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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Alma imaging and gravitational lens models of south pole telescope—selected dusty, star-forming galaxies at high redshifts

The South Pole Telescope has discovered 100 gravitationally lensed, high-redshift, dusty, star-forming galaxies (DSFGs). We present 0.″5 resolution 870 μm Atacama Large Millimeter/submillimeter Array imaging of a sample of 47 DSFGs spanning z=1.9--5.7, and construct gravitational lens models of these sources. Our visibility-based lens modeling incorporates several sources of residual interferometric calibration uncertainty, allowing us to properly account for noise in the observations. At least 70% of the sources are strongly lensed by foreground galaxies (μ{sub 870μm}>2), with a median magnification of μ{sub 870μm}=6.3, extending to μ{sub 870μm}>30. We compare the intrinsic size distribution of the strongly lensed sources to a similar number of unlensed DSFGs and find no significant differences in spite of a bias between the magnification and intrinsic source size. This may indicate that the true size distribution of DSFGs is relatively narrow. We use the source sizes to constrain the wavelength at which the dust optical depth is unity and find this wavelength to be correlated with the dust temperature. This correlation leads to discrepancies in dust mass estimates of a factor of two compared to estimates using a single value for this wavelength. We investigate the relationship between the [C ii] line and the far-infrared luminosity and find that the same correlation between the [C ii]/L{sub FIR} ratio and Σ{sub FIR} found for low-redshift star-forming galaxies applies to high-redshift galaxies and extends at least two orders of magnitude higher in Σ{sub FIR}. This lends further credence to the claim that the compactness of the IR-emitting region is the controlling parameter in establishing the “[C ii] deficit.”.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

The role of the Kozai-Lidov mechanism in black hole binary mergers in galactic centers

In order to understand the rate of merger of stellar mass black hole binaries (BHBs) by gravitational wave (GW) emission it is important to determine the major pathways to merger. We use numerical simulations to explore the evolution of BHBs inside the radius of influence of supermassive black holes (SMBHs) in galactic centers. In this region, the evolution of binaries is dominated by perturbations from the central SMBH. In particular, as first pointed out by Antonini and Perets, the Kozai–Lidov mechanism trades relative inclination of the BHB to the SMBH for eccentricity of the BHB, and for some orientations can bring the BHB to an eccentricity near unity. At very high eccentricities, GW emission from the BHB can become efficient, causing the members of the BHB to coalesce. We use a novel combination of two N-body codes to follow this evolution. We are required to simulate small systems to follow the behavior accurately. We have completed 400 simulations that range from ∼300 stars around a 10{sup 3} M{sub ⊙} black hole to ∼4500 stars around a 10{sup 4} M{sub ⊙} black hole. These simulations are the first to follow the internal orbit of a binary near an SMBH while also following the changes to its external orbit self-consistently. We find that this mechanism could produce mergers at a maximum rate per volume of ∼100 Gpc{sup −3} yr{sup −1} or considerably less if the inclination oscillations of the binary remain constant as the BHB inclination to the SMBH changes, or if the binary black hole fraction is small.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

THE BARYON CYCLE AT HIGH REDSHIFTS: EFFECTS OF GALACTIC WINDS ON GALAXY EVOLUTION IN OVERDENSE AND AVERAGE REGIONS

We employ high-resolution cosmological zoom-in simulations focusing on a high-sigma peak and an average cosmological field at z ∼ 6–12 in order to investigate the influence of environment and baryonic feedback on galaxy evolution in the reionization epoch. Strong feedback, e.g., galactic winds, caused by elevated star formation rates (SFRs) is expected to play an important role in this evolution. We compare different outflow prescriptions: (i) constant wind velocity (CW), (ii) variable wind scaling with galaxy properties (VW), and (iii) no outflows (NW). The overdensity leads to accelerated evolution of dark matter and baryonic structures, absent from the “normal” region, and to shallow galaxy stellar mass functions at the low-mass end. Although CW shows little dependence on the environment, the more physically motivated VW model does exhibit this effect. In addition, VW can reproduce the observed specific SFR (sSFR) and the sSFR–stellar mass relation, which CW and NW fail to satisfy simultaneously. Winds also differ substantially in affecting the state of the intergalactic medium (IGM). The difference lies in the volume-filling factor of hot, high-metallicity gas, which is near unity for CW, while such gas remains confined in massive filaments for VW, and locked up in galaxies for NW. Such gas is nearly absent from the normal region. Although all wind models suffer from deficiencies, the VW model seems to be promising in correlating the outflow properties with those of host galaxies. Further constraints on the state of the IGM at high z are needed to separate different wind models.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Compressible flow in front of an axisymmetric blunt object: analytic approximation and astrophysical implications

