Multi-object Integral Field Spectrograph Research Articles

The SAMI galaxy survey: predicting kinematic morphology with logistic regression

ABSTRACT We use the SAMI (Sydney-AAO Multi-object Integral field spectrograph) galaxy survey to study the the kinematic morphology–density relation: the observation that the fraction of slow rotator galaxies increases towards dense environments. We build a logistic regression model to quantitatively study the dependence of kinematic morphology (whether a galaxy is a fast or slow rotator) on a wide range of parameters, without resorting to binning the data. Our model uses a combination of stellar mass, star formation rate (SFR), r-band half-light radius, and a binary variable based on whether the galaxy’s observed ellipticity (ϵ) is less than 0.4. We show that, at fixed mass, size, SFR, and ϵ, a galaxy’s local environmental surface density (log10(Σ5/Mpc−2)) gives no further information about whether a galaxy is a slow rotator, that is, the observed kinematic–morphology density relation can be entirely explained by the well-known correlations between environment and other quantities. We show how our model can be applied to different galaxy surveys to predict the fraction of slow rotators which would be observed and discuss its implications for the formation pathways of slow rotators.

AGN-driven outflows in the OH absorber galaxy IRAS 19154+2704

ABSTRACT We present a two-dimensional study of the gas distribution, excitation, and kinematics of the OH absorber galaxy IRAS 19154+2704 using Gemini Multi-Object Spectrograph integral field unit observations. Its continuum image shows a disturbed morphology indicative of a past or ongoing interaction. The ionized gas emission presents two kinematic components: a narrow (σ ≲ 300 km s−1) component that may be tracing the gas orbiting in the galaxy potential and a broad (σ ≳ 500 km s−1) component, which is produced by an active galactic nucleus (AGN)-driven outflow, with velocities reaching −500 km s−1, which may exceed the escape velocity of the galaxy. The emission-line ratios and Baldwin–Phillips–Terlevich diagrams confirm that the gas excitation in the inner ∼2 kpc is mainly due to the AGN, while in regions farther away, a contribution from star formation is observed. We estimate a mass-outflow rate of $\dot{M}_{\rm out}=4.0\pm 2.6$ M⊙ yr−1 at a distance of 850 pc from the nucleus. The corresponding outflow kinetic power, $\dot{E}_{\rm out} = (2.5\pm 1.6)\times 10^{42}$ erg s−1, is only 3 × 10−4 Lbol (the AGN luminosity), but the large mass-outflow rate, if kept for an ∼10 Myr AGN life cycle, will expel ≈108 M⊙ in ionized gas alone. This is the sixth of a series of papers in which we have investigated the kinematics of ultra-luminous infrared galaxies, most of which are interacting galaxies showing OH megamasers. IRAS 19154 shows the strongest signatures of an active AGN, supporting an evolutionary scenario: interactions trigger AGN that fully appears in the most advanced stages of the interaction.

Unraveling the Complex Structure of AGN-driven Outflows. VI. Strong Ionized Outflows in Type 1 AGNs and the Outflow Size–Luminosity Relation

We present spatially resolved gas kinematics, ionization, and energetics of 11 type 1 and 5 type 2 active galactic nuclei (AGNs) with strong ionized gas outflows at z <0.3 using Gemini Multi-Object Spectrograph Integral Field Unit data. We find a strongly blueshifted region in [O iii] velocity maps, representing an approaching cone in biconical outflows, and blueshifted and redshifted regions in Hα velocity maps, which show gravitationally rotating kinematics. AGN photoionization is dominant in the central region of most targets, and some of them also show ring-like structures of LINER or composite that surround the AGN-dominated center. Following our previous studies, we kinematically determine outflow sizes by the ratio between [O iii] and stellar velocity dispersion. Outflow sizes of type 1 AGNs follow the same kinematic outflow size–[O iii] luminosity relation obtained from the type 2 Integral Field Unit sample in Kang & Woo and Luo (updated slope 0.29 ± 0.04), while they are limited to the central kiloparsec scales, indicating the lack of global impact of outflows on the interstellar medium. Small mass outflow rates and large star formation rates of the combined sample support that there is no evidence of rapid star formation quenching by outflows, which is consistent with the delayed AGN feedback.

