scholarly journals A sub-kiloparsec-scale view of un-lensed submillimeter galaxies

2019 ◽  
Vol 15 (S352) ◽  
pp. 287-290
Author(s):  
Ken-ichi Tadaki ◽  
Daisuke Iono
Keyword(s):  
Surface Density ◽  
Gravitational Instability ◽  
Effective Radius ◽  
The Other ◽  
Ex Situ ◽  
Submillimeter Galaxies ◽  
The Galaxy ◽  
Central Regions ◽  
Kinematic Properties

AbstractSubmillimeter galaxies at z > 3 building up their central cores through compact starbursts with an effective radius of 1–2 kpc. Our ALMA high-resolution observations reveal off-center gas clumps in a submillimeter galaxy at z = 4.3, COSMOS-AzTEC-1, as well as a rotation-dominated disk. Exploiting the kinematic properties and the spatial distribution of gas mass surface density, we find that the starburst disk is gravitationally unstable. This result is consistent with a scenario where in-situ clumps are formed through disk instability. On the other hand, we find evidence for an ex-situ clump that does not corotate with the starburst disk. The accretion of such a non-corotating clump could stimulate violent disk instability, driving gas inflows into the central regions of the galaxy. Our results suggest that compact cores are formed through an extreme starburst due to a gravitational instability, triggered by non-corotating clumps.

scholarly journals Chemodynamics of barred galaxies in cosmological simulations: On the Milky Way’s quiescent merger history and in-situ bulge

2020 ◽  
Vol 494 (4) ◽  
pp. 5936-5960 ◽  
Author(s):  
F Fragkoudi ◽  
R J J Grand ◽  
R Pakmor ◽  
G Blázquez-Calero ◽  
I Gargiulo ◽  
...  
Keyword(s):  
Milky Way ◽  
Stellar Populations ◽  
Ex Situ ◽  
Mass Ratio ◽  
Star Forming ◽  
Barred Galaxies ◽  
The Galaxy ◽  
Central Regions ◽  
Major Merger

ABSTRACT We explore the chemodynamical properties of a sample of barred galaxies in the Auriga magnetohydrodynamical cosmological zoom-in simulations, which form boxy/peanut (b/p) bulges, and compare these to the Milky Way (MW). We show that the Auriga galaxies which best reproduce the chemodynamical properties of stellar populations in the MW bulge have quiescent merger histories since redshift z ∼ 3.5: their last major merger occurs at $t_{\rm lookback}\gt 12\, \rm Gyr$, while subsequent mergers have a stellar mass ratio of ≤1:20, suggesting an upper limit of a few per cent for the mass ratio of the recently proposed Gaia Sausage/Enceladus merger. These Auriga MW-analogues have a negligible fraction of ex-situ stars in the b/p region ($\lt 1{{\ \rm per\ cent}}$), with flattened, thick disc-like metal-poor stellar populations. The average fraction of ex-situ stars in the central regions of all Auriga galaxies with b/p’s is 3 per cent – significantly lower than in those which do not host a b/p or a bar. While the central regions of these barred galaxies contain the oldest populations, they also have stars younger than 5 Gyr (>30 per cent) and exhibit X-shaped age and abundance distributions. Examining the discs in our sample, we find that in some cases a star-forming ring forms around the bar, which alters the metallicity of the inner regions of the galaxy. Further out in the disc, bar-induced resonances lead to metal-rich ridges in the Vϕ − r plane – the longest of which is due to the Outer Lindblad Resonance. Our results suggest the Milky Way has an uncommonly quiet merger history, which leads to an essentially in-situ bulge, and highlight the significant effects the bar can have on the surrounding disc.

scholarly journals The merger-driven evolution of massive early-type galaxies

2020 ◽  
Vol 15 (S359) ◽  
pp. 62-66
Author(s):  
Carlo Cannarozzo ◽  
Carlo Nipoti ◽  
Alessandro Sonnenfeld ◽  
Alexie Leauthaud ◽  
Song Huang ◽  
...  
Keyword(s):  
Mass Velocity ◽  
Selection Criteria ◽  
Velocity Dispersion ◽  
Ex Situ ◽  
Scaling Relations ◽  
Early Type ◽  
History Of ◽  
Kinematic Properties ◽  
Shed Light

