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S. P. Willner

Bio: S. P. Willner is an academic researcher from Harvard University. The author has contributed to research in topics: Galaxy & Luminous infrared galaxy. The author has an hindex of 50, co-authored 138 publications receiving 10446 citations.


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Journal ArticleDOI
TL;DR: The Infrared Array Camera (IRAC) is one of three focal plane instruments on the Spitzer Space Telescope as mentioned in this paper, which is a four-channel camera that obtains simultaneous broadband images at 3.6, 4.5, 5.8, and 8.0 m.
Abstract: The Infrared Array Camera (IRAC) is one of three focal plane instruments on the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broadband images at 3.6, 4.5, 5.8, and 8.0 � m. Two nearly adjacent 5A2 ; 5A2 fields of view in the focal plane are viewed by the four channels in pairs (3.6 and 5.8 � m; 4.5 and 8 � m). All four detector arrays in the camera are 256 ; 256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors. IRAC is a powerful survey instrument because of its high sensitivity, large field of view, and four-color imaging. This paper summarizes the in-flight scientific, technical, and operational performance of IRAC.

3,567 citations

Journal ArticleDOI
Saurabh Jha1, Saurabh Jha2, Robert P. Kirshner2, Peter Challis2, Peter M. Garnavich2, Thomas Matheson2, Alicia M. Soderberg2, Genevieve J. Graves2, Malcolm Hicken2, João Alves2, Héctor G. Arce2, Zoltan Balog2, Pauline Barmby2, Elizabeth J. Barton2, Perry Berlind2, Ann Bragg2, Cesar Briceno2, Warren R. Brown2, J. H. Buckley2, Nelson Caldwell2, Michael L. Calkins2, B. J. Carter2, Kristi Dendy Concannon2, R. Hank Donnelly2, Kristoffer A. Eriksen2, Daniel G. Fabricant2, Emilio E. Falco2, Fabrizio Fiore2, Michael R. Garcia2, Mercedes Gomez2, Norman A. Grogin2, Ted Groner2, Paul J. Groot2, Karl E. Haisch2, Lee Hartmann2, Carl Hergenrother2, Matthew J. Holman2, John P. Huchra2, Ray Jayawardhana2, D. Jerius2, Sheila J. Kannappan2, Dong-Woo Kim2, Jan T. Kleyna2, Christopher S. Kochanek2, Daniel M. Koranyi2, M. Krockenberger2, Charles J. Lada2, Kevin Luhman2, Jane Luu2, Lucas M. Macri2, J. Mader2, Andisheh Mahdavi2, Massimo Marengo2, Brian G. Marsden2, Brian McLeod2, Brian R. McNamara2, S. Thomas Megeath2, Dan Moraru2, A. Mossman2, August Muench2, J. A. Muñoz2, James Muzerolle2, Orlando Naranjo2, Kristin Nelson-Patel2, Michael A. Pahre2, Brian M. Patten2, J. Peters2, Wayne Peters2, John C. Raymond2, Kenneth J. Rines2, Rudolph E. Schild2, Gregory J. Sobczak2, Timothy Spahr2, John R. Stauffer2, Robert P. Stefanik2, Andrew Szentgyorgyi2, Eric V. Tollestrup2, Petri Vaisanen2, Alexey Vikhlinin2, Zhong Wang2, S. P. Willner2, Scott J. Wolk2, Joseph Zajac2, Ping Zhao2, Krzysztof Z. Stanek2 
TL;DR: In this article, the authors present UBVRI photometry of 44 Type Ia supernovae (SNe Ia) observed from 1997 to 2001 as part of a continuing monitoring campaign at the Fred Lawrence Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics.
Abstract: We present UBVRI photometry of 44 Type Ia supernovae (SNe Ia) observed from 1997 to 2001 as part of a continuing monitoring campaign at the Fred Lawrence Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics. The data set comprises 2190 observations and is the largest homogeneously observed and reduced sample of SNe Ia to date, nearly doubling the number of well-observed, nearby SNe Ia with published multicolor CCD light curves. The large sample of U-band photometry is a unique addition, with important connections to SNe Ia observed at high redshift. The decline rate of SN Ia U-band light curves correlates well with the decline rate in other bands, as does the U - B color at maximum light. However, the U-band peak magnitudes show an increased dispersion relative to other bands even after accounting for extinction and decline rate, amounting to an additional ~40% intrinsic scatter compared to the B band.

