Lorenzo Amati INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Bologna INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Bologna XLIV Rencontres.

Lorenzo Amati INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Bologna INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Bologna XLIV Rencontres de Moriond La Thuile, February 1 - 8, 2009

Outline  Gamma-Ray Bursts: promising powerful cosmological probes  Cosmological parameters estimates with GRB:  GRB as cosmological tracers and beacons  Future perspectives  using GRB spectrum-energy correlations  including other GRB correlations  calibrating low-z GRBs with SN Ia

Outline  Gamma-Ray Bursts: promising powerful cosmological probes  Cosmological parameters estimates with GRB:  GRB as cosmological tracers and beacons  Conclusions and future perspectives  using GRB spectrum-energy correlations  including other GRB correlations  calibrating low-z GRBs with SN Ia

 isotropic distribution of GRBs directions  paucity of weak events with respect to homogeneous distribution in euclidean space  given the high fluences (up to more than 10 -4 erg/cm2 in 20-1000 keV) a cosmological origin would imply huge luminosity  thus, a “local” origin was not excluded until 1997 ! Early evidences for a cosmological origin of GRBs

 in 1997 discovery of afterglow emission by BeppoSAX  first X, optical, radio counterparts, host galaxies Establishing the GRB cosmological distance scale

 optical spectroscopy of afterglow and/or host galaxy –> first measurements of GRB redshift  redshifts higher than 0.1 and up to >6 -> GRB are cosmological  their isotropic equivalent radiated energy is huge (up to more than 10 54 erg in a few tens of s !)  fundamental input for origin of long / short GRB COSMOLOGY ?

 all GRBs with measured redshift (~170, including a few short GRB) lie at cosmological distances (z = 0.033 – 6.7) (except for the peculiar GRB980425, z=0.0085)  isotropic luminosities and radiated energy are huge and span several orders of magnitude: GRB are not standard candles (unfortunately) Are GRB standard candles ? Jakobsson, 2009Amati, 2006

 jet angles derived from break time of optical afterglow light curve by assuming standard scenario, are of the order of few degrees  the collimation-corrected radiated energy spans the range ~5x10 40 – 10 52 erg-> more clustered but still not standard Ghirlanda et al., 2004

 GRB have huge luminosity, a redshift distribution extending far beyond SN Ia  high energy emission -> no extinction problems  potentially powerful cosmological sources but need to investigate their properties to find ways to standardize them (if possible) Ghirlanda et al, 2006

 GRB F spectra typically show a peak at photon energy Ep  for GRB with known redshift it is possible to estimate the cosmological rest frame peak energy Ep,i and the radiated energy assuming isotropic emission, Eiso “Standardizing” GRB with spectrum-energy correlations log(Ep,i )= 2.52  = 0.43 log(Eiso)= 1.0,  = 0.9 Amati, 2006

 Amati et al. (2002) analyzed a sample of BeppoSAX events with known redshift finding evidence for a strong correlation between Ep,i and Eiso  Further analysis with updated samples (BATSE, HETE-2, KW, Swift) confirmed the correlation and extended it to the weakest and softest events  Significant extra-Poissonian scatter of the data around the best fit power- law:  ext [log(Ep,i)] ~ 0.17  Correlation not followed by short GRBs and peculiar sub-energetic GRBs Amati et al., 2008; Amati 2008

 redshift estimates available only for a small fraction of GRBs occurred in the last 10 years based on optical spectroscopy  pseudo-redshift estimates for the large amount of GRB without measured redshift -> GRB luminosity function, star formation rate evolution up to z > 6, etc.  use of the Ep,i – Eiso correlation for pseudo- redshift: most simple method is to study the track in the Ep,i - Eiso plane ad a function of z  not precise z estimates and possible degeneracy for z > 1.4  anyway useful for low z GRB and in general when combined with optical  A first step: using E p,i – E iso correlation for z estimates

 more refined: combine the Ep,i – Eiso correlation with other observables to construct GRB redshift estimators (es. Atteia, 2003, Pelangeon et al. 2006): pseudo-redshift of HETE-2 bursts published in GCN Atteia, A&A, 2003Pelangeon et al., 2006

