J/A+A/500/L17 Spectral flux ratio of SN Ia (Bailey+, 2009)
Using spectral flux ratios to standardize SN Ia luminosities.
Bailey S., Aldering G., Antilogus P., Aragon C., Baltay C., Bongard S.,
Buton C., Childress M., Chotard N., Copin Y., Gangler E., Loken S.,
Nugent P., Pain R., Pecontal E., Pereira R., Perlmutter S., Rabinowitz D.,
Rigaudier G., Runge K., Scalzo R., Smadja G., Swift H., Tao C.,
Thomas R.C., Wu C.
<Astron. Astrophys. 500, L17 (2009)>
=2009A&A...500L..17B 2009A&A...500L..17B
ADC_Keywords: Supernovae ; Spectrophotometry
Keywords: stars: supernovae: general - cosmology: observations
Abstract:
We present a new method to standardize Type Ia supernova (SN Ia)
luminosities to ~<0.13mag using flux ratios from a single
flux-calibrated spectrum per SN. Using Nearby Supernova Factory
spectrophotometry of 58 SNe Ia, we performed an unbiased search for
flux ratios that correlate with SN Ia luminosity. After developing the
method and selecting the best ratios from a training sample, we
verified the results on a separate validation sample and with data
from the literature. We identified multiple flux ratios whose
correlations with luminosity are stronger than those of light curve
shape and color, previously identified spectral feature ratios, or
equivalent width measurements. In particular, the flux ratio
R(642/443)=Flux(642nm)/Flux(443nm) has a correlation of 0.95 with SN
Ia absolute magnitudes. Using this single ratio as a correction factor
produces a Hubble diagram with a residual scatter standard deviation
of 0.125±0.011mag, compared with 0.161±0.015mag when fit with the
SALT2 light curve shape and color parameters x1 and c. The ratio
R(642/443) is an effective correction factor for both extrinsic dust
reddening and intrinsic variations such as those of SN 1991T-like and
SN 1999aa-like SNe. When combined with broad-band color measurements,
spectral flux ratios can standardize SN Ia magnitudes to ∼0.12mag.
These are the first spectral metrics that give robust improvements
over the standard normalization methods based upon light curve shape
and color, and they provide among the lowest scatter Hubble diagrams
ever published.
Description:
These tables provide the names, redshifts, lightcurve fit parameters,
and measured flux ratios for the SNe.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 88 11 Flux Ratio correlations and Hubble residual stdev
table2.dat 130 74 *SALT2 fit and R(642/443) flux ratios
table3.dat 203 58 All flux ratios R, Rc for SNfactory SNe
--------------------------------------------------------------------------------
Note on table2.dat: SALT2 parameters x1 and c and the decolored flux ratio
Rc(642/443) were not measured or used for the literature SNe in this
analysis, thus they are not included in this table.
--------------------------------------------------------------------------------
See also:
B/sn : Asiago Supernova Catalogue (Barbon et al., 1999-)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- FitParms Hubble fit standardization parameters
14- 17 F4.2 --- rho.T Correlations in Training set
20- 23 F4.2 --- rho.V Correlations in Validation set
26- 29 F4.2 --- rho.C Correlations in Combined set
31- 34 F4.1 --- Gamma ?=- Flux ratio fit slope
36- 38 F3.1 --- e_Gamma ?=- Flux ratio fit slope error
42- 46 F5.3 mag sig.T Hubble residuals stdev Training set
48- 52 F5.3 mag e_sig.T stdev errors Training set