AbstractThe evolution of the structural and kinematic properties of early-type galaxies (ETGs), their scaling relations, as well as their stellar metallicity and age contain precious information on the assembly history of these systems. We present results on the evolution of the stellar mass-velocity dispersion relation of ETGs, focusing in particular on the effects of some selection criteria used to define ETGs. We also try to shed light on the role that in-situ and ex-situ stellar populations have in massive ETGs, providing a possible explanation of the observed metallicity distributions.

scholarly journals The assembly history of the nearest S0 galaxy NGC 3115 from its kinematics out to six half-light radii

2020 ◽  
Vol 495 (1) ◽  
pp. 1321-1339 ◽  
Author(s):  
Arianna Dolfi ◽  
Duncan A Forbes ◽  
Warrick J Couch ◽  
Anna Ferré-Mateu ◽  
Sabine Bellstedt ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Dwarf Galaxies ◽  
Ex Situ ◽  
Mass Ratio ◽  
Rotating Disc ◽  
Rotation Pattern ◽  
History Of ◽  
Kinematic Properties ◽  
Fast Rotating

ABSTRACT Using new and archival data, we study the kinematic properties of the nearest field S0 galaxy, NGC 3115, out to ∼6.5 half-light radii (Re) from its stars (integrated starlight), globular clusters (GCs), and planetary nebulae (PNe). We find evidence of three kinematic regions with an inner transition at ∼0.2 Re from a dispersion-dominated bulge (Vrot/σ < 1) to a fast-rotating disc (Vrot/σ > 1), and then an additional transition from the disc to a slowly rotating spheroid at $\sim 2\!-\!2.5\, R_\mathrm{e}$, as traced by the red GCs and PNe (and possibly by the blue GCs beyond $\sim 5\, R_\mathrm{e}$). From comparison with simulations, we propose an assembly history in which the original progenitor spiral galaxy undergoes a gas-rich minor merger that results in the embedded kinematically cold disc that we see today in NGC 3115. At a later stage, dwarf galaxies, in mini mergers (mass ratio < 1:10), were accreted building up the outer slowly rotating spheroid, with the central disc kinematics largely unaltered. Additionally, we report new spectroscopic observations of a sample of ultracompact dwarfs (UCDs) around NGC 3115 with the Keck/KCWI instrument. We find that five UCDs are inconsistent with the general rotation field of the GCs, suggesting an ex situ origin for these objects, i.e. perhaps the remnants of tidally stripped dwarfs. A further seven UCDs follow the GC rotation pattern, suggesting an in situ origin and, possibly a GC-like nature.

scholarly journals Star formation at the Galactic Centre: coevolution of multiple young stellar discs

2019 ◽  
Vol 490 (4) ◽  
pp. 5820-5831 ◽  
Author(s):  
Alessandra Mastrobuono-Battisti ◽  
Hagai B Perets ◽  
Alessia Gualandris ◽  
Nadine Neumayer ◽  
Anna C Sippel
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Direct Evidence ◽  
Galactic Nuclei ◽  
Galactic Centre ◽  
Stellar Clusters ◽  
Stellar Disc ◽  
The Galaxy ◽  
Kinematic Properties

ABSTRACT Studies of the Galactic Centre suggest that in situ star formation may have given rise to the observed stellar population near the central supermassive black hole (SMBH). Direct evidence for a recent starburst is provided by the currently observed young stellar disc (2–7 Myr) in the central 0.5 pc of the Galaxy. This result suggests that star formation in galactic nuclei may occur close to the SMBH and produce initially flattened stellar discs. Here, we explore the possible build-up and evolution of nuclear stellar clusters near SMBHs through in situ star formation producing stellar discs similar to those observed in the Galactic Centre and other nuclei. We use N-body simulations to model the evolution of multiple young stellar discs and explore the potential observable signatures imprinted by such processes. Each of the five simulated discs is evolved for 100 Myr before the next one is introduced in the system. We find that populations born at different epochs show different morphologies and kinematics. Older and presumably more metal-poor populations are more relaxed and extended, while younger populations show a larger amount of rotation and flattening. We conclude that star formation in central discs can reproduce the observed properties of multiple stellar populations in galactic nuclei differing in age, metallicity, and kinematic properties.

