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 ~ 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

Apparent magnitude: m 1 ( ) = M 1 ( ) + 5 log d 1 + A 1 ( ) m 2 ( ) = M 2 ( ) + 5 log d 2 + A 2 ( ) where 1 = ‘reddened’ star; 2 = ‘comparison’ star if M 1 ( ) = M 2 ( ) =>  m( ) = 5 log (d 1 /d 2 ) + A( ) for 1 and 2 : E norm = (  m( ) -  m( 2 )) / (  m( 1 ) -  m( 2 )) = (A( ) - A( 2 )) / (A( 1 ) - A( 2 )) = E( - 2 ) / E( ) where E norm = normalized extinction Extinction curve: E( -V) A( ) - A(V)  A( ) A(V) = = R V  - 1  => R V = E(B-V) E(B-V)  A(V)  E(B-V)

Cardelli´s extinction law Extinction law = A( )/A(V)  Parameterization: the average R v -dependent Extinction Law A( )/A(V) = a(x) + b(x)/R v (x= -1 )  R v affects the shape of the extinction curves (particularly at the shorter wavelengths) Cardelli et al. 1989

Cardelli´s extinction law Cardelli et al A bump around 2175 Å Serious deviation for x > 7  m -1 Shape independent on R v in the NIR

R V ratio-of-total-extinction A B = R B x E(B-V) R B = 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 R B  R V + 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

Reddening in SN Ia SN 2003cg in NGC 3169 (SA(s)a pec) SN 2004eo in NGC 6928 (SB(s)ab)

Reddening in SN Ia NGC 3169 MW

Na ID Turatto et al. 2003

Na ID SN2003cg

Lira (30  t v  90) Lira 1995 Phillips et al. 1999

Phillips Relations: B max -V max Phillips et al (at max)

Phillips Relation: V max -I max and tail Phillips et al Lira (at late time) (at max)

Reindl Relations Reindl et al There are also relations at +35 days

Multicolor Light Curve Shape (MLCS) Riess et al. 1996

CMAGIC Wang et al. 2003

Extinction Curves Comparison Reddened SN Unreddened SN Corrected by redshift and Galactic reddening Put at same distance A( ) = -2.5 log (F /F 0 ) normalize to A(V) ratio = approximate extinction curve to be compared with the theoretical Cardelli's extinction law. (Similar  m 15 and spectra features) F 0 F

Extinction Curves Comparison At maximum

Extinction Curves Comparison At +30 days

Spectral Comparison E(B-V) = 1.22 R V = 2.0

Optical Color Evolution E(B-V) = 1.22 R V = 2.0

IR Color Evolution E(B-V) = 1.22 R V = 2.0

Relation between R v and E(B-V) Fitzpatrick 1999 (R  R V )

IR Spectra Rudy et al. 2002

Diffuse Interstellar Bands Herbig 1995

Diffuse Interstellar Bands Å