Emission-line Gas Research Articles

Mass Loss from Evolved Stars in Elliptical Galaxies

Most of the X-ray emitting gas in early-type galaxies probably originates from red giant mass loss and here we model the interaction between this stellar mass loss and the hot ambient medium. Using two-dimensional hydrodynamic simulations, we adopt a temperature for the ambient medium of 3E6 K along with a range of ambient densities and stellar velocities. When the stellar velocity is supersonic relative to the ambient medium, a bow shock occurs, along with a shock driven into the stellar ejecta, which heats only a fraction of the gas. Behind the bow shock, a cool wake develops but the fast flow of the hot medium causes Kelvin-Helmholtz instabilities to grow and these fingers are shocked and heated (without radiative cooling). Along with the mixing of this wake material with the hot medium, most of the stellar ejecta is heated to approximately the temperature of the hot ambient medium within 2 pc of the star. With the addition of radiative cooling, some wake material remains cool (< 1E5 K), accounting for up to 25% of the stellar mass loss. Less cooled gas survives when the ambient density is lower or when the stellar velocity is higher than in our reference case. These results suggest that some cooled gas should be present in the inner part of early-type galaxies that have a hot ambient medium. These calculations may explain the observed distributed optical emission line gas as well as the presence of dust in early-type galaxies.

Enormous disc of cool gas surrounding the nearby powerful radio galaxy NGC 612 (PKS 0131−36)

We present the detection of an enormous disc of cool neutral hydrogen (H i) gas surrounding the S0 galaxy NGC 612, which hosts one of the nearest powerful radio sources (PKS 0131−36). Using the Australia Telescope Compact Array, we detectMH i= 1.8 × 109M⊙ of H i emission-line gas that is distributed in a 140-kpc wide disc-like structure along the optical disc and dust lane of NGC 612. The bulk of the gas in the disc appears to be settled in regular rotation with a total velocity range of 850 km s−1, although asymmetries in this disc indicate that perturbations are being exerted on part of the gas, possibly by a number of nearby companions. The H i disc in NGC 612 suggests that the total mass enclosed by the system isMenc≈ 2.9 × 1012 sin−2i M⊙, implying that this early-type galaxy contains a massive dark matter halo. We also discuss an earlier study by Holt et al. that revealed the presence of a prominent young stellar population at various locations throughout the disc of NGC 612, indicating that this is a rare example of an extended radio source that is hosted by a galaxy with a large-scale star-forming disc. In addition, we map a faint H i bridge along a distance of 400 kpc in between NGC 612 and the gas-rich (MH i= 8.9 × 109M⊙) barred galaxy NGC 619, indicating that likely an interaction between both systems occurred. From the unusual amounts of H i gas and young stars in this early-type galaxy, in combination with the detection of a faint optical shell and the system's high infrared luminosity, we argue that either ongoing or past galaxy interactions or a major merger event are a likely mechanism for the triggering of the radio source in NGC 612. This paper is part of an ongoing study to map the large-scale neutral hydrogen properties of nearby radio galaxies and it presents the first example of large-scale H i detected around a powerful Fanaroff–Riley type II (FR-II) radio galaxy. The H i properties of the FR-II radio galaxy NGC 612 are very similar to those found for low-power compact radio sources, but different from those of extended Fanaroff–Riley type I (FR-I) sources.

WFPC2 LRF Imaging of Emission‐Line Nebulae in 3CR Radio Galaxies

We present Hubble Space Telescope WFPC2 Linear Ramp Filter images of high surface brightness emission lines (either [O II], [O III], or H alpha + [N II]) in 80 3CR radio sources. We overlay the emission-line images on high-resolution VLA radio images (eight of which are new reductions of archival data) in order to examine the spatial relationship between the optical and radio emission. We confirm that the radio and optical emission-line structures are consistent with weak alignment at low redshift (z < 0.6) except in the compact steep-spectrum (CSS) radio galaxies where both the radio source and the emission-line nebulae are on galactic scales and strong alignment is seen at all redshifts. There are weak trends for the aligned emission-line nebulae to be more luminous and for the emission-line nebula size to increase with redshift and/or radio power. The combination of these results suggests that there is a limited but real capacity for the radio source to influence the properties of the emission-line nebulae at these low redshifts (z < 0.6). Our results are consistent with previous suggestions that both mechanical and radiant energy are responsible for generating alignment between the radio source and emission-line gas.

