arXiv subjects

J. D. Vieira

Publications and source records attributed to J. D. Vieira.

At least 145 records · Page 8Linked to original sources

arXiv2013

The suppression of star formation by powerful active galactic nuclei

The old, red stars which constitute the bulges of galaxies, and the massive black holes at their centres, are the relics of a period in cosmic history when galaxies formed stars at remarkable rates and active galactic nuclei (AGN) shone brightly from accretion onto black holes. It is widely suspected, but unproven, that the tight correlation in mass of the black hole and stellar components results from the AGN quenching the surrounding star formation as it approaches its peak luminosity. X-rays trace emission from AGN unambiguously, while powerful star-forming galaxies are usually dust-obscured and are brightest at infrared to submillimetre wavelengths. Here we report observations in the submillimetre and X-ray which show that rapid star formation was common in the host galaxies of AGN when the Universe was 2-6 Gyrs old, but that the most vigorous star formation is not observed around black holes above an X-ray luminosity of 10^44 erg/s. This suppression of star formation in the host galaxies of powerful AGN is a key prediction of models in which the AGN drives a powerful outflow, expelling the interstellar medium of its host galaxy and transforming the galaxy's properties in a brief period of cosmic time.

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arXiv2013

Gravitational Lens Models Based on Submillimeter Array Imaging of Herschel-selected Strongly Lensed Sub-millimeter Galaxies at z>1.5

Strong gravitational lenses are now being routinely discovered in wide-field surveys at (sub)millimeter wavelengths. We present Submillimeter Array (SMA) high-spatial resolution imaging and Gemini-South and Multiple Mirror Telescope optical spectroscopy of strong lens candidates discovered in the two widest extragalactic surveys conducted by the Herschel Space Observatory: the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) and the Herschel Multi-tiered Extragalactic Survey (HerMES). From a sample of 30 Herschel sources with S_500>100 mJy, 21 are strongly lensed (multiply imaged), 4 are moderately lensed (singly imaged), and the remainder require additional data to determine their lensing status. We apply a visibility-plane lens modeling technique to the SMA data to recover information about the masses of the lenses as well as the intrinsic (i.e., unlensed) sizes (r_half) and far-infrared luminosities (L_FIR) of the lensed submillimeter galaxies (SMGs). The sample of lenses comprises primarily isolated massive galaxies, but includes some groups and clusters as well. Several of the lenses are located at z_lens>0.7, a redshift regime that is inaccessible to lens searches based on Sloan Digital Sky Survey spectroscopy. The lensed SMGs are amplified by factors that are significantly below statistical model predictions given the 500um flux densities of our sample. We speculate that this may reflect a deficiency in our understanding of the intrinsic sizes and luminosities of the brightest SMGs. The lensed SMGs span nearly one decade in L_FIR (median L_FIR=7.9x10^12 L_sun) and two decades in FIR luminosity surface density (median Sigma_FIR=6.0x10^11 L_sun kpc^-2). The strong lenses in this sample and others identified via (sub-)mm surveys will provide a wealth of information regarding the astrophysics of galaxy formation and evolution over a wide range in redshift.

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arXiv2013

The Spitzer-South Pole Telescope Deep Field: Survey Design and IRAC Catalogs

The Spitzer-South Pole Telescope Deep Field (SSDF) is a wide-area survey using Spitzer's Infrared Array Camera (IRAC) to cover 94 square degrees of extragalactic sky, making it the largest IRAC survey completed to date outside the Milky Way midplane. The SSDF is centered at 23:30,-55:00, in a region that combines observations spanning a broad wavelength range from numerous facilities. These include millimeter imaging from the South Pole Telescope, far-infrared observations from Herschel/SPIRE, X-ray observations from the XMM XXL survey, near-infrared observations from the VISTA Hemisphere Survey, and radio-wavelength imaging from the Australia Telescope Compact Array, in a panchromatic project designed to address major outstanding questions surrounding galaxy clusters and the baryon budget. Here we describe the Spitzer/IRAC observations of the SSDF, including the survey design, observations, processing, source extraction, and publicly available data products. In particular, we present two band-merged catalogs, one for each of the two warm IRAC selection bands. They contain roughly 5.5 and 3.7 million distinct sources, the vast majority of which are galaxies, down to the SSDF 5-sigma sensitivity limits of 19.0 and 18.2 Vega mag (7.0 and 9.4 microJy) at 3.6 and 4.5 microns, respectively.

