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Spatially resolved emission-line kinematics are invaluable for investigating fundamental galaxy properties and have become increasingly accessible for galaxies at z ≳0.5 through sensitive near-infrared imaging spectroscopy and millimeter interferometry. Kinematic modeling is at the core of the analysis and interpretation of such data sets, which at high z present challenges due to the lower signal-to-noise ratio (S/N) and resolution compared to the data of local galaxies. We present and test the 3D fitting functionality of DysmalPy, examining how well it recovers the intrinsic disk rotation velocity and velocity dispersion, using a large suite of axisymmetric models, covering a range of galaxy properties and observational parameters typical of z ∼ 1−3 star-forming galaxies. We also compare DysmalPy's recovery performance to that of two other commonly used codes, GalPak3D and 3DBarolo, which we use in turn to create additional sets of models to benchmark DysmalPy. Over the ranges of S/N, resolution, mass, and velocity dispersion explored, the rotation velocity is accurately recovered by all tools. The velocity dispersion is recovered well at high S/N, but the impact of methodology differences is more apparent. In particular, template differences for parametric tools and S/N sensitivity for the nonparametric tool can lead to differences of up to a factor of 2. Our tests highlight and the importance of deep, high-resolution data and the need for careful consideration of (i) the choice of priors (parametric approaches); and (ii) the masking (all approaches); and (iii), more generally, the evaluating of the suitability of each approach to the specific data at hand. This paper accompanies the public release of DysmalPy. [ABSTRACT FROM AUTHOR]

We present an analysis of the relationship between the CO–H2 conversion factor (αCO) and total mass surface density (tot) in star-forming galaxies at z < 1.5. Our sample, which is drawn from the IRAM Plateau de Bure HIgh-z Blue Sequence Survey (PHIBSS) and the CO Legacy Database for GASS (COLD GASS), includes ‘normal’, massive star-forming galaxies that dominate the evolution of the cosmic star formation rate (SFR) at this epoch and probe the tot regime where the strongest variation in αCO is observed. We constrain αCO via existing CO observations, measurements of the SFR and an assumed molecular gas depletion time (tdep = Mgas/SFR) – the latter two of which establish the total molecular gas mass independent of the observed CO luminosity. For a broad range of adopted depletion times, we find that αCO is independent of total mass surface density, with little deviation from the canonical Milky Way value. This runs contrary to a scenario in which αCO decreases as surface density increases within the extended clouds of molecular gas that potentially fuel clumps of star formation in z ∼ 1 galaxies, similar to those observed in local ultra-luminous infrared galaxies. Instead, our results suggest that molecular gas, at both z ∼ 0 and z ∼ 1, is primarily in the form of self-gravitating molecular clouds. While CO observations suggest a factor of ∼3 reduction in the average molecular gas depletion time between z ∼ 0 and z ∼ 1, we find that, for typical galaxies, the structure of molecular gas and the process of star formation at z ∼ 1 is otherwise remarkably similar to that observed in local star-forming systems.

We compare ionized gas and stellar kinematics of 16 star-forming galaxies (log (M ⋆/ M ⊙) = 9.7–11.2, SFR =6 − 86 M⊙ yr−1) at z ∼ 1 using near-infrared integral field spectroscopy (IFS) of Hα emission from the KMOS3D (the K-band Multi-Object Spectrograph 3D) survey and optical slit spectroscopy of stellar absorption and gas emission from the LEGA-C (Large Early Galaxy Astrophysics Census) survey. Hα is dynamically colder than stars, with higher disc rotation velocities (by ∼45 per cent) and lower disc velocity dispersions (by a factor ∼2). This is similar to trends observed in the local Universe. We find higher rotational support for Hα relative to [O  ii ], potentially explaining systematic offsets in kinematic scaling relations found in the literature. Regarding dynamical mass measurements, for six galaxies with cumulative mass profiles from Jeans Anisotropic Multi-Gaussian Expansion (JAM) models the Hα dynamical mass models agree remarkably well out to ∼10 kpc for all but one galaxy (average |$\Delta M_{\rm dyn}(R_{e,\rm F814W})\lt 0.1$| dex). Simpler dynamical mass estimates based on integrated stellar velocity dispersion are less accurate (standard deviation 0.24 dex). Differences in dynamical mass estimates are larger, for example, for galaxies with stronger misalignments of the Hα kinematic major axis and the photometric position angle, highlighting the added value of IFS observations for dynamics studies. The good agreement between the JAM and the dynamical models based on Hα kinematics at z ∼ 1 corroborates the validity of dynamical mass measurements from Hα IFS observations, which can be more easily obtained for higher redshift galaxies. [ABSTRACT FROM AUTHOR]

