IRAS Redshift Survey Research Articles

Cosmological Parameters from the Comparison of the 2MASS Gravity Field with Peculiar Velocity Surveys

We compare the peculiar velocity field within 65 $h^{-1}$ Mpc predicted from 2MASS photometry and public redshift data to three independent peculiar velocity surveys based on type Ia supernovae, surface brightness fluctuations in ellipticals, and Tully-Fisher distances to spirals. The three peculiar velocity samples are each in good agreement with the predicted velocities and produce consistent results for $\beta_{K}=\Omega\sbr{m}^{0.6}/b_{K}$. Taken together the best fit $\beta_{K} = 0.49 \pm 0.04$. We explore the effects of morphology on the determination of $\beta$ by splitting the 2MASS sample into E+S0 and S+Irr density fields and find both samples are equally good tracers of the underlying dark matter distribution, but that early-types are more clustered by a relative factor $b\sbr{E}/b\sbr{S} \sim 1.6$. The density fluctuations of 2MASS galaxies in $8 h^{-1}$ Mpc spheres in the local volume is found to be $\sigma\sbr{8,K} = 0.9$. From this result and our value of $\beta_{K}$, we find $\sigma_8 (\Omega\sbr{m}/0.3)^{0.6} = 0.91\pm0.12$. This is in excellent agreement with results from the IRAS redshift surveys, as well as other cosmological probes. Combining the 2MASS and IRAS peculiar velocity results yields $\sigma_8 (\Omega\sbr{m}^/0.3)^{0.6} = 0.85\pm0.05$.

Constraining the Cosmic Mass Density from the SBF Survey Peculiar Velocities

The recently completed I-band SBF Survey of Galaxy Distances contains about 300 galaxy distances within cz ≲ 4000 km/s. These data allow for good constraints on the local mass density and velocity fields. The mass density parameter βI ≡ Ω0.6/bI, where bI is the biasing factor of the IRAS redshift survey galaxies, is found to be βI ≍ 0.45.

Nonnucleosynthetic Constraints on the Baryon Density and Other Cosmological Parameters

Because the baryon-to-photon ratio ?10 is in some doubt, we drop nucleosynthetic constraints on ?10 and fit the three cosmological parameters (h, ?M, ?10) to four observational constraints: Hubble parameter ho = 0.70 ? 0.15, age of the universe t=14 Gyr, cluster gas fraction fo ? fG h3/2 = 0.060 ? 0.006, and effective shape parameter ?o = 0.255 ? 0.017. Errors quoted are 1 ?, and we assume Gaussian statistics. We experiment with a fifth constraint ?o = 0.2 ? 0.1 from clusters. We set the tilt parameter n = 1 and the gas enhancement factor = 0.9. We consider cold dark matter models (open and ?M = 1) and flat ?CDM models. We omit HCDM models (to which the ?o constraint does not apply). We test goodness of fit and draw confidence regions by the ??2 method. CDM models with ?M = 1 (SCDM models) are accepted only because the large error on ho allows h < 0.5. Baryonic matter plays a significant role in ?o when ?M ~ 1. Open CDM models are accepted only for ?M 0.4. The combination of the four other constraints with ?o ? 0.2 is rejected in CDM models with 98% confidence, suggesting that light may not trace mass. ?CDM models give similar results. In all of these models, ?10 6 is favored strongly over ?10 2. This suggests that reports of low deuterium abundances on QSO lines of sight may be correct and that observational determinations of primordial 4He may have systematic errors. Plausible variations on n and in our models do not change the results much. If we drop or change the crucial ?o constraint, lower values of ?M and ?10 are permitted. The constraint ?o = 0.15 ? 0.04, derived recently from the IRAS redshift survey, favors ?M ? 0.3 and ?10 ? 5 but does not exclude ?10 ? 2.

Searching for the scale of homogeneity

ABSTRA C T We introduce a statistical quantity, known as the K function, related to the integral of the twopoint correlation function. It gives us straightforward information about the scale where clustering dominates and the scale at which homogeneity is reached. We evaluate the correlation dimension, D2, as the local slope of the log‐log plot of the K function. We apply this statistic to several stochastic point fields, to three numerical simulations describing the distribution of clusters and finally to real galaxy redshift surveys. Four different galaxy catalogues have been analysed using this technique: the Center for Astrophysics I, the Perseus‐Pisces redshift surveys (these two lying in our local neighbourhood), the Stromlo‐ APM and the 1.2-Jy IRAS redshift surveys (these two encompassing a larger volume). In all cases, this cumulant quantity shows the fingerprint of the transition to homogeneity. The reliability of the estimates is clearly demonstrated by the results from controllable point sets, such as the segment Cox processes. In the cluster distribution models, as well as in the real galaxy catalogues, we never see long plateaus when plotting D2 as a function of the scale, leaving no hope for unbounded fractal distributions.