56- 60 F5.3 mag sig.V Hubble residuals stdev Validation set
62- 66 F5.3 mag e_sig.V stdev errors Validation set
70- 74 F5.3 mag sig.C Hubble residuals stdev Combined set
76- 80 F5.3 mag e_sig.C stdev errors Combined set
84- 88 F5.3 mag sigma Normalized Median Absolute Deviation
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- Name SN Name
17 A1 --- Set [TVL] T=Training, V=Validation, L=Literature
19- 24 F6.4 --- zcmb Redshift in CMB frame
27- 31 F5.2 --- x1 ?=- SALT2 x1 light curve shape parameter
34- 37 F4.2 --- e_x1 ?=- SALT2 x1 parameter error
39- 44 F6.3 mag color ?=- SALT2 color parameter [∼E(B-V)]
46- 50 F5.3 mag e_color ?=- SALT2 color parameter error
52- 57 F6.3 mag dmuB Uncorrected Hubble diagram residual
59- 63 F5.3 mag e_dmuB Hubble diagram residual error
66- 70 F5.3 --- R642/443 Flux ratio R(642/443)
73- 77 F5.3 --- e_R642/443 Flux ratio R(642/443) error
80- 84 F5.3 --- Rc642/443 ?=- Decolored Flux ratio Rc(642/443)
87- 91 F5.3 --- e_Rc642/443 ?=- Decolored Flux ratio Rc(642/443) error
93-130 A38 --- Ref Non-SNfactory discovery reference
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- Name SN Name
17 A1 --- Set [TV] T=Training, V=Validation
19- 24 F6.4 --- zcmb Redshift in CMB frame (1)
27- 31 F5.2 --- x1 SALT2 x1 light curve shape parameter
34- 37 F4.2 --- e_x1 SALT2 x1 parameter error
39- 44 F6.3 mag color SALT2 color parameter ∼E(B-V)
46- 50 F5.3 mag e_color SALT2 color parameter error
52- 57 F6.3 mag dmuB Uncorrected Hubble diagram residual
59- 63 F5.3 mag e_dmuB Hubble diagram residual error
66- 70 F5.3 --- R642/443 Flux ratio R(642/443)
73- 77 F5.3 --- e_R642/443 Flux ratio R(642/443) error
80- 84 F5.3 --- R642/417 Flux ratio R(642/417)
87- 91 F5.3 --- e_R642/417 Flux ratio R(642/417) error
94- 98 F5.3 --- R772/437 Flux ratio R(772/437)
101-105 F5.3 --- e_R772/437 Flux ratio R(772/437) error
108-112 F5.3 --- R642/512 Flux ratio R(642/512)
115-119 F5.3 --- e_R642/512 Flux ratio R(642/512) error
122-126 F5.3 --- R728/398 Flux ratio R(728/398)
129-133 F5.3 --- e_R728/398 Flux ratio R(728/398) error
136-140 F5.3 --- Rc642/519 Decolored Flux ratio Rc(642/519)
143-147 F5.3 --- e_Rc642/519 Decolored Flux ratio Rc(642/519) error
150-154 F5.3 --- Rc577/642 Decolored Flux ratio Rc(577/642)
157-161 F5.3 --- e_Rc577/642 Decolored Flux ratio Rc(577/642) error
164-168 F5.3 --- Rc642/536 Decolored Flux ratio Rc(642/536)
171-175 F5.3 --- e_Rc642/536 Decolored Flux ratio Rc(642/536) error
178-182 F5.3 --- Rc676/642 Decolored Flux ratio Rc(676/642)
185-189 F5.3 --- e_Rc676/642 Decolored Flux ratio Rc(676/642) error
192-196 F5.3 --- Rc642/443 Decolored Flux ratio Rc(642/443)
199-203 F5.3 --- e_Rc642/443 Decolored Flux ratio Rc(642/443) error
--------------------------------------------------------------------------------
Note (1): Reference for non-SNfactory redshifts are from:
de Vaucouleurs et al., RC3, Cat. VII/155
Keel, 1996, Cat. J/ApJS/106/27
Mathewson & Ford, 1996, Cat. J/ApJS/107/97
Theureau et al., 1998, Cat. J/A+AS/130/333
Huchra et al., 1999, Cat. J/ApJS/121/287
Falco et al., 1999, Cat. J/PASP/111/438
Koribalski et al., 2004, Cat. J/AJ/128/16
O'Neil, 2004, Cat. J/AJ/128/2080
Jones et al., 6dF, 2005i, Cat. VII/249
SDSS Data Release 7
--------------------------------------------------------------------------------
Acknowledgements:
Stephen Bailey, stephen.bailey(at)in2p3.fr
(End) Stephen Bailey [LPNHE Paris], Patricia Vannier [CDS] 02-Jul-2009