Accretion of gas from the cosmic web to galaxy halos and ultimately theirdisks is a prediction of modern cosmological models but is rarely observeddirectly or at the full rate expected from star formation. Here we illustratepossible large-scale cosmic HI accretion onto the nearby dwarf starburst galaxyIC10, observed with the VLA and GBT. We also suggest that cosmic accretion isthe origin of sharp metallicity drops in the starburst regions of other dwarfgalaxies, as observed with the 10-m GTC. Finally, we question the importance ofcosmic accretion in normal dwarf irregulars, for which a recent study of theirfar-outer regions sees no need for, or evidence of, continuing gas buildup.

By means of 3D hydrodynamical simulations, in a separate paper we havediscussed the properties of non-axisymmetric density wave trains in theoutermost regions of galaxy disks, based on the picture that self-excitedglobal spiral modes in the bright optical stellar disk are accompanied bylow-amplitude short trailing wave signals outside corotation; in the gas, suchwave trains can penetrate through the outer Lindblad resonance and propagateoutwards, forming prominent spiral patterns. In this paper we present thesynthetic 21~cm velocity maps expected from simulated models of the outergaseous disk, focusing on the case when the disk is dominated by a two-armedspiral pattern, but considering also other more complex situations. We discusssome aspects of the spiral pattern in the gaseous periphery of galaxy disksnoted in our simulations that might be interesting to compare with specificobserved cases.

We compare the mass and internal distribution of atomic hydrogen (HI) in 2200present-day central galaxies with M_star > 10^10 M_Sun from the 100 Mpc EAGLEReference simulation to observational data. Atomic hydrogen fractions arecorrected for self-shielding using a fitting formula from radiative transfersimulations and for the presence of molecular hydrogen using an empirical or atheoretical prescription from the literature. The resulting neutral hydrogenfractions, M_(HI+H2)/M_star, agree with observations to better than 0.1 dex forgalaxies with M_star between 10^10 and 10^11 M_Sun. Our fiducial, empirical H2model based on gas pressure results in galactic HI mass fractions, M_HI/M_star,that agree with observations from the GASS survey to better than 0.3 dex, butthe alternative theoretical H2 formula leads to a negative offset inM_HI/M_star of up to 0.5 dex. Visual inspection reveals that most HI disks insimulated HI-rich galaxies are vertically disturbed, plausibly due to recentaccretion events. Many galaxies (up to 80 per cent) contain spuriously large HIholes, which are likely formed as a consequence of the feedback implementationin EAGLE. The HI mass-size relation of all simulated galaxies is close to (but16 per cent steeper than) observed, and when only galaxies without large holesin the HI disc are considered, the agreement becomes excellent (better than 0.1dex). The presence of large HI holes also makes the radial HI surface densityprofiles somewhat too low in the centre, at \Sigma_HI > 1 M_Sun pc^-2 (by afactor of <~ 2 compared to data from the Bluedisk survey). In the outer region(\Sigma_HI < 1 M_Sun pc^-2), the simulated profiles agree quantitatively withobservations. Scaled by HI size, the simulated profiles of HI-rich (M_HI >10^9.8 M_Sun) and control galaxies (10^9.1 M_Sun > M_HI > 10^9.8 M_Sun) followeach other closely, as observed. (Abridged)

The radial profiles of stars in disc galaxies are observed to be eitherpurely exponential (Type-I), truncated (Type-II) or anti-truncated (Type-III)exponentials. Controlled formation simulations of isolated galaxies canreproduce all of these profile types by varying a single parameter, the initialhalo spin. In this paper we examine these simulations in more detail in aneffort to identify the physical mechanism that leads to the formation ofType-III profiles. The stars in the anti-truncated outskirts of such discs arenow on eccentric orbits, but were born on near-circular orbits at much smallerradii. We show that, and explain how, they were driven to the outskirts vianon-linear interactions with a strong and long-lived central bar, which greatlyboosted their semi-major axis but also their eccentricity. While bars have beenknown to cause radial heating and outward migration to stellar orbits, we linkthis effect to the formation of Type-III profiles. This predicts that theanti-truncated parts of galaxies have unusual kinematics for disc-like stellarconfigurations: high radial velocity dispersions and slow net rotation. Whethersuch discs exist in nature, can be tested by future observations.

