Open AccessComparing the SFI peculiar velocities with the PSC z gravity field: a VELMOD analysis
Author(s) -
Branchini E.,
Freudling W.,
Da Costa L.N.,
Frenk C.S.,
Giovanelli R.,
Haynes M.P.,
Salzer J.J.,
Wegner G.,
Zehavi I.
Publication year - 2001
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2001.04671.x
Subject(s) - physics , astrophysics , galaxy , redshift , peculiar velocity , redshift survey , gravitational field , redshift space distortions , velocity dispersion , smoothing , spiral galaxy , field (mathematics) , astronomy , statistics , mathematics , pure mathematics
We compare the peculiar velocities derived from the I ‐band Tully–Fisher (TF) relation for 989 field spiral galaxies in the SFI catalogue with the predicted velocity field derived from the IRAS PSC z galaxy redshift survey. We assume linear gravitational instability theory and apply the maximum likelihood technique, VELMOD to SFI galaxies within a redshift cz LG =6000 km s −1 . The resulting calibration of the TF relation is consistent with a previous, independent calibration for a similar sample of spirals residing in clusters. Our analysis provides an accurate estimate of the quantity β I ≡ Ω m 0.6 /b I , where b I is the linear biasing parameter for IRAS galaxies. Using the forward TF relation and smoothing the predicted velocity field with a Gaussian filter of radius 300 km s −1 , we obtain β I =0.42±0.04 (1 σ uncertainty). This value, as well as other parameters in the fit, are robust to varying the smoothing radius to 500 km s −1 and splitting the sample into spherical shells in redshift space. The one exception is the small‐scale velocity dispersion, σ v , which varies from ∼ 200 km s −1 (within cz LG =4000 km s −1 ) to ∼ 500 km s −1 at larger distance. For β I ≃0.42 , the residuals between the TF data and the PSC z gravity field are uncorrelated, indicating that the model provides a good fit to the data. More generally, a χ 2 statistic indicates that the PSC z model velocity field provides an acceptable (3 σ ) fit to the data for 0.3<β I <0.5 .