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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 253 records · Page 14
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DOE OSTI2015

THE EVOLUTION OF THE FAR-UV LUMINOSITY FUNCTION AND STAR FORMATION RATE DENSITY OF THE CHANDRA DEEP FIELD SOUTH FROM z = 0.2 TO 1.2 WITH SWIFT/UVOT

We use deep Swift UV/Optical Telescope (UVOT) near-ultraviolet (1600–4000 Å) imaging of the Chandra Deep Field South to measure the rest-frame far-UV (FUV; 1500 Å) luminosity function (LF) in four redshift bins between z = 0.2 and 1.2. Our sample includes 730 galaxies with u < 24.1 mag. We use two methods to construct and fit the LFs: the traditional V{sub max} method with bootstrap errors, and a maximum likelihood estimator. We observe luminosity evolution such that M* fades by ∼2 mag from z ∼ 1 to z ∼ 0.3, implying that star formation activity was substantially higher at z ∼ 1 than today. We integrate our LFs to determine the FUV luminosity densities and star formation rate densities (SFRDs) from z = 0.2 to 1.2. We find evolution consistent with an increase proportional to (1 + z){sup 1.9} out to z ∼ 1. Our luminosity densities and star formation rates are consistent with those found in the literature but are, on average, a factor of ∼2 higher than previous FUV measurements. In addition, we combine our UVOT data with the MUSYC survey to model the galaxies’ ultraviolet-to-infrared spectral energy distributions and estimate the rest-frame FUV attenuation. We find that accounting for the attenuation increases the SFRDs by ∼1 dex across all four redshift bins.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Reionization after Planck: The derived growth of the cosmic ionizing emissivity now matches the growth of the galaxy UV luminosity density

Thomson optical depth τ measurements from Planck provide new insights into the reionization of the universe. In pursuit of model-independent constraints on the properties of the ionizing sources, we determine the empirical evolution of the cosmic ionizing emissivity. We use a simple two-parameter model to map out the evolution in the emissivity at z ≳ 6 from the new Planck optical depth τ measurements, from the constraints provided by quasar absorption spectra and from the prevalence of Lyα emission in z ∼ 7–8 galaxies. We find the redshift evolution in the emissivity N-dot {sub ion}(z) required by the observations to be (dlog{sub 10} N-dot {sub ion}/dz){sub z=8}=−0.15{sub −0.11}{sup +0.08} ((dlog{sub 10} N-dot {sub ion}/dz){sub z=8}=−0.19{sub −0.11}{sup +0.09} for a flat prior), largely independent of the assumed clumping factor C{sub H ii} and entirely independent of the nature of the ionizing sources. The trend in N-dot {sub ion}(z) is well-matched by the evolution of the galaxy UV-luminosity density (dlog{sub 10}ρ{sub UV}/dz=−0.11±0.04) to a magnitude limit ≳−13 mag, suggesting that galaxies are the sources that drive the reionization of the universe. The role of galaxies is further strengthened by the conversion from the UV luminosity density ρ{sub UV} to N-dot {sub ion}(z) being possible for physically plausible values of the escape fraction f{sub esc}, the Lyman-continuum photon production efficiency ξ{sub ion}, and faint-end cut-off M{sub lim} to the luminosity function. Quasars/active galactic nuclei appear to match neither the redshift evolution nor normalization of the ionizing emissivity. Based on the inferred evolution in the ionizing emissivity, we estimate that the z ∼ 10 UV-Iuminosity density is 8{sub −4}{sup +15}× lower than at z ∼ 6, consistent with the observations. The present approach of contrasting the inferred evolution of the ionizing emissivity with that of the galaxy UV luminosity density adds to the growing observational evidence that faint, star-forming galaxies drive the reionization of the universe.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Predicting the redshift 2 Hα luminosity function using [O iii] emission line galaxies

