J/ApJ/732/65 Modeling the local velocity field with SNIa (Weyant+, 2011)
An unbiased method of modeling the local peculiar velocity field with type Ia
supernovae.
Weyant A., Wood-Vasey M., Wasserman L., Freeman P.
<Astrophys. J., 732, 65 (2011)>
=2011ApJ...732...65W 2011ApJ...732...65W
ADC_Keywords: Supernovae ; Redshifts ; Models
Keywords: methods: statistical - supernovae: general
Abstract:
We apply statistically rigorous methods of nonparametric risk
estimation to the problem of inferring the local peculiar velocity
field from nearby Type Ia supernovae (SNIa). We use two nonparametric
methods -weighted least squares (WLS) and coefficient unbiased (CU)-
both of which employ spherical harmonics to model the field and use
the estimated risk to determine at which multipole to truncate the
series. We show that if the data are not drawn from a uniform
distribution or if there is power beyond the maximum multipole in the
regression, a bias is introduced on the coefficients using WLS. CU
estimates the coefficients without this bias by including the sampling
density making the coefficients more accurate but not necessarily
modeling the velocity field more accurately. After applying
nonparametric risk estimation to SNIa data, we find that there are not
enough data at this time to measure power beyond the dipole. The WLS
Local Group bulk flow is moving at 538±86km/s toward
(l,b)=(258±10°,36±11°) and the CU bulk flow is moving at
446±101km/s toward (l,b)=(273±11°,46±8°). We find that
the magnitude and direction of these measurements are in agreement
with each other and previous results in the literature.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 76 126 SNIa data
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See also:
B/sn : Asiago Supernova Catalogue (Barbon et al., 1999-)
J/ApJS/192/1 : Light-curve parameters from the SNLS (Conley+, 2011)
J/MNRAS/412/1441 : SNe luminosity functions (Li+, 2011)
J/MNRAS/412/1419 : Nearby supernova rates (Leaman+, 2011)
J/MNRAS/410/1262 : SN Legacy Survey. Type Ia supernovae (Walker+, 2011)
J/A+A/523/A7 : Light curves of type Ia supernovae in SNLS (Guy+, 2010)
J/AJ/139/120 : Low-redshift Type-Ia supernovae (Folatelli+, 2010)
J/ApJS/190/418 : Light curves for 165 SNe (Ganeshalingam+, 2010)
J/ApJ/700/1097 : Light curve parameters of SN Ia (Hicken+, 2009)
J/ApJ/700/331 : Light curves of type Ia supernovae (CfA3) (Hicken+, 2009)
J/A+A/507/85 : ESO/VLT 3rd year type Ia supernova data (Balland+, 2009)
J/ApJ/666/674 : ESSENCE supernova survey (Miknaitis+, 2007)
J/ApJ/659/122 : Improved distances to type Ia supernovae (Jha+, 2007)
http://snfactory.lbl.gov/ : Nearby SN Factory home page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- SN SN name (YYYYaa) (1)
8- 9 I2 h RAh Hour of right ascension (J2000) (2)
11- 12 I2 min RAm Minute of right ascension (J2000)
14- 18 F5.2 s RAs Second of right ascension (J2000)
20 A1 --- DE- Sign of declination (J2000) (2)
21- 22 I2 deg DEd Degree of declination (J2000) (2)
24- 25 I2 arcmin DEm Arcminute of declination (J2000)
27- 30 F4.1 arcsec DEs Arcsecond of declination (J2000)
32- 36 F5.3 --- z [0.003/0.028] Redshift in the rest frame of
the cosmic microwave background
38- 42 F5.3 --- e_z [0.001] z uncertainty
44- 49 F6.3 mag mu [28.012/35.282] Distance modulus (µ)
51- 55 F5.3 mag e_mu mu uncertainty
57- 61 F5.3 mag Av [0.006/3.134] Extinction
63- 67 F5.3 mag e_Av Av uncertainty
69- 72 I4 km/s UVel [-942/2423]? Peculiar velocity (U) (3)
74- 76 I3 km/s e_UVel [322/741]? UVel uncertainty (4)
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Note (1): Our data consist of SNIa published in Hicken et al. (H09b; 2009,
Cat. J/ApJ/700/331), Jha et al. (2007, Cat. J/ApJ/659/122), Hamuy et
al. (1996AJ....112.2391H 1996AJ....112.2391H), and Riess et al. (1999AJ....117..707R 1999AJ....117..707R)
using the distance measurements published in Hicken et al. (H09a;
2009, Cat. J/ApJ/700/1097). Not all of the SNIa published in H09b have
distance measurements published in H09a. The rest were obtained from
private communication with the author.
Note (2): SNIa RA and DEC (J2000) from:
http://www.cfa.harvard.edu/iau/lists/Supernovae.html
Note (3): The peculiar velocity, U, is calculated according to (see Jha et al.
2007, Cat. J/ApJ/659/122): U=H0,dl(z)-H0dSN (see equation 37
and section 5.1 for further details).
Note (4): Includes the error on µ, a recommended error of 0.078mag (see
Hicken et al., 2009, Cat. J/ApJ/700/1097), σz, and a peculiar
velocity error of σν=300km/s due to local motions on scales
smaller than those probed by this analysis.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 31-Oct-2012