Publications (18)81.74 Total impact
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ABSTRACT: We use microwave temperature maps from two seasons of data from the Atacama Cosmology Telescope (ACTPol) at 146 GHz, together with the Constant Mass CMASS galaxy sample from the Baryon Oscillation Spectroscopic Survey to measure the kinematic SunyaevZe\v{l}dovich (kSZ) effect over the redshift range z = 0.4  0.7. We use galaxy positions and the continuity equation to obtain a reconstruction of the lineofsight velocity field. We stack the cosmic microwave background temperature at the location of each halo, weighted by the corresponding reconstructed velocity. The resulting best fit kSZ model is preferred over the nokSZ hypothesis at 3.3sigma and 2.9sigma for two independent velocity reconstruction methods, using 25,537 galaxies over 660 square degrees. The effect of foregrounds that are uncorrelated with the galaxy velocities is expected to be well below our signal, and residual thermal SunyaevZe\v{l}dovich contamination is controlled by masking the most massive clusters. Finally, we discuss the systematics involved in converting our measurement of the kSZ amplitude into the mean free electron fraction of the halos in our sample.  [Show abstract] [Hide abstract]
ABSTRACT: Using a radioquiet subsample of the Sloan Digital Sky Survey spectroscopic quasar catalog, spanning redshifts 0.53.5, we derive the mean millimetre and farinfrared quasar spectral energy densities via a stacking analysis of Atacama Cosmology Telescope and HerschelSPIRE data. We constrain the form and evolution of the farinfrared emission finding 34$\sigma$ evidence for the presence of the thermal SunyaevZel'dovich (SZ) effect in the millimetre bands. We find this signal to be characteristic of a hot ionized gas component with thermal energy $(6.2 \pm 1.7) \times 10^{60}$erg. This amount of thermal energy is an order of magnitude greater than would be expected assuming only hot gas in virial equilibrium with the dark matter haloes of $(15)\times 10^{12}h^{1}$M$_\odot$ that these systems are expected to occupy, though the highest quasar mass estimates found in the literature could explain a large fraction of this energy. We find that our measurements are consistent with a scenario in which quasars deposit up to $(14.5 \pm 3.3)~\tau_8^{1}$ per cent of their radiative energy into their circumgalactic environment if their typical period of quasar activity is $\tau_8\times 10^8$ years. If quasar host masses are high ($\sim10^{13}h^{1}$M$_\odot$), then this percentage will be reduced significantly. Furthermore, the uncertainty quoted for this percentage is only statistical and additional systematic uncertainties (e.g., on quasar bolometric luminosity) enter at the 40 per cent level. Finally, emission from thermal dust is significant in these systems, with infrared luminosities of $\log_{10}(L_{\rm ir}/{\rm L}_\odot)=11.412.2$, increasing to higher redshift. We consider various models for dust emission. While sufficiently complex dust models can obviate the SZ effect, the SZ interpretation remains favoured at the 34$\sigma$ level for most models.  [Show abstract] [Hide abstract]
ABSTRACT: We present a measurement of the gravitational lensing of the Cosmic Microwave Background (CMB) temperature and polarization fields obtained by crosscorrelating the reconstructed convergence signal from the first season of ACTPol data at 146 GHz with Cosmic Infrared Background (CIB) fluctuations measured using the Planck satellite. Using an overlap area of 206 square degrees, we detect gravitational lensing of the CMB polarization by largescale structure at a statistical significance of 4.5 sigma. Combining both CMB temperature and polarization data gives a lensing detection at 9.1 sigma significance. A Bmode polarization lensing signal is present with a significance of 3.2 sigma. We also present the first measurement of CMB lensingCIB correlation at small scales corresponding to l > 2000. Null tests and systematic checks show that our results are not significantly biased by astrophysical or instrumental systematic effects, including Galactic dust. Fitting our measurements to the bestfit lensingCIB cross power spectrum measured in Planck data, scaled by an amplitude A, gives A=1.02 +0.12/0.18 (stat.) +/0.06(syst.), consistent with the Planck results.The Astrophysical Journal 07/2015; 808(1). DOI:10.1088/0004637X/808/1/7 · 5.99 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The cosmic microwave background (CMB) energy spectrum is a nearperfect blackbody. The standard