scholarly journals The statistical properties of protostellar discs and their dependence on metallicity

2021 ◽  
Author(s):  
Daniel Elsender ◽  
Matthew R Bate
Keyword(s):  
Cluster Formation ◽  
Small Scale ◽  
Star Forming ◽  
Star Forming Regions ◽  
Characteristic Radius ◽  
Thermochemical Model ◽  
Solar Metallicity ◽  
Hydrodynamical Simulations ◽  
Protostellar Discs ◽  
The Masses

Abstract We present the analysis of the properties of large samples of protostellar discs formed in four radiation hydrodynamical simulations of star cluster formation. The four calculations have metallicities of 0.01, 0.1, 1 and 3 times solar metallicity. The calculations treat dust and gas temperatures separately and include a thermochemical model of the diffuse interstellar medium. We find the radii of discs of bound protostellar systems tend to decrease with decreasing metallicity, with the median characteristic radius of discs in the 0.01 and 3 times solar metallicity calculations being ≈20 and ≈65 au, respectively. Disc masses and radii of isolated protostars also tend to decrease with decreasing metallicity. We find that the circumstellar discs and orbits of bound protostellar pairs, and the two spins of the two protostars are all less well aligned with each other with lower metallicity than with higher metallicity. These variations with metallicity are due to increased small scale fragmentation due to lower opacities and greater cooling rates with lower metallicity, which increase the stellar multiplicity and increase dynamical interactions. We compare the disc masses and radii of protostellar systems from the solar metallicity calculation with recent surveys of discs around Class 0 and I objects in the Orion and Perseus star-forming regions. The masses and radii of the simulated discs have similar distributions to the observed Class 0 and I discs.

scholarly journals Ionisation Feedback in Star and Cluster Formation Simulations

2010 ◽  
Vol 6 (S270) ◽  
pp. 301-308 ◽  
Author(s):  
Barbara Ercolano ◽  
Matthias Gritschneder
Keyword(s):  
Massive Star ◽  
Radiation Transfer ◽  
Cluster Formation ◽  
New Approach ◽  
Star Forming ◽  
Star Forming Regions ◽  
New Codes ◽  
Hydrodynamical Simulations ◽  
Formation Efficiency ◽  
Rapid Expulsion

AbstractFeedback from photoionisation may dominate on parsec scales in massive star-forming regions. Such feedback may inhibit or enhance the star formation efficiency and sustain or even drive turbulence in the parent molecular cloud. Photoionisation feedback may also provide a mechanism for the rapid expulsion of gas from young clusters' potentials, often invoked as the main cause of ‘infant mortality’. There is currently no agreement, however, with regards to the efficiency of this process and how environment may affect the direction (positive or negative) in which it proceeds. The study of the photoionisation process as part of hydrodynamical simulations is key to understanding these issues, however, due to the computational demand of the problem, crude approximations for the radiation transfer are often employed.We will briefly review some of the most commonly used approximations and discuss their major drawbacks. We will then present the results of detailed tests carried out using the detailed photoionisation code mocassin and the SPH+ionisation code iVINE code, aimed at understanding the error introduced by the simplified photoionisation algorithms. This is particularly relevant as a number of new codes have recently been developed along those lines.We will finally propose a new approach that should allow to efficiently and self-consistently treat the photoionisation problem for complex radiation and density fields.

Simulating star-forming regions in spiral galaxies with AMUSE

2019 ◽  
Vol 14 (S351) ◽  
pp. 216-219
Author(s):  
Steven Rieder ◽  
Clare Dobbs ◽  
Thomas Bending
Keyword(s):  
Gas Dynamics ◽  
Molecular Clouds ◽  
Spiral Galaxies ◽  
Initial Conditions ◽  
Cluster Formation ◽  
Star Cluster ◽  
Star Forming ◽  
Star Forming Regions ◽  
Formation And Evolution ◽  
Spiral Arm

AbstractWe present a model for hydrodynamic + N-body simulations of star cluster formation and evolution using AMUSE. Our model includes gas dynamics, star formation in regions of dense gas, stellar evolution and a galactic tidal spiral potential, thus incorporating most of the processes that play a role in the evolution of star clusters.We test our model on initial conditions of two colliding molecular clouds as well as a section of a spiral arm from a previous galaxy simulation.