Radial-velocity monitoring has revealed the presence of moving broad emission lines in some quasars, potentially indicating the presence of a subparsec binary system. Phase-referenced, near-infrared interferometric observations could map out the binary orbit by measuring the photocenter difference between a broad emission line and the hot dust continuum. We show that astrometric data over several years may be able to detect proper motions and accelerations, confirming the presence of a binary and constraining system parameters. The brightness, redshifts, and astrometric sizes of current candidates are well matched to the capabilities of the upgraded Very Large Telescope Interferometer/GRAVITY+ instrument, and we identify a first sample of 10 possible candidates. The astrometric signature depends on the morphology and evolution of hot dust emission in supermassive black hole binary systems. Measurements of the photocenter offset may reveal binary motion whether the hot dust emission region is fixed to the inner edge of the circumbinary disk, or moves in response to the changing irradiation pattern from an accreting secondary black hole. [ABSTRACT FROM AUTHOR]

We present 0.″2 resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations at 870 μm in a stellar mass–selected sample of 85 massive () star-forming galaxies (SFGs) at in the CANDELS/3D-Hubble Space Telescope fields of UDS and GOODS-S. We measure the effective radius of the rest-frame far-infrared (FIR) emission for 62 massive SFGs. They are distributed over wide ranges of FIR size from to. The effective radius of the FIR emission is smaller by a factor of than the effective radius of the optical emission and is smaller by a factor of than the half-mass radius. Taking into account potential extended components, the FIR size would change only by ∼10%. By combining the spatial distributions of the FIR and optical emission, we investigate how galaxies change the effective radius of the optical emission and the stellar mass within a radius of 1 kpc,. The compact starburst puts most of the massive SFGs on the mass–size relation for quiescent galaxies (QGs) at z ∼ 2 within 300 Myr if the current star formation activity and its spatial distribution are maintained. We also find that within 300 Myr, ∼38% of massive SFGs can reach the central mass of , which is around the boundary between massive SFGs and QGs. These results suggest an outside-in transformation scenario in which a dense core is formed at the center of a more extended disk, likely via dissipative in-disk inflows. Synchronized observations at ALMA 870 μm and James Webb Space Telescope 3–4 μm will explicitly verify this scenario. [ABSTRACT FROM AUTHOR]

Over the past decade, increasingly robust estimates of the dense molecular gas content in galaxy populations between redshift z = 0 and the peak of cosmic galaxy/star formation (z ∼ 1–3) have become available. This rapid progress has been possible due to the advent of powerful ground- and space-based telescopes for the combined study of several millimeter to far-IR, line or continuum tracers of the molecular gas and dust components. The main conclusions of this review are as follows: Star-forming galaxies contained much more molecular gas at earlier cosmic epochs than at the present time. The galaxy-integrated depletion timescale for converting the gas into stars depends primarily on z or Hubble time and, at a given z, on the vertical location of a galaxy along the star-formation rate versus stellar mass main sequence (MS) correlation. Global rates of galaxy gas accretion primarily control the evolution of the cold molecular gas content and star-formation rates of the dominant MS galaxy population, which in turn vary with cosmological expansion. Another key driver may be global disk fragmentation in high-z, gas-rich galaxies, which ties local free-fall timescales to galactic orbital times and leads to rapid radial matter transport and bulge growth. The low star-formation efficiency inside molecular clouds is plausibly set by supersonic streaming motions and internal turbulence, which in turn may be driven by conversion of gravitational energy at high z and/or by local feedback from massive stars at low z. A simple gas regulator model is remarkably successful in predicting the combined evolution of molecular gas fractions, star-formation rates, galactic winds, and gas-phase metallicities. [ABSTRACT FROM AUTHOR]