Probing the Ionization Structure of the Narrow‐Line Region in the Seyfert 1 Galaxy NGC 4151

We present a study of the distribution of [O III] λ5007 and [O II] λ3727 emission in the narrow-line region (NLR) of the Seyfert 1 galaxy NGC 4151. While the NLR of NGC 4151 exhibits an overall structure consistent with the unified model of Seyfert galaxies, narrowband [O III] and [O II] images obtained with the Wide Field and Planetary Camera 2 aboard the Hubble Space Telescope reveal significant emission from outside the emission-line bicone. The [O III]/[O II] ratios are lower in these regions, consistent with a weaker ionizing flux. We performed a photoionization modeling analysis of the emission-line gas within a series of annuli, centered on the central continuum source, with inner radii from 13 to 90 pc. The gas is ionized by radiation that has been attenuated by a relatively highly ionized absorber (HABS), which completely covers the central source, and a lower ionization absorber (LABS), which has a covering factor ranging from 0 to 1. We found that the [O III]/[O II] ratios are well fit by assuming that, within each segment of an annulus, some fraction of the NLR gas is completely within the shadow of LABS, while the rest is irradiated by the continuum filtered only by HABS. This suggests that the structure of the NLR is due to filtering of the ionizing radiation by ionized gas, consistent with disk-wind models. One possible scenario is that the low-ionization absorbers are dense knots of gas swept up by a wind.

Fast outflows in compact radio sources: evidence for AGN-induced feedback in the early stages of radio source evolution

We present intermediate-resolution, wide-wavelength coverage spectra for a complete sample of 14 compact radio sources taken with the aim of investigating the impact of the nuclear activity on the circumnuclear interstellar medium (ISM) in the early stages of radio source evolution. We observe spatially extended line emission (up to ∼20 kpc) in the majority of sources which is consistent with a quiescent halo. In the nuclear apertures we observe broad, highly complex emission-line profiles. Multiple Gaussian modelling of the [O iii]λ5007 line reveals between two and four components which can have velocity widths [full width at half-maximum (FWHM)] and blueshifts relative to the halo of up to ∼2000 km s−1. We interpret these broad, blueshifted components as material in outflow and discuss the kinematical evidence for jet-driven outflows as previously proposed for PKS 1549−79 and PKS 1345+12. Comparisons with samples in the literature show that compact radio sources harbour more extreme nuclear kinematics than their extended counterparts, a trend seen within our sample with larger velocities in the smaller sources. The observed velocities are also likely to be influenced by source orientation with respect to the observer's line of sight. Nine sources have associated H i absorption. In common with the optical emission-line gas, the H i profiles are often highly complex with the majority of the detected components significantly blueshifted, tracing outflows in the neutral gas. The sample has been tested for stratification in the ISM (FWHM/ionization potential/critical density) as suggested by Holt, Tadhunter & Morganti for PKS 1345+12 but we find no significant trends within the sample using a Spearman rank analysis. This study supports the idea that compact radio sources are young radio-loud active galactic nuclei observed during the early stages of their evolution and currently shedding their natal cocoons through extreme circumnuclear outflows.

Low‐Ionization Emission Regions in Quasars: Gas Properties Probed with Broad Oiand CaiiLines

