A5012467340- Galaxies: Formation, Evolution, Phenomena
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astrophysical Phenomena and Observations
- Dark Matter and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Pulsars and Gravitational Waves Research
- Adaptive optics and wavefront sensing
- Heat Transfer Mechanisms
- Scientific Research and Discoveries
- Astronomical Observations and Instrumentation
- Laser-Plasma Interactions and Diagnostics
- History and Developments in Astronomy
- Solar and Space Plasma Dynamics
- CCD and CMOS Imaging Sensors
- High-pressure geophysics and materials
- Light effects on plants
- Optical Polarization and Ellipsometry
- Particle Detector Development and Performance
- Relativity and Gravitational Theory
- Semiconductor Lasers and Optical Devices
University of Maryland, College Park
2016-2025
University of Sussex
2024
Sorbonne Université
2013-2014
Université Paris Cité
2013
Institute of Astronomy
2003-2005
University of Colorado Boulder
2002-2003
Laboratory for Atmospheric and Space Physics
1999-2002
University of Florence
1997
We investigate the effect of nonevaporating primordial black holes (PBHs) on ionization and thermal history universe. X-rays emitted by gas accretion onto PBHs modify cosmic recombination history, producing measurable effects spectrum anisotropies microwave background (CMB). Using third-year WMAP data COBE FIRAS we improve existing upper limits abundance with masses >0.1 M☉ several orders magnitude. The new still allow to be important for origin supermassive ultraluminous X-ray sources....
Abstract The Cosmic Gems arc is among the brightest and highly magnified galaxies observed at redshift z ≈ 10.2 (ref. 1 ). However, it an intrinsically ultraviolet faint galaxy, in range of those now thought to drive reionization Universe 2–4 . Hitherto smallest features resolved a galaxy comparable are between few hundreds tens parsecs (pc) 5,6 Here we report JWST observations Gems. light into five star clusters located region smaller than 70 pc. They exhibit minimal dust attenuation low...
Abstract We present JWST/NIRSpec prism spectroscopy of MACS0647−JD, a triply lensed z ∼ 11 candidate discovered in Hubble Space Telescope imaging and spatially resolved by JWST into two components, A B. Spectroscopy component yields spectroscopic redshift = 10.17 based on seven detected emission lines: C iii ] λ 1907, 1909, [O ii 3727, [Ne 3869, 3968, H δ 4101, γ 4340, 4363. These are the second-most distant detections these lines to date, galaxy observed just 460 million years after Big...
We develop a method to extract the "effective equation of state" intergalactic medium from Doppler (b) parameter distribution low-density Lyα forest. test on numerical simulations and then apply it published observations forest at redshifts z ≃ 0-4. find that effective state is close isothermal redshift ~ 3, indicating second reheating took place 3. This can plausibly be identified with reionization He II observed occur
We compare the properties of dwarf galaxies in Local Group with simulated formed before reionization a cosmological simulation unprecedented spatial and mass resolution,including radiative feedback effects. find that subset dwarfs are remarkably similar to all their already reionization. Based on this similarity, we propose hypothesis form variety ways: some them ``true fossils'' pre-reionization era, most stars later, after (we call ``survivors'' era), rest an intermediate group ``polluted...
We investigate the possibility that there is a first phase of partial ionisation due to X-rays produced by black hole accretion in small-mass galaxies at redshifts 7
We argue that, at least a fraction of the newly discovered population ultra-faint dwarf spheroidal galaxies in Local Group constitute fossil relic once ubiquitous formed before reionization with circular velocities smaller than $v_{c}^{cr} \sim 20$ km/s. present several arguments support this model. The number luminous Milky Way satellites inferred from observations is larger estimated dark halos Galaxy that have, or had past, velocity $>v_{c}^{cr}$, as predicted by "Via Lactea" simulation....
We have conducted N-body simulations of the growth Milky Way-sized halos in cold and warm dark matter cosmologies. The number satellites our simulated Ways decreases with decreasing mass particle. Assuming that exceeds or equals observed Way we derive lower limits on particle mass. find 95% confidence m_s > 13.3 keV for a sterile neutrino produced by Dodelson Widrow mechanism, 8.9 Shi Fuller 3.0 Higgs decay m_{WDM} 2.3 thermal recent discovery many new dominated Sloan Digital Sky Survey...
This paper, the second of a series on radiation-regulated accretion onto black holes (BHs) from galactic scales, focuses effects radiation pressure and angular momentum accreting gas. We simulate intermediate-mass holes, but we derive general scaling relationships that are solutions Bondi problem with feedback valid for any mass BH $M_{\rm bh}$. Thermal ionized sphere around regulates rate producing periodic short-lived luminosity bursts. find ambient gas densities exceeding $n^{\rm cr}_{\rm...
ABSTRACT Standard models of structure formation allow us to predict the cosmic timescales relevant for onset star and assembly history galaxies at high redshifts (z > 10). The strength Balmer break represents a well-known diagnostic age galaxies, which enables compare observations with contemporary simulations – thus shedding light on predictive power our current in early Universe. Here, we measure 23 spectroscopically confirmed 6 ≲ z 12 using public JWST NIRSpec data from cycle 1 GO...
We present a detailed JWST/NIRSpec and NIRCam analysis of gravitationally lensed galaxy ( μ = 17 − 21) at redshift 6.14 magnified by the Hubble Frontier Field cluster MACS J0416. The target is typical compact UV-faint M UV −17.8) Lyman- α emitter, yet large magnification allows characterization structures on sub-galactic scales (down to few parsecs). Prominent optical H , β [O III ] λλ 4959, 5007 lines are spatially resolved with high-spectral-resolution grating (G395H, R 2700), equivalent...
