ABSTRACT
The characterization of exoplanets is critical to understanding planet diversity and formation, their atmospheric composition, and the potential for life. This endeavour is greatly enhanced ...when light from the planet can be spatially separated from that of the host star. One potential method is nulling interferometry, where the contaminating starlight is removed via destructive interference. The GLINT instrument is a photonic nulling interferometer with novel capabilities that has now been demonstrated in on-sky testing. The instrument fragments the telescope pupil into sub-apertures that are injected into waveguides within a single-mode photonic chip. Here, all requisite beam splitting, routing, and recombination are performed using integrated photonic components. We describe the design, construction, and laboratory testing of our GLINT pathfinder instrument. We then demonstrate the efficacy of this method on sky at the Subaru Telescope, achieving a null-depth precision on sky of ∼10−4 and successfully determining the angular diameter of stars (via their null-depth measurements) to milliarcsecond accuracy. A statistical method for analysing such data is described, along with an outline of the next steps required to deploy this technique for cutting-edge science.
Abstract
The fraction of galaxies supported by internal rotation compared to galaxies stabilized by internal pressure provides a strong constraint on galaxy formation models. In integral field ...spectroscopy surveys, this fraction is biased because survey instruments typically only trace the inner parts of the most massive galaxies. We present aperture corrections for the two most widely used stellar kinematic quantities V/σ and λR (spin parameter proxy). Our demonstration involves integral field data from the SAMI (Sydney-AAO Multi-object Integral-field spectrograph) Galaxy Survey and the ATLAS3D survey. We find a tight relation for both V/σ and λR when measured in different apertures that can be used as a linear transformation as a function of radius, i.e. a first-order aperture correction. In degraded seeing, however, the aperture corrections are more significant as the steeper inner profile is more strongly affected by the point spread function than the outskirts. We find that V/σ and λR radial growth curves are well approximated by second-order polynomials. By only fitting the inner profile (0.5Re), we successfully recover the profile out to one Re if a constraint between the linear and quadratic parameter in the fit is applied. However, the aperture corrections for V/σ and λR derived by extrapolating the profiles perform as well as applying a first-order correction. With our aperture-corrected λR measurements, we find that the fraction of slow rotating galaxies increases with stellar mass. For galaxies with log M*/M⊙ > 11, the fraction of slow rotators is 35.9 ± 4.3 per cent, but is underestimated if galaxies without coverage beyond one Re are not included in the sample (24.2 ± 5.3 per cent). With measurements out to the largest aperture radius, the slow rotator fraction is similar as compared to using aperture-corrected values (38.3 ± 4.4 per cent). Thus, aperture effects can significantly bias stellar kinematic integral field spectrograph studies, but this bias can now be removed with the method outlined here.
We demonstrate the feasibility and potential of using large integral field spectroscopic surveys to investigate the prevalence of galactic-scale outflows in the local Universe. Using integral field ...data from the Sydney-AAO Multi-object Integral field spectrograph (SAMI) and the Wide Field Spectrograph, we study the nature of an isolated disc galaxy, SDSS J090005.05+000446.7 (z = 0.053 86). In the integral field data sets, the galaxy presents skewed line profiles changing with position in the galaxy. The skewed line profiles are caused by different kinematic components overlapping in the line-of-sight direction. We perform spectral decomposition to separate the line profiles in each spatial pixel as combinations of (1) a narrow kinematic component consistent with H ii regions, (2) a broad kinematic component consistent with shock excitation, and (3) an intermediate component consistent with shock excitation and photoionization mixing. The three kinematic components have distinctly different velocity fields, velocity dispersions, line ratios, and electron densities. We model the line ratios, velocity dispersions, and electron densities with our mappings iv shock and photoionization models, and we reach remarkable agreement between the data and the models. The models demonstrate that the different emission line properties are caused by major galactic outflows that introduce shock excitation in addition to photoionization by star-forming activities. Interstellar shocks embedded in the outflows shock-excite and compress the gas, causing the elevated line ratios, velocity dispersions, and electron densities observed in the broad kinematic component. We argue from energy considerations that, with the lack of a powerful active galactic nucleus, the outflows are likely to be driven by starburst activities. Our results set a benchmark of the type of analysis that can be achieved by the SAMI Galaxy Survey on large numbers of galaxies.
