Spectrum Synthesis and Supernovae

1. Spectrum Synthesis and Supernovae Peter Nugent (LBNL)

2. The acceleration is 6 years old… …well more like 6 Gyr, we’re just slow at figuring it out. IPAM Workshop IV: Transfer Phenomena

3. How do we measure it? The dynamics of space is described by the expansion rate of the Universe as a function of time. An astronomical source emits a signal at time t0 which we detect now at time t1 Over this time the distance between the source and the observer changes from d0 to d1. Comparing the observed and absolute luminosities of the source tells us about d1 through the inverse square law. Comparing the observed and emitted wavelengths or the signal tells us about  d1 / d0. This we label the redshift. Relating d0 to d1 tells us about the integrated expansion rate of the Universe over that period and repeating this for sources at different distances tells us how the expansion rate has changed over time. IPAM Workshop IV: Transfer Phenomena

4. Distances and Redshifts Redshifts are easy to measure. - A simple spectrum gives you the wavelengths. Distances are very difficult. - Astronomers typically measure distances with standard candles. - They need to be seen across the universe, they have to be bright! - Their brightnesses need to be well calibrated. - The objects can't change or evolve as a function of the universe's age or expansion history. All roads lead to Type Ia Supernovae... IPAM Workshop IV: Transfer Phenomena

5. Type Ia Supernovae Type Ia Supernovae are bright: For a few weeks they are as bright as the entire galaxy they originated in. "Before" and "After" for SN 1999be. Type Ia Supernovae are very similar: They give reliable distances to better than 10% and their brightness don't appear to change as a function of the age of the universe. IPAM Workshop IV: Transfer Phenomena

6. Lightcurves and Spectra IPAM Workshop IV: Transfer Phenomena

7. Differences Calibrated In 1993 Mark Phillips discovered the correlation between peak brightness and lightcurve shape. This allowed one to calibrate SNe Ia to about 8% in distance. The race was on….. Brightness IPAM Workshop IV: Transfer Phenomena time

8. Hubble Diagram The Calan/Tololo Survey by Hamuy et al. pinned the low-z part of the Hubble diagram, while the work of Riess et al. and Perlmutter et al. got the high-z end. IPAM Workshop IV: Transfer Phenomena

9. Contours The data showed that SNe Ia were fainter at their observed redshifts than they would have been given an ΩM=1 by 10-sigma… …and in addition they were fainter than they would have been in an empty universe, indicating acceleration. Theorists rejoice, Dark Energy is born! IPAM Workshop IV: Transfer Phenomena

10. Now What?: The Past 2 Years Many groups have gone out to test these measurements: • More, more, more! • Look for signs of dust. • Compare subsets in different environments. Thanks to B. Schmidt, A. Riess and C. Lidman IPAM Workshop IV: Transfer Phenomena

11. Host Galaxy Studies Sullivan et al. (2003) Ellipticals & Spirals Over 30 SNe Ia host galaxies at high-z observed with HST/STIS photometry and with spectroscopy taken at Keck. IPAM Workshop IV: Transfer Phenomena

12. Differences are small Scatter about the Hubble line was less in the E/S0 galaxies, and they were, on average, ~0.1 magnitudes brighter than their spiral counterparts. IPAM Workshop IV: Transfer Phenomena

13. More, More, More! IPAM Workshop IV: Transfer Phenomena

14. Precision Measurements IPAM Workshop IV: Transfer Phenomena

15. Higher Redshift… Aphrodite (z~1.3) Riess et al. GOODs SN Search. ~10 SNe Ia ACS F850lp NICMOS F110W IPAM Workshop IV: Transfer Phenomena

16. Concordance Cosmology NASA and DOE have proposed a Joint Dark Energy Mission to measure the accelerating universe. IPAM Workshop IV: Transfer Phenomena

17. Where does modeling come in? • Supernova Spectrum Synthesis Simulations: • - Discover ways to improve them as distance indicators • - Eliminate/Constrain systematic uncertainties • - Real -Time assessment of data • - Provide the link between the data and hydrodynamical models • - Determine the nature of the progenitor IPAM Workshop IV: Transfer Phenomena

18. Spectrum Synthesis 1-D, Simplified Physics, Model Atmospheres (very quick line identification & velocity determination) SYNOW/MADSYN 3-D, Simplified Physics, Model Atmospheres (what effects geometry has on determining distances to SNe) SYNPOL 1-D, Full Physics, Spectrum Synthesis (can we make SNe better for distances/cosmology) PHOENIX IPAM Workshop IV: Transfer Phenomena

19. PHOENIX PHOENIX is a state-of-the-art spectrum synthesis code which is currently in 1-D. It treats all the applicable micro-physics appropriately and has been used to model supernovae of all types, the sun, novae, cool stars, red-giants, quasars and active galactic nuclei. Input: Luminosity, Abundances, Density and Velocity Profiles and Non-Thermal Ionization from radioactive Ni, Co, etc. Each of the above inputs range by an order of magnitude for SNe. 100 spatial zones, 300k wavelength points, energy conservation and non-LTE for 50 ionic species. IPAM Workshop IV: Transfer Phenomena

20. General Model Assumptions • full treatment of special relativistic radiative transfer in spherical geometry for all lines and continua, • radiative equilibrium in the Lagrangian frame (including all velocity terms), • full non-LTE treatment of most ions. • detailed profiles for the lines, fluorescence effects are included in the NLTE treatment • equation of state used includes up to 26 ionization stages of 40 elements as well as up to 206 molecules. IPAM Workshop IV: Transfer Phenomena

