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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
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:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 76 126 SNIa data
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
Bytes Format Units Label Explanations
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)
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), and Riess et al. (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.
History: From electronic version of the journal
(End) Emmanuelle Perret [CDS] 31-Oct-2012
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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