Browsing by Subject "ATLAS(3D) PROJECT"

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  • Davis, Timothy A.; van de Voort, Freeke; Rowlands, Kate; McAlpine, Stuart; Wild, Vivienne; Crain, Robert A. (2019)
    Post-starburst galaxies arc typically considered to be a transition population, en route to the red sequence after a recent quenching event. Despite this, recent observations have shown that these objects typically have large reservoirs of cold molecular gas. In this paper we study the star-forming gas properties of a large sample of post-starburst galaxies selected from the cosmological, hydrodynamical EAGLE simulations. These objects resemble observed high-mass post-starburst galaxies both spectroscopically and in terms of their space density, stellar mass distribution, and sizes. We find that the vast majority of simulated post-starburst galaxies have significant gas reservoirs, with star-forming gas masses approximate to 10(9) M-circle dot, in good agreement with those seen in observational samples. The simulation reproduces the observed time evolution of the gas fraction of the post-starburst galaxy population, with the average galaxy losing approximate to 90 per cent of its star-forming interstellar medium in only approximate to 600 Myr. A variety of gas consumption/loss processes are responsible for this rapid evolution, including mergers and environmental effects, while active galactic nuclei play only a secondary role. The fast evolution in the gas fraction of post-starburst galaxies is accompanied by a clear decrease in the efficiency of star formation due to a decrease in the dense gas fraction. We predict that forthcoming ALMA observations of the gas reservoirs of low-redshift post-starburst galaxies will show that the molecular gas is typically compact and has disturbed kinematics, reflecting the disruptive nature of many of the evolutionary pathways that build up the post-starburst galaxy population.
  • Lahen, Natalia; Naab, Thorsten; Johansson, Peter H.; Elmegreen, Bruce; Hu, Chia-Yu; Walch, Stefanie (2020)
    We analyze the three-dimensional shapes and kinematics of the young star cluster population forming in a high-resolution griffin project simulation of a metal-poor dwarf galaxy starburst. The star clusters, which follow a power-law mass distribution, form from the cold phase interstellar medium with an initial mass function sampled with individual stars down to four solar masses at sub-parsec spatial resolution. Massive stars and their important feedback mechanisms are modeled in detail. The simulated clusters follow a surprisingly tight relation between the specific angular momentum and mass with indications of two sub-populations. Massive clusters (M-cl greater than or similar to 3 x 10(4) M) have the highest specific angular momenta at low ellipticities (epsilon similar to 0.2) and show alignment between their shapes and rotation. Lower mass clusters have lower specific angular momenta with larger scatter, show a broader range of elongations, and are typically misaligned indicating that they are not shaped by rotation. The most massive clusters (M greater than or similar to 10(5) M) accrete gas and protoclusters from a less than or similar to 100 pc scale local galactic environment on a t less than or similar to 10 Myr timescale, inheriting the ambient angular momentum properties. Their two-dimensional kinematic maps show ordered rotation at formation, up to v similar to 8.5 km s(-1), consistent with observed young massive clusters and old globular clusters, which they might evolve into. The massive clusters have angular momentum parameters lambda(R) less than or similar to 0.5 and show Gauss-Hermite coefficients h(3) that are anti-correlated with the velocity, indicating asymmetric line-of-sight velocity distributions as a signature of a dissipative formation process.
