Planck Intermediate Results. XI: The gas content of dark matter halos: the Sunyaev-Zeldovich-stellar mass relation for locally brightest galaxies

TL;DR

This study establishes a detailed relation between Sunyaev-Zeldovich signals and stellar mass for a large sample of galaxies, revealing insights into baryon content and gas distribution in dark matter halos across a wide mass range.

Contribution

It provides the first measurement of the SZ-stellar mass relation for low-mass halos down to 4×10^{12} solar masses, extending previous studies to smaller systems.

Findings

SZ signal correlates with stellar mass over a wide halo mass range

Approximately 25% of baryons are observed as hot halo gas in low-mass halos

The SZ signal in high-mass halos is 20% lower than X-ray observations suggest

Abstract

We present the scaling relation between Sunyaev-Zeldovich (SZ) signal and stellar mass for almost 260,000 locally brightest galaxies (LBGs) selected from the Sloan Digital Sky Survey (SDSS). These are predominantly the central galaxies of their dark matter halos. We calibrate the stellar-to-halo mass conversion using realistic mock catalogues based on the Millennium Simulation. Applying a multi-frequency matched filter to the Planck data for each LBG, and averaging the results in bins of stellar mass, we measure the mean SZ signal down to $M_\ast\sim 2\times 10^{11} \Msolar$, with a clear indication of signal at even lower stellar mass. We derive the scaling relation between SZ signal and halo mass by assigning halo properties from our mock catalogues to the real LBGs and simulating the Planck observation process. This relation shows no evidence for deviation from a power law over a halo mass range extending from rich clusters down to $M_{500}\sim 2\times 10^{13} \Msolar$, and there is a clear indication of signal down to $M_{500}\sim 4\times 10^{12} \Msolar$. Planck's SZ detections in such low-mass halos imply that about a quarter of all baryons have now been seen in the form of hot halo gas, and that this gas must be less concentrated than the dark matter in such halos in order to remain consistent with X-ray observations. At the high-mass end, the measured SZ signal is 20% lower than found from observations of X-ray clusters, a difference consistent with Malmquist bias effects in the X-ray sample.