Evolution of the Galaxy - Dark Matter Connection and the Assembly of Galaxies in Dark Matter Halos (1110.1420v3)

Abstract: We present a new model to describe the galaxy-dark matter connection across cosmic time, which unlike the popular subhalo abundance matching technique is self-consistent in that it takes account of the facts that (i) subhalos are accreted at different times, and (ii) the properties of satellite galaxies may evolve after accretion. Using observations of galaxy stellar mass functions out to $z \sim 4$, the conditional stellar mass function at $z\sim 0.1$ obtained from SDSS galaxy group catalogues, and the two-point correlation function (2PCF) of galaxies at $z \sim 0.1$ as function of stellar mass, we constrain the relation between galaxies and dark matter halos over the entire cosmic history from $z \sim 4$ to the present. This relation is then used to predict the median assembly histories of different stellar mass components within dark matter halos (central galaxies, satellite galaxies, and halo stars). We also make predictions for the 2PCFs of high-$z$ galaxies as function of stellar mass. Our main findings are the following: (i) Our model reasonably fits all data within the observational uncertainties, indicating that the $\Lambda$CDM concordance cosmology is consistent with a wide variety of data regarding the galaxy population across cosmic time. (ii) ... [abridged]

Analyzing the Galaxy and Dark Matter Connection Across Cosmic Time

This paper by Yang et al. presents a novel approach to understanding the relationship between galaxies and their dark matter halos throughout cosmic history. It enhances the traditional methods like subhalo abundance matching by incorporating the effects of subhalo accretion times and the post-accretion evolution of satellite galaxies. Using observational data ranging from the stellar mass functions of galaxies at various redshifts to the conditional stellar mass function (CSMF) and two-point correlation functions (2PCFs) from the Sloan Digital Sky Survey (SDSS), the paper offers a comprehensive model capturing the galaxy-dark matter connection from redshift $z \sim 4$ to the present.

Main Contributions

1. Self-consistent Model: The paper introduces a model that dynamically tracks the evolution of satellite galaxies within their host halos. It highlights that satellite properties depend on both the mass at accretion and subsequent evolution, thus aligning more closely with the physical processes involved in galaxy formation.
2. Evolution of Central and Satellite Galaxies: Central galaxies steadily increase in mass with their halo mass, showing the most efficient star formation at a halo mass of $M \sim 10^{11.8} M_{\odot}$. The stellar mass of central galaxies in these halos exhibits a maximum of about 0.03 relative to their halo mass, a factor lower than the universal baryon fraction, demonstrating the inefficiencies in star formation.
3. Disruption Time Scale: The disruption scale for satellite galaxies suggests a close alignment with the dynamical friction time scales derived from $N$-body simulations. This consistency highlights a possible widespread disruption mechanism relative to their orbital decay.
4. Assembly Histories and Redshift Dependence: The paper produces detailed assembly histories for central and satellite components, indicating that central galaxy growth is predominantly insular until reaching a halo mass of about $10^{12} M_{\odot}$. Growth then primarily proceeds through processes other than just accretion, possibly star formation fueled internally.
5. High-Redshift Predictions: The paper extends the model to predict the 2PCFs at higher redshifts. It finds that clustering properties evolve significantly, particularly on small scales, potentially offering new insights into the processes shaping early galaxy formation.

Implications

The findings present a shift from classical models of galaxy formation by presenting a more integrated account of galaxy evolution, incorporating not just halo growth but also subhalo interactions post-accretion. This approach not only resolves some of the discrepancies in matching satellite distributions but also accounts for the shifts in star formation efficiency over cosmic time. Moreover, the paper demonstrates the utility of high-precision datasets, particularly the SDSS, in constraining cosmological models and galaxy evolution theories.

Future Directions

Future models could integrate constraints from additional high-redshift datasets and combine with environmental effects that might alter the satellite disruption rates differently in varying halo environments. Additionally, improvements in dynamical models could offer richer insights into the mechanics of star formation quenching as halo masses cross specific thresholds. Such developments might allow researchers to better delineate the relative roles of AGN feedback, hot gas formation, and other halo properties in driving galaxy evolution.