model of cosmology predicts small spectral distortions to this form, but no such distortion of the skyaveraged CMB spectrum has yet been measured. We calculate the largest expected distortion, which arises from the inverse Compton scattering of CMB photons off hot, ionized electrons in the universe, known as the thermal SunyaevZel'dovich (tSZ) effect. We show that the predicted signal is roughly one order of magnitude below the current bound from the COBEFIRAS experiment, but will be detected at enormous significance ($\gtrsim 1000\sigma$) by the proposed Primordial Inflation Explorer (PIXIE). Although cosmic variance reduces the effective signaltonoise to $230\sigma$, PIXIE will still yield a subpercent constraint on the total thermal energy in electrons in the observable universe. Furthermore, we show that PIXIE will detect subtle relativistic effects in the skyaveraged tSZ signal at $30\sigma$, which directly probe moments of the optical depthweighted intracluster medium electron temperature distribution. PIXIE will thus determine the global thermodynamic properties of ionized gas in the universe with unprecedented precision. These measurements will impose a fundamental "integral constraint" on models of galaxy formation and the injection of feedback energy over cosmic time.  [Show abstract] [Hide abstract]
ABSTRACT: This paper was published online on 13 April 2015 with an error in an author’s name. The seventh author’s name should read as “Jerod Caligiuri.” The author’s name has been corrected as of 17 April 2015. The author’s name is correct in the printed version of the journal.Physical Review Letters 05/2015; 114(18). DOI:10.1103/PhysRevLett.114.189901 · 7.51 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present a statistical detection of the gravitational lensing of the cosmic microwave background by $10^{13}$ solar mass dark matter halos. Lensing convergence maps from the Atacama Cosmology Telescope Polarimeter (ACTPol) are stacked at the positions of around 12,000 opticallyselected CMASS galaxies from the SDSSIII/BOSS survey. The mean lensing signal is consistent with simulated dark matter halo profiles, and is favored over a null signal at 3.2 sigma significance. This result demonstrates the potential of microwave background lensing to probe the dark matter distribution in galaxy group and galaxy cluster halos.Physical Review Letters 04/2015; 114(15):151302. DOI:10.1103/PhysRevLett.114.151302 · 7.51 Impact Factor 
Article: The Atacama Cosmology Telescope: A Measurement of the Thermal SunyaevZel'dovich OnePoint PDF
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ABSTRACT: We present a measurement of the onepoint probability distribution function (PDF) of the thermal SunyaevZel'dovich (tSZ) decrement in the pixel temperature histogram of filtered 148 GHz sky maps from the Atacama Cosmology Telescope (ACT). The PDF includes the signal from all galaxy clusters in the map, including objects below the signaltonoise threshold for individual detection, making it a particularly sensitive probe of the amplitude of matter density perturbations, $\sigma_8$. We use a combination of analytic halo model calculations and numerical simulations to compute the theoretical tSZ PDF and its covariance matrix, accounting for all noise sources and including relativistic corrections. From the measured ACT 148 GHz PDF alone, we find $\sigma_8 = 0.793 \pm 0.018$, with additional systematic errors of $\pm 0.017$ due to uncertainty in intracluster medium gas physics and $\pm 0.006$ due to uncertainty in infrared point source contamination. Using effectively the same data set, the statistical error here is a factor of two lower than that found in ACT's previous $\sigma_8$ determination based solely on the skewness of the tSZ signal. In future temperature maps with higher sensitivity, the tSZ PDF will break the degeneracy between intracluster medium gas physics and cosmological parameters.  [Show abstract] [Hide abstract]