We use one-dimensional radiative transfer simulations to study the evolution of H2 gas-phase (H- catalyzed) formation and photodissociation regions in primordial universe. find a new positive feedback mechanism capable producing shells intergalactic medium (IGM), which are optically thick some Lyman-Werner bands. While these exist, this effect is important reducing dissociating background flux size spheres around each luminous object. The maximum opacity IGM bands τ ≈ 1-2 for relic molecular...
We use three-dimensional cosmological simulations with radiative transfer to study the formation and evolution of first galaxies in a ΛCDM cosmology. The include continuum using optically thin variable Eddington tensor (OTVET) approximation line H2 Lyman-Werner bands UV background radiation. Chemical thermal processes are treated detail, particularly ones relevant for destruction. find that luminous objects ("small-halo objects") characterized by bursting star (SF) is self-regulated feedback...
We study the effect of radiative feedback on accretion onto intermediate-mass black holes (IMBHs) using hydrodynamical code ZEUS-MP with a transfer algorithm. In this paper, first series, we assume from uniformly dense gas zero angular momentum and extremely low metallicity. Our one-dimensional (1D) 2D simulations explore how X-ray UV radiation emitted near hole regulates supply large scales. Both 1D show similar rates periods between peaks in accretion, meaning that hydro-instabilities...
We use a new set of cold dark matter simulations the local universe to investigate distribution fossils primordial dwarf galaxies within and around Milky Way. Throughout, we build upon previous results showing agreement between observed stellar properties subset ultra-faint dwarfs our simulated fossils. Here, show that first have galactocentric distributions cumulative luminosity functions consistent with observations. In model, predict ∼300 luminous satellites orbiting Way, 50%–70% which...
We propose the existence of ultracompact minihalos as a new type massive compact halo object (MACHO) and suggest an observational test to discover them. These MACHOs are powerful probe into nature dark matter physics in high energy Universe. Non-Gaussian energy-density fluctuations produced at phase transitions (e.g., QCD) or by features inflaton potential can trigger primordial black hole (PBH) formation if their amplitudes delta > 30%. show that PBH accumulates over time sufficiently...
ABSTRACT In this paper, the first in a series on galaxy formation before reionization, we focus understanding what determines size and morphology of stellar objects low-mass galaxies, using parsec-scale cosmological simulations performed with an adaptive mesh hydrodynamics code. Although dense gas which stars are formed tends to have disk structure, found spheroids little rotation. Halos masses between <?CDATA ${10}^{6}\,{M}_{\odot }$?> $5\times {10}^{8}\,{M}_{\odot form stochastically,...
If primordial black holes of $\mathcal{O}(1-100) M_{\odot}$ constitute a significant portion the dark matter in Universe, they should be very abundant our Galaxy. We present here detailed analysis radio and X-ray emission that these objects are expected to produce due accretion gas from interstellar medium. With respect previous studies, we relax assumption monochromatic mass function, introduce an improved treatment physics onto isolated, moving compact objects, based on set...
We present JWST/NIRSpec prism spectroscopy of MACS0647-JD, the triply-lensed $z \sim 11$ candidate discovered in HST imaging and spatially resolved by JWST into two components A B. Spectroscopy component yields a spectroscopic redshift $z=10.17$ based on 7 detected emission lines: CIII] $\lambda\lambda$1907,1909, [OII] $\lambda$3727, [NeIII] $\lambda$3869, $\lambda$3968, H$\delta$ $\lambda$4101, H$\gamma$ $\lambda$4340, [OIII] $\lambda$4363. These are second-most distant detections these...
We present JWST/Near Infrared Spectrograph (NIRSpec) integral field spectroscopy (IFS) of a lensed Population III candidate stellar complex (dubbed Lensed And Pristine 1, LAP1), with lensing-corrected mass ≲10 4 M ⊙ and an absolute luminosity UV > −11.2 ( m 35.6), confirmed at redshift 6.639 ± 0.004. The system is strongly amplified μ ≳ 100) by straddling critical line the Hubble Frontier Field galaxy cluster MACS J0416. Although continuum currently not detected in Camera (NIRCam) Near...
JWST observations of galaxies at $z\gtrsim 8$ suggest that they are more luminous and clumpier than predicted by most models, prompting several proposals on the physics star formation feedback in first galaxies. In this paper, we focus role ultraviolet (UV) radiation regulating performing a set cosmological hydrodynamics simulations one galaxy sub-pc resolution with different radiative models. We find suppression cooling far UV (FUV) (i.e., $\mathrm{H_2}$ dissociating radiation) from Pop II...
In cold dark matter (CDM) cosmogonies, low-mass objects play an important role in the evolution of universe. Not only are they first luminous to shed light a previously universe, but if their formation is not inhibited by own feedback, dominate galaxy mass function until redshift z ~ 5. this paper we present and discuss implementation three-dimensional cosmological code that includes most needed physics simulate galaxies with self-consistent treatment radiative feedback. The simulation...
I compare the density profile of dark matter (DM) halos in cold (CDM) N-body simulations with 1 Mpc, 32 256 Mpc and 1024 box sizes. In dimensionless units differ only for initial power spectrum perturbations. profiles when most massive are composed about 10^5 DM particles. The show systematically shallower cores respect to corresponding simulation that have masses, M_{dm}, typical Milky Way fitted by a NFW profile. consistent having steeper than simulation, but higher mass resolution needed...
This paper presents a study of quasi-steady spherical accretion in the early Universe, before formation first stars and galaxies. The main motivation is to derive basic formulas that will be used companion calculate luminosity primordial black holes their effect on cosmic ionization history. following cosmological effects are investigated: coupling gas CMB photon fluid (i.e., Compton drag), Hubble expansion, growth dark matter halo seeded by gravitational potential central point mass....