Cosmological hydrodynamical simulations are rich tools to understand the build-up of stellar mass and angular momentum in galaxies, but require some level of calibration to observations. We compare ...predictions at |$z$| ∼ 0 from the eagle, hydrangea, horizon-agn, and magneticum simulations with integral field spectroscopic (IFS) data from the SAMI (Sydney-AAO Multi-object Integral field spectrograph) Galaxy Survey, ATLAS^3D, CALIFA (Calar Alto Legacy Integral Field Area), and MASSIVE surveys. The main goal of this work is to simultaneously compare structural, dynamical, and stellar population measurements in order to identify key areas of success and tension. We have taken great care to ensure that our simulated measurement methods match the observational methods as closely as possible, and we construct samples that match the observed stellar mass distribution for the combined IFS sample. We find that the eagle and hydrangea simulations reproduce many galaxy relations but with some offsets at high stellar masses. There are moderate mismatches in R_e (+), ε (−), σ_e (−), and mean stellar age (+), where a plus sign indicates that quantities are too high on average, and minus sign too low. The horizon-agn simulations qualitatively reproduce several galaxy relations, but there are a number of properties where we find a quantitative offset to observations. Massive galaxies are better matched to observations than galaxies at low and intermediate masses. Overall, we find mismatches in R_e (+), ε (−), σ_e (−), and (V/σ)_e (−). magneticum matches observations well: this is the only simulation where we find ellipticities typical for disc galaxies, but there are moderate differences in σ_e (−), (V/σ)_e (−), and mean stellar age (+). Our comparison between simulations and observational data has highlighted several areas for improvement, such as the need for improved modelling resulting in a better vertical disc structure, yet our results demonstrate the vast improvement of cosmological simulations in recent years.
We demonstrate a novel technology that combines the power of the multi-object spectrograph with the spatial multiplex advantage of an integral field spectrograph (IFS). The Sydney-AAO (Australian ...Astronomical Observatory) Multi-object IFS (SAMI) is a prototype wide-field system at the Anglo-Australian Telescope (AAT) that allows 13 imaging fibre bundles ('hexabundles') to be deployed over a 1-degree diameter field of view. Each hexabundle comprises 61 lightly fused multi-mode fibres with reduced cladding and yields a 75 per cent filling factor. Each fibre core diameter subtends 1.6 arcsec on the sky and each hexabundle has a field of view of 15 arcsec diameter. The fibres are fed to the flexible AAOmega double-beam spectrograph, which can be used at a range of spectral resolutions (R=λ/δλ≈ 1700-13 000) over the optical spectrum (3700-9500 Å). We present the first spectroscopic results obtained with SAMI for a sample of galaxies at z≈ 0.05. We discuss the prospects of implementing hexabundles at a much higher multiplex over wider fields of view in order to carry out spatially resolved spectroscopic surveys of 104-105 galaxies.
Abstract
We present an analysis of the global stellar populations of galaxies in the SAMI (Sydney-AAO Multi-object Integral field spectrograph) Galaxy Survey. Our sample consists of 1319 galaxies ...spanning four orders of magnitude in stellar mass and includes all morphologies and environments. We derive luminosity-weighted, single stellar population equivalent stellar ages, metallicities and alpha enhancements from spectra integrated within one effective radius apertures. Variations in galaxy size explain the majority of the scatter in the age–mass and metallicity–mass relations. Stellar populations vary systematically in the plane of galaxy size and stellar mass, such that galaxies with high stellar surface mass density are older, more metal rich and alpha enhanced than less dense galaxies. Galaxies with high surface mass densities have a very narrow range of metallicities; however, at fixed mass, the spread in metallicity increases substantially with increasing galaxy size (decreasing density). We identify residual correlations with morphology and environment. At fixed mass and size, galaxies with late-type morphologies, small bulges and low Sérsic n are younger than early type, high n, high bulge-to-total galaxies. Both age and metallicity show small residual correlations with environment; at fixed mass and size, galaxies in denser environments or more massive haloes are older and somewhat more metal rich than those in less dense environments. We connect these trends to evolutionary tracks within the size–mass plane.