We have compiled the emission-line fluxes of O I λ8446, O I λ11287, and the near-infrared (IR) Ca II triplet (λ8579) observed in 11 quasars. These lines are considered to emerge from the same gas as do the Fe II lines in the low-ionized portion of the broad emission line region (BELR). The compiled quasars are distributed over wide ranges of redshift (0.06 ⩽ z⩽ 1.08) and of luminosity (–29.8 ⩽ MB ⩽ − 22.1), thus providing a useful sample to investigate the line-emitting gas properties in various quasar environments. The measured line strengths and velocities, as functions of the quasar properties, are analyzed using photoionization model calculations. We found that the flux ratio between the Ca II triplet and O I λ8446 is hardly dependent on the redshift or luminosity, indicating similar gas densities in the emission region from quasar to quasar. On the other hand, a scatter of the O I λ11287/λ8446 ratios appears to imply the diversity of the ionization parameter. These facts invoke a picture of the line-emitting gases in quasars that have similar densities and are located at regions exposed to various ionizing radiation fluxes. The observed O I line widths are found to be remarkably similar over more than 3 orders of magnitude in luminosity, which indicates a kinematically determined location of the emission region and is in clear contrast to the case of H I lines. We also argue about the dust presence in the emission region since the region is suggested to be located near the dust sublimation point at the outer edge of the BELR.

A SINFONI VIEW OF GALAXY CENTERS: MORPHOLOGY AND KINEMATICS OF FIVE NUCLEAR STAR-FORMATION RINGS

We present near-infrared (H- and K-band) integral-field observations of the circumnuclear star formation rings in five nearby spiral galaxies. The data, obtained at the Very Large Telescope with the SINFONI spectrograph, are used to construct maps of various emission lines that reveal the individual star forming regions (hot spots) delineating the rings. We derive the morphological parameters of the rings, and construct velocity fields of the stars and the emission line gas. We propose a qualitative, but robust, diagnostic for relative hot spot ages based on the intensity ratios of the emission lines Brγ, He I, and [Fe II]. Application of this diagnostic to the data presented here provides tentative support for a scenario in which star formation in the rings is triggered predominantly at two well-defined regions close to, and downstream from, the intersection of dust lanes along the bar with the inner Lindblad resonance.

Compact radio sources and jet-driven AGN feedback in the early universe: constraints from integral-field spectroscopy

To investigate the impact of radio jets during the formation epoch of their massive host galaxies, we present an analysis of two massive, log M{sub stellar}/M{sub {circle_dot}} {approx} 10.6 and 11.3, compact radio galaxies at z = 3.5, TNJ0205+2242 and TNJ0121+1320. Their small radio sizes (R {le} 10 kpc) are most likely a sign of youth. In particular, we compare their radio properties and gas dynamics with those in well extended radio galaxies at high redshift, which show strong evidence for powerful, jet-driven outflows of significant gas masses (M {approx} 10{sup 9-10} M{sub {circle_dot}}). Our analysis combines rest-frame optical integral-field spectroscopy obtained with SINFONI on the VLT with existing radio imaging, CO(4-3) emission line spectra, and rest-frame UV longslit spectroscopy. [OIII]{lambda}5007 line emission is compact in both galaxies and lies within the region defined by the radio lobes. For TNJ0205+2242, the Ly{alpha} profile narrows significantly outside the jet radius, indicating the presence of a quiescent halo. TNJ0121+1320 has two components at a projected relative distance of {approx}10 kpc and a velocity offset of {approx}300 km s{sup -1}, measured from the [OIII]{lambda}5007 velocity map. This suggests that the fainter component is orbiting around the more massive, radio-loud galaxy. If motions aremore » gravitational, this implies a dynamical mass of 2 x 10{sup 11} M{sub {circle_dot}} for the radio-loud component. The dynamical mass, molecular gas mass measured from the CO line emission, and radio luminosity of these two compact radio galaxies imply that compact radio sources may well develop large-scale, energetic outflows as observed in extended radio galaxies, with the potential of removing significant fractions of the ISM from the host galaxy. The absence of luminous emission line gas extending beyond the radio emission in these sources agrees with the observed timescales and outflow rates in extended radio galaxies, and adds further evidence that the energetic, large-scale outflows observed in extended radio sources (Nesvadba et al. 2006) are indeed the result of influence of the radio jet.« less

