Subaru/FOCAS IFU revealed the metallicity gradient of a local extremely metal-poor galaxy

TL;DR

This study uses Subaru/FOCAS IFU to measure the metallicity gradient in a local extremely metal-poor galaxy, revealing detailed chemical distribution and demonstrating the effectiveness of 3D spectroscopy in such faint, low-mass systems.

Contribution

First measurement of metallicity gradient in an extremely metal-poor galaxy using IFU spectroscopy, showing the potential of 8m-class telescopes for studying primordial galaxy analogs.

Findings

Metallicity gradient of -0.36 dex/kpc measured in the galaxy.

Demonstrated the capability of 8m-class telescopes for detailed chemical mapping.

Provided insights into baryon cycle in primitive galaxy environments.

Abstract

We present the first measurement of the metallicity gradient in extremely metal-poor galaxies (EMPGs). With Subaru/Faint Object Camera And Spectrograph (FOCAS) Integral Field Unit (IFU), we have observed a nearby, low-mass EMPG, HSC J1631+4426, whose oxygen abundance and stellar mass are known to be 12+log(O/H) $=6.9$ and $\log_{10}(M_*/{\rm M}_\odot)=5.8$, respectively. The measured metallicity gradient is $-0.36 \pm 0.04$ dex kpc$^{-1}$ corresponding to $-0.049 \pm 0.006$ dex R$_\mathrm{e}^{-1}$ for the continuum effective radius of $R_\mathrm{e} = 0.14$ kpc. Our observation has successfully demonstrated that three-dimensional spectroscopy with 8m-class telescopes is powerful enough to reveal the metallicity distribution in local EMPGs, providing precious information of the baryon cycle in local analogs of primordial galaxies in the early Universe.