 the E p,i -E iso correlation becomes tighter when adding a third observable : the optical afterglow break time tb (Liang & ZHang 2004), the jet opening angle derived from tb (  jet -> E  = [1-cos(  jet )]*E iso (Ghirlanda et al. 2004) or the “high signal time” T 0.45 (Firmani et al. 2006)  the logarithmic dispersion of these correlations seems low enough to allow their use to standardize GRB (Ghirlanda et al., Dai et al., Firmani et al., and many)  A step forward: standardizing GRBs with 3-parameters spectrum-energy correlations

 general purpouse: estimate c.l. contours in 2-param surface (e.g.  M -   )  general method: construct a chi-square statistics for a given correlation as a function of a couple cosmological parameters  method 1 – luminosity distance: fit the correlation and construct an Hubble diagram for each couple of cosmological parameters - > derive c.l. contours based on chi-square  Methods (e.g., Ghirlanda et al, Firmani et al., Dai et al., Zhang et al.) : E p,i = E p,obs x (1 + z) D l = D l (z, H 0,  M,  , …)

Ghirlanda et al., 2004  method 2 – minimum correlation scatter: for each couple of cosm.parameters compute Ep,i and Eiso (or E  ), fit the points with a pl and compute the chi-square -> derive c.l. contours based on chi-square surface  method 3: bayesian method assuming that the correlation exists and is unique Firmani et al. 2007

Ghirlanda, Ghisellini et al. 2005, 2006,2007  What can be obtained with 150 GRB with known z and Ep and complementarity with other probes (SN Ia, CMB)  complementary to SN Ia: extension to much higher z even when considering the future sample of SNAP (z < 1.7), cross check of results with different probes

 “Crisis” of 3-parameters spectrum-energy correlations ?  Recent debate on Swift outliers to the Ep-E  correlation (including both GRB with no break and a few GRB with chromatic break)  lack of jet breaks in several Swift X-ray afterglow light curves, in some cases, evidence of chromatic break: challenging jet and afterglow models  which break, which afterglow (X, opt), which GRBs can be used for Ep-E  ? Campana et al. 2007Ghirlanda et al. 2007

 recent analysis (Rossi et al. 2008, Schaefer et al. 2008), based on BeppoSAX and Swift GRBs that the dispersion of the Lp-Ep-T 0.45 correlation is significantly higher than thought before and that the Ep,i-Lp,iso-T0.45 correlation my be equivalent to the Ep,i-Eiso correlation Rossi et al. 2008

The genealogy and nomenclature of spectrum-energy correlations Ep,i – Eiso “Amati” 02 Ep,i – Liso 04 Ep,i – Lp,iso “Yonetoku”04 Ep,i – E  “Ghirlanda” 04 Ep,i – Eiso-tb “Liang-Zhang” 05 Ep,i – Lp,iso-T0.45 “Firmani” 06 Eiso LisoEiso Lp,iso tb,opt + jet modeltb,optT0.45 =

Ep,i – Eiso “Amati” 02 Ep,i – Liso 04 Ep,i – Lp,iso “Yonetoku”04 Ep,i – E  “Ghirlanda” 04 Ep,i – Eiso-tb “Liang-Zhang” 05 Ep,i – Lp,iso-T0.45 “Firmani” 06 Eiso LisoEiso Lp,iso tb,opt + jet modeltb,optT0.45 = The genealogy and nomenclature of spectrum-energy correlations

 Using the simple E p,i -E iso correlation for cosmology  Based on only 2 observables: a) much higher number of GRB that can be used b) reduction of systematics  Evidence that a fraction of the extrinsic scatter of the E p,i -E iso correlation is due to choice of cosmological parameters used to compute E iso Amati et al. 2008 Simple PL fit 70 GRB

 By using a maximum likelihood method the extrinsic scatter can be parametrized and quantified (e.g., D’Agostini 2005)   M can be constrained to 0.04-0.40 (68%) and 0.02-0.68 (90%) for a flat  CDM universe (  M = 1 excluded at 99.9% c.l.) Amati et al. 2008

 releasing assumption of flat universe still provides evidence of low  M, with a low sensitivity to    significant constraints on both  M and   expected from sample enrichment and z extension by present and next GRB experiments (e.g., Swift, Konus_WIND, Fermi, SVOM)  completely independent on other cosmological probes (e.g., CMB, type Ia SN, BAO; clusters…) and free of circularity problems Amati et al. 2008 70 REAL + 150 SIMUL

 physics of prompt emission still not settled, various scenarios: SSM internal shocks, IC-dominated internal shocks, external shocks, photospheric emission dominated models, kinetic energy dominated fireball, poynting flux dominated fireball)  e.g., Ep,i  -2 L 1/2 t -1 for syncrotron emission from a power-law distribution of electrons generated in an internal shock (Zhang & Meszaros 2002, Ryde 2005); for Comptonized thermal emission  geometry of the jet (if assuming collimated emission) and viewing angle effects also may play a relevant role  Drawbacks: lack of settled physical explanation

 physical explanations of the Ep,i – Eiso correlation in alternative GRB scenarios ‘Cannonball’ model (Dar et al.)‘Fireshell’ model (Ruffini et al.)

