Showing papers by "Edward L. Wright published in 2018"
University of Connecticut1, California Institute of Technology2, University of Michigan3, Jet Propulsion Laboratory4, Space Telescope Science Institute5, Johns Hopkins University6, University of Massachusetts Amherst7, University of California, Irvine8, Goddard Space Flight Center9, University of British Columbia10, University of Maryland, College Park11, Ames Research Center12, University of California, Santa Cruz13, Cornell University14, Harvard University15, University of Florida16, University of California, San Diego17, University of Arizona18, University of Illinois at Urbana–Champaign19, University of California, Los Angeles20, NASA Headquarters21, University of Paris22, Netherlands Institute for Space Research23, University of Tokyo24
TL;DR: The Origins Space Telescope, one of four large mission concept studies sponsored by NASA for review in the 2020 US Astrophysics Decadal Survey, will open unprecedented discovery space in the infrared, unveiling our cosmic origins.
Abstract: The Origins Space Telescope, one of four large Mission Concept Studies sponsored by NASA for review in the 2020 US Astrophysics Decadal Survey, will open unprecedented discovery space in the infrared, unveiling our cosmic origins.
69 citations
California Institute of Technology1, University of California, Santa Cruz2, University of California, Los Angeles3, University of California, Riverside4, American Museum of Natural History5, University of Toledo6, Arizona State University7, University of Texas at Austin8, University of New South Wales9
TL;DR: In this article, the authors present preliminary trigonometric parallaxes of 184 late-T and Y dwarfs using observations from Spitzer (143), USNO (18), NTT (14), and UKIRT (9).
Abstract: We present preliminary trigonometric parallaxes of 184 late-T and Y dwarfs using observations from Spitzer (143), USNO (18), NTT (14), and UKIRT (9). To complete the 20-pc census of $\ge$T6 dwarfs, we combine these measurements with previously published trigonometric parallaxes for an additional 44 objects and spectrophotometric distance estimates for another 7. For these 235 objects, we estimate temperatures, sift into five 150K-wide $T_{\rm eff}$ bins covering the range 300-1050K, determine the completeness limit for each, and compute space densities. To anchor the high-mass end of the brown dwarf mass spectrum, we compile a list of early- to mid-L dwarfs within 20 pc. We run simulations using various functional forms of the mass function passed through two different sets of evolutionary code to compute predicted distributions in $T_{\rm eff}$. The best fit of these predictions to our L, T, and Y observations is a simple power-law model with $\alpha \approx 0.6$ (where $dN/dM \propto M^{-\alpha}$), meaning that the slope of the field substellar mass function is in rough agreement with that found for brown dwarfs in nearby star forming regions and young clusters. Furthermore, we find that published versions of the log-normal form do not predict the steady rise seen in the space densities from 1050K to 350K. We also find that the low-mass cutoff to formation, if one exists, is lower than $\sim$5 $M_{Jup}$, which corroborates findings in young, nearby moving groups and implies that extremely low-mass objects have been forming over the lifetime of the Milky Way.
64 citations
TL;DR: In this article, the authors presented the Massive and Distant Clusters of WISE Survey (MaDCoWS) data set, which consists of the 2433 highest amplitude detections in the WISE-Pan-STARRS region and the 250 highest amplitude detection in WISE--SuperCOSMOS region.