scholarly journals Star Clusters in Irregular Galaxies in the Local Group

2002 ◽  
Vol 207 ◽  
pp. 94-104
Author(s):  
Eva K. Grebel
Keyword(s):  
Globular Clusters ◽  
Local Group ◽  
Cluster Formation ◽  
Star Clusters ◽  
Open Clusters ◽  
High Angular Resolution ◽  
Star Clusters And Associations ◽  
Star Forming ◽  
Star Forming Regions ◽  
Irregular Galaxies

I summarize our knowledge of star clusters and associations in irregular galaxies other than the Magellanic Clouds in the Local Group. Surveys affording complete area coverage at high angular resolution are still lacking. Confirmed globular clusters are known only in NGC 6822 and WLM. Very few dIrrs contain populous or sparse open clusters. There is a pronounced deficiency of intermediate-age and young clusters. Apart from parent galaxy mass, the lack of interactions may be a key reason for the lack of cluster formation in the dIrrs. All dIrrs have one or several short-lived OB associations in the star-forming regions in their centers.

scholarly journals The formation of discs in clusters

2009 ◽  
Vol 5 (H15) ◽  
pp. 771-771
Author(s):  
Paul C. Clark
Keyword(s):  
Local Density ◽  
Cluster Formation ◽  
Nearby Star ◽  
Single Star ◽  
Star Forming ◽  
Central Object ◽  
Star Forming Regions ◽  
Time Period ◽  
Particle Hydrodynamics ◽  
Smoothed Particle

We review the properties of the discs that form around ‘sink particles’ in smoothed particle hydrodynamics (SPH) simulations of cluster formation, similar to those of Bate et al. (2003) and Bonnell et al. (2004), and compare them to the observed properties of discs in nearby star-forming regions. Contrary to previous suggestions, discs can form and survive in such an environment, despite the chaotic effects of competitive accretion. We find the discs are typically massive, with ratios of disc mass to central object mass of around 0.1, or higher, being typical. Naturally, the evolution of these discs is dominated by gravitational torques, and the more massive examples exhibit strong m=2 spiral modes. We also find that they can continuously grow over a period of 100,000 years, provided the central object is a single sink particle and the local density of sink particles is low. Discs that form around sink particles in the very centres of clusters tend to be shorter lived, but a single star can lose and gain a disc several times during the main accretion phase. However due to the nature of the turbulence in the cluster, the disc orientation can change dramatically over this time period, since disc-sink systems can accrete from counter-rotating envelopes. Since the competitive accretion process brings in material from large distances, the associated angular momentum can be higher than one would expect for an isolated star formation model. As such, we find that the discs are typically several hundred of AUs in extent, with the largest keplerian structures having radii of ~ 2000AU.

scholarly journals NGC 7469 as seen by MEGARA: new results from high-resolution IFU spectroscopy

2020 ◽  
Vol 493 (3) ◽  
pp. 3656-3675 ◽  
Author(s):  
S Cazzoli ◽  
A Gil de Paz ◽  
I Márquez ◽  
J Masegosa ◽  
J Iglesias ◽  
...  
Keyword(s):  
High Resolution ◽  
Spatial Scales ◽  
High Signal ◽  
Ionized Gas ◽  
Narrow Component ◽  
Star Forming ◽  
Star Forming Regions ◽  
Solar Metallicity ◽  
Field Unit ◽  
Ngc 7469

ABSTRACT We present our analysis of high-resolution (R ∼ 20 000) GTC/MEGARA integral-field unit spectroscopic observations, obtained during the commissioning run, in the inner region (12.5 arcsec × 11.3 arcsec) of the active galaxy NGC 7469, at spatial scales of 0.62 arcsec. We explore the kinematics, dynamics, ionization mechanisms, and oxygen abundances of the ionized gas, by modelling the H α-[N ii] emission lines at high signal-to-noise (> 15) with multiple Gaussian components. MEGARA observations reveal, for the first time for NGC 7469, the presence of a very thin (20 pc) ionized gas disc supported by rotation (V/σ = 4.3), embedded in a thicker (222 pc), dynamically hotter (V/σ  =  1.3) one. These discs nearly corotate with similar peak-to-peak velocities (163  versus  137 km s−1), but with different average velocity dispersion (38 ± 1 versus 108 ± 4 km s−1). The kinematics of both discs could be possibly perturbed by star-forming regions. We interpret the morphology and the kinematics of a third (broader) component (σ > 250 km s−1) as suggestive of the presence of non-rotational turbulent motions possibly associated either to an outflow or to the lense. For the narrow component, the [N ii]/H α ratios point to the star-formation as the dominant mechanism of ionization, being consistent with ionization from shocks in the case of the intermediate component. All components have roughly solar metallicity. In the nuclear region of NGC 7469, at r ≤ 1.85 arcsec, a very broad (FWHM  =  2590 km s−1) H α component is contributing (41 per cent) to the global H α-[N ii] profile, being originated in the (unresolved) broad line region of the Seyfert 1.5 nucleus of NGC 7469.

