Galaxy-Galaxy Weak Lensing Measurements from SDSS: I. Image Processing and Lensing signals

TL;DR

This paper introduces an improved image processing pipeline for SDSS DR7 data to measure galaxy-galaxy lensing signals, confirming that more luminous or massive galaxies exhibit stronger lensing effects and exploring differences among galaxy types.

Contribution

We developed a new pipeline to correct PSF systematics in SDSS DR7 data, enabling more accurate galaxy-galaxy lensing measurements and analysis of galaxy-halo relations.

Findings

Lensing signals are stronger for more luminous/massive galaxies.

Red/quenched galaxies show stronger lensing signals than blue/star-forming ones.

Results are consistent with previous SDSS DR4 studies, with higher signal-to-noise ratio.

Abstract

As the first paper in a series on the study of the galaxy-galaxy lensing from Sloan Digital Sky Survey Data Release 7 (SDSS DR7), we present our image processing pipeline that corrects the systematics primarily introduced by the Point Spread Function (PSF). Using this pipeline, we processed SDSS DR7 imaging data in $r$ band and generated a background galaxy catalog containing the shape information of each galaxy. Based on our own shape measurements of the galaxy images from SDSS DR7, we extract the galaxy-galaxy (GG) lensing signals around foreground spectroscopic galaxies binned in different luminosity and stellar mass. The overall signals are in good agreement with those obtained by \citet{Mandelbaum2005, Mandelbaum2006} from the SDSS DR4. The results in this paper with higher signal to noise ratio is due to the larger survey area than SDSS DR4, confirm that more luminous/massive galaxies bear stronger GG lensing signal. We also divide the foreground galaxies into red/blue and star forming/quenched subsamples and measured their GG lensing signals, respectively. We find that, at a specific stellar mass/luminosity, the red/quenched galaxies have relatively stronger GG lensing signals than their counterparts especially at large radii. These GG lensing signals can be used to probe the galaxy-halo mass relations and their environmental dependences in the halo occupation or conditional luminosity function framework.