The MUSE Extremely Deep Field: Evidence for SFR-induced cores in dark-matter dominated galaxies atz≃ 1

Abstract

Context. Disc-halo decompositions z = 1 − 2 star-forming galaxies (SFGs) at z > 1 are often limited to massive galaxies (M⋆ > 1010 M⊙) and rely on either deep integral field spectroscopy data or stacking analyses. Aims. We present a study of the dark-matter (DM) content of nine z ≈ 1 SFGs selected among the brightest [O II] emitters in the deepest Multi-Unit Spectrograph Explorer (MUSE) field to date, namely the 140 h MUSE Extremely Deep Field. These SFGs have low stellar masses, ranging from 108.5 to 1010.5 M⊙. Methods. We analyzed the kinematics with a 3D modeling approach, which allowed us to measure individual rotation curves to ≈3 times the half-light radius Re. We performed disk-halo decompositions on their [O II] emission line with a 3D parametric model. The disk-halo decomposition includes a stellar, DM, gas, and occasionally a bulge component. The DM component primarily uses the generalized α, β, γ profile or a Navarro-Frenk-White profile. Results. The disk stellar masses M⋆ obtained from the [O II] 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 fDM(< Re) are found to be 60% to 95%, extending to lower masses (densities) recent results who found low DM fractions in SFGs with M⋆ > 1010 M⊙. The DM halos show constant surface densities of ∼100 M⊙ pc−2. For isolated galaxies, 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 low stellar-to-halo mass ratio, log M⋆/Mvir ≈ −2.5. In addition, the cuspiness of the DM profiles is found to be a strong function of the recent star-formation activity. Conclusions. We measured the properties of DM halos on scales from 1 to 15 kpc, put constraints on the z > 0 cvir − Mvir scaling relation, and unveiled the cored nature of DM halos in some z ≃ 1 SFGs. These results support feedback-induced core formation in the cold dark matter context.

Observational evidence of evolving dark matter profiles atz ≤ 1

“…Providing the various results and comparisons of the NFW and Burkert halo in the case of individual and coadded RCs, we found that our current sample favors the Burkert halo model and also agrees quite well with the simulations. Moreover, the recent studies by Genzel et al (2020) and Bouché et al (2022) also found a cored profile in majority of their SFGs at z ∼ 1. Therefore, we focus on discussing the Burkert halo results in what follows.…”

“…In particular, Genzel et al (2020) dynamically mass modeled the RCs of 41 star-forming galaxies (SFGs), and provided the first piece of evidence of a cored DM profile at high-z (in the majority of the sample). Moreover, in a more recent study, Bouché et al (2022) dynamically mass-modeled the nine z ≈ 1 SFGs and they show that, similar to the z ∼ 1 sample of Genzel et al (2020), a significant fraction of their sample also shows evidence of a cored DM profile. The study of Bouché et al (2022) also shows that the DM "cored" feature is generally associated with galaxies with low stellar-to-halo mass, while "cusps" are found to be a function of strong star-formation activity.…”

“…Moreover, in a more recent study, Bouché et al (2022) dynamically mass-modeled the nine z ≈ 1 SFGs and they show that, similar to the z ∼ 1 sample of Genzel et al (2020), a significant fraction of their sample also shows evidence of a cored DM profile. The study of Bouché et al (2022) also shows that the DM "cored" feature is generally associated with galaxies with low stellar-to-halo mass, while "cusps" are found to be a function of strong star-formation activity. They conclude that this suggests feedback-induced core formation in the ΛCDM scenario.…”

Observational constraints on stellar feedback in dwarf galaxies

“…They find an anticorrelation between the inner dark matter density (measured at 150 pc) and M * /M 200 , with the approximate transition from cuspy to cored systems occurring at M * /M 200 ∼ 5 × 10 −4 , exactly as predicted by [152]. These results have been corroborated and expanded upon by [22]. Their data overlap with [21] at M * /M 200 ∼ 5×10 −3 , but extend to higher M * /M 200 , showing the increasing inefficiency of dark matter heating as M * /M 200 rises above ∼ 10 −2 , again as predicted by [152].…”

“…Indeed, there is mounting dynamical evidence for this in dwarf galaxies at both low and high redshift [e.g. 21,22,23]. Finally, for the very smallest galaxies (M * < 10 5−6 M ), ionising radiation from the first stars and galaxies in the early Universe (z ∼ 8 − 12) heats their ISM shutting off further accretion of cold gas [e.g.…”