Determining the properties of dust in other galaxies using Type Ia SNe

Determining the properties of dustin other galaxies using Type Ia SNe

Kevin Krisciunas

George P. and Cynthia Woods Mitchell Institute forFundamental Physics & Astronomy, Texas A&M University, College Station, Texas

Walter Baade (1893-1960)discovered the two basic populations of stars (Pop I and II)and, with Zwicky, founded SNresearch.

In the summer of 1953 he participated in a summerschool in astrophysics at the Univ. of Michigan.One evening a grad student asked him if he had hislife to live over, would he still have become an astronomer?Baade answered, “Yes, but only if R were constant.”

Cardelli, Clayton, and Mathis (1989)

It has been knownfor decades that differentlines of sight inthe Galaxy givedifferent values ofRV = AV / E(BV).CCM89 giveA / AV =ab / RV .Normal Galacticdust has RV = 3.1.

The CCM89parametrizationshows that fordifferent valuesof RV we havedifferent valuesof A / AV .

Standard model of a Type Ia SN. A white dwarf in a closebinary system acquires mass. When it reaches 1.4 MSun itexplodes, producing 0.1 to 1.0 MSun of 56Ni.

The “decline rate” m15(B) of Type Ia supernovae

The decline rate was originally defined just from B-bandlight curves. Nowadays, BVRI data are used to determinem15(B). It is more of a morphological label.

A stack of I-band light curves ordered by the declinerate shows that slow decliners have late, strong secondarymaxima. As we proceed to larger values of m15(B) thesecondary maximum becomes weaker and earlier, untilit just blends with the first maximum.

Optical and near-IR lightcurves of thenormal Type IaSN 2001el.

Garnavich et al. (2004)

Fast declinersare less luminousthan slow declinersin optical bands.This makes Type Ia SNe “standard-izable candles”.

Meikle (2000) showed that Type Ia SNe at ~ 14 days after T(Bmax) might be standard candles.

The absolutemagnitudes ofType Ia SNe atthe times of thenear-IR maximaare statisticallyconstant, at least for theslow declinersand the mid-rangedecliners.

Krisciunas et al. (2009b, in press)

The fast declinersthat peak lateare fainter andalso have weakersecondary peaks.

Krisciunas et al. (2009b, in press)

The Hubble diagram for extragalactic standard[izable]candles, corrected for extinction.

Conley et al. (2007, ApJ, 664, L13)

Fitting the same SNe with different fitters gives aslope of = RB = 2.7 +/- 0.3 (RV = 1.7). Whetherwe live in a Hubble bubble or not depends criticallyon what SN colors you adopt!

The nature of the Dark Energy depends on the valueof the equation of state parameter w = P / ( c2). Ifw = -1, then the Dark Energy is equivalent to Einstein’scosmological constant.

SN surveys, combined with WMAP data or baryonacoustic oscillations, obtain w between -0.8 and -1.1depending on the SN fitter and the extinction priors adopted. The situation is much worse than we had feared.

ESSENCE project (M. Wood-Vasey plot)

The basic rule is that if you are observing inone filter, you have no information about reddening.Half of the original 42 high-redshift SNe observedby Perlmutter et al. (1999) cannot really be used forcosmology because they were observed in only onefilter.

The ESSENCE survey observed in two filters (R andI). You can correct for reddening with two-filter databut cannot derive any extinction law.

The Legacy SN survey has observed in 4 filters (griz)and can derive dust properties for each object.

Lira (1995) relation forunreddened Type Ia SNe.

New CSP Lira Law(Folatelli et al. 2009)

While unreddened Type Ia SNe have different B-Vcolors at maximum light, from 30 to 90 days aftermaximum light they have uniform B-V color curves.

The RMS scatter in the tail is about 0.07 mag.

An estimate of the B-V color excess can be obtained from a plot of the observed colors in the tail vs. the unreddened locus.

Elias et al. (1985) suggested that V-K might be auniform color index for these objects.

SN 1999cl occurred inM 88 (NGC 4501),which is supposedto be part of theVirgo cluster.

Krisciunas et al. (2000)

Based on Krisciunas et al. (2000)

Krisciunas et al. (2000)

Our first V-[JHK]color templates.

Peter Hoeflich showed in our 2003 paper on SN 2001elthat a generic SN model could reasonably reproducethe V-H and V-K colors of Type Ia SNe.

For AV = 3.1 E(B-V), an uncertainty of 0.07 mag inthe unreddened color leads to a 0.2 mag uncertaintyin AV. If RV is not 3.1, then serious systematic errorscan result.

However, if uniform unreddened V-[JHK] colors exist,AV ~ 1.217 E(V-H) ~ 1.130 E(V-K) for RV = 3.1.

For really non-standard dust these parameters do not change much. For RV = 1.55, AV ~ 1.07 E(V-K).

The systematic errors in near-IR extinction can approachthe random errors of the photometry.

SN 1999cl was highly reddened and dimmed by dustin the host galaxy. But if we adopt “normal” dust withRV = 3.1, the calculated distance is 7.2 Mpc. Sincethe cluster is supposedly at d ~ 16 Mpc, that is problematic.