Abstract: We present the Massive and Distant Clusters of WISE Survey (MaDCoWS), a search for galaxy clusters at 0.7 -30 degrees) and the remainder of the southern extragalactic sky at Dec<-30 degrees for which shallower optical data from SuperCOSMOS Sky Survey are available. In this paper we describe the search algorithm, characterize the sample, and present the first MaDCoWS data release -- catalogs of the 2433 highest amplitude detections in the WISE--Pan-STARRS region and the 250 highest amplitude detections in the WISE--SuperCOSMOS region. A total of 1723 of the detections from the WISE--Pan-STARRS sample have also been observed with the Spitzer Space Telescope, providing photometric redshifts and richnesses, and an additional 64 detections within the WISE--SuperCOSMOS region also have photometric redshifts and richnesses. Spectroscopic redshifts for 38 MaDCoWS clusters with IRAC photometry demonstrate that the photometric redshifts have an uncertainty of $\sigma_z/(1+z)\sim0.036$. Combining the richness measurements with Sunyaev-Zel'dovich observations of MaDCoWS clusters, we also present a preliminary mass-richness relation that can be used to infer the approximate mass distribution of the full sample. The estimated median mass for the WISE--Pan-STARRS catalog is $M_{500}=1.6^{+0.7}_{-0.8}\times10^{14} \mathrm{M}_\odot$, with the Sunyaev-Zel'dovich data confirming that we detect clusters with masses up to $M_{500}\sim5\times10^{14} \mathrm{M}_\odot$ $(M_{200}\sim10^{15} \mathrm{M}_\odot)$.
58 citations
TL;DR: Wu et al. as discussed by the authors measured the supermassive black hole masses of five z ∼ 2 Hot DOGs via broad Hα emission lines, using Keck/MOSFIRE and Gemini/FLAMINGOS-2.
Abstract: Author(s): Wu, J; Jun, HD; Assef, RJ; Tsai, CW; Wright, EL; Eisenhardt, PRM; Blain, A; Stern, D; Diaz-Santos, T; Denney, KD; Hayden, BT; Perlmutter, S; Aldering, G; Boone, K; Fagrelius, P | Abstract: Hot, dust-obscured galaxies, or "Hot DOGs," are a rare, dusty, hyperluminous galaxy population discovered by the WISE mission. Predominantly at redshifts 2-3, they include the most luminous known galaxies in the universe. Their high luminosities likely come from accretion onto highly obscured supermassive black holes (SMBHs). We have conducted a pilot survey to measure the SMBH masses of five z ∼ 2 Hot DOGs via broad Hα emission lines, using Keck/MOSFIRE and Gemini/FLAMINGOS-2. We detect broad Hα emission in all five Hot DOGs. We find substantial corresponding SMBH masses for these Hot DOGs (∼ 109 M⊙), and their derived Eddington ratios are close to unity. These z ∼ 2 Hot DOGs are the most luminous active galactic nuclei for their BH masses, suggesting that they are accreting at the maximum rates for their BHs. A similar property is found for known z ∼ 6 quasars. Our results are consistent with scenarios in which Hot DOGs represent a transitional, high-accretion phase between obscured and unobscured quasars. Hot DOGs may mark a special evolutionary stage before the red quasar and optical quasar phases, and they may be present at other cosmic epochs.
39 citations
Goddard Space Flight Center1, Johns Hopkins University2, Harris Corporation3, Grumman Aircraft Corporation4, California Institute of Technology5, University of Connecticut6, University of Maryland, College Park7, Advanced Technology Center8, NASA Headquarters9, University of Michigan10, University of California, Irvine11, Chalmers University of Technology12, Ames Research Center13, University of California, Santa Cruz14, University of Paris15, Netherlands Institute for Space Research16, Space Telescope Science Institute17, Harvard University18, University of Florida19, University of Massachusetts Amherst20, University of Tokyo21, University of California, San Diego22, University of British Columbia23, University of Arizona24, University of Illinois at Urbana–Champaign25, University of California, Los Angeles26
TL;DR: The OST study team will present a scientifically compelling, executable mission concept to the 2020 Decadal Survey in Astrophysics and study two alternative mission concepts.
Abstract: The Origins Space Telescope (OST) will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did the universe evolve in response to its changing ingredients? How common are life-bearing planets? To accomplish its scientific objectives, OST will operate at mid- and far-infrared wavelengths and offer superlative sensitivity and new spectroscopic capabilities. The OST study team will present a scientifically compelling, executable mission concept to the 2020 Decadal Survey in Astrophysics. To understand the concept solution space, our team studied two alternative mission concepts. We report on the study approach and describe both of these concepts, give the rationale for major design decisions, and briefly describe the mission-enabling technology.