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arXiv2013

A direct measurement of the linear bias of mid-infrared-selected quasars at z~1 using cosmic microwave background lensing

We measure the cross-power spectrum of the projected mass density as traced by the convergence of the cosmic microwave background lensing field from the South Pole Telescope (SPT) and a sample of Type 1 and 2 (unobscured and obscured) quasars at z~1 selected with the Wide-field Infrared Survey Explorer, over 2500 deg^2. The cross-power spectrum is detected at ~7-sigma, and we measure a linear bias b=1.67+/-0.24, consistent with clustering analyses. Using an independent lensing map, derived from Planck observations, to measure the cross-spectrum, we find excellent agreement with the SPT analysis. The bias of the combined sample of Type 1 and 2 quasars determined in this work is similar to that previously determined for Type 1 quasars alone; we conclude that that obscured and unobscured quasars must trace the matter field in a similar way. This result has implications for our understanding of quasar unification and evolution schemes.

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arXiv2013

Detection of B-mode Polarization in the Cosmic Microwave Background with Data from the South Pole Telescope

Gravitational lensing of the cosmic microwave background generates a curl pattern in the observed polarization. This "B-mode" signal provides a measure of the projected mass distribution over the entire observable Universe and also acts as a contaminant for the measurement of primordial gravity-wave signals. In this Letter we present the first detection of gravitational lensing B modes, using first-season data from the polarization-sensitive receiver on the South Pole Telescope (SPTpol). We construct a template for the lensing B-mode signal by combining E-mode polarization measured by SPTpol with estimates of the lensing potential from a Herschel-SPIRE map of the cosmic infrared background. We compare this template to the B modes measured directly by SPTpol, finding a non-zero correlation at 7.7 sigma significance. The correlation has an amplitude and scale-dependence consistent with theoretical expectations, is robust with respect to analysis choices, and constitutes the first measurement of a powerful cosmological observable.

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arXiv2013

SPT 0538-50: Physical conditions in the ISM of a strongly lensed dusty star-forming galaxy at z=2.8

We present observations of SPT-S J053816-5030.8, a gravitationally-lensed dusty star forming galaxy (DSFG) at z = 2.7817, first discovered at millimeter wavelengths by the South Pole Telescope. SPT 0538-50 is typical of the brightest sources found by wide-field millimeter-wavelength surveys, being lensed by an intervening galaxy at moderate redshift (in this instance, at z = 0.441). We present a wide array of multi-wavelength spectroscopic and photometric data on SPT 0538-50, including data from ALMA, Herschel PACS and SPIRE, Hubble, Spitzer, VLT, ATCA, APEX, and the SMA. We use high resolution imaging from HST to de-blend SPT 0538-50, separating DSFG emission from that of the foreground lens. Combined with a source model derived from ALMA imaging (which suggests a magnification factor of 21 +/- 4), we derive the intrinsic properties of SPT 0538-50, including the stellar mass, far-IR luminosity, star formation rate, molecular gas mass, and - using molecular line fluxes - the excitation conditions within the ISM. The derived physical properties argue that we are witnessing compact, merger-driven star formation in SPT 0538-50, similar to local starburst galaxies, and unlike that seen in some other DSFGs at this epoch.

