TUNA Lunch Talk:

Sara Petty

Virginia Tech

Tracing Inside-out Growth in UV-bright Nearby Early Type Galaxies

March 4

12:10PM, Room 230, NRAO, Edgemont Road


I will be presenting a recent paper, which focuses on the use of extended photometry across a broad spectrum to trace the formation history of nearby early type galaxies (ETGs). The origin of significant UV emission in quiescent ETGs is currently still debated, and strongly tied to a multi-epoch evolutionary process where much of the information is lost over many relaxation times. In order to address this topic, stellar synthesis and galaxy evolution must be disentangled, which can be more pragmatically done with well-resolved multi-wavelength images of nearby ETGs. We explore the radial distribution of FUV-NUV, NUV-r, and NUV-IR colors in a selection of nearby E/S0-type galaxies. Comparing these colors with stellar synthesis models, we find strong color gradients with the outer radii bluer than the inner half-light radii by ~1 magnitude, and account for it with an extreme horizontal branch fraction increase of 0.25. We estimated the average ages and determine that outer regions are likely to have formed ~1 Gyr after the inner regions. The results support inside-out formation: rapid star formation within the core at early epochs (>4Gyr ago) and at least one later stage starburst event coinciding with z~1.