349 citations

Journal ArticleDOI
TL;DR: In this paper, a simple method for selecting high-z population based solely on the ratio of the observed mid-IR 24um to optical R-band flux density was presented, revealing a significant population of high-redshift z~2 dust-obscured galaxies (DOGs) with large midIR to UV luminosity ratios.
Abstract: Observations with Spitzer Space Telescope have recently revealed a significant population of high-redshift z~2 dust-obscured galaxies (DOGs) with large mid-IR to UV luminosity ratios. These galaxies have been missed in traditional optical studies of the distant universe. We present a simple method for selecting this high-z population based solely on the ratio of the observed mid-IR 24um to optical R-band flux density. In the 8.6 sq.deg Bootes NDWFS Field, we uncover ~2,600 DOG candidates (= 0.089/sq.arcmin) with 24um flux densities F24>0.3mJy and (R-[24])>14 (i.e., F[24]/F[R] > 1000). These galaxies have no counterparts in the local universe, and become a larger fraction of the population at fainter F24, representing 13% of the sources at 0.3~mJy. DOGs exhibit evidence of both star-formation and AGN activity, with the brighter 24um sources being more AGN- dominated. We have measured spectroscopic redshifts for 86 DOGs, and find a broad z distribution centered at ~2.0. Their space density is 2.82E-5 per cubic Mpc, similar to that of bright sub-mm-selected galaxies at z~2. These redshifts imply very large luminosities LIR>~1E12-14 Lsun. DOGs contribute ~45-100% of the IR luminosity density contributed by all z~2 ULIRGs, suggesting that our simple selection criterion identifies the bulk of z~2 ULIRGs. DOGs may be the progenitors of ~4L* present-day galaxies seen undergoing a luminous,short- lived phase of bulge and black hole growth. They may represent a brief evolution phase between SMGs and less obscured quasars or galaxies. [Abridged]

304 citations

Journal ArticleDOI
TL;DR: In this paper, galaxy counts at 3.6 and 4.5μm were shown to follow the expectations of a Euclidean world model down to ~16.5 mag.
Abstract: Infrared source counts at wavelengths 3 μm < λ < 10 μm cover more than 10 mag in source brightness, reach 4 orders of magnitude in surface density, and reach an integrated surface density of 105 sources deg-2. At m < 14 mag, most of the sources are Galactic stars, in agreement with models. After removal of Galactic stars, galaxy counts are consistent with what few measurements exist at nearby wavelengths. At 3.6 and 4.5 μm, the galaxy counts follow the expectations of a Euclidean world model down to ~16 mag and drop below the Euclidean curve for fainter magnitudes. Counts at these wavelengths begin to show decreasing completeness around 19.5 mag. At 5.8 and 8 μm, the counts relative to a Euclidean world model show a large excess at bright magnitudes. This is probably because local galaxies emit strongly in the aromatic dust (polycyclic aromatic hydrocarbon) features. The counts at 3.6 μm resolve less than 50% of the cosmic infrared background at that wavelength.