32 citations
TL;DR: In this article, the spectral energy distributions of brown dwarfs with decreasing effective temperature were examined. But the spectral properties of the Y dwarfs were not investigated. And the authors also presented the discovery of 6 new late-T dwarfs, updated spectra of two T dwarfs and the reclassification of a new Y dwarf, WISE J033605.04$-$014351.0, based on Keck/NIRSPEC $J$-band spectroscopy.
Abstract: Y dwarfs provide a unique opportunity to study free-floating objects with masses $<$30 M$_{Jup}$ and atmospheric temperatures approaching those of known Jupiter-like exoplanets. Obtaining distances to these objects is an essential step towards characterizing their absolute physical properties. Using Spitzer/IRAC [4.5] images taken over baselines of $\sim$2-7 years, we measure astrometric distances for 22 late-T and early Y dwarfs, including updated parallaxes for 18 objects and new parallax measurements for 4 objects. These parallaxes will make it possible to explore the physical parameter space occupied by the coldest brown dwarfs. We also present the discovery of 6 new late-T dwarfs, updated spectra of two T dwarfs, and the reclassification of a new Y dwarf, WISE J033605.04$-$014351.0, based on Keck/NIRSPEC $J$-band spectroscopy. Assuming that effective temperatures are inversely proportional to absolute magnitude, we examine trends in the evolution of the spectral energy distributions of brown dwarfs with decreasing effective temperature. Surprisingly, the Y dwarf class encompasses a large range in absolute magnitude in the near- to mid-infrared photometric bandpasses, demonstrating a larger range of effective temperatures than previously assumed. This sample will be ideal for obtaining mid-infrared spectra with the James Webb Space Telescope because their known distances will make it easier to measure absolute physical properties.
30 citations
TL;DR: In this article, the authors identify new Y- and T-type brown dwarfs from the WISE All Sky data release using images obtained in filters that divide the traditional near-infrared H and J bands into two halves.
Abstract: We identify new Y- and T-type brown dwarfs from the WISE All Sky data release using images obtained in filters that divide the traditional near-infrared H and J bands into two halves—specifically CH_(4s) and CH_4l in the H and J2, and J3 in the J. This proves to be very effective at identifying cool brown dwarfs via the detection of their methane absorption, as well as providing preliminary classification using methane colors and WISE -to-near-infrared colors. New and updated calibrations between T/Y spectral types and CH_(4s)–CH_4l J3–W2, and CH_(4s)–W2 colors are derived, producing classification estimates good to a few spectral sub-types. We present photometry for a large sample of T and Y dwarfs in these filters, together with spectroscopy for 23 new ultra-cool dwarfs—2 Y dwarfs and 21 T dwarfs. We identify a further 8 new cool brown dwarfs, which we have high confidence are T dwarfs based on their methane photometry. We find that, for objects observed on a 4 m class telescope at J-band magnitudes of ~20 or brighter, CH_(4s)–CH_4l is the more powerful color for detecting objects and then estimating spectral types. Due to the lower sky background in the J-band, the J3 and J2 bands are more useful for identifying fainter cool dwarfs at J ≳ 22. The J3–J2 color is poor at estimating spectral types. But fortunately, once J3–J2 confirms that an object is a cool dwarf, the J3–W2 color is very effective at estimating approximate spectral types.
29 citations
TL;DR: In this article, the spectral energy distributions of brown dwarfs with decreasing effective temperature were examined. But the spectral properties of the Y dwarfs were not investigated. And the authors also presented the discovery of 6 new late-T dwarfs, updated spectra of two T dwarfs and the reclassification of a new Y dwarf, WISE J033605.04$-$014351.0, based on Keck/NIRSPEC $J$-band spectroscopy.
