scholarly journals The Cosmic Ballet III: halo spin evolution in the cosmic web

2021 ◽  
Author(s):  
Punyakoti Ganeshaiah Veena ◽  
Marius Cautun ◽  
Rien van de Weygaert ◽  
Elmo Tempel ◽  
Carlos S Frenk
Keyword(s):  
Initial Conditions ◽  
High Redshift ◽  
High Mass ◽  
Thin Filaments ◽  
Web Environment ◽  
Order Of Magnitude ◽  
Low Mass ◽  
Halo Masses ◽  
First Time ◽  
Environmental Dependence

Abstract We explore the evolution of halo spins in the cosmic web using a very large sample of dark matter haloes in the ΛCDM Planck-Millennium N-body simulation. We use the nexus+ multiscale formalism to identify the hierarchy of filaments and sheets of the cosmic web at several redshifts. We find that at all times the magnitude of halo spins correlates with the web environment, being largest in filaments, and, for the first time, we show that it also correlates with filament thickness as well as the angle between spin-orientation and the spine of the host filament. For example, massive haloes in thick filaments spin faster than their counterparts in thin filaments, while for low-mass haloes the reverse is true. We also have studied the evolution of alignment between halo spin orientations and the preferential axes of filaments and sheets. The alignment varies with halo mass, with the spins of low-mass haloes being predominantly along the filament spine, while those of high-mass haloes being predominantly perpendicular to the filament spine. On average, for all halo masses, halo spins become more perpendicular to the filament spine at later times. At all redshifts, the spin alignment shows a considerable variation with filament thickness, with the halo mass corresponding to the transition from parallel to perpendicular alignment varying by more than one order of magnitude. The cosmic web environmental dependence of halo spin magnitude shows little evolution for z ≤ 2 and is likely a consequence of the correlations in the initial conditions or high redshift effects.

scholarly journals Quiescent high mass cores in Orion region

2006 ◽  
Vol 2 (S237) ◽  
pp. 488-488
Author(s):  
T. Velusamy ◽  
D. Li ◽  
P. F. Goldsmith ◽  
W. D. Langer
Keyword(s):  
Initial Conditions ◽  
High Mass ◽  
Mass Star ◽  
Core Mass ◽  
Star Forming ◽  
Star Forming Regions ◽  
Starting Point ◽  
Order Of Magnitude ◽  
Mass Size ◽  
Low Mass

Our goal is to study relatively quiescent dense gas cores, isolated from disruptive stars, to understand the initial conditions of massive star formation. Determining their mass, size, dynamical status, and core mass distribution is a starting point to understand the mechanisms for formation, collapse, and the origin of their IMF. We obtained CSO 350 μm, images of quiescent regions in Orion and detected 51 resolved or nearly resolved molecular cores with masses ranging from 0.1 M to 46 M (Li et al. 2006). The mean mass is 9.8 M, which is one order of magnitude higher than that of the resolved cores in low mass star forming regions, such as Taurus. Our sample includes largely thermally unstable cores, which implies that the cores are supported neither by thermal pressure nor by turbulence, and are probably supercritical. They are likely precursors of protostars.

The AGN dependence on cluster mass

2018 ◽  
Vol 14 (S342) ◽  
pp. 145-148
Author(s):  
Elias Koulouridis ◽  
Keyword(s):  
Galaxy Clusters ◽  
High Velocity ◽  
High Redshift ◽  
High Mass ◽  
X Ray ◽  
Cluster Galaxies ◽  
Cluster Mass ◽  
Bona Fide ◽  
Low Mass ◽  
Velocity Dispersions

AbstractWe present the results of a study of the AGN density in a homogeneous and well studied sample of 167 bona-fide X-ray galaxy clusters (0.1<z<0.5). Our aim is to study the AGN activity in 167 XXL X-ray galaxy clusters as a function of the cluster mass and the location of the AGN in the cluster. We report a significant AGN excess in our low-mass cluster sub-sample between 0.5r500 and 2r500. In contrast, the high-mass sub-sample presents no AGN excess. The AGN excess in poor clusters indicates AGN triggering, supporting previous studies that reported enhanced galaxy merging in the cluster outskirts. This effect is probably prevented by high velocity dispersions in high-mass clusters. Comparing also with previous studies of massive or high-redshift clusters, we conclude that the AGN fraction in cluster galaxies anti-correlates strongly with cluster mass.

