scholarly journals A new channel to form IMBHs throughout cosmic time

2020 ◽  
Vol 501 (1) ◽  
pp. 1413-1425
Author(s):  
Priyamvada Natarajan
Keyword(s):  
High Redshift ◽  
Cosmic Time ◽  
Intermediate Mass ◽  
Massive Galaxies ◽  
Net Zero ◽  
Wide Range ◽  
Low Mass ◽  
Gas Accretion ◽  
Growth Scaling ◽  
Gas Supply

ABSTRACT While the formation of the first black holes (BHs) at high redshift is reasonably well understood though debated, massive BH formation at later cosmic epochs has not been adequately explored. We present a gas accretion driven mechanism that can build-up BH masses rapidly in dense, gas-rich nuclear star clusters (NSCs). Wind-fed supraexponential accretion in these environments under the assumption of net zero angular momentum for the gas, can lead to extremely rapid growth, scaling stellar mass remnant seed BHs up to the intermediate mass black hole (IMBH) range. This new long-lived channel for IMBH formation permits growth to final masses ranging from 50 to 105 M⊙. Growth is modulated by the gas supply, and premature termination can result in the formation of BHs with masses between 50 and a few 100 M⊙ filling in the so-called mass gap. Typically, growth is unimpeded and will result in the formation of IMBHs with masses ranging from ∼100 to 105 M⊙. New detections from the LIGO–VIRGO source GW190521 to the emerging population of ∼105 M⊙ BHs harboured in low-mass dwarf galaxies are revealing this elusive population. Naturally accounting for the presence of off-centre BHs in low-mass dwarfs, this new pathway also predicts the existence of a population of wandering non-central BHs in more massive galaxies detectable via tidal disruption events and as gravitational wave coalescences. Gas-rich NSCs could therefore serve as incubators for the continual formation of BHs over a wide range in mass throughout cosmic time.

scholarly journals Characterizing mass, momentum, energy and metal outflow rates of multi-phase galactic winds in the FIRE-2 cosmological simulations

2021 ◽  
Author(s):  
Viraj Pandya ◽  
Drummond B Fielding ◽  
Daniel Anglés-Alcázar ◽  
Rachel S Somerville ◽  
Greg L Bryan ◽  
...  
Keyword(s):  
Milky Way ◽  
High Redshift ◽  
Mass Loading ◽  
Intermediate Mass ◽  
Order Unity ◽  
Massive Galaxies ◽  
Galactic Winds ◽  
Low Mass ◽  
Halo Gas ◽  
Multi Phase

Abstract We characterize mass, momentum, energy and metal outflow rates of multi-phase galactic winds in a suite of FIRE-2 cosmological ‘zoom-in’ simulations from the Feedback in Realistic Environments (FIRE) project. We analyse simulations of low-mass dwarfs, intermediate-mass dwarfs, Milky Way-mass haloes, and high-redshift massive haloes. Consistent with previous work, we find that dwarfs eject about 100 times more gas from their interstellar medium (ISM) than they form in stars, while this mass ‘loading factor’ drops below one in massive galaxies. Most of the mass is carried by the hot phase (>105 K) in massive haloes and the warm phase (103 − 105 K) in dwarfs; cold outflows (<103 K) are negligible except in high-redshift dwarfs. Energy, momentum and metal loading factors from the ISM are of order unity in dwarfs and significantly lower in more massive haloes. Hot outflows have 2 − 5 × higher specific energy than needed to escape from the gravitational potential of dwarf haloes; indeed, in dwarfs, the mass, momentum, and metal outflow rates increase with radius whereas energy is roughly conserved, indicating swept up halo gas. Burst-averaged mass loading factors tend to be larger during more powerful star formation episodes and when the inner halo is not virialized, but we see effectively no trend with the dense ISM gas fraction. We discuss how our results can guide future controlled numerical experiments that aim to elucidate the key parameters governing galactic winds and the resulting associated preventative feedback.

scholarly journals What dominates the X-ray emission of normal galaxies?

