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DUST AT HIGH REDSHIFT
Why do we care?
BAL are the most reddened
sub-class of QSOs R
ed
den
ing!
SMC-like extinction curve!
as for noBAL QSOs at 0<z<2.2!
Reichard et al. 2003; Richards et al. 2003; Hopkins et al. 2004!
dusty wind
EXTINCTION CURVE AT z<4 FROM QSO SPECTRA
Bluer than any BAL at low z (Maiolino et al.04)
EXTINCTION CURVE AT z~6 FROM QSO SPECTRA
A SAMPLE of 33 OPTICAL/NIR SPECTRA OF QSOs AT 4<z<6.4
5.2
)62.1(3000
103000
!"
!!
! AA
templCFF#
#
$%
&'(
)=
F!templ
template by Reichard et al. 2003, having !=-1.62
A3000 absolute extinction at 3000 Å
A! extinction curve normalized at 3000 Å
(Data from Juarez et al. 2009; Jiang et al. 2007; Willott et al. 2009; Mortlock et al. 2008)
GRID OF EXTINCTION CURVES
!
A"
mix= (1# p)A"
SMC+ pA"
SN
170 M!
nH=1cm-3
Todini & Ferrara 01 Bianchi & Schneider 07
Hirashita et al. 08
20 M!
Hirashita et al. 08
SNe type dust
SNe type dust
Pair instability SNe type
dust
Empirical extinction curves
from the local Universe
!
0 " p "1
DUST REDDENING IN 4<z<6.4 QSOs
Extinction curves
at 4<z<6.4
Extinction curve
at 0<z<4
Gallerani et al. (2010)
!"#$%&&$'()$#)**)+)*$,-%.%#$"/$"-#$.%01&)$$
'()$2).'$3'$)45+65"+$6-#7)$8.$+"'$'()$9:;$
THE EXTINCTION LAW AT HIGH REDSHIFT
Evidence for different dust properties in the early Universe (chemical composition? grain size distribution? dust sources?...)
Gallerani et al. (2010)
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CONCLUSIONS
•! Dust extinction in quasars at z<4 is described through
the SMC extinction curve.
•! We infer a mean extinction curve (MEC) from 4<z<6.4
quasar spectra finding that it deviates from the SMC one.
•! Evidence for different dust properties in the early Universe,
(dust sources? chemical composition? grain size?…)
Gallerani et al. (2010)
