arXiv subjects

Ian P. Dell'Antonio

Publications and source records attributed to Ian P. Dell'Antonio.

24 records · Page 2Linked to original sources

arXiv2007

The Mass Of The Coma Cluster From Weak Lensing In The Sloan Digital Sky Survey

We present a weak lensing analysis of the Coma Cluster using the Sloan Digital Sky Survey (SDSS) Data Release Five. Complete imaging of a ~ 200 square degree region is used to measure the tangential shear of this cluster. The shear is fit to an NFW model and we find a virial radius of r_{200}=1.99_{-0.22}^{+0.21}h^{-1}Mpc which corresponds to a virial mass of M_{200}=1.88_{-0.56}^{+0.65}\times10^{15}h^{-1}M_{\odot}. We additionally compare our weak lensing measurement to the virial mass derived using dynamical techniques, and find they are in agreement. This is the lowest redshift, largest angle weak lensing measurement of an individual cluster to date.

astro-ph↗

arXiv2007

$μ$--PhotoZ: Photometric Redshifts by Inverting the Tolman Surface Brightness Test

Surface brightness is a fundamental observational parameter of galaxies. We show, for the first time in detail, how it can be used to obtain photometric redshifts for galaxies, the $μ$-PhotoZ method. We demonstrate that the Tolman surface brightness relation, $μ\propto (1+z)^{-4}$, is a powerful tool for determining galaxy redshifts from photometric data. We develop a model using $μ$ and a color percentile (ranking) measure to demonstrate the $μ$-PhotoZ method. We apply our method to a set of galaxies from the SHELS survey, and demonstrate that the photometric redshift accuracy achieved using the surface brightness method alone is comparable with the best color-based methods. We show that the $μ$-PhotoZ method is very effective in determining the redshift for red galaxies using only two photometric bands. We discuss the properties of the small, skewed, non-gaussian component of the error distribution. We calibrate $μ_r, (r-i)$ from the SDSS to redshift, and tabulate the result, providing a simple, but accurate look up table to estimate the redshift of distant red galaxies.

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arXiv2005

SHELS: The Hectospec Lensing Survey

The Smithsonian Hectospec Lensing Survey (SHELS) combines a large deep complete redshift survey with a weak lensing map from the Deep Lens Survey (Wittman et al. 2002; 2005). We use maps of the velocity dispersion based on systems identified in the redshift survey to compare the three-dimensional matter distribution with the two-dimensional projection mapped by weak lensing. We demonstrate directly that the lensing map images the three-dimensional matter distribution obtained from the kinematic data.

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arXiv1998

Detailed Mass Map of CL0024+1654 from Strong Lensing

We construct a high resolution mass map of the z=0.39 cluster 0024+1654, based on parametric inversion of the associated gravitational lens. The lens creates eight well-resolved sub-images of a background galaxy, seen in deep imaging with HST. Excluding mass concentrations centered on visible galaxies, more than 98% of the remaining mass is represented by a smooth concentration of dark matter centered near the brightest cluster galaxies, with a 35 h^{-1} kpc soft core. The asymmetry in the mass distribution is <3% inside 107 ~h^{-1} kpc radius. The dark matter distribution we observe in CL0024 is far more smooth, symmetric, and nonsingular than in typical simulated clusters in either Omega=1 or Omega=0.3 CDM cosmologies. Integrated to 107 h^{-1} kpc radius, the rest-frame mass to light ratio is M/L_V = 276\pm 40 h (M/L_V)_solar.

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arXiv1996

Galaxy Dark Matter: Galaxy-Galaxy Lensing in the Hubble Deep Field

In this Letter we present calibrated observations of the average mass of galaxies with 22< I < 25 in the Hubble Deep Field. We measure the mean mass profile using the statistical gravitational lens distortion of faint blue background galaxies, based on 2221 foreground-background pairs. The observed weak lensing distortion is calibrated via full 3-D simulations and other HST data on a foreground cluster of known mass. Inside a projected radius of 5 arcsec we find a 3σdetection of shear. Fitting to an isothermal mass distribution, we find a shear of 0.066^{+0.018}_{-0.019} at a radius of 2\arcsec\ (\sim 8 ~ h^{-1} kpc). The (1σ) limits on the parameters for the truncated isothermal model are σ_v =185^{+30}_{-35} km s^{-1}, r_{outer} \ge 15 ~ h^{-1} kpc, and r_{core}= 0.6^{+1.3}_{-0.6} ~ h^{-1} kpc. This corresponds to an average galaxy mass interior to 20 h^{-1} kpc of 5.9^{+2.5}_{-2.7}\times 10^{11} h^{-1} M_\odot. Inside 10 h^{-1} kpc, we find an average rest-frame V band mass-to-light ratio of 11.4^{+6.0}_{-6.7} h (M/L_V)_\odot.

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arXiv1993

The Time Development of a Resonance Line in the Expanding Universe

The time-dependent spectral profile of a resonance line in a homogeneous expanding medium is studied by numerically solving an improved Fokker-Planck diffusion equation. The solutions are used to determine the time required to reach a quasi-static solution near the line center. A simple scaling law for this relaxation time is derived and is fitted to the numerical results. The results are applied to the case of Lyman alpha scattering during primordial recombination of hydrogen. For a wide range of cosmological models it is found that the relaxation times are smaller than the recombination timescale, although not by a very large factor. Thus the standard assumption of a quasi-static solution in cosmological recombination calculations is reasonably valid, and should not cause substantial errors in the solutions.

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