Non-linear cosmological power spectra in real and redshift space

We present an expression for the nonlinear evolution of the cosmological power spectrum based on following Lagrangian trajectories. This is simplified using the Zel'dovich approximation to trace particle displacements, assuming Gaussian initial conditions. The model is found to exhibit the transfer of power from large to small scales expected in self- gravitating fields. We have extended this analysis into redshift-space and found a solution for the nonlinear, anisotropic redshift-space power spectrum in the limit of plane--parallel redshift distortions. The quadrupole-to- monopole ratio is calculated for the case of power-law initial spectra. We find that the shape of this ratio depends on the shape of the initial spectrum, but when scaled to linear theory depends only weakly on the redshift-space distortion parameter, $\beta$. The point of zero-crossing of the quadrupole, $k_0$, is found to obey a scaling relation. This model is found to be in agreement with $N$-body simulations on scales down to the zero-crossing of the quadrupole, although the wavenumber at zero-crossing is underestimated. These results are applied to the quadrupole--monopole ratio found in the merged QDOT+1.2 Jy IRAS redshift survey. We have estimated that the distortion parameter is constrained to be $\beta>0.5$ at the $95 \%$ level. The local primordial spectral slope is not well constrained, but analysis suggests $n \approx -2$ in the translinear regime. The zero-crossing scale of the quadrupole is $k_0=0.5 \pm 0.1 h/Mpc$ and from this we infer the amplitude of clustering is $\sigma_8=0.7 \pm 0.05$. We suggest that the success of this model is due to nonlinear redshift--space effects arising from infall onto caustics and is not dominated by virialised cluster cores.

A Gravitational Lens Solution for the [ITAL]IRAS[/ITAL] Galaxy FSC 10214+4724

We show that the z = 2.3 IRAS source FSC 10214+4724 is gravitationally lensed by an intervening elliptical galaxy. Its many anomalous properties can be explained if the active galactic nucleus (AGN) region of the source is much more magnified than its outer regions. We uncover a small counterimage to the arc adjacent to the lensing galaxy, as predicted by our lens model. A redshift of unity for the lens is suggested by a red component in the observed spectrum, yielding a lensing mass interior to the critical radius of M(r < 3 kpc) ≈ 1011 M☉, consistent with an ordinary massive galaxy. We present new high-resolution optical images which show a thin arc of emission, implying that the optical source is compact (less than 0.5 kpc) and highly magnified (more than 20 times). Since the optical emission is known to be strongly polarized and Seyfert 2, we propose that the optical arc is a highly magnified image of the inner mirror region of an obscured AGN. The central obscuring torus will be similarly magnified, naturally accounting for the large IR flux. We propose that cases like F10214 represent the obscured AGN counterparts to the lensed QSO population, and find that the probability of finding objects like F10214 in IRAS redshift surveys is reasonably large.

Statistics of peculiar velocities from cosmic strings

We calculate the probability distribution of a single component of peculiar velocities due to cosmic strings, smoothed over regions with a radius of several $h^{-1}$ Mpc. The probability distribution is shown to be Gaussian to good accuracy, in agreement with the distribution of peculiar velocities deduced from the 1.9 Jy IRAS redshift survey. Using the normalization of parameters of the cosmic string model from CMB measurements, we show that the rms values for peculiar velocities inferred from IRAS are consistent with the cosmic string model provided that long strings have some small-scale structure.

The Puppis cluster of galaxies behind the Galactic plane and the origin of the 'Local Anomaly'

Recent surveys of galaxies behind the Galactic plane have revealed the Puppis cluster, centred at l approximately 240-degrees, b approximately 0-degrees and redshift cz approximately 1000-2000 km s-1. We supplement the recent 2-Jy IRAS redshift survey of Strauss et al. for absolute value of b > 5-degrees with an IRAS-selected sample in the direction of Puppis (absolute value of b < 5-degrees; 230-degrees < l < 260-degrees), which consists of 32 identified galaxies, 12 of them with measured redshift. Using this combined sample, we examine the overdensity of Puppis and its dynamical effect on the motion of the Local Group. We find that the projected number count of galaxies brighter than 2 Jy in Puppis is about half that of Virgo. We also compare Puppis with the rest of the sky by a spherical harmonic reconstruction; out to a distance of 3000 km s-1 Puppis is second only to Virgo. We estimate that Puppis (which lies below the Supergalactic plane) may contribute at least 30 km s-1 to the motion of the Local Group perpendicular to the Supergalactic plane (V(SGZ) = -370 km s-1 in the cosmic microwave background frame). Together with the Local Void (above the Supergalactic plane) and Fornax and Eridanus (below it), this may explain the origin of the so-called 'Local Anomaly'. The analysis presented here illustrates how to combine non-uniform surveys behind the Galactic plane to produce whole-sky uniform surveys.

