J. Frieman
A5021421082- Galaxies: Formation, Evolution, Phenomena
- Gamma-ray bursts and supernovae
- Astronomy and Astrophysical Research
- Cosmology and Gravitation Theories
- Stellar, planetary, and galactic studies
- Astrophysics and Cosmic Phenomena
- Dark Matter and Cosmic Phenomena
- Adaptive optics and wavefront sensing
- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- CCD and CMOS Imaging Sensors
- Radio Astronomy Observations and Technology
- Astrophysics and Star Formation Studies
- History and Developments in Astronomy
- Geophysics and Gravity Measurements
- Gaussian Processes and Bayesian Inference
- Particle physics theoretical and experimental studies
- Astro and Planetary Science
- Black Holes and Theoretical Physics
- Remote Sensing in Agriculture
- Impact of Light on Environment and Health
- Scientific Research and Discoveries
- Neutrino Physics Research
- Solar and Space Plasma Dynamics
University of Chicago
2016-2025
Fermi National Accelerator Laboratory
2016-2025
Netherlands Institute for Radio Astronomy
2023-2024
Electronics for Imaging (United States)
1994-2024
Kavli Institute for Particle Astrophysics and Cosmology
2005-2023
Stanford University
1982-2023
University of Michigan–Ann Arbor
2023
Columbia University
2023
Institute of Space Sciences
2022
Campbell Collaboration
2005-2021
Aims. We present cosmological constraints from a joint analysis of type Ia supernova (SN Ia) observations obtained by the SDSS-II and SNLS collaborations. The dataset includes several low-redshift samples (z< 0.1), all three seasons (0.05 <z< 0.4), years (0.2 1), it totals 740 spectroscopically confirmed supernovae with high-quality light curves.
Ten years ago, the discovery that expansion of universe is accelerating put in place last major building block present cosmological model, which composed 4% baryons, 20% dark matter, and 76% energy. At same time, it posed one most profound mysteries all science, with deep connections to both astrophysics particle physics. Cosmic acceleration could arise from repulsive gravity energy—for example, quantum energy vacuum—or may signal general relativity (GR) breaks down on scales must be...
We show that a pseudo Nambu-Goldstone boson, with potential of the form V(\ensuremath{\varphi})=${\mathrm{\ensuremath{\Lambda}}}^{4}$[1\ifmmode\pm\else\textpm\fi{}cos(\ensuremath{\varphi}/f)], can naturally give rise to an epoch inflation in early Universe. Successful be achieved if f\ensuremath{\sim}${\mathit{m}}_{\mathrm{Pl}}$ and \ensuremath{\Lambda}\ensuremath{\sim}${\mathit{m}}_{\mathrm{GUT}}$. Such mass scales arise particle-physics models gauge group becomes strongly interacting at...
We present the design and performance of multi-object fiber spectrographs for Sloan Digital Sky Survey (SDSS) their upgrade Baryon Oscillation Spectroscopic (BOSS). Originally commissioned in Fall 1999 on 2.5-m aperture Telescope at Apache Point Observatory, produced more than 1.5 million spectra SDSS SDSS-II surveys, enabling a wide variety Galactic extra-galactic science including first observation baryon acoustic oscillations 2005. The were upgraded 2009 are currently use BOSS, flagship...
We present UV, optical, and NIR photometry of the first electromagnetic counterpart to a gravitational wave source from Advanced LIGO/Virgo, binary neutron star merger GW170817. Our data set extends discovery optical at $0.47$ days $18.5$ post-merger, includes observations with Dark Energy Camera (DECam), Gemini-South/FLAMINGOS-2 (GS/F2), {\it Hubble Space Telescope} ({\it HST}). The spectral energy distribution (SED) inferred this $0.6$ is well described by blackbody model $T\approx 8300$...
