Type Ia Supernovae in the Near-Infrared

Kevin Krisciunas

Texas A&MGeorge P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy

Collaborators: Nick Suntzeff, Mark Phillips, MarioHamuy, Peter Garnavich …

The most popular model of a Type Ia supernova.

It is generally believed that a Type Ia SN is a carbon-oxygen white dwarf that acquires mass froma nearby donor star. When the mass of the WD exceeds1.4 Msun the WD completely obliterates itself.

The spectra of Type Ia supernovae are characterized byhaving no hydrogen emission. The prime signatureis a blue-shifted absorption line of singly ionized siliconobserved at ~6150 Angstroms.

A Type Ia SN produces between 0.1 and 1.0 solar massesof radioactive Nickel-56, which decays to Cobalt-56,which decays to Iron-56, which is stable.

Two Type Iasupernovae atabout the samenumber of daysafter explosion.The spectra arealmost identical.

Krisciunas et al. (2007)

B-band lightcurves of twoType Iasupernovae.The “declinerate” is thenumber ofmagnitudes itgets fainterin the first15 days aftermaximum light.

At optical wave-lengths, the absolutemagnitudes of TypeIa supernovae atmaximum brightnessare related to thedecline rate parameter.These supernovae arestandardizablecandles. The brightestones are 4 billion times brighter thanthe Sun.

Garnavich et al. (2004)

We are publishinga paper in theDecember, 2009,issue of the AJ onSN 2003gs, picturedhere next to itshost galaxy NGC 936.We know the distanceto the host from themethod of SurfaceBrightness Fluctua-tions.

Optical photometryof SN 2003gsobtained with theCTIO 1.3-m, 0.9-m,Las Campanas 1.0-m, and Steward1.54-m telescopes.

With Δm15(B) = 1.83it is a fast declinerand is “faint” inthe optical bands.

Near-IR lightcurves ofSN 2003gs.

Data fromCTIO 1.3-mtelescope.

It seems thatSN 2003gspeaked in thenear-IR about3 days beforethe time ofB-band maxi-mum.

Curved locus is stretchable template ofKrisciunas et al. (2004b).

SN 2003gs is notthe only fastdecliner thatpeaked prior toT(Bmax). Therewas 86G, 03hv, and 06gt.

Other fast declinersobserved in the near-IR have weak secondarymaxima and peak after T(Bmax).

The fastdecliners thatpeak earlyare just asbright as themuch slowerdecliners.Except forthe late-peakingfast decliners,Type Ia SNeare standardcandles inthe near-IR.

If we never findany objects inthe middle, thenwe’ll have toconsider the near-IR absolutemagnitudes ofthe fast declinersa bimodaldistribution.

In the case of SN 2001el vs. 2004S, a combination of optical and near-IR photometry allowed us to get an accurate value of theparameter RV = AV / E(B-V) = 2.15 +/- 0.24, and the extinction AV.

Standard Milky Way dust has RV ~ 3.1. ManyType Ia SNe have host galaxy dust with RV ~ 2.4.

Some Type Ia SNe have RV in the range 1.55 to 1.8(1999cl, 2002cv, 2003cg, 2006X).

To do the very best cosmology with Type Ia SNe, youshould determine RV for every object.

Krisciunas et al. (2007)

The accuracy ofa distancedeterminationcan be greatlyimproved byhaving bothoptical and IRdata.

For near-IR spectra of Type Ia SNe see :

Marion et al. (2009), AJ 138, 727

Kotak et al., in preparation (SN 2003gs)

Conclusions

Type Ia SNe are standardizable candles in optical bands.

Type Ia SNe are standard candles in the near-IR, exceptthe fast decliners that peak after the time of B-band maximum.

A combination of rest-frame optical and near-IR photometry can give you distances/absolute magnitudes which havesystematic errors due to extinction corrections as low as 0.02mag. This is true even if the dust in the host galaxies is verydifferent than dust in our Milky Way.