scholarly journals Shatter or not: role of temperature and metallicity in the evolution of thermal instability

2021 ◽  
Vol 502 (4) ◽  
pp. 4935-4952
Author(s):  
Hitesh Kishore Das ◽  
Prakriti Pal Choudhury ◽  
Prateek Sharma
Keyword(s):  
Thermal Instability ◽  
Transient State ◽  
Cooling Time ◽  
Small Scale ◽  
Gas Temperature ◽  
Linear Evolution ◽  
Non Linear ◽  
Density Perturbations ◽  
Cooling Function

ABSTRACT We test how metallicity variation (a background gradient and fluctuations) affects the physics of local thermal instability using analytical calculations and idealized, high-resolution 1D hydrodynamic simulations. Although the cooling function (Λ[T, Z]) and the cooling time (tcool) depend on gas temperature and metallicity, we find that the growth rate of thermal instability is explicitly dependent only on the derivative of the cooling function relative to temperature (∂ln Λ/∂ln T) and not on the metallicity derivative (∂ln Λ/∂ln Z). For most of 104 K ≲ T ≲ 107 K, both the isobaric and isochoric modes (occurring at scales smaller and larger than the sonic length covered in a cooling time [cstcool], respectively) grow linearly, and at higher temperatures (≳107 K) the isochoric modes are stable. We show that even the non-linear evolution depends on whether the isochoric modes are linearly stable or unstable. For the stable isochoric modes, we observe the growth of small-scale isobaric modes but this is distinct from the non-linear fragmentation of a dense cooling region. For unstable isochoric perturbations we do not observe large density perturbations at small scales. While very small clouds (∼min[cstcool]) form in the transient state of non-linear evolution of the stable isochoric thermal instability, most of them merge eventually.

scholarly journals Linear Evolution of Small Scale Cosmological Density Perturbations

1999 ◽  
Vol 183 ◽  
pp. 273-273
Author(s):  
K. Yamamoto ◽  
N. Sugiyama ◽  
H. Sato
Keyword(s):  
Structure Formation ◽  
Hierarchical Clustering ◽  
Density Fluctuations ◽  
Small Scale ◽  
Cosmological Perturbations ◽  
Linear Evolution ◽  
Early Formation ◽  
Small Scales ◽  
Density Perturbations ◽  
Population Iii Stars

We carefully re-examine the evolution of small scale cosmological perturbations, motivated from the studies of cosmic structure formation in the high-z universe. Under the assumption of the hierarchical clustering scenario, the evolution of density fluctuations on very small scales is especially important for the early formation of the bound objects such as population III stars or primordial sub-galaxies.

scholarly journals Non-Linear Evolution of Inhomogeneities in Universes Dominated by Dark Matter

1987 ◽  
Vol 117 ◽  
pp. 369-377
Author(s):  
S. F. Shandarin
Keyword(s):  
Dark Matter ◽  
Gravitational Instability ◽  
Homogeneous Component ◽  
Linear Processes ◽  
Astronomical Data ◽  
Linear Evolution ◽  
Non Linear ◽  
The Universe

The astronomical data show that most of the mass in the Universe is dark. At present there are a few models of the dark matter: (i) the standard neutrino model, (ii) the model with unstable neutrinos, (iii) axion model. All models can be modified with Λ - term which plays role of the homogeneous component of the dark matter. In this paper the non-linear processes of gravitational instability are briefly discussed.

scholarly journals Resolving small-scale cold circumgalactic gas in TNG50

2020 ◽  
Vol 498 (2) ◽  
pp. 2391-2414 ◽  
Author(s):  
Dylan Nelson ◽  
Prateek Sharma ◽  
Annalisa Pillepich ◽  
Volker Springel ◽  
Rüdiger Pakmor ◽  
...  
Keyword(s):  
High Resolution ◽  
Thermal Instability ◽  
Cell Mass ◽  
Small Scale ◽  
M Cell ◽  
Thermal Pressure ◽  
Massive Galaxies ◽  
Density Perturbations ◽  
Intermediate Redshift ◽  
Cold Gas

