English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We use 85 pairs of high resolution LCDM cosmological simulations from theNIHAO project to investigate why in dwarf galaxies neutral hydrogen (HI)linewidths measured at 50% of the peak flux W_50 /2 (from the hydrodynamicalsimulations) tend to underpredict the maximum circular velocity VmaxDMO (fromthe corresponding dark matter only simulations). There are two maincontributing processes. 1) Lower mass galaxies are less rotationally supported.This is confirmed observationally from the skewness of linewidths in bins of HImass in both ALFALFA and HIPASS observations. 2) The HI distributions are lessextended (relative to the dark matter halo) in dwarf galaxies. Coupled to thelower baryon-to-halo ratio results in rotation curves that are still rising atthe last measured data point, in agreement with observations from SPARC.Combining these two effects, in both simulations and observations lower massgalaxies have on average lower W_50 / W_20. Additionally, mass loss driven bysupernovae and projection effects (dwarf galaxies are in general not thindisks) further reduce the linewidths. The implied HI linewidth velocityfunction from NIHAO is in good agreement with observations in the nearbyUniverse of dwarf galaxies: 10 < W_50 /2 < 80 km/s. The dark matter only slopeof -2.9 is reduced to -1.0 in the hydro simulations. Future radio observationsof unbiased samples with higher spatial resolution will enable stricter testsof the simulations, and thus of the LCDM model.

NIHAO XVII: The diversity of dwarf galaxy kinematics and implications for the HI velocity function