxy is basically confined to a range between ∼ 4000 Å and ∼ 20 000 Å. If the galaxy is actively forming stars, young hot stars extend this frequency range to higher frequency, and the thermal radiation from dust, heated by these new-born stars, extends the emission to the far-infrared. JF - Extragalactic Astronomy and Cosmology EP - 222 TI - Active Galactic Nuclei SP - 175 KW - agn KW - book KW - review PY - 2006/// UR - http://dx.doi.org/10.1007/978-3-540-33175-9_5 ER -