We report on the results of radio observations in the 21 cm emission line ofatomic hydrogen (HI) of four relatively isolated ultra-diffuse galaxies (UDGs):DGSAT I, R-127-1, M-161-1, and SECCO-dI-2. Our Effelsberg observations resultedin non-detections for the first three UDGs, and a clear detection for the last.DGSAT I, R-127-1, and M-161-1 are quiescent galaxies with gas fractions thatare much lower than those of typical field galaxies of the same stellar mass.On the other hand, SECCO-dI-2 is a star forming gas-rich dwarf, similar to twoother field UDGs that have literature HI data: SECCO-dI-1 and UGC 2162. Thisgroup of three gas-rich UDGs have stellar and gaseous properties that arecompatible with a recently proposed theoretical mechanism for the formation ofUDGs, based on feedback-driven outflows. In contrast, the physicalcharacteristics of R-127-1 and M-161-1 are puzzling, given their isolatednature. We interpret this dichotomy in the gaseous properties of field UDGs asa sign of the existence of multiple mechanisms for their formation, with theformation of the quiescent gas-poor UDGs remaining a mystery.

We present a sample of 115 very low optical surface brightness, highlyextended, HI-rich galaxies carefully selected from the ALFALFA survey that havesimilar optical absolute magnitudes, surface brightnesses, and radii torecently discovered "ultra-diffuse" galaxies (UDGs). However, these systems arebluer and have more irregular morphologies than other UDGs, are isolated, andcontain significant reservoirs of HI. We find that while these sources havenormal star formation rates for HI selected galaxies of similar stellar mass,they have very low star formation efficiencies. We further present deep opticaland HI synthesis follow up imaging of three of these HI-bearing ultra-diffusesources. We measure HI diameters extending to ~40 kpc, but note that while allthree sources have large HI diameters for their stellar mass, they areconsistent with the HI mass - HI radius relation. We further analyze the HIvelocity widths and rotation velocities for the unresolved and resolved sourcesrespectively, and find that the sources appear to inhabit halos of dwarfgalaxies. We estimate spin parameters, and suggest that these sources may existin high spin parameter halos, and as such may be potential HI-rich progenitorsto the ultra-diffuse galaxies observed in cluster environments.

We exploit the deep resolved Halpha kinematic data from the KMOS^3D andSINS/zC-SINF surveys to examine the largely unexplored outer disk kinematics ofstar-forming galaxies (SFGs) out to the peak of cosmic star formation. Oursample contains 101 SFGs representative of the more massive (9.3 < log(M*/Msun)< 11.5) main sequence population at 0.6<z<2.6. Through a novel stackingapproach we are able to constrain a representative rotation curve extending outto ~4 effective radii. This average rotation curve exhibits a significant dropin rotation velocity beyond the turnover, with a slope of Delta(V)/Delta(R) =$-0.26^{+0.10}_{-0.09}$ in units of normalized coordinates V/V_max andR/R_turn. This result confirms that the fall-off seen previously in someindividual galaxies is a common feature of our sample of high-z disks. We showthat this outer fall-off strikingly deviates from the flat or mildly risingrotation curves of local spiral galaxies of similar masses. We furthermorecompare our data with models including baryons and dark matter demonstratingthat the falling stacked rotation curve can be explained by a high massfraction of baryons relative to the total dark matter halo (m_d>~0.05) incombination with a sizeable level of pressure support in the outer disk. Thesefindings are in agreement with recent studies demonstrating that star-formingdisks at high redshift are strongly baryon dominated within the disk scale, andfurthermore suggest that pressure gradients caused by large turbulent gasmotions are present even in their outer disks. We demonstrate that theseresults are largely independent of our model assumptions such as the presenceof a central stellar bulge, the effect of adiabatic contraction at fixed m_d,and variations in the concentration parameter.

In cold dark matter cosmology, the baryonic components of galaxies arethought to be mixed with and embedded in non-baryonic and non-relativistic darkmatter, which dominates the total mass of the galaxy and its dark matter halo.In the local Universe, the mass of dark matter within a galactic disk increaseswith disk radius, becoming appreciable and then dominant in the outer, baryonicregions of the disks of star-forming galaxies. This results in rotationvelocities of the visible matter within the disk that are constant orincreasing with disk radius. Comparison between the dynamical mass and the sumof stellar and cold gas mass at the peak epoch of galaxy formation, inferredfrom ancillary data, suggest high baryon factions in the inner, star-formingregions of the disks. Although this implied baryon fraction may be larger thanin the local Universe, the systematic uncertainties (stellar initial massfunction, calibration of gas masses) render such comparisons inconclusive interms of the mass of dark matter. Here we report rotation curves for the outerdisks of six massive star-forming galaxies, and find that the rotationvelocities are not constant, but decrease with radius. We propose that thistrend arises because of two main factors: first, a large fraction of themassive, high-redshift galaxy population was strongly baryon dominated, withdark matter playing a smaller part than in the local Universe; and second, thelarge velocity dispersion in high-redshift disks introduces a substantialpressure term that leads to a decrease in rotation velocity with increasingradius. The effect of both factors appears to increase with redshift.Qualitatively, the observations suggest that baryons in the early Universeefficiently condensed at the centres of dark matter halos when gas fractionswere high, and dark matter was less concentrated. [Abridged]