Power-spectrum analysis of three-dimensional redshift surveys

view Abstract Citations (798) References (40) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Power-Spectrum Analysis of Three-dimensional Redshift Surveys Feldman, Hume A. ; Kaiser, Nick ; Peacock, John A. Abstract We develop a general method for power-spectrum analysis of three- dimensional redshift surveys. We present rigorous analytical estimates for the statistical uncertainty in the power, and we are able to derive a rigorous optimal weighting scheme under the reasonable (and largely empirically verified) assumption that the long-wavelength Fourier components are Gaussian-distributed. We apply the formalism to the updated one-in-six QDOT IRAS redshift survey and compare our results with data from other probes: APM angular correlations and the CfA and the Berkeley 1.2 Jy IRAS redshift surveys. Our results bear out and further quantify the impression from, e.g., counts-in-cells analysis that there is extra power on large scales as compared to the standard cold dark matter (CDM) model with {OMEGA}h ~ 0.5. We apply likelihood analysis using the CDM spectrum with {OMEGA}h as a free parameter as a phenomenological family of models; we find the best-fitting parameters in redshift space and transform the results to real space. Finally, we calculate the distribution of the estimated long-wavelength power. This agrees remarkably well with the exponential distribution expected for Gaussian fluctuations, even out to powers of 10 times the mean. Our results thus reveal no trace of periodicity or other non-Gaussian behavior. Publication: The Astrophysical Journal Pub Date: May 1994 DOI: 10.1086/174036 arXiv: arXiv:astro-ph/9304022 Bibcode: 1994ApJ...426...23F Keywords: Astronomical Models; Cosmology; Dark Matter; Normal Density Functions; Power Spectra; Red Shift; Sky Surveys (Astronomy); Three Dimensional Models; Fourier Transformation; Infrared Astronomy Satellite; Stochastic Processes; Weighting Functions; Astrophysics; COSMOLOGY: THEORY; GALAXIES: DISTANCES AND REDSHIFTS; INFRARED: GALAXIES; METHODS: STATISTICAL; SURVEYS; Astrophysics E-Print: 31 pages, plain TeX, 9 figures available upon request. UM AC 93-5 full text sources arXiv | ADS |

Do galactic potential wells depend on their large-scale environment?

We study the dependence of the intrinsic velocities of galaxies on their large-scale environment, using a cross-correlation technique that provides an objective way of defining the local overdensity of 'trace' galaxies around 'target' galaxies. We use galaxies in optical (CfA and SSRS) and IRAS redshift surveys as tracers of the density field, and about 1000 spiral galaxies with measured circular velocities and elliptical galaxies with measured velocity dispersion as 'targets'. We find that the correlation function tends to increase with circular velocity, the trend being weak except in the case of cD-like elliptical galaxies with the highest velocity dispersions (σ ≳ 300 km s–1), where the effect is strong, possibly due to morphological segregations in clusters of galaxies. A fit to the mean overdensity δ(r < rp) of the trace galaxies (in spheres of radius rp) around target galaxies as a function of the circular velocities |$\upsilon_c$| shows a weak increase of δ with |$\upsilon_c$|⁠, with slope |$\Delta \delta(r\lesssim3.6\, h^{-1}\, \text {Mpc})/\Delta\upsilon_c\lesssim0.02$|⁠. The observed weak correlation is contrasted with the strong dependence of the correlation functions of dark haloes on their circular velocities predicted in some (e.g. high-biasing cold dark matter) models for galaxy formation. In particular, our results are inconsistent with the prediction of the 'natural' (high) biasing model at a high significance level. Comparison of our results with those of a simple biasing model suggests that either the observed circular velocities of galaxies are not simply related to the circular velocities of dark haloes, or most dark haloes were formed at high redshifts, or the galaxy distribution does not trace the matter distribution in a simple way.

The power spectra of IRAS galaxies and of Abell clusters

This work measures the power spectra of IRAS galaxies and of Abell clusters by analyzing the 2 Jy IRAS redshift survey and two redshift samples of Abell clusters. In terms of the variance Δ 2 (k), we find that the Δ 2 (k) of IRAS galaxies obeys a power law Δ 2 (k)∞k 1.3 up to the largest possible wavelength λ=2π/k∼100 h −1 Mpc which the survey is able to explore. The Δ 2 (k) of Abell clusters has the same slope as that of IRAS galaxies for λ<100 h −1 Mpc but has an amplitude about 10 times higher, which supports the linear biasing mechanism as the origin of rich clusters. At larger wavelengths, the variance of Abell clusters falls more rapidly than the power law