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The Chemical Nature of the Young 120-Myr-old Nearby Pisces-Eridanus Stellar Stream Flowing through the Galactic Disk

Recently, a new cylindrical-shaped stream of stars up to 700 pc long was discovered hiding in the Galactic disk using kinematic data enabled by the Gaia mission. This stream of stars, dubbed Pisces-Eridanus (Psc-Eri), was initially thought to be as old as 1 Gyr, yet its stars shared a rotation period distribution consistent with a population that was 120-Myr-old. Here, we explore the detailed chemical nature of this stellar stream. We carried out high-resolution spectroscopic follow-up of 42 Psc-Eri stars using McDonald Observatory, and combined these data with information for 40 members observed with the low-resolution LAMOST spectroscopic survey. Together, these data enabled us to measure the abundance distribution of light/odd-Z (Li, Na, Al, Sc, V), $α$ (Mg, Si, Ca, Ti), Fe-peak (Cr, Mn, Fe, Co, Ni, Zn), and neutron capture (Sr, Y, Zr, Ba, La, Nd, Eu) elements along the Psc-Eri stream. We find that the stream is (1) near solar metallicity with [Fe/H] = -0.03~dex and (2) has a metallicity spread of 0.07~dex (or 0.04 dex when outliers are excluded). We also find that (3) the abundance of Li indicates that Psc-Eri is $\sim$120 Myr old, consistent with its gyrochronology age. Additionally, Psc-Eri has (4) [X/Fe] abundance spreads which are just larger than the typical uncertainty in most elements, (5) it is a cylindrical-like system whose outer edges rotate about the center and, (6) no significant abundance gradients along its major axis except a potentially weak gradient in [Si/Fe]. These results show that Psc-Eri is a uniquely close, young, chemically interesting laboratory for testing our understanding of star and planet formation.