Exploring the DR7 Quasar Catalog Session 2 PDF

Exploring the DR7 Quasar Catalog Session 2 by Marim Saad Quasars A quasar (quasi-stellar object) is an extremely active and luminous type of active galactic nucleus (AGN). Quasars are a subclass of active galactic nuclei (AGNs), extremely luminous gal...

Exploring the DR7 Quasar Catalog Session 2 by Marim Saad Quasars A quasar (quasi-stellar object) is an extremely active and luminous type of active galactic nucleus (AGN). Quasars are a subclass of active galactic nuclei (AGNs), extremely luminous galactic cores where gas and dust falling into a supermassive black hole emit electromagnetic radiation across the entire electromagnetic spectrum. Quasars are amongst the most luminous objects in the known Universe, typically emitting thousands of times lighter than the entire Milky Way. 1. Understanding Redshift Redshift Basics 1 In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and simultaneous increase in frequency and energy, is known as a negative redshift, or blueshift. The terms derive from the colors red and blue which form the extremes of the visible light spectrum, indicating the object is moving away from the observer. 2 Examples Examples of strong redshirting are a gamma ray perceived as an X-ray, or initially visible light perceived as radio waves. Subtler redshifts are seen in the spectroscopic observations of astronomical objects and are used in terrestrial technologies such as Doppler radar and radar guns. 3 physical processes Other physical processes exist that can lead to a shift in the frequency of electromagnetic radiation, including scattering and optical effects; however, the resulting changes are distinguishable from (astronomical) redshift. Luminosity Measures 2. Bolometric Luminosity “LOGLBOL”: 3. Monochromatic Luminosity LOGL5100 , LOGL3000 , LOGL1350: ❑ Bolometric luminosity (in units of erg/s); using bolometric corrections derived from the composite SED “Spectral Density Distibution” ❑ The luminosity at specific wavelengths, such ❑ The total energy radiated by an object at as L5100, L3000, and L1350, providing all wavelengths, usually given in joules per second insights into the spectral energy distribution. (identical to watts). 4. Radio Loudness “R_6CM_2500A”: It is the ratio between the radio radiation at 6 cm wavelength to the optical radiation at 2500 A wavelength If R>10 “ the source is radio Loud” If R