Cosmic Odyssey: How Intrepid Astronomers at Palomar Observatory Changed Our View of the Universe by Linda Schweizer

Author:Linda Schweizer [Schweizer, Linda]
Language: eng
Format: epub
Tags: science, Space Science, Astronomy, Physics, Astrophysics, General
ISBN: 9780262359658
Google: 9M7tDwAAQBAJ
Publisher: MIT Press
Published: 2020-11-24T00:33:20.262013+00:00

ULTRALUMINOUS INFRARED GALAXIES: CELEBRITY ROCK STARS

Sanders found himself at the nexus of unique observational opportunities as data were becoming available over an increasingly wide range of wavelengths. Following a hunch, he decided to select and analyze what he whimsically termed the “top ten” most luminous infrared galaxies from the IRAS bright galaxy survey.148 At first, these 10 objects appeared to be nondescript: they did not appear in any of the usual lists of galaxies, such as the NGC catalog or optical spectroscopic surveys. Instead, they were included in Fritz and Margrit Zwicky’s 1971 Catalogue of Selected Compact Galaxies and of Post-eruptive Galaxies149 and Chip Arp’s Atlas of Peculiar Galaxies. Optical counterparts of the host galaxies could be seen on prints of the Palomar Observatory Sky Survey. While Soifer had relied on published classifications of galaxies for his plot of bolometric luminosities, Sanders determined the morphologies from scratch. He imaged each of his 10 objects with the Palomar 60-inch telescope, took spectra with the 200-inch, and identified them with their counterparts on the 48-inch Schmidt using overlays.

From these data, Sanders suggested an evolutionary path leading from infrared-bright galaxies to quasars. In his scenario, the first stage of the transition occurs when gas and dust are driven to the center of an infrared galaxy which contains either a dust-shrouded starburst, an active black hole, or a pair of merging black holes. The galaxies’ star-forming regions are embedded in dust, which absorbs ultraviolet and optical radiation. The absorbed energy heats the dust until it radiates at a temperature of 30 to 60 K. Then, in a second stage, powerful winds—created by supernova explosions and radiation pressure—sweep the dust clear of the nuclear region, allowing the embedded quasar to outshine the decaying starburst. A bright “naked” quasar makes its appearance.

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