Satellite Kinematics III: Halo Masses of Central Galaxies in SDSS (1003.3203v1)

Abstract: We use the kinematics of satellite galaxies that orbit around the central galaxy in a dark matter halo to infer the scaling relations between halo mass and central galaxy properties. Using galaxies from the Sloan Digital Sky Survey, we investigate the halo mass-luminosity relation (MLR) and the halo mass-stellar mass relation (MSR) of central galaxies. In particular, we focus on the dependence of these scaling relations on the colour of the central galaxy. We find that red central galaxies on average occupy more massive haloes than blue central galaxies of the same luminosity. However, at fixed stellar mass there is no appreciable difference in the average halo mass of red and blue centrals, especially for M* $\lsim$ 10^{10.5} h^{-2} Msun. This indicates that stellar mass is a better indicator of halo mass than luminosity. Nevertheless, we find that the scatter in halo masses at fixed stellar mass is non-negligible for both red and blue centrals. It increases as a function of stellar mass for red centrals but shows a fairly constant behaviour for blue centrals. We compare the scaling relations obtained in this paper with results from other independent studies of satellite kinematics, with results from a SDSS galaxy group catalog, from galaxy-galaxy weak lensing measurements, and from subhalo abundance matching studies. Overall, these different techniques yield MLRs and MSRs in fairly good agreement with each other (typically within a factor of two), indicating that we are converging on an accurate and reliable description of the galaxy-dark matter connection. We briefly discuss some of the remaining discrepancies among the various methods.

• The paper finds that red central galaxies occupy more massive halos than blue ones at fixed luminosity, establishing a key color dependency in halo mass relations.
• It employs satellite- and host-weighted velocity dispersions on a volume-limited SDSS sample to robustly derive halo mass-luminosity and halo mass-stellar mass scaling relations.
• The study highlights significant scatter in halo mass at fixed stellar mass, underscoring the stochastic nature of galaxy formation processes.

Satellite Kinematics and Halo Masses of Central Galaxies

The paper "Satellite Kinematics III: Halo Masses of Central Galaxies in SDSS" by More et al. presents a comprehensive investigation into the relationship between dark matter halo masses and the properties of central galaxies. Using data from the Sloan Digital Sky Survey (SDSS), the authors employ satellite galaxy kinematics to infer scaling relations, particularly exploring the halo mass-luminosity relation (MLR) and the halo mass-stellar mass relation (MSR).

Methodology and Data

The authors analyze the kinematics of satellite galaxies orbiting central galaxies within dark matter halos to derive the scaling relations between halo mass and galaxy properties. The central galaxy's properties of interest include luminosity and stellar mass, adjusted to consider the color of the galaxies. The paper uses a volume-limited sample from SDSS, focusing on identifying centrals and satellites via an iterative selection method which scales with the galaxy's property of interest, such as luminosity or stellar mass.

The satellite-weighted and host-weighted velocity dispersions are pivotal to this analysis. This approach is instrumental in addressing previous studies' issues by allowing for determining both average halo masses and their scatter. The authors also utilize statistical models to describe satellite kinematics and infer the properties of the halos.

Key Findings

1. Color Dependency: The paper finds that red central galaxies generally occupy more massive halos than their blue counterparts when observed at fixed luminosity. This highlights a potential dependency of halo properties on the color of the central galaxy, suggesting that red centrals reside in denser dark matter halos.
2. Stellar Mass versus Luminosity: When central galaxies are stacked by stellar mass, the distinction between red and blue galaxies in terms of their average halo masses is less pronounced, specifically at lower mass scales (M* around 10^10.5). This suggests that stellar mass is a more reliable predictor of halo mass compared to luminosity.
3. Scatter in Halo Mass: A notable conclusion is that the scatter in halo mass at fixed stellar mass is significant, with variations in scatter behavior for red and blue centrals—highlighting the stochastic nature of galaxy formation and the complexity in linking galaxy and halo properties.

Implications

The research demonstrates the capability of satellite kinematics in refining the understanding of the galaxy-dark matter halo connection. Despite achieving convergence among different methodologies, slight variances remain across studies, elucidating potential avenues for refinement in future astronomical surveys. The findings emphasize the need for considering galaxy color and stellar mass more critically in modeling galaxy-halo relationships, thus improving the theoretical models of galaxy formation.

Future developments could target further refinement of satellite galaxy kinematics modeling, potentially involving enhanced simulations that account for more diverse galaxy formation histories and environmental influences. This could improve the accuracy of predictions related to galaxy evolution and the dynamics of their respective dark matter halos.

Overall, More et al.'s work stands as a crucial contribution to the field, providing rigorous empirical constraints on the distribution of dark matter around galaxies, offering new insights, especially concerning the role of galaxy color, and advocating for stellar mass as a key determinant of halo mass. This understanding is essential for future cosmological studies and for enhancing the predictive power of galaxy formation models.