279 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the Wilkinson Microwave Anisotropy Probe (WMAP) 5-year data were used to constrain the physics of cosmic inflation via Gaussianity, adiabaticity, the power spectrum of primordial fluctuations, gravitational waves, and spatial curvature.
Abstract: The Wilkinson Microwave Anisotropy Probe (WMAP) 5-year data provide stringent limits on deviations from the minimal, six-parameter Λ cold dark matter model. We report these limits and use them to constrain the physics of cosmic inflation via Gaussianity, adiabaticity, the power spectrum of primordial fluctuations, gravitational waves, and spatial curvature. We also constrain models of dark energy via its equation of state, parity-violating interaction, and neutrino properties, such as mass and the number of species. We detect no convincing deviations from the minimal model. The six parameters and the corresponding 68% uncertainties, derived from the WMAP data combined with the distance measurements from the Type Ia supernovae (SN) and the Baryon Acoustic Oscillations (BAO) in the distribution of galaxies, are: Ω b h 2 = 0.02267+0.00058 –0.00059, Ω c h 2 = 0.1131 ± 0.0034, ΩΛ = 0.726 ± 0.015, ns = 0.960 ± 0.013, τ = 0.084 ± 0.016, and at k = 0.002 Mpc-1. From these, we derive σ8 = 0.812 ± 0.026, H 0 = 70.5 ± 1.3 km s-1 Mpc–1, Ω b = 0.0456 ± 0.0015, Ω c = 0.228 ± 0.013, Ω m h 2 = 0.1358+0.0037 –0.0036, z reion = 10.9 ± 1.4, and t 0 = 13.72 ± 0.12 Gyr. With the WMAP data combined with BAO and SN, we find the limit on the tensor-to-scalar ratio of r 1 is disfavored even when gravitational waves are included, which constrains the models of inflation that can produce significant gravitational waves, such as chaotic or power-law inflation models, or a blue spectrum, such as hybrid inflation models. We obtain tight, simultaneous limits on the (constant) equation of state of dark energy and the spatial curvature of the universe: –0.14 < 1 + w < 0.12(95%CL) and –0.0179 < Ω k < 0.0081(95%CL). We provide a set of WMAP distance priors, to test a variety of dark energy models with spatial curvature. We test a time-dependent w with a present value constrained as –0.33 < 1 + w 0 < 0.21 (95% CL). Temperature and dark matter fluctuations are found to obey the adiabatic relation to within 8.9% and 2.1% for the axion-type and curvaton-type dark matter, respectively. The power spectra of TB and EB correlations constrain a parity-violating interaction, which rotates the polarization angle and converts E to B. The polarization angle could not be rotated more than –59 < Δα < 24 (95% CL) between the decoupling and the present epoch. We find the limit on the total mass of massive neutrinos of ∑m ν < 0.67 eV(95%CL), which is free from the uncertainty in the normalization of the large-scale structure data. The number of relativistic degrees of freedom (dof), expressed in units of the effective number of neutrino species, is constrained as N eff = 4.4 ± 1.5 (68%), consistent with the standard value of 3.04. Finally, quantitative limits on physically-motivated primordial non-Gaussianity parameters are –9 < f local NL < 111 (95% CL) and –151 < f equil NL < 253 (95% CL) for the local and equilateral models, respectively.

5,904 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present cosmological parameter constraints based on the final nine-year WMAP data, in conjunction with a number of additional cosmology data sets.
Abstract: We present cosmological parameter constraints based on the final nine-year WMAP data, in conjunction with a number of additional cosmological data sets. The WMAP data alone, and in combination, continue to be remarkably well fit by a six-parameter CDM model. When WMAP data are combined with measurements of the high-l cosmic microwave background (CMB) anisotropy, the baryon acoustic oscillation (BAO) scale, and the Hubble constant, the matter and energy densities, bh 2 , ch 2 , and , are each determined to a precision of 1.5%. The amplitude of the primordial spectrum is measured to within 3%, and there is now evidence for a tilt in the primordial spectrum at the 5 level, confirming the first detection of tilt based on the five-year WMAP data. At the end of the WMAP mission, the nine-year data decrease the allowable volume of the six-dimensional CDM parameter space by a factor of 68,000 relative to pre-WMAP measurements. We investigate a number of data combinations and show that their CDM parameter fits are consistent. New limits on deviations from the six-parameter model are presented, for example: the fractional contribution of tensor modes is limited to r < 0.13 (95% CL); the spatial curvature parameter is limited to k = 0.0027 +0.0039 0.0038 ; the summed mass of neutrinos is limited to P m < 0.44 eV (95% CL); and the number of relativistic species is found to lie within Ne = 3.84±0.40, when the full data are analyzed. The joint constraint on Ne and the primordial helium abundance, YHe, agrees with the prediction of standard Big Bang nucleosynthesis. We compare recent Planck measurements of the Sunyaev‐Zel’dovich eect with our seven-year measurements, and show their mutual agreement. Our analysis of the polarization pattern around temperature extrema is updated. This confirms a fundamental prediction of the standard cosmological model and provides a striking illustration of acoustic oscillations and adiabatic initial conditions in the early universe. Subject headings: cosmic microwave background, cosmology: observations, early universe, dark matter, space vehicles, space vehicles: instruments, instrumentation: detectors, telescopes