21. PHOENIX • Radiative Transfer Assumptions: • spherical symmetry, • time independence, • full special relativistic treatment in the Lagrangian frame. • Spherically symmetric, special relativistic equation of radiative transfer • partial integro-differential equation, • telegrapher's equation: boundary value problem in and initial value problem in (certain restrictions apply) IPAM Workshop IV: Transfer Phenomena

22. Radiative Transfer IPAM Workshop IV: Transfer Phenomena

23. Basic Emissivity More complicated for NLTE but similar in principle. IPAM Workshop IV: Transfer Phenomena

24. Numerical Solution • Basic idea: discretize and treat the boundary • value problem for each wavelength individually • Operator splitting (OS) method: • solve along characteristics of the RTE • iterative method: piecewise parabolic ansatz to calculate I for given J - iterate to self-consistent solution for J • eigenvalues of iteration matrix close to unity -> use operator splitting to reduce eigenvalues of amplification matrix IPAM Workshop IV: Transfer Phenomena

25. Rate Equations Where nj is the level population and Rij & Cij are the radiative and collisional rates, respectively + Saha-Boltzmann. IPAM Workshop IV: Transfer Phenomena

26. Atomic Data Example Grotrian diagram for Fe II: 617 Levels 1.2 million total lines The level populations off all species are solved simultaneously as a very large set of linear equations, in 256-bit precision! All relevant b-f and f-f transitions are included - atomic line blanketing: about 2*106 lines dynamically selected from Kurucz IPAM Workshop IV: Transfer Phenomena

27. The Brightness-LC Correlation There exists a spectral sequence of increasing luminosity that correlates very nicely with those of the lightcurves: Broader-Brighter-Hotter Nugent et al. (1995) IPAM Workshop IV: Transfer Phenomena

28. SN Phot-Z Templates The spectral templates were created by homogenizing IUE and HST observations + modeling to fill in the gaps. Here we have the SN Ia template every week for the first 7 weeks. Note the large color evolution. IPAM Workshop IV: Transfer Phenomena

29. SN Phot-Z Results SN 2001jm Best fit z = 0.96+/-0.07 The observed redshift was z = 0.979 Success rate is ~95% IPAM Workshop IV: Transfer Phenomena

30. Recent Discoveries… Synthetic spectra from Lentz et al. (2000), based on explosion models by Höflich et al. (1999). Metallicity effects the UV. IPAM Workshop IV: Transfer Phenomena

31. Observed Metallicity Nugent et al. HST/STIS studies of the UV… IPAM Workshop IV: Transfer Phenomena

32. Metallicity and Cosmology Understanding the UV has large implications for cosmology. Intrinsic color and corrections for dust Get intertwined. UV - suppressed UV - enhanced Ω ΩM IPAM Workshop IV: Transfer Phenomena

33. SYNPOL & 3-D Effects SYNPOL is a relatively simple code from the physics standpoint. A Monte Carlo code (follow the photons out) incorporating LTE and a 2-level atom. It iteratively solves for the temperature structure and calculates the polarization due to electron scattering and scattering off of lines. Input: Luminosity, Abundances, Density and Velocity Profiles 300x300x300 spatial zones, 2-4k wavelength points, energy conservation and an atomic linelist of ~500k transitions. 1010 photons to converge in energy 1014 photons for spectropolarimetry Full runs calculated on NERSC’s IBM SP take ~50,000 hrs. IPAM Workshop IV: Transfer Phenomena

34. SYNPOL & 3-D Effects • We need the large number of photons since: • Polarization is low < 1% • Atmosphere changes quickly on short scales • Many lines to interact with… IPAM Workshop IV: Transfer Phenomena

35. A Hole in SNe Ia? A White Dwarf accretes material from a companion star, either a main sequence Star or a Red Giant. • The companion subtends an angle ~40o. • After explosion, the SN ejecta runs over the companion star in a few minutes to hours. • This may leave a ~40o hole in the SN ejecta . (Marietta et. al. 2000; c.f. Livne et. al. 1996) IPAM Workshop IV: Transfer Phenomena

36. A Hole in SNe Ia? IPAM Workshop IV: Transfer Phenomena

37. A Hole in SNe Ia? IPAM Workshop IV: Transfer Phenomena

38. A Hole in SNe Ia? IPAM Workshop IV: Transfer Phenomena

39. A Hole in SNe Ia? IPAM Workshop IV: Transfer Phenomena

40. Effect on Cosmology? IPAM Workshop IV: Transfer Phenomena

41. SN Factory Objective is to improve our understanding of Type Ia Supernovae for cosmology. Search is carried out at Palomar and Haleakela and spectrophotometric follow-up at UH 2.2-m and other telescopes like YALO. IPAM Workshop IV: Transfer Phenomena

42. SN Factory IPAM Workshop IV: Transfer Phenomena

43. SN Factory Not a slur, they picked it: FRench Observing Group of Supernova IPAM Workshop IV: Transfer Phenomena

44. SYNOW/MADSYN SYNOW employs the Sobolev approximation for the line transfer, as well as a “hard” photosphere and equivalent 2-level atoms in LTE. Highly parameterized and very fast. IPAM Workshop IV: Transfer Phenomena

45. SYNOW/MADSYN • Input for the photosphere: • Temperature • Velocity • Density (exp or pwr law) Input for the lines: • Optical depth • Min and Max velocity • Teff Runs in < 10 sec, almost all time is spent reading Kurucz linelist. IPAM Workshop IV: Transfer Phenomena

46. SYNOW/MADSYN IPAM Workshop IV: Transfer Phenomena

47. Conclusions • Many great nearby & high-redshift programs underway now • All will rely on computational modeling to improve our understanding of supernovae and to constrain systematics. • Understanding/Constraining 3-D effects will be important for “precision” cosmology…. IPAM Workshop IV: Transfer Phenomena