We study the dependence of the galaxy content of dark matter halos on large-scale environment and halo formation time using semi-analytic galaxy models applied to the Millennium simulation. We analyze subsamples of halos at the extremes of these distributions and measure the occupation functions for the galaxies they host. We find distinct differences in these occupation functions. The main effect with environment is that central galaxies (and in one model also the satellites) in denser regions start populating lower-mass halos. A similar, but significantly stronger, trend exists with halo age, where early-forming halos are more likely to host central galaxies at lower halo mass. We discuss the origin of these trends and the connection to the stellar mass -halo mass relation. We find that, at fixed halo mass, older halos and to some extent also halos in dense environments tend to host more massive galaxies. Additionally, we see a reverse trend for the satellite galaxies occupation where early-forming halos have fewer satellites, likely due to having more time for them to merge with the central galaxy. We describe these occupancy variations also in terms of the changes in the occupation function parameters, which can aid in constructing realistic mock galaxy catalogs. Finally, we study the corresponding galaxy auto-and cross-correlation functions of the different samples and elucidate the impact of assembly bias on galaxy clustering. Our results can inform theoretical models of assembly bias and attempts to detect it in the real universe.

We study the gas kinematics traced by the 21-cm emission of a sample of six H i-rich low surface brightness galaxies classified as ultra-diffuse galaxies (UDGs). Using the 3D kinematic modelling code 3D Barolo we derive robust circular velocities, revealing a startling feature: H i-rich UDGs are clear outliers from the baryonic Tully-Fisher relation, with circular velocities much lower than galaxies with similar baryonic mass. Notably, the baryon fraction of our UDG sample is consistent with the cosmological value: these UDGs are compatible with having no "missing baryons" within their virial radii. Moreover, the gravitational potential provided by the baryons is sufficient to account for the amplitude of the rotation curve out to the outermost measured point, contrary to other galaxies with similar circular velocities. We speculate that any formation scenario for these objects will require very inefficient feedback and a broad diversity in their inner dark matter content.

Ultra-diffuse galaxies have generated significant interest due to their large optical extents and low optical surface brightnesses, which challenge galaxy formation models. Here we present resolved synthesis observations of 12 H i-bearing ultra-diffuse galaxies (HUDs) from the Karl G. Jansky Very Large Array, as well as deep optical imaging from the WIYN 3.5 m telescope at Kitt Peak National Observatory. We present the data processing and images, including total intensity H i maps and H i velocity fields. The HUDs show ordered gas distributions and evidence of rotation, important prerequisites for the detailed kinematic models of Mancera Piña et al. We compare the H i and stellar alignment and extent, and find that H i extends beyond the already extended stellar component and the H i disk is often misaligned with respect to the stellar one, emphasizing the importance of caution when approaching inclination measurements for these extreme sources. We explore the H i mass–diameter scaling relation, and find that, although the HUDs have diffuse stellar populations, they fall along the relation with typical global H i surface densities. This resolved sample forms an important basis for more detailed study of the H i distribution in this extreme extragalactic population.

Background Increasing epithelial chloride (Cl−) secretion in the upper airways represents a putative method for promoting MCC through augmentation of airway surface liquid depth. Several naturally occurring flavonoid compounds, including quercetin, have demonstrated the capacity to increase transepithelial Cl− transport. Quercetin exhibits well-known antioxidant and anti-inflammatory activity and is now recognized as a potent activator of the cystic fibrosis transmembrane conductance regulator (CFTR) anion channel activity in a fashion largely independent of cAMP signaling. The present study investigates whether this compound activates Cl− secretion and ciliary beat frequency (CBF) in well characterized culture models of sinonasal epithelium. Methods CF and non-CF primary human sinonasal (HSNE) and murine nasal septal epithelial (MNSE) cultures were studied for transepithelial ion transport in Ussing chambers under voltage clamp conditions and CBF was performed using pharmacologic manipulation. Results Change in short circuit current (ΔISC -expressed as μA/cm2) in response to quercetin were significantly greater than controls in both MNSE (23.23+/−5.44 vs. 2.47 +/− 1.62, p<0.0001) and HSNE (−8.72+/−1.88 vs. −1.88+/−0.66, p<0.01) cultures. CBF was significantly increased in quercetin-treated cells (expressed as fold-change over baseline) in w.t. [1.65+/−0.13 vs. 1.23+/−0.05 (control), p<0.01), but not CFTR−/− (1.65+/−0.29 vs. 1.48+/−0.38, p = 0.23). Conclusions Quercetin significantly increased transepithelial Cl− transport and CBF in MNSE and HSNE cultures. Future studies investigating quercetin as a means to promote mucociliary transport in individuals with rhinosinusitis are warranted.