scholarly journals The formation of young massive clusters triggered by cloud–cloud collisions in the Antennae galaxies NGC 4038/NGC 4039

2020 ◽  
Author(s):  
Kisetsu Tsuge ◽  
Yasuo Fukui ◽  
Kengo Tachihara ◽  
Hidetoshi Sano ◽  
Kazuki Tokuda ◽  
...  
Keyword(s):  
Formation Mechanism ◽  
Cluster Formation ◽  
Large Magellanic Cloud ◽  
Star Forming ◽  
Star Forming Regions ◽  
Region I ◽  
Major Merger ◽  
Super Star Clusters ◽  
Massive Clusters ◽  
Key Parameter

Abstract The formation mechanism of super star clusters (SSCs), present-day analogs of the ancient globulars, still remains elusive. The major merger that is the Antennae galaxies is forming SSCs and is one of the primary targets to test the cluster formation mechanism. We reanalyzed the archival ALMA CO data of the Antennae and found three typical observational signatures of a cloud–cloud collision toward SSC B1 and other SSCs in the overlap region: (i) two velocity components with ∼100 km s−1 velocity separation, (ii) bridge features connecting the two components, and (iii) a complementary spatial distribution between them, lending support to collisions of the two components as a cluster formation mechanism. We present a scenario that two clouds with 100 km s−1 velocity separation collided, and SSCs having ∼106–107 M⊙ were formed rapidly during that time scale. We compared the present results with the recent studies of star-forming regions in the Milky Way and the Large Magellanic Cloud, where the SSCs having ∼104–105 M⊙ are located. As a result, we found that there is a positive correlation between the compressed gas pressure generated by collisions and the total stellar mass of an SSC, suggesting that the pressure may be a key parameter in SSC formation.

scholarly journals Photometric properties of reionization-epoch galaxies in the Simba simulations

2020 ◽  
Author(s):  
Xiaohan Wu ◽  
Romeel Davé ◽  
Sandro Tacchella ◽  
Jennifer Lotz
Keyword(s):  
Gas Phase ◽  
Luminosity Function ◽  
Line Of Sight ◽  
Star Forming ◽  
Dust Extinction ◽  
Star Forming Regions ◽  
James Webb Space Telescope ◽  
Hydrodynamical Simulations ◽  
Color Gradients ◽  
Attenuation Laws

Abstract We study the photometric properties and sizes of the reionization-epoch galaxies in high-resolution Simba cosmological hydrodynamical simulations with box sizes of [25, 50]h−1Mpc. Assuming various attenuation laws, we compute photometry by extincting each star particle’s spectrum using the line-of-sight gas metal column density. The predicted ultraviolet luminosity function (UVLF) generally agrees with observations at z = 6, owing to a partial cancellation between the high metallicities of the simulated galaxies and lower dust-to-metal ratios. The simulated z = 8 UVLF is low compared to observations, likely owing to excessive dust extinction. Simba predicts UV continuum slopes (β) in agreement with the z = 6 observations, with the best agreement obtained using a Calzetti extinction law. Interestingly, the gas-phase mass-metallicity relation in Simba is higher at z ∼ 6 than at z ∼ 2, suggesting that rapid early enrichment (and dust growth) might be necessary to match the observed β. We find that β is more sensitive to the dust extinction law than the UVLF. By generating mock James Webb Space Telescope (JWST) images and analysing in a manner similar to observations, we show that Simba’s galaxy size–luminosity relation well reproduces the current z = 6 Hubble observations. Unlike observations at lower redshifts, Simba predicts similar rest-UV and rest-optical sizes of z = 6 galaxies, owing to weak age gradients and dust extinction in star-forming regions counteract each other to weaken the color gradients within galaxies. These predictions will be testable with JWST.