Abstract: Y dwarfs provide a unique opportunity to study free-floating objects with masses $<$30 M$_{Jup}$ and atmospheric temperatures approaching those of known Jupiter-like exoplanets. Obtaining distances to these objects is an essential step towards characterizing their absolute physical properties. Using Spitzer/IRAC [4.5] images taken over baselines of $\sim$2-7 years, we measure astrometric distances for 22 late-T and early Y dwarfs, including updated parallaxes for 18 objects and new parallax measurements for 4 objects. These parallaxes will make it possible to explore the physical parameter space occupied by the coldest brown dwarfs. We also present the discovery of 6 new late-T dwarfs, updated spectra of two T dwarfs, and the reclassification of a new Y dwarf, WISE J033605.04$-$014351.0, based on Keck/NIRSPEC $J$-band spectroscopy. Assuming that effective temperatures are inversely proportional to absolute magnitude, we examine trends in the evolution of the spectral energy distributions of brown dwarfs with decreasing effective temperature. Surprisingly, the Y dwarf class encompasses a large range in absolute magnitude in the near- to mid-infrared photometric bandpasses, demonstrating a larger range of effective temperatures than previously assumed. This sample will be ideal for obtaining mid-infrared spectra with the James Webb Space Telescope because their known distances will make it easier to measure absolute physical properties.
18 citations
TL;DR: In this paper, the authors used optical and near-infrared spectroscopy to observe rest-UV emission lines and estimate the black hole mass of WISEA J224607.56-052634.
Abstract: We use optical and near-infrared spectroscopy to observe rest-UV emission lines and estimate the black hole mass of WISEA J224607.56-052634.9 (W2246-0526) at z = 4.601, the most luminous hot, dust-obscured galaxy yet discovered by WISE. From the broad component of the Mg ii 2799 A emission line, we measure a black hole mass of log(M BH/M ) = 9.6 ± 0.4. The broad C iv 1549 A line is asymmetric and significantly blueshifted. The derived M BH from the blueshift-corrected broad C iv line width agrees with the Mg ii result. From direct measurement using a well-sampled SED, the bolometric luminosity is 3.6 -1014 L . The corresponding Eddington ratio for W2246-0526 is λ Edd = L AGN/L Edd = 2.8. This high Eddington ratio may reach the level where the luminosity is saturating due to photon trapping in the accretion flow and may be insensitive to the mass accretion rate. In this case, the M BH growth rate in W2246-0526 would exceed the apparent accretion rate derived from the observed luminosity.
18 citations
Posted Content•
TL;DR: In this paper, the authors show that the accuracy of the infrared albedo of the two asteroids published by Myhrvold et al. (2018b) is incorrect and overestimates their differences.
Abstract: We show that a number of claims made in Myhrvold (2018) (hereafter M2018b) regarding the WISE data and thermal modeling of asteroids are incorrect. That paper provides thermal fit parameter outputs for only two of the about 150,000 object dataset and does not make a direct comparison to asteroids with diameters measured by other means to assess the quality of that work's thermal model. We are unable to reproduce the results for the two objects for which M2018b published its own thermal fit outputs, including diameter, albedo, beaming, and infrared albedo. In particular, the infrared albedos published in M2018b are unphysically low. [...]
While there were some minor issues with consistency between tables due to clerical errors in the WISE/NEOWISE team's various papers and data release in the Planetary Data System, and a software issue that slightly increased diameter uncertainties in some cases, these issues do not substantially change the results and conclusions drawn from the data. We have shown in previous work and with updated analyses presented here that the effective spherical diameters for asteroids published to date are accurate to within the previously quoted minimum systematic 1-sigma uncertainty of about 10 percent when data of appropriate quality and quantity are available. Moreover, we show that the method used by M2018b to compare diameters between various asteroid datasets is incorrect and overestimates their differences. In addition, among other misconceptions in M2018b, we show that the WISE photometric measurement uncertainties are appropriately characterized and used by the WISE data processing pipeline and NEOWISE thermal modeling software. We show that the Near-Earth Asteroid Thermal Model (Harris 1998) employed by the NEOWISE team is a very useful model for analyzing infrared data to derive diameters and albedos when used properly.