Upcoming space-based surveys such as Euclid and WFIRST-AFTA plan to measure baryonic acoustic oscillations in order to study dark energy. These surveys will use IR slitless grism spectroscopy to measure redshifts of a large number of galaxies over a significant redshift range. In this paper, we use the Wide Field Camera 3 Infrared Spectroscopic Parallel Survey (WISP) to estimate the expected number of Hα emitters observable by these future surveys. WISP is an ongoing Hubble Space Telescope slitless spectroscopic survey, covering the 0.8–1.65 μm wavelength range and allowing the detection of Hα emitters up to z ∼ 1.5 and [O iii] emitters to z ∼ 2.3. We derive the Hα–[O iii] bivariate line luminosity function (LLF) for WISP galaxies at z ∼ 1 using a maximum likelihood estimator that properly accounts for uncertainties in line luminosity measurements and we demonstrate how it can be used to derive the Hα luminosity function by exclusively fitting [O iii] data. Using the z∼2 [O iii] LLF and assuming that the relation between Hα and [O iii] luminosity does not change significantly over the redshift range, we predict the Hα number counts at z∼2—the upper end of the redshift range of interest for future surveys. For the redshift range 0.7<z<2, we expect ∼3000 galaxies deg{sup −2} for a flux limit of 3 × 10{sup −16} erg s{sup −1} cm{sup −2} (the proposed depth of the Euclid galaxy redshift survey) and ∼20,000 galaxies deg{sup −2} for a flux limit of ∼10{sup −16} erg s{sup −1} cm{sup −2} (the baseline depth of the WFIRST galaxy redshift survey).

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Magellan adaptive optics first-light observations of the exoplanet β PIC b. II. 3–5 μm direct imaging with MagAO+Clio, and the empirical bolometric luminosity of a self-luminous giant planet

Young giant exoplanets are a unique laboratory for understanding cool, low-gravity atmospheres. A quintessential example is the massive extrasolar planet β Pic b, which is 9 AU from and embedded in the debris disk of the young nearby A6V star β Pictoris. We observed the system with first light of the Magellan Adaptive Optics (MagAO) system. In Paper I we presented the first CCD detection of this planet with MagAO+VisAO. Here we present four MagAO+Clio images of β Pic b at 3.1 μm, 3.3 μm, L′, and M{sup ′}, including the first observation in the fundamental CH{sub 4} band. To remove systematic errors from the spectral energy distribution (SED), we re-calibrate the literature photometry and combine it with our own data, for a total of 22 independent measurements at 16 passbands from 0.99 to 4.8 μm. Atmosphere models demonstrate the planet is cloudy but are degenerate in effective temperature and radius. The measured SED now covers >80% of the planet’s energy, so we approach the bolometric luminosity empirically. We calculate the luminosity by extending the measured SED with a blackbody and integrating to find log(L{sub bol}/L{sub ⊙}) = −3.78±0.03. From our bolometric luminosity and an age of 23 ± 3 Myr, hot-start evolutionary tracks give a mass of 12.7 ± 0.3 M{sub Jup}, radius of 1.45 ± 0.02 R{sub Jup}, and T{sub eff} of 1708 ± 23 K (model-dependent errors not included). Our empirically determined luminosity is in agreement with values from atmospheric models (typically −3.8 dex), but brighter than values from the field-dwarf bolometric correction (typically −3.9 dex), illustrating the limitations in comparing young exoplanets to old brown dwarfs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Unified treatment of the luminosity distance in cosmology

Comparing the luminosity distance measurements to its theoretical predictions is one of the cornerstones in establishing the modern cosmology. However, as shown in Biern and Yoo, its theoretical predictions in literature are often plagued with infrared divergences and gauge-dependences. This trend calls into question the sanity of the methods used to derive the luminosity distance. Here we critically investigate four different methods—the geometric approach, the Sachs approach, the Jacobi mapping approach, and the geodesic light cone (GLC) approach to modeling the luminosity distance, and we present a unified treatment of such methods, facilitating the comparison among the methods and checking their sanity. All of these four methods, if exercised properly, can be used to reproduce the correct description of the luminosity distance.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Gauge-invariance and infrared divergences in the luminosity distance

Measurements of the luminosity distance have played a key role in discovering the late-time cosmic acceleration. However, when accounting for inhomogeneities in the Universe, its interpretation has been plagued with infrared divergences in its theoretical predictions, which are in some cases used to explain the cosmic acceleration without dark energy. The infrared divergences in most calculations are artificially removed by imposing an infrared cut-off scale. We show that a gauge-invariant calculation of the luminosity distance is devoid of such divergences and consistent with the equivalence principle, eliminating the need to impose a cut-off scale. We present proper numerical calculations of the luminosity distance using the gauge-invariant expression and demonstrate that the numerical results with an ad hoc cut-off scale in previous calculations have negligible systematic errors as long as the cut-off scale is larger than the horizon scale. We discuss the origin of infrared divergences and their cancellation in the luminosity distance.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Consistency between the luminosity function of resolved millisecond pulsars and the galactic center excess

