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We present a suite of baryonic cosmological zoom-in simulations of self-interacting dark matter (SIDM) haloes within the 'Feedback In Realistic Environment' (FIRE) project. The three simulated haloes have virial masses of ∼ 1012 M⊙ at z = 0, and we study velocity-independent self-interaction cross sections of 1 and 10 cm2, g-1. We study star formation rates and the shape of dark matter density profiles of the parent haloes in both cold dark matter (CDM) and SIDM models. Galaxies formed in the SIDM haloes have higher star formation rates at z ≤ 1, resulting in more massive galaxies compared to the CDM simulations. While both CDM and SIDM simulations show diverse shape of the dark matter density profiles, the SIDM haloes can reach higher and more steep central densities within few kpcs compared to the CDM haloes. We identify a correlation between the build-up of the stars within the half-mass radii of the galaxies and the growth in the central dark matter densities. The thermalization process in the SIDM haloes is enhanced in the presence of a dense stellar component. Hence, SIDM haloes with highly concentrated baryonic profiles are predicted to have higher central dark matter densities than the CDM haloes. Overall, the SIDM haloes are more responsive to the presence of a massive baryonic distribution than their CDM counterparts.

As the Milky Way and its satellite system become more entrenched in near field cosmology efforts, the need for an accurate mass estimate of the Milky Way's dark matter halo is increasingly critical. With the second and early third data releases of stellar proper motions from Gaia , several groups calculated full 6D phase-space information for the population of Milky Way satellite galaxies. Utilizing these data in comparison to subhalo properties drawn from the Phat ELVIS simulations, we constrain the Milky Way dark matter halo mass to be ∼1–1.2 × 1012 M⊙. We find that the kinematics of subhaloes drawn from more- or less-massive hosts (i.e. >1.2 × 1012 M⊙ or <1012 M⊙) are inconsistent, at the 3σ confidence level, with the observed velocities of the Milky Way satellites. The preferred host halo mass for the Milky Way is largely insensitive to the exclusion of systems associated with the Large Magellanic Cloud, changes in galaxy formation thresholds, and variations in observational completeness. As more Milky Way satellites are discovered, their velocities (radial, tangential, and total) plus Galactocentric distances will provide further insight into the mass of the Milky Way dark matter halo. [ABSTRACT FROM AUTHOR]

Hydrodynamic simulations provide a powerful, but computationally expensive, approach to study the interplay of dark matter and baryons in cosmological structure formation. Here, we introduce the EM ulating B aryonic E n R ichment (EMBER) Deep Learning framework to predict baryon fields based on dark matter-only simulations thereby reducing computational cost. EMBER comprises two network architectures, U-Net and Wasserstein Generative Adversarial Networks (WGANs), to predict 2D gas and H  i densities from dark matter fields. We design the conditional WGANs as stochastic emulators, such that multiple target fields can be sampled from the same dark matter input. For training we combine cosmological volume and zoom-in hydrodynamical simulations from the Feedback in Realistic Environments (FIRE) project to represent a large range of scales. Our fiducial WGAN model reproduces the gas and H  i power spectra within 10 per cent accuracy down to ∼10 kpc scales. Furthermore, we investigate the capability of EMBER to predict high resolution baryon fields from low resolution dark matter inputs through upsampling techniques. As a practical application, we use this methodology to emulate high-resolution H  i maps for a dark matter simulation of a |$L=100\, \text{Mpc}\, h^{ -1}$| comoving cosmological box. The gas content of dark matter haloes and the H  i column density distributions predicted by EMBER agree well with results of large volume cosmological simulations and abundance matching models. Our method provides a computationally efficient, stochastic emulator for augmenting dark matter only simulations with physically consistent maps of baryon fields. [ABSTRACT FROM AUTHOR]

The predominantly ancient stellar populations observed in the lowest mass galaxies (i.e. ultra-faint dwarfs) suggest that their star formation was suppressed by reionization. Most of the well-studied ultra-faint dwarfs, however, are within the central half of the Milky Way dark matter halo, such that they are consistent with a population that was accreted at early times and thus potentially quenched via environmental processes. To study the potential role of environment in suppressing star formation on the smallest scales, we utilize the Exploring the Local Volume in Simulations suite of N -body simulations to constrain the distribution of infall times for low-mass subhaloes likely to host the ultra-faint population. For the ultra-faint satellites of the Milky Way with star formation histories inferred from Hubble Space Telescope imaging, we find that environment is highly unlikely to play a dominant role in quenching their star formation. Even when including the potential effects of pre-processing, there is a |${\lesssim } 0.1{{\ \rm per\ cent}}$| probability that environmental processes quenched all of the known ultra-faint dwarfs early enough to explain their observed star formation histories. Instead, we argue for a mass floor in the effectiveness of satellite quenching at roughly |${M}_{\star }\sim 10^{5}\, {\rm M}_{\odot }$|⁠, below which star formation in surviving galaxies is globally suppressed by reionization. We predict a large population of quenched ultra-faint dwarfs in the Local Field (1 < R / R vir < 2), with as many as ∼250 to be discovered by future wide-field imaging surveys. [ABSTRACT FROM AUTHOR]

We present a combination of new and archival neutral hydrogen (HI) observations and new ionized gas spectroscopic observations for 16 galaxies in the statistically representative Extended Disk Galaxy Explore Science kinematic sample. HI rotation curves are derived from new and archival radio synthesis observations from the Very Large Array (VLA) as well as processed data products from the Westerbork Radio Synthesis Telescope (WSRT). The HI rotation curves are supplemented with optical spectroscopic integral field unit (IFU) observations using SparsePak on the WIYN 3.5 m telescope to constrain the central ionized gas kinematics in 12 galaxies. The full rotation curves of each galaxy are decomposed into baryonic and dark matter halo components using 3.6μm images from the Spitzer Space Telescope for the stellar content, the neutral hydrogen data for the atomic gas component, and, when available, CO data from the literature for the molecular gas component. Differences in the inferred distribution of mass are illustrated under fixed stellar mass-to-light ratio (M/L) and maximum disc/bulge assumptions in the rotation curve decomposition. [ABSTRACT FROM AUTHOR]

We present results from multiwavelength observations of the galaxy NGC 5005. We use new neutral hydrogen (HI) observations from the Very Large Array to examine the neutral gas morphology and kinematics. We find an HI disc with a well-behaved flat rotation curve in the radial range 20-140 arcsec. Ionized gas observations from the SparsePak integral field unit on the WIYN 3.5 m telescope provide kinematics for the central 70 arcsec. We use both the SparsePak and HI velocity fields to derive a rotation curve for NGC 5005. Deep 3.6 μm observations from the Spitzer Space Telescope probe the faint extended stellar population of NGC 5005. The images reveal a large stellar disc with a high surface brightness component that transitions to a low surface brightness component at a radius nearly 1.6 times farther than the extent of the gas disc detected in HI. The 3.6 μm image is also decomposed into bulge and disc components to account for the stellar light distribution. Optical broad-band B and R and narrowband Hα from the WIYN 0.9 m telescope complement the 3.6 μm data by providing information about the dominant stellar population and current star formation activity. The neutral and ionized gas rotation curve is used along with the stellar bulge and disc light profiles to decompose the mass distributions in NGC 5005 and determine a dark matter halo model. The maximum stellar disc contribution to the total rotation curve is only about 70 per cent, suggesting that dark matter makes a significant contribution to the dynamics at all radii. [ABSTRACT FROM AUTHOR]