Fields and filaments in the core of the Centaurus cluster

We present high resolution images of the Faraday Rotation Measure (RM) structure of the radio galaxy PKS 1246-410, at the center of the Centaurus cluster. Comparison with Halpha-line and soft X-ray emission reveals a correspondence between the line-emitting gas, the soft X-ray emitting gas, regions with an excess in the RM images, and signs of depolarization. Magnetic field strengths of 25 microG, organized on scales of ~1 kpc, and intermixed with gas at a temperature of 5 x 10^6 K with a density of ~0.1 cm^-3 can reproduce the observed RM excess, the depolarization, and the observed X-ray surface brightness. This hot gas may be in pressure equilibrium with the optical line-emitting gas, but the magnetic field strength of 25 microG associated with the hot gas provides only 10% of the thermal pressure and is therefore insufficient to account for the stability of the line-emitting filaments.

Star formation and stellar populations across nuclear rings in galaxies

We present a study of the optical spectra of a sample of eight star-forming nuclear rings and the nuclei of their host galaxies. The spectra were obtained with the Intermediate dispersion Spectrograph and Imaging System spectrograph on the William Herschel Telescope and cover a wide range in wavelength, enabling the measurement of several stellar absorption features and gas emission lines. We compared the strength of the absorption lines to a variety of population synthesis models for the star formation history in the nuclear rings, including also the contribution of the older bulge and disc stellar components. In agreement with our previous investigation of the nuclear ring of NGC 4321, which was based on a more restricted number of line-strength indices, we find that the stars in our sample of nuclear rings have most likely formed over a prolonged period of time characterized by episodic bursts of star formation activity. Constant star formation is firmly ruled out by the present data, whereas a one-off formation event is an unlikely explanation for a common galactic component such as nuclear rings. The nuclear rings of NGC 4314 and NGC 7217 have distinct line-strength properties that set them apart from the rest of our sample, which are due to a larger contribution of bulge star in the observed spectra and, in the case of NGC 4314, to a younger stellar population in the ring. We have used emission-line measurements to constrain the physical conditions of the ionized gas within the rings, using the ratio of the [S II]λλ6716, 6731 lines to estimate the density of the gas, and photoionization model grids within specific diagnostic diagrams to derive metallicity. We find that emission in all nuclear rings originates from H II regions with electron densities typical for these kinds of objects, and that the rings are characterized by values for the gas metallicity ranging from slightly below to just above solar. We have also studied the spectra of the nuclei of our sample galaxies, all of which display emission lines. Consistent with previous studies for the nuclear activity and stellar populations, the majority of our nuclei appear to be dominated by old stellar populations and by Low-Ionization Nuclear Emission Region like emission. As 20 per cent of nearby spiral galaxies host nuclear rings that are presently forming massive stars, our finding of an episodic star formation history in nuclear rings implies that a significant population remains to be identified of young nuclear rings that are not presently in a massive star formation phase. Nuclear rings may thus be a much more common galactic component than presently known.

TheSuzakuObservation of the Nucleus of the Radio‐loud Active Galaxy Centaurus A: Constraints on Abundances of the Accreting Material

A Suzaku observation of the nucleus of the radio-loud AGN Centaurus A in 2005 has yielded a broadband spectrum spanning 0.3 to 250 keV. The hard X-rays are fit by two power laws, absorbed by columns of 1.5 and 7 x 10(exp 23) per square centimeter. The dual power-laws are consistent with previous suggestions that the powerlaw components are X-ray emission from the sub-pc VLBI jet and from Bondi accretion at the core, or are consistent with a partial covering interpretation. The soft band is dominated by thermal emission from the diffuse plasma and is fit well by a two-temperature VAPEC model, plus a third power-law component to account for scattered nuclear emission, kpc-scale jet emission, and emission from X-ray Binaries and other point sources. Narrow fluorescent emission lines from Fe, Si, S, Ar, Ca and Ni are detected. The width of the Fe Ka line yields a 200 light-day lower limit on the distance from the black hole to the line-emitting gas. K-shell absorption edges due to Fe, Ca, and S are detected. Elemental abundances are constrained via the fluorescent lines strengths, absorption edge depths and the diffuse plasma emission lines. The high metallicity ([Fe/H]=+0.l) of the circumnuclear material compared to that in the metal-poor outer halo suggests that the accreting material could not have originated in the outer halo unless enrichment by local star formation has occurred. Relative abundances are consistent with enrichment from Type II and Ia supernovae.

