1. Determining the properties of dust in other galaxies using Type Ia SNe Kevin Krisciunas George P. and Cynthia Woods Mitchell Institute for Fundamental Physics & Astronomy, Texas A&M University, College Station, Texas

2. Walter Baade (1893-1960) discovered the two basic populations of stars (Pop I and II) and, with Zwicky, founded SN research. In the summer of 1953 he participated in a summer school in astrophysics at the Univ. of Michigan. One evening a grad student asked him if he had his life to live over, would he still have become an astronomer? Baade answered, “Yes, but only if R were constant.”

3. Cardelli, Clayton, and Mathis (1989) It has been known for decades that different lines of sight in the Galaxy give different values of R V = A V / E(B  V). CCM89 give A / A V = a  b / R V. Normal Galactic dust has R V = 3.1.

4. The CCM89 parametrization shows that for different values of R V we have different values of A / A V.

5. Standard model of a Type Ia SN. A white dwarf in a close binary system acquires mass. When it reaches 1.4 M Sun it explodes, producing 0.1 to 1.0 M Sun of 56 Ni.

6. The “decline rate”  m 15 (B) of Type Ia supernovae

7. The decline rate was originally defined just from B-band light curves. Nowadays, BVRI data are used to determine  m 15 (B). It is more of a morphological label. A stack of I-band light curves ordered by the decline rate shows that slow decliners have late, strong secondary maxima. As we proceed to larger values of  m 15 (B) the secondary maximum becomes weaker and earlier, until it just blends with the first maximum.

8. Optical and near-IR light curves of the normal Type Ia SN 2001el.

9. Garnavich et al. (2004) Fast decliners are less luminous than slow decliners in optical bands. This makes Type Ia SNe “standard- izable candles”.

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

11. The absolute magnitudes of Type Ia SNe at the times of the near-IR maxima are statistically constant, at least for the slow decliners and the mid-range decliners. Krisciunas et al. (2009b, in press)

12. The fast decliners that peak late are fainter and also have weaker secondary peaks. Krisciunas et al. (2009b, in press)

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

14. Conley et al. (2007, ApJ, 664, L13) Fitting the same SNe with different fitters gives a slope of  = R B = 2.7 +/- 0.3 (R V = 1.7). Whether we live in a Hubble bubble or not depends critically on what SN colors you adopt!

15. The nature of the Dark Energy depends on the value of the equation of state parameter w = P / (  c 2 ). If w = -1, then the Dark Energy is equivalent to Einstein’s cosmological constant. SN surveys, combined with WMAP data or baryon acoustic oscillations, obtain w between -0.8 and -1.1 depending on the SN fitter and the extinction priors adopted. The situation is much worse than we had feared.

16. ESSENCE project (M. Wood-Vasey plot)

17. The basic rule is that if you are observing in one filter, you have no information about reddening. Half of the original 42 high-redshift SNe observed by Perlmutter et al. (1999) cannot really be used for cosmology because they were observed in only one filter. The ESSENCE survey observed in two filters (R and I). You can correct for reddening with two-filter data but cannot derive any extinction law. The Legacy SN survey has observed in 4 filters (griz) and can derive dust properties for each object.

18. Lira (1995) relation for unreddened Type Ia SNe. New CSP Lira Law (Folatelli et al. 2009)

19. While unreddened Type Ia SNe have different B-V colors at maximum light, from 30 to 90 days after maximum 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 a uniform color index for these objects.

20. SN 1999cl occurred in M 88 (NGC 4501), which is supposed to be part of the Virgo cluster. Krisciunas et al. (2000)

21. Based on Krisciunas et al. (2000)

22. Krisciunas et al. (2000) Our first V-[JHK] color templates.

23. Peter Hoeflich showed in our 2003 paper on SN 2001el that a generic SN model could reasonably reproduce the V-H and V-K colors of Type Ia SNe.

24. For A V = 3.1 E(B-V), an uncertainty of 0.07 mag in the unreddened color leads to a 0.2 mag uncertainty in A V. If R V is not 3.1, then serious systematic errors can result. However, if uniform unreddened V-[JHK] colors exist, A V ~ 1.217 E(V-H) ~ 1.130 E(V-K) for R V = 3.1. For really non-standard dust these parameters do not change much. For R V = 1.55, A V ~ 1.07 E(V-K). The systematic errors in near-IR extinction can approach the random errors of the photometry.