scholarly journals The Impacts ofEx SituTransplantation on the Physiology of the Taiwanese Reef-Building CoralSeriatopora hystrix

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Anderson B. Mayfield ◽  
Tung-Yung Fan ◽  
Chii-Shiarng Chen
Keyword(s):  
Photosynthetic Performance ◽  
Light Regime ◽  
The Other ◽  
Ex Situ ◽  
Field Sampling ◽  
In Captivity ◽  
Southern Taiwan ◽  
Seriatopora Hystrix ◽  
Study Sites

We sought to determine whether the Indo-Pacific reef-building coralSeriatopora hystrixperforms in a similar manner in the laboratory as it doesin situby measuringSymbiodiniumdensity, chlorophyll a (chl-a) concentration, and the maximum quantum yield of photosystem II (FV/FM) at the time of field sampling (in situ), as well as after three weeks of acclimation and one week of experimentation (ex situ).Symbiodiniumdensity was similar between corals of the two study sites, Houbihu (an upwelling reef) and Houwan (a nonupwelling reef), and also remained at similar levelsex situasin situ. On the other hand, both areal and cell-specific chl-aconcentrations approximately doubledex siturelative toin situ, an increase that may be due to having employed a light regime that differed from that experienced by these corals on the reefs of southern Taiwan from which they were collected. As this change inSymbiodiniumchl-acontent was documented in corals of both sites, the experiment itself was not biased by this difference. Furthermore,FV/FMincreased by only 1%ex siturelative toin situ, indicating that the corals maintained a similar level of photosynthetic performance as displayedin situeven after one month in captivity.

scholarly journals Biopolymer colloids for controlling and templating inorganic synthesis

2014 ◽  
Vol 5 ◽  
pp. 2129-2138 ◽  
Author(s):  
Laura C Preiss ◽  
Katharina Landfester ◽  
Rafael Muñoz-Espí
Keyword(s):  
Nucleation And Growth ◽  
Inorganic Materials ◽  
The Other ◽  
Shell Structures ◽  
Ex Situ ◽  
Inorganic Synthesis ◽  
Wide Range ◽  
Synthetic Approaches ◽  
Soft Templates

Biopolymers and biopolymer colloids can act as controlling agents and templates not only in many processes in nature, but also in a wide range of synthetic approaches. Inorganic materials can be either synthesized ex situ and later incorporated into a biopolymer structuring matrix or grown in situ in the presence of biopolymers. In this review, we focus mainly on the latter case and distinguish between the following possibilities: (i) biopolymers as controlling agents of nucleation and growth of inorganic materials; (ii) biopolymers as supports, either as molecular supports or as carrier particles acting as cores of core–shell structures; and (iii) so-called “soft templates”, which include on one hand stabilized droplets, micelles, and vesicles, and on the other hand continuous scaffolds generated by gelling biopolymers.

An in situ and ex situ TEM study of the formation of thin cobalt silicide films by molecular beam epitaxy on the silicon (100) surface

1988 ◽  
Vol 46 ◽  
pp. 884-885
Author(s):  
D. Loretto ◽  
J. M. Gibson ◽  
S. M. Yalisove ◽  
R. T. Tung
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Defect Density ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Metal Base ◽  
In Situ Experiments ◽  
Potential Applications

The cobalt disilicide/silicon system has potential applications as a metal-base and as a permeable-base transistor. Although thin, low defect density, films of CoSi2 on Si(111) have been successfully grown, there are reasons to believe that Si(100)/CoSi2 may be better suited to the transmission of electrons at the silicon/silicide interface than Si(111)/CoSi2. A TEM study of the formation of CoSi2 on Si(100) is therefore being conducted. We have previously reported TEM observations on Si(111)/CoSi2 grown both in situ, in an ultra high vacuum (UHV) TEM and ex situ, in a conventional Molecular Beam Epitaxy system.The procedures used for the MBE growth have been described elsewhere. In situ experiments were performed in a JEOL 200CX electron microscope, extensively modified to give a vacuum of better than 10-9 T in the specimen region and the capacity to do in situ sample heating and deposition. Cobalt was deposited onto clean Si(100) samples by thermal evaporation from cobalt-coated Ta filaments.

