We present the results of the 2MASS Redshift Survey (2MRS), a ten-year project to map the full three-dimensional distribution of galaxies in the nearby Universe. The 2 Micron All-Sky Survey (2MASS) was completed in 2003 and its final data products, including an extended source catalog (XSC), are available on-line. The 2MASS XSC contains nearly a million galaxies with K s ≤ 13.5 mag and is essentially complete and mostly unaffected by interstellar extinction and stellar confusion down to a galactic latitude of |b| = 5 • for bright galaxies. Near-infrared wavelengths are sensitive to the old stellar populations that dominate galaxy masses, making 2MASS an excellent starting point to study the distribution of matter in the nearby Universe.We selected a sample of 44,599 2MASS galaxies with K s ≤ 11.75 mag and |b| ≥ 5 • (≥ 8 • towards the Galactic bulge) as the input catalog for our survey. We obtained spectroscopic observations for 11,000 galaxies and used previously-obtained velocities for the remainder of the sample to generate a redshift catalog that is 97.6% complete to well-defined limits and covers 91% of the sky. This provides an unprecedented census of galaxy (baryonic mass) concentrations within 300 Mpc.Earlier versions of our survey have been used in a number of publications that have studied the bulk motion of the Local Group, mapped the density and peculiar velocity fields out to 50 h −1 Mpc, detected galaxy groups, and estimated the values of several cosmological parameters.Additionally, we present morphological types for a nearly-complete sub-sample of 20,860 galaxies with K s ≤ 11.25 mag and |b| ≥ 10 • .
Citation for published item:pringoD ghristopher wF nd wgoulsD ghristin nd gollessD wtthew nd wouldD teremy nd irdogduD irin nd tonesD hF reth nd vueyD tohn F nd gmpellD vhln nd plukeD ghristopher tF @PHIRA 9he Tdp qlxy urvey X peulir veloity (eld nd osmogrphyF9D wonthly noties of the oyl estronomil oietyFD RRS @QAF ppF PTUUEPTWUF Further information on publisher's website: Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACTWe derive peculiar velocities for the 6dF Galaxy Survey (6dFGS) and describe the velocity field of the nearby (z < 0.055) Southern hemisphere. The survey comprises 8885 galaxies for which we have previously reported Fundamental Plane data. We obtain peculiar velocity probability distributions for the redshift-space positions of each of these galaxies using a Bayesian approach. Accounting for selection bias, we find that the logarithmic distance uncertainty is 0.11 dex, corresponding to 26 per cent in linear distance. We use adaptive kernel smoothing to map the observed 6dFGS velocity field out to cz ∼ 16 000 km s −1 , and compare this to the predicted velocity fields from the PSCz Survey and the 2MASS Redshift Survey. We find a better fit to the PSCz prediction, although the reduced χ 2 for the whole sample is approximately unity for both comparisons. This means that, within the observational uncertainties due to redshift-independent distance errors, observed galaxy velocities and those predicted by the linear approximation from the density field agree. However, we find peculiar velocities that are systematically more positive than model predictions in the direction of the Shapley and Vela superclusters, and systematically more negative than model predictions in the direction of the Pisces-Cetus Supercluster, suggesting contributions from volumes not covered by the models.
We estimate the acceleration on the Local Group (LG) from the 2 Micron All-Sky Redshift Survey (2MRS). The sample used includes about 23 200 galaxies with extinction-corrected magnitudes brighter than K s = 11.25 and it allows us to calculate the flux-weighted dipole. The near-infrared flux-weighted dipoles are very robust because they closely approximate a mass-weighted dipole, bypassing the effects of redshift distortions and require no preferred reference frame. This is combined with the redshift information to determine the change in dipole with distance. The misalignment angle between the LG and the cosmic microwave background (CMB) dipole drops to 12 • ± 7 • at around 50 h −1 Mpc, but then increases at larger distances, reaching 21 • ± 8 • at around 130 h −1 Mpc. Exclusion of the galaxies Maffei 1, Maffei 2, Dwingeloo 1, IC342 and M87 brings the resultant flux dipole to 14 • ± 7 • away from the CMB velocity dipole. In both cases, the dipole seemingly converges by 60 h −1 Mpc. Assuming convergence, the comparison of the 2MRS flux dipole and the CMB dipole provides a value for the combination of the mass density and luminosity bias parameters 0.6 m /b L = 0.40 ± 0.09.
We report a direct observational evidence for the existence of the galaxy spin alignments with the real space tidal field. We calculate the real space tidal field from the real space density field reconstructed recently from the Two Mass Redshift Survey (2MRS) by Erdogdu et al. in 2006. Using a total of 12122 nearby spiral galaxies from the Tully Galaxy Catalog, we calculate the orientations of their spin axes relative to the 2MRS tidal field. We find a clear signal of the intrinsic correlations between the galaxy spins and the intermediate principal axes of the tidal shears. The null hypothesis of no correlation is rejected at 99.99% confidence level. We also investigate the dependence of the intrinsic correlations on the galaxy morphological type and the environment. It is found that (i) the intrinsic correlation depends weakly on the morphological type of the spiral galaxies but tends to decrease slightly as the type increases; (ii) it is stronger in the high-density regions than in the low-density regions. The observational result is quantitatively consistent with analytic prediction based on the tidal torque theory. It is concluded that the galaxy spin orientations may provide in principle a new complimentary probe of the dark matter distribution.
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