ABSTRACT: We use the Planck nominal mission temperature maps to examine the stacked thermal SunyaevZel'dovich (tSZ) signal of 188042 "locally brightest galaxies" (LBGs) selected from the Sloan Digital Sky Survey Data Release 7. Our LBG sample closely matches that of Planck Collaboration XI (2013, PCXI), but our analysis differs in several ways. We work directly in terms of physically observable quantities, requiring minimal assumptions about the gas pressure profile. We explicitly model the dust emission from each LBG and simultaneously measure both the stacked tSZ and dust signals as a function of stellar mass $M_*$. There is a small residual bias in stacked tSZ measurements; we measure this bias and subtract it from our results, finding that the effects are nonnegligible at the lowest masses in the LBG sample. Finally, we compare our measurements with two pressure profile models, finding that the profile from Battaglia et al. (2012b) provides a better fit to the results than the Arnaud et al. (2010) "universal pressure profile". However, within the uncertainties, we find that the data are consistent with a selfsimilar scaling with mass  more precise measurements are needed to detect the relatively small deviations from selfsimilarity predicted by these models. Our results are consistent with PCXI for LBGs with $\log(M_*/M_\odot) > 11.3$; below this mass, however, we do not see evidence for a stacked tSZ signal, in contrast to PCXI. The difference likely arises from our consideration of dust and stacking bias effects. In particular, we note that the stacked dust emission is comparable to or larger than the stacked tSZ signal for $\log(M_*/M_\odot) \lesssim 11.3$. Future tSZ analyses with larger samples and lower noise levels should be able to probe deviations from selfsimilarity and thus provide constraints on models of feedback and the evolution of hot halo gas over cosmic time.The Astrophysical Journal 09/2014; 808(2). DOI:10.1088/0004637X/808/2/151 · 5.99 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Future arcminute resolution polarization data from groundbased Cosmic Microwave Background (CMB) observations can be used to estimate the contribution to the temperature power spectrum from the primary anisotropies and to uncover the signature of reionization near $\ell=1500$ in the small angularscale temperature measurements. Our projections are based on combining expected smallscale Emode polarization measurements from Advanced ACTPol in the range $300<\ell<3000$ with simulated temperature data from the full Planck mission in the low and intermediate $\ell$ region, $2<\ell<2000$. We show that the six basic cosmological parameters determined from this combination of data will predict the underlying primordial temperature spectrum at high multipoles to better than $1\%$ accuracy. Assuming an efficient cleaning from multifrequency channels of most foregrounds in the temperature data, we investigate the sensitivity to the only residual secondary component, the kinematic SunyaevZel'dovich (kSZ) term. The CMB polarization is used to break degeneracies between primordial and secondary terms present in temperature and, in effect, to remove from the temperature data all but the residual kSZ term. We estimate a $15 \sigma$ detection of the diffuse homogeneous kSZ signal from expected AdvACT temperature data at $\ell>1500$, leading to a measurement of the amplitude of matter density fluctuations, $\sigma_8$, at $1\%$ precision. Alternatively, by exploring the reionization signal encoded in the patchy kSZ measurements, we bound the time and duration of the reionization with $\sigma(z_{\rm re})=1.1$ and $\sigma(\Delta z_{\rm re})=0.2$. We find that these constraints degrade rapidly with large beam sizes, which highlights the importance of arcminutescale resolution for future CMB surveys.Journal of Cosmology and Astroparticle Physics 06/2014; JCAP08(2014)010. DOI:10.1088/14757516/2014/08/010 · 6.04 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: BICEP2 has reported the detection of a degreescale Bmode polarization pattern in the Cosmic Microwave Background (CMB) and has interpreted the measurement as evidence for primordial gravitational waves. Motivated by the profound importance of the discovery of gravitational waves from the early Universe, we examine to what extent a combination of Galactic foregrounds and lensed Emodes could be responsible for the signal. We reanalyze the BICEP2 results and show that the 100x150 GHz and 150x150 GHz data are consistent with a cosmology with r=0.2 and negligible foregrounds, but also with a cosmology with r=0 and a significant dust polarization signal. We give independent estimates of the dust polarization signal in the BICEP2 region using four different approaches. While these approaches are consistent with each other, the expected amplitude of the dust polarization power spectrum remains uncertain by about a factor of three. The lower end of the prediction leaves room for a primordial contribution, but at the higher end the dust in combination with the standard CMB lensing signal could account for the BICEP2 observations, without requiring the existence of primordial