scholarly journals A centrally concentrated sub-solar-mass starless core in the Taurus L1495 filamentary complex

2019 ◽  
Vol 71 (4) ◽  
Author(s):  
Kazuki Tokuda ◽  
Kengo Tachihara ◽  
Kazuya Saigo ◽  
Phillipe André ◽  
Yosuke Miyamoto ◽  
...  
Keyword(s):  
Star Formation ◽  
Initial Conditions ◽  
Volume Density ◽  
Mass Star ◽  
Brown Dwarf ◽  
Solar Mass ◽  
Star Forming ◽  
The Core ◽  
Order Of Magnitude ◽  
Low Mass

Abstract The formation scenario of brown dwarfs is still unclear because observational studies to investigate its initial condition are quite limited. Our systematic survey of nearby low-mass star-forming regions using the Atacama Compact Array (aka the Morita array) and the IRAM 30-m telescope in 1.2 mm continuum has identified a centrally concentrated starless condensation with a central H2 volume density of ∼106 cm−3, MC5-N, connected to a narrow (width ∼0.03 pc) filamentary cloud in the Taurus L1495 region. The mass of the core is $\sim {0.2\!-\!0.4}\, M_{\odot }$, which is an order of magnitude smaller than typical low-mass pre-stellar cores. Taking into account a typical core to star formation efficiency for pre-stellar cores (∼20%–40%) in nearby molecular clouds, brown dwarf(s) or very low-mass star(s) may be going to be formed in this core. We have found possible substructures at the high-density portion of the core, although much higher angular resolution observation is needed to clearly confirm them. The subsequent N2H+ and N2D+ observations using the Nobeyama 45-m telescope have confirmed the high-deuterium fractionation (∼30%). These dynamically and chemically evolved features indicate that this core is on the verge of proto-brown dwarf or very low-mass star formation and is an ideal source to investigate the initial conditions of such low-mass objects via gravitational collapse and/or fragmentation of the filamentary cloud complex.

scholarly journals Correlation between mass segregation and structural concentration in relaxed stellar clusters

2019 ◽  
Vol 485 (4) ◽  
pp. 5752-5760 ◽  
Author(s):  
Ruggero de Vita ◽  
Michele Trenti ◽  
Morgan MacLeod
Keyword(s):  
Globular Clusters ◽  
Initial Conditions ◽  
Hubble Space Telescope ◽  
Stellar Clusters ◽  
Low Mass Stars ◽  
Best Fitting ◽  
Low Mass ◽  
The Difference ◽  
Mass Segregation ◽  
First Time

Abstract The level of mass segregation in the core of globular clusters has been previously proposed as a potential indicator of the dynamical constituents of the system, such as presence of a significant population of stellar-mass black holes (BHs), or even a central intermediate-mass black hole (IMBH). However, its measurement is limited to clusters with high-quality Hubble Space Telescope data. Thanks to a set of state-of-the-art direct N-body simulations with up to 200k particles inclusive of stellar evolution, primordial binaries, and varying BH/neutron stars, we highlight for the first time the existence of a clear and tight linear relation between the degree of mass segregation and the cluster structural concentration index. The latter is defined as the ratio of the radii containing 5 per cent and 50 per cent of the integrated light (R5/R50), making it robustly measurable without the need to individually resolve low-mass stars. Our simulations indicate that given R5/R50, the mass segregation Δm (defined as the difference in main-sequence median mass between centre and half-light radius) is expressed as Δm/M⊙ = −1.166R5/R50 + 0.3246, with a root-mean-square error of 0.0148. In addition, we can explain its physical origin and the values of the fitted parameters through basic analytical modelling. Such correlation is remarkably robust against a variety of initial conditions (including presence of primordial binaries and IMBHs) and cluster ages, with a slight dependence in best-fitting parameters on the prescriptions used to measure the quantities involved. Therefore, this study highlights the potential to develop a new observational tool to gain insight on the dynamical status of globular clusters and on its dark remnants.