Fermi Large Area Telescope data reveal an excess of GeV gamma rays from the direction of the Galactic Center and bulge. Several explanations have been proposed for this excess including an unresolved population of millisecond pulsars (MSPs) and self-annihilating dark matter. It has been claimed that a key discriminant for or against the MSP explanation can be extracted from the properties of the luminosity function describing this source population. Specifically, is the luminosity function of the putative MSPs in the Galactic Center consistent with that characterizing the resolved MSPs in the Galactic disk? To investigate this we have used a Bayesian Markov Chain Monte Carlo to evaluate the posterior distribution of the parameters of the MSP luminosity function describing both resolved MSPs and the Galactic Center excess. At variance with some other claims, our analysis reveals that, within current uncertainties, both data sets can be well fit with the same luminosity function.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

DETERMINING THE LUMINOSITY FUNCTION OF SWIFT LONG GAMMA-RAY BURSTS WITH PSEUDO-REDSHIFTS

The determination of the luminosity function (LF) of gamma-ray bursts (GRBs) is an important role for the cosmological applications of the GRBs, which, however, is seriously hindered by some selection effects due to redshift measurements. In order to avoid these selection effects, we suggest calculating pseudo-redshifts for Swift GRBs according to the empirical L-E{sub p} relationship. Here, such a L-E{sub p} relationship is determined by reconciling the distributions of pseudo- and real redshifts of redshift-known GRBs. The values of E{sub p} taken from Butler's GRB catalog are estimated with Bayesian statistics rather than observed. Using the GRB sample with pseudo-redshifts of a relatively large number, we fit the redshift-resolved luminosity distributions of the GRBs with a broken-power-law LF. The fitting results suggest that the LF could evolve with redshift by a redshift-dependent break luminosity, e.g., L{sub b} = 1.2 Multiplication-Sign 10{sup 51}(1 + z){sup 2} erg s{sup -1}. The low- and high-luminosity indices are constrained to 0.8 and 2.0, respectively. It is found that the proportional coefficient between the GRB event rate and the star formation rate should correspondingly decrease with increasing redshifts.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

RELATIONSHIP BETWEEN THE KINETIC POWER AND BOLOMETRIC LUMINOSITY OF JETS: LIMITATION FROM BLACK HOLE X-RAY BINARIES, ACTIVE GALACTIC NUCLEI, AND GAMMA-RAY BURSTS

The correlation between the kinetic power P {sub jet} and intrinsic bolometric luminosity L {sub jet} of jets may reveal the underlying jet physics in various black hole systems. Based on the recent work by Nemmen et al., we re-investigate this correlation with additional sources of black hole X-ray binaries (BXBs) in hard/quiescent states and low-luminosity active galactic nuclei (LLAGNs). The new sample includes 29 sets of data from 7 BXBs and 20 LLAGNs, with P {sub jet} and L {sub jet} being derived from spectral modeling of the quasi-simultaneous multi-band spectra under the accretion jet scenario. Compared to previous works, the range of luminosity is now enlarged to more than 20 decades, i.e., from ∼10{sup 31} erg s{sup –1} to ∼10{sup 52} erg s{sup –1}, which allows for better constraining of the correlation. One notable result is that the jets in BXBs and LLAGNs almost follow the same P {sub jet}-L {sub jet} correlation that was obtained from blazars and gamma-ray bursts. The slope indices we derived are 1.03 ± 0.01 for the whole sample, 0.85 ± 0.06 for the BXB subsample, 0.71 ± 0.11 for the LLAGN subsample, and 1.01 ± 0.05 for the LLAGN-blazar subsample, respectively. The correlation index around unit implies the independence of jet efficiency on the luminosity or kinetic power. Our results may further support the hypothesis that similar physical processes exist in the jets of various black hole systems.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