Beyond BPT: A New Multidimensional Diagnostic Diagram for Classifying Power Sources Tested Using the SAMI Galaxy Survey

Current methods of identifying the ionizing source of nebular emission in galaxies are well defined for the era of single-fiber spectroscopy, but still struggle to differentiate the complex and overlapping ionization sources in some galaxies. With the advent of integral field spectroscopy, the limits of these previous classification schemes are more apparent. We propose a new method for distinguishing the ionizing source in resolved galaxy spectra by use of a multidimensional diagnostic diagram that compares emission-line ratios with velocity dispersion on a spaxel-by-spaxel basis within a galaxy. This new method is tested using the Sydney-Australian-Astronomical-Observatory Multi-object Integral-Field Spectrograph Galaxy Survey (SAMI) Data Release 3 (DR3), which contains 3068 galaxies at z < 0.12. Our results are released as ionization maps available alongside the SAMI DR3 public data. Our method accounts for a more diverse range of ionization sources than the standard suite of emission-line diagnostics; we find 1433 galaxies with a significant contribution from non-star-forming ionization using our improved method as compared to 316 galaxies identified using only emission-line ratio diagnostics. Within these galaxies, we further identify 886 galaxies hosting unique signatures inconsistent with standard ionization by H ii regions, active galactic nuclei, or shocks. These galaxies span a wide range of masses and morphological types and comprise a sizable portion of the galaxies used in our sample. With our revised method, we show that emission-line diagnostics alone do not adequately differentiate the multiple ways to ionize gas within a galaxy.

Spatially resolved mock observations of stellar kinematics: full radiative transfer treatment of simulated galaxies

ABSTRACT We present a framework to build realistic mock spectroscopic observations for state-of-the-art hydrodynamical simulations, using high spectral resolution stellar population models and full radiative transfer treatment with skirt. As a first application, we generate stellar continuum mock observations for the Auriga cosmological zoom simulations emulating integral-field observations from the Sydney–AOO Multi-object Integral Field Spectrograph (SAMI) Galaxy Survey. We perform spectral fitting on our synthetic cubes and compute the resulting rotation velocity (Vrot) and velocity dispersion within 1Re (σe) for a subset of the Auriga sample. We find that the kinematics produced by Auriga are in good agreement with the observations from the SAMI galaxy survey after taking into account the effects of dust and the systematics produced by the observation limitations. We also explore the effects of seeing convolution, inclination, and attenuation on the line-of-sight velocity distribution. For highly inclined galaxies, these effects can lead to an artificial decrease in the measured V/σ by nearly a factor of two (after inclination correction). We also demonstrate the utility of our method for high-redshift galaxies by emulating spatially resolved continuum spectra from the Large Early Galaxy Census (LEGA-C) survey and, looking forward, the European Extremely Large Telescope (E-ELT) High Angular Resolution Monolithic Optical and Near-infrared Integral field spectrograph (HARMONI). Our framework represents a crucial link between the ground truth for stellar populations and kinematics in simulations and the observed stellar continuum observations at low and high redshift.

Witnessing a Transformation to Blue-cored Dwarf Early-type Galaxies in Filaments and the Cluster Outskirts: Gas-phase Abundances and Internal Kinematics Perspectives

The presence of transitional dwarf galaxies in filaments and cluster outskirts may be closely related to preprocessing in the filament; however, the underlying mechanism is not yet comprehensively understood. We present the spatially resolved chemical and kinematical properties of three blue-cored dwarf early-type galaxies (dE(bc)s) in the Virgo cluster and Virgo-related filaments (Crater and Virgo III) using the Sydney-AAO Multi-object Integral-field spectrograph galaxy Survey. We map the spatial distribution of Hα, oxygen abundance (O/H), nitrogen-to-oxygen abundance ratio (N/O), stellar population age, and gas-stellar internal kinematics. We find irregular shapes of enhanced star-forming regions from the centers to the outlying regions of blue cores in dE(bc)s. These regions are relatively metal poor compared with the surrounding regions, rendering the overall metallicity gradient of each galaxy positive. Furthermore, they exhibit higher N/O ratios at a given O/H relative to their surroundings, implying metal-poor gas infall by external processes. The equivalent width of the Hα emission line in metal-poor regions indicates young age of star formation, 6–8 Myr. The disturbed ionized gas velocity field, one of the most prominent features of galaxy mergers is also discovered in two dE(bc)s. We propose that a moderately dense filament environment is favorable for the formation of blue cores in dEs, in which dE(bc)s in filaments may have already been transformed before they fall into the Virgo cluster. This process may contribute to the composition of galaxy population at the outskirts of the cluster.

