Hawaii, HI, United States
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Moustakas J.,Siena College | Coil A.L.,University of California at San Diego | Aird J.,Durham University | Blanton M.R.,New York University | And 7 more authors.
Astrophysical Journal | Year: 2013

We measure the evolution of the stellar mass function (SMF) from z = 0-1 using multi-wavelength imaging and spectroscopic redshifts from the PRism MUlti-object Survey (PRIMUS) and the Sloan Digital Sky Survey (SDSS). From PRIMUS we construct an i < 23 flux-limited sample of ∼40, 000 galaxies at z = 0.2-1.0 over five fields totaling ≈5.5 deg2, and from the SDSS we select ∼170, 000 galaxies at z = 0.01-0.2 that we analyze consistently with respect to PRIMUS to minimize systematic errors in our evolutionary measurements. We find that the SMF of all galaxies evolves relatively little since z = 1, although we do find evidence for mass assembly downsizing; we measure a ≈30% increase in the number density of ∼10 10M⊙ galaxies since z ≈ 0.6, and a ≲ 10% change in the number density of all ≳ 1011M⊙ galaxies since z ≈ 1. Dividing the sample into star-forming and quiescent using an evolving cut in specific star formation rate, we find that the number density of ∼1010M⊙ star-forming galaxies stays relatively constant since z ≈ 0.6, whereas the space density of ≳ 1011M⊙ star-forming galaxies decreases by ≈50% between z ≈ 1 and z ≈ 0. Meanwhile, the number density of ∼10 10M⊙ quiescent galaxies increases steeply toward low redshift, by a factor of ∼2-3 since z ≈ 0.6, while the number of massive quiescent galaxies remains approximately constant since z ≈ 1. These results suggest that the rate at which star-forming galaxies are quenched increases with decreasing stellar mass, but that the bulk of the stellar mass buildup within the quiescent population occurs around ∼1010.8 . In addition, we conclude that mergers do not appear to be a dominant channel for the stellar mass buildup of galaxies at z < 1, even among massive (≳ 10 11M⊙ ) quiescent galaxies. © 2013. The American Astronomical Society. All rights reserved.


Morrison G.E.,University of Hawaii at Manoa | Morrison G.E.,Canada France Hawaii Telescope Corporation | Owen F.N.,U.S. National Radio Astronomy Observatory | Dickinson M.,National Optical Astronomy Observatory | And 3 more authors.
Astrophysical Journal, Supplement Series | Year: 2010

We describe deep, new, wide-field radio continuum observations of the Great Observatories Origins Deep Survey-North field. The resulting map has a synthesized beam size of ∼1.7 and an rms noise level of ∼3.9 μJy beam -1 near its center and ∼8 μJy beam -1 at 15′ from phase center. We have cataloged 1230 discrete radio emitters, within a 40′ × 40′ region, above a 5σ detection threshold of ∼20 μJy at the field center. New techniques, pioneered by Owen & Morrison, have enabled us to achieve a dynamic range of 6800:1 in a field that has significantly strong confusing sources. We compare the 1.4 GHz (20 cm) source counts with those from other published radio surveys. Our differential counts are nearly Euclidean below 100 μJy with a median source diameter of ∼1.2. This adds to the evidence presented by Owen & Morrison that the natural confusion limit may lie near 1 μJy. If the Euclidean slope of the counts continues down to the natural confusion limit as an extrapolation of our log N-log S, this indicates that the cutoff must be fairly sharp below 1 μJy else the cosmic microwave background temperature would increase above 2.7 K at 1.4 GHz. © 2010. The American Astronomical Society. All rights reserved.