Compressible flows around blunt objects have diverse applications, but current analytic treatments are inaccurate and limited to narrow parameter regimes. We show that the gas-dynamic flow in front of an axisymmetric blunt body is accurately derived analytically using a low order expansion of the perpendicular gradients in terms of the parallel velocity. This reproduces both subsonic and supersonic flows measured and simulated for a sphere, including the transonic regime and the bow shock properties. Some astrophysical implications are outlined, in particular for planets in the solar wind and for clumps and bubbles in the intergalactic medium. The bow shock standoff distance normalized by the obstacle curvature is ∼2/(3g) in the strong shock limit, where g is the compression ratio. For a subsonic Mach number M approaching unity, the thickness δ of an initially weak, draped magnetic layer is a few times larger than in the incompressible limit, with amplification ∼(1+1.3M{sup 2.6})/(3δ).

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

HYDROCARBON EMISSION RINGS IN PROTOPLANETARY DISKS INDUCED BY DUST EVOLUTION

We report observations of resolved C{sub 2}H emission rings within the gas-rich protoplanetary disks of TW Hya and DM Tau using the Atacama Large Millimeter Array. In each case the emission ring is found to arise at the edge of the observable disk of millimeter-sized grains (pebbles) traced by submillimeter-wave continuum emission. In addition, we detect a C{sub 3}H{sub 2} emission ring with an identical spatial distribution to C{sub 2}H in the TW Hya disk. This suggests that these are hydrocarbon rings (i.e., not limited to C{sub 2}H). Using a detailed thermo-chemical model we show that reproducing the emission from C{sub 2}H requires a strong UV field and C/O > 1 in the upper disk atmosphere and outer disk, beyond the edge of the pebble disk. This naturally arises in a disk where the ice-coated dust mass is spatially stratified due to the combined effects of coagulation, gravitational settling and drift. This stratification causes the disk surface and outer disk to have a greater permeability to UV photons. Furthermore the concentration of ices that transport key volatile carriers of oxygen and carbon in the midplane, along with photochemical erosion of CO, leads to an elemental C/O ratio that exceeds unity in the UV-dominated disk. Thus the motions of the grains, and not the gas, lead to a rich hydrocarbon chemistry in disk surface layers and in the outer disk midplane.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

A study of the relation between star formation and molecular clumps on subparsec scales in 30 Doradus

We present {sup 12}CO and {sup 13}CO molecular gas data observed by ALMA, massive early-stage young stellar objects (YSOs) identified by applying color–magnitude cuts to Spitzer and Herschel photometry, and low-mass late-stage YSOs identified via Hα excess. Using dendrograms, we derive properties for the molecular cloud structures. This is the first time a dendrogram analysis has been applied to extragalactic clouds. The majority of clumps have a virial parameter equal to unity or less. The size–linewidth relations of {sup 12}CO and {sup 13}CO show the clumps in this study have a larger linewidth for a given size (by factors of 3.8 and 2.5, respectively) in comparison to several, but not all, previous studies. The larger linewidths in 30 Doradus compared to typical Milky Way quiescent clumps are probably due to the former’s highly energetic environmental conditions. The slopes of the size–linewidth relations of {sup 12}CO, 0.65 ± 0.04, and {sup 13}CO, 0.97 ± 0.12, are on the higher end but consistent within 3σ of those of previous studies. Massive star formation occurs in clumps with high masses (>1.83 × 10{sup 2} M {sub ⊙}), high linewidths (v > 1.18 km s{sup −1}), and high mass densities (>6.67 × 10{sup 2} M {sub ⊙} pc{sup −2}). The majority of embedded, massive YSOs are associated with a clump; however, the majority of more evolved, low-mass YSOs are not.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