Age-divided mean stellar populations from full spectrum fitting as the simplified star formation and chemical evolution history of a galaxy: methodology and reliability

ABSTRACT We introduce a practical methodology for investigating the star formation and chemical evolution history of a galaxy: age-divided mean stellar populations (ADPs) from full spectrum fitting. In this method, the mass-weighted mean stellar populations and mass fractions (fmass) of young and old stellar components in a galaxy are separately estimated, which are divided with an age cut (selected to be 109.5 yr ≈3.2 Gyr in this paper). To examine the statistical reliability of ADPs, we generate 10 000 artificial galaxy spectra, each of which consists of five random simple stellar population components. Using the Penalized PiXel-Fitting (ppxf) package, we conduct full spectrum fitting to the artificial spectra with noise as a function of wavelength, imitating the real noise of Sydney-Australian Astronomical Observatory Multi-object Integral field spectrograph (SAMI) galaxies. As a result, the Δ (= output − input) of age and metallicity appears to significantly depend on not only signal-to-noise ratio (S/N), but also luminosity fractions (flum) of young and old components. At given S/N and flum, Δ of young components tends to be larger than Δ of old components; e.g. σ(Δ[M/H]) ∼ 0.40 versus 0.23 at S/N = 30 and flum = 50 per cent. The age-metallicity degeneracy appears to be insignificant, but Δlog(age/yr) shows an obvious correlation with Δfmass for young stellar components ($\mathcal {R}\sim 0.6$). The impact of dust attenuation and emission lines appears to be mostly insignificant. We discuss how this methodology can be applied to spectroscopic studies of the formation histories of galaxies, with a few examples of SAMI galaxies.

SAMI-H i: the connection between global asymmetry in the ionized and neutral atomic hydrogen gas in galaxies

ABSTRACT Observations of the neutral atomic hydrogen (${\rm H\, {\small I}}$) gas in galaxies are predominantly spatially unresolved, in the form of a global ${\rm H\, {\small I}}$ spectral line. There has been substantial work on quantifying asymmetry in global ${\rm H\, {\small I}}$ spectra (‘global ${\rm H\, {\small I}}$ asymmetry’), but due to being spatially unresolved, it remains unknown what physical regions of galaxies the asymmetry traces, and whether the other gas phases are affected. Using optical integral field spectrograph (IFS) observations from the Sydney AAO Multi-object IFS (SAMI) survey for which global ${\rm H\, {\small I}}$ spectra are also available (SAMI-${\rm H\, {\small I}}$), we study the connection between asymmetry in galaxies’ ionized and neutral gas reservoirs to test if and how they can help us better understand the origin of global ${\rm H\, {\small I}}$ asymmetry. We reconstruct the global Hα spectral line from the IFS observations and find that while some global Hα asymmetries can arise from disturbed ionized gas kinematics, the majority of asymmetric cases are driven by the distribution of Hα-emitting gas. When compared to the ${\rm H\, {\small I}}$, we find no evidence for a relationship between the global Hα and ${\rm H\, {\small I}}$ asymmetry. Further, a visual inspection reveals that cases where galaxies have qualitatively similar Hα and ${\rm H\, {\small I}}$ spectral profiles can be spurious, with the similarity originating from an irregular 2D Hα flux distribution. Our results highlight that comparisons between global Hα and ${\rm H\, {\small I}}$ asymmetry are not straightforward, and that many global ${\rm H\, {\small I}}$ asymmetries trace disturbances that do not significantly impact the central regions of galaxies.