CONSTRAINING PHYSICAL PROPERTIES OF TYPE IIn SUPERNOVAE THROUGH RISE TIMES AND PEAK LUMINOSITIES

We investigate the diversity in the wind density, supernova ejecta energy, and ejecta mass in Type IIn supernovae based on their rise times and peak luminosities. We show that the wind density and supernova ejecta properties can be estimated independently if both the rise time and peak luminosity are observed. The peak luminosity is mostly determined by the supernova properties and the rise time can be used to estimate the wind density. We find that the ejecta energies of Type IIn supernovae need to vary by factors of 0.2-5 from the average if their ejecta masses are similar. The diversity in the observed rise times indicates that their wind densities vary by factors of 0.2-2 from the average. We show that Type IIn superluminous supernovae should have not only large wind density but also large ejecta energy and/or small ejecta mass to explain their large luminosities and the rise times at the same time. We also note that shock breakout does not necessarily occur in the wind even if it is optically thick, except for the case of superluminous supernovae, and we analyze the observational data both with and without assuming that the shock breakout occurs in the dense wind of Type IIn supernovae.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

RHIC Proton Luminosity and Polarization Improvement

The RHIC proton beam polarization can be improved by raising the Booster scraping, which also helps to reduce the RHIC transverse emittance, and therefore to improve the luminosity. By doing this, the beam-beam effect would be enhanced. Currently, the RHIC working point is constrained between 2/3 and 7/10, the 2/3 resonance would affect intensity and luminosity lifetime, and the working point close to 7/10 would enhance polarization decay in store. Run 2013 shows that average polarization decay is merely 1.8% in 8 hours, and most fills have the luminosity lifetime better than 14 hours, which is not a problem. Therefore, even without beam-beam correction, there is room to improve for RHIC polarization and luminosity. The key to push the Booster scraping is to raise the Booster input intensity; for that, two approaches can be used. The first is to extend the LINAC tank 9 pulse width, which has been successfully applied in run 2006. The second is to raise the source temperature, which has been successfully applied in run 2006 and run 2012.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

NuSTAR unveils a heavily obscured low-luminosity active galactic nucleus in the luminous infrared galaxy NGC 6286

We report the detection of a heavily obscured active galactic nucleus (AGN) in the luminous infrared galaxy (LIRG) NGC 6286 identified in a 17.5 ks Nuclear Spectroscopic Telescope Array observation. The source is in an early merging stage and was targeted as part of our ongoing NuSTAR campaign observing local luminous and ultra-luminous infrared galaxies in different merger stages. NGC 6286 is clearly detected above 10 keV and by including the quasi-simultaneous Swift/XRT and archival XMM-Newton and Chandra data, we find that the source is heavily obscured (N{sub H} ≃(0.95−1.32) × 10{sup 24} cm{sup −2}) with a column density consistent with being Compton-thick (CT, log(N{sub H}/cm{sup −2})⩾24). The AGN in NGC 6286 has a low absorption-corrected luminosity (L{sub 2−10 keV} ∼ 3−20 × 10{sup 41} erg s{sup −1}) and contributes ≲1% to the energetics of the system. Because of its low luminosity, previous observations carried out in the soft X-ray band (<10 keV) and in the infrared did not notice the presence of a buried AGN. NGC 6286 has multiwavelength characteristics typical of objects with the same infrared luminosity and in the same merger stage, which might imply that there is a significant population of obscured low-luminosity AGNs in LIRGs that can only be detected by sensitive hard X-ray observations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

FORMATION AND RECONDENSATION OF COMPLEX ORGANIC MOLECULES DURING PROTOSTELLAR LUMINOSITY OUTBURSTS

During the formation of stars, the accretion of surrounding material toward the central object is thought to undergo strong luminosity outbursts followed by long periods of relative quiescence, even at the early stages of star formation when the protostar is still embedded in a large envelope. We investigated the gas-phase formation and recondensation of the complex organic molecules (COMs) di-methyl ether and methyl formate, induced by sudden ice evaporation processes occurring during luminosity outbursts of different amplitudes in protostellar envelopes. For this purpose, we updated a gas-phase chemical network forming COMs in which ammonia plays a key role. The model calculations presented here demonstrate that ion–molecule reactions alone could account for the observed presence of di-methyl ether and methyl formate in a large fraction of protostellar cores without recourse to grain-surface chemistry, although they depend on uncertain ice abundances and gas-phase reaction branching ratios. In spite of the short outburst timescales of about 100 years, abundance ratios of the considered species higher than 10% with respect to methanol are predicted during outbursts due to their low binding energies relative to water and methanol which delay their recondensation during cooling. Although the current luminosity of most embedded protostars would be too low to produce complex organics in the hot-core regions that are observable with current sub-millimetric interferometers, previous luminosity outburst events would induce the formation of COMs in extended regions of protostellar envelopes with sizes increasing by up to one order of magnitude.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