Emission‐Line Gas Kinematics in the Vicinity of the Supermassive Black Holes in Nearby Radio Galaxies

We describe our characterization of the kinematics of the emission-line gas in the nuclear regions of a complete sample of 21 nearby radio galaxies. We obtained data using the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. We show that the point-to-point variations are largest perpendicular to the disks and in nuclei where the organized motion is less pronounced, suggesting that motions are present from gas that has not settled into smooth rotation. We show that the velocity dispersion is not distributed as a function of inclination, and so likely arises from isotropic random motions in the gas. We find that the difference in mean velocities on either side of the nucleus does not vanish as the disks become face-on, suggesting there may be bulk motions of the gas disks. We show that the gas velocity dispersions are closely related to the stellar velocity dispersions, which has implications for black hole fueling and growth mechanisms. We show that significant motions digressing from a smooth thin disk configuration are ubiquitous, and even in those cases where the velocity profile of the emission-line gas appears smooth and uncomplicated there may be dynamical components of the system that are not explained by a thin Keplerian disk model, suggesting caution in the use of gas disk kinematics for the determination of black hole masses.

On the Effects of Dissipative Turbulence on the Narrow Emission‐Line Ratios in Seyfert Galaxies

We present a photoionization model study of the effects of microturbulence and dissipative heating on emission lines for number and column densities, elemental abundances, and ionizations typical for the narrow emission line regions (NLRs) of Seyfert galaxies. Earlier studies of NLR spectra generally found good agreement between the observations and the model predictions for most strong emission lines, such as [O III] λ5007, [O II] λ3727, [N II] λ6583, [Ne III] λ3869, and the H and He recombination lines. Nevertheless, the strengths of lines from species with ionization potentials greater than that of He+ (54.4 eV), e.g., N+4 and Ne+4, were often underpredicted. Among the explanations suggested for these discrepancies were (selectively) enhanced elemental abundances and contributions from shock-heated gas. Interestingly, the NLR lines have widths of several 100 km s-1, well in excess of the thermal broadening. If this is due to microturbulence, and the turbulence dissipates within the emission-line gas, the gas can be heated in excess of that due to photoionization. We show that the combined effects of turbulence and dissipative heating can strongly enhance N V λ1240 (relative to He II λ1640), while the heating alone can boost the strength of [Ne V] λ3426. We suggest that this effect is present in the NLR, particularly within ~100 pc of the central engine. Finally, since microturbulence would make clouds robust against instabilities generated during acceleration, it is not likely to be a coincidence that the radially outflowing emission-line gas is turbulent.

Star Formation, Radio Sources, Cooling X-Ray Gas, and Galaxy Interactions in the Brightest Cluster Galaxy in 2A0335+096

We present deep emission-line imaging taken with the SOAR Optical Imaging Camera of the brightest cluster galaxy (BCG) in the nearby (z=0.035) X-ray cluster 2A0335+096. We analyze long-slit optical spectroscopy, archival VLA, Chandra X-ray, and XMM UV data. 2A0335+096 is a bright, cool-core X-ray cluster, once known as a cooling flow. Within the highly disturbed core revealed by Chandra X-ray observations, 2A0335+096 hosts a highly structured optical emission-line system. The redshift of the companion is within 100 km/s of the BCG and has certainly interacted with the BCG, and is likely bound to it. The comparison of optical and radio images shows curved filaments in H-alpha emission surrounding the resolved radio source. The velocity structure of the emission-line bar between the BCG nucleus and the companion galaxy provides strong evidence for an interaction between the two in the last ~50 Myrs. The age of the radio source is similar to the interaction time, so this interaction may have provoked an episode of radio activity. We estimate a star formation rate of >7 solar mass/yr based on the Halpha and archival UV data, a rate similar to, but somewhat lower than, the revised X-ray cooling rate of 10-30 solar masses/year estimated from XMM spectra by Peterson & workers. The Halpha nebula is limited to a region of high X-ray surface brightness and cool X-ray temperature. The detailed structures of H-alpha and X-ray gas differ. The peak of the X-ray emission is not the peak of H-alpha emission, nor does it lie in the BCG. The estimated age of the radio lobes and their interaction with the optical emission-line gas, the estimated timescale for depletion and accumulation of cold gas, and the dynamical time in the system are all similar, suggesting a common trigger mechanism.