The SAMI Galaxy Survey: Detection of Environmental Dependence of Galaxy Spin in Observations and Simulations Using Marked Correlation Functions

Abstract The existence of a kinematic morphology–density relation remains uncertain, and instead stellar mass appears the more dominant driver of galaxy kinematics. We investigate the dependence of the stellar spin parameter proxy λ R e on environment using a marked cross-correlation method with data from the Sydney Australian Astronomical Observatory Multi-object Integral-field Spectrograph (SAMI) Galaxy Survey. Our sample contains 710 galaxies with spatially resolved stellar velocity and velocity dispersion measurements. By utilizing the highly complete spectroscopic data from the Galaxy and Mass Assembly Survey, we calculate marked cross-correlation functions for SAMI galaxies using a pair count estimator and marks based on stellar mass and λ R e . We detect an anticorrelation of stellar kinematics with environment at the 3.2σ level, such that galaxies with low λ R e values are preferably located in denser galaxy environments. However, a significant correlation between stellar mass and environment is also found (correlation at 2.4σ), as found in previous works. We compare these results to mock observations from the cosmological Evolution and Assembly of Galaxies and their Environments (EAGLE) simulations, where we find a similar significant λ R e anticorrelation with environment, and a mass and environment correlation. We demonstrate that the environmental correlation of λ R e is not caused by the mass–environment relation. The significant relationship between λ R e and environment remains when we exclude slow rotators. The signals in SAMI and EAGLE are strongest on small scales (10–100 kpc) as expected from galaxy interactions and mergers. Our work demonstrates that the technique of marked correlation functions is an effective tool for detecting the relationship between λ R e and environment.

The SAMI Galaxy Survey: the role of disc fading and progenitor bias in kinematic transitions

ABSTRACT We use comparisons between the Sydney-AAO Multi-object Integral Field Spectrograph (SAMI) Galaxy Survey and equilibrium galaxy models to infer the importance of disc fading in the transition of spirals into lenticular (S0) galaxies. The local S0 population has both higher photometric concentration and lower stellar spin than spiral galaxies of comparable mass and we test whether this separation can be accounted for by passive aging alone. We construct a suite of dynamically self-consistent galaxy models, with a bulge, disc, and halo using the galactics code. The dispersion-dominated bulge is given a uniformly old stellar population, while the disc is given a current star formation rate putting it on the main sequence, followed by sudden instantaneous quenching. We then generate mock observables (r-band images, stellar velocity, and dispersion maps) as a function of time since quenching for a range of bulge/total (B/T) mass ratios. The disc fading leads to a decline in measured spin as the bulge contribution becomes more dominant, and also leads to increased concentration. However, the quantitative changes observed after 5 Gyr of disc fading cannot account for all of the observed difference. We see similar results if we instead subdivide our SAMI Galaxy Survey sample by star formation (relative to the main sequence). We use EAGLE simulations to also take into account progenitor bias, using size evolution to infer quenching time. The EAGLE simulations suggest that the progenitors of current passive galaxies typically have slightly higher spin than present day star-forming disc galaxies of the same mass. As a result, progenitor bias moves the data further from the disc fading model scenario, implying that intrinsic dynamical evolution must be important in the transition from star-forming discs to passive discs.

Gauging the effect of supermassive black holes feedback on quasar host galaxies

ABSTRACT In order to gauge the role that active galactic nuclei play in the evolution of galaxies via the effect of kinetic feedback in nearby QSO 2’s (z ∼ 0.3), we observed eight such objects with bolometric luminosities $L_{bol} \sim 10^{46}\rm {erg\, s^{-1}}$ using Gemini Multi-Object Spectrograph-integral field units. The emission lines were fitted with at least two Gaussian curves, the broadest of which we attributed to gas kinetically disturbed by an outflow. We found that the maximum extent of the outflow ranges from ∼1 to 8 kpc, being ${\sim }\, 0.5\, {\pm }\, 0.3$ times the extent of the [$\mathrm{O\,{\small III}}$] ionized gas region. Our ‘default’ assumptions for the gas density (obtained from the [$\mathrm{S\,{\small II}}$] doublet) and outflow velocities resulted in peak mass outflow rates of $\dot{M}_{\mathrm{ out}}^{{\tt def}}\sim$ 3–30 $\rm {M_{\odot }}\, yr^{-1}$ and outflow power of $\dot{E}_{\mathrm{ out}}^{{\tt \mathrm{ def}}}\sim \, 10^{41}$–$10^{43}\, \mathrm{erg\, s^{-1}}$. The corresponding kinetic coupling efficiencies are $\varepsilon _f^{{\tt def}}=\dot{E}_{\mathrm{ out}}^{{\tt def}}/L_{\mathrm{ bol}}\, \sim 7\times 10^{-4}$–0.5 per cent, with the average efficiency being only 0.06 per cent (0.01 per cent median), implying little feedback powers from ionized gas outflows in the host galaxies. We investigated the effects of varying assumptions and calculations on $\dot{M}_{\mathrm{ out}}$ and $\dot{E}_{\mathrm{ out}}$ regarding the ionized gas densities, velocities, masses, and inclinations of the outflow relative to the plane of the sky, resulting in average uncertainties of 1 dex. In particular, we found that better indicators of the [$\mathrm{O\,{\small III}}$] emitting gas density than the default [$\mathrm{S\,{\small II}}$] line ratio, such as the [$\mathrm{Ar\,{\small IV}}$] λλ4711,40 line ratio, result in almost an order of magnitude decrease in the εf.

