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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,783 records · Page 99
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

ORBITAL AND PHYSICAL PROPERTIES OF THE σ Ori Aa, Ab, B TRIPLE SYSTEM

We provide a complete characterization of the astrophysical properties of the σ Ori Aa, Ab, B hierarchical triple system and an improved set of orbital parameters for the highly eccentric σ Ori Aa, Ab spectroscopic binary. We compiled a spectroscopic data set comprising 90 high-resolution spectra covering a total time span of 1963 days. We applied the Lehman-Filhés method for a detailed orbital analysis of the radial velocity curves and performed a combined quantitative spectroscopic analysis of the σ Ori Aa, Ab, B system by means of the stellar atmosphere code FASTWIND. We used our own plus other available information on photometry and distance to the system for measuring the radii, luminosities, and spectroscopic masses of the three components. We also inferred evolutionary masses and stellar ages using the Bayesian code BONNSAI. The orbital analysis of the new radial velocity curves led to a very accurate orbital solution of the σ Ori Aa, Ab pair. We provided indirect arguments indicating that σ Ori B is a fast-rotating early B dwarf. The FASTWIND+BONNSAI analysis showed that the Aa, Ab pair contains the hottest and most massive components of the triple system while σ Ori B is a bit cooler and less massive. The derived stellar ages of the inner pair are intriguingly younger than the one widely accepted for the σ Orionis cluster, at 3 ± 1 Ma. The outcome of this study will be of key importance for a precise determination of the distance to the σ Orionis cluster, the interpretation of the strong X-ray emission detected for σ Ori Aa, Ab, B, and the investigation of the formation and evolution of multiple massive stellar systems and substellar objects.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

THEORETICAL EMISSION SPECTRA OF ATMOSPHERES OF HOT ROCKY SUPER-EARTHS

Motivated by recent detection of transiting high-density super-Earths, we explore the detectability of hot rocky super-Earths orbiting very close to their host stars. In an environment hot enough for their rocky surfaces to be molten, they would have an atmosphere composed of gas species from the magma oceans. In this study, we investigate the radiative properties of the atmosphere that is in gas/melt equilibrium with the underlying magma ocean. Our equilibrium calculations yield Na, K, Fe, Si, SiO, O, and O{sub 2} as the major atmospheric species. We compile the radiative absorption line data of those species available in the literature and calculate their absorption opacities in the wavelength region of 0.1–100 μm. Using them, we integrate the thermal structure of the atmosphere. Then, we find that thermal inversion occurs in the atmosphere because of the UV absorption by SiO. In addition, we calculate the ratio of the planetary to stellar emission fluxes during secondary eclipse, and we find prominent emission features induced by SiO at 4 μm detectable by Spitzer, and those at 10 and 100 μm detectable by near-future space telescopes.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Suzaku X-ray observations of the Fermi Bubbles: Northernmost cap and southeast claw discovered with maxi-SSC

We report on Suzaku observations of large-scale X-ray structures possibly related to the Fermi Bubbles obtained in 2013 with a total duration of ≃80 ks. The observed regions were (1) the northern cap (N-cap; l ∼ 0°, 45°<b< 55°) seen in the mid-band (1.7–4.0 keV) map recently provided by Monitor of All-sky X-ray Image Solid-state Slit Camera (MAXI-SSC) and (2) the southeast claw (SE-claw; l ∼ 10°, −20{sup ∘}<b<−10{sup ∘}) seen in the ROSAT all-sky map and MAXI-SSC low-band (0.7–1.7 keV) map. In each region, we detected diffuse X-ray emission, which is represented by a three-component plasma model consisting of an unabsorbed thermal component (kT ≃ 0.1 keV) from the Local Hot Bubble, absorbed kT = 0.30 ± 0.05 keV emission representing the Galactic halo (GH), and a power-law component due to the isotropic cosmic X-ray background radiation. The emission measure of the GH component in the SE-claw shows an excess by a factor of ≃2.5 over the surrounding emission at 2° away. We also found a broad excess in the 1.7–4.0 keV count rates across the N-cap after compiling other archival data from Suzaku and Swift. The spectral stacking analysis of the N-cap data indicates the presence of another thermal component with kT = 0.70{sub −0.11}{sup +0.22}keV. The temperature kT ≃ 0.3 keV of the GH is higher than the ubiquitous value of kT ≃ 0.2 keV near the Fermi bubbles, and can be even higher (∼0.7 keV). We discuss our findings in the context of the bubble–halo interaction.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