13 citations
TL;DR: In this article, the authors report on the parameters for the luminosity function of galaxies obtained from applying the spectroluminosity functional based methods defined in Lake et al. (2017b) to the data sets described in Lake and Wright (2017a) using the mean and covariance of $2.4, µ$m normalized SEDs from Lake & Wright (2016).
Abstract: The WISE satellite surveyed the entire sky multiple times in four infrared wavelengths (3.4, 4.6, 12, and $22\\,\\mu$m; Wright et al. 2010). The unprecedented combination of coverage area and depth gives us the opportunity to measure the luminosity function of galaxies, one of the fundamental quantities in the study of them, at $2.4\\ \\mu$m to an unparalleled level of formal statistical accuracy in the near infrared. The big advantage of measuring luminosity functions at wavelengths in the window $\\approx 2$ to $3.5\\,\\mu$m is that it correlates more closely to the total stellar mass in galaxies than others. In this paper we report on the parameters for the $2.4\\,\\mu$m luminosity function of galaxies obtained from applying the spectroluminosity functional based methods defined in Lake et al. (2017b) to the data sets described in Lake et al. (2017a) using the mean and covariance of $2.4\\,\\mu$m normalized SEDs from Lake & Wright (2016). In terms of single Schechter function parameters evaluated at the present epoch, the combined result is: $\\phi_\\star = 5.8 \\pm [0.3_{\\mathrm{stat}},\\, 0.3_{\\mathrm{sys}}] \\times 10^{-3} \\operatorname{Mpc}^{-3}$, $L_\\star = 6.4 \\pm [0.1_{\\mathrm{stat}},\\, 0.3_{\\mathrm{sys}}] \\times 10^{10}\\, L_{2.4\\,\\mu\\mathrm{m}\\,\\odot}$ ($M_\\star = -21.67 \\pm [0.02_{\\mathrm{stat}},\\, 0.05_{\\mathrm{sys}}]\\operatorname{AB\\ mag}$), and $\\alpha = -1.050 \\pm [0.004_{\\mathrm{stat}},\\, 0.03_{\\mathrm{sys}}]$, corresponding to a galaxy number density of $0.08\\operatorname{Mpc}^{-3}$ brighter than $10^6\\, L_{2.4\\,\\mu\\mathrm{m}\\,\\odot}$ ($10^{-3} \\operatorname{Mpc}^{-3}$ brighter than $L_\\star$) and a $2.4\\,\\mu$m luminosity density equivalent to $3.8\\times10^{8}\\,L_{2.4\\,\\mu\\mathrm{m}\\,\\odot}\\operatorname{Mpc}^{-3}$. $\\ldots$
Space Telescope Science Institute1, California Institute of Technology2, University of Connecticut3, University of Maryland, College Park4, University of Michigan5, University of California, Irvine6, University of California, Santa Cruz7, Goddard Space Flight Center8, University of California, San Diego9, Johns Hopkins University10, University of Arizona11, NASA Headquarters12, Chalmers University of Technology13, Ames Research Center14, University of Paris15, Netherlands Institute for Space Research16, Cornell University17, Harvard University18, Florida State University19, University of Tokyo20, University of British Columbia21, University of Illinois at Urbana–Champaign22, University of California, Los Angeles23
TL;DR: The Origins Space Telescope (OST) mission concept study is the subject of one of the four science and technology definition studies supported by NASA Headquarters to prepare for the 2020 Astronomy and Astrophysics Decadal Survey as discussed by the authors.