Exploring the AGN-merger connection in Arp 245 I: Nuclear star formation and gas outflow in NGC 2992

ABSTRACT Galaxy mergers are central to our understanding of galaxy formation, especially within the context of hierarchical models. Besides having a large impact on the star formation history, mergers are also able to influence gas motions at the centre of galaxies and trigger an active galactic nucleus (AGN). In this paper, we present a case study of the Seyfert galaxy NGC 2992, which together with NGC 2993 forms the early-stage merger system Arp 245. Using Gemini Multi-Object Spectrograph integral field unit data from the inner 1.1 kpc of the galaxy, we were able to spatially resolve the stellar populations, the ionization mechanism, and kinematics of ionized gas. From full spectral synthesis, we found that the stellar population is primarily composed by old metal-rich stars (t ≥ 1.4 Gyr, Z ≥ 2.0 Z⊙), with a contribution of at most 30 per cent of the light from a young and metal-poor population (t ≤ 100 Myr, Z ≤ 1.0 Z⊙). We detect H α and H β emission from the broad-line region with a full width at half-maximum of ∼2000 $\rm km\, s^{-1}$. The narrow-line region kinematics presents two main components: one from gas orbiting the galaxy disc and a blueshifted (velocity ≈ −200 $\rm km\, s^{-1}$) outflow, possibly correlated with the radio emission, with mass outflow rate of ∼2 M⊙ yr−1 and a kinematic power of ∼2 × 1040 erg s−1 ($\dot{E}_{\mathrm{ out}}$/Lbol ≈ 0.2 per cent). We also show even though the main ionization mechanism is the AGN radiation, ionization by young stars and shocks may also contribute to the emission line ratios presented in the innermost region of the galaxy.

The SAMI Galaxy Survey: Stellar Populations of Passive Spiral Galaxies in Different Environments

Abstract We investigate the stellar populations of passive spiral galaxies as a function of mass and environment, using integral field spectroscopy data from the Sydney-AAO Multi-object Integral field spectrograph Galaxy Survey. Our sample consists of 52 cluster passive spirals and 18 group/field passive spirals, as well as a set of S0s used as a control sample. The age and [Z/H] estimated by measuring Lick absorption line strength indices both at the center and within 1R e do not show a significant difference between the cluster and the field/group passive spirals. However, the field/group passive spirals with log(M ⋆/M ⊙) ≳ 10.5 show decreasing [α/Fe] along with stellar mass, which is ∼0.1 dex smaller than that of the cluster passive spirals. We also compare the stellar populations of passive spirals with S0s. In the clusters, we find that passive spirals show slightly younger age and lower [α/Fe] than the S0s over the whole mass range. In the field/group, stellar populations show a similar trend between passive spirals and S0s. In particular, [α/Fe] of the field/group S0s tend to be flattening with increasing mass above log(M ⋆/M ⊙) ≳ 10.5, similar to the field/group passive spirals. We relate the age and [α/Fe] of passive spirals to their mean infall time in phase space; we find a positive correlation, in agreement with the prediction of numerical simulations. We discuss the environmental processes that can explain the observed trends. The results lead us to conclude that the formation of the passive spirals and their transformation into S0s may significantly depend on their environments.