We investigate the stellar mass and baryonic mass Tully-Fisher relations(TFRs) of massive star-forming disk galaxies at redshift z~2.3 and z~0.9 aspart of the KMOS^3D integral field spectroscopy survey. Our spatially resolveddata allow reliable modelling of individual galaxies, including the effect ofpressure support on the inferred gravitational potential. At fixed circularvelocity, we find higher baryonic masses and similar stellar masses at z~2.3 ascompared to z~0.9. Together with the decreasing gas-to-stellar mass ratios withdecreasing redshift, this implies that the contribution of dark matter to thedynamical mass at the galaxy scale increases towards lower redshift. Acomparison to local relations reveals a negative evolution of the stellar andbaryonic TFR zero-points from z=0 to z~0.9, no evolution of the stellar TFRzero-point from z~0.9 to z~2.3, and a positive evolution of the baryonic TFRzero-point from z~0.9 to z~2.3. We discuss a toy model of disk galaxy evolutionto explain the observed, non-monotonic TFR evolution, taking into account theempirically motivated redshift dependencies of galactic gas fractions, and ofthe relative amount of baryons to dark matter on galaxy and halo scales.

As a part of the mm-Wave Interferometric Survey of Dark Object Masses(WISDOM) project, we present an estimate of the mass of the supermassive blackhole (SMBH) in the nearby fast-rotator early-type galaxy NGC 3665. We obtainedCombined Array for Research in Millimeter Astronomy (CARMA) B and C arrayobservations of the $^{12}$CO$(J=2-1)$ emission line with a combined angularresolution of $0".59$. We analysed and modelled the three-dimensional moleculargas kinematics, obtaining a best-fit SMBH mass $M_{\rm BH}=5.75^{+1.49}_{-1.18}\times 10^{8}$ $M_{\odot}$, a mass-to-light ratio at $H$-band$(M/L)_{H}=1.45\pm0.04$ $(M/L)_{\odot, H}$, and other parameters describing thegeometry of the molecular gas disc (statistical errors, all at $3\sigma$confidence). We estimate the systematic uncertainties on the stellar $M/L$ tobe $\approx0.2$ $(M/L)_{\odot, H}$, and on the SMBH mass to be$\approx0.4\times10^{8}$ $M_{\odot}$. The measured SMBH mass is consistent withthat estimated from the latest correlations with galaxy properties. Followingour older works, we also analysed and modelled the kinematics using only themajor-axis position-velocity diagram, and conclude that the two methods areconsistent.

As part of the mm-Wave Interferometric Survey of Dark Object Masses (WISDOM)project, we present an estimate of the mass of the supermassive black hole(SMBH) in the nearby fast-rotating early-type galaxy NGC4697. This estimate isbased on Atacama Large Millimeter/submillimeter Array (ALMA) cycle-3observations of the 12CO(2-1) emission line with a linear resolution of 29 pc(0.53"). We find that NGC4697 hosts a small relaxed central molecular gas discwith a mass of 1.6x10^7 Msun, co-spatial with the obscuring dust disc visiblein optical Hubble Space Telescope (HST) imaging. We also resolve thermal 1mmcontinuum emission from the dust in this disc. NGC4697 is found to have a verylow molecular gas velocity dispersion, $\sigma_{gas}=1.65^{+0.68}_{-0.65}$km/s. This seems to be partially because the giant molecular cloud massfunction is not fully sampled, but other mechanisms such as chemicaldifferentiation in a hard radiation field or morphological quenching also seemto be required. We detect a Keplerian increase of the rotation of the moleculargas in the very centre of NGC4697, and use forward modelling of the ALMA datacube in a Bayesian framework with the KINematic Molecular Simulation (KinMS)code to estimate a SMBH mass of ($1.3_{-0.17}^{+0.18})\times10^8$ Msun and ani-band mass-to-light ratio of $2.14_{-0.05}^{+0.04}$ Msun/Lsun (at the 99%confidence level). Our estimate of the SMBH mass is entirely consistent withprevious measurements from stellar kinematics. This increases confidence in thegrowing number of SMBH mass estimates being obtained in the ALMA era.