Abstract: The Origins Space Telescope (OST) mission concept study is the subject of one of the four science and technology definition studies supported by NASA Headquarters to prepare for the 2020 Astronomy and Astrophysics Decadal Survey. OST will survey the most distant galaxies to discern the rise of metals and dust and to unveil the co-evolution of galaxy and blackhole formation, study the Milky Way to follow the path of water from the interstellar medium to habitable worlds in planetary systems, and measure biosignatures from exoplanets. This paper describes the science drivers and how they drove key requirements for OST Mission Concept 2, which will operate between ~5 and ~600 microns with a JWST sized telescope. Mission Concept 2 for the OST study optimizes the engineering for the key science cases into a powerful and more economical observatory compared to Mission Concept 1.
TL;DR: In this article, the authors conducted a search of the first three years of the reactivated NEOWISE data, looking for near-Earth objects discovered by ground-based surveys that have previously unreported thermal infrared data.
Abstract: Automated asteroid detection routines set requirements on the number of detections, signal-to-noise ratio, and the linearity of the expected motion in order to balance completeness, reliability, and time delay after data acquisition when identifying moving object tracklets. However, when the full-frame data from a survey are archived, they can be searched later for asteroids that were below the initial detection thresholds. We have conducted such a search of the first three years of the reactivated NEOWISE data, looking for near-Earth objects discovered by ground-based surveys that have previously unreported thermal infrared data. Using these measurements, we can then perform thermal modeling to measure the diameters and albedos of these objects. We present new physical properties for 116 Near-Earth Objects found in this search.
TL;DR: In this article, a method for bounding the actual NEOWISE diameter errors in the Main Belt based on the knowledge of the albedos of asteroid families is presented, and it is shown that the 1 sigma relative diameter error for the main Belt population must be less than 17.5% for the vast majority of objects.
Abstract: Quantifying the accuracy with which physical properties of asteroids can be determined from thermal modeling is critical to measuring the impact of infrared data on our understanding of asteroids. Previous work (Mainzer et al. 2011b) has used independently-derived diameters (from asteroid radar, occultations, and spacecraft visits) to test the accuracy of the NEOWISE diameter determinations. Here, we present a new and different method for bounding the actual NEOWISE diameter errors in the Main Belt based on our knowledge of the albedos of asteroid families. We show the 1 sigma relative diameter error for the Main Belt population must be less than 17.5% for the vast majority of objects. For a typical uncertainty on H magnitude of 0.2 mag, the relative error on diameter for the population would be ~10%.
TL;DR: In this article, the authors conducted a search of the first three years of the reactivated Near Earth Object Wide-field Infrared Survey Explorer data, looking for near-Earth objects discovered by ground-based surveys that have previously unreported thermal infrared data.
Abstract: Automated asteroid detection routines set requirements on the number of detections, signal-to-noise ratio, and the linearity of the expected motion in order to balance completeness, reliability, and time delay after data acquisition when identifying moving object tracklets. However, when the full-frame data from a survey are archived, they can be searched later for asteroids that were below the initial detection thresholds. We have conducted such a search of the first three years of the reactivated Near-Earth Object Wide-field Infrared Survey Explorer data, looking for near-Earth objects discovered by ground-based surveys that have previously unreported thermal infrared data. Using these measurements, we can then perform thermal modeling to measure the diameters and albedos of these objects. We present new physical properties for 116 Near-Earth Objects found in this search.
TL;DR: In this paper, a new method for bounding the actual NEOWISE diameter errors in the Main Belt based on knowledge of the albedos of asteroid families was presented, and it was shown that the 1σ relative diameter error for the main Belt population must be less than 17.5% for the vast majority of objects.
Abstract: Quantifying the accuracy with which physical properties of asteroids can be determined from thermal modeling is critical to measuring the impact of infrared data on our understanding of asteroids. Previous work has used independently derived diameters (from asteroid radar, occultations, and spacecraft visits) to test the accuracy of the NEOWISE diameter determinations. Here, we present a new and different method for bounding the actual NEOWISE diameter errors in the Main Belt based on our knowledge of the albedos of asteroid families. We show the 1σ relative diameter error for the Main Belt population must be less than 17.5% for the vast majority of objects. For a typical uncertainty on H magnitude of 0.2 mag, the relative error on diameter for the population would be ~10%.
