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The SAMI Galaxy Survey: Mass as the Driver of the Kinematic Morphology-Density Relation in Clusters
Brough, Sarah,van de Sande, Jesse,Owers, Matt S.,d’Eugenio, Francesco,Sharp, Rob,Cortese, Luca,Scott, Nicholas,Croom, Scott M.,Bassett, Rob,Bekki, Kenji,Bland-Hawthorn, Joss,Bryant, Julia J.,Davies, R American Astronomical Society 2017 The Astrophysical journal Vol.844 No.1
<P>We examine the kinematic morphology of early-type galaxies (ETGs) in eight galaxy clusters in the Sydney-AAO Multi-object Integral-field spectrograph Galaxy Survey. The clusters cover a mass range of 14.2 < log(M-200/M-circle dot) < 15.2 and we measure spatially resolved stellar kinematics for 315 member galaxies with stellar masses 10.0 < log(M-*/M-circle dot) <= 11.7 within 1 R-200 of the cluster centers. We calculate the spin parameter, lambda(R), and use this to classify the kinematic morphology of the galaxies as fast or slow rotators (SRs). The total fraction of SRs in the ETG population is F-SR = 0.14 +/- 0.02 and does not depend on host cluster mass. Across the eight clusters, the fraction of SRs increases with increasing local overdensity. We also find that the slow-rotator fraction increases at small clustercentric radii (R-cl < 0.3 R-200), and note that there is also an increase in the slow-rotator fraction at R-cl similar to 0.6 R-200. The SRs at these larger radii reside in the cluster substructure. We find that the strongest increase in the slow-rotator fraction occurs with increasing stellar mass. After accounting for the strong correlation with stellar mass, we find no significant relationship between spin parameter and local overdensity in the cluster environment. We conclude that the primary driver for the kinematic morphology-density relationship in galaxy clusters is the changing distribution of galaxy stellar mass with the local environment. The presence of SRs in the substructure suggests that the cluster kinematic morphology-density relationship is a result of mass segregation of slow-rotating galaxies forming in groups that later merge with clusters and sink to the cluster center via dynamical friction.</P>
The SAMI Galaxy Survey: global stellar populations on the size–mass plane
Scott, Nicholas,Brough, S.,Croom, Scott M.,Davies, Roger L.,van de Sande, Jesse,Allen, J. T.,Bland-Hawthorn, Joss,Bryant, Julia J.,Cortese, Luca,D'Eugenio, Francesco,Federrath, Christoph,Ferreras, Ign Oxford University Press 2017 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.472 No.3
The SAMI Galaxy Survey: revising the fraction of slow rotators in IFS galaxy surveys
van de Sande, Jesse,Bland-Hawthorn, Joss,Brough, Sarah,Croom, Scott M.,Cortese, Luca,Foster, Caroline,Scott, Nicholas,Bryant, Julia J.,d'Eugenio, Francesco,Tonini, Chiara,Goodwin, Michael,Konstantopou Oxford University Press 2017 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.472 No.2
<P>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/sigma and lambda(R) (spin parameter proxy). Our demonstration involves integral field data from the SAMI (Sydney-AAO Multi-object Integral-field spectrograph) Galaxy Survey and the ATLAS(3D) survey. We find a tight relation for both V/sigma and lambda(R) 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/sigma and lambda(R) radial growth curves are well approximated by second-order polynomials. By only fitting the inner profile (0.5R(e)), we successfully recover the profile out to one R-e if a constraint between the linear and quadratic parameter in the fit is applied. However, the aperture corrections for V/sigma and lambda(R) derived by extrapolating the profiles perform as well as applying a first-order correction. With our aperture-corrected lambda(R) measurements, we find that the fraction of slow rotating galaxies increases with stellar mass. For galaxies with log M-*/M-circle dot > 11, the fraction of slow rotators is 35.9 +/- 4.3 per cent, but is underestimated if galaxies without coverage beyond one R-e 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.</P>
The SAMI Galaxy Survey: observing the environmental quenching of star formation in GAMA groups
Schaefer, A L,Croom, S M,Scott, N,Brough, S,Allen, J T,Bekki, K,Bland-Hawthorn, J,Bloom, J V,Bryant, J J,Cortese, L,Davies, L J M,Federrath, C,Fogarty, L M R,Green, A W,Groves, B,Hopkins, A M,Konstant Oxford University Press 2019 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.483 No.3
Measures of galaxy environment – I. What is ‘environment’?
