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We present a sample of local analogs for high-redshift galaxies selected inthe Sloan Digital Sky Survey (SDSS). The physical conditions of theinterstellar medium (ISM) in these local analogs resemble those inhigh-redshift galaxies. These galaxies are selected based on their positions inthe [OIII]/H$\beta$ versus [NII]/H$\alpha$ nebular emission-line diagnosticdiagram. We show that these local analogs share similar physical propertieswith high-redshift galaxies, including high specific star formation rates(sSFRs), flat UV continuums and compact galaxy sizes. In particular, theionization parameters and electron densities in these analogs are comparable tothose in $z\simeq2-3$ galaxies, but higher than those in normal SDSS galaxiesby $\simeq$0.6~dex and $\simeq$0.9~dex, respectively. The mass-metallicityrelation (MZR) in these local analogs shows $-0.2$~dex offset from that in SDSSstar-forming galaxies at the low mass end, which is consistent with the MZR ofthe $z\sim2-3$ galaxies. We compare the local analogs in this study with thosein other studies, including Lyman break analogs (LBA) and green pea (GP)galaxies. The analogs in this study share a similar star formation surfacedensity with LBAs, but the ionization parameters and electron densities in ouranalogs are higher than those in LBAs by factors of 1.5 and 3, respectively.The analogs in this study have comparable ionization parameter and electrondensity to the GP galaxies, but our method can select galaxies in a widerredshift range. We find the high sSFR and SFR surface density can increase theelectron density and ionization parameters, but still cannot fully explain thedifference in ISM condition between nearby galaxies and the localanalogs/high-redshift galaxies.

Local Analogs for High-redshift Galaxies: Resembling the Physical Conditions of the Interstellar Medium in High-redshift Galaxies