A very rapid in situ Kikuchi technique to determine relative crystal misorientation

1988 ◽  
Vol 46 ◽  
pp. 830-831
Author(s):  
J. I. Bennetch
Keyword(s):  
Electron Beam ◽  
Analytical Techniques ◽  
Superplastic Forming ◽  
The Other ◽  
Kikuchi Pattern ◽  
Kikuchi Line ◽  
Line Analysis

In a recent study of the superplastic forming (SPF) behavior of certain Al-Li-X alloys, the relative misorientation between adjacent (sub)grains proved to be an important parameter. It is well established that the most accurate way to determine misorientation across boundaries is by Kikuchi line analysis. However, the SPF study required the characterization of a large number of (sub)grains in each sample to be statistically meaningful, a very time-consuming task even for comparatively rapid Kikuchi analytical techniques.In order to circumvent this problem, an alternate, even more rapid in-situ Kikuchi technique was devised, eliminating the need for the developing of negatives and any subsequent measurements on photographic plates. All that is required is a double tilt low backlash goniometer capable of tilting ± 45° in one axis and ± 30° in the other axis. The procedure is as follows. While viewing the microscope screen, one merely tilts the specimen until a standard recognizable reference Kikuchi pattern is centered, making sure, at the same time, that the focused electron beam remains on the (sub)grain in question.

The use of transmission and analytical electron microscopy in studying reactions and phase transformations in thin film

1993 ◽  
Vol 51 ◽  
pp. 842-843
Author(s):  
K. Barmak
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Phase Transformations ◽  
Analytical Electron Microscopy ◽  
Ex Situ ◽  
Multilayer Thin Films ◽  
Absolute Concentration ◽  
Analytical Electron ◽  
Deposition Step

Generally, processing of thin films involves several annealing steps in addition to the deposition step. During the annealing steps, diffusion, transformations and reactions take place. In this paper, examples of the use of TEM and AEM for ex situ and in situ studies of reactions and phase transformations in thin films will be presented.The ex situ studies were carried out on Nb/Al multilayer thin films annealed to different stages of reaction. Figure 1 shows a multilayer with dNb = 383 and dAl = 117 nm annealed at 750°C for 4 hours. As can be seen in the micrograph, there are four phases, Nb/Nb3-xAl/Nb2-xAl/NbAl3, present in the film at this stage of the reaction. The composition of each of the four regions marked 1-4 was obtained by EDX analysis. The absolute concentration in each region could not be determined due to the lack of thickness and geometry parameters that were required to make the necessary absorption and fluorescence corrections.

Transmission Electron Microscopy of Epitaxial silicides grown by ultra high vacuum deposition

1989 ◽  
Vol 47 ◽  
pp. 462-463
Author(s):  
D. Loretto ◽  
J. M. Gibson ◽  
S. M. Yalisove
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
High Vacuum ◽  
High Energy ◽  
Energy Electron ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Transmission Electron

The silicides CoSi2 and NiSi2 are both metallic with the fee flourite structure and lattice constants which are close to silicon (1.2% and 0.6% smaller at room temperature respectively) Consequently epitaxial cobalt and nickel disilicide can be grown on silicon. If these layers are formed by ultra high vacuum (UHV) deposition (also known as molecular beam epitaxy or MBE) their thickness can be controlled to within a few monolayers. Such ultrathin metal/silicon systems have many potential applications: for example electronic devices based on ballistic transport. They also provide a model system to study the properties of heterointerfaces. In this work we will discuss results obtained using in situ and ex situ transmission electron microscopy (TEM).In situ TEM is suited to the study of MBE growth for several reasons. It offers high spatial resolution and the ability to penetrate many monolayers of material. This is in contrast to the techniques which are usually employed for in situ measurements in MBE, for example low energy electron diffraction (LEED) and reflection high energy electron diffraction (RHEED), which are both sensitive to only a few monolayers at the surface.

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