We use spectra from the ALFALFA, GASS and COLD GASS surveys to quantify variations in the mean atomic and molecular gas mass fractions throughout the SFR-M* plane and along the main sequence (MS) of star-forming galaxies. Although galaxies well below the MS tend to be undetected in the Arecibo and IRAM observations, reliable mean atomic and molecular gas fractions can be obtained through a spectral stacking technique. We find that the position of galaxies in the SFR-M* plane can be explained mostly by their global cold gas reservoirs as observed in the H I line, with in addition systematic variations in the molecular-to-atomic ratio and star formation efficiency. When looking at galaxies within ±0.4 dex of the MS, we find that as stellar mass increases, both atomic and molecular gas mass fractions decrease, stellar bulges become more prominent, and the mean stellar ages increase. Both star formation efficiency and molecular-to-atomic ratios vary little for massive MS galaxies, indicating that the flattening of the MS is due to the global decrease of the cold gas reservoirs of galaxies rather than to bottlenecks in the process of converting cold atomic gas to stars. [ABSTRACT FROM AUTHOR]

We present multiline CO observations of the complex submillimeter galaxy SMM J00266+1708. Using the Zpectrometer on the Green Bank Telescope, we provide the first precise spectroscopic measurement of its redshift (z=2.742). Based on followup CO(1-0), CO(3-2), and CO(5-4) mapping, SMM J00266+1708 appears to have two distinct components separated by ~500 km/s that are nearly coincident along our line of sight. The two components show hints of different kinematics, with the blue-shifted component dispersion-dominated and the red-shifted component showing a clear velocity gradient. CO line ratios differ slightly between the two components, indicating that the physical conditions in their molecular gas may not be alike. We tentatively infer that SMM J00266+1708 is an ongoing merger with a mass ratio of (7.8 ± -4.0)/sin²(i), with its overall size and surface brightness closely resembling that of other merging systems. We perform large velocity gradient modeling of the CO emission from both components and find that each component's properties are consistent with a single phase of molecular gas (i.e., a single temperatures and density); additional multi-phase modeling of the red-shifted component, although motivated by a CO(1-0) size larger than the CO(3-2) size, is inconclusive. SMM J00266+1708 provides evidence of early stage mergers within the submillimeter galaxy population. Continuum observations of J00266 at the ~1" resolution of our observations could not have distinguished between the two components due to their separation (0.73" +/- 0.06"), illustrating that the additional velocity information provided by spectral line studies is important for addressing the prevalence of unresolved galaxy pairs in low-resolution submillimeter surveys. [ABSTRACT FROM AUTHOR]

We explore the nature of the long-wavelength mid-infrared (MIR) emission of a sample of 13,000 local Type II (narrow-line) active galactic nuclei (AGNs) from the Sloan Digital Sky Survey (SDSS) using 12 μm and 22 μm photometry from the WISE all-sky survey. In combination with FIRST 1.4 GHz photometry, we show that AGNs divide into two relatively distinct populations or “branches” in the plane of MIR and radio luminosity. Seyfert galaxies lie almost exclusively on an MIR-bright branch (Branch A), while low-ionization nuclear emission line galaxies (LINERs) are split evenly into Branch A and the MIR-faint Branch B. We devise various tests to constrain the processes that define the branches, including a comparison to the properties of pure star-forming inactive galaxies on the MIR-radio plane. We demonstrate that the total MIR emission of objects on Branch A, including most Seyfert galaxies, is governed primarily by host star formation, with ≈15% of the 22 μm luminosity coming from AGN-heated dust. This implies that ongoing dusty star formation is a general property of Seyfert host galaxies. We show that the 12 μm broadband luminosity of AGNs on Branch A is suppressed with respect to star-forming galaxies, possibly due to the destruction of PAHs or deeper 10 μm Si absorption in AGNs. We uncover a correlation between the MIR luminosity and [O III] λ5007 luminosity in AGNs. This suggests a relationship between the star formation rate and nuclear luminosity in the AGN population, but we caution on the importance of selection effects inherent to such AGN-dominated emission-line galaxies in driving such a correlation. We highlight the MIR-radio plane as a useful tool in comparative studies of star formation and nuclear activity in AGNs. [ABSTRACT FROM AUTHOR]