  • Rantala, Antti; Johansson, Peter H.; Naab, Thorsten; Thomas, Jens; Frigo, Matteo (2018)
    Given its velocity dispersion, the early-type galaxy NGC 1600 has an unusually massive (M-center dot = 1.7 x 10(10) M-circle dot) central supermassive black hole (SMBH) surrounded by a large core (r(b) = 0.7 kpc) with a tangentially biased stellar distribution. We present high-resolution equal-mass merger simulations including SMBHs to study the formation of such systems. The structural parameters of the progenitor ellipticals were chosen to produce merger remnants resembling NGC 1600. We test initial stellar density slopes of rho proportional to r(-1) and rho proportional to r(-3/2) and vary the initial SMBH masses from 8.5 x 10(8) to 8.5 x(.) 10(9) M-circle dot. With increasing SMBH mass, the merger remnants show a systematic decrease in central surface brightness, an increasing core size, and an increasingly tangentially biased central velocity anisotropy. Two-dimensional kinematic maps reveal decoupled, rotating core regions for the most massive SMBHs. The stellar cores form rapidly as the SMBHs become bound, while the velocity anisotropy develops more slowly after the SMBH binaries become hard. The simulated merger remnants follow distinct relations between the core radius and the sphere of influence, and the SMBH mass, similar to observed systems. We find a systematic change in the relations as a function of the progenitor density slope and present a simple scouring model reproducing this behavior. Finally, we find the best agreement with NGC 1600 using SMBH masses totaling the observed value of M-center dot = 1.7 x 10(10) M-circle dot. In general, density slopes of rho proportional to r(-3/2) for the progenitor galaxies are strongly favored for the equal-mass merger scenario.
  • Rawlings, Alexander; Foster, Caroline; van de Sande, Jesse; Taranu, Dan S.; Croom, Scott M.; Bland-Hawthorn, Joss; Brough, Sarah; Bryant, Julia J.; Colless, Matthew; Lagos, Claudia del P.; Konstantopoulos, Iraklis S.; Lawrence, Jon S.; Lopez-Sanchez, Angel R.; Lorente, Nuria P. F.; Medling, Anne M.; Oh, Sree; Owers, Matt S.; Richards, Samuel N.; Scott, Nicholas; Sweet, Sarah M.; Yi, Sukyoung K. (2020)
    We study the behaviour of the spin-ellipticity radial tracks for 507 galaxies from the Sydney AAO Multiobject Integral Field (SAMI) Galaxy Survey with stellar kinematics out to >= 1.5R(e). We advocate for a morpho-dynamical classification of galaxies, relying on spatially resolved photometric and kinematic data. We find the use of spin-ellipticity radial tracks is valuable in identifying substructures within a galaxy, including embedded and counter-rotating discs, that are easily missed in unilateral studies of the photometry alone. Conversely, bars are rarely apparent in the stellar kinematics but are readily identified on images. Consequently, we distinguish the spin-ellipticity radial tracks of seven morpho-dynamical types: elliptical, lenticular, early spiral, late spiral, barred spiral, embedded disc, and 2 sigma galaxies. The importance of probing beyond the inner radii of galaxies is highlighted by the characteristics of galactic features in the spin-ellipticity radial tracks present at larger radii. The density of information presented through spin-ellipticity radial tracks emphasizes a clear advantage to representing galaxies as a track, rather than a single point, in spin-ellipticity parameter space.
  • Gobat, R.; Daddi, E.; Magdis, G.; Bournaud, F.; Sargent, M.; Martig, M.; Jin, S.; Finoguenov, A.; Bethermin, M.; Hwang, H. S.; Renzini, A.; Wilson, G. W.; Aretxaga, I.; Yun, M.; Strazzullo, V.; Valentino, F. (2018)
    Early-type galaxies (ETGs) contain most of the stars present in the local Universe and, above a stellar mass content of similar to 5 x 10(10) solar masses, vastly outnumber spiral galaxies such as the Milky Way. These massive spheroidal galaxies have, in the present day, very little gas or dust in proportion to their mass(1), and their stellar populations have been evolving passively for over 10 billion years. The physical mechanisms that led to the termination of star formation in these galaxies and depletion of their interstellar medium remain largely conjectural. In particular, there are currently no direct measurements of the amount of residual gas that might still be present in newly quiescent spheroidals at high redshift(2). Here we show that quiescent ETGs at redshift z similar to 1.8, close to their epoch of quenching, contained at least two orders of magnitude more dust at a fixed stellar mass compared with local ETGs. This implies the presence of substantial amounts of gas (5-10%), which has been consumed less efficiently than in more active galaxies, probably due to their spheroidal morphology, consistent with our simulations. This lower star formation efficiency, combined with an extended hot gas halo possibly maintained by persistent feedback from an active galactic nucleus, keep ETGs mostly passive throughout cosmic time.