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arXiv2013

The Growth of Cool Cores and Evolution of Cooling Properties in a Sample of 83 Galaxy Clusters at 0.3 < z < 1.2 Selected from the SPT-SZ Survey

We present first results on the cooling properties derived from Chandra X-ray observations of 83 high-redshift (0.3 < z < 1.2) massive galaxy clusters selected by their Sunyaev-Zel'dovich signature in the South Pole Telescope data. We measure each cluster's central cooling time, central entropy, and mass deposition rate, and compare to local cluster samples. We find no significant evolution from z~0 to z~1 in the distribution of these properties, suggesting that cooling in cluster cores is stable over long periods of time. We also find that the average cool core entropy profile in the inner ~100 kpc has not changed dramatically since z ~ 1, implying that feedback must be providing nearly constant energy injection to maintain the observed "entropy floor" at ~10 keV cm^2. While the cooling properties appear roughly constant over long periods of time, we observe strong evolution in the gas density profile, with the normalized central density (rho_0/rho_crit) increasing by an order of magnitude from z ~ 1 to z ~ 0. When using metrics defined by the inner surface brightness profile of clusters, we find an apparent lack of classical, cuspy, cool-core clusters at z > 0.75, consistent with earlier reports for clusters at z > 0.5 using similar definitions. Our measurements indicate that cool cores have been steadily growing over the 8 Gyr spanned by our sample, consistent with a constant, ~150 Msun/yr cooling flow that is unable to cool below entropies of 10 keV cm^2 and, instead, accumulates in the cluster center. We estimate that cool cores began to assemble in these massive systems at z ~ 1, which represents the first constraints on the onset of cooling in galaxy cluster cores. We investigate several potential biases which could conspire to mimic this cool core evolution and are unable to find a bias that has a similar redshift dependence and a substantial amplitude.

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arXiv2013

H-ATLAS: estimating redshifts of Herschel sources from sub-mm fluxes

Upon its completion the Herschel ATLAS (H-ATLAS) will be the largest submillimetre survey to date, detecting close to half-a-million sources. It will only be possible to measure spectroscopic redshifts for a small fraction of these sources. However, if the rest-frame spectral energy distribution (SED) of a typical H-ATLAS source is known, this SED and the observed Herschel fluxes can be used to estimate the redshifts of the H-ATLAS sources without spectroscopic redshifts. In this paper, we use a subset of 40 H-ATLAS sources with previously measured redshifts in the range 0.5 1 we estimate that the rms of Delta z/(1+z) = 0.12. We have used this template to estimate the redshift distribution for the sources detected in the H-ATLAS equatorial fields, finding a bimodal distribution with a mean redshift of 1.2, 1.9 and 2.5 for 250, 350 and 500 um selected sources respectively. \end{abstract}

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arXiv2013

Keck-I MOSFIRE spectroscopy of the z~12 candidate galaxy UDFj-39546284

We report the results of deep (4.6h) H band spectroscopy of the well studied z~12 H-band dropout galaxy candidate UDFj-39546284 with MOSFIRE on Keck-I. These data reach a sensitivity of 5-10 x 10^-19 erg s^-1 cm^-2 per 4.4 Angstrom resolution element between sky lines. Previous papers have argued this source could either be a large equivalent width line emitting galaxy at 2<z<3.5 or a luminous galaxy at z~12. We find a 2.2 sigma peak associated with a line candidate in deep Hubble-Space-Telescope Wide-Field-Camera 3 Infrared grism observations, but at a lower flux than what was expected. After considering several possibilities we conclude these data can not conclusively confirm or reject the previous line detection, and significantly deeper spectroscopic observations are required. We also search for low-redshift emission lines in ten other 7<z<10 z, Y, and J-dropout candidates in our mask and find no significant detections.

