Near-IR Diagnostics for SNe Carnegie Observatories Mark M. Phillips Carnegie Observatories

Collaborators: K. Krisciunas (CTIO/Carnegie), N. Suntzeff (CTIO) M. Hamuy (Carnegie), E. Persson (Carnegie), W. Freedman (Carnegie), M. Roth (Carnegie) L. Germany (ESO)

Outline of Talk: SNe Ia Morphology of NIR light curves Light curve templates Colors & Reddening Absolute magnitudes & Hubble diagram SNe II A few words about Reddening Determinations

UBVRIJHK Light Curves of a Typical SN Ia Primary maximum Secondary maximum Sources: UBVRI: Suntzeff et al. (1999) JHK: Mayya et al. (1998) Jha et al. (1999) Hernandez et al. (2000)

Secondary maximum occurs later for slower declining SNe SN m15(B) Secondary maximum occurs later for slower declining SNe Generally speaking, secondary maximum is stronger for slower declining SNe

Y band at 1.035 µm Secondary maximum appears to have been significantly stronger than primary maximum!

Strength of Secondary Maximum vs. Decline Rate in the I Band Krisciunas et al. (2001)

Krisciunas et al. (2001)

Morphology of JHK lightcurves of SNe Ia: Primary maxima occur a few days before T(Bmax) As a general rule, the secondary maximum occurs later and is stronger in slower declining events Secondary maximum can be brighter than primary maximum (e.g., in Y & H bands) H & K light curves are relatively flat around T(Bmax)

JHK Light Curves of 6 well-observed SNe I

JHK Light Curves of the same 6 SNe I, but corrected to a stretch equivalent to m15(B) = 1.1 Let’s zoom in on this time window, and do this more precisely (e.g., include K corrections)

Construction of JHK Stretch Templates SN m15(B) = 1980N (1.29) = 1986G (1.79) = 1998bu (1.05) = 1999aw (0.81) = 1999ee (0.94) = 2000ca (1.01) = 2001el (1.15)  Krisciunas et al. (2004)

Fitting JHK Light Curves with the Stretch Templates m15(B) = 0.99 m15(B) = 1.73

Fitting JHK Light Curves with the Stretch Templates m15(B) = 1.28 m15(B) = 1.63

JHK light curve Templates for SNe Ia: Stretch technique works well for JHK light curves in the window -12 to +10 days with respect to T(Bmax) Allows reasonable estimates to be made of the maximum light magnitudes in JHK without the need to actually obtain photometry at maximum light The same technique can most likely be extended to the I band as well (useful for observations of high-z SNe Ia)

The B-V Color Evolution of Unreddened SNe Ia From: Phillips et al. 1999

The B-V Color Evolution of Unreddened SNe Ia From: Phillips et al. 1999

Scatter corresponds to ± 0.05 mag in E(B-V) Colors at Maximum Light for Unreddened SNe Ia Scatter corresponds to ± 0.05 mag in E(B-V) This is as well as we can currently determine the reddening of an individual SN Ia

"Realistic Case Optical" Av = (2.6±0.3) x E(B-V) "Worst Case NIR" Av = (1.126±0.072) x E(V-K) "Best Case Optical" Av = (3.1±0.1) x E(B-V) Krisciunas et al. (2000)

Optical-NIR Colors of Unreddened SNe Ia SNe Ia with 0.9 < m15(B) < 1.3 Shifted to Av = 0.0 locus Krisciunas et al. (2000)

Optical-NIR Colors of Unreddened SNe Ia SNe Ia with 0.8 < m15(B) < 1.0 Shifted to Av = 0.0 locus SNe Ia with 0.9 < m15(B) < 1.3 Krisciunas et al. (2004)

Optical-NIR Colors vs. Δm15(B) Unreddened SNe Ia Scatter corresponds to ± 0.18 mag in Av Equivalent to ± 0.06 mag in E(B-V) This is as expected since reddening corrections were derived from BVI data Krisciunas et al. (2004)

Reddening: SNe Ia with intermediate decline rates (0.9 < m15(B) < 1.3) have similar V-IR color evolution As expected, the V-IR color evolution of slower declining (0.8 < m15(B) < 1.0) events is somewhat bluer Use of optical-IR color evolution to determine reddening should ultimately prove more precise than optical-only colors

Note that the luminosity vs. decline rate relaton in H may be flat Absolute Magnitudes of SNe Ia Note that the luminosity vs. decline rate relaton in H may be flat Phillips et al. (2003)

Are SNe Ia “Perfect” Standard Candles in the NIR? We can try to answer this question by constructing Hubble diagrams in JHK Available data: 7 SNe Ia observed at LCO and CTIO + 9 SNe Ia with previously published photometry Use stretch template fits to find maximum light magnitudes Correct for reddening based on E(B-V) values determined from BVI photometry K corrections calculated from NIR spectra of SN 1999ee (Hamuy et al. 2002)

JHK Hubble Diagrams of SNe Ia Cepheid & SBF distances used to derive “equivalent” v(cmb) assuming Ho = 72  = 0.14 mag Are the deviations from the Hubble lines a function of m15(B)?  = 0.18 mag  = 0.12 mag Krisciunas, Phillips, & Suntzeff (2004)

Krisciunas, Phillips, & Suntzeff (2004) NIR Absolute Magnitudes of SNe Ia Within the precision of the observations, there are no obvious decline rate relations in the NIR Mean values: M(J) = -18.57 ± 0.14 M(H) = -18.24 ± 0.18 M(K) = -18.42 ± 0.12 Krisciunas, Phillips, & Suntzeff (2004)

Absolute Magnitudes & Hubble Diagrams: While SNe Ia are standardizable candles in the optical bands, they apparently are standard candles in the NIR at the ± 0.20 mag level or better (± 9% in distance) The one disadvantage of the NIR is that SNe Ia are  1 mag less luminous in JHK than they are in the V band

What about SNe II in the NIR? Plateau SNe (SNe II-P) are potentially useful distance indicators EPM (the models need more work) The Luminosity vs. Velocity Relation (looks encouraging) Major source of error is determining the dust reddening Since electron scattering is dominant opacity during plateau phase, SNe II-P should have similar similar hydrogen recombination tempertures during last part of plateau phase As in the case of SNe Ia, Optical-NIR colors offer significant promise for improving reddening estimates of SNe II-P

NIR Light Curves of a Plateau SN II SNe II-P are relatively bright in the NIR, with maximum occurring typically 2 months after explosion Hamuy et al. (2001)

Color curves and reddening Comparison of B-V and V-I Color Evolution: SN 1999gi vs. SN 1999ee Color curves and reddening Av=0.50 Av=0.85 color B-V V-I time since explosion (days) Hamuy (2002)

Color curves and reddening Comparison of B-V and V-I Color Evolution: SN 1999cr vs. SN 1999ee Color curves and reddening Av=-0.75 Av=0.10 color B-V V-I time since explosion (days) Hamuy (2002)

Comparison of B-V and V-I Reddening Determinations (Relative to SN 1999em) Reddening Estimates In many cases, values based on B-V are negative – differing metallicities may be responsible for this Values based on V-I appear to be better behaved V-NIR colors may give best estimates of all Hamuy (2002)