Platais I.,Johns Hopkins University | Gosnell N.M.,University of Wisconsin - Madison | Meibom S.,Harvard - Smithsonian Center for Astrophysics | Kozhurina-Platais V.,US Space Telescope Science Institute | And 3 more authors.
Astronomical Journal | Year: 2013

We present proper motions and astrometric membership analysis for 15,750 stars around the intermediate-age open cluster NGC 6819. The accuracy of relative proper motions for well-measured stars ranges from ∼0.2 mas yr-1 within 10' of the cluster center to 1.1 mas yr-1 outside this radius. In the proper motion vector-point diagram, the separation between the cluster members and field stars is convincing down to V ∼ 18 and within 10' from the cluster center. The formal sum of membership probabilities indicates a total of ∼2500 cluster members down to V ∼ 22. We confirm the cluster membership of several variable stars, including some eclipsing binaries. The estimated absolute proper motion of NGC 6819 is μx a bs = -2.6±0.5 andμy a bs = -4.2 ±0.5 mas yr-1. A cross-identification between the proper motion catalog and a list of X-ray sources in the field of NGC 6819 resulted in a number of new likely optical counterparts, including a candidate CV. For the first time we show that there is significant differential reddening toward NGC 6819. © 2013. The American Astronomical Society. All rights reserved. Printed in the U.S.A.


Platais I.,Johns Hopkins University | Cudworth K.M.,University of Chicago | Kozhurina-Platais V.,US Space Telescope Science Institute | McLaughlin D.E.,Keele University | And 2 more authors.
Astrophysical Journal Letters | Year: 2011

We present comprehensive cluster membership and g′r′ photometry of the prototypical old, metal-rich Galactic star cluster NGC6791. The proper-motion catalog contains 58,901 objects down to g′ 24, limited to a circular area of radius 30′. The highest precision of the proper motions is 0.08 mas yr-1. Our proper motions confirm cluster membership of all main and also some rare constituents of NGC6791. The total number of probable cluster members down to g′ = 22 (MV +8) is 4800, corresponding to M tot 5000 M. New findings include an extended horizontal branch in this cluster. The angular radius of NGC6791 is at least 15′ (the effective radius is Rh ≃ 44 while the tidal radius is rt ≃ 23′). The luminosity function of the cluster peaks at 4.5 and then steadily declines toward fainter magnitudes. Our data provide evidence that differential reddening may not be ignored in NGC6791. © 2011. The American Astronomical Society. All rights reserved.


Duc P.-A.,University Paris Diderot | Paudel S.,University Paris Diderot | McDermid R.M.,Gemini Observatory | Cuillandre J.-C.,Canada France Hawaii Telescope Corporation | And 5 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2014

It has recently been proposed that the dwarf spheroidal galaxies located in the Local Group discs of satellites (DoSs) may be tidal dwarf galaxies (TDGs) born in a major merger at least 5Gyr ago. Whether TDGs can live that long is still poorly constrained by observations. As part of deep optical and HI surveys with the Canada-France-Hawaii Telescope (CFHT) MegaCam camera and Westerbork Synthesis Radio Telescope made within the ATLAS3D project, and follow-up spectroscopic observations with the Gemini-North telescope, we have discovered old TDG candidates around several early-type galaxies. At least one of them has an oxygen abundance close to solar, as expected for a tidal origin. This confirmed pre-enriched object is located within the gigantic, but very low surface brightness, tidal tail that emanates from the elliptical galaxy, NGC 5557. An age of 4 Gyr estimated from its SED fitting makes it the oldest securely identified TDG ever found so far. We investigated the structural and gaseous properties of the TDG and of a companion located in the same collisional debris, and thus most likely of tidal origin as well. Despite several Gyr of evolution close to their parent galaxies, they kept a large gas reservoir. Their central surface brightness is low and their effective radius much larger than that of typical dwarf galaxies of the same mass. This possibly provides us with criteria to identify tidal objects which can be more easily checked than the traditional ones requiring deep spectroscopic observations. In view of the above, we discuss the survival time of TDGs and question the tidal origin of the DoSs. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