H α AS A LUMINOSITY CLASS DIAGNOSTIC FOR K- AND M-TYPE STARS

We have identified the H α absorption feature as a new spectroscopic diagnostic of luminosity class in K- and M-type stars. From high-resolution spectra of 19 stars with well-determined physical properties (including effective temperatures and stellar radii), we measured equivalent widths for H α and the Ca ii triplet and examined their dependence on both luminosity class and stellar radius. H α shows a strong relation with both luminosity class and radius that extends down to late M spectral types. This behavior in H α has been predicted as a result of the density-dependent overpopulation of the metastable 2s level in hydrogen, an effect that should become dominant for Balmer line formation in non-LTE conditions. We conclude that this new metallicity-insensitive diagnostic of luminosity class in cool stars could serve as an effective means of discerning between populations such as Milky Way giants and supergiant members of background galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Evolutions and Calibrations of Long Gamma-Ray-burst Luminosity Correlations Revisited

Luminosity correlations of long gamma-ray bursts (GRBs) are extensively proposed as an effective complementarity to trace the Hubble diagram of the universe at high redshifts, which is of great importance to explore properties of dark energy. Recently, several empirical luminosity correlations have been statistically proposed from GRB observations. However, to treat a GRB as the distance indicator, there are two key issues: the redshift evolution of luminosity correlations and their calibrations. In this paper, we choose the Amati relation, the correlation between the peak spectra energy and the equivalent isotropic energy of GRBs (E{sub p}--E{sub iso}) as an example and find that the current GRB data set implies that there could be a evolution of the luminosity correlation with respect to the redshift. Therefore, we propose an extended Amati relation with two extra redshift-dependent terms to correct the redshift evolution of the GRB relation. Second, we carefully check the reliability of the calibration method using the low-redshift GRB data. Importantly, we find that the low-redshift calibration method does not take whole correlations between Ω{sub m} and coefficients into account. Neglecting this correlation information can break the degeneracies and obtain the biased constraint on Ω{sub m}, which is very sensitive to values of parameters for the calibration. A small shift in the parameters of the “calibrated” relation could significantly change the final constraint on Ω{sub m} in the low-redshift calibration method. Finally, we simulate several GRB samples with different statistical errors and find that, in order to correctly recover the fiducial value of Ω{sub m}, using the low-redshift calibration method, we need a large number of GRB samples with high precisions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

The MOSDEF Survey: Metallicity Dependence of PAH Emission at High Redshift and Implications for 24 μm Inferred IR Luminosities and Star Formation Rates at z ∼ 2

We present results on the variation of 7.7 μm polycyclic aromatic hydrocarbon (PAH) emission in galaxies spanning a wide range in metallicity at z ∼ 2. For this analysis, we use rest-frame optical spectra of 476 galaxies at 1.37 ≤ z ≤ 2.61 from the MOSFIRE Deep Evolution Field (MOSDEF) survey to infer metallicities and ionization states. Spitzer/MIPS 24 μm and Herschel/PACS 100 and 160 μm observations are used to derive rest-frame 7.7 μm luminosities (L{sub 7.7}) and total IR luminosities (L{sub IR}), respectively. We find significant trends between the ratio of L{sub 7.7} to L{sub IR} (and to dust-corrected star formation rate [SFR]) and both metallicity and [O iii]/[O ii] (O{sub 32}) emission line ratio. The latter is an empirical proxy for the ionization parameter. These trends indicate a paucity of PAH emission in low-metallicity environments with harder and more intense radiation fields. Additionally, L{sub 7.7}/L{sub IR} is significantly lower in the youngest quartile of our sample (ages of ≲500 Myr) compared to older galaxies, which may be a result of the delayed production of PAHs by AGB stars. The relative strength of L{sub 7.7} to L{sub IR} is also lower by a factor of ∼2 for galaxies with masses M{sub ∗}<10{sup 10} M{sub ⊙}, compared to the more massive ones. We demonstrate that commonly used conversions of L{sub 7.7} (or 24 μm flux density, f {sub 24}) to L{sub IR} underestimate the IR luminosity by more than a factor of 2 at M{sub ∗}∼10{sup 9.6--10.0} M{sub ⊙}. We adopt a mass-dependent conversion of L{sub 7.7} to L{sub IR} with L{sub 7.7}/L{sub IR} = 0.09 and 0.22 for M{sub ∗}⩽10{sup 10} and >10{sup 10} M{sub ⊙}, respectively. Based on the new scaling, the SFR–M {sub *} relation has a shallower slope than previously derived. Our results also suggest a higher IR luminosity density at z ∼ 2 than previously measured, corresponding to a ∼30% increase in the SFR density.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