The nearby lenticular galaxy NGC 1277 is thought to host one of the largestblack holes known, however the black hole mass measurement is based on lowspatial resolution spectroscopy. In this paper, we present Gemini Near-infraredIntegral Field Spectrometer observations assisted by adaptive optics. We mapout the galaxy's stellar kinematics within ~440 pc of the nucleus with anangular resolution that allows us to probe well within the region where thepotential from the black hole dominates. We find that the stellar velocitydispersion rises dramatically, reaching ~550 km/s at the center. Throughorbit-based, stellar-dynamical models we obtain a black hole mass of (4.9 \pm1.6) x 10^9 Msun (1-sigma uncertainties). Although the black hole massmeasurement is smaller by a factor of ~3 compared to previous claims based onlarge-scale kinematics, NGC 1277 does indeed contain one of the most massiveblack holes detected to date, and the black hole mass is an order of magnitudelarger than expectations from the empirical relation between black hole massand galaxy luminosity. Given the galaxy's similarities to the higher redshift(z~2) massive quiescent galaxies, NGC 1277 could be a relic, passively evolvingsince that period. A population of local analogs to the higher redshiftquiescent galaxies that also contain over-massive black holes may suggest thatblack hole growth precedes that of the host galaxy.

The classification "early-type" galaxy includes both elliptically- andlenticular-shaped galaxies. Theoretically, the spheroid-to-disc flux ratio ofan early-type galaxy can assume any positive value, but in practice studiesoften consider only spheroid/disc decompositions in which the disc neatlydominates over the spheroid at large galaxy radii, creating an inner "bulge" asobserved in most spiral galaxies. Here we show that decompositions in which thedisc remains embedded within the spheroid, labelled by some as "unphysical",correctly reproduce both the photometric and kinematic properties of early-typegalaxies with intermediate-scale discs. Intermediate-scale discs have oftenbeen confused with large-scale discs and incorrectly modelled as such; whenthis happens, the spheroid luminosity is considerably underestimated. This hasrecently led to some surprising conclusions, such as the claim that a number ofgalaxies with intermediate-scale discs (Mrk 1216, NGC 1277, NGC 1271, and NGC1332) host a central black hole whose mass is abnormally large compared toexpectations from the (underestimated) spheroid luminosity. We show that whenthese galaxies are correctly modelled, they no longer appear as extremeoutliers in the (black hole mass)-(spheroid mass) diagram. This not onlynullifies the need for invoking different evolutionary scenarios for thesegalaxies but it strengthens the significance of the observed (black holemass)-(spheroid mass) correlation and confirms its importance as a fundamentalingredient for theoretical and semi-analytic models used to describe thecoevolution of spheroids and their central supermassive black holes.

We present SAURON integral-field observations of a sample of 12 mid tohigh-inclination disk galaxies, to unveil hidden bars on the basis of theirkinematics, i.e., the correlation between velocity and h3 profiles, and toestablish their degree of cylindrical rotation. For the latter, we introduce amethod to quantify cylindrical rotation that is robust against inner diskcomponents. We confirm high-levels of cylindrical rotation in boxy/peanutbulges, but also observe this feature in a few galaxies with rounder bulges. Wesuggest that these are also barred galaxies with end-on orientations.Re-analysing published data for our own Galaxy using this new method, wedetermine that the Milky Way bulge is cylindrically rotating at the same levelas the strongest barred galaxy in our sample. Finally, we use self-consistentthree-dimensional N-body simulations of bar-unstable disks to study thedependence of cylindrical rotation on the bar's orientation and host galaxyinclination.