Galaxy And Mass Assembly (GAMA): Blue spheroids within 87 Mpc

TL;DR

This study investigates whether nearby blue spheroid galaxies are potential progenitors of star-forming spirals or passive ellipticals by analyzing their structural and star-forming properties.

Contribution

It provides a detailed comparison of blue spheroids with other galaxy types, highlighting their unique position in galaxy evolution pathways.

Findings

Blue spheroids are structurally similar to passive red spheroids.

Their star-formation properties resemble star-forming spirals.

Some blue spheroids show signs of disk development from HI data.

Abstract

In this paper we test if nearby blue spheroid (BSphs) galaxies may become the progenitors of star-forming spiral galaxies or passively-evolving elliptical galaxies. Our sample comprises 428 galaxies of various morphologies in the redshift range 0.002<z<0.02 (8-87 Mpc) with panchromatic data from the Galaxy and Mass Assembly survey. We find that BSph galaxies are structurally (mean effective surface brightness, effective radius) very similar to their passively-evolving red counterparts. However, their star-formation and other properties such as colour, age and metallicity are more like star-forming spirals than spheroids (ellipticals and lenticulars). We show that BSph galaxies are statistically distinguishable from other spheroids as well as spirals in the multi-dimensional space mapped by luminosity-weighted age, metallicity, dust mass and specific star formation rate. We use HI data to reveal that some of the BSphs are (further) developing their disks, hence their blue colours. They may eventually become spiral galaxies --- if sufficient gas accretion occurs --- or more likely fade into low-mass red galaxies.