The MUSE Extremely Deep Field: Evidence for SFR-induced cores in dark-matter dominated galaxies at z=1

TL;DR

This study uses deep MUSE data to analyze dark matter in low-mass star-forming galaxies at z=1, revealing high dark matter fractions, constant surface densities, and evidence for feedback-induced core formation.

Contribution

It introduces a novel 3D modeling approach for disk-halo decomposition of low-mass galaxies at z=1, providing detailed dark matter profile measurements and insights into core formation mechanisms.

Findings

Dark matter fractions within R_e range from 60% to 95%.

Half of the galaxies show preference for cored dark matter profiles.

Dark matter core presence correlates with recent star formation activity.

Abstract

Disc-halo decomposition on rotationally supported star-forming galaxies (SFGs) at $z>1$ are often limited to massive galaxies ($M_\star>10^{10}~M_\odot$) and rely on either deep Integral Field Spectroscopy data or stacking analyses. We present a study of the dark matter (DM) content of nine $z\approx1$ SFGs selected Using the brightest [OII] emitters in the deepest Multi-Unit Spectrograph Explorer (MUSE) field to date, namely the 140hr MUSE Extremely Deep Field, we perform disk-halo decompositions on 9 low-mass SFGs (with $10^{8.5}<M_\star<10^{10.5}~M_\odot$) using a novel 3D modeling approach, which together with the exquisite S/N allows us to measure individual rotation curves to $3\times R_e$. The disk-halo decomposition includes a stellar, DM, gas, and occasionally a bulge component. The DM component primarily uses the generalized $\alpha,\beta,\gamma$ profile or a Navarro-Frenk-White (NFW) profile. The disk stellar masses $M_\star$ obtained from the [OII] disk-halo decomposition agree with the values inferred from the spectral energy distributions. While the rotation curves show diverse shapes, ranging from rising to declining at large radii, the DM fractions within the half-light radius $f_{\rm DM}(<R_e)$ are found to be 60\% to 95\%, extending to lower masses (densities) recent results on massive SFGs with $M_\star>10^{10}~M_\odot$. The DM halos show constant surface densities of $\sim100~M_\odot$ pc$^{-2}$. Half of the sample shows a strong preference for cored over cuspy DM profiles. The presence of DM cores appears to be related to galaxies with stellar-to-halo mass $\log M_\star/M_{\rm vir}\approx-2.5$. In addition, the cuspiness of the DM profiles is found to be a strong function of the recent star-formation activity. Both of these results are interpreted as evidence for feedback-induced core formation in the Cold Dark Matter context.