Croll B.,University of Toronto | Lafreniere D.,University of Montréal | Albert L.,Canada France Hawaii Telescope Corporation | Jayawardhana R.,University of Toronto | And 2 more authors.
Astronomical Journal | Year: 2011

We present Ks, H, &J-band photometry of the very highly irradiated hot Jupiter WASP-12b using the Widefield Infrared Camera on the Canada-France-Hawaii telescope. Our photometry brackets the secondary eclipse of WASP-12b in the Ks and H bands, and in J band starts in mid-eclipse and continues until well after the end of the eclipse. We detect its thermal emission in all three near-infrared bands. Our secondary eclipse depths are 0.309 +0.013 -0.012% in Ks band (24σ), 0.176+0.016 -0.021% in H band (9σ), and 0.131+0.027 -0.029% in J band (4σ). All three secondary eclipses are best fit with a consistent phase, φ , that is compatible with a circular orbit: φ = 0.4998+0.0008 -0.0007. The limits on the eccentricity, e, and argument of periastron, ω, of this planet from our photometry alone are thus |ecos?| < 0.0040. By combining our secondary eclipse times with others published in the literature, as well as the radialvelocity and transit-timing data for this system, we show that there is no evidence that WASP-12b is precessing at a detectable rate and that its orbital eccentricity is likely zero. Our thermal-emission measurements also allow us to constrain the characteristics of the planet's atmosphere; our Ks-band eclipse depth argues strongly in favor of inefficient day to nightside redistribution of heat and a low Bond albedo for this very highly irradiated hot Jupiter. The J- and H-band brightness temperatures are slightly cooler than the Ks-band brightness temperature, and thus hint at the possibility of a modest temperature inversion deep in the atmosphere of WASP-12b; the high-pressure, deep atmospheric layers probed by our J- and H-band observations are likely more homogenized than the higher altitude layer probed by our Ks-band observations. Lastly, our best-fit Ks-band eclipse has a marginally longer duration than would otherwise be expected; this may be tentative evidence for material being tidally stripped from the planet-as was predicted for this system by Li and collaborators, and for which observational confirmation was recently arguably provided by Fossati and collaborators. © 2011. The American Astronomical Society.


Croll B.,University of Toronto | Albert L.,Canada France Hawaii Telescope Corporation | Lafreniere D.,University of Montréal | Jayawardhana R.,University of Toronto | Fortney J.J.,University of California at Santa Cruz
Astrophysical Journal | Year: 2010

We present near-infrared Ks-band photometry bracketing the secondary eclipse of the hot Jupiter TrES-2b using the Wide-field Infrared Camera on the Canada-France-Hawaii Telescope. We detect its thermal emission with an eclipse depth of 0.062+0.013 -0.011% (5σ). Our best-fit secondary eclipse is consistent with a circular orbit (a 3σ upper limit on the eccentricity, ℓ, and argument or periastron, ω, of |ℓ cos ω| < 0.0090), in agreement with mid-infrared detections of the secondary eclipse of this planet. A secondary eclipse of this depth corresponds to a dayside Ks-band brightness temperature of TB = 1636 +79 -88K. Our thermal emission measurement, when combined with the thermal emission measurements using Spitzer/IRAC from O'Donovan and collaborators, suggests that this planet exhibits relatively efficient dayside to nightside redistribution of heat and a near isothermal dayside atmospheric temperature structure, whose spectrum is well approximated by a blackbody. It is unclear if the atmosphere of TrES-2b requires a temperature inversion; if it does it is likely due to chemical species other than TiO/VO as the atmosphere of TrES-2b is too cool to allow TiO/VO to remain in gaseous form. Our secondary eclipse has the smallest depth of any detected from the ground, at around 2 μm, to date. © 2010. The American Astronomical Society. All rights reserved.