We explore the cosmological implications of an ultralight pseudo Nambu-Goldstone boson. With global spontaneous symmetry breaking scale $f\ensuremath{\simeq}{10}^{18}\mathrm{GeV}$ and explicit comparable to Mikheyev-Smirnov-Wolfenstein neutrino masses, $M\ensuremath{\sim}{10}^{\ensuremath{-}3}\mathrm{eV}$, such a field, which acquires mass ${m}_{\ensuremath{\varphi}}\ensuremath{\sim}{M}^{2}/f\ensuremath{\sim}{H}_{0}$, would currently dominate energy density Universe. The field acts as...
We present measurements of the Hubble diagram for 103 Type Ia supernovae (SNe) with redshifts 0.04 < z 0.42, discovered during first season (Fall 2005) Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. These data fill in redshift "desert" between low- and high-redshift SN surveys. combine SDSS-II new distance estimates published from ESSENCE survey, Legacy Survey, Space Telescope, a compilation nearby measurements. Combining Baryon Acoustic Oscillations SDSS Luminous Red Galaxy sample...
Abstract We describe the first public data release of Dark Energy Survey, DES DR1, consisting reduced single-epoch images, co-added source catalogs, and associated products services assembled over 3 yr science operations. DR1 is based on optical/near-infrared imaging from 345 distinct nights (2013 August to 2016 February) by Camera mounted 4 m Blanco telescope at Cerro Tololo Inter-American Observatory in Chile. wide-area survey covering ∼5000 deg 2 southern Galactic cap five broad...
We discuss the particle physics basis for models of natural inflation with pseudo Nambu-Goldstone bosons and study consequences large-scale structure nonscale-invariant density fluctuation spectra that arise in other models. A boson, a potential form $V(\ensuremath{\varphi})={\ensuremath{\Lambda}}^{4}[1\ifmmode\pm\else\textpm\fi{}cos(\frac{\ensuremath{\varphi}}{f})]$, can naturally give rise to an epoch early Universe, if $f\ensuremath{\sim}{M}_{\mathrm{Pl}}$...
The Dark Energy Camera is a new imager with 22 diameter field of view mounted at the prime focus Victor M. Blanco 4 m telescope on Cerro Tololo near La Serena, Chile. camera was designed and constructed by Survey Collaboration meets or exceeds stringent requirements for wide-field supernova surveys which collaboration uses it. consists five-element optical corrector, seven filters, shutter 60 cm aperture, charge-coupled device (CCD) focal plane 250 μm thick fully depleted CCDs cooled inside...
Abstract We present the Dark Energy Camera (DECam) discovery of optical counterpart first binary neutron star merger detected through gravitational-wave emission, GW170817. Our observations commenced 10.5 hr post-merger, as soon localization region became accessible from Chile. imaged 70 deg 2 in i and z bands, covering 93% initial integrated probability, to a depth necessary identify likely counterparts (e.g., kilonova). At 11.4 post-merger we bright transient located nucleus NGC 4993 at...
We report the discovery of eight new ultra-faint dwarf galaxy candidates in second year optical imaging data from Dark Energy Survey (DES). Six these are detected at high confidence, while two lower-confidence identified regions non-uniform survey coverage. The stellar systems found by three independent automated search techniques and as overdensities stars, consistent with isochrone luminosity function an old metal-poor simple population. faint (Mv > -4.7 mag) span a range physical sizes...
If weakly interacting massive particles (WIMP's) are the dark matter in galactic halo, they may be detected low-background ionization detectors now operating or with low-temperature devices under development. In detecting WIMP's of low mass spin-dependent nuclear interactions (e.g., photinos), a principal technical difficulty appears to achieving very thresholds (\ensuremath{\lesssim} keV) large (\ensuremath{\sim} kg) background noise. We present an analytic treatment WIMP detection and show...
The Sloan Digital Sky Survey-II (SDSS-II) has embarked on a multi-year project to identify and measure light curves for intermediate-redshift (0.05 < z 0.35) Type Ia supernovae (SNe Ia) using repeated five-band (ugriz) imaging over an area of 300 sq. deg. survey region is stripe 2.5° wide centered the celestial equator in Southern Galactic Cap that been imaged numerous times earlier years, enabling construction deep reference image discovery new objects. Supernova observations are being...
