REDDENING

Nancy Elias de la Rosa

OUTLINE

Interstellar reddening Extinction law – Cardelli et al. Reddening in SNIa Photometric methods Spectroscopic methods

Interstellar Reddening

• In a galaxy only ~10-22 of the volume is in stars.

• The Interstellar Medium provides 5-10% of the baryonic mass of the galaxy in form of gas mixed with tiny solid particles: dust grain.

• Dust strongly affects the properties of astrophysical objects.

• Dust particles interact with photons (absorbtion, scattering, polarization). This is particularly effective in optical-UV.

Interstellar Reddening

Dibujo del talk con los rayos azul y rojo

Blue light is absorbed more than red light

Interstellar Reddening

Interstellar Reddening

Apparent magnitude: m1() = M1() + 5 log d1 + A1() m2() = M2() + 5 log d2 + A2()

where 1 = ‘reddened’ star; 2 = ‘comparison’ star

if M1() = M2() => m() = 5 log (d1/d2) + A()

for 1 and 2: Enorm = (m() - m(2)) / (m(1) - m(2)) = (A() - A(2)) / (A(1) - A(2)) = E( - 2) / E(1- 2)

where Enorm = normalized extinction

Extinction curve:

E(-V) A() - A(V) A() A(V) = = RV - 1 => RV = E(B-V) E(B-V) A(V) E(B-V)

Cardelli´s extinction law

Extinction law = A()/A(V)

Parameterization: the average Rv-dependent Extinction Law

A()/A(V) = a(x) + b(x)/Rv

(x= -1)

Rv affects the shape of the extinction curves(particularly at the shorter wavelengths)

Cardelli et al. 1989

Cardelli´s extinction law

Cardelli et al. 1989

A bump around 2175 Å

Serious deviation for x > 7 m-1

Shape independent on Rv in the NIR

RV ratio-of-total-extinction

AB = RB x E(B-V)

RB = 4.14 ± 0.15 (Savage & Mathis 1979) 1.70 ± 0.33 (Capaccioli et al. 1990) 3.35 ± 0.25 (Della Valle & Panagia 1992) 3.55 ± 0.30 (Riess et al. 1996) 2.09 (Tripp 1998) 3.5 ± 0.4 (Phillips et al. 1999) 2.8 (Krisciunas et al. 2000) 3.88 ± 0.15 (Wang et al. 2003) 3.5 (Altavilla et al. 2004) 3.65 ± 0.21 (Reindl et al. 2005) 3.1 ± 0.5 (Elias et al. 2005)

(here RB RV + 1)

Reddening in SN Ia

SN 1994D

SN 2003cg

Reddening in SN Ia

(3) absence of interstellar NaI line

(1) morphology of the host galaxy

(2) position of the SN in the host galaxy

SNe in E or S0 galaxies are less affected by dust

Na ID

Turatto et al. 2003

Na ID

SN2003cg

Lira

(30 tv 90)

Lira 1995Phillips et al. 1999

Phillips Relations: Bmax-Vmax

Phillips et al. 1999

(at max)

Phillips Relation: Vmax-Imax and tail

Phillips et al. 1999

Lira(at late time)

(at max)

Reindl Relations

Reindl et al. 2005

There are alsorelations at +35 days

Multicolor Light Curve Shape (MLCS)

Riess et al. 1996

CMAGIC

Wang et al. 2003

Extinction Curves Comparison

Reddened SNUnreddened SN

Corrected by redshift and Galactic reddeningPut at same distance

A() = -2.5 log (F /F0)

normalize to A(V)

ratio = approximate extinction curve

to be compared with the theoretical Cardelli's extinction law.

(Similar m15 and spectra features)

F0 F

Extinction Curves Comparison

At maximum

Extinction Curves Comparison

At +30 days

Spectral Comparison

E(B-V) = 1.22RV = 2.0

Optical Color Evolution

E(B-V) = 1.22RV = 2.0

IR Color Evolution

E(B-V) = 1.22RV = 2.0

Relation between Rv and E(B-V)

Fitzpatrick 1999(R RV)

IR Spectra

Rudy et al. 2002

Diffuse Interstellar Bands

Herbig 1995

Diffuse Interstellar Bands

6283.86 Å