THE DIFFERENCES IN THE TORUS GEOMETRY BETWEEN HIDDEN AND NON-HIDDEN BROAD LINE ACTIVE GALACTIC NUCLEI

We present results from the fitting of infrared (IR) spectral energy distributions of 21 active galactic nuclei (AGNs) with clumpy torus models. We compiled high spatial resolution (∼0.3–0.7 arcsec) mid-IR (MIR) N-band spectroscopy, Q-band imaging, and nuclear near- and MIR photometry from the literature. Combining these nuclear near- and MIR observations, far-IR photometry, and clumpy torus models enables us to put constraints on the torus properties and geometry. We divide the sample into three types according to the broad line region (BLR) properties: type-1s, type-2s with scattered or hidden broad line region (HBLR) previously observed, and type-2s without any published HBLR signature (NHBLR). Comparing the torus model parameters gives us the first quantitative torus geometrical view for each subgroup. We find that NHBLR AGNs have smaller torus opening angles and larger covering factors than HBLR AGNs. This suggests that the chance to observe scattered (polarized) flux from the BLR in NHBLR could be reduced by the dual effects of (a) less scattering medium due to the reduced scattering volume given the small torus opening angle and (b) the increased torus obscuration between the observer and the scattering region. These effects give a reasonable explanation for the lack of observed HBLR in some type-2 AGNs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

A search for population III galaxies in CLASH. I. Singly imaged candidates at high redshift

Population III (Pop III) galaxies are predicted to exist at high redshifts and may be rendered sufficiently bright for detection with current telescopes when gravitationally lensed by a foreground galaxy cluster. Pop III galaxies that exhibit strong Lyα emission should furthermore be identifiable from broadband photometry because of their unusual colors. Here, we report on a search for such objects at z≳6 in the imaging data from the Cluster Lensing And Supernova survey with Hubble (CLASH), covering 25 galaxy clusters in 16 filters. Our selection algorithm returns five singly imaged candidates with Lyα-like color signatures, for which ground-based spectroscopy with current 8–10 m class telescopes should be able to test the predicted strength of the Lyα line. None of these five objects have been included in previous CLASH compilations of high-redshift galaxy candidates. However, when large grids of spectral synthesis models are applied to the study of these objects, we find that only two of these candidates are significantly better fitted by Pop III models than by more mundane, low-metallicity stellar populations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

An ALMA survey of sub-millimeter galaxies in the extended Chandra deep field south: Physical properties derived from ultraviolet-to-radio modeling

The ALESS survey has followed up on a sample of 122 sub-millimeter sources in the Extended Chandra Deep Field South at 870 μm with the Atacama Large Millimeter Array (ALMA), allowing us to pinpoint the positions of sub-millimeter galaxies (SMGs) to ∼0.3 arcsec and to find their precise counterparts at different wavelengths. This enabled the first compilation of the multi-wavelength spectral energy distributions (SEDs) of a statistically reliable survey of SMGs. In this paper, we present a new calibration of the magphys SED modeling code that is optimized to fit these ultraviolet-to-radio SEDs of z>1 star-forming galaxies using an energy balance technique to connect the emission from stellar populations, dust attenuation, and dust emission in a physically consistent way. We derive statistically and physically robust estimates of the photometric redshifts and physical parameters (such as stellar masses, dust attenuation, star formation rates (SFRs), and dust masses) for the ALESS SMGs. We find that the ALESS SMGs have median stellar mass M{sub ∗}=8.9±0.1×10{sup 10} M{sub ⊙}, median SFR = 280±70 M{sub ⊙} yr{sup −1}, median overall V-band dust attenuation A{sub V}=1.9±0.2 mag, median dust mass M{sub dust}=(5.6±1.0)×10{sup 8} M{sub ⊙}, and median average dust temperature T{sub dust}≃40 K. We find that the average intrinsic SED of the ALESS SMGs resembles that of local ultra-luminous infrared galaxies in the infrared range, but the stellar emission of our average SMG is brighter and bluer, indicating lower dust attenuation, possibly because they are more extended. We explore how the average SEDs vary with different parameters (redshift, sub-millimeter flux, dust attenuation, and total infrared luminosity), and we provide a new set of SMG templates that can be used to interpret other SMG observations. To put the ALESS SMGs into context, we compare their stellar masses and SFRs with those of less actively star-forming galaxies at the same redshifts. We find that at z≃2, about half of the SMGs lie above the star-forming main sequence (with SFRs three times larger than normal galaxies of the same stellar mass), while half are consistent with being at the high-mass end of the main sequence. At higher redshifts (z≃3.5), the SMGs tend to have higher SFRs and stellar masses, but the fraction of SMGs that lie significantly above the main sequence decreases to less than a third.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