 Drawbacks: lack of calibration  differently to SN Ia, there are no low-redshift GRB (only 1 at z correlations cannot be calibrated in a “cosmology independent” way  would need calibration with a good number of events at z neeed to substantial increase the number of GRB with estimates of redshift and Ep  Bayesian methods have been proposed to “cure” the circularity problem (e.g., Firmani et al., 2006, Li et al. 2008), resulting in slightly reduced contours w/r to simple (and circularity free) scatter method (using L p,iso -E p,i -T 0.45 corr.)

 possible further improvements on cosmological parameter estimates by exploiting self-calibration with GRB at similar redshift or solid phyisical model for the correlation Amati et al. 2008 70 REAL + 150 SIMUL 70 REAL + 150 SIMUL 70 REAL

Luminosity-Variability correlation (Reichart et al., Guidorzi et al., Rizzuto et al.) Combining spectrum-energy correlations with other (less tight) GRB correlations (e.g., Schaefer 2007, Mosquera Cuesta et al. 2008) Luminosity-time lag correlation (Norris et al.)

 pseudo redshift estimates and GRB Hubble diagram  cosmological parameters consistent with standard cosmology with no dark energy evolution  drawbacks: no substantial improvements in estimation accuracy with respect to spectrum-energy correlations alone; adding other more dispersed correlations and new observables adds more systematics and uncertainties (and some correlations are not independent)

 Very recently, several authors (e.g., Kodama et al., 2008; Liang et al., 2008, Li et al. 2008) calibrated GRB spectrum—energy correlation at z < 1.7 by using the luminosity distance – redshift relation derived for SN Ia (e.g., Riess et al, 2007)  The aim is to extend the SN Ia Hubble diagram up to redshift where the luminosity distance is more sensitive to dark energy properties and evolution  Obtained significant constraints on both  M and   but with this method GRB are no more an indipendent cosmological probe Calibrating spectrum-energy correlations with SN Ia

 Because of the association with the death of massive stars GRB allow the study the evolution of massive star formation rate back to the early epochs of the Universe (z > 6)  several attempts to reconstruct the GRB luminosity function, and thus the massive SFR evolution have been done by using pseudo-z derived with GRB luminosity correlations (e.g., Yonetoku et al. 2004) GRB as tracers of star formation rate and cosmic beacons

 GRB can be used as cosmological beacons for study of the IGM up to z > 6 and the evolution of their host galaxy ISM back to the early epochs of the Universe (z > 6) EDGE Team

The future: what is needed ?  increase the number of z estimates, reduce selection effects and optimize coverage of the fluence-Ep plane in the sample of GRBs with known redshift  more accurate estimates of Ep,i by means of sensitive spectroscopy of GRB prompt emission from a few keV (or even below) and up to at least ~1 MeV  Swift is doing greatly the first job but cannot provide a high number of firm Ep estimates, due to BAT ‘narrow’ energy band (sensitive spectral analysis only from 15 up to ~200 keV)  in last years, Ep estimates for some Swift GRBs from Konus (from 15 keV to several MeV) and, to minor extent, RHESSI and SUZAKU NARROW BAND BROAD BAND

 2008: main contribution expected from joint Fermi + Swift measurements  Fermi/GBM (8-30000 keV) -> increase in number and accuracy of Ep measurements; Swift -> z estimate for simultaneously detected events; Fermi/LAT -> up to GeV for few  Up to now: about 110 GBM GRBs, 90 Ep estimates (82%), 14 detected and localized by Swift (13%), 4 detected and localized by LAT, 4 with z estimates (4%), 4 with Ep + z (4%)  2008 pre-Fermi : 61 Swift detections, 5 BAT Ep (8%), 15 BAT+KON+SUZ Ep estimates (25%), 20 redshift (33%), 11 Ep + z (16%)  Fermi provides a dramatic increase in Ep estimates (as expected), but only 14 Fermi GRBs have been detected / localized by Swift (13%) -> low number of Fermi GRBs with redshift. Will it be possible to improve this number ? BAT FOV much narrower than Fermi/GBM; similar orbits, each satellite limited by Earth occultation but at different times, … )

