A5086780511- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Astrophysical Phenomena and Observations
- Cosmology and Gravitation Theories
- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- History and Developments in Astronomy
- Pulsars and Gravitational Waves Research
- Dark Matter and Cosmic Phenomena
- Adaptive optics and wavefront sensing
- Scientific Research and Discoveries
- Astronomical Observations and Instrumentation
- Relativity and Gravitational Theory
- Solar and Space Plasma Dynamics
- Black Holes and Theoretical Physics
- Superconducting and THz Device Technology
- Geophysics and Gravity Measurements
- CCD and CMOS Imaging Sensors
- Advanced Chemical Physics Studies
- Historical Astronomy and Related Studies
- Atmospheric Ozone and Climate
The University of Texas at Austin
2015-2024
Harvard University Press
2003-2022
Seoul National University
2016
Tohoku University
2016
Max Planck Institute for Astrophysics
2010-2012
Heidelberg University
2010
University of Cologne
2010
Harvard University
1997-2007
University of Cambridge
2002-2006
Center for Astrophysics Harvard & Smithsonian
2002-2006
To constrain the nature of very first stars, we investigate collapse and fragmentation primordial, metal-free gas clouds. We explore physics primordial star formation by means three-dimensional simulations dark matter components, using smoothed particle hydrodynamics, under a wide range initial conditions, including spin, total mass halo, redshift virialization, power spectrum DM fluctuations, presence HD cooling, number particles employed in simulation. find characteristic values for...
▪ Abstract We review recent theoretical results on the formation of first stars in universe, and emphasize related open questions. In particular, we discuss initial conditions for Population III star formation, as given by variants cold dark matter cosmology. Numerical simulations have investigated collapse fragmentation metal-free gas, showing that were predominantly very massive. The exact determination stellar masses, precise form primordial mass function, is still hampered our limited...
We present results from the largest numerical simulation of star formation to resolve fragmentation process down opacity limit. The follows collapse and a large-scale turbulent molecular cloud form stellar cluster and, simultaneously, circumstellar discs binary stars. This large range scales enables us predict wide variety properties for comparison with observations. calculation clearly demonstrates that is highly-dynamic chaotic process. Star-disc encounters binaries truncate discs. Stellar...
We consider the physical conditions under which supermassive black holes could have formed inside first galaxies. Our smoothed particle hydrodynamics simulations indicate that metal-free galaxies with a virial temperature of ~104 K and suppressed H2 formation (due to an intergalactic UV background) tend form binary hole system contains substantial fraction (≳10%) total baryonic mass host galaxy. Fragmentation into stars is without cooling. follow condensation ~5 × 106 M☉ around two centers...
The cosmic dark ages ended a few hundred million years after the big bang, when first stars began to fill universe with new light. It has generally been argued that these formed in isolation and were extremely massive—perhaps 100 times as massive Sun. In recent study, Clark collaborators showed this picture requires revision. They demonstrated accretion disks build up around Population III are strongly susceptible fragmentation should therefore form clusters rather than isolation. We here...
In order to constrain the initial mass function of first generation stars (Population III), we investigate fragmentation properties metal-free gas in context a hierarchical model structure formation. We evolution an isolated 3 σ peak 2 × 106 M☉ that collapses at zcoll ≃ 30 using smoothed particle hydrodynamics. find dissipatively settles into rotationally supported disk has very filamentary morphology. The these filaments is Jeans unstable with MJ ~ 103 M☉. Fragmentation leads formation...
We discuss the formation of supermassive black holes in early universe, and how to probe their subsequent evolution with upcoming mm/sub‐mm telescope ALMA. first focus on chemical radiative conditions for hole formation, particular considering radiation trapping molecular dissociation effects. then turn our attention towards magnetic properties halos where form, show that presence turbulence may lead a dynamo, which could support process by providing an efficient means transporting angular...
The very first stars to form in the Universe heralded an end cosmic dark ages and introduced new physical processes that shaped early evolution. Until now, it was thought these lived short, solitary lives, with only one extremely massive star, or possibly a wide binary system, forming each matter minihalo. Here we describe numerical simulations show were, contrary, often members of tight multiple systems. Our results disks formed around young were unstable gravitational fragmentation,...
We review our current understanding of how the first galaxies formed at end cosmic dark ages, a few 100 million years after Big Bang. Modern large telescopes discovered redshifts greater than seven, whereas theoretical studies have just reached degree sophistication necessary to make meaningful predictions. A crucial ingredient is feedback exerted by generation stars, through UV radiation, supernova blast waves, and chemical enrichment. The key goal derive signature be observed with upcoming...
We investigate the formation of metal-free, Population III (Pop III), stars within a minihalo at z≃ 20 with smoothed particle hydrodynamics (SPH) simulation, starting from cosmological initial conditions. Employing hierarchical, zoom-in procedure, we achieve sufficient numerical resolution to follow collapsing gas in centre up number densities 1012 cm−3. This allows us study protostellar accretion on hydrostatic core, which represent as growing sink particle, improved physical detail. The...