A COMPREHENSIVE CHARACTERIZATION OF THE 70 VIRGINIS PLANETARY SYSTEM

An on-going effort in the characterization of exoplanetary systems is the accurate determination of host star properties. This effort extends to the relatively bright host stars of planets discovered with the radial velocity method. The Transit Ephemeris Refinement and Monitoring Survey (TERMS) is aiding in these efforts as part of its observational campaign for exoplanet host stars. One of the first known systems is that of 70 Virginis, which harbors a jovian planet in an eccentric orbit. Here we present a complete characterization of this system with a compilation of TERMS photometry, spectroscopy, and interferometry. We provide fundamental properties of the host star through direct interferometric measurements of the radius (1.5% uncertainty) and through spectroscopic analysis. We combined 59 new Keck HIRES radial velocity measurements with the 169 previously published from the ELODIE, Hamilton, and HIRES spectrographs, to calculate a refined orbital solution and construct a transit ephemeris for the planet. These newly determined system characteristics are used to describe the Habitable Zone of the system with a discussion of possible additional planets and related stability simulations. Finally, we present 19 years of precision robotic photometry that constrain stellar activity and rule out central planetary transits for a Jupiter-radius planet at the 5σ level, with reduced significance down to an impact parameter of b = 0.95.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Exploring the properties of milliarcsecond radio sources

Cosmological applications of the “redshift—angular size” test require knowledge of the linear size of the “standard rod” used. In this paper, we study the properties of a large sample of 140 mas compact radio sources with flux densities measured at 6 and 20 cm, compiled by Gurvits et al. Using the best-fitted cosmological parameters given by Planck/WMAP9 observations, we investigate the characteristic length l{sub m}, as well as its dependence on the source luminosity L and redshift l{sub m} = lL{sup β} (1 + z){sup n}. For the full sample, measurements of the angular size θ provide a tight constraint on the linear size parameters. We find that cosmological evolution of the linear size is small (|n|≃10{sup −2}) and consistent with previous analysis. However, a substantial evolution of linear sizes with luminosity is still required (β ≃ 0.17). Furthermore, similar analysis done on sub-samples defined by different source optical counterparts and different redshift ranges seems to support the scheme of treating radio galaxies and quasars with distinct strategies. Finally, a cosmological-model-independent method is discussed to probe the properties of the angular size of milliarcsecond radio quasars. Using the corrected redshift—angular size relation for the quasar sample, we obtained a value of the matter density parameter, Ω{sub m}=0.292{sub −0.090}{sup +0.065}, in the spatially flat ΛCDM cosmology.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Improved estimates of the Milky Way’s stellar mass and star formation rate from hierarchical Bayesian meta-analysis

We present improved estimates of several global properties of the Milky Way, including its current star formation rate (SFR), the stellar mass contained in its disk and bulge+bar components, as well as its total stellar mass. We do so by combining previous measurements from the literature using a hierarchical Bayesian (HB) statistical method that allows us to account for the possibility that any value may be incorrect or have underestimated errors. We show that this method is robust to a wide variety of assumptions about the nature of problems in individual measurements or error estimates. Ultimately, our analysis yields an SFR for the Galaxy of M-dot {sub ⋆}=1.65±0.19 M{sub ⊙} yr{sup −1}, assuming a Kroupa initial mass function (IMF). By combining HB methods with Monte Carlo simulations that incorporate the latest estimates of the Galactocentric radius of the Sun, R{sub 0}, the exponential scale length of the disk, L{sub d}, and the local surface density of stellar mass, Σ{sub ⋆}(R{sub 0}), we show that the mass of the Galactic bulge+bar is M{sub ⋆}{sup B}=0.91±0.07×10{sup 10} M{sub ⊙}, the disk mass is M{sub ⋆}{sup D}=5.17±1.11×10{sup 10} M{sub ⊙}, and their combination yields a total stellar mass of M{sub ⋆}=6.08±1.14×10{sup 10} M{sub ⊙} (assuming a Kroupa IMF and an exponential disk profile). This analysis is based upon a new compilation of literature bulge mass estimates, normalized to common assumptions about the stellar IMF and Galactic disk properties, presented herein. We additionally find a bulge-to-total mass ratio for the Milky Way of B/T=0.150{sub −0.019}{sup +0.028} and a specific SFR of M-dot {sub ⋆}/M{sub ⋆}=2.71±0.59×10{sup −11} yr{sup −1}.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