DENSITY-MAGNETIC FIELD CORRELATION IN MAGNETOHYDRODYNAMIC TURBULENCE DRIVEN BY DIFFERENT DRIVING SCHEMES WITH DIFFERENT CORRELATION TIMES

Turbulent motions naturally produce density and magnetic-field fluctuations. Correlation between the two fluctuations is important for interpretation of observations, such as observations of the rotation measure (RM). In this paper, we study the effect of driving schemes on the density-magnetic-field correlation. In particular, we numerically investigate how the correlation time of driving affects the correlation between density and magnetic field. We perform compressible magnetohydrodynamic turbulence simulations at different sonic Mach numbers ( M {sub s} ), using two different driving schemes—a finite-correlated driving and a delta-correlated driving. In the former, the forcing vectors change continuously with a correlation time comparable to the large-eddy turnover time. In the latter, the direction (and amplitude) of driving changes in a very short timescale. The finite-correlated driving results in strong anti-correlation between two fields when the sonic and the Alfvénic Mach numbers are similar to unity (i.e., when M {sub s} ∼ 1 and M {sub A} ∼ 1, respectively). However, the anti-correlation becomes weaker and approaches zero for higher values of M {sub s} or M {sub A}. The delta-correlated driving produces virtually no correlation between two fields when M {sub s} ∼ 1 and M {sub A} ∼ 1, and produces more and more positive correlations as M {sub s} or M {sub A} increases. We conjecture that two competing effects, tendency for achieving balance between the gas and the magnetic pressure and simultaneous compression of fluid and magnetic field, determine the correlation behavior. We also investigate how different driving schemes affect the Probability Density Function of three-dimensional density, dispersion measure, and RM.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

NUMERICAL SIMULATIONS OF PLASMA DYNAMICS IN THE VICINITY OF A RETRACTING FLUX TUBE

In a previous paper, we presented an analytical, zero- β model for supra-arcade downflows in which a retracting flux tube deforms the surrounding magnetic field, constricting the flow of plasma along affected field lines and, in some cases, forcing the plasma to exhibit collimated shocks. Here we present a numerical simulation based on the same model construction—a retracting flux tube is treated as a rigid boundary around which the plasma is forced to flow and the magnetic field and plasma evolve according to the governing equations of magnetohydrodynamics. We find that the collimated shocks described in our previous study are recovered for plasma β in the range of 0 ≤ β ≲ 1, while for 1 ≲ β the behavior is similar to the simpler hydrodynamic case, with classical bow shocks forming when the acoustic Mach number approaches or exceeds unity. Furthermore, we find that while the plasma β is important for identifying the various types of behaviors, more important still is the Alfvén Mach number, which, if large, implies that the bulk kinetic energy of the fluid exceeds the internal energy of the magnetic field, thereby leading to the formation of unconfined, fast-mode magnetosonic shocks, even in the limit of small β .

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Collisionless isotropization of the solar-wind protons by compressive fluctuations and plasma instabilities

Compressive fluctuations are a minor yet significant component of astrophysical plasma turbulence. In the solar wind, long-wavelength compressive slow-mode fluctuations lead to changes in β{sub ∥p}≡8πn{sub p}k{sub B}T{sub ∥p}/B{sup 2} and in R{sub p}≡T{sub ⊥p}/T{sub ∥p}, where T{sub ⊥p} and T{sub ∥p} are the perpendicular and parallel temperatures of the protons, B is the magnetic field strength, and n{sub p} is the proton density. If the amplitude of the compressive fluctuations is large enough, R{sub p} crosses one or more instability thresholds for anisotropy-driven microinstabilities. The enhanced field fluctuations from these microinstabilities scatter the protons so as to reduce the anisotropy of the pressure tensor. We propose that this scattering drives the average value of R{sub p} away from the marginal stability boundary until the fluctuating value of R{sub p} stops crossing the boundary. We model this “fluctuating-anisotropy effect” using linear Vlasov–Maxwell theory to describe the large-scale compressive fluctuations. We argue that this effect can explain why, in the nearly collisionless solar wind, the average value of R{sub p} is close to unity.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