ABSTRACT We use the high-resolution TNG50 cosmological magnetohydrodynamical simulation to explore the properties and origin of cold circumgalactic medium (CGM) gas around massive galaxies (M⋆ > 1011 M⊙ ) at intermediate redshift ($z \sim 0.5$). We discover a significant abundance of small-scale, cold gas structure in the CGM of ‘red and dead’ elliptical systems, as traced by neutral H i and Mg ii. Halos can host tens of thousands of discrete absorbing cloudlets, with sizes of order a kpc or smaller. With a Lagrangian tracer analysis, we show that cold clouds form due to strong $\delta \rho / \bar{\rho } \gg 1$ gas density perturbations that stimulate thermal instability. These local overdensities trigger rapid cooling from the hot virialized background medium at ∼107 K to radiatively inefficient ∼104 K clouds, which act as cosmologically long-lived, ‘stimulated cooling’ seeds in a regime where the global halo does not satisfy the classic tcool/tff < 10 criterion. Furthermore, these small clouds are dominated by magnetic rather than thermal pressure, with plasma β ≪ 1, suggesting that magnetic fields may play an important role. The number and total mass of cold clouds both increase with resolution, and the mgas ≃ 8 × 104 M⊙ cell mass of TNG50 enables the ∼ few hundred pc, small-scale CGM structure we observe to form. Finally, we make a preliminary comparison against observations from the COS-LRG, LRG-RDR, COS-Halos, and SDSS LRG surveys. We broadly find that our recent, high-resolution cosmological simulations produce sufficiently high covering fractions of extended, cold gas as observed to surround massive galaxies.

The role of collective identifications in family processes of post-trauma reconstruction: An exploratory study with Kurdish refugee families and their diasporic community

2017 ◽  
Vol 5 (2) ◽  
pp. 107-133 ◽  
Author(s):  
Ruth Kevers ◽  
Peter Rober ◽  
Lucia De Haene
Keyword(s):  
Thematic Analysis ◽  
Exploratory Study ◽  
Meaning Making ◽  
Family Processes ◽  
Small Scale ◽  
Refugee Families ◽  
Family Contexts ◽  
Diasporic Community ◽  
And Coping

While collective identifications of diasporic Kurds have attracted considerable scholarly interest, their possible role in familial processes of post-trauma reconstruction has hardly been studied. The aim of this article is therefore to develop an explorative understanding of the deployment and meaning of collective identifications in intimate family contexts by examining the interconnectedness between the transmission of cultural and political belonging and post-trauma meaning-making and coping in Kurdish refugee families. After contextualising diasporic Kurds’ collective identifications through an ethnographic depiction of the Kurdish diasporic community in Belgium, this article reports on findings from a small-scale, exploratory study with five Kurdish refugee families in Belgium. Thematic analysis of family and parent interviews indicates how cultural and political identifications may operate as sources of (1) dealing with cultural bereavement and loss; (2) commemorating trauma; and (3) reversing versus reiterating trauma. Overall, this study’s findings support an explorative understanding of collective identifications as meaningful resources in families’ post-trauma reconstruction.ABSTRACT IN KURMANJIRola nasnameyên komelî di pêvajoyên malbatî yên vesazkirina paş-trawmayê de: Xebateke raveker li ser malbatên kurd ên penaber û civakên wan ên dîasporayêTevî ku nasnameyên komelî yên kurdên dîasporayê ta radeyeke baș bûye mijara lêkolînan, rola wan a muhtemel di pêvajoyên malbatî yên vesazkirina (selihandin) paş-trawmayê qet nehatine vekolîn. Lewma armanca vê gotarê ew e têgihiştineke raveker pêş bixe li ser rol û wateya nasnameyên komelî yên di çarçoveya mehremiya malbatê de, ku vê yekê jî dê bi rêya vekolîna wê têkiliya rijd bike ya di navbera neqlkirina aidiyetên çandî-siyasî û rêyên sazkirina wateyê û serederîkirina li dû trawmayê di nav malbatên kurd ên penaber de. Piştî diyarkirina çarçoveya nasnameya komelî ya Kurdên diasporayê bi rêya teswîreke etnografîk a cemaeta diasporaya Kurd li Belçîkayê, ev gotar encamên ji xebateke biçûk a bi pênc malbatên kurd ên penaber ên li Belçîkayê pêşkêş dike. Tehlîla babetî ya hevpeyvînên ligel malbatan û dayik û bavan nîşan dide ka çawa nasnameyên çandî û siyasî dikarin bibin çavkanî ji bo (1) serederîkirina bi mehrûmiyeta çandî û windahiyên xwe; (2) bibîranîna trawmayê; û (3) kêmrengkirin an, beramber vê yekê, dubarekirina trawmayê. Bi giştî, encamên vê xebatê wê têgihiştineke raveker tesdîq dikin ku nasnameyên kolektîf çavkaniyên kêrhatî ne di vesazkirina paş-trawmayê ya malbatan de. ABSTRACT IN SORANIDewrî nasname bekomellekan le prose binemalleyîyekanî sazkirdinewey paş-trawmayîda: lêkollîneweyekî şirovekarî binemalle penabere kurdekan û civatî ewan le diyasporaLe katêkda nasname bekomellekanî kurdekanî diyaspora le layen şarezakanewe giringîyekî berçawî pê drawe û serincî ewanî bo lay xoyî rakêşawe, bellam sebaret be egerî dewrî prose binemalleyîyekanî sazkirdinewey paş-tirawma be degmen lêkollîneweyek encam drawe. Ke wate, amancî em wutare perepêdan be têgeyîştinêkî şirovekarane lemerr bekarhênan û manay nasname bekomellekan le bestênekanî têkellawîy binemalleyîdaye, ke le rêgey peywendîy nêwan rewtî gwastineweyî grêdraweyî kultûrî û siyasî, sazbûnî mana û herweha rahatin legell kêşekanî qonaẍî paş tirawma le binemalle kurde penaberekanda taqî krawetewe. Dway awirrdanewe le civakî diyasporay kurd le Belcîka, nasname bekomellekanî kurdekanî diyaspora le bestênî xoyda xwêndinewey bo krawe û bem gêreye lem wutareda lêkollîneweyekî şirovekarane bo qebareyekî biçûk le pênc binemalley kurdî penaber le Belcîka dekrê û encamekanî billaw dekrêtewe. Şîkarîyekî babetiyaney wutuwêj legell binemalle û dayk û bawkekan nîşanî dedat ke çon dekrê nasname kultûrî û siyasîyekan wek serçaweyek bo em sê mijare derbikewn: (1) gîrodebûn be ledestçûn û bizirbûnî kultûr; (2) webîrhênanewey tirawma; û (3) pêçewanebûnî tirawma leberamber dûbarebûneweyda. Beşêweyekî giştî, encamekanî em lêkollîneweye piştgîrî le têgeyîştinêkî şirovekarane le nasname bekomellekan dekat ke wekû serçaweyekî giring bo sazkirdinewey binemallekan le dway qonaẍî paş-tirawma seyr dekrêt.

