Hutchings J.B.,Herzberg Institute for Astrophysics |
Bianchi L.,Johns Hopkins University
Astronomical Journal | Year: 2010
We discuss a sample of ∼60,000 objects from the combined Sloan Digital Sky Survey-Galaxy Evolution Explorer (SDSS-GALEX) database with UV-optical colors that should isolate QSOs in the redshift range 0.5-1.5. We use SDSS spectra of a subsample of ∼4500 to remove stellar and galaxy contaminants in the sample to a very high level, based on the 7-band photometry. We discuss the distributions of redshift, luminosity, and reddening of the 19,100 QSOs (∼96%) that we estimate to be present in the final sample of 19,812 point sources. The catalog is available as an online table. 2010. The American Astronomical Society. All rights reserved. Printed in the U.S.A.
Wesson P.S.,University of Waterloo |
Wesson P.S.,Herzberg Institute for Astrophysics
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011
In 5D, I take the metric in canonical form and define causality by null-paths. Then spacetime is modulated by a factor equivalent to the wave function, and the 5D geodesic equation gives the 4D Klein-Gordon equation. These results effectively show how general relativity and quantum mechanics may be unified in 5D. © 2011 Elsevier B.V.
McConnachie A.W.,Herzberg Institute for Astrophysics
Astronomical Journal | Year: 2012
Positional, structural, and dynamical parameters for all dwarf galaxies in and around the Local Group are presented, and various aspects of our observational understanding of this volume-limited sample are discussed. Over 100 nearby galaxies that have distance estimates reliably placing them within 3Mpc of the Sun are identified. This distance threshold samples dwarfs in a large range of environments, from the satellite systems of the MW and M31, to the quasi-isolated dwarfs in the outer regions of the Local Group, to the numerous isolated galaxies that are found in its surroundings. It extends to, but does not include, the galaxies associated with the next nearest groups, such as Maffei, Sculptor, and IC 342. Our basic knowledge of this important galactic subset and their resolved stellar populations will continue to improve dramatically over the coming years with existing and future observational capabilities, and they will continue to provide the most detailed information available on numerous aspects of dwarf galaxy formation and evolution. Basic observational parameters, such as distances, velocities, magnitudes, mean metallicities, as well as structural and dynamical characteristics, are collated, homogenized (as far as possible), and presented in tables that will be continually updated to provide a convenient and current online resource. As well as discussing the provenance of the tabulated values and possible uncertainties affecting their usage, the membership and spatial extent of the MW sub-group, M31 sub-group, and the Local Group are explored. The morphological diversity of the entire sample and notable sub-groups is discussed, and timescales are derived for the Local Group members in the context of their orbital/interaction histories. The scaling relations and mean stellar metallicity trends defined by the dwarfs are presented, and the origin of a possible "floor" in central surface brightness (and, more speculatively, stellar mean metallicity) at faint magnitudes is considered. © 2012. National Research Council Canada. All rights reserved.
Willott C.J.,Herzberg Institute for Astrophysics |
Omont A.,CNRS Paris Institute of Astrophysics |
Bergeron J.,CNRS Paris Institute of Astrophysics
Astrophysical Journal | Year: 2013
We present Atacama Large Millimeter Array observations of rest-frame far-infrared continuum and [C II] line emission in two z = 6.4 quasars with black hole masses of 108 M ⊙. CFHQS J0210-0456 is detected in the continuum with a 1.2 mm flux of 120 ± 35 μJy, whereas CFHQS J2329-0301 is undetected at a similar noise level. J2329-0301 has a star formation rate limit of <40 M ⊙ yr-1, considerably below the typical value at all redshifts for this bolometric luminosity. Through comparison with hydro simulations, we speculate that this quasar is observed at a relatively rare phase where quasar feedback has effectively shut down star formation in the host galaxy. [C II] emission is also detected only in J0210-0456. The ratio of [C II] to far-infrared luminosity is similar to that of low-redshift galaxies of comparable luminosity, suggesting that the previous finding of an offset in the relationships between this ratio and far-infrared luminosity at low and high redshifts may be partially due to a selection effect due to the limited sensitivity of previous continuum data. The [C II] line of J0210-0456 is relatively narrow (FWHM = 189 ± 18 km s-1), indicating a dynamical mass substantially lower than expected from the local black hole-velocity dispersion correlation. The [C II] line is marginally resolved at 0.″7 resolution with the blue and red wings spatially offset by 0.″5 (3 kpc) and a smooth velocity gradient of 100 km s-1 across a scale of 6 kpc, possibly due to the rotation of a galaxy-wide disk. These observations are consistent with the idea that stellar mass growth lags black hole accretion for quasars at this epoch with respect to more recent times. © 2013. The American Astronomical Society. All rights reserved.
Gwyn S.D.J.,Herzberg Institute for Astrophysics
Astronomical Journal | Year: 2012
This paper describes the image stacks and catalogs of the Canada-France-Hawaii Telescope Legacy Survey produced using the MegaPipe data pipeline at the Canadian Astronomy Data Centre. The Legacy Survey is divided into two parts. The Deep Survey consists of four fields each of 1deg 2, with magnitude limits (50% completeness for point sources) of u = 27.5, g = 27.9, r = 27.7, i = 27.4, and z = 26.2. It contains 1.6 × 10 6 sources. The Wide Survey consists of 150deg 2 split over four fields, with magnitude limits of u = 26.0, g = 26.5, r = 25.9, i = 25.7, and z = 24.6. It contains 3 × 10 7 sources. This paper describes the calibration, image stacking, and catalog generation process. The images and catalogs are available on the web through several interfaces: normal image and text file catalog downloads, a "Google Sky" interface, an image cutout service, and a catalog database query service. © 2012. National Research Council Canada. All rights reserved.