scholarly journals The XXL Survey

2018 ◽  
Vol 620 ◽  
pp. A20 ◽  
Author(s):  
E. Koulouridis ◽  
M. Ricci ◽  
P. Giles ◽  
C. Adami ◽  
M. Ramos-Ceja ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
High Redshift ◽  
High Mass ◽  
Host Galaxy ◽  
Gas Stripping ◽  
X Ray ◽  
Cluster Galaxies ◽  
Cluster Mass ◽  
Ram Pressure ◽  
Low Mass

Context. We present the results of a study of the active galactic nucleus (AGN) density in a homogeneous and well-studied sample of 167 bona fide X-ray galaxy clusters (0.1 < z < 0.5) from the XXL Survey, from the cluster core to the outskirts (up to 6r500). The results can provide evidence of the physical mechanisms that drive AGN and galaxy evolution within clusters, testing the efficiency of ram pressure gas stripping and galaxy merging in dense environments. Aims. The XXL cluster sample mostly comprises poor and moderately rich structures (M = 1013–4 × 1014 M⊙), a poorly studied population that bridges the gap between optically selected groups and massive X-ray selected clusters. Our aim is to statistically study the demographics of cluster AGNs as a function of cluster mass and host galaxy position. Methods. To investigate the effect of the environment on AGN activity, we computed the fraction of spectroscopically confirmed X-ray AGNs (LX [0.5-10 keV] > 1042 erg cm−1) in bright cluster galaxies with Mi* − 2 < M < Mi* + 1, up to 6r500 radius. The corresponding field fraction was computed from 200 mock cluster catalogues with reshuffled positions within the XXL fields. To study the mass dependence and the evolution of the AGN population, we further divided the sample into low- and high-mass clusters (below and above 1014M⊙, respectively) and two redshift bins (0.1–0.28 and 0.28–0.5). Results. We detect a significant excess of X-ray AGNs, at the 95% confidence level, in low-mass clusters between 0.5r500 and 2r500, which drops to the field value within the cluster cores (r < 0.5r500). In contrast, high-mass clusters present a decreasing AGN fraction towards the cluster centres, in agreement with previous studies. The high AGN fraction in the outskirts is caused by low-luminosity AGNs, up to LX [0.5-10 keV] = 1043 erg cm−1. It can be explained by a higher galaxy merging rate in low-mass clusters, where velocity dispersions are not high enough to prevent galaxy interactions and merging. Ram pressure stripping is possible in the cores of all our clusters, but probably stronger in deeper gravitational potentials. Compared with previous studies of massive or high-redshift clusters, we conclude that the AGN fraction in cluster galaxies anti-correlates strongly with cluster mass. The AGN fraction also increases with redshift, but at the same rate with the respective fraction in field galaxies.

scholarly journals Peter Pan discs: finding Neverland’s parameters

2020 ◽  
Vol 496 (1) ◽  
pp. L111-L115
Author(s):  
Gavin A L Coleman ◽  
Thomas J Haworth
Keyword(s):  
Initial Conditions ◽  
Mass Star ◽  
Evolutionary Models ◽  
Peter Pan ◽  
Low Mass Stars ◽  
Star Forming ◽  
Star Forming Regions ◽  
Accretion Rates ◽  
Order Of Magnitude ◽  
Low Mass

ABSTRACT Peter Pan discs are a recently discovered class of long-lived discs around low-mass stars that survive for an order of magnitude longer than typical discs. In this paper, we use disc evolutionary models to determine the required balance between initial conditions and the magnitude of dispersal processes for Peter Pan discs to be primordial. We find that we require low transport (α ∼ 10−4), extremely low external photoevaporation (${\le}10^{-9}\, {\rm M}_{\odot }\, {\rm yr^{-1}}$), and relatively high disc masses (&gt;0.25M*) to produce discs with ages and accretion rates consistent with Peter Pan discs. Higher transport (α = 10−3) results in disc lifetimes that are too short and even lower transport (α = 10−5) leads to accretion rates smaller than those observed. The required external photoevaporation rates are so low that primordial Peter Pan discs will have formed in rare environments on the periphery of low-mass star-forming regions, or deeply embedded, and as such have never subsequently been exposed to higher amounts of UV radiation. Given that such an external photoevaporation scenario is rare, the required disc parameters and accretion properties may reflect the initial conditions and accretion rates of a much larger fraction of the discs around low-mass stars.

