reddening nancy elias de la rosa. outline interstellar reddening extinction law – cardelli et...
TRANSCRIPT
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