gravitational waves. By measuring the crosscorrelations between the prePlanck templates used in the BICEP2 analysis and between different versions of a databased template, we emphasize that crosscorrelations between models are very sensitive to noise in the polarization angles and that measured crosscorrelations are likely underestimates of the contribution of foregrounds to the map. These results suggest that BICEP1 and BICEP2 data alone cannot distinguish between foregrounds and a primordial gravitational wave signal, and that future Keck Array observations at 100 GHz and Planck observations at higher frequencies will be crucial to determine whether the signal is of primordial origin. (abridged)Journal of Cosmology and Astroparticle Physics 05/2014; 2014(08). DOI:10.1088/14757516/2014/08/039 · 5.81 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We report on measurements of the cosmic microwave background (CMB) and celestial polarization at 146 GHz made with the Atacama Cosmology Telescope Polarimeter (ACTPol) in its first three months of observing. Four regions of sky covering a total of 270 square degrees were mapped with an angular resolution of $1.3'$. The map noise levels in the four regions are between 11 and 17 $\mu$Karcmin. We present TT, TE, EE, TB, EB, and BB power spectra from three of these regions. The observed Emode polarization power spectrum, displaying six acoustic peaks in the range $200<\ell<3000$, is an excellent fit to the prediction of the bestfit cosmological models from WMAP9+ACT and Planck data. The polarization power spectrum, which mainly reflects primordial plasma velocity perturbations, provides an independent determination of cosmological parameters consistent with those based on the temperature power spectrum, which results mostly from primordial density perturbations. We find that without masking any point sources in the EE data at $\ell<9000$, the Poisson tail of the EE power spectrum due to polarized point sources has an amplitude less than $2.4$ $\mu$K$^2$ at $\ell = 3000$ at 95\% confidence. Finally, we report that the Crab Nebula, an important polarization calibration source at microwave frequencies, has 8.7\% polarization with an angle of $150.9^\circ \pm 0.5^\circ$ when smoothed with a $5'$ Gaussian beam.Journal of Cosmology and Astroparticle Physics 05/2014; JCAP10(2014)007. DOI:10.1088/14757516/2014/10/007 · 5.81 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The nominal mission maps from the Planck satellite contain a wealth of information about secondary anisotropies in the cosmic microwave background (CMB), including those induced by the thermal SunyaevZel'dovich (tSZ) effect and gravitational lensing. As both the tSZ and CMB lensing signals trace the largescale matter density field, the anisotropies sourced by these processes are expected to be correlated. We report the first detection of this crosscorrelation signal, which we measure at 6.2 sigma significance using the Planck data. We take advantage of Planck's multifrequency coverage to construct a tSZ map using internal linear combination techniques, which we subsequently crosscorrelate with the publiclyreleased Planck CMB lensing potential map. [Abridged] We interpret the signal using halo model calculations, which indicate that the tSZ  CMB lensing crosscorrelation is a unique probe of the physics of intracluster gas in highredshift, lowmass groups and clusters. Our results are consistent with extrapolations of existing gas physics models to this previously unexplored regime and show clear evidence for contributions from both the one and twohalo terms, but no statistically significant evidence for contributions from diffuse, unbound gas outside of collapsed halos. We also show that the amplitude of the signal depends rather sensitively on the amplitude of fluctuations ($\sigma_8$) and the matter density ($\Omega_m$). We constrain the degenerate combination $\sigma_8 (\Omega_m/0.282)^{0.26} = 0.831^{+0.026}_{0.030}$, a result that is in less tension with primordial CMB constraints than some recent tSZ analyses. Our detection is a direct confirmation that hot, ionized gas traces the dark matter distribution over a wide range of scales in the universe ($\sim 0.1$$50 \, {\rm Mpc}/h$).Journal of Cosmology and Astroparticle Physics 12/2013; 2014(02). DOI:10.1088/14757516/2014/02/030 · 5.81 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We carry out a comprehensive analysis of the possible constraints on cosmological and astrophysical parameters achievable with measurements of the thermal SunyaevZel'dovich (tSZ) power spectrum from upcoming fullsky CMB observations, with a particular focus on oneparameter extensions to the LCDM standard model involving local primordial nonGaussianity (described by fNL) and massive neutrinos (described by Mnu). We include all of the relevant physical effects due to these additional parameters, including the change to the halo mass function and the scaledependent halo bias induced by local primordial nonGaussianity. [...] We compute forecasts for Planck, PIXIE, and a cosmic variance (CV)limited experiment, using multifrequency subtraction to remove foregrounds and implementing two masking criteria based on the ROSAT and eROSITA cluster catalogs to reduce the significant CV errors at low multipoles. We find that Planck can detect the tSZ power spectrum with >30sigma significance, regardless of the masking scenario. However, neither Planck or PIXIE is likely to provide competitive constraints on fNL from the tSZ power spectrum due to CV noise at lowell overwhelming the unique signature of the scaledependent bias. A future CVlimited experiment could provide a 3sigma detection of fNL~37, which is the WMAP9 maximumlikelihood result. The outlook for neutrino masses is more optimistic: Planck can reach levels comparable to the current upper bounds ~<0.3 eV with conservative assumptions about the intracluster medium (ICM); stronger ICM priors could allow Planck to provide 12sigma evidence for massive neutrinos from the tSZ power spectrum, depending on the true value of the sum of the neutrino masses. We also forecast a ~<10% constraint on the outer slope of the ICM pressure profile using the unmasked Planck tSZ power spectrum.Physical review D: Particles and fields 03/2013; 88(6). DOI:10.1103/PhysRevD.88.063526 · 4.86 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present constraints on cosmological and astrophysical parameters from highresolution microwave background maps at 148 GHz and 218 GHz made by the Atacama Cosmology Telescope (ACT) in three seasons of observations from 2008 to 2010. A model of primary cosmological and secondary foreground parameters is fit to the map power spectra and lensing deflection power spectrum, including contributions from both the thermal SunyaevZeldovich (tSZ) effect and the kinematic SunyaevZeldovich (kSZ) effect, Poisson and correlated anisotropy from unresolved infrared sources, radio sources, and the correlation between the tSZ effect and infrared sources. The power ell^2 C_ell/2pi of the thermal SZ power spectrum at 148 GHz is measured to be 3.4 +\ 1.4 muK^2 at ell=3000, while the corresponding amplitude of the kinematic SZ power spectrum has a 95% confidence level upper limit of 8.6 muK^2. Combining ACT power spectra with the WMAP 7year temperature and polarization power spectra, we find excellent consistency with the LCDM model. We constrain the number of effective relativistic degrees of freedom in the early universe to be Neff=2.79 +\ 0.56, in agreement with the canonical value of Neff=3.046 for three massless neutrinos. We constrain the sum of the neutrino masses to be Sigma m_nu < 0.39 eV at 95% confidence when combining ACT and WMAP 7year data with BAO and Hubble constant measurements. We constrain the amount of primordial helium to be Yp = 0.225 +\ 0.034, and measure no variation in the fine structure constant alpha since recombination, with alpha/alpha0 = 1.004 +/ 0.005. We also find no evidence for any running of the scalar spectral index, dns/dlnk = 0.004 +\ 0.012.Journal of Cosmology and Astroparticle Physics 01/2013; 2013(10):60. DOI:10.1088/14757516/2013/10/060 · 5.81 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We measure the crosscorrelation of Atacama Cosmology Telescope CMB lensing convergence maps with quasar maps made from the Sloan Digital Sky Survey DR8 SDSSXDQSO photometric catalog. The CMB lensingquasar crosspower spectrum is detected for the first time at a significance of 3.8 sigma, which directly confirms that the quasar distribution traces the mass distribution at high redshifts z>1. Our detection passes a number of null tests and systematic checks. Using this crosspower spectrum, we measure the amplitude of the linear quasar bias assuming a template for its redshift dependence, and find the amplitude to be consistent with an earlier measurement from clustering; at redshift z ~ 1.4, the peak of the distribution of quasars in our maps, our measurement corresponds to a bias of b = 2.5 +/ 0.6. With the signaltonoise ratio on CMB lensing measurements likely to improve by an order of magnitude over the next few