2015 ◽  
Vol 11 (A29B) ◽  
pp. 124-135
Author(s):  
Ann E. Hornschemeier ◽  
Anna Wolter ◽  
Dong-Woo Kim
Keyword(s):  
Black Holes ◽  
High Redshift ◽  
Cosmic Time ◽  
Compact Objects ◽  
Intermediate Mass ◽  
X Ray ◽  
Massive Galaxies ◽  
Normal Galaxies ◽  
Ring Galaxies ◽  
Intermediate Mass Black Holes

AbstractX-ray surveys of normal galaxies, i.e. those that do not host actively supermassive black holes, have revealed important information on the nature of accreting stellar-mass compact objects (neutron stars and black holes), constraints on populations of possible intermediate-mass black holes (102–5M⊙), and on the reservoir of materials in the hot interstellar medium of the most massive galaxies. Here we summarize briefly the results of Chandra and NuSTAR surveys of several samples of galaxies covered during the 2015 IAU General Assembly. This includes a comprehensive study of six nearby starburst galaxies by the NuSTAR mission, of high-redshift galaxies from the 6 Ms Chandra Deep Field South for which evolutionary trends in X-ray emission over cosmic time have been measured, of collisional ring galaxies which are excellent local environments for studying intermediate-mass black holes and of elliptical galaxies which are ideal for study of the hot gas reservoirs containing the effects of stellar and AGN feedback.

scholarly journals Stellar Population Models

2012 ◽  
Vol 8 (S295) ◽  
pp. 272-281 ◽  
Author(s):  
Claudia Maraston
Keyword(s):  
Galaxy Formation ◽  
Stellar Population ◽  
High Redshift ◽  
Spectral Energy Distribution ◽  
Cosmic Time ◽  
Mass Function ◽  
Initial Mass Function ◽  
Asymptotic Giant Branch ◽  
Spectral Energy ◽  
Massive Galaxies

AbstractModelling stellar populations in galaxies is a key approach to gain knowledge on the still elusive process of galaxy formation as a function of cosmic time. In this review, after a summary of the state-of-art, I discuss three aspects of the modelling, that are particularly relevant to massive galaxies, the focus of this symposium, at low and high-redshift. These are the treatment of the Thermally-Pulsating Asymptotic Giant Branch phase, evidences of an unusual Initial Mass Function, and the effect of modern stellar libraries on the model spectral energy distribution.

scholarly journals Observational Comparison of Star Formation in Different Galaxy Types

2010 ◽  
Vol 6 (S270) ◽  
pp. 335-346
Author(s):  
Eva K. Grebel
Keyword(s):  
Star Formation ◽  
Variable Star ◽  
High Mass ◽  
Early Type ◽  
Intermediate Mass ◽  
Wide Range ◽  
Low Mass ◽  
Key Features ◽  
Star Formation Histories ◽  
Hubble Time

AbstractGalaxies cover a wide range of masses and star formation histories. In this review, I summarize some of the evolutionary key features of common galaxy types. At the high-mass end, very rapid, efficient early star formation is observed, accompanied by strong enrichment and later quiescence, well-described by downsizing scenarios. In the intermediate-mass regime, early-type galaxies may still show activity in low-mass environments or when being rejuvenated by wet mergers. In late-type galaxies, we find continuous, though variable star formation over a Hubble time. In the dwarf regime, a wide range of properties from bursty activity to quiescence is observed. Generally, stochasticity dominates here, and star formation rates and efficiencies tend to be low. Morphological types and their star formation properties correlate with environment.

scholarly journals Tidal barrier and the asymptotic mass of proto gas-giant planets

2007 ◽  
Vol 3 (S249) ◽  
pp. 263-266 ◽  
Author(s):  
Ian Dobbs-Dixon ◽  
ShuLin Li ◽  
Douglas N.C. Lin
Keyword(s):  
Giant Planets ◽  
Positive Pressure ◽  
Gap Formation ◽  
Multiple Systems ◽  
Aspect Ratios ◽  
T Tauri ◽  
Nearby Stars ◽  
Low Mass ◽  
Gas Accretion ◽  
Gas Supply

AbstractAlthough late stage gap formation reduces the surface density in the vicinity of protoplanets, simulations suggest gas may continue to leak through the protoplanets tidal barrier, replenishing the gas supply and allowing protoplanets to acquire masses comparable to or larger than that of Jupiter. Global gas depletion is a possible explanation for gaseous planets with lower masses in weak-line T-Tauri disks and ice giants in our own solar system, but it is unlikely to have stalled the growth of multiple systems around nearby stars that contain relatively low-mass, close-in planets along with more massive and longer period companions. Here, we suggest a potential solution. We show that supersonic infall of surrounding gas onto a protoplanet is only possible interior to both its Bondi and Roche radii. Although the initial Bondi radius is much smaller than its Roche radius, the former overtakes the latter during its growth. Thereafter, a positive pressure gradient is required to induce the gas to enter the Roche lobe of the protoplanet and flow is significantly reduced. We present the results of analysis and numerical simulations to show that the accretion rate increases rapidly with the ratio of the protoplanets Roche to Bondi radii. Based on these results we suggest that in regions with low geometric aspect ratios gas accretion is quenched, resulting in relatively low protoplanetary masses.