5,488 citations

Journal ArticleDOI
TL;DR: The Infrared Array Camera (IRAC) is one of three focal plane instruments on the Spitzer Space Telescope as mentioned in this paper, which is a four-channel camera that obtains simultaneous broadband images at 3.6, 4.5, 5.8, and 8.0 m.
Abstract: The Infrared Array Camera (IRAC) is one of three focal plane instruments on the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broadband images at 3.6, 4.5, 5.8, and 8.0 � m. Two nearly adjacent 5A2 ; 5A2 fields of view in the focal plane are viewed by the four channels in pairs (3.6 and 5.8 � m; 4.5 and 8 � m). All four detector arrays in the camera are 256 ; 256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors. IRAC is a powerful survey instrument because of its high sensitivity, large field of view, and four-color imaging. This paper summarizes the in-flight scientific, technical, and operational performance of IRAC.

3,567 citations

Journal ArticleDOI
TL;DR: The Spitzer Space Telescope, NASA's great Observatory for infrared astronomy, was launched 2003 August 25 and is returning excellent scientific data from its Earth-trailing solar orbit as mentioned in this paper.
Abstract: The Spitzer Space Telescope, NASA's Great Observatory for infrared astronomy, was launched 2003 August 25 and is returning excellent scientific data from its Earth-trailing solar orbit. Spitzer combines the intrinsic sensitivity achievable with a cryogenic telescope in space with the great imaging and spectroscopic power of modern detector arrays to provide the user community with huge gains in capability for exploration of the cosmos in the infrared. The observatory systems are largely performing as expected, and the projected cryogenic lifetime is in excess of 5 years. This paper summarizes the on-orbit scientific, technical, and operational performance of Spitzer. Subsequent papers in this special issue describe the Spitzer instruments in detail and highlight many of the exciting scientific results obtained during the first 6 months of the Spitzer mission.

3,177 citations

Journal ArticleDOI
TL;DR: In this article, the authors review the range of complementary techniques and theoretical tools that allow astronomers to map the cosmic history of star formation, heavy element production, and reionization of the Universe from the cosmic "dark ages" to the present epoch.
Abstract: Over the past two decades, an avalanche of data from multiwavelength imaging and spectroscopic surveys has revolutionized our view of galaxy formation and evolution. Here we review the range of complementary techniques and theoretical tools that allow astronomers to map the cosmic history of star formation, heavy element production, and reionization of the Universe from the cosmic "dark ages" to the present epoch. A consistent picture is emerging, whereby the star-formation rate density peaked approximately 3.5 Gyr after the Big Bang, at z~1.9, and declined exponentially at later times, with an e-folding timescale of 3.9 Gyr. Half of the stellar mass observed today was formed before a redshift z = 1.3. About 25% formed before the peak of the cosmic star-formation rate density, and another 25% formed after z = 0.7. Less than ~1% of today's stars formed during the epoch of reionization. Under the assumption of a universal initial mass function, the global stellar mass density inferred at any epoch matches reasonably well the time integral of all the preceding star-formation activity. The comoving rates of star formation and central black hole accretion follow a similar rise and fall, offering evidence for co-evolution of black holes and their host galaxies. The rise of the mean metallicity of the Universe to about 0.001 solar by z = 6, one Gyr after the Big Bang, appears to have been accompanied by the production of fewer than ten hydrogen Lyman-continuum photons per baryon, a rather tight budget for cosmological reionization.

3,104 citations