KMOS3D: dynamical constraints on the mass budget in early star-forming disks

We exploit deep integral-field spectroscopic observations with KMOS/Very Large Telescope of 240 star-forming disks at 0.6 2. We conclude that baryons make up most of the mass within the disk regions of high-redshift star-forming disk galaxies, with typical disks at z>2 being strongly baryon-dominated within R {sub e}. Substantial object-to-object variations in both stellar and baryonic mass fractions are observed among the galaxies in our sample, larger than what can be accounted for by the formal uncertainties in their respective measurements. In both cases, the mass fractions correlate most strongly with measures of surface density. High-Σ{sub star} galaxies feature stellar mass fractions closer to unity, and systems with high inferred gas or baryonic surface densities leave less room for additional mass components other than stars and molecular gas. Our findings can be interpreted as more extended disks probing further (and more compact disks probing less far) into the dark matter halos that host them.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

FAR-UV EMISSION PROPERTIES OF FR1 RADIO GALAXIES

The power mechanism and accretion geometry for low-power FR 1 radio galaxies are poorly understood in comparison to those for Seyfert galaxies and QSOs. In this paper, we use the diagnostic power of the Ly α recombination line observed using the Cosmic Origins Spectrograph (COS) aboard the Hubble Space Telescope ( HST ) to investigate the accretion flows in three well-known, nearby FR 1s: M87, NGC 4696, and Hydra A. The Ly α emission line’s luminosity, velocity structure, and the limited knowledge of its spatial extent provided by COS are used to assess conditions within a few parsecs of the supermassive black hole in these radio-mode active galactic nuclei. We observe strong Ly α emission in all three objects with total luminosity similar to that seen in BL Lacertae objects. M87 shows a complicated emission-line profile in Ly α , which varies spatially across the COS aperture and possibly temporally over several epochs of observation. In both NGC 4696 and M87, the Ly α luminosities ∼10{sup 40} erg s{sup -1} are closely consistent with the observed strength of the ionizing continuum in Case B recombination theory and with the assumption of a near-unity covering factor. It is possible that the Ly α -emitting clouds are ionized largely by beamed radiation associated with the jets. Long-slit UV spectroscopy can be used to test this hypothesis. Hydra A and the several BL Lac objects studied in this and previous papers have Ly α luminosities larger than M87 but their extrapolated, nonthermal continua are so luminous that they overpredict the observed strength of Ly α , a clear indicator of relativistic beaming in our direction. Given their substantial space density (∼4 × 10{sup -3} Mpc{sup -3}), the unbeamed Lyman continuum radiation of FR 1s may make a substantial minority contribution (∼10%) to the local UV background if all FR 1s are similar to M87 in ionizing flux level.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Rotational Spectral Unmixing of Exoplanets: Degeneracies between Surface Colors and Geography

Unmixing the disk-integrated spectra of exoplanets provides hints about heterogeneous surfaces that we cannot directly resolve in the foreseeable future. It is particularly important for terrestrial planets with diverse surface compositions like Earth. Although previous work on unmixing the spectra of Earth from disk-integrated multi-band light curves appeared successful, we point out a mathematical degeneracy between the surface colors and their spatial distributions. Nevertheless, useful constraints on the spectral shape of individual surface types may be obtained from the premise that albedo is everywhere between 0 and 1. We demonstrate the degeneracy and the possible constraints using both mock data based on a toy model of Earth, as well as real observations of Earth. Despite the severe degeneracy, we are still able to recover an approximate albedo spectrum for an ocean. In general, we find that surfaces are easier to identify when they cover a large fraction of the planet and when their spectra approach zero or unity in certain bands.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

