John N. Bahcall

Bio: John N. Bahcall is an academic researcher from Princeton University. The author has contributed to research in topics: Solar neutrino & Neutrino. The author has an hindex of 94, co-authored 555 publications receiving 33159 citations. Previous affiliations of John N. Bahcall include California Institute of Technology & Space Telescope Science Institute.

High energy neutrinos from cosmological gamma-ray burst fireballs

Abstract: Observations suggest that {gamma}-ray bursts (GRBs) are produced by the dissipation of the kinetic energy of a relativistic fireball. We show that a large fraction, {ge}10{percent}, of the fireball energy is expected to be converted by photomeson production to a burst of {approximately}10{sup 14}eV neutrinos. A km{sup 2} neutrino detector would observe at least several tens of events per year correlated with GRBs, and test for neutrino properties (e.g., flavor oscillations, for which upward moving {tau}{close_quote}s would be a unique signature, and coupling to gravity) with an accuracy many orders of magnitude better than is currently possible. {copyright} {ital 1997} {ital The American Physical Society}

High-energy neutrinos from astrophysical sources: An Upper bound

Abstract: We show that cosmic-ray observations set a model-independent upper bound of ${E}_{\ensuremath{ u}}^{2}{\ensuremath{\Phi}}_{\ensuremath{ u}}l2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}{\mathrm{G}\mathrm{e}\mathrm{V}/\mathrm{c}\mathrm{m}}^{2}\mathrm{}\mathrm{s}\mathrm{}\mathrm{sr}$ to the intensity of high-energy neutrinos produced by photo-meson (or $p\ensuremath{-}p)$ interactions in sources of size not much larger than the proton photo-meson (or $p\ensuremath{-}p)$ mean-free-path. This bound applies, in particular, to neutrino production by either AGN jets or GRBs. The upper limit is two orders of magnitude below the intensity predicted in some popular AGN jet models and therefore contradicts the theory that the cosmic gamma-ray background is due to photo-pion interactions in AGN jets. The upper bound is consistent with our predictions from GRB models. The predicted intensity from GRBs is ${E}^{2}dN/dE\ensuremath{\sim}0.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}{\mathrm{G}\mathrm{e}\mathrm{V}/\mathrm{c}\mathrm{m}}^{2}\mathrm{}\mathrm{s}\mathrm{}\mathrm{sr}$ for ${10}^{14}\mathrm{eV}lEl{10}^{16}\mathrm{eV};$ we also derive the expected intensity at higher energy.

Solar Models: Current Epoch and Time Dependences, Neutrinos, and Helioseismological Properties

Abstract: We calculate accurate solar models and report the detailed time dependences of important solar quantities. We use helioseismology to constrain the luminosity evolution of the Sun and report the discovery of semiconvection in evolved solar models that include diffusion. In addition, we compare the computed sound speeds with the results of p-mode observations by BiSON, GOLF, GONG, LOWL, and MDI instruments. We contrast the neutrino predictions from a set of eight standard-like solar models and four deviant (or deficient) solar models with the results of solar neutrino experiments. For solar neutrino and helioseismological applications, we present present-epoch numerical tabulations of characteristics of the standard solar model as a function of solar radius, including the principal physical and composition variables, sound speeds, neutrino fluxes, and functions needed for calculating solar neutrino oscillations.

The universe at faint magnitudes. I - Models for the galaxy and the predicted star counts

Abstract: A detailed model is constructed for the disk and spheroid components of the Galaxy from which the distribution of visible stars and mass in the Galaxy is calculated. The application of star counts to the determination of galactic structure parameters is demonstrated. The possibility of detecting a halo component with the aid of star counts is also investigated quantitatively.

Star distribution around a massive black hole in a globular cluster.

Abstract: To predict the likely distribution of stars around a massive black hole in the core of a cluster of stars, an equation of the Fokker-Planck type is derived that describes the diffusion of stars in the 1/r gravitational well of the black hole, by star-star gravitational collisions. The main assumptions are: (1) the distribution of stars is described by a single-particle distribution function that is shperically symmetric in coordinate space and approximately isotropic in velocity space; (2) the stars have equal masses; (3) star mass very-much-less-thanblack-hole massvery-much-less-thancluster-core mass; (4) a star is destroyed by star-star collisions or by tidal forces when its binding energy in the well exceeds a specified large value; (5) binaries are unimportant. Numerical solutions for the time-dependent equations indicate that the equilibrium star density, closely approached within a collision time, approximates an r/sup -7///sup 4/ power law throughout most of the well. The same equilibrium power law obtains for nonisotropic distribution functions whose anisotropy is independent of r. Stars in bound orbits about a black hole diffuse slowly into its gravitational well under equilibrium conditions. A black hole of approximately-less-than10/sup 3/ M/sub sun/ may accrete stars primarily by capture from unbound orbits.Theshape of the star distribution more » near the cluster center observed with small diaphragms is predicted. As a function of diaphragm size, the velocity dispersion and line profile that might be measured spectroscopically is calculated. Some calculations are also presented for an open slit configuration. For globular clusters in our Galaxy, one might be able to detect black holes with masses approximately-greater-than5 x 10/sup 3/ M/sub sun/ and, with a large space telescope, masses approximately-greater-than10/sup 3/ M/sub sun/. An approximate formula for the mean distance of a massive black hole from the center of mass of the unbound stars is also presented. (AIP) « less

Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant

Abstract: We present spectral and photometric observations of 10 Type Ia supernovae (SNe Ia) in the redshift range 0.16 " z " 0.62. The luminosity distances of these objects are determined by methods that employ relations between SN Ia luminosity and light curve shape. Combined with previous data from our High-z Supernova Search Team and recent results by Riess et al., this expanded set of 16 high-redshift supernovae and a set of 34 nearby supernovae are used to place constraints on the following cosmo- logical parameters: the Hubble constant the mass density the cosmological constant (i.e., the (H 0 ), () M ), vacuum energy density, the deceleration parameter and the dynamical age of the universe ) " ), (q 0 ), ) M \ 1) methods. We estimate the dynamical age of the universe to be 14.2 ^ 1.7 Gyr including systematic uncer- tainties in the current Cepheid distance scale. We estimate the likely e†ect of several sources of system- atic error, including progenitor and metallicity evolution, extinction, sample selection bias, local perturbations in the expansion rate, gravitational lensing, and sample contamination. Presently, none of these e†ects appear to reconcile the data with and ) " \ 0 q 0 " 0.

