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Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses
Published on: July 2, 2012
Dust-free quasars in the early Universe
Linhua Jiang1, Xiaohui Fan, W N Brandt
1Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721, USA. ljiang@email.arizona.edu
Nature
|March 19, 2010
Summary
Early universe quasars lack hot dust, suggesting they are young, first-generation objects. Their hot dust abundance correlates with black hole growth, unlike older quasars.
Area of Science:
- Astronomy
- Cosmology
- Astrophysics
Background:
- Distant quasars at redshift z~6 exhibit properties similar to lower-redshift quasars.
- This similarity suggests evolved objects, contradicting the early cosmic age (7% of current age).
- Previous observations noted one z~6 quasar lacking hot dust, raising questions about high-redshift dust properties.
Purpose of the Study:
- Investigate the prevalence of hot dust in z~6 quasars.
- Determine if hot-dust-free quasars are unique to the early universe.
- Understand the relationship between hot dust abundance and black hole mass evolution.
Main Methods:
- Analyzed a sample of 21 quasars at redshift z~6.
- Searched for detectable emission from hot dust.
- Compared hot dust abundance with central black hole mass.
Main Results:
- Discovered a second quasar without detectable hot dust among the 21 z~6 quasars.
- Found no counterparts to these hot-dust-free quasars at low redshift.
- Demonstrated that hot dust abundance in z~6 quasars correlates with black hole mass growth, unlike at low redshift.
Conclusions:
- z~6 quasars represent an early evolutionary stage with rapid accretion and dust formation.
- The two observed hot-dust-free quasars are likely first-generation objects.
- These young quasars originated in dust-free environments and haven't yet formed significant hot dust.
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