scholarly journals Outflows in low-mass galaxies at z >1

2016 ◽  
Vol 11 (S321) ◽  
pp. 339-341
Author(s):  
Michael V. Maseda ◽  
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Theoretical Models ◽  
Potential Wells ◽  
Low Mass ◽  
Hydrodynamical Simulations ◽  
Gas Accretion ◽  
Stellar Masses ◽  
Star Formation Histories ◽  
Cold Gas

AbstractStar formation histories of local dwarf galaxies, derived through resolved stellar populations, appear complex and varied. The general picture derived from hydrodynamical simulations is one of cold gas accretion and bursty star formation, followed by feedback from supernovae and winds that heat and eject the central gas reservoirs. This ejection halts star formation until the material cools and re-accretes, resulting in an episodic SFH, particularly at stellar masses below ~ 109 M⊙. Such feedback has often been cited as the driving force behind the observed slowly-rising rotation curves in local dwarfs, due to an under-density of dark matter compared to theoretical models, which is one of the primary challenges to LCDM cosmology. However, these events have not yet been directly observed at high-redshift. Recently, using HST imaging and grism spectroscopy, we have uncovered an abundant population of low-mass galaxies (M* < 109 M⊙) at z = 1 - 2 that are undergoing strong bursts of star formation, in agreement with the theoretical predictions. These Extreme Emission Line Galaxies, with high specific SFRs and shallow gravitational potential wells, are ideal places to test the theoretical prediction of strong feedback-driven outflows. Here we use deep MUSE spectroscopy to search these galaxies for signatures of outflowing material, namely kinematic offsets between absorption lines (in the restframe optical and UV), which trace cool gas, and the nebular emission lines, which define the systemic redshift of the galaxy. Although the EELGs are intrinsically very faint, stacked spectra reveal blueshifted velocity centroids for Fe II absorption, which is indicative of outflowing cold gas. This represents the first constraint on outflows in M* < 109 M⊙ galaxies at z = 1 - 2. These outflows should regulate the star formation histories of low-mass galaxies at early cosmic times and thus play a crucial role in galaxy growth and evolution.

scholarly journals Formation of planetary populations – III. Core composition and atmospheric evaporation

2020 ◽  
Vol 497 (4) ◽  
pp. 4814-4833 ◽  
Author(s):  
Matthew Alessi ◽  
Julie Inglis ◽  
Ralph E Pudritz
Keyword(s):  
Physical Factors ◽  
Solid Core ◽  
Core Composition ◽  
Planetary Cores ◽  
Short Period ◽  
Wide Range ◽  
Low Mass ◽  
Orbital Periods ◽  
Far Ultraviolet ◽  
Gas Accretion

ABSTRACT The exoplanet mass–radius diagram reveals that super-Earths display a wide range of radii, and therefore mean densities, at a given mass. Using planet population synthesis models, we explore the key physical factors that shape this distribution: planets’ solid core compositions, and their atmospheric structure. For the former, we use equilibrium disc chemistry models to track accreted minerals on to planetary cores throughout the formation. For the latter, we track gas accretion during the formation and consider photoevaporation-driven atmospheric mass-loss to determine what portion of accreted gas escapes after the disc phase. We find that atmospheric stripping of Neptunes and sub-Saturns at small orbital radii (≲0.1 au) plays a key role in the formation of short-period super-Earths. Core compositions are strongly influenced by the trap in which they formed. We also find a separation between Earth-like planet compositions at small orbital radii ≲0.5 au and ice-rich planets (up to 50 per cent by mass) at larger orbits ∼1 au. This corresponds well with the Earth-like mean densities inferred from the observed position of the low-mass planet radius valley at small orbital periods. Our model produces planet radii comparable to observations at masses ∼1–3 M⊕. At larger masses, planets’ accreted gas significantly increases their radii to be larger than most of the observed data. While photoevaporation, affecting planets at small orbital radii ≲0.1 au, reduces a subset of these planets’ radii and improves our comparison, most planets in our computed populations are unaffected due to low-far ultraviolet fluxes as they form at larger separations.