The Rest-frame Optical (900 nm) Galaxy Luminosity Function at z ∼ 4–7: Abundance Matching Points to Limited Evolution in the M{sub STAR}/M{sub HALO} Ratio at z ≥ 4

We present the first determination of the galaxy luminosity function (LF) at z ∼ 4, 5, 6, and 7, in the rest-frame optical at λ{sub rest}∼900 nm (z′ band). The rest-frame optical light traces the content in low-mass evolved stars (∼stellar mass—M {sub *}), minimizing potential measurement biases for M {sub *}. Moreover, it is less affected by nebular line emission contamination and dust attenuation, is independent of stellar population models, and can be probed up to z ∼ 8 through Spitzer/IRAC. Our analysis leverages the unique full-depth Spitzer/IRAC 3.6–8.0 μm data over the CANDELS/GOODS-N, CANDELS/GOODS-S, and COSMOS/UltraVISTA fields. We find that, at absolute magnitudes where M{sub z{sup ′}} is fainter than ≳−23 mag, M{sub z{sup ′}} linearly correlates with M{sub UV,1600}. At brighter M{sub z{sup ′}}, M{sub UV,1600} presents a turnover, suggesting that the stellar mass-to-light ratio M{sub ∗}/L{sub UV,1600} could be characterized by a very broad range of values at high stellar masses. Median-stacking analyses recover an M{sub ∗}/L{sub z{sup ′}} roughly independent on M{sub z{sup ′}} for M{sub z{sup ′}}≳−23 mag, but exponentially increasing at brighter magnitudes. We find that the evolution of the LF marginally prefers a pure luminosity evolution over a pure density evolution, with the characteristic luminosity decreasing by a factor of ∼5× between z ∼ 4 and z ∼ 7. Direct application of the recovered M{sub ∗}/L{sub z{sup ′}} generates stellar mass functions consistent with average measurements from the literature. Measurements of the stellar-to-halo mass ratio at fixed cumulative number density show that it is roughly constant with redshift for M{sub h}≳10{sup 12}M{sub ⊙}. This is also supported by the fact that the evolution of the LF at 4≲z≲7 can be accounted for by a rigid displacement in luminosity, corresponding to the evolution of the halo mass from abundance matching.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Radio Luminosity Function of Flat-spectrum Radio Quasars

We present the radio luminosity function (LF) of flat-spectrum radio quasars (FSRQ), using the the largest and most complete sample to date. Cross-matching between the FIRST 20 cm and GB6 6 cm radio surveys, we find 638 flat-spectrum radio sources above 220 mJy at 1.4 GHz; of these, 327 are are classified and verified using optical spectroscopy data, mainly from Sloan Digital Sky Survey Data Release 12. We also considered flat-spectrum radio sources that lack both literature references and optical spectroscopy, and we identified 12 out of the 43 such sources to potentially be FSRQs, using their WISE colors. From the fully identified sample of 242 FSRQs, we derived the radio LF and cosmic evolution of blazars at 1.4 GHz, finding good agreement with previous work at 5 GHz. The number density of FSRQs increases dramatically to a redshift of z ∼ 2 and then declines for higher redshifts. Furthermore, the redshift at which the quasar density peaks is clearly dependent on luminosity, with more luminous sources peaking at higher redshifts. The approximate best-fit LF for a luminosity-dependent evolutionary model is a broken power-law with slopes ∼0.7 and ∼1.7 below and above the break luminosity, logL{sub 1.4}∼43.8 erg s{sup −1}, respectively.

79 ASTRONOMY AND ASTROPHYSICS↗