Croll B.,University of Toronto | Jayawardhana R.,University of Toronto | Fortney J.J.,University of California at Santa Cruz | Lafreniere D.,University of Montréal | Albert L.,Canada France Hawaii Telescope Corporation
Astrophysical Journal | Year: 2010

We present H- and Ks-band photometry bracketing the secondary eclipse of the hot Jupiter TrES-3b using the Wide-field Infrared Camera on the Canada-France-Hawaii Telescope.We detect the secondary eclipse of TrES-3b with a depth of 0.133+0.018 -0.016% in the Ks band (8σ)-a result that is in sharp contrast to the eclipse depth reported by de Mooij & Snellen. We do not detect its thermal emission in the H band, but place a 3σ limit of 0.051% on the depth of the secondary eclipse in this band. A secondary eclipse of this depth in Ks requires very efficient day-to-nightside redistribution of heat and nearly isotropic reradiation, a conclusion that is in agreement with longer wavelength, mid-infrared Spitzer observations. Our 3σ upper limit on the depth of our H-band secondary eclipse also argues for very efficient redistribution of heat and suggests that the atmospheric layer probed by these observations may be well homogenized. However, our H-band upper limit is so constraining that it suggests the possibility of a temperature inversion at depth, or an absorbing molecule, such as methane, that further depresses the emitted flux at this wavelength. The combination of our near-infrared measurements and those obtained with Spitzer suggests that TrES-3b displays a near-isothermal dayside atmospheric temperature structure, whose spectrum is well approximated by a blackbody. We emphasize that our strict H-band limit is in stark disagreement with the best-fit atmospheric model that results from longer wavelength observations only, thus highlighting the importance of near-infrared observations at multiple wavelengths, in addition to those returned by Spitzer in the mid-infrared, to facilitate a comprehensive understanding of the energy budgets of transiting exoplanets. ©2010. The American Astronomical Society. All rights reserved.


Petit P.,CNRS Institute for research in astrophysics and planetology | Louge T.,CNRS Institute for research in astrophysics and planetology | Theado S.,CNRS Institute for research in astrophysics and planetology | Paletou F.,CNRS Institute for research in astrophysics and planetology | And 4 more authors.
Publications of the Astronomical Society of the Pacific | Year: 2014

PolarBase is an evolving database that contains all stellar data collected with the ESPaDOnS and NARVAL high-resolution spectropolarimeters, in their reduced form, as soon as they become public. As of early 2014, observations of 2000 stellar objects throughout the Hertzsprung-Russell diagram are available. Intensity spectra are available for all targets, and the majority of the observations also include simultaneous spectra in circular or linear polarization, with the majority of the polarimetric measurements being performed only in circularly polarized light (Stokes V). Observations are associated with a cross-correlation pseudoline profile in all available Stokes parameters, greatly increasing the detectability of weak polarized signatures. Stokes V signatures are detected for more than 300 stars of all masses and evolutionary stages, and linear polarization is detected in 35 targets. The detection rate in Stokes V is found to be anticorrelated with the stellar effective temperature. This unique set of Zeeman detections offers the first opportunity to run homogeneous magnetometry studies throughout the H-R diagram. The Web interface of PolarBase is available at http://polarbase.irap.omp.eu. © 2014. The Astronomical Society of the Pacific. All rights reserved.


Barrick G.A.,Canada France Hawaii Telescope Corporation | Ward J.,Canada France Hawaii Telescope Corporation | Cuillandre J.-C.,Canada France Hawaii Telescope Corporation
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

The ESPaDOnS spectrograph at the Canada-France-Hawaii Telescope was recently upgraded to use an E2V CCD42-90 deep-depletion CCD. While changing to this device from a standard silicon CCD42-90 had many benefits such as much higher red QE and much lower fringing, it was also found that the new device exhibited persistence. After talking with E2V, a solution to the persistence was found, but this resulted in reduced resolution on the spectrograph from charge diffusion. This paper will describe the solution found to allow the detector to run with no persistence and with limited charge diffusion. © 2012 SPIE.

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