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