Does stellar mass assembly history vary with environment?

TL;DR

This study investigates how stellar mass assembly history varies with environment using SDSS data and compares it with semi-analytic models, finding that stellar age is largely environment-independent but correlates with dark matter halo mass.

Contribution

It provides an empirical analysis of stellar mass weighted age dependence on environment and halo mass, and compares these findings with semi-analytic models and dark matter accretion histories.

Findings

Stellar MWA shows large scatter consistent with models.

Stellar MWA is largely independent of local galaxy density.

Average stellar MWA increases with dark matter halo mass.

Abstract

Using the publicly available VESPA database of SDSS Data Release 7 spectra, we calculate the stellar Mass Weighted Age (hereafter MWA) as a function of local galaxy density and dark matter halo mass. We compare our results with semi-analytic models from the public Millennium Simulation. We find that the stellar MWA has a large scatter which is inherent in the data and consistent with that seen in semi-analytic models. The stellar MWA is consistent with being independent (to first order) with local galaxy density, which is also seen in semi-analytic models. As a function of increasing dark matter halo mass (using the SDSS New York Value Added Group catalogues), we find that the average stellar MWA for member galaxies increases, which is again found in semi-analytic models. Furthermore we use public dark matter Mass Accretion History (MAH) code calibrated on simulations, to calculate the dark matter Mass Weighted Age as a function of dark matter halo mass. In agreement with earlier analyses, we find that the stellar MWA and the dark matter MWA are anti correlated for large mass halos, i.e, dark matter accretion does not seem to be the primary factor in determining when stellar mass was compiled. This effect can be described by down-sizing.