Krisciunas et al. (2006) obtained a revised value ofRV = 1.55 +/- 0.08 for 99cl. The distance is 15.5 +/- 1.5Mpc, which confirms the membership in the Virgocluster.

Draine (1999, private communic.) was able to come upwith a recipe for grains that would give a low valueof RV . But Lifan Wang (2005) warned that we mustconsider scattering too.

We also have to consider thepossibility that in the aftermathof a supernova explosion,the nearby interstellar mediumis altered, and unusual statesof carbon-based materialcould be produced.

Other Type Ia supernovae with low RV values:

2002cv 1.59 (0.07) Elias-Rosa et al. (2008) AV = 8.74 +/- 0.21!

2003cg 1.80 (0.19) Elias-Rosa et al. (2006)

2006X 1.48 (0.06) X. Wang et al. (2008)

2001el 2.15 (0.23) Krisciunas et al. (2007)

SN 2001el inNGC 1448(also the host ofSN 2003hn)

These twoSNe wereclones ofeach other.

Krisciunas et al. (2007)

Light curves of SN 2004S and templates based on fits tophotometry of SN 2001el. (If the spectra are nearly identical,the light curves will be nearly identical.)

If SNe 2001el and 2004S were identical objects,then the photometry should allow us to determinethe difference of the distance moduli of the hostgalaxies, providing we have the right extinctionlaw for dust in each galaxy. As SN 2004S wasessentially unreddened in its host, this allows us todetermine the extinction and RV for the dust in 2001el.

Take optical and IR photometry and correct it onlyfor Galactic extinction from Schlegel, Finkbeiner,and Davis (1998). Look at how much fainter oneSN was compared to the other, as a function ofwavelength.

Similar to a graph in Krisciunas et al. (2007)

For infinitewavelengththere will beno extinction,and the dashedline will represent thedifference ofthe distancemoduli of thegalaxies.

Observing Type Ia SNe in rest frame optical bands plusone or more near-IR bands allows one to determine RV andAV with considerable accuracy, even for “weird” dust.

Krisciunas et al. (2007)

SN 2004S datafitted with templatesfrom SN 2001el.

SN 2004S datafitted with templatesbased on 8 otherobjects with mid-range decline rates.(Krisciunas et al. 2000). Fits are OK,but not great.

Slow decliners (solid lines) are~0.24 mag bluer in V-H andV-K than mid-range decliners(Krisciunas et al. 2004b).

Fast decliners have similarV-H and V-K colors at latetimes, which are also similar to the mid-range decliner SN 2001el at late times(Krisciunas et al. 2009b, in press).

Do Type II SNe exist with similar enough colors thatwe can use the photometry to determine at least thedifferential color excesses of the SNe? Yes.

V minus IR colorsof SN 2003hn andtemplates of 99em(Krisciunas et al.2009a). The problem is: there are no Type II-P’s that are unreddened.

Other evidence for dust, standard and otherwise

Reindl et al. (2005) analysis of 122 SNe gives meanRV = 2.65 +/- 0.15.

X. Wang et al. (2006) analysis of 109 SNe gives meanRV = 3.33 +/- 0.11.

X. Wang et al. (2009), preprint 0906.1616

Those with expansion velocity within 3 days of T(Bmax) greater than 11,800 km/sec have lower RV. Some propertiesof the dust must be related to the SNe themselves…

Various studies find that adopting RV ~ 1.8 for Type Ia SNe minimizes the scatter in the Hubble diagram(e.g. SN Legacy Survey, Folatelli et al. 2009). Theevidence is that there is an intrinsic dispersion in the colors of Type Ia supernovae which is correlated with luminosity but independent of the decline rate.

So, Type Ia SNe are not such pure standardizablecandles after all. We need new insights on dustproduction. We need a better understanding of thecomposition and opacities in these explosions fromtheoretical and observational perspectives.

Goobar (2008, ApJ, 686, L103) tried thisparameterization, different than CCM89:

AV = 1 – a + a (V)p

Lensing Galaxies

Falco et al. (1999) found RV = 1.47 and 7.20 fortwo galaxies with redshift 0.96 and 0.68, respectively.

Toft et al. (2000) found RV between 1.3 and 2.0 fora z = 0.44 lensing galaxy.

Oestman, Goobar, and Moertsell (2008) studied 21quasar-galaxy systems and found RV ~ 2.4.

Eliasdottir et al. (2009), GRB 070802 shows evidencefor 2175 A bump in the host galaxy.

Menard et al. (0902.4240, 0903.4199) simultaneouslymeasured gravitational magnification and dust reddening due to galactic halos and large scalestructure. They correlated 85,000 quasars with thepositions of 20 million galaxies at z~ 0.3 from theSloan Digital Sky Survey.

M and w = P/( c2) are biased at the level of afew percent by AV ~ 0.03 mag absorption in thehalos of lensing galaxies. Menard et al. find typical halodust masses of 5 X 107 solar masses, out to severaltens of kpc from the individual galaxies. To determinew accurately enough to say it is equal/not equalto -1 will have to take this effect into account.

Anti-correlation between quasar magnitude and foregroundoverdensity due to magnification. Systematic offset isa function of filter, suggesting dust extinction.