A Spectroscopic Analysis of the Hyades Cool Giants

High-resolution spectroscopic observations of the four cool giants in the Hyades cluster, taken at the Elginfield Observatory, are analyzed. The velocity of γ Tau between 2002 and 2009 is constant to a few m s{sup −1}; small variations, compatible with the planetary orbit, are seen for ε Tau. The primary-to-secondary mass ratio of θ {sup 1} Tau is found to be 2.33 ± 0.07. Absolute radial velocities are determined for three of the giants from third-signature plots that correct for granulation blueshifts: 38,615 ± 50, 38,760 ± 100, and 38,570 ± 50 m s{sup −1} for γ Tau, δ Tau, and ε Tau respectively. Line–depth ratios show that γ Tau is 33 ± 5 K, δ Tau is 53 ± 10 K, and θ {sup 1} Tau is 30 ± 6 K hotter than ε Tau. Although the λ6253 line bisectors are similar for all four giants, there are significant differences in the line profiles. Fourier analysis of the profile shapes yields projected rotation rates of 2.1, 2.4, 2.8, and 2.8 km s{sup −1} for γ Tau, δ Tau, ε Tau, and θ {sup 1} Tau respectively, with an uncertainty of ±0.3 km s{sup −1}. The corresponding radial–tangential macroturbulence dispersions are 5.07, 5.66, 5.55, and 4.65 km s{sup −1}, with a uncertainty of ±0.10 km s{sup −1}. Scale factors for third-signature plots are close to unity, ±10%, implying that the granulation velocity gradient through their photospheres is similar to the Sun's. Bisector mapping returns flux differences between granules and lanes, with average granule-to-lane temperature differences ∼125 K.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

A Comprehensive Study of Three Early-type Contact Twin Binaries: CT Tau, GU Mon, and V701 Sco

Three eclipsing binaries, CT Tau, GU Mon, and V701 Sco, are early-type contact binaries with infrared excess from circumbinary matter. We present the multi-color photometry for CT Tau and GU Mon, whose spectral types of B1V are identified by the low-precision spectra. Combining these new light curves (LCs) with previously reported LCs and radial velocity curves, we perform a synthesized analysis to estimate/update the stellar absolute parameters of the three systems. Their mass ratios are close to unity (i.e., q ≃ 1), which indicates that the binary system comprising of twin components may be undergoing a slow Case A mass transfer. From the period analysis, the light–time orbit in the (O - C) curve may result from the third condense companion around the binary system although no evidence could be provided by the third light ℓ {sub 3}. From the spectral energy distribution for three binaries, the excess infrared (IR) emissions are above the photospheric emissions, which can be seen at the 22.1 μm for CT Tau and GU Mon, and 11.6 μm, 14.5 μm, and 22.1 μm for V701 Sco, respectively. This kind of infrared excess for the early-type star may be attributed to the circumbinary matter by stellar wind.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Accretion Properties of PDS 70b with MUSE

We report a new evaluation of the accretion properties of PDS 70b obtained with the Very Large Telescope/Multi Unit Spectroscopic Explorer. The main difference from the previous studies of Haffert et al. and Aoyama & Ikoma is in the mass accretion rate. Simultaneous multiple line observations, such as Hα and Hβ, can better constrain the physical properties of an accreting planet. While we clearly detected Hα emissions from PDS 70b, no Hβ emissions were detected. We estimate the line flux of Hβ with a 3σ upper limit to be 2.3 × 10{sup −16} erg s{sup −1} cm{sup −2}. The flux ratio F {sub Hβ}/F {sub Hα} for PDS 70b is <0.28. Numerical investigations by Aoyama et al. suggest that F {sub Hβ}/F {sub Hα} should be close to unity if the extinction is negligible. We attribute the reduction of the flux ratio to the extinction, and estimate the extinction of Hα (A {sub Hα}) for PDS 70b to be >2.0 mag using the interstellar extinction value. By combining with the Hα linewidth and the dereddening line luminosity of Hα, we derive the PDS 70b mass accretion rate to be ≳5 × 10{sup −7} M {sub Jup} yr{sup −1}. The PDS 70b mass accretion rate is an order of magnitude larger than that of PDS 70. We found that the filling factor f {sub f} (the fractional area of the planetary surface emitting Hα) is ≳0.01, which is similar to the typical stellar value. The small value of f {sub f} indicates that the Hα emitting areas are localized at the surface of PDS 70b.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

A Featureless Infrared Transmission Spectrum for the Super-puff Planet Kepler-79d

