New constraints on the evolution of the stellar-to-dark matter connection: a combined analysis of galaxy-galaxy lensing, clustering, and stellar mass functions from z=0.2 to z=1 (1104.0928v1)

Abstract: Using data from the COSMOS survey, we perform the first joint analysis of galaxy-galaxy weak lensing, galaxy spatial clustering, and galaxy number densities. Carefully accounting for sample variance and for scatter between stellar and halo mass, we model all three observables simultaneously using a novel and self-consistent theoretical framework. Our results provide strong constraints on the shape and redshift evolution of the stellar-to-halo mass relation (SHMR) from z=0.2 to z=1. At low stellar mass, we find that halo mass scales as Mh M*^0.46 and that this scaling does not evolve significantly with redshift to z=1. We show that the dark-to-stellar ratio, Mh/M*, varies from low to high masses, reaching a minimum of Mh/M*~27 at M*=4.5x10^10 Msun and Mh=1.2x10^12 Msun. This minimum is important for models of galaxy formation because it marks the mass at which the accumulated stellar growth of the central galaxy has been the most efficient. We describe the SHMR at this minimum in terms of the "pivot stellar mass", M*piv, the "pivot halo mass", Mhpiv, and the "pivot ratio", (Mh/M*)piv. Thanks to a homogeneous analysis of a single data set, we report the first detection of mass downsizing trends for both Mhpiv and M*piv. The pivot stellar mass decreases from M*piv=5.75+-0.13x10^10 Msun at z=0.88 to M*piv=3.55+-0.17x10^10 Msun at z=0.37. Intriguingly, however, the corresponding evolution of Mhpiv leaves the pivot ratio constant with redshift at (Mh/M*)piv~27. We use simple arguments to show how this result raises the possibility that star formation quenching may ultimately depend on Mh/M* and not simply Mh, as is commonly assumed. We show that simple models with such a dependence naturally lead to downsizing in the sites of star formation. Finally, we discuss the implications of our results in the context of popular quenching models, including disk instabilities and AGN feedback.

• The paper employs a joint analysis of lensing, clustering, and mass functions to tightly constrain the stellar-to-halo mass relation over a redshift range of 0.2 to 1.
• It reveals a pivot in the dark-to-stellar mass ratio, with the most efficient stellar accumulation at M* ≈ 4.5×10^10 M₀ and Mₕ ≈ 1.2×10^12 M₀.
• The findings imply that star formation quenching and mass downsizing are closely linked to evolving SHMR characteristics and the dark-to-stellar mass ratio.

Overview of "New Constraints on the Evolution of the Stellar-to-Dark Matter Connection"

The paper by Leauthaud et al. presents a comprehensive paper that explores the link between stellar mass and dark matter halo mass in galaxies from a redshift of 0.2 to 1.0. Using the COSMOS survey data, the paper incorporates galaxy-galaxy weak lensing, spatial clustering, and stellar mass functions to establish a self-consistent framework constraining the stellar-to-halo mass relation (SHMR).

The research deploys a novel and holistic approach, modeling these three observables simultaneously to derive strong constraints on the SHMR's shape and its evolution over time. The analysis reveals that the relationship between halo mass and stellar mass changes with redshift, elucidating critical insights into the galaxy formation and evolution processes.

Key Findings

1. Stellar-to-Halo Mass Relation (SHMR) Characteristics:
   • At low stellar masses, the SHMR follows a power-law relationship with halo mass $M_h \propto M_*^{0.46}$.
   • The SHMR slope steepens considerably at high stellar masses ($M_* > 5\times 10^{10}\, M_{\odot}$), rendering stellar mass a poor tracer of halo mass beyond this range.
2. Dark-to-Stellar Mass Ratio:
   • The ratio $M_h/M_*$ varies significantly across the mass spectrum, reaching a minimum of $\sim 27$ at a stellar mass of $4.5\times 10^{10}\, M_{\odot}$ and a halo mass of $1.2\times 10^{12}\, M_{\odot}$.
   • This ratio minimum is particularly significant, marking the mass scale where stellar accumulation in central galaxies is most efficient.
3. Redshift Evolution and "Mass Downsizing":
   • A notable decrease in the pivot stellar and halo masses from higher to lower redshifts was detected, indicating a mass downsizing trend in galaxy formation.
   • The pivot stellar mass progresses from $5.75\times 10^{10}\, M_{\odot}$ at $z=0.88$ to $3.55\times 10^{10}\, M_{\odot}$ at $z=0.37$.
4. Implications for Star Formation Quenching:
   • The findings suggest that star formation quenching might be intricately tied not just to halo mass but the dark-to-stellar mass ratio $M_h/M_*$.
   • The paper posits that such dependencies could naturally engender the observed downsizing phenomenon, impacting models reliant on AGN feedback and disk instabilities for explaining galaxy evolution.

Theoretical and Practical Implications

This research holds profound implications for both theoretical modeling of galaxy formation and observational strategies in cosmology. By refining our understanding of the SHMR's evolution, the paper advances theories regarding the physical processes that regulate star formation across cosmic time. Moreover, insights into the dynamic interplay between baryonic and dark matter components can inform the development of more accurate semi-analytical models and hydrodynamic simulations.

The consistency of the pivot ratio observed highlights potential new areas for investigation, particularly regarding its implications for feedback mechanisms and galaxy quenching processes. Future research efforts could focus on validating these findings using larger, diverse datasets and exploring the applicability of this framework at higher or lower redshifts across different cosmological environments.

In summary, the paper by Leauthaud et al. effectively utilizes COSMOS survey data to deliver new insights into the intricate stellar-to-dark matter connections in galaxies, providing a pivotal reference point for ongoing studies in galactic and extragalactic astrophysics.