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
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
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
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)
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)
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
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
THE EXTINCTION LAW AT HIGH REDSHIFT:
Implications on galaxy spectra at z>4
Gallerani et al. 2010, submitted to A&A
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.
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.
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
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