Deep Submillimeter and Radio Observations in the SSA22 Field. IV. Spectral Energy Distributions, Star Formation Histories, and the Infrared-Radio Correlation of the 850 $\mu$m-selected SMGs

TL;DR

This study investigates the properties, evolution, and contributions of 850 μm-selected submillimeter galaxies in SSA22, revealing their star formation histories, mass assembly, and the infrared-radio correlation across cosmic time.

Contribution

It provides a comprehensive analysis of the spectral energy distributions, star formation histories, and IR-radio correlation of SMGs, highlighting their role in cosmic star formation and galaxy evolution.

Findings

Most SMGs began forming ~1.68 Gyr after the Big Bang.

SMGs transition from active to quiescent within ~0.2 Gyr.

SMGs contribute significantly to cosmic star formation at z=2.5-3.5.

Abstract

We analyze the spectral energy distributions (SEDs), star formation histories (SFHs), and infrared-radio correlation (IRRC) of 221 850 $\mu$m-selected submillimeter galaxies (SMGs) in the SSA22 deep field. The median mass-weighted age is 567 Myr. Most galaxies in our sample began forming $\sim$ 1.68 Gyr after the Big Bang, entered the `SMG phase' after $\sim$ 1 Gyr of evolution -- when they are predominantly observed -- and largely transitioned out of the `SMG phase' to become quiescent within an additional $\sim$ 0.2 Gyr. A subset of massive galaxies shows rapid early assembly with high star formation efficiencies ($\sim$0.2-0.8). The majority of SMGs reside at the high-mass end of the star-forming main sequence, with a characteristic stellar mass of $M_{star} \sim 10^{11}$ M$_\odot$, above which galaxies are predominantly either on the main sequence or already quenched. We observe a downsizing trend: more massive galaxies tend to ``mature" earlier, completing their major episodes of star formation at higher redshifts compared to lower-mass systems. Our sample contributes $\sim$ 21% (28%) to the cosmic star formation rate density (stellar mass density), including the overdensity, with its relative contribution peaking at 50-60% in the redshift range $z=2.5-3.5$. The median infrared-radio correlation parameter $q_{IR}$ is 2.37, evolving as $(1+z)^{-0.11}$, likely due to AGN contributions at high redshift and intrinsic differences between low- and high-redshift populations.