The properties of Galactic molecular clouds tabulated by Solomon et al. (1987) (SRBY) are re-examined using the Boston University-FCRAO Galactic Ring Survey of 13 CO J=1-0 emission. These new data provide a lower opacity tracer of molecular clouds and improved angular and spectral resolution compared to previous surveys of molecular line emission along the Galactic Plane. We calculate GMC masses within the SRBY cloud boundaries assuming LTE conditions throughout the cloud and a constant H 2 to 13 CO abundance, while accounting for the variation of the 12 C/ 13 C with Galacto-centric radius. The LTE derived masses are typically five times smaller than the SRBY virial masses. The corresponding median mass surface density of molecular hydrogen for this sample is 42 M ⊙ pc −2 , which is significantly lower than the value derived by SRBY (median 206 M ⊙ pc −2 ) that has been widely adopted by most models of cloud evolution and star formation. This discrepancy arises from both the extrapolation by SRBY of velocity dispersion, size, and CO luminosity to the 1 K antenna temperature isophote that likely overestimates the GMC masses and our assumption of constant 13 CO abundance over the projected area of each cloud. Owing to the uncertainty of molecular abundances in the envelopes of clouds, the mass surface density of giant molecular clouds could be larger than the valued derived from our 13 CO measurements. From velocity dispersions derived from the 13 CO data, we find that the coefficient of the cloud structure functions, v • = σ v /R 1/2 , is not constant, as required to satisfy Larson's scaling relationships, but rather systematically varies with the surface density of the cloud as ∼ Σ 0.5 as expected for clouds in self-gravitational equilibrium.

We present the fifth edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog, which is based upon the SDSS Seventh Data Release. The catalog, which contains 105,783 spectroscopically confirmed quasars, represents the conclusion of the SDSS-I and SDSS-II quasar survey. The catalog consists of the SDSS objects that have luminosities larger than M i = −22.0 (in a cosmology with H 0 = 70 km s −1 Mpc −1 , Ω M = 0.3, and Ω Λ = 0.7), have at least one emission line with FWHM larger than 1000 km s −1 or have interesting/complex absorption features, are fainter than i ≈ 15.0, and have highly reliable redshifts. The catalog covers an area of ≈ 9380 deg 2 . The quasar redshifts range from 0.065 to 5.46, with a median value of 1.49; the catalog includes 1248 quasars at redshifts greater than four, of which 56 are at redshifts greater than five. The catalog contains 9210 quasars with i < 18; slightly over half of the entries have i < 19. For each object the catalog presents positions accurate to better than 0.1 ′′ rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3800-9200Å at a spectral resolution of ≃ 2000; the spectra can be retrieved from the SDSS public database using the information provided in the catalog. Over 96% of the objects in the catalog were discovered by the SDSS. We also include a supplemental list of an additional 207 quasars with SDSS spectra whose archive photometric information is incomplete.

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We explore the mid-infrared (mid-IR) through ultraviolet (UV) spectral energy distributions (SEDs) of 119,652 luminous broad-lined quasars with 0.064 < z < 5.46 using mid-IR data from Spitzer and WISE, near-infrared data from Two Micron All Sky Survey and UKIDSS, optical data from Sloan Digital Sky Survey, and UV data from Galaxy Evolution Explorer. The mean SED requires a bolometric correction (relative to 2500Å) of BC 2500Å = 2.75 ± 0.40 using the integrated light from 1 µm-2 keV, and we further explore the range of bolometric corrections exhibited by individual objects. In addition, we investigate the dependence of the mean SED on various parameters, particularly the UV luminosity for quasars with 0.5 z 3 and the properties of the UV emission lines for quasars with z 1.6; the latter is a possible indicator of the strength of the accretion disk wind, which is expected to be SED dependent. Luminosity-dependent mean SEDs show that, relative to the highluminosity SED, low-luminosity SEDs exhibit a harder (bluer) far-UV spectral slope (α UV ), a redder optical continuum, and less hot dust. Mean SEDs constructed instead as a function of UV emission line properties reveal changes that are consistent with known Principal Component Analysis (PCA) trends. A potentially important contribution to the bolometric correction is the unseen extream-UV (EUV) continuum. Our work suggests that lower-luminosity quasars and/or quasars with disk-dominated broad emission lines may require an extra continuum component in the EUV that is not present (or much weaker) in high-luminosity quasars with strong accretion disk winds. As such, we consider four possible models and explore the resulting bolometric corrections. Understanding these various SED-dependent effects will be important for accurate determination of quasar accretion rates.

We identify 885,503 type 1 quasar candidates to i 22  using the combination of optical and mid-IR photometry. Optical photometry is taken from the Sloan Digital Sky Survey-III: Baryon Oscillation Spectroscopic Survey (SDSS-III/BOSS), while mid-IR photometry comes from a combination of data from the Wide-field Infrared Survey Explorer (WISE) "AllWISE" data release and several large-area Spitzer Space Telescope fields. Selection is based on a Bayesian kernel density algorithm with a training sample of 157,701 spectroscopically confirmed type1 quasars with both optical and mid-IR data. Of the quasar candidates, 733,713 lack spectroscopic confirmation (and 305,623 are objects that we have not previously classified as photometric quasar candidates). These candidates include 7874 objects targeted as high-probability potential quasars with z 3.5 5 < < (of which 6779 are new photometric candidates). Our algorithm is more complete to z 3.5 > than the traditional mid-IR selection "wedges" and to z 2.2 3.5 < < quasars than the SDSS-III/BOSS project. Number counts and luminosity function analysis suggestthat the resulting catalog is relatively complete to known quasars and is identifying new high-z quasars at z 3 >. This catalog paves the way for luminosity-dependent clustering investigations of large numbers of faint, high-redshift quasars and for further machine-learning quasar selection using Spitzer and WISE data combined with other large-area optical imaging surveys.