Intense Mechanoluminescence and Gas Phase Reactions from the Sonication of an Organic Slurry

Mechanoluminescence is typically produced by grinding, crushing, or scraping a crystal, which can give a faint glow of light, and was first reported by Francis Bacon in 1605. This light is a microdischarge produced by the local separation of charged surfaces, resulting in a spectrum of gas line emission and the crystal itself. We have produced mechanoluminescence via a new route, using acoustic cavitation. Upon sonication of slurries of resorcinol in long chain alkanes, intense mechanoluminescence is observed, up to 1000-fold increase in intensity over grinding. We have observed extensive atomic and molecular emission lines that have not been previously reported for mechanoluminescence. In addition, we have evidence of gas phase reactions taking place during the mechanoluminescent event.

Intense Star Formation and Feedback at High Redshift: Spatially Resolved Properties of thez= 2.6 Submillimeter Galaxy SMM J14011+0252

We present a detailed analysis of the spatially resolved properties of the lensed submillimeter galaxy (SMG) SMM J14011+0252 at z = 2.56, combining deep near-infrared integral-field data obtained with SPIFFI on the VLT with other multiwavelength data sets. As previously discussed by other authors, the broad characteristics of SMM J14011+0252 in particular and submillimeter galaxies in general are in agreement with what is expected for the early evolution of local massive spheroidal galaxies. From continuum and line flux, velocity, and dispersion maps, we measure the kinematics, star formation rates, gas densities, and extinction for individual subcomponents. The star formation intensity is similar to low-redshift while the line fluxes and the dynamics of the emission line gas provide direct evidence for a starburst-driven wind with physical properties very similar to local superwinds. We also find circumstantial evidence for self-regulated star formation within J1. The relative velocity of the bluer companion J2 yields a dynamical mass estimate for J1 within ~20 kpc of Mdyn ~ 1 × 1011 M☉. The relative metallicity of J2 is 0.4 dex lower than in J1n/J1s, suggesting different star formation histories. Spectral energy distribution fitting of the continuum peak J1c confirms and substantiates previous suggestions that this component is a z = 0.25 interloper. When removing J1c, the stellar continuum and Hα line emission appear well aligned spatially in two individual components, J1n and J1s, and coincide with two kinematically distinct regions in the velocity map, which might well indicate a merging system. This highlights the close similarity between SMGs and ultraluminous infrared galaxies (ULIRGs), which are often merger-driven maximal starbursts, and suggests that the intrinsic mechanisms of star formation and related feedback are in fact similar to low-redshift strongly star-forming systems.

The Velocity Field of Quasar Broad Emission Line Gas

In this Letter, the broad emission line (BEL) profiles of superluminal quasars with apparent jet velocities, $\beta_{a}>10$, (ultraluminal QSOs, or ULQSOs hereafter) are studied as a diagnostic of the velocity field of the BEL emitting gas in quasars. The ULQSOs are useful because they satisfy a very strict kinematical constraint, their parsec scale jets must be propagating within $12^{\circ}$ of the line of sight. We know the orientation of these objects with great certainty. The large BEL FWHM, $\sim 3,000 \mathrm{km/s} - 6,000 \mathrm{km/s}$, in ULQSOs tend to indicate that the BEL gas has a larger component of axial velocity (either random or in a wind) along the jet direction than previously thought.

