A Headless Tadpole Galaxy: The High Gas-phase Metallicity of the Ultra-diffuse Galaxy UGC 2162

DOI: 
10.3847/1538-4357/aae9f3
Publication date: 
01/12/2018
Main author: 
Sánchez Almeida, J.
IAA authors: 
Pérez-Montero, E.
Authors: 
Sánchez Almeida, J.;Olmo-García, A.;Elmegreen, B. G.;Elmegreen, D. M.;Filho, M.;Muñoz-Tuñón, C.;Pérez-Montero, E.;Román, J.
Journal: 
The Astrophysical Journal
Refereed: 
Yes
Publication type: 
Article
Volume: 
869
Pages: 
40
Abstract: 
The cosmological numerical simulations tell us that accretion of external metal-poor gas drives star formation (SF) in galaxy disks. One the best pieces of observational evidence supporting this prediction is the existence of low-metallicity star-forming regions in relatively high-metallicity host galaxies. The SF is thought to be fed by metal-poor gas recently accreted. Since the gas accretion is stochastic, there should be galaxies with all the properties of a host but without the low-metallicity starburst. These galaxies have not been identified yet. The exception may be UGC 2162, a nearby ultra-diffuse galaxy (UDG) that combines low surface brightness and relatively high metallicity. We confirm the high metallicity of UGC 2162 (12+{log}({{O}}/{{H}})={8.52}<SUB>-0.24</SUB><SUP>+0.27</SUP>) using spectra taken with the 10 m GTC telescope. UGC 2162 has the stellar mass, metallicity, and star formation rate surface density expected for a host galaxy in between outbursts. This fact suggests a physical connection between some UDGs and metal-poor galaxies, which may be the same type of object in a different phase of the SF cycle. UGC 2162 is a high-metallicity outlier of the mass─metallicity relation, a property shared by the few UDGs with known gas-phase metallicity.
Database: 
ADS
SCOPUS
URL: 
https://ui.adsabs.harvard.edu/#abs/2018ApJ...869...40S/abstract
ADS Bibcode: 
2018ApJ...869...40S
Keywords: 
galaxies: abundances;galaxies: evolution;galaxies: formation;galaxies: fundamental parameters;galaxies: star formation;intergalactic medium;Astrophysics - Astrophysics of Galaxies