arXiv subjects

Nikhil Padmanabhan

Publications and source records attributed to Nikhil Padmanabhan.

111 records · Page 7Linked to original sources

arXiv2001

The power spectrum of the CfA/SSRS UZC galaxy redshift survey

The combined CfA2/SSRS redshift catalog has recently been improved and made public. We compute the redshift-space power spectrum of this catalog using the regions at -2.5 < delta < 50 north (8h < alpha < 17h) and south (20h < alpha < 3h, b < -13) of the Galactic plane, where it is 98% complete down to Zwicky magnitude 15.5 and contains 13,681 galaxies. Our analysis uses Heavens-Taylor mode expansion, Karhunen-Loeve data compression and the Fisher matrix technique to compute quadratic band power estimates. This allows an exact calculation of window functions, including the integral constraint, in addition to the production of a power spectrum with uncorrelated error bars. Our results with this larger data set agree well with previous studies. We analyze 101Mpc/h and 130Mpc/h volume-limited subsets in addition to the full magnitude-limited sample, and our results are well fit by, e.g., Lambda-CDM models with bias b=1.2, 1.4 and 1.4, respectively. We estimate the effect of extinction using the Schlegel, Finkbeiner & Davis dust map. Our results are exclusively for the redshift space galaxy power spectrum, so they can only be compared with theoretical predictions if appropriate corrections are made for biasing and redshift space distortions.

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arXiv2000

Weak Lensing Constraints on Cluster Structural Parameters

We study the reliability of dark matter (DM) profile determinations for rich clusters of galaxies based on weak gravitational lensing measurements. We consider three functional forms for the mass distribution: a softened isothermal sphere (SIS), the Navarro, Frenk, & White model (NFW) and the Klypin, Kravstov, Bullock, & Primack model (KKBP). A maximum likelihood parametric method is developed and applied to simulated images of background galaxies (z=2.0) lensed by clusters at z=0.2, 0.5, and 0.8. The images have field size (~10 arcmin) and angular resolution (~0.5 arcsec) characteristic of the new generation of 8-10 meter-class ground-based telescopes. The method recovers the correct virial mass of the DM halo, M_{200}, to within ~10% at all redshifts. The recovered values of δ_c and r_s are only accurate to ~25%; however, their correlated errors are such that greater accuracy is obtained for the mass. Clusters with an SIS density profile are recognized by the method, while NFW and KKBP clusters are recognized as not being SIS. The method does not discriminate between NFW and KKBP profiles for clusters of a given mass, because they are too similar in their outer regions. Strongly lensed arcs near the cluster centers would be needed to distinguish NFW from KKBP.

astro-ph↗

arXiv2000

Linear Redshift Distortions and Power in the PSCz Survey

We present a state-of-the-art linear redshift distortion analysis of the recently published IRAS Point Source Catalog Redshift Survey (PSCz). The procedure involves linear compression into 4096 Karhunen-Loeve modes culled from a potential pool of about 3 x 10^5 modes, followed by quadratic compression into three separate power spectra, the galaxy-galaxy, galaxy-velocity, and velocity-velocity power spectra. Least squares fitting to the decorrelated power spectra yields a linear redshift distortion parameter beta = Omega_m^0.6/b = 0.41(+0.13,-0.12).

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