 In the > 2014 time frame a significant step forward expected from SVOM:  spectral study of prompt emission in 5-5000 keV -> accurate estimates of Ep and reduction of systematics (through optimal continuum shape determination and measurement of the spectral evolution down to X-rays)  fast and accurate localization of optical counterpart and prompt dissemination to optical telescopes -> increase in number of z estimates and reduction of selection effects  optimized for detection of XRFs, short GRB, sub- energetic GRB, high-z GRB  substantial increase of the number of GRB with known z and Ep -> test of correlations and calibration for their cosmological use

 use of GRB as cosmological beacons for absorption spectroscopy of the WHIM and galaxies ISM; GRB redshift and Ep  proposed to ESA CV as EDGE; will be proposed to NASA decadal survey as Xenia  Under study: GRB as cosmological beacons with EDGE/Xenia

 the quest for high-z GRB  for both cosmological parameters and SFR evolution studies it is of fundamental importance to increase the detection rate of high-z GRBs  Swift recently changed the BAT trigger threshold to this purpouse  the detection rate can be increased by lowering the low energy bound of the GRB detector trigger energy band Qui et al. 2009adapted from Salvaterra et al. 2007

 final remark: X-ray redshift measurements are possible !  a transient absorption edge at 3.8 keV was detected by BeppoSAX in the firs 13 s of the prompt emission of GRB 990705 (Amati et al. Science, 2000)  by interpreting this feature as a redhsifted neutral iron edge a redshift of 0.86+/-0.17 was estimated  the redshift was later confirmed by optical spectroscopy of the host galaxy (z = 0.842)

END OF THE TALK

BACK UP SLIDES

 Nakar & Piran and Band & Preece 2005: a substantial fraction (50-90%) of BATSE GRBs without known redshift are potentially inconsistent with the Ep,i-Eiso correlation for any redshift value  they suggest that the correlation is an artifact of selection effects introduced by the steps leading to z estimates: we are measuring the redshift only of those GRBs which follow the correlation  they predicted that Swift will detect several GRBs with Ep,i and Eiso inconsistent with the Ep,i-Eiso correlation  Ghirlanda et al. (2005), Bosnjak et al. (2005), Pizzichini et al. (2005): most BATSE GRB with unknown redshift are consistent with the Ep,i- Eiso correlation  different conclusions mostly due to the accounting or not for the dispersion of the correlation  Debate based on BATSE GRBs without known redshift

 Swift / BAT sensitivity better than BATSE for Ep ~100 keV but better than BeppoSAX/GRBM and HETE-2/FREGATE -> more complete coverage of the Ep-Fluence plane Band, ApJ, (2003, 2006) CGRO/BATSE Swift/BAT  Swift GRBs and selection effects Ghirlanda et al., MNRAS, (2008)

 fast (~1 min) and accurate localization (few arcesc) of GRBs -> prompt optical follow-up with large telescopes -> substantial increase of redshift estimates and reduction of selection effects in the sample of GRBs with known redshift  fast slew -> observation of a part (or most, for very long GRBs) of prompt emission down to 0.2 keV with unprecedented sensitivity –> following complete spectra evolution, detection and modelization of low-energy absorption/emission features -> better estimate of Ep for soft GRBs  drawback: BAT “narrow” energy band allow to estimate Ep only for ~15-20% of GRBs (but for some of them Ep from HETE-2 and/or Konus GRB060124, Romano et al., A&A, 2006

 all long Swift GRBs with known z and published estimates or limits to Ep,i are consistent with the correlation  the parameters (index, normalization,dispersion) obatined with Swift GRBs only are fully consistent with what found before  Swift allows reduction of selection effects in the sample of GRB with known z -> the Ep,i-Eiso correlation is passing the more reliable test: observations ! Amati 2006, Amati et al. 2008

 very recent claim by Butler et al.: 50% of Swift GRB are inconsistent with the pre-Swift Ep,i-Eiso correlation  but Swift/BAT has a narrow energy band: 15- 150 keV, nealy unesuseful for Ep estimates, possible only when Ep is in (or close to the bounds of ) the passband (15-20%) and with low accuracy  comparison of Ep derived by them from BAT spectra using Bayesian method and those MEASURED by Konus/Wind show they are unreliable  as shown by the case of GRB 060218, missing the soft part of GRB emission leads to overestimate of Ep