We combine IRAM Plateau de Bure Interferometer and Herschel PACS and SPIRE measurements to study the dust and gas contents of high-redshift star-forming galaxies. We present new observations for a sample of 17 lensed galaxies at z = 1.4-3.1, which allow us to directly probe the cold interstellar medium of normal star-forming galaxies with stellar masses of ∼1010M☼, a regime otherwise not (yet) accessible by individual detections in Herschel and molecular gas studies. The lensed galaxies are combined with reference samples of submillimeter and normal z ∼ 1-2 star-forming galaxies with similar far-infrared photometry to study the gas and dust properties of galaxies in the SFR-M*-redshift parameter space. The mean gas depletion timescale of main-sequence (MS) galaxies at z > 2 is measured to be only ∼450 Myr, a factor of ∼1.5 (∼5) shorter than at z = 1 (z = 0), in agreement with a (1 + z)–1 scaling. The mean gas mass fraction at z = 2.8 is 40% ± 15% (44% after incompleteness correction), suggesting a flattening or even a reversal of the trend of increasing gas fractions with redshift recently observed up to z ∼ 2. The depletion timescale and gas fractions of the z > 2 normal star-forming galaxies can be explained under the “equilibrium model” for galaxy evolution, in which the gas reservoir of galaxies is the primary driver of the redshift evolution of specific star formation rates. Due to their high star formation efficiencies and low metallicities, the z > 2 lensed galaxies have warm dust despite being located on the star formation MS. At fixed metallicity, they also have a gas-to-dust ratio 1.7 times larger than observed locally when using the same standard techniques, suggesting that applying the local calibration of the δGDR-metallicity relation to infer the molecular gas mass of high-redshift galaxies may lead to systematic differences with CO-based estimates. [ABSTRACT FROM AUTHOR]

We present F110W (~J ) and F160W (~H) observations of 10 submillimeter galaxies (SMGs) obtained with the Hubble Space Telescope's (HST's)NICMOS camera. Our targets have optical redshifts in the range 2.20 ⩽ z ⩽ 2.81 confirmed by millimeter CO or mid-IR spectroscopy, guaranteeing that the two bands sample the rest-frame optical with the Balmer break falling between them. Eight of ten are detected in both bands, while two are detected in F160W only. We study their F160W morphologies, applying a maximum-deblending detection algorithm to distinguish multiple- from single-component configurations, leading to reassessments for several objects. Based on our NICMOS imaging and/or previous dynamical evidence we identify five SMGs as multiple sources, which we interpret as merging systems. Additionally, we calculate morphological parameter asymmetry (A) and the Gini coefficient (G); thanks to our sample's limited redshift range we recover the trend that multiple-component, mergerlike morphologies are reflected in higher asymmetries. We analyze the stellar populations of nine objects with F110W/F160W photometry, using archival HST optical data when available. For multiple systems, we are able to model the individual components that build up an SMG.With the available data we cannot discriminate among star formation histories, but we constrain stellar masses and mass ratios for merger-like SMG systems, obtaining a mean log(M"/M☉) = 10.9±0.2 for our full sample, with individual values log(M"/M☉) ~ 9.6-11.8. The morphologies and mass ratios of the least and most massive systems match the predictions of the major-merger and cold accretion SMG formation scenarios, respectively, suggesting that both channels may have a role in the population's origin. [ABSTRACT FROM AUTHOR]

ABSTRACT We analyse the role of bars in the build-up of central mass concentrations in massive, disc galaxies. Our parent sample consists of 3757 face-on disc galaxies with redshifts between 0.01 and 0.05, selected from the seventh Data Release of the Sloan Digital Sky Survey. 1555 galaxies with bars are identified using the position angle and ellipticity profiles of the i-band light. We compare the ratio of the specific star formation rate measured in the 1-3 kpc central region of the galaxy to that measured for the whole galaxy. Galaxies with strong bars have centrally enhanced star formation; the degree of enhancement depends primarily on the ellipticity of the bar and not on the size of the bar or on the mass or structure of the host galaxy. The fraction of galaxies with strong bars is highest at stellar masses greater than 3 × 1010 M⊙, stellar surface densities less than 3 × 108 M⊙ and concentration indices less than 2.5. In this region of parameter space, galaxies with strong bars either have enhanced central star formation rates, or star formation that is suppressed compared to the mean. This suggests that bars may play a role in the eventual quenching of star formation in galaxies. Only 50 per cent of galaxies with strongly concentrated star formation have strong bars, indicating that other processes such as galaxy interactions also induce central starbursts. We also find that the ratio of the size of the bar to that of the disc depends mainly on the colour of the galaxy, suggesting that the growth and destruction of bars are regulated by gas accretion, as suggested by simulations. [ABSTRACT FROM AUTHOR]