Non-Linear Interaction of MHD Waves with Small-Scale Ionospheric Irregularities

2004 ◽  
Vol 61 (7-12) ◽  
pp. 1055-1071
Author(s):  
N. N. Gerasimova ◽  
V. G. Sinitsin ◽  
Yu. M. Yampolski
Keyword(s):  
Ionospheric Irregularities ◽  
Mhd Waves ◽  
Small Scale ◽  
Linear Interaction ◽  
Non Linear

GOELRO plan is 100 years old

2020 ◽  
Vol 12 (12) ◽  
pp. 4-9
Author(s):  
Pavel A. BUTYRIN ◽  
Keyword(s):  
Agricultural Production ◽  
Historical Context ◽  
Soviet Period ◽  
Small Scale ◽  
Efficient Production ◽  
Soviet Republic ◽  
Starting Conditions ◽  
Per Capita ◽  
State Plan

The historical context in which the State Plan for Electrification of Russia (GOELRO) was developed, establishment of the GOELRO Commission, the GOELRO Plan content, the specific features of its implementation, and the role of the plan in the soviet period of Russia’s history are considered. Attention is paid to the electrification plants of other countries and territories of all inhabited continents, and to the participation of states in the electrification of countries and regions with small-scale and agricultural production in the 1920 s. The specific features pertinent to the electrification of the Russian Socialist Federative Soviet Republic are pointed out, namely, low starting conditions (in 1923, the energy consumption per capita in Russia was 100 times lower than that in Norway), its being state-owned in nature and revolutionary in its purpose: to get done with the main upheavals in the country and to shift the national economy for fore efficient production. The role of V.I. Lenin and G.M. Krzhizhanovsky, who were the initiators of the electrification of Russia, is analyzed in detail. A conclusion is drawn about the need to study both the GOELRO Plan itself and the specific features and circumstances of its implementation within the framework of training modern specialists in electrical engineering.

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