years, our results demonstrate the potential of CMB lensing crosscorrelations to probe astrophysics at high redshifts.Physical Review D 07/2012; 86(8). DOI:10.1103/PhysRevD.86.083006 · 4.86 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: In this paper, we explain how moments of the thermal SunyaevZel'dovich (tSZ) effect can constrain both cosmological parameters and the astrophysics of the intracluster medium (ICM). As the tSZ signal is strongly nonGaussian, higher moments of tSZ maps contain useful information. We first calculate the dependence of the tSZ moments on cosmological parameters, finding that higher moments scale more steeply with sigma_8 and are sourced by more massive galaxy clusters. Taking advantage of the different dependence of the variance and skewness on cosmological and astrophysical parameters, we construct a statistic, <T^3>/<T^2>^1.4, which cancels much of the dependence on cosmology (i.e., sigma_8) yet remains sensitive to the astrophysics of intracluster gas (in particular, to the gas fraction in lowmass clusters). Constraining the ICM astrophysics using this statistic could break the wellknown degeneracy between cosmology and gas physics in tSZ measurements, allowing for tight constraints on cosmological parameters. Although detailed simulations will be needed to fully characterize the accuracy of this technique, we provide a first application to data from the Atacama Cosmology Telescope and the South Pole Telescope. We estimate that a Plancklike fullsky tSZ map could achieve a <1% constraint on sigma_8 and a 1sigma error on the sum of the neutrino masses that is comparable to the existing lower bound from oscillation measurements.Physical review D: Particles and fields 05/2012; 87(2). DOI:10.1103/PhysRevD.87.023527 · 4.86 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present a detection of the unnormalized skewness <T^3> induced by the thermal SunyaevZel'dovich (tSZ) effect in filtered Atacama Cosmology Telescope (ACT) 148 GHz cosmic microwave background temperature maps. Contamination due to infrared and radio sources is minimized by template subtraction of resolved sources and by constructing a mask using outlying values in the 218 GHz (tSZnull) ACT maps. We measure <T^3>= 31 + 6 \mu K^3 (measurement error only) or + 14 \mu K^3 (including cosmic variance error) in the filtered ACT data, a 5sigma detection. We show that the skewness is a sensitive probe of sigma_8, and use analytic calculations and tSZ simulations to obtain cosmological constraints from this measurement. From this signal alone we infer a value of sigma_8= 0.79 +0.03 0.03 (68 % C.L.) +0.06 0.06 (95 % C.L.). Our results demonstrate that measurements of nonGaussianity can be a useful method for characterizing the tSZ effect and extracting the underlying cosmological information.Physical Review D 03/2012; 86(12). DOI:10.1103/PhysRevD.86.122005 · 4.86 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present followup observations with the SunyaevZel'dovich Array (SZA) of opticallyconfirmed galaxy clusters found in the equatorial survey region of the Atacama Cosmology Telescope (ACT): ACTCL J00220036, ACTCL J2051+0057, and ACTCL J2337+0016. ACTCL J00220036 is a newlydiscovered, massive (10^15 Msun), highredshift (z=0.81) cluster revealed by ACT through the SunyaevZel'dovich effect (SZE). Deep, targeted observations with the SZA allow us to probe a broader range of cluster spatial scales, better disentangle cluster decrements from radio point source emission, and derive more robust integrated SZE flux and mass estimates than we can with ACT data alone. For the two clusters we detect with the SZA we compute integrated SZE signal and derive masses from the SZA data only. ACTCL J2337+0016, also known as Abell 2631, has archival Chandra data that allow an additional Xraybased mass estimate. Optical richness is also used to estimate cluster masses and shows good agreement with the SZE and Xraybased estimates. Based on the point sources detected by the SZA in these three cluster fields and an extrapolation to ACT's frequency, we estimate that point sources could be contaminating the SZE decrement at the <= 20% level for some fraction of clusters.The Astrophysical Journal 08/2011; 751(1). DOI:10.1088/0004637X/751/1/12 · 5.99 Impact Factor
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256  Citations  
81.74  Total Impact Points  
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20142015

Columbia University
New York, New York, United States


20112014

Princeton University
Princeton, New Jersey, United States
