1. The ALPINE-ALMA [C II] survey: Investigation of 10 galaxies at z ∼ 4.5 with [O II] and [C II] line emission − ISM properties and [O II]−SFR relation
- Author
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Vanderhoof, Brittany N., Faisst, A. L., Shen, L., Lemaux, B. C., Béthermin, M., Capak, P. L., Cassata, P., Le Fèvre, O., Schaerer, D., Silverman, J., Yan, L., Boquien, M., Gal, R., Kartaltepe, J., Lubin, L. M., Dessauges-Zavadsky, M., Fudamoto, Y., Ginolfi, M., Hathi, N. P., Jones, G. C., Koekemoer, A. M., Narayanan, D., Romano, M., Talia, M., Vergani, D., and Zamorani, G.
- Abstract
We present 10 main-sequence ALPINE galaxies (log (M/M_⊙) = 9.2−11.1 and SFR = 23−190 M_⊙ yr⁻¹) at z ∼ 4.5 with optical [O II] measurements from Keck/MOSFIRE spectroscopy and Subaru/MOIRCS narrow-band imaging. This is the largest such multiwavelength sample at these redshifts, combining various measurements in the ultraviolet, optical, and far-infrared including [C II]_(158 μm) line emission and dust continuum from ALMA and H α emission from Spitzer photometry. For the first time, this unique sample allows us to analyse the relation between [O II] and total star-formation rate (SFR) and the interstellar medium (ISM) properties via [O II]/[C II] and [O II]/H α luminosity ratios at z ∼ 4.5. The [O II]−SFR relation at z ∼ 4.5 cannot be described using standard local descriptions, but is consistent with a metal-dependent relation assuming metallicities around 50 per cent solar. To explain the measured dust-corrected luminosity ratios of log(L_[OII]/L_[CII]) ∼ 0.98^(+0.21)_(−0.22) and log(L_[OII]/L_(Hα)) ∼ −0.22^(+0.13)_(−0.15) for our sample, ionization parameters log (U) < −2 and electron densities log(nₑ/[cm⁻³]) ∼ 2.5−3 are required. The former is consistent with galaxies at z ∼ 2−3, however lower than at z > 6. The latter may be slightly higher than expected given the galaxies’ specific SFR. The analysis of this pilot sample suggests that typical log (M/M_⊙) > 9 galaxies at z ∼ 4.5 to have broadly similar ISM properties as their descendants at z ∼ 2 and suggest a strong evolution of ISM properties since the epoch of reionization at z > 6.
- Published
- 2022