ABSTRACT We compare the semi-analytic models of galaxy formation of Fu et al. which track the evolution of the radial profiles of atomic and molecular gas in galaxies, with gas fraction scaling relations derived from a stellar mass-limited sample of 299 galaxies from the CO Legacy Database for GASS. These galaxies have measurements of the CO(1-0) line from the IRAM 30-m telescope and the H i line from Arecibo, as well as measurements of star formation rates, stellar masses, galaxy sizes and concentration parameters from GALEX+SDSS photometry. The models provide a good description of how condensed baryons in star-forming galaxies are partitioned into atomic and molecular gas and stars as a function of galaxy stellar mass and stellar surface density. The models do not reproduce the observed tight relation between stellar surface mass density and bulge-to-disc ratio in these galaxies. The current implementation of 'radio-mode feedback' in the models produces trends that disagree strongly with the data. In the models, gas cooling shuts down in nearly all galaxies in dark matter haloes above a mass of ∼1012 M⊙. As a result, stellar mass is the observable that best predicts whether a galaxy has little or no neutral gas, that is, whether a galaxy has been quenched. In contrast, our data show that quenching is largely independent of stellar mass. Instead, there are clear thresholds in bulge-to-disc ratio and in stellar surface density that demarcate the location of quenched galaxies in our chosen parameter space. We speculate that the disagreement between the models and the observations may be resolved if radial transport of gas from the outer disc is included as an additional bulge formation mechanism in the models. In addition, we propose that processes associated with bulge formation play a key role in depleting the neutral gas in galaxies and that gas accretion is suppressed in a significant fraction of galaxies following the formation of the bulge, even in dark matter haloes of low mass. [ABSTRACT FROM AUTHOR]

The membership of Commission 28 is so large, and the spread of research interests so broad, that the research highlights presented here of necessity represent just a small subset of the work carried out over the past three years. Progress in the area of galaxy evolution continues to be particularly rapid, driven by both the availability of new multi-wavelength survey data and the development of increasingly sophisticated simulations to model the complex behaviour of stars and gas (e.g. Agertz et al. 2011; Guo et al. 2011; Keres et al. 2009; Schaye et al. 2010). [ABSTRACT FROM PUBLISHER]

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We present results from infrared spectroscopic projects that aim to test the relation between the mass of a black hole MBH and the velocity dispersion of the stars in its host-galaxy bulge. We demonstrate that near-infrared, high-resolution spectroscopy assisted by adaptive optics is key in populating the high-luminosity end of the relation. We show that the velocity dispersions of mid-infrared, high-ionization lines originating from gas in the narrow-line region of the active galactic nucleus follow the same relation. This result provides a way of inferring MBH estimates for the cosmologically significant population of obscured, type 2 AGN that can be applicable to data from spectrographs on next-generation infrared telescopes. [ABSTRACT FROM PUBLISHER]