Abstract We present an investigation into the first 500 Myr of galaxy evolution from Cosmic Evolution Early Release Science (CEERS) survey. CEERS, one 13 JWST ERS programs, targets formation z ∼ 0.5 to >10 using several imaging and spectroscopic modes. make use epoch CEERS NIRCam imaging, spanning 35.5 arcmin 2 , search for candidate galaxies at > 9. Following a detailed data reduction process implementing custom steps produce high-quality reduced images, we perform multiband...
We investigate the formation of first stars at end cosmic dark ages with a suite three-dimensional, moving-mesh simulations that directly resolve collapse gas beyond protostar centre matter minihalo. The cover more than 25 orders magnitude in density and have maximum spatial resolution 0.05 R⊙, which extends well below radius individual protostars captures their interaction surrounding gas. In analogy to previous studies employed sink particles, we find Keplerian disc around primary...
Understanding the formation of first stars is one frontier topics in modern astrophysics and cosmology. Their emergence signaled end cosmic dark ages, a few hundred million years after Big Bang, leading to fundamental transformation early Universe through production ionizing photons initial enrichment with heavy chemical elements. We here review state our knowledge, separating well understood elements emerging picture from those where more work required. Primordial star unique that its...
We report results from numerical simulations of star formation in the early universe that focus on dynamical behavior metal-free gas under different initial and environmental conditions. In particular we investigate role turbulence, which is thought to ubiquitously accompany collapse high-redshift halos. distinguish between two main cases: birth Population III.1 stars - those form pristine halos unaffected by prior III.2 forming where still metal free but has an increased ionization...
We report the discovery of a candidate galaxy with photo-z z~12 in first epoch JWST Cosmic Evolution Early Release Science (CEERS) Survey. Following conservative selection criteria we identify source robust z_phot = 11.8^+0.3_-0.2 (1-sigma uncertainty) m_F200W=27.3, and >7-sigma detections five filters. The is not detected at lambda < 1.4um deep imaging from both HST JWST, has faint ~3-sigma F150W F160W, which signal Ly-alpha break near red edge filters, implying z~12. This object (Maisie's...
We simulate the growth of a Population III stellar system, starting from cosmological initial conditions at z = 100. follow formation minihalo and subsequent collapse its central gas to high densities, resolving scales as small ∼ 1 au. Using sink particles represent growing protostars, we model photodissociating ionizing region around first sink, continuing simulation for ∼5000 yr after protostar formation. Along with first-forming several tens secondary sinks form before an ionization front...
Abstract We report the discovery of an accreting supermassive black hole at z = 8.679. This galaxy, denoted here as CEERS_1019, was previously discovered a Ly α -break galaxy by Hubble with redshift from Keck. As part Cosmic Evolution Early Release Science (CEERS) survey, we have observed this source JWST/NIRSpec, MIRI, NIRCam, and NIRCam/WFSS uncovered plethora emission lines. The H β line is best fit narrow plus broad component, where latter measured 2.5 σ FWHM ∼1200 km s −1 . conclude...
Recent observations with JWST have identified several bright galaxy candidates at $z\gtrsim 10$, some of which appear unusually massive (up to $\sim 10^{11}\ \rm M_{\odot}$). Such early formation galaxies is difficult reconcile standard $\Lambda\rm CDM$ predictions, demanding very high star efficiency (SFE), possibly even in excess the cosmic baryon mass budget collapsed structures. With an idealized analysis based on linear perturbation theory and Press-Schechter formalism, we show that...
Abstract We present a sample of 88 candidate z ∼ 8.5–14.5 galaxies selected from the completed NIRCam imaging Cosmic Evolution Early Release Science survey. These data cover ∼90 arcmin 2 (10 pointings) in six broadband filters and one medium-band filter. With this we confirm at higher confidence early JWST conclusions that bright epoch are more abundant than predicted by most theoretical models. construct rest-frame ultraviolet luminosity functions 9, 11, 14 show space density ( M UV = −20)...
Abstract Recent findings from photometric and spectroscopic JWST surveys have identified examples of high-redshift galaxies at z ≳ 10. These high- appear to form much earlier exhibit greater UV luminosity than predicted by theoretical work. In this study, our goal is reproduce the brightness these sources simulating with virial masses M vir = 10 9 –10 ⊙ > To achieve this, we conduct cosmological hydrodynamic zoom-in simulations, modifying baryonic subgrid physics, post-process simulation...
We calculate the generic spectral signature of an early population massive stars at high redshifts. For metal-free with mass above 300 M☉, we find that combined luminosity per unit stellar is almost independent distribution these stars. To zeroth order, spectrum resembles a blackbody effective temperature ~105 K, making highly efficient ionizing hydrogen and helium. The production rate radiation by more than ~300 M☉ larger ~1 order magnitude for He I ~2 orders II emission from standard...
We present results from the first hydrodynamical star formation calculation to demonstrate that brown dwarfs are a natural and frequent product of collapse fragmentation turbulent molecular cloud. The form via dense gas in unstable multiple systems ejected before they have been able accrete stellar masses. Thus, can be viewed as 'failed stars'. Approximately three-quarters gravitationally circumstellar discs while remainder collapsing filaments gas. These mechanisms very efficient, producing...