Extremely low-density planets (“super-puffs”) are a small but intriguing subset of the transiting planet population. With masses in the super-Earth range (1 − 10 M{sub ⊕}) and radii akin to those of giant planets (> 4 R{sub ⊕}), their large envelopes may have been accreted beyond the water snow line and many appear to be susceptible to catastrophic mass loss. Both the presence of water and the importance of mass loss can be explored using transmission spectroscopy. Here, we present new Hubble space telescope WFC3 spectroscopy and updated Kepler transit depth measurements for the super-puff Kepler-79d. We do not detect any molecular absorption features in the 1.1 − 1.7 μm WFC3 bandpass, and the combined Kepler and WFC3 data are consistent with a flat-line model, indicating the presence of aerosols in the atmosphere. We compare the shape of Kepler-79d’s transmission spectrum to predictions from a microphysical haze model that incorporates an outward particle flux due to ongoing mass loss. We find that photochemical hazes offer an attractive explanation for the observed properties of super-puffs like Kepler-79d, as they simultaneously render the near-infrared spectrum featureless and reduce the inferred envelope mass-loss rate by moving the measured radius (optical depth unity surface during transit) to lower pressures. We revisit the broader question of mass-loss rates for super-puffs and find that the age estimates and mass-loss rates for the majority of super-puffs can be reconciled if hazes move the photosphere from the typically assumed pressure of ∼10 mbar to ∼10 μbar.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

BVR{sub c}I{sub c} Observations, Third-body Orbital Study, and Analysis of the UV Leo-type, Pre-W UMA Binary V642 Virginis

V642 Vir is a polar spotted, well-detached, UV Leo-type, low-mass, pre-WUMa (T1 ~ 4250K, ~K6V) eclipsing binary. It was observed in 2020 April, May, and June at the Dark Sky Observatory in North Carolina, USA with the 0.81 m reflector of Appalachian State University. A total of 88 timings were used in our 22-year period study which included 12 Transiting Exoplanet Survey Satellite (TESS) timings. The O - C plots show a low-amplitude oscillation of residuals that points to the existence of an orbiting third body, a dwarf of minimum mass, 0.15 M {sub ⊙} in an eccentric orbit (e = 0.41), with an orbital period of 20.07 yr. The odd light curves of V642 Virginis indicate that it has polar spots similar to UV Leo and the recently published V1023 Per. Its present large polar spot region indicates that it must have a strong magnetic field and that it is synchronously rotating. The BVR{sub c}I{sub c} simultaneous Wilson–Devinney Program solution gives a detached binary (primary and secondary components are underfilling their respective Roche Lobes, with 76% and 78% fill outs respectively). The cool spot region models near the pole of the primary component (centered at 10° colatitude) and is angled toward the secondary component. Its large radius (68°) and T-fact (T{sub spot}/T{sub surface} = 0.69) also attest to the conclusion of the strength of the magnetic field. The small ΔT in the components (~318 K) and mass ratio near unity (0.9542 ± 0.0005) show that the stars are similar in spectral type (secondary ~K9V). The inclination is high, ~86.87 ± 0.04°, yet there is no time of constant light due to the two stars’ essentially equal radii.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Primordial black hole formation in the matter-dominated phase of the universe

We investigate primordial black hole formation in the matter-dominated phase of the universe, where nonspherical effects in gravitational collapse play a crucial role. This is in contrast to the black hole formation in a radiation-dominated era. We apply the Zel’dovich approximation, Thorne’s hoop conjecture, and Doroshkevich’s probability distribution and subsequently derive the production probability β{sub 0} of primordial black holes. The numerical result obtained is applicable even if the density fluctuation σ at horizon entry is of the order of unity. For σ≪1, we find a semi-analytic formula β{sub 0}≃0.05556σ{sup 5}, which is comparable to the Khlopov–Polnarev formula. We find that the production probability in the matter-dominated era is much larger than that in the radiation-dominated era for σ≲0.05, while they are comparable with each other for σ≳0.05. We also discuss how σ can be written in terms of primordial curvature perturbations.

79 ASTRONOMY AND ASTROPHYSICS↗