Dust Trapping and Coagulation in Protoplanetary Disks

2018 ◽  
Vol 14 (S345) ◽  
pp. 355-357
Author(s):  
Ya-Ping Li
Keyword(s):  
Protoplanetary Disks ◽  
Large Family ◽  
Continuum Emission ◽  
Nearby Star ◽  
Dust Trapping ◽  
Star Forming ◽  
Star Forming Regions ◽  
Hydrodynamical Simulations ◽  
Two Fluid ◽  
Key Parameter

AbstractIn this work, we carry out two-fluid (gas+dust) hydrodynamical simulations on a large family of models in order to study the dust coagulation and the dust-gas dynamical processes in protoplanetary disks. Our theoretical effort is guided by the observational results of disks in nearby star forming regions at sub-millimeter and millimeter (mm) wavelengths. By a systematic comparison with the continuum emission at several mm bands from ALMA observations, we find that ringed structures are predicated in the unresolved faint disks for those with mm spectral indexes as low as about 2.0. Our parameter exploration can also be used to constrain the fragmentation velocity, one key parameter of the dust coagulation model, and some other disk parameters.

scholarly journals Intense velocity-shears and magnetic fields in diffuse molecular gas: from 10 pc to 5 mpc

2009 ◽  
Vol 5 (H15) ◽  
pp. 442-443
Author(s):  
Edith Falgarone ◽  
Pierre Hily-Blant
Keyword(s):  
Velocity Field ◽  
Magnetic Fields ◽  
Large Scale ◽  
Dust Emission ◽  
Large Scale Structure ◽  
Small Scale ◽  
Molecular Gas ◽  
Gas Velocity ◽  
Star Forming ◽  
Star Forming Regions

AbstractRegions of intense velocity-shears are identified on statistical grounds in nearby diffuse molecular gas: they form conspicuous thin (~ 0.03 pc) and parsec-long structures that do not bear the signatures of shocked gas. Several straight substructures, ~ 3 mpc thick, have been detected at different position-angles within one of them. Two exhibit the largest velocity-shears ever measured far from star forming regions, up to 780 kms−1pc−1. Their position-angles are found to be also those of 10-parsec striations in the I(100μm) dust emission of the large scale environment. The B field projections, where available in these fields, are parallel both to the parsec- and to one of the milliparsec-scale shears. These findings put in relation the small-scale intermittent facet of the gas velocity field and the large scale structure of the magnetic fields.

scholarly journals Why do protoplanetary disks appear not massive enough to form the known exoplanet population?

2018 ◽  
Vol 618 ◽  
pp. L3 ◽  
Author(s):  
C. F. Manara ◽  
A. Morbidelli ◽  
T. Guillot
Keyword(s):  
Protoplanetary Disks ◽  
Protoplanetary Disk ◽  
Giant Planets ◽  
Dust Particles ◽  
Low Mass Stars ◽  
Star Forming ◽  
Star Forming Regions ◽  
Exoplanetary Systems ◽  
Low Mass ◽  
The Masses

When and how planets form in protoplanetary disks is still a topic of discussion. Exoplanet detection surveys and protoplanetary disk surveys are now providing results that are leading to new insights. We collect the masses of confirmed exoplanets and compare their dependence on stellar mass with the same dependence for protoplanetary disk masses measured in ∼1–3 Myr old star-forming regions. We recalculated the disk masses using the new estimates of their distances derived from Gaia DR2 parallaxes. We note that single and multiple exoplanetary systems form two different populations, probably pointing to a different formation mechanism for massive giant planets around very low-mass stars. While expecting that the mass in exoplanetary systems is much lower than the measured disk masses, we instead find that exoplanetary systems masses are comparable or higher than the most massive disks. This same result is found by converting the measured planet masses into heavy element content (core masses for the giant planets and full masses for the super-Earth systems) and by comparing this value with the disk dust masses. Unless disk dust masses are heavily underestimated, this is a big conundrum. An extremely efficient recycling of dust particles in the disk cannot solve this conundrum. This implies that either the cores of planets have formed very rapidly (<0.1–1 Myr) and a large amount of gas is expelled on the same timescales from the disk, or that disks are continuously replenished by fresh planet-forming material from the environment. These hypotheses can be tested by measuring disk masses in even younger targets and by better understanding if and how the disks are replenished by their surroundings.

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