Chemical abundances in Seyfert galaxies – V. The discovery of shocked emission outside the AGN ionization axis

ABSTRACT We present maps for the electron temperature in the inner kpc of three luminous Seyfert galaxies: Mrk 79, Mrk 348, and Mrk 607 obtained from Gemini Multi-Object Spectrograph-integral field unit observations at spatial resolutions of ∼110–280 pc. We study the distributions of electron temperature in active galaxies and find temperatures varying in the range from ∼8000 to $\gtrsim 30\, 000\,$K. Shocks due to gas outflows play an important role in the observed temperature distributions of Mrk 79 and Mrk 348, while standard photoionization models reproduce the derived temperature values for Mrk 607. In Mrk 79 and Mrk 348, we find direct evidence for shock ionization with overall orientation orthogonal to the ionization axis, where shocks can be easily observed as the active galactic nuclei radiation field is shielded by the nuclear dusty torus. This also indicates that even when the ionization cones are narrow, the shocks can be much wider angle.

The SAMI galaxy survey: gas velocity dispersions in low-z star-forming galaxies and the drivers of turbulence

ABSTRACT We infer the intrinsic ionized gas kinematics for 383 star-forming galaxies across a range of integrated star formation rates (SFR ∈ [10−3, 102] M⊙ yr−1) at z ≲ 0.1 using a consistent 3D forward-modelling technique. The total sample is a combination of galaxies from the Sydney-AAO Multiobject Integral field Spectrograph (SAMI) Galaxy survey and DYnamics of Newly Assembled Massive Objects survey. For typical low-z galaxies taken from the SAMI Galaxy Survey, we find the vertical velocity dispersion (σv,z) to be positively correlated with measures of SFR, stellar mass, H i gas mass, and rotational velocity. The greatest correlation is with SFR surface density (ΣSFR). Using the total sample, we find σv,z increases slowly as a function of integrated SFR in the range SFR ∈ [10−3, 1] M⊙ yr−1 from 17 ± 3 to 24 ± 5 km s−1 followed by a steeper increase up to σv,z ∼80 km s−1 for SFR ≳ 1 M⊙ yr−1. This is consistent with recent theoretical models that suggest a σv,z floor driven by star formation feedback processes with an upturn in σv,z at higher SFR driven by gravitational transport of gas through the disc.

Star–Gas Misalignment in Galaxies. I. The Properties of Galaxies from the Horizon-AGN Simulation and Comparisons to SAMI

Abstract Recent integral field spectroscopy observations have found that about 11% of galaxies show star–gas misalignment. The misalignment possibly results from external effects such as gas accretion, interaction with other objects, and other environmental effects, hence providing clues to these effects. We explore the properties of misaligned galaxies using Horizon-AGN, a large-volume cosmological simulation, and compare the results with those of the Sydney-AAO Multi-object integral field spectrograph (SAMI) Galaxy Survey. Horizon-AGN can match the overall misalignment fraction and reproduces the distribution of misalignment angles found by observations surprisingly closely. The misalignment fraction is found to be highly correlated with galaxy morphology both in observations and in the simulation: early-type galaxies are substantially more frequently misaligned than late-type galaxies. The gas fraction is another important factor associated with misalignment in the sense that misalignment increases with decreasing gas fraction. However, there is a significant discrepancy between the SAMI and Horizon-AGN data in the misalignment fraction for the galaxies in dense (cluster) environments. We discuss possible origins of misalignment and disagreement.

Gemini Multi-Object Spectrograph Integral Field Unit Spectroscopy of the Double-peaked Broad Emission Line of a Red Active Galactic Nucleus

Abstract Galaxy mergers are expected to produce multiple supermassive black holes (SMBHs) in close-separation, but the detection of such SMBHs has been difficult. 2MASS J165939.7 + 183436 is a red active galactic nucleus (AGN) that is a prospective merging SMBH candidate owing to its merging features in Hubble Space Telescope imaging and double-peaked broad emission lines (BELs). Herein, we report a Gemini Multi-Object Spectrograph Integral Field Unit observation of a double-peaked broad Hα line of 2MASS J165939.7+183436. Furthermore, we confirm the existence of two BEL peaks that are kinematically separated by 3000 km s−1, with the SMBH of each BEL component weighing at and , if they arise from independent BELs near the two SMBHs. The BEL components were not separated at &gt;0.″1; however, under several plausible assumptions regarding the fitting of each spaxel, the two components are found to be spatially separated at 0.″085 (∼250 pc). Different assumptions for the fitting can lead to a null (&lt;0.″05) or a larger spatial separation (∼0.″15). Given the uncertainty regarding the spatial separation, various models, such as the disk emitter and multiple SMBH models, are viable solutions to explain the double BEL components. These results will promote future research for finding more multiple SMBH systems in red AGNs, and higher-resolution imaging validates these different models.

