The ALPINE-ALMA [C II] survey: Star-formation-driven outflows and circumgalactic enrichment in the early Universe

Abstract

We study the efficiency of galactic feedback in the early Universe by stacking the [C II] 158 µm emission in a large sample of normal star-forming galaxies at 4 < z < 6 from the ALMA Large Program to INvestigate [C II] at Early times (ALPINE) survey. Searching for typical signatures of outflows in the high-velocity tails of the stacked [C II] profile, we observe (i) deviations from a single-component Gaussian model in the combined residuals and (ii) broad emission in the stacked [C II] spectrum, with velocities of |v| 500 km s −1 . The significance of these features increases when stacking the subset of galaxies with star formation rates (SFRs) higher than the median (SFR med = 25 M yr −1 ), thus confirming their star-formation-driven nature. The estimated mass outflow rates are comparable to the SFRs, yielding mass-loading factors of the order of unity (similarly to local star-forming galaxies), suggesting that star-formation-driven feedback may play a lesser role in quenching galaxies at z > 4. From the stacking analysis of the datacubes, we find that the combined [C II] core emission (|v| < 200 km s −1 ) of the higher-SFR galaxies is extended on physical sizes of ∼ 30 kpc (diameter scale), well beyond the analogous [C II] core emission of lower-SFR galaxies and the stacked far-infrared continuum. The detection of such extended metal-enriched gas, likely tracing circumgalactic gas enriched by past outflows, corroborates previous similar studies, confirming that baryon cycle and gas exchanges with the circumgalactic medium are at work in normal star-forming galaxies already at early epochs.Article number, page 16 of 16

The ALPINE-ALMA [CII] survey: Data processing, catalogs, and statistical source properties

“…In addition, at z > 4, it is conveniently redshifted to the >850 µm atmospheric windows. This line has a variety of different scientific applications since it can be used to probe the interstellar medium (e.g., Zanella et al 2018), the SFR (e.g., De Looze et al 2014;Carniani et al 2018a), the gas dynamics (e.g., De Breuck et al 2014;Jones et al 2020), or outflows (e.g., Maiolino et al 2012;Gallerani et al 2018;Ginolfi et al 2020a). It has now been detected in ∼35 galaxies at z > 4, but most of them are magnified by lensing or starbursts and only one third of them are normal star-forming systems (see compilation in Lagache et al 2018).…”

The nature of CR7 revealed with MUSE: a young starburst powering extended Ly α emission at z = 6.6

“…[CII] emission is also reported to be significantly more extended than the UV continuum (e.g. Fujimoto et al 2019;Ginolfi et al 2020), possibly tracing past outflow activity (Pizzati et al 2020).…”

High-redshift star formation in the Atacama large millimetre/submillimetre array era

“…Targeted studies such as the ALMA Large Programme to INvestigate [CII] at Early times (ALPINE) survey (e.g. [584,[640][641][642][643][644]) are a more promising way to detect [CII] emission at high-redshift. ALPINE targeted a sample of 118 spectroscopically confirmed star-forming galaxies at 4.4 < z < 5.9 with a typical beam size of 0.7 arcsec (≃6 kpc).…”

“…Multi-tracer studies can dissect the multi-phase ISM as well as material inflows/outflows of such sources by analysing the spatial distribution and velocity offsets of Ly α , [OIII] and [CII] emission (when detected) with resolved observations (e.g. [ 204 , 291 , 459 , 549 , 572 , 584 , 585 ]).…”

“…They detect 64% of their targets, and show that their detections are diverse in terms of morphology and kinematics, including rotating discs and mergers. ALPINE is only starting to produce results at the time of writing, but it is already demonstrating how ALMA can take advantage of the brightness of [CII] in star-forming galaxies to trace their detailed structure and kinematics [ 642 ], and even detect gas outflows and metal enrichment of the circumgalactic medium in the early Universe [ 584 ].…”