We report the discovery of eight new Milky Way companions in optical imaging data collected during first year Dark Energy Survey (DES). Each system is identified as a statistically significant over-density individual stars consistent with expected isochrone and luminosity function an old metal-poor stellar population. The objects span wide range absolute magnitudes (MV from to ), physical sizes (), heliocentric distances (). Based on low surface brightnesses, large sizes, and/or...
We report the discovery of rising X-ray emission from binary neutron star (BNS) merger event GW170817. This is first detection a gravitational-wave source. Observations acquired with Chandra Observatory (CXO) at t~2.3 days post reveal no significant emission, L_x<=3.2x10^38 erg/s (isotropic-equivalent). Continued monitoring revealed presence an source that brightened time, reaching L_x\sim 9x10^39 ~15.1 merger. interpret these findings in context isotropic and collimated relativistic...
We use the abundance and weak-lensing mass measurements of Sloan Digital Sky Survey maxBCG cluster catalog to simultaneously constrain cosmology richness–mass relation clusters. Assuming a flat ΛCDM cosmology, we find σ8(Ωm/0.25)0.41 = 0.832 ± 0.033 after marginalization over all systematics. In common with previous studies, our error budget is dominated by systematic uncertainties, primary two being absolute scale masses clusters, uncertainty in scatter relation. Our constraints are fully...
ABSTRACT We search for excess γ -ray emission coincident with the positions of confirmed and candidate Milky Way satellite galaxies using six years data from Fermi Large Area Telescope (LAT). Our sample 45 stellar systems includes 28 kinematically dark-matter-dominated dwarf spheroidal (dSphs) 17 recently discovered that have photometric characteristics consistent population known dSphs. For each these targets, relative predicted flux due to dark matter annihilation is taken kinematic...
We present Very Large Array (VLA) and Atacama Millimeter/sub-millimeter ALMA radio observations of GW\,170817, the first Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo gravitational wave (GW) event from a binary neutron star merger GW with an electromagnetic (EM) counterpart. Our data include following discovery optical transient at both centimeter ($13.7$ hours post merger) millimeter ($2.41$ days bands. detect faint emission 6 GHz 19.47 39.23 after merger, but not in...
We present a near-infrared spectral sequence of the electromagnetic counterpart to binary neutron star merger GW170817 detected by Advanced LIGO/Virgo. Our dataset comprises seven epochs J+H spectra taken with FLAMINGOS-2 on Gemini-South between 1.5 and 10.5 days after merger. In initial epoch, spectrum is dominated smooth blue continuum due high-velocity, lanthanide-poor kilonova component. Starting following night, all subsequent instead show features that are similar those predicted in...
The H0LiCOW collaboration inferred via strong gravitational lensing time delays a Hubble constant value of H 0 = 73.3 −1.8 +1.7 km s −1 Mpc , describing deflector mass density profiles by either power-law or stars (constant mass-to-light ratio) plus standard dark matter halos. mass-sheet transform (MST) that leaves the observables unchanged is considered dominant source residual uncertainty in . We quantify any potential effect MST with flexible family models, which directly encodes it, and...
ABSTRACT We describe updates to the redMaPPer algorithm, a photometric red-sequence cluster finder specifically designed for large surveys. The updated algorithm is applied of Science Verification (SV) data from Dark Energy Survey (DES), and Sloan Digital Sky (SDSS) DR8 set. DES SV catalog locally volume limited contains 786 clusters with richness (roughly equivalent ) . consists 26,311 , sharply increasing threshold as function redshift performance both catalogs shown be excellent,...
We combine Dark Energy Survey Year 1 clustering and weak lensing data with Baryon Acoustic Oscillations (BAO) Big Bang Nucleosynthesis (BBN) experiments to constrain the Hubble constant. Assuming a flat $\Lambda$CDM model minimal neutrino mass ($\sum m_\nu = 0.06$ eV) we find $H_0=67.2^{+1.2}_{-1.0}$ km/s/Mpc (68% CL). This result is completely independent of constant measurements based on distance ladder, Cosmic Microwave Background (CMB) anisotropies (both temperature polarization), strong...