Muldrew, Stuart I.,Croton, Darren J.,Skibba, Ramin A.,Pearce, Frazer R.,Ann, Hong Bae,Baldry, Ivan K.,Brough, Sarah,Choi, Yun‐,Young,Conselice, Christopher J.,Cowan, Nicolas B.,Gallazzi, Anna,Gr Blackwell Publishing Ltd 2012 Monthly notices of the Royal Astronomical Society Vol.419 No.3
<P><B>ABSTRACT</B></P><P>The influence of a galaxy’s environment on its evolution has been studied and compared extensively in the literature, although differing techniques are often used to define environment. Most methods fall into two broad groups: those that use nearest neighbours to probe the underlying density field and those that use fixed apertures. The differences between the two inhibit a clean comparison between analyses and leave open the possibility that, even with the same data, different properties are actually being measured. In this work, we apply 20 published environment definitions to a common mock galaxy catalogue constrained to look like the local Universe. We find that nearest‐neighbour‐based measures best probe the internal densities of high‐mass haloes, while at low masses the interhalo separation dominates and acts to smooth out local density variations. The resulting correlation also shows that nearest‐neighbour galaxy environment is largely independent of dark matter halo mass. Conversely, aperture‐based methods that probe superhalo scales accurately identify high‐density regions corresponding to high‐mass haloes. Both methods show how galaxies in dense environments tend to be redder, with the exception of the largest apertures, but these are the strongest at recovering the background dark matter environment. We also warn against using photometric redshifts to define environment in all but the densest regions. When considering environment, there are two regimes: the ‘local environment’ internal to a halo best measured with nearest neighbour and ‘large‐scale environment’ external to a halo best measured with apertures. This leads to the conclusion that there is no universal environment measure and the most suitable method depends on the scale being probed.</P>
THE SAMI GALAXY SURVEY: GALAXY INTERACTIONS AND KINEMATIC ANOMALIES IN ABELL 119
Oh, Sree,Yi, Sukyoung K.,Cortese, Luca,Sande, Jesse van de,Mahajan, Smriti,Jeong, Hyunjin,Sheen, Yun-Kyeong,Allen, James T.,Bekki, Kenji,Bland-Hawthorn, Joss,Bloom, Jessica V.,Brough, Sarah,Bryant, Ju American Astronomical Society 2016 The Astrophysical journal Vol.832 No.1
<P>Galaxy mergers are important events that can determine the fate of a galaxy by changing its morphology, star formation activity and mass growth. Merger systems have commonly been identified from their disturbed morphologies, and we now can employ integral field spectroscopy to detect and analyze the impact of mergers on stellar kinematics as well. We visually classified galaxy morphology using deep images (mu(r) = 28 mag arcsec(-2)) taken by the Blanco 4 m telescope at the Cerro Tololo Inter-American Observatory. In this paper we investigate 63 bright (M-r < - 19.3) spectroscopically selected galaxies in Abell 119, of which 53 are early type and 20 show a disturbed morphology by visual inspection. A misalignment between the major axes in the photometric image and the kinematic map is conspicuous in morphologically disturbed galaxies. Our sample is dominated by early-type galaxies, yet it shows a surprisingly tight Tully-Fisher relation except for the morphologically disturbed galaxies which show large deviations. Three out of the eight slow rotators in our sample are morphologically disturbed. The morphologically disturbed galaxies are generally more asymmetric, visually as well as kinematically. Our findings suggest that galaxy interactions, including mergers and perhaps fly-bys, play an important role in determining the orientation and magnitude of a galaxy's angular momentum.</P>