The Two Micron All Sky Survey (2MASS)

Abstract: Between 1997 June and 2001 February the Two Micron All Sky Survey (2MASS) collected 25.4 Tbytes of raw imagingdatacovering99.998%ofthecelestialsphereinthenear-infraredJ(1.25 � m),H(1.65 � m),andKs(2.16 � m) bandpasses. Observations were conducted from two dedicated 1.3 m diameter telescopes located at Mount Hopkins, Arizona,andCerroTololo,Chile.The7.8sofintegrationtimeaccumulatedforeachpointontheskyandstrictquality control yielded a 10 � point-source detection level of better than 15.8, 15.1, and 14.3 mag at the J, H, and Ks bands, respectively, for virtually the entire sky. Bright source extractions have 1 � photometric uncertainty of <0.03 mag and astrometric accuracy of order 100 mas. Calibration offsets between any two points in the sky are <0.02 mag. The 2MASS All-Sky Data Release includes 4.1 million compressed FITS images covering the entire sky, 471 million source extractions in a Point Source Catalog, and 1.6 million objects identified as extended in an Extended Source Catalog.

Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant To Appear in the Astronomical Journal

Abstract: We present spectral and photometric observations of 10 type Ia supernovae (SNe Ia) in the redshift range 0.16 � z � 0.62. The luminosity distances of these objects are determined by methods that employ relations between SN Ia luminosity and light curve shape. Combined with previous data from our High-Z Supernova Search Team (Garnavich et al. 1998; Schmidt et al. 1998) and Riess et al. (1998a), this expanded set of 16 high-redshift supernovae and a set of 34 nearby supernovae are used to place constraints on the following cosmological parameters: the Hubble constant (H0), the mass density (M), the cosmological constant (i.e., the vacuum energy density, �), the deceleration parameter (q0), and the dynamical age of the Universe (t0). The distances of the high-redshift SNe Ia are, on average, 10% to 15% farther than expected in a low mass density (M = 0.2) Universe without a cosmological constant. Different light curve fitting methods, SN Ia subsamples, and prior constraints unanimously favor eternally expanding models with positive cosmological constant (i.e., � > 0) and a current acceleration of the expansion (i.e., q0 < 0). With no prior constraint on mass density other than M � 0, the spectroscopically confirmed SNe Ia are statistically consistent with q0 < 0 at the 2.8�

First year Wilkinson Microwave Anisotropy Probe (WMAP) observations: Determination of cosmological parameters

Abstract: WMAP precision data enable accurate testing of cosmological models. We find that the emerging standard model of cosmology, a flat � -dominated universe seeded by a nearly scale-invariant adiabatic Gaussian fluctuations, fits the WMAP data. For the WMAP data only, the best-fit parameters are h ¼ 0:72 � 0:05, � bh 2 ¼ 0:024 � 0:001, � mh 2 ¼ 0:14 � 0:02, � ¼ 0:166 þ0:076 � 0:071 , ns ¼ 0:99 � 0:04, and � 8 ¼ 0:9 � 0:1. With parameters fixed only by WMAP data, we can fit finer scale cosmic microwave background (CMB) measure- ments and measurements of large-scale structure (galaxy surveys and the Lyforest). This simple model is also consistent with a host of other astronomical measurements: its inferred age of the universe is consistent with stellar ages, the baryon/photon ratio is consistent with measurements of the (D/H) ratio, and the inferred Hubble constant is consistent with local observations of the expansion rate. We then fit the model parameters to a combination of WMAP data with other finer scale CMB experiments (ACBAR and CBI), 2dFGRS measurements, and Lyforest data to find the model's best-fit cosmological parameters: h ¼ 0:71 þ0:04 � 0:03 , � bh 2 ¼ 0:0224 � 0:0009, � mh 2 ¼ 0:135 þ0:008 � 0:009 , � ¼ 0:17 � 0:06, ns(0.05 Mpc � 1 )=0 :93 � 0:03, and � 8 ¼ 0:84 � 0:04. WMAP's best determination of � ¼ 0:17 � 0:04 arises directly from the temperature- polarization (TE) data and not from this model fit, but they are consistent. These parameters imply that the age of the universe is 13:7 � 0:2 Gyr. With the Lyforest data, the model favors but does not require a slowly varying spectral index. The significance of this running index is sensitive to the uncertainties in the Ly� forest. By combining WMAP data with other astronomical data, we constrain the geometry of the universe, � tot ¼ 1:02 � 0:02, and the equation of state of the dark energy, w < � 0:78 (95% confidence limit assuming w �� 1). The combination of WMAP and 2dFGRS data constrains the energy density in stable neutrinos: � � h 2 < 0:0072 (95% confidence limit). For three degenerate neutrino species, this limit implies that their mass is less than 0.23 eV (95% confidence limit). The WMAP detection of early reionization rules out warm dark matter. Subject headings: cosmic microwave background — cosmological parameters — cosmology: observations — early universe On-line material: color figure