FIRST DETECTION OF THERMAL RADIOJETS IN A SAMPLE OF PROTO-BROWN DWARF CANDIDATES

We observed with the Jansky Very Large Array at 3.6 and 1.3 cm a sample of 11 proto-brown dwarf (BD) candidates in Taurus in a search for thermal radio jets driven by the most embedded BDs. We detected for the first time four thermal radio jets in proto-BD candidates. We compiled data from UKIDSS, 2MASS, Spitzer, WISE, and Herschel to build the spectral energy distribution (SED) of the objects in our sample, which are similar to typical Class I SEDs of young stellar objects (YSOs). The four proto-BD candidates driving thermal radio jets also roughly follow the well-known trend of centimeter luminosity against bolometric luminosity determined for YSOs, assuming they belong to Taurus, although they present some excess of radio emission compared to the known relation for YSOs. Nonetheless, we are able to reproduce the flux densities of the radio jets modeling the centimeter emission of the thermal radio jets using the same type of models applied to YSOs, but with corresponding smaller stellar wind velocities and mass-loss rates, and exploring different possible geometries of the wind or outflow from the star. Moreover, we also find that the modeled mass outflow rates for the bolometric luminosities of our objects agree reasonably well with the trends found between the mass outflow rates and bolometric luminosities of YSOs, which indicates that, despite the “excess” centimeter emission, the intrinsic properties of proto-BDs are consistent with a continuation of those of very low-mass stars to a lower mass range. Overall, our study favors the formation of BDs as a scaled-down version of low-mass stars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Better alternatives to “astronomical silicate”: Laboratory-based optical functions of chondritic/solar abundance glass with application to HD 161796

“Astronomical” or “circumstellar” silicate optical functions (real and imaginary indices of refraction n(λ) and k(λ)) have previously been derived from compositionally and structurally disparate samples; past values were compiled from different sources in the literature, and are essentially kluges of observational, laboratory, and extrapolated or interpolated values. These synthetic optical functions were created because astronomers lack the quantitative data on amorphous silicates at all wavelengths needed for radiative transfer modeling. This paper provides optical functions that (1) are created with a consistent methodology, (2) use the same sample across all wavelengths, and (3) minimize interpolation and extrapolation wherever possible. We present electronic data tables of optical functions derived from mid-ultraviolet to far-infrared (FIR) laboratory transmission spectra for two materials: iron-free glass with chondritic/solar atmospheric abundances, and metallic iron. We compare these optical functions to other popular n, k data used to model amorphous silicates (e.g., “astronomical” or “circumstellar” silicate), both directly and in application to a simple system: the dust shell of the post-AGB star HD 161796. Using the new optical functions, we find that the FIR profile of model spectral energy distributions are significantly affected by the ratio of glass to iron. Our case study on HD 161796 shows that in modeling with our new optical functions, the mineralogy is markedly different from that derived using synthetic optical functions and suggests a new scenario of crystalline silicate formation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