Neutrons peek into f-electron bandsNeutron scattering can be used to tease out the details of collective magnetic excitations that yield well-defined peaks in the data. In principle, it could also be ...used to look into single-electron band excitations, but collecting enough data to capture broad distributions of intensity is tricky. Goremychkin et al. used neutron spectrometers that could efficiently capture a large amount of data by rotating the sample, a crystal of the intermediatevalence compound CePd3 (see the Perspective by Georges). The measured dynamical magnetic susceptibility, in combination with detailed ab initio calculations, showed the formation of coherent f-electron bands at low temperatures.Science, this issue p. 186; see also p. 162In common with many strongly correlated electron systems, intermediate valence compounds are believed to display a crossover from a high-temperature regime of incoherently fluctuating local moments to a low-temperature regime of coherent hybridized bands. We show that inelastic neutron scattering measurements of the dynamic magnetic susceptibility of CePd3 provides a benchmark for ab initio calculations based on dynamical mean field theory. The magnetic response is strongly momentum dependent thanks to the formation of coherent f-electron bands at low temperature, with an amplitude that is strongly enhanced by local particle-hole interactions. The agreement between experiment and theory shows that we have a robust first-principles understanding of the temperature dependence of f-electron coherence.
Characterisation of exoplanets is key to understanding their formation, composition and potential for life. Nulling interferometry, combined with extreme adaptive optics, is among the most promising ...techniques to advance this goal. We present an integrated-optic nuller whose design is directly scalable to future science-ready interferometric nullers: the Guided-Light Interferometric Nulling Technology, deployed at the Subaru Telescope. It combines four beams and delivers spatial and spectral information. We demonstrate the capability of the instrument, achieving a null depth better than 10
with a precision of 10
for all baselines, in laboratory conditions with simulated seeing applied. On sky, the instrument delivered angular diameter measurements of stars that were 2.5 times smaller than the diffraction limit of the telescope. These successes pave the way for future design enhancements: scaling to more baselines, improved photonic component and handling low-order atmospheric aberration within the instrument, all of which will contribute to enhance sensitivity and precision.
ABSTRACT
We investigate the stellar kinematics of the bulge and disk components in 826 galaxies with a wide range of morphology from the Sydney-AAO Multi-object Integral-field spectroscopy Galaxy ...Survey. The spatially resolved rotation velocity (V) and velocity dispersion (σ) of bulge and disk components have been simultaneously estimated using the penalized pixel fitting (ppxf) method with photometrically defined weights for the two components. We introduce a new subroutine of ppxf for dealing with degeneracy in the solutions. We show that the V and σ distributions in each galaxy can be reconstructed using the kinematics and weights of the bulge and disk components. The combination of two distinct components provides a consistent description of the major kinematic features of galaxies over a wide range of morphological types. We present Tully–Fisher and Faber–Jackson relations showing that the galaxy stellar mass scales with both V and σ for both components of all galaxy types. We find a tight Faber–Jackson relation even for the disk component. We show that the bulge and disk components are kinematically distinct: (1) the two components show scaling relations with similar slopes, but different intercepts; (2) the spin parameter λR indicates bulges are pressure-dominated systems and disks are supported by rotation; and (3) the bulge and disk components have, respectively, low and high values in intrinsic ellipticity. Our findings suggest that the relative contributions of the two components explain, at least to first order, the complex kinematic behaviour of galaxies.
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