 Full testing and exploitation of spectral-energy correlations may be provided by EDGE in the > 2015 time frame  in 3 years of operations, EDGE will detect perform sensitive spectral analysis in 8-2500 keV for ~150-180 GRB  redshift will be provided by optical follow-up and EDGE X-ray absorption spectroscopy (use of microcalorimeters, GRB afterglow as bkg source)  substantial improvement in number and accuracy of the estimates of E p, which are critical for ultimately testing the reliability of spectral-energy correlations and their use for the estimates of cosmological parameters

 Evidence of two populations: 50% prompt + 50% exp “prompt” “tardy” Della Valle et al. 2005 Mannucci et al. 2005 Mannucci et al. 2006; Sullivan et al. 2006 Aubourg et al. 2007

Phillips’s relationship is calibrated on the “tardy” component  luminosity- decline rate relation might change with redshift??? Metallicity? (Nomoto et al. 2003 Dominguez et al. 2005)

Two scenarios for type Ia Double degenarate: where two C-O WDs in a binary systems make coalescence as result of the lost of orbital energy for GWs (Webbink 1984; Iben & Tutukov 1984) Single Degenerate (Whelan & Iben 1973, Nomoto 1982) Cataclysmic-like systems: RNe (WD+giant, WD+He) Symbiotic systems (WD+Mira or red giant) Supersoft X-ray Sources (WD+MS star) Both explosive channels are at play? maybe at different redshifts?  Differerent progenitors / explosion mechanisms ?

 Extinction factor: A B =R B x E(B-V)  for SNe-Ia in many cases R B  2-3 (Capaccioli et al. 1990, Della Valle & Panagia 1992, Phillips et al. 1999, Altavilla et al. 2004, Elias-Rosa et al. 2006, Wang et al. 2006)  more important at high-z

LONG  energy budget up to >10 54 erg  long duration GRBs  metal rich (Fe, Ni, Co) circum-burst environment  GRBs occur in star forming regions  GRBs are associated with SNe  naturally explained collimated emission  energy budget up to 10 51 - 10 52 erg  short duration GRBs (< 5 s)  clean circum-burst environment  GRBs in the outer regions of the host galaxy SHORT

 Very recently (Kodama et al., 2008; Liang et al., 2008) calibrated GRB spectrum—energy correlation at z < 1.7 by using the cosmology independent luminosity distance – redshift relation derived for SN Ia (RIess et al, 2007)  Obtained significant constraints on both  M and   but with this method GRB are no more an indipendent cosmological probe

 Combining spectrum-energy correlations with other (less tight) Luminosity correlations in GRB (Schaefer 2007)

 GRB can be used as cosmological beacons for study of the IGM up to z > 6  Because of the association with the death of massive stars GRB allow the study the evolution of massive star formation and the evolution of their host galaxy ISM back to the early epochs of the Universe (z > 6) GRB as cosmological beacons EDGE Team

Gamma-Ray Bursts: the brightest cosmological sources  most of the flux detected from 10-20 keV up to 1-2 MeV  measured rate (by an all-sky experiment on a LEO satellite): ~0.8 / day; estimated true rate ~2 / day  bimodal duration distribution  fluences (= av.flux * duration) typically of ~10 - 7 – 10 -4 erg/cm 2 short long

 possible further improvements on cosmological parameter estimates by exploiting self-calibration with GRB at similar redshift or solid phyisical model for the correlation Amati et al. 2008 70 REAL + 150 SIMUL 70 REAL + 150 SIMUL 70 REAL

 given their redshift distribution (0.033 - 6.3 up to now), GRB are potentially the best-suited probes to study properties and evolution of “dark energy” Amati et al. 2008 70 REAL (flat,  m=0.27) 70 REAL + 150 SIMUL (flat) (e.g.,Chevalier & Polarski, Linder & Utherer)