The SAMI Galaxy Survey: The contribution of different kinematic classes to the stellar mass function of nearby galaxies

Abstract We use the complete Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey to determine the contribution of slow rotators, as well as different types of fast rotators, to the stellar mass function of galaxies in the local Universe. We use stellar kinematics not only to discriminate between fast and slow rotators, but also to distinguish between dynamically cold systems (i.e., consistent with intrinsic axis ratios&lt;0.3) and systems including a prominent dispersion-supported bulge. We show that fast rotators account for more than $80\%$ of the stellar mass budget of nearby galaxies, confirming that their number density overwhelms that of slow rotators at almost all masses from 109 to 1011.5M⊙. Most importantly, dynamically cold disks contribute to at least $25\%$ of the stellar mass budget of the local Universe, significantly higher than what is estimated from visual morphology alone. For stellar masses up to 1010.5M⊙, this class makes up $&gt;=30\%$ of the galaxy population in each stellar mass bin. The fact that many galaxies that are visually classified as having two-components have stellar spin consistent with dynamically cold disks suggests that the inner component is either rotationally-dominated (e.g., bar, pseudo-bulge) or has little effect on the global stellar kinematics of galaxies.

Outflowing gas in a compact ionization cone in the Seyfert 2 galaxy ESO 153-G20

ABSTRACT We present two-dimensional ionized gas and stellar kinematics in the inner 1.4 × 1.9 kpc2 of the Seyfert 2 galaxy ESO 153-G20 obtained with the Gemini-South/Gemini multi-object spectrograph integral field unit (GMOS-IFU) at a spatial resolution of ~250 pc and spectral resolution of 36 km s−1. Strong [O iii], Hα, [N ii] and [S ii] emission lines are detected over the entire field of view. The stellar kinematics trace circular rotation with a projected velocity amplitude of ±96 km s−1, a kinematic major axis in position angle of 11°, and an average velocity dispersion of 123 km s−1. To analyse the gas kinematics, we used aperture spectra, position–velocity diagrams and single/double Gaussian fits to the emission lines. All lines show two clear kinematic components: a rotating component that follows the stellar kinematics, and a larger-dispersion component, close to the systemic velocity (from which most of the [O iii] emission comes), mainly detected to the south-west. We interpret this second component as gas outflowing at ∼400 km s−1 in a compact (300 pc) ionization cone with a half-opening angle ≤40°. The counter-cone is probably obscured behind a dust lane. We estimate a mass outflow rate of 1.1 M$\odot$ yr−1, 200 times larger than the estimated accretion rate on to the supermassive black hole, and a kinetic to radiative power ratio of 1.7 × 10−3. Bar-induced perturbations probably explain the remaining disturbances observed in the velocity field of the rotating gas component.

The SAMI galaxy survey: stellar population radial gradients in early-type galaxies

ABSTRACT We study the internal radial gradients of the stellar populations in a sample comprising 522 early-type galaxies (ETGs) from the SAMI (Sydney-AAO Multi-object Integral field spectrograph) Galaxy Survey. We stack the spectra of individual spaxels in radial bins, and derive basic stellar population properties: total metallicity ([Z/H]), [Mg/Fe], [C/Fe] and age. The radial gradient (∇) and central value of the fits (evaluated at Re/4) are compared against a set of six observables that may act as drivers of the trends. We find that velocity dispersion (σ) – or, equivalently gravitational potential – is the dominant driver of the chemical composition gradients. Surface mass density is also correlated with the trends, especially with stellar age. The decrease of ∇[Mg/Fe] with increasing σ is contrasted by a rather shallow dependence of ∇[Z/H] with σ (although this radial gradient is overall rather steep). This result, along with a shallow age slope at the massive end, imposes a substantial constraint on the progenitors of the populations that contribute to the formation of the outer envelopes of ETGs. The SAMI sample is split, by design, between ‘field’ and cluster galaxies. Only weak environment-related differences are found, most notably a stronger dependence of central total metallicity ([Z/H]e4) with σ, along with a marginal trend of ∇[Z/H] to steepen in cluster galaxies, a result that is not followed by [Mg/Fe]. The results presented here serve as stringent constraints on numerical models of the formation and evolution of ETGs.