PROBING THE ISOTROPY OF COSMIC ACCELERATION TRACED BY TYPE Ia SUPERNOVAE

We present a method to test the isotropy of the magnitude–redshift relation of Type Ia Supernovae (SNe Ia) and single out the most discrepant direction (in terms of the signal-to-noise ratio) with respect to the all-sky data. Our technique accounts for possible directional variations of the corrections for SNe Ia and yields all-sky maps of the best-fit cosmological parameters with arbitrary angular resolution. To show its potential, we apply our method to the high-redshift SNe Ia from the recent Union2.1 compilation, building maps with three different angular resolutions. We use a Monte Carlo method to estimate the statistical significance with which we could reject the null hypothesis that the magnitude–redshift relation is isotropic based on the properties of the observed most discrepant directions. We find that, based on pure signal-to-noise arguments, the null hypothesis cannot be rejected at any meaningful confidence level. However, if we also consider that the strongest deviations in the Union2.1 sample closely align with the dipole temperature anisotropy of the cosmic microwave background, we find that the null hypothesis should be rejected at the 95%–99% confidence level, slightly depending on the angular resolution of the study. If this result is not due to a statistical fluke, it might either indicate that the SN data have not been cleaned from all possible systematics or even point toward new physics. We finally discuss future perspectives in the field for achieving larger and more uniform data sets that will vastly improve the quality of the results and optimally exploit our method.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

COHESION OF AMORPHOUS SILICA SPHERES: TOWARD A BETTER UNDERSTANDING OF THE COAGULATION GROWTH OF SILICATE DUST AGGREGATES

Adhesion forces between submicrometer-sized silicate grains play a crucial role in the formation of silicate dust agglomerates, rocky planetesimals, and terrestrial planets. The surface energy of silicate dust particles is the key to their adhesion and rolling forces in a theoretical model based on contact mechanics. Here we revisit the cohesion of amorphous silica spheres by compiling available data on the surface energy for hydrophilic amorphous silica in various circumstances. It turned out that the surface energy for hydrophilic amorphous silica in a vacuum is a factor of 10 higher than previously assumed. Therefore, the previous theoretical models underestimated the critical velocity for the sticking of amorphous silica spheres, as well as the rolling friction forces between them. With the most plausible value of the surface energy for amorphous silica spheres, theoretical models based on the contact mechanics are in harmony with laboratory experiments. Consequently, we conclude that silicate grains with a radius of 0.1 μm could grow to planetesimals via coagulation in a protoplanetary disk. We argue that the coagulation growth of silicate grains in a molecular cloud is advanced either by organic mantles rather than icy mantles or, if there are no mantles, by nanometer-sized grain radius.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

ON THE ENHANCED CORONAL MASS EJECTION DETECTION RATE SINCE THE SOLAR CYCLE 23 POLAR FIELD REVERSAL

Compared to cycle 23, coronal mass ejections (CMEs) with angular widths >30° have been observed to occur at a higher rate during solar cycle 24, per sunspot number. This result is supported by data from three independent databases constructed using Large Angle and Spectrometric Coronagraph Experiment coronagraph images, two employing automated detection techniques and one compiled manually by human observers. According to the two databases that cover a larger field of view, the enhanced CME rate actually began shortly after the cycle 23 polar field reversal, in 2004, when the polar fields returned with a 40% reduction in strength and the interplanetary radial magnetic field became ≈30% weaker. This result is consistent with the link between anomalous CME expansion and the heliospheric total pressure decrease recently reported by Gopalswamy et al.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

A new sample of obscured AGNs selected from the XMM-Newton and AKARI surveys

We report a new sample of obscured active galactic nuclei (AGNs) selected from the XMM-Newton serendipitous source and AKARI point-source catalogs. We match X-ray sources with infrared (18 and 90 μm) sources located at |b|>10{sup ∘} to create a sample consisting of 173 objects. Their optical classifications and absorption column densities measured by X-ray spectra are compiled and study efficient selection criteria to find obscured AGNs. We apply the criteria (1) X-ray hardness ratio defined by using the 2–4.5 keV and 4.5–12 keV bands > −0.1 and (2) EPIC-PN count rate (CR) in the 0.2–12 keV to infrared flux ratio CR/F{sub 90}<0.1 or CR/F{sub 18}<1, where F{sub 18} and F{sub 90} are infrared fluxes at 18 and 90 μm in Jy, respectively, to search for obscured AGNs. X-ray spectra of 48 candidates, for which no X-ray results have been published, are analyzed and X-ray evidence for the presence of obscured AGNs such as a convex shape X-ray spectrum indicative of absorption of N{sub H} ∼ 10{sup 22–24} cm{sup −2}, a very flat continuum, or a strong Fe–K emission line with an equivalent width of >700 eV is found in 26 objects. Six of them are classified as Compton-thick AGNs, and four are represented by either Compton-thin or Compton-thick spectral models. The success rate of finding obscured AGNs combining our analysis and the literature is 92% if the 18 μm condition is used. Of the 26 objects, 4 are optically classified as an H ii nucleus and are new “elusive AGNs” in which star formation activity likely overwhelms AGN emission in the optical and infrared bands.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