 Eiso is the GRB brightness indicator with less systematic uncertainties:  Liso is affected by the often uncertain GRB duration (e.g., long tails of Swift GRB);  Lp,iso is affected by the lack of or poor knowledge of spectral shape of the peak emisison (the time average spectrum is often used) and by the subjective choice and inhomogeneity in z of the peak time scale  Comparison with three-parameters correlations: reduced scatter, but…  addition of a third observable introduces further uncertainties (difficulties in measuring t_break, chromatic breaks, model assumptions, subjective choice of the energy band in which compute T0.45, inhomogeneity on z of T0.45) and substantially reduces the number of GRB that can be used (e.g., #Ep,i – E  ~ ¼ #Ep,i – Eiso )  recent evidences that dispersion of Ep,i-Lp,iso-T0.45 correlation is comparable to that of Ep,i - Eiso and debates on possible outliers / higher dispersion of the Ep-E  and Ep-Eiso-tb correlations (but see talk by Ghirlanda) Ep,i – Eiso correlation vs. the other spectrum-energy correlations

Complementarity to other probes: the case of SN Ia  Several possible systematics may affect the estimate of cosmological parameters with SN Ia, e.g.:  different explosion mechanism and progenitor systems ? May depend on z ?  light curve shape correction for the luminosity normalisation may depend on z  signatures of evolution in the colours  correction for dust extinction  anomalous luminosity-color relation  contaminations of the Hubble Diagram by no-standard SNe-Ia and/or bright SNe-Ibc (e.g. HNe) Kowalski et al. 2008

 The Hubble diagram for type Ia SNe may be significantly affected by systematics -> need to carry out independent measurement of   and    GRBs allow us today to change the “experimental methodology” and provide an independent measurement of the cosmological parameters:  GRBs are extremely bright and detectable out of cosmological distances (z=6.3 Kuwai et al. 2005, Tagliaferri et al. 2005) -> interesting objects for cosmology  SNe-Ia are currently observed at z<1.7: GRBs appear to be (in principle) the only class of objects capable to study the evolution of the dark energy from the beginning (say from z~7-8)  No need of correction for reddening  Different orientation of the contours

 Given their huge luminosities and redshift distribution extending up to at least 6.3, GRB are a powerful tool for cosmology and complementary to other probes (CMB, SN Ia, BAO, clusters, etc.)  The use of Ep,i – Eiso correlation to this purpouse is promising (already significant constraints on  m, in agreement with “concordance cosmology), but:  need to substantial increase of the # of GRB with known z and Ep (which will be realistically allowed by next GRB experiments: Swift+GLAST/GBM, SVOM,…)  auspicable solid physical interpretation  identification and understanding of possible sub- classes of GRB not following correlations Conclusions Conclusions

Complementarity to other probes: the case of SN Ia  Several possible systematics may affect the estimate of cosmological parameters with SN Ia, e.g.:  different explosion mechanism and progenitor systems ? May depend on z ?  light curve shape correction for the luminosity normalisation may depend on z  signatures of evolution in the colours  correction for dust extinction  anomalous luminosity-color relation  contaminations of the Hubble Diagram by no-standard SNe-Ia and/or bright SNe-Ibc (e.g. HNe) Kowalski et al. 2008

 The Hubble diagram for type Ia SNe may be significantly affected by systematics -> need to carry out independent measurement of   and    GRBs allow us today to change the “experimental methodology” and provide an independent measurement of the cosmological parameters:  GRBs are extremely bright and detectable out of cosmological distances (z=6.3 Kuwai et al. 2005, Tagliaferri et al. 2005) -> interesting objects for cosmology  SNe-Ia are currently observed at z<1.7: GRBs appear to be (in principle) the only class of objects capable to study the evolution of the dark energy from the beginning (say from z~7-8)  No need of correction for reddening  Different orientation of the contours

Complementarity to other probes: the case of SN Ia  Several possible systematics may affect the estimate of cosmological parameters with SN Ia, e.g.:  different explosion mechanism and progenitor systems ? May depend on z ?  light curve shape correction for the luminosity normalisation may depend on z  signatures of evolution in the colours  correction for dust extinction  anomalous luminosity-color relation  contaminations of the Hubble Diagram by no-standard SNe-Ia and/or bright SNe-Ibc (e.g. HNe)

Lorenzo Amati INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Bologna INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Bologna XLIV Rencontres.

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Lorenzo Amati INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Bologna INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Bologna XLIV Rencontres.

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Presentation on theme: "Lorenzo Amati INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Bologna INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Bologna XLIV Rencontres."— Presentation transcript:

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