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

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 ${\log }_{10}(M_{\ast }/{\mathrm{M}}_{\odot })=5.8$, 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.

PASJ accepted, 7 pages, 4 figures

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