Using atomic and molecular gas observations from the GASS and COLD GASS surveys and complementary optical/UV data from the Sloan Digital Sky Survey and the Galaxy Evolution Explorer, we investigate the nature of the variations in the molecular gas depletion time observed across the local massive galaxy population. The large and unbiased COLD GASS sample allows us for the first time to statistically assess the relative importance of galaxy interactions, bar instabilities, morphologies, and the presence of active galactic nuclei (AGNs) in regulating star formation efficiency. We find that both the H2 mass fraction and depletion time vary as a function of the distance of a galaxy from the main sequence traced by star-forming galaxies in the SFR-M* plane. The longest gas depletion times are found in below-main-sequence bulge-dominated galaxies (μ* >5 × 108M☼ kpc–2, C > 2.6) that are either gas-poor (/M* <1.5%) or else on average less efficient by a factor of ∼2 than disk-dominated galaxies at converting into stars any cold gas they may have. We find no link between the presence of AGNs and these long depletion times. In the regime where galaxies are disk-dominated and gas-rich, the galaxies undergoing mergers or showing signs of morphological disruptions have the shortest molecular gas depletion times, while those hosting strong stellar bars have only marginally higher global star formation efficiencies as compared to matched control samples. Our interpretation is that the molecular gas depletion time variations are caused by changes in the ratio between the gas mass traced by the CO(1-0) observations and the gas mass in high-density star-forming cores (as traced by observations of, e.g., HCN(1-0)). While interactions, mergers, and bar instabilities can locally increase pressure and raise the ratio of efficiently star-forming gas to CO-detected gas (therefore lowering the CO-based depletion time), massive bulges may prevent the formation of dense clumps by stabilizing gas disks against fragmentation, therefore producing the long depletion times. Building a sample representative of the local galaxy population with M* >1010M☼, we derive a global Kennicutt-Schmidt star formation relation of slope 1.18 ± 0.24 and observe structure within the scatter around this relation, with galaxies having low (high) stellar mass surface densities lying systematically above (below) the mean relation, suggesting that is not the only parameter driving the global star formation ability of a galaxy. [ABSTRACT FROM AUTHOR]

Previous studies of the molecular gas excitation in high-redshift galaxies have focused on galaxy-wide averages of CO line ratios. However, it is possible that these averages hide spatial variation on sub-galactic scales, disguising the true distribution and conditions of the molecular gas within star-forming galaxies. Even in the pre-ALMA era we have begun to see evidence for spatial variation of CO excitation in both rest-UV selected and submillimeter-selected galaxies at z > 2, aided both by the increased frequency coverage of the Jansky Very Large Array (allowing high-resolution observations of the CO(1–0) line, the best tracer for the coldest molecular gas) and by the benefits of gravitational lensing for spatially extended sources. We show new results for multiple high-redshift systems that reveal spatial and/or spectral variations in CO excitation, including an early-stage merger that has different conditions in its two components, thereby illustrating the need for high spatial and spectral resolution mapping in order to accurately characterize the molecular ISM in high-z galaxies. [ABSTRACT FROM PUBLISHER]

We have obtained high-resolution data of the z ∼ 2 ring-like, clumpy star-forming galaxy (SFG) ZC406690 using the VLT/SINFONI with adaptive optics (in K band) and in seeing-limited mode (in H and J bands). Our data include all of the main strong optical emission lines: [O II], [O III], Hα, Hβ, [N II], and [S II]. We find broad, blueshifted Hα and [O III] emission line wings in the spectra of the galaxy's massive, star-forming clumps (σ ∼ 85 km s–1) and even broader wings (up to 70% of the total Hα flux, with σ ∼ 290 km s–1) in regions spatially offset from the clumps by ∼2 kpc. The broad emission likely originates from large-scale outflows with mass outflow rates from individual clumps that are 1-8× the star formation rate (SFR) of the clumps. Based on emission line ratio diagnostics ([N II]/Hα and [S II]/Hα) and photoionization and shock models, we find that the emission from the clumps is due to a combination of photoionization from the star-forming regions and shocks generated in the outflowing component, with 5%-30% of the emission deriving from shocks. In terms of the ionization parameter (6 × 107 to 108 cm s–1, based on both the SFR and the O32 ratio), density (local electron densities of 300-1800 cm–3 in and around the clumps, and ionized gas column densities of 1200-8000 M☼pc–2), and SFR (10-40 M☼ yr–1), these clumps more closely resemble nuclear starburst regions of local ultraluminous infrared galaxies and dwarf irregulars than H II regions in local galaxies. However, the star-forming clumps are not located in the nucleus as in local starburst galaxies but instead are situated in a ring several kpc from the center of their high-redshift host galaxy, and have an overall disk-like morphology. The two brightest clumps are quite different in terms of their internal properties, energetics, and relative ages, and thus we are given a glimpse at two different stages in the formation and evolution of rapidly star-forming giant clumps at high-z. [ABSTRACT FROM AUTHOR]