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arXiv2013

Extragalactic millimeter-wave point source catalog, number counts and statistics from 771 square degrees of the SPT-SZ Survey

We present a point source catalog from 771 square degrees of the South Pole Telescope Sunyaev Zel'dovich (SPT-SZ) survey at 95, 150, and 220 GHz. We detect 1545 sources above 4.5 sigma significance in at least one band. Based on their relative brightness between survey bands, we classify the sources into two populations, one dominated by synchrotron emission from active galactic nuclei, and one dominated by thermal emission from dust-enshrouded star-forming galaxies. We find 1238 synchrotron and 307 dusty sources. We cross-match all sources against external catalogs and find 189 unidentified synchrotron sources and 189 unidentified dusty sources. The dusty sources without counterparts are good candidates for high-redshift, strongly lensed submillimeter galaxies. We derive number counts for each population from 1 Jy down to roughly 9, 5, and 11 mJy at 95, 150, and 220 GHz. We compare these counts with galaxy population models and find that none of the models we consider for either population provide a good fit to the measured counts in all three bands. The disparities imply that these measurements will be an important input to the next generation of millimeter-wave extragalactic source population models.

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arXiv2013

HerMES: Cosmic Infrared Background Anisotropies and the Clustering of Dusty Star-Forming Galaxies

We present measurements of the auto- and cross-frequency power spectra of the cosmic infrared background (CIB) at 250, 350, and 500um (1200, 860, and 600 GHz) from observations totaling ~ 70 deg^2 made with the SPIRE instrument aboard the Herschel Space Observatory. We measure a fractional anisotropy dI / I = 14 +- 4%, detecting signatures arising from the clustering of dusty star-forming galaxies in both the linear (2-halo) and non-linear (1-halo) regimes; and that the transition from the 2- to 1-halo terms, below which power originates predominantly from multiple galaxies within dark matter halos, occurs at k_theta ~ 0.1 - 0.12 arcmin^-1 (l ~ 2160 - 2380), from 250 to 500um. New to this paper is clear evidence of a dependence of the Poisson and 1-halo power on the flux-cut level of masked sources --- suggesting that some fraction of the more luminous sources occupy more massive halos as satellites, or are possibly close pairs. We measure the cross-correlation power spectra between bands, finding that bands which are farthest apart are the least correlated, as well as hints of a reduction in the correlation between bands when resolved sources are more aggressively masked. In the second part of the paper we attempt to interpret the measurements in the framework of the halo model. With the aim of fitting simultaneously with one model the power spectra, number counts, and absolute CIB level in all bands, we find that this is achievable by invoking a luminosity-mass relationship, such that the luminosity-to-mass ratio peaks at a particular halo mass scale and declines towards lower and higher mass halos. Our best-fit model finds that the halo mass which is most efficient at hosting star formation in the redshift range of peak star-forming activity, z ~ 1-3, is log(M_peak/M_sun) ~ 12.1 +- 0.5, and that the minimum halo mass to host infrared galaxies is log(M_min/M_sun) ~ 10.1 +- 0.6.

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arXiv2013

The rapid assembly of an elliptical galaxy of 400 billion solar masses at a redshift of 2.3

Stellar archeology shows that massive elliptical galaxies today formed rapidly about ten billion years ago with star formation rates above several hundreds solar masses per year (M_sun/yr). Their progenitors are likely the sub-millimeter-bright galaxies (SMGs) at redshifts (z) greater than 2. While SMGs' mean molecular gas mass of 5x10^10 M_sun can explain the formation of typical elliptical galaxies, it is inadequate to form ellipticals that already have stellar masses above 2x10^11 M_sun at z ~ 2. Here we report multi-wavelength high-resolution observations of a rare merger of two massive SMGs at z = 2.3. The system is currently forming stars at a tremendous rate of 2,000 M_sun/yr. With a star formation efficiency an order-of-magnitude greater than that of normal galaxies, it will quench the star formation by exhausting the gas reservoir in only ~200 million years. At a projected separation of 19 kiloparsecs, the two massive starbursts are about to merge and form a passive elliptical galaxy with a stellar mass of ~4x10^11 M_sun. Our observations show that gas-rich major galaxy mergers, concurrent with intense star formation, can form the most massive elliptical galaxies by z ~ 1.5.