scholarly journals The XXL Survey

2020 ◽  
Vol 642 ◽  
pp. A126 ◽  
Author(s):  
M. Ricci ◽  
R. Adam ◽  
D. Eckert ◽  
P. Ade ◽  
P. André ◽  
...  
Keyword(s):  
High Redshift ◽  
High Mass ◽  
Optical Data ◽  
Local Pressure ◽  
Mass System ◽  
Cluster Galaxy ◽  
X Ray ◽  
The Galaxy ◽  
Low Mass ◽  
The Impact

High-mass clusters at low redshifts have been intensively studied at various wavelengths. However, while more distant objects at lower masses constitute the bulk population of future surveys, their physical state remain poorly explored to date. In this paper, we present resolved observations of the Sunyaev-Zel’dovich (SZ) effect, obtained with the NIKA2 camera, towards the cluster of galaxies XLSSC 102, a relatively low-mass system (M500 ∼ 2 × 1014 M⊙) at z = 0.97 detected from the XXL survey. We combine NIKA2 SZ data, XMM-Newton X-ray data, and Megacam optical data to explore, respectively, the spatial distribution of the gas electron pressure, the gas density, and the galaxies themselves. We find significant offsets between the X-ray peak, the SZ peak, the brightest cluster galaxy, and the peak of galaxy density. Additionally, the galaxy distribution and the gas present elongated morphologies. This is interpreted as the sign of a recent major merging event, which induced a local boost of the gas pressure towards the north of XLSSC 102 and stripped the gas out of the galaxy group. The NIKA2 data are also combined with XXL data to construct the thermodynamic profiles of XLSSC 102, obtaining relatively tight constraints up to about ∼r500, and revealing properties that are typical of disturbed systems. We also explore the impact of the cluster centre definition and the implication of local pressure substructure on the recovered profiles. Finally, we derive the global properties of XLSSC 102 and compare them to those of high-mass-and-low-redshift systems, finding no strong evidence for non-standard evolution. We also use scaling relations to obtain alternative mass estimates from our profiles. The variation between these different mass estimates reflects the difficulty to accurately measure the mass of low-mass clusters at z ∼ 1, especially with low signal-to-noise ratio data and for a disturbed system. However, it also highlights the strength of resolved SZ observations alone and in combination with survey-like X-ray data. This is promising for the study of high redshift clusters from the combination of eROSITA and high resolution SZ instruments and will complement the new generation of optical surveys from facilities such as LSST and Euclid.

scholarly journals Observational Studies of Pre-Stellar Cores and Infrared Dark Clouds

2011 ◽  
Vol 7 (S280) ◽  
pp. 19-32 ◽  
Author(s):  
Paola Caselli
Keyword(s):  
Molecular Cloud ◽  
Chemical Structure ◽  
Initial Conditions ◽  
Theoretical Work ◽  
High Mass ◽  
Mass Star ◽  
Stellar Cluster ◽  
Dark Clouds ◽  
Low Mass ◽  
Infrared Dark Clouds

AbstractStars like our Sun and planets like our Earth form in dense regions within interstellar molecular clouds, called pre-stellar cores (PSCs). PSCs provide the initial conditions in the process of star and planet formation. In the past 15 years, detailed observations of (low-mass) PSCs in nearby molecular cloud complexes have allowed us to find that they are cold (T < 10K) and quiescent (molecular line widths are close to thermal), with a chemistry profoundly affected by molecular freeze-out onto dust grains. In these conditions, deuterated molecules flourish, becoming the best tools to unveil the PSC physical and chemical structure. Despite their apparent simplicity, PSCs still offer puzzles to solve and they are far from being completely understood. For example, what is happening to the gas and dust in their nuclei (the future stellar cradles) is still a mystery that awaits for ALMA. Other important questions are: how do different environments and external conditions affect the PSC physical/chemical structure? Are PSCs in high-mass star forming regions similar to the well-known low-mass PSCs? Here I review observational and theoretical work on PSCs in nearby molecular cloud complexes and the ongoing search and study of massive PSCs embedded in infrared dark clouds (IRDCs), which host the initial conditions for stellar cluster and high-mass star formation.