[O iii] λ5007 and X-ray properties of a complete sample of hard X-RAY selected AGNs in the local universe

We study the correlation between the [O iii] λ5007 and X-ray luminosities of local active galactic nuclei (AGNs), using a complete, hard X-ray (>10 keV) selected sample in the Swift/BAT 9-month catalog. From our optical spectroscopic observations at the South African Astronomical Observatory and the literature, a catalog of [O iii] λ5007 line flux for all 103 AGNs at Galactic latitudes of |b|>15{sup ∘} is compiled. Significant correlations with intrinsic X-ray luminosity (L{sub X}) are found for both observed (L{sub [O III] }) and extinction-corrected (L{sub [O III]}{sup cor}) luminosities, separately for X-ray unabsorbed and absorbed AGNs. We obtain the regression form of L{sub [O III] }∝ L{sub 2−10 keV}{sup 1.18±0.07} and L{sub [O III]}{sup cor} ∝ L{sub 2−10 keV}{sup 1.16±0.09} from the whole sample. The absorbed AGNs with low (<0.5%) scattering fractions in soft X-rays show on average smaller L{sub [O III]}/L{sub X} and L{sub [O III]}{sup cor}/L{sub X} ratios than the other absorbed AGNs, while those in edge-on host galaxies do not. These results suggest that a significant fraction of this population is buried in tori with small opening angles. By using these L{sub [O III] }versus L{sub X} correlations, the X-ray luminosity function (LF) of local AGNs (including Compton-thick AGNs) in a standard population synthesis model gives much better agreement with the [O iii] λ5007 LF derived from the Sloan Digital Sky Survey than previously reported. This confirms that hard X-ray observations are a very powerful tool to find AGNs with high completeness.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

THE 2014 KIDA NETWORK FOR INTERSTELLAR CHEMISTRY

Chemical models used to study the chemical composition of the gas and the ices in the interstellar medium are based on a network of chemical reactions and associated rate coefficients. These reactions and rate coefficients are partially compiled from data in the literature, when available. We present in this paper kida.uva.2014, a new updated version of the kida.uva public gas-phase network first released in 2012. In addition to a description of the many specific updates, we illustrate changes in the predicted abundances of molecules for cold dense cloud conditions as compared with the results of the previous version of our network, kida.uva.2011.

astrochemistry↗
DOE OSTI2015

YOUNG STELLAR OBJECTS IN THE GOULD BELT

We present the full catalog of Young Stellar Objects (YSOs) identified in the 18 molecular clouds surveyed by the Spitzer Space Telescope “cores to disks” (c2d) and “Gould Belt” (GB) Legacy surveys. Using standard techniques developed by the c2d project, we identify 3239 candidate YSOs in the 18 clouds, 2966 of which survive visual inspection and form our final catalog of YSOs in the GB. We compile extinction corrected spectral energy distributions for all 2966 YSOs and calculate and tabulate the infrared spectral index, bolometric luminosity, and bolometric temperature for each object. We find that 326 (11%), 210 (7%), 1248 (42%), and 1182 (40%) are classified as Class 0 + I, Flat-spectrum, Class II, and Class III, respectively, and show that the Class III sample suffers from an overall contamination rate by background Asymptotic Giant Branch stars between 25% and 90%. Adopting standard assumptions, we derive durations of 0.40–0.78 Myr for Class 0 + I YSOs and 0.26–0.50 Myr for Flat-spectrum YSOs, where the ranges encompass uncertainties in the adopted assumptions. Including information from (sub)millimeter wavelengths, one-third of the Class 0 + I sample is classified as Class 0, leading to durations of 0.13–0.26 Myr (Class 0) and 0.27–0.52 Myr (Class I). We revisit infrared color–color diagrams used in the literature to classify YSOs and propose minor revisions to classification boundaries in these diagrams. Finally, we show that the bolometric temperature is a poor discriminator between Class II and Class III YSOs.

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