O/H-N/O: the curious case of NGC 4670<SUP>★</SUP>

DOI: 
10.1093/mnras/sty402
Publication date: 
01/02/2018
Main author: 
Kumari, Nimisha
IAA authors: 
Pérez-Montero, Enrique
Authors: 
Kumari, Nimisha;James, Bethan L.;Irwin, Mike J.;Amorín, Ricardo;Pérez-Montero, Enrique
Journal: 
Monthly Notices of the Royal Astronomical Society
Refereed: 
Yes
Publication type: 
Article
Pages: 
3793-3815
Abstract: 
We use integral field spectroscopic (IFS) observations from Gemini North Multi-Object Spectrograph (GMOS-N) of a group of four H II regions and the surrounding gas in the central region of the blue compact dwarf (BCD) galaxy NGC 4670. At spatial scales of ̃ 9 pc, we map the spatial distribution of a variety of physical properties of the ionised gas: internal dust attenuation, kinematics, stellar age, star-formation rate, emission line ratios and chemical abundances. The region of study is found to be photoionised. Using the robust direct T<SUB>e</SUB>-method, we estimate metallicity, nitrogen-to-oxygen ratio and helium abundance of the four H II regions. The same parameters are also mapped for the entire region using the HII-CHI-mistry code. We find that log(N/O) is increased in the region where the Wolf-Rayet bump is detected.The region coincides with the continuum region, around which we detect a slight increase in He abundance. We estimate the number of WC4, WN2-4 and WN7-9 stars from the integrated spectrum of WR bump region. We study the relation between log(N/O) and 12 + log(O/H) using the spatially-resolved data of the FOV as well as the integrated data of the H II regions from ten BCDs. We find an unexpected negative trend between N/O and metallicity. Several scenarios are explored to explain this trend, including nitrogen enrichment, and variations in star formation efficiency via chemical evolution models.
Database: 
ADS
SCOPUS
URL: 
https://ui.adsabs.harvard.edu/#abs/2018MNRAS.476.3793K/abstract
ADS Bibcode: 
2018MNRAS.476.3793K
Keywords: 
galaxies: individual: NGC 4670;galaxies: dwarfs;galaxies: abundances;ISM: H II regions;Astrophysics - Astrophysics of Galaxies