scholarly journals The quasar clustering and its evolution in a semi-analytic model based on ultra high-resolution N-body simulations

2015 ◽  
Vol 11 (S319) ◽  
pp. 61-61
Author(s):  
Taira Oogi ◽  
Motohiro Enoki ◽  
Tomoaki Ishiyama ◽  
Masakazu A. R. Kobayashi ◽  
Ryu Makiya ◽  
...  
Keyword(s):  
High Resolution ◽  
Qualitative Agreement ◽  
State Of The Art ◽  
High Mass ◽  
Analytic Model ◽  
Model Based ◽  
Major Merger ◽  
Low Mass ◽  
Halo Masses

AbstractWe investigate clustering properties of quasars using a new version of our semi-analytic model of galaxy and quasar formation with state-of-the-art cosmological N-body simulations (Ishiyama et al. 2015; Oogi et al. 2015). We assume that a major merger of galaxies triggers quasar activity. We find that the quasar bias does not depend significantly on the quasar luminosity, similar to observed trends. This result reflects the fact that quasars with a fixed luminosity have various Eddington ratios and thus have various host halo masses that primarily determine the quasar bias. The quasar bias increases with redshift, which is in qualitative agreement with observations. Our bias value is lower than the observed values at high redshifts, implying that we need some mechanisms that make quasars inactive in low-mass haloes and/or that make them more active in high-mass haloes.

scholarly journals Galactic chimney sweeping: the effect of ‘gradual’ stellar feedback mechanisms on the evolution of dwarf galaxies

2019 ◽  
Vol 489 (3) ◽  
pp. 4278-4299
Author(s):  
Lilian Garratt-Smithson ◽  
Graham A Wynn ◽  
Chris Power ◽  
C J Nixon
Keyword(s):  
High Redshift ◽  
High Mass ◽  
Stellar Winds ◽  
Feedback Mechanisms ◽  
Dwarf Spheroidal Galaxies ◽  
Stellar Feedback ◽  
Hydrodynamical Simulations ◽  
Halo Masses ◽  
The Impact ◽  
Spheroidal Galaxies

ABSTRACT We investigate the impact of time-resolved ‘gradual’ stellar feedback processes in high redshift dwarf spheroidal galaxies. Here ‘gradual’ feedback refers to individual stellar feedback events which deposit energy over a period of time. We conduct high-resolution hydrodynamical simulations of dwarf spheroidal galaxies with halo masses of 107–108 M⊙, based on z = 6 progenitors of the Milky Way’s dwarf spheroidal galaxies. We also include a novel feedback prescription for individual massive stars, which includes stellar winds and an HMXB (high mass X-ray binary) phase, on top of supernovae. We find the mass of gas unbound across a 1 Gyr starburst is uniformly lowered if gradual feedback mechanisms are included across the range of metallicities, halo concentration parameters, and galaxy masses studied here. Furthermore, we find including gradual feedback in the smallest galaxies delays the unbinding of the majority of the gas and facilitates the production of ‘chimneys’ in the dense shell surrounding the feedback generated hot, pressurized ‘superbubble’. These ‘chimneys’ vent hot gas from the galaxy interior, lowering the temperature of the central 10 kpc of the gaseous halo. Additionally, we find radiative cooling has little effect on the energetics of simulations that include a short, violent starburst compared with those that have a longer, less concentrated starburst. Finally, we investigate the relative impact of HMXB feedback and stellar winds on our results, finding the ubiquity of stellar winds throughout each starburst makes them a defining factor in the final state of the interstellar medium.

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