The Formation and Evolution of Planetary Systems: Placing Our Solar System in Context with Spitzer

ABSTRACTWe provide an overview of the Spitzer Legacy Program, Formation and Evolution of Planetary Systems, that was proposed in 2000, begun in 2001, and executed aboard the Spitzer Space Telescope between 2003 and 2006. This program exploits the sensitivity of Spitzer to carry out mid‐infrared spectrophotometric observations of solar‐type stars. With a sample of ∼328 stars ranging in age from ∼3 Myr to ∼3 Gyr, we trace the evolution of circumstellar gas and dust from primordial planet‐building stages in young circumstellar disks through to older collisionally generated debris disks. When completed, our program will help define the timescales over which terrestrial and gas giant planets are built, constrain the frequency of planetesimal collisions as a function of time, and establish the diversity of mature planetary architectures. In addition to the observational program, we have coordinated a concomitant theoretical effort aimed at understanding the dynamics of circumstellar dust with and without the effects of embedded planets, dust spectral energy distributions, and atomic and molecular gas line emission. Together with the observations, these efforts will provide an astronomical context for understanding whether our solar system—and its habitable planet—is a common or a rare circumstance. Additional information about the FEPS project can be found on the team Web site.

Formation and Evolution of Planetary Systems: Upper Limits to the Gas Mass in Disks around Sun‐like Stars

We have carried out a sensitive search for gas emission lines at IR and millimeter wavelengths for a sample of 15 young Sun-like stars selected from our dust disk survey with Spitzer. We have used mid-IR lines to trace the warm (300-100 K) gas in the inner disk and millimeter transitions of ^(12)CO to probe the cold (~20 K) outer disk. We report no gas line detections from our sample. Line flux upper limits are first converted to warm and cold gas mass limits using simple approximations allowing a direct comparison with values from the literature. We also present results from more sophisticated models following Gorti & Hollenbach that confirm and extend our simple analysis. These models show that the [S I] 25.23 μm line can set constraining limits on the gas surface density at the disk inner radius and traces disk regions up to a few AU. We find that none of the 15 systems have more than 0.04M_J of gas within a few AU from the disk inner radius for disk radii from 1 to ~40 AU. These gas mass upper limits even in the eight systems younger than ~30 Myr suggest that most of the gas is dispersed early. The gas mass upper limits in the 10-40 AU region, which is mainly traced by our CO data, are <2 M_⊕. If these systems are analogs of the solar system, they either have already formed Uranus- and Neptune-like planets or will not form them beyond 100 Myr. Finally, the gas surface density upper limits at 1 AU are smaller than 0.01% of the minimum mass solar nebula for most of the sources. If terrestrial planets form frequently and their orbits are circularized by gas, then circularization occurs early.

Extreme Gas Kinematics in thez = 2.2 Powerful Radio Galaxy MRC 1138−262: Evidence for Efficient Active Galactic Nucleus Feedback in the Early Universe?

To explain the properties of the most massive low-redshift galaxies and the shape of their mass function, recent models of galaxy evolution include strong AGN feedback to complement starburst-driven feedback in massive galaxies. Using the near-infrared integral-field spectrograph SPIFFI on the VLT, we searched for direct evidence for such feedback in the optical emission line gas around the z = 2.16 powerful radio galaxy MRC 1138-262, likely a massive galaxy in formation. The kiloparsec-scale kinematics, with FWHMs and relative velocities 2400 km s-1 and nearly spherical spatial distribution, do not resemble large-scale gravitational motion or starburst-driven winds. Order-of-magnitude timescale and energy arguments favor the AGN as the only plausible candidate to accelerate the gas, with a total energy injection of a few ?1060 ergs or more, necessary to power the outflow, and relatively efficient coupling between radio jet and ISM. Observed outflow properties are in gross agreement with the models and suggest that AGN winds might have a cosmological significance that is similar to, or perhaps larger than, starburst-driven winds if MRC 1138-262 is indeed archetypal. Moreover, the outflow has the potential to remove significant gas fractions (50%) from a >L* galaxy within a few tens to 100?Myr, fast enough to preserve the observed [?/Fe] overabundance in massive galaxies at low redshift. Using simple arguments, it appears that feedback like that observed in MRC 1138-262 may have sufficient energy to inhibit material from infalling into the dark matter halo and thus regulate galaxy growth as required in some recent models of hierarchical structure formation.