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arXiv2013

Large gas reservoirs and free-free emission in two lensed star-forming galaxies at z=2.7

We report the detection of CO(1-0) line emission in the bright, lensed star-forming galaxies SPT-S 233227-5358.5 (z=2.73) and SPT-S 053816-5030.8 (z=2.78), using the Australia Telescope Compact Array (ATCA). Both galaxies were discovered in a large-area millimeter survey with the South Pole Telescope (SPT) and found to be gravitationally lensed by intervening structures. The measured CO intensities imply galaxies with molecular gas masses of (3.2 \pm 0.5)x10^10 (mu/15)^{-1}(X_CO/0.8) M_sun and (1.7 \pm 0.3)x10^10 (mu/20)^{-1}(X_CO/0.8) M_sun, and gas depletion timescales of 4.9x10^7 (X_CO/0.8) yr and 2.6x10^7 (X_CO/0.8) yr, respectively, where mu corresponds to the lens magnification and X_CO is the CO luminosity to gas mass conversion factor. In the case of SPT-S 053816-5030.8, we also obtained significant detections of the rest-frame 115.7 and 132.4 GHz radio continuum. Based on the radio to infrared spectral energy distribution and an assumed synchrotron spectral index, we find that 42 \pm 10 % and 55 \pm 13 % of the flux at rest-frame 115.7 and 132.4 GHz arise from free-free emission. We find a radio-derived intrinsic star formation rate (SFR) of 470 \pm 170 M_sun/yr, consistent within the uncertainties with the infrared estimate. Based on the morphology of this object in the source plane, the derived gas mass and the possible flattening of the radio spectral index towards low frequencies, we argue that SPT-S 053816-5030.8 exhibits properties compatible with a scaled-up local ultra-luminous infrared galaxy.

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arXiv2013

CAST constraints on the axion-electron coupling

In non-hadronic axion models, which have a tree-level axion-electron interaction, the Sun produces a strong axion flux by bremsstrahlung, Compton scattering, and axio-recombination, the "BCA processes." Based on a new calculation of this flux, including for the first time axio-recombination, we derive limits on the axion-electron Yukawa coupling g_ae and axion-photon interaction strength g_ag using the CAST phase-I data (vacuum phase). For m_a < 10 meV/c2 we find g_ag x g_ae< 8.1 x 10^-23 GeV^-1 at 95% CL. We stress that a next-generation axion helioscope such as the proposed IAXO could push this sensitivity into a range beyond stellar energy-loss limits and test the hypothesis that white-dwarf cooling is dominated by axion emission.

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arXiv2013

HerMES: deep number counts at 250, 350, and 500 microns in the COSMOS and GOODS-N fields and the build-up of the cosmic infrared background

ABRIGED Herschel/SPIRE has provided confusion limited maps of deep fields at 250, 350, and 500um, as part of the HerMES survey. Due to confusion, only a small fraction of the Cosmic Infrared Background can be resolved into individually-detected sources. Our goal is to produce deep galaxy number counts and redshift distributions below the confusion limit, which we then use to place strong constraints on the origins of the cosmic infrared background and on models of galaxy evolution. We individually extracted the bright SPIRE with a method using the positions, the flux densities, and the redshifts of the 24um sources as a prior, and derived the number counts and redshift distributions of the bright SPIRE sources. For fainter SPIRE sources, we reconstructed the number counts and the redshift distribution below the confusion limit using the deep 24um catalogs associated with photometric redshift and information provided by the stacking of these sources into the deep SPIRE maps. Finally, by integrating all these counts, we studied the contribution of the galaxies to the CIB as a function of their flux density and redshift. Through stacking, we managed to reconstruct the source counts per redshift slice down to ~2 mJy in the three SPIRE bands, which lies about a factor 10 below the 5sigma confusion limit. None of the pre-existing population models are able to reproduce our results at better than 3sigma. Finally, we extrapolate our counts to zero flux density in order to derive an estimate of the total contribution of galaxies to the CIB, finding 10.1, 6.5, and 2.8 nW/m2/sr at 250, 350, and 500um, respectively. These values agree well with FIRAS absolute measurements, suggesting our number counts and their extrapolation are sufficient to explain the CIB. Finally, combining our results with other works, we estimate the energy budget contained in the CIB between 8 and 1000um: 26 nW/m2/sr.

