Going beyond galaxy ages with dense basis star formation history reconstruction

Panchromatic SED fitting allows us to better resolve degeneracies between quantities like the star formation rate and dust. This in turn allows us to more robustly extract information about the different stellar populations that comprise a galaxy’s Star Formation History (SFH). Using the Dense Basis SED fitting method (Iyer & Gawiser 2017), we reconstruct the SFHs with uncertainties for a large sample of galaxies using an atlas of SEDs corresponding to a physically motivated basis of SFHs. Using Gaussian Process Regression, we encode the parameters describing these SFHs in a functionally independent form. This give us more robust estimates for quantities like Stellar Masses and Star Formation Rates, that directly depend on the SFH. These SFHs can additionally be used to answer questions like the time at which a galaxy’s star formation peaked, and how many major episodes of star formation occurred in a galaxy’s past, allowing us to go beyond the traditionally estimated ‘Galaxy Age’, which is often poorly constrained. They also allow us to probe the high-redshift low-stellar mass regime of the SFR-M* correlation by constructing trajectories in SFR-M* space for each galaxy.

The City—A Popular Assembly

The architecture of cities provides infrastructures for thousands of people.Yet if it seems that the primary task of this architecture is to make the administration of many people, their living together, their work, their leisure, possible on a rational and dense basis, we ought not oversee that the fulfillment of these functions is not a sufficient condition of what makes a city. Important characteristics of urbanity rather enable the meeting of a multitude of people. Cities count among the conditions for social events insofar as they assemble. In my paper, I propose to analyze this architectural condition as the decisive difference between »Being With« in contrast to just »Being next to«.