Effect Of Adiabatic Contraction Research Articles

Velocity-dependent self-interacting dark matter from groups and clusters of galaxies

We probe the self-interactions of dark matter with relaxed galaxy groups and clusters using observational data from strong and weak lensing and stellar kinematics. Our analysis uses the Jeans formalism and considers a wider range of systematic effects than in previous work, including adiabatic contraction and stellar anisotropy, to robustly constrain the self-interaction cross section. For both groups and clusters, our results show a mild preference for a nonzero cross section compared with cold collisionless dark matter. Our groups result, σ/m=0.5±0.2 cm2/g, places the first constraint on self-interacting dark matter (SIDM) at an intermediate scale M200∼ 1014 M⊙ between galaxies and massive clusters. For massive clusters with M200∼ 1015 M⊙, our result is σ/m=0.19±0.09 cm2/g, with an upper limit of σ / m < 0.35 cm2/g (95% CL) . Thus, our results disfavor a velocity-independent cross section of order 1 cm2/g or larger needed to impact small scale structure problems in galaxies, but are consistent with a velocity-dependent cross section that decreases with increasing scattering velocity. Comparing the cross sections with and without the effect of adiabatic contraction, we find that adiabatic contraction produces slightly larger values for our data sample, but they are consistent at the 1σ level. Finally, to validate our approach, we apply our Jeans analysis to a sample of mock data generated from SIDM-plus-baryons simulations with σ/m = 1 cm2/g. This is the first test of the Jeans model at the level of stellar and lensing observables directly measured from simulations. We find our analysis gives a robust determination of the cross section, as well as consistently inferring the true baryon and dark matter density profiles.

Falling Outer Rotation Curves of Star-forming Galaxies at 0.6 ≲ z ≲ 2.6 Probed with KMOS3D and SINS/zC-SINF

Abstract We exploit the deep, resolved, Hα kinematic data from the KMOS3D and SINS/zC-SINF surveys to examine the largely unexplored outer-disk kinematics of star-forming galaxies (SFGs), out to the peak of cosmic star formation. Our sample contains 101 SFGs, representative of the more massive ( ) main sequence population at 0.6 ≤ z ≤ 2.6. Through a novel stacking approach, we are able to constrain a representative rotation curve extending out to ∼4 effective radii. This average rotation curve exhibits a significant drop in rotation velocity beyond the turnover, with a slope of in units of normalized coordinates V/V max and R/R turn. This result confirms that the fall-off seen in some individual galaxies is a common feature of our sample of high-z disks. The outer fall-off strikingly deviates from the flat or mildly rising rotation curves of local spiral galaxies that have similar masses. Through a comparison with models that include baryons and dark matter, we demonstrate that the falling stacked rotation curve is consistent with a high mass fraction of baryons, relative to the total dark matter halo (m d ≳ 0.05), in combination with a sizeable level of pressure support in the outer disk. These findings agree with recent studies demonstrating that high-z star-forming disks are strongly baryon-dominated within the disk scale, and furthermore suggest that pressure gradients caused by large, turbulent gas motions are present even in their outer disks. These results are largely independent of our model assumptions, such as the presence of stellar bulges, the effect of adiabatic contraction, and variations in halo concentration.

THE NEXT GENERATION VIRGO CLUSTER SURVEY. IX. ESTIMATING THE EFFICIENCY OF GALAXY FORMATION ON THE LOWEST-MASS SCALES

The Next Generation Virgo Cluster Survey has recently determined the luminosity function of galaxies in the core of the Virgo cluster down to unprecedented magnitude and surface brightness limits. Comparing simulations of cluster formation to the derived central stellar mass function, we attempt to estimate the stellar-to-halo-mass ratio (SHMR) for dwarf galaxies, as it would have been before they fell into the cluster. This approach ignores several details and complications, e.g., the contribution of ongoing star formation to the present-day stellar mass of cluster members, and the effects of adiabatic contraction and/or violent feedback on the subhalo and cluster potentials. The final results are startlingly simple, however; we find that the trends in the SHMR determined previously for bright galaxies appear to extend down in a scale-invariant way to the faintest objects detected in the survey. These results extend measurements of the formation efficiency of field galaxies by two decades in halo mass, or five decades in stellar mass, down to some of the least massive dwarf galaxies known, with stellar masses of $\sim 10^5 M_\odot$.