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arXiv2013

A Dust-Obscured Massive Maximum-Starburst Galaxy at a Redshift of 6.34

Massive present-day early-type (elliptical and lenticular) galaxies probably gained the bulk of their stellar mass and heavy elements through intense, dust-enshrouded starbursts - that is, increased rates of star formation - in the most massive dark matter halos at early epochs. However, it remains unknown how soon after the Big Bang such massive starburst progenitors exist. The measured redshift distribution of dusty, massive starbursts has long been suspected to be biased low in redshift owing to selection effects, as confirmed by recent findings of systems out to redshift z~5. Here we report the identification of a massive starburst galaxy at redshift 6.34 through a submillimeter color-selection technique. We unambiguously determined the redshift from a suite of molecular and atomic fine structure cooling lines. These measurements reveal a hundred billion solar masses of highly excited, chemically evolved interstellar medium in this galaxy, which constitutes at least 40% of the baryonic mass. A "maximum starburst" converts the gas into stars at a rate more than 2,000 times that of the Milky Way, a rate among the highest observed at any epoch. Despite the overall downturn of cosmic star formation towards the highest redshifts, it seems that environments mature enough to form the most massive, intense starbursts existed at least as early as 880 million years after the Big Bang.

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arXiv2013

A CMB lensing mass map and its correlation with the cosmic infrared background

We use a temperature map of the cosmic microwave background (CMB) obtained using the South Pole Telescope at 150 GHz to construct a map of the gravitational convergence to z ~ 1100, revealing the fluctuations in the projected mass density. This map shows individual features that are significant at the ~ 4 sigma level, providing the first image of CMB lensing convergence. We cross-correlate this map with Herschel/SPIRE maps covering 90 square degrees at wavelengths of 500, 350, and 250 microns. We show that these submillimeter-wavelength (submm) maps are strongly correlated with the lensing convergence map, with detection significances in each of the three submm bands ranging from 6.7 to 8.8 sigma. We fit the measurement of the cross power spectrum assuming a simple constant bias model and infer bias factors of b=1.3-1.8, with a statistical uncertainty of 15%, depending on the assumed model for the redshift distribution of the dusty galaxies that are contributing to the Herschel/SPIRE maps.

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arXiv2013

Dusty starburst galaxies in the early Universe as revealed by gravitational lensing

In the past decade, our understanding of galaxy evolution has been revolutionized by the discovery that luminous, dusty, starburst galaxies were 1,000 times more abundant in the early Universe than at present. It has, however, been difficult to measure the complete redshift 2 distribution of these objects, especially at the highest redshifts (z > 4). Here we report a redshift survey at a wavelength of three millimeters, targeting carbon monoxide line emission from the star-forming molecular gas in the direction of extraordinarily bright millimetrewave-selected sources. High-resolution imaging demonstrates that these sources are strongly gravitationally lensed by foreground galaxies. We detect spectral lines in 23 out of 26 sources and multiple lines in 12 of those 23 sources, from which we obtain robust, unambiguous redshifts. At least 10 of the sources are found to lie at z > 4, indicating that the fraction of dusty starburst galaxies at high redshifts is greater than previously thought. Models of lens geometries in the sample indicate that the background objects are ultra-luminous infrared galaxies, powered by extreme bursts of star formation.

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