Engineering topics

Da Costa, L. Nicolaci

Publications and source records attributed to Da Costa, L. Nicolaci.

4 records

NASA NTRS1994

The power spectrum of galaxies in the nearby universe

We compute the power spectrum of galaxy density fluctuations in a recently completed Southern Sky Redshift Survey of optically selected galaxies (SSRS2). The amplitude and shape of the SSRS2 power spectrum are consistent with results of the Center for Astrophysics redshift survey of the northern hemisphere (CfA2), including the abrupt change of slope on a scale of 30-50/h Mpc; these results are reproducible for independent volumes of space, and variations are consistent with the errors estimated from mock surveys. Taken together, the SSRS2 and the CfA2 form a complete sample of 14,383 galaxies which covers one-third of the sky. The power spectrum of this larger sample continues to rise on scales up to approximately 200/h Mpc, with weak evidence for flattening on the largest scales. The SSRS2 + CfA2 power spectrum and the power spectrum constraints implied by COBE are well matched by an Omega(h) is approximately 0.2, Omega + lambda(sub 0) = 1 cold dark matter model with minimal biasing of optically selected galaxies.

Da Costa, L. Nicolaci↗

NASA NTRS1994

A complete southern sky redshift survey

We discuss a magnitude-limited redshift survey covering a region around the south Galactic pole (SSRS2). The survey includes 3592 galaxies and covers a region of 1.13 sr to a limiting m(sub B(0)) = 15.5, directly comparable to CfA2. Together, CfA2 and SSR2 cover more than a third of the sky. The northern and southern surveys are remarkably similar. Both contain voids with diameters as large as 5000 km/s. The southern survey contains the Southern Wall, similar to the northern Great Wall. The distributions of velocity dispersions for systems extracted from the SSRS2 and CfA2 surveys are also remarkably similar. For the SSRS2, an inhomogeneity-independent technique yields Schechter luminosity function parameters M(sup *) = -19.50 and alpha = -1.20 (H(sub O) = 100 h km/s/Mpc, h = 1 unless otherwise specified). The steep faint-end slope is probably attributable to bluer galaxies. By examining the normalized density fluctuations in the SSRS2 and CfA2 surveys, we suggest that the combined sample is not yet large enough to be 'fair.' There are large fluctuations in shells at 10,000 km/s.

Da Costa, L. Nicolaci↗

NASA NTRS1990

Distribution of galaxies in the Southern Galactic Cap

Observations in the southern galactic hemisphere in the declination range between -17.5 and 2.5 degrees are combined with other available observation. The data set is used to study the spatial distribution of galaxies of a contiguous area of 3.13 sr of the Southern Galactic Cap. An approximately homogeneous magnitude-limited sample of galaxies in the Southern Galactic Cap is constructed from different catalogs. The resulting large scale structure is similar to that of previous surveys in which bright galaxies are distributed on surfaces which intersect at sharp corners and nearly surround voids that are almost empty of galaxies.

Pellegrini, P. S.↗

NASA NTRS1988

On the universality of the two-point galaxy correlation function

The behavior of the two-point galaxy correlation function in volume-limited subsamples of three complete redshift surveys is investigated. The correlation length is shown to scale approximately as the square root of the distance limit in both the CfA and Southern Sky catalogs, but to be independent of the distance limit in the IRAS sample. This effect is found to be due to factors such as the large positive density fluctuations in the foreground of the optically selected catalogs biasing the correlation length estimate downward, and the brightest galaxies appearing to be more strongly clustered than the mean.

Davis, Marc↗