The extinction law at high redshift (z>4) and its implications
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The extinction law at high redshift (z>4) The extinction law at high redshift (z>4) and and
its implicationsits implications
Simona Gallerani
in collaboration with:
R. Maiolino; Y. Juarez; T. Nagao; A. Marconi, S. Bianchi, R. Schneider; F. Mannucci; T. Oliva; C. Willott; L. Jiang; X. Fan.
Osservatorio Astronomico di Roma
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EXTINCTION CURVE AT z<4 FROM QUASAR SPECTRA
BAL are the most reddenedsub-class of QSOs
Red
deni
ng
SMC-like extinction curveas for noBAL QSOs at z<4
Reichard et al. 2003; Richards et al. 2003; Hopkins et al. 2004
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Extinction curve consistent with properties of dust theoretically Extinction curve consistent with properties of dust theoretically expected from SNeexpected from SNe
(Maiolino et al. 04)(Maiolino et al. 04)
(Todini & Ferrara 01)(Todini & Ferrara 01)
Bluer than any BAL at low z (Maiolino et al.04)
EXTINCTION CURVE AT z~6 FROM QUASAR SPECTRA
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Stratta et al. 06
EXTINCTION CURVE AT z~6 FROM GRB SPECTRA
GRB050904 GRB050904 at z=6.3at z=6.3
((Tagliaferri Tagliaferri et al. 2005et al. 2005))SN dust (A3000Å=2)
=QSO J1148 z=6.2
Galactic (A3000Å=1.49) SMC (A3000Å=0.8)
Calzetti (A3000Å=2)
Data fromHaislip et al. 06
K
HJ Z
(see also(see also Watson et al. 2010)Watson et al. 2010)
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A SAMPLE of 33 OPTICAL/NIR SPECTRA OF QSOs AT 4<z<6.4
5.2)62.1(
3000103000
λα
λλλ A
AtempλCFF−
−
⎟⎠⎞⎜⎝
⎛=
Fλtempl
template by Reichard et al. 2003, having α=-1.62
A3000 absolute extinction at 3000 Å
Aλ extinction curve normalized at 3000 Å
(Data from Juarez et al. 2009; Jiang et al. 2007; Willott et al. 2009; Mortlock et al. 2008)
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GRID OF EXTINCTION CURVES
170 M
nH=1cm-3
Todini & Ferrara 01Bianchi & Schneider 07
Hirashita et al. 08
20 M
Hirashita et al. 08
SNe type dust
SNe type dust
Pair instabilitySNe type
dust
Empiricalextinction curves
from thelocal Universe
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DUST REDDENING IN 4<z<6.4 QSOs
Evidence for different dust properties (chemical composition? grain size distribution? dust sources?...)
in the early Universe
Extinction curves at 4<z<6.4
Extinction curve at 0<z<4
Gallerani et al. 2010, subm
itted to A&
A
€
A3000BAL ≈1.8
€
A3000BAL ≈1.1
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THE EXTINCTION LAW AT HIGH REDSHIFT:
Implications on galaxy spectra at z>4
Gallerani et al. 2010, submitted to A&A
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THE EXTINCTION LAW AT HIGH REDSHIFT:
Implications on galaxy spectra at z>4
Gallerani et al. 2010, submitted to A&A
λRF=1600 Å
λRF=2300 Å
The amount of dust in a galaxy is measured from the spectral slope β.
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THE EXTINCTION LAW AT HIGH REDSHIFT:
Implications on galaxy spectra at z>4
Gallerani et al. 2010, submitted to A&A
λRF=1600 Å
λRF=2300 Å
The amount of dust inferred from a galaxy spectrum depends on the extinction curve adopted.
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THE EXTINCTION LAW AT HIGH REDSHIFT:
Implications on the star formation rate at z>4
Gallerani et al. 2010, submitted to A&A
The extinction curve inferred at z>4 implies a star formation rate at these epochs higher than previously estimated.
~20
≤ 3
Data from Bouwens et al. 09
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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?…)
• The mean extinction curve (MEC) at z>4 implies a star formation rate at these epochs higher than previously estimated.
Gallerani et al. 2010, submitted to A&A