25. SN 1999cl was highly reddened and dimmed by dust in the host galaxy. But if we adopt “normal” dust with R V = 3.1, the calculated distance is 7.2 Mpc. Since the cluster is supposedly at d ~ 16 Mpc, that is problematic. Krisciunas et al. (2006) obtained a revised value of R V = 1.55 +/- 0.08 for 99cl. The distance is 15.5 +/- 1.5 Mpc, which confirms the membership in the Virgo cluster. Draine (1999, private communic.) was able to come up with a recipe for grains that would give a low value of R V. But Lifan Wang (2005) warned that we must consider scattering too.

26. We also have to consider the possibility that in the aftermath of a supernova explosion, the nearby interstellar medium is altered, and unusual states of carbon-based material could be produced.

27. Other Type Ia supernovae with low R V values: 2002cv 1.59 (0.07) Elias-Rosa et al. (2008) A V = 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)

28. SN 2001el in NGC 1448 (also the host of SN 2003hn)

29. These two SNe were clones of each other. Krisciunas et al. (2007)

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

31. If SNe 2001el and 2004S were identical objects, then the photometry should allow us to determine the difference of the distance moduli of the host galaxies, providing we have the right extinction law for dust in each galaxy. As SN 2004S was essentially unreddened in its host, this allows us to determine the extinction and R V for the dust in 2001el. Take optical and IR photometry and correct it only for Galactic extinction from Schlegel, Finkbeiner, and Davis (1998). Look at how much fainter one SN was compared to the other, as a function of wavelength.

32. Similar to a graph in Krisciunas et al. (2007) For infinite wavelength there will be no extinction, and the dashed line will represent the difference of the distance moduli of the galaxies.

33. Observing Type Ia SNe in rest frame optical bands plus one or more near-IR bands allows one to determine R V and A V with considerable accuracy, even for “weird” dust. Krisciunas et al. (2007)

34. SN 2004S data fitted with templates from SN 2001el.

35. SN 2004S data fitted with templates based on 8 other objects with mid- range decline rates. (Krisciunas et al. 2000). Fits are OK, but not great.

36. Slow decliners (solid lines) are ~0.24 mag bluer in V-H and V-K than mid-range decliners (Krisciunas et al. 2004b). Fast decliners have similar V-H and V-K colors at late times, which are also similar to the mid-range decliner SN 2001el at late times (Krisciunas et al. 2009b, in press).

37. Do Type II SNe exist with similar enough colors that we can use the photometry to determine at least the differential color excesses of the SNe? Yes. V minus IR colors of SN 2003hn and templates of 99em (Krisciunas et al. 2009a). The problem is: there are no Type II-P’s that are unreddened.

38. Other evidence for dust, standard and otherwise Reindl et al. (2005) analysis of 122 SNe gives mean R V = 2.65 +/- 0.15. X. Wang et al. (2006) analysis of 109 SNe gives mean R V = 3.33 +/- 0.11.

39. X. Wang et al. (2009), preprint 0906.1616 Those with expansion velocity within 3 days of T(B max ) greater than 11,800 km/sec have lower R V. Some properties of the dust must be related to the SNe themselves…

40. Various studies find that adopting R V ~ 1.8 for Type Ia SNe minimizes the scatter in the Hubble diagram (e.g. SN Legacy Survey, Folatelli et al. 2009). The evidence 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 standardizable candles after all. We need new insights on dust production. We need a better understanding of the composition and opacities in these explosions from theoretical and observational perspectives.

41. Goobar (2008, ApJ, 686, L103) tried this parameterization, different than CCM89: A  V = 1 – a + a (  V ) p

42. Lensing Galaxies Falco et al. (1999) found R V = 1.47 and 7.20 for two galaxies with redshift 0.96 and 0.68, respectively. Toft et al. (2000) found R V between 1.3 and 2.0 for a z = 0.44 lensing galaxy. Oestman, Goobar, and Moertsell (2008) studied 21 quasar-galaxy systems and found R V ~ 2.4. Eliasdottir et al. (2009), GRB 070802 shows evidence for 2175 A bump in the host galaxy.

43. Menard et al. (0902.4240, 0903.4199) simultaneously measured gravitational magnification and dust reddening due to galactic halos and large scale structure. They correlated 85,000 quasars with the positions of 20 million galaxies at z~ 0.3 from the Sloan Digital Sky Survey.  M and w = P/(  c 2 ) are biased at the level of a few percent by A V ~ 0.03 mag absorption in the halos of lensing galaxies. Menard et al. find typical halo dust masses of 5 X 10 7 solar masses, out to several tens of kpc from the individual galaxies. To determine w accurately enough to say it is equal/not equal to -1 will have to take this effect into account.

44. Anti-correlation between quasar magnitude and foreground overdensity due to magnification. Systematic offset is a function of filter, suggesting dust extinction.