scholarly journals Star Formation Through Cosmic Time

2006 ◽  
Vol 2 (S235) ◽  
pp. 261-267
Author(s):  
Michael A. Dopita
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Globular Clusters ◽  
High Redshift ◽  
Cosmic Time ◽  
Star Formation History ◽  
Massive Black Holes ◽  
Massive Galaxies ◽  
History Of ◽  
Population Iii Stars

AbstractThis paper reviews the star formation history of the Universe, from the first stars to the current day, with emphasis on the critical analysis of the techniques that have been used to determine it, especially considering the role of dust. We consider the first population of stars, the Population III stars, were formed at redshifts ranging as high as z ~ 60, the formation of the Globular Clusters, the main epoch of galaxy formation. In the sub-mm galaxies and high-redshift radio galaxies the collapse of massive galaxies was surprisingly rapid, and that the growth of super-massive black holes at their centers provides the energy input to eject the galactic interstellar medium while at the same time precipitating a final burst of star formation and the ejection of their ISM so that the subsequent evolution of these galaxies is passive.

scholarly journals Galaxies in most dense environments at z ~ 1.4

2012 ◽  
Vol 10 (H16) ◽  
pp. 377-377
Author(s):  
V. Strazzullo
Keyword(s):  
Galaxy Evolution ◽  
High Redshift ◽  
Cosmic Time ◽  
Cluster Center ◽  
Final Conclusion ◽  
Early Type ◽  
Massive Galaxies ◽  
Star Forming ◽  
Cluster Cores ◽  
Red Sequence

AbstractThe X-ray luminous system XMMU J2235-2557 at z~1.4 is among the most massive of the very distant galaxy clusters, and remains a unique laboratory to observe environment-biased galaxy evolution already 9 Gyr ago (Lidman et al.2008, Rosati et al.2009, Strazzullo et al.2010). At a cosmic time when cluster cores start showing evidence of a still active galaxy population, star-forming (M>1010M⊙) galaxies in XMMU J2235-2557 are typically located beyond ~250kpc from the cluster center, with the cluster core already effectively quenched and dominated by massive galaxies on a tight red sequence, showing early-type spectral features and bulge-dominated morphologies. While masses and stellar populations of these red-sequence galaxies suggest that they have largely completed their formation, their size is found to be typically smaller that similarly massive early-type galaxies in the local Universe, in agreement with many high-redshift studies. This would leave room for later evolution, likely through non-secular processes, changing their structure to match their local counterparts. On the other hand, uncertainties and biases in the determination of masses and sizes, as well as in the local mass-size relation, and the possible effect of progenitor bias, still hamper a final conclusion on the actual relevance of size evolution for early-type galaxies in this dense high-redshift environment.

scholarly journals First core properties: from low- to high-mass star formation

2018 ◽  
Vol 618 ◽  
pp. A95 ◽  
Author(s):  
Asmita Bhandare ◽  
Rolf Kuiper ◽  
Thomas Henning ◽  
Christian Fendt ◽  
Gabriel-Dominique Marleau ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Star Formation ◽  
Molecular Cloud ◽  
Radiation Transport ◽  
High Mass ◽  
Mass Star ◽  
Intermediate Mass ◽  
Wide Range ◽  
Low Mass ◽  
Cloud Core

Aims. In this study, the main goal is to understand the molecular cloud core collapse through the stages of first and second hydrostatic core formation. We investigate the properties of Larsons first and second cores following the evolution of the molecular cloud core until the formation of Larson’s cores. We expand these collapse studies for the first time to span a wide range of initial cloud masses from 0.5 to 100 M⊙. Methods. Understanding the complexity of the numerous physical processes involved in the very early stages of star formation requires detailed thermodynamical modelling in terms of radiation transport and phase transitions. For this we used a realistic gas equation of state via a density- and temperature-dependent adiabatic index and mean molecular weight to model the phase transitions. We used a grey treatment of radiative transfer coupled with hydrodynamics to simulate Larsons collapse in spherical symmetry. Results. We reveal a dependence of a variety of first core properties on the initial cloud mass. The first core radius and mass increase from the low-mass to intermediate-mass regime and decrease from the intermediate-mass to high-mass regime. The lifetime of first cores strongly decreases towards the intermediate- and high-mass regimes. Conclusions. Our studies show the presence of a transition region in the intermediate-mass regime. Low-mass protostars tend to evolve through two distinct stages of formation that are related to the first and second hydrostatic cores. In contrast, in the high-mass star formation regime, collapsing cloud cores rapidly evolve through the first collapse phase and essentially immediately form Larson’s second cores.

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