TL;DR: The combination of the AKARI and WISE infrared all-sky surveys provides an unique opportunity to identify and characterize the most highly dust obscured AGNs in the universe as mentioned in this paper, but these AGNs are not easily detectable and potentially underrepresented in extragalactic surveys due to their high optical extinction.
Abstract: The combination of the AKARI and WISE infrared all-sky surveys provides an unique opportunity to identify and characterize the most highly dust obscured AGNs in the universe. Dust-obscured AGNs are not easily detectable and potentially underrepresented in extragalactic surveys due to their high optical extinction, but are readily found in the WISE catalog due to their extremely red mid-IR colors. Combining these surveys with photometry from Pan-STARRS and Herschel, we use SED modeling to characterize the extinction and dust properties of these AGNs. From mid-IR WISE colors, we are able to compute bolometric corrections to AGN luminosities. Using AKARI's far-IR wavelength photometry and broadband AGN/galaxy spectral templates, we estimate AGN dust mass and temperature using simple analytic models with 3-4 parameters. Even without spectroscopic data, we can determine a number of AGN dust properties only using SED analysis. These methods, combined with the abundance of archival photometric data publically available, will be valuable for large-scale studies of dusty, IR-luminous AGNs.
TL;DR: In this article, the authors used optical and near-infrared spectroscopy to observe rest-UV emission lines and estimate the black hole mass of WISEA J224607.56-052634, the most luminous hot dust-obscured galaxy yet discovered by WISE.
Abstract: We use optical and near-infrared spectroscopy to observe rest-UV emission lines and estimate the black hole mass of WISEA J224607.56-052634.9 (W2246-0526) at z = 4.601, the most luminous hot dust-obscured galaxy yet discovered by WISE. From the broad component of the MgII-2799A emission line, we measure a black hole mass of log (M_BH/M_sun) = 9.6 +- 0.4. The broad CIV-1549A line is asymmetric and significantly blue-shifted. The derived M_BH from the blueshift-corrected broad CIV line width agrees with the MgII result. From direct measurement using a well-sampled SED, the bolometric luminosity is 3.6 * 10^14 L_sun. The corresponding Eddington ratio for W2246-0526 is lambda_Edd = L_AGN / L_Edd = 2.8. This high Eddington ratio may reach the level where the luminosity is saturating due to photon trapping in the accretion flow, and be insensitive to the mass accretion rate. In this case, the M_BH growth rate in W2246-0526 would exceed the apparent accretion rate derived from the observed luminosity.
07 Aug 2018
TL;DR: The WD 0806-661 system consists of a DQ white dwarf primary at 19.26 pc (Gaia Collaboration et al. 2018) and an extremely cold common proper motion companion at 130'' separation as mentioned in this paper.
Abstract: The WD 0806-661 system consists of a DQ white dwarf primary at 19.26 pc (Gaia Collaboration et al. 2018) and an extremely cold common proper motion companion at 130'' separation (WD 0806-661B; Luhman et al. 2011). Given its absolute magnitude at Spitzer [4.5], the cold companion is presumed to be either a Y type brown dwarf or giant planet. At a projected physical separation of ~2500 au, WD 0806-661B represents the widest known definitively planetary-mass companion, and may provide important insights into the processes of star and planet formation.
Unlike most Y dwarfs, WD 0806-661B has lacked a secure detection at 4.6 μm in the Wide-field Infrared Survey Explorer (WISE; Wright et al. 2010) W2 channel. WD 0806-661B was reported as a low-significance detection in the WISE All-Sky Source Catalog (Cutri et al. 2012), with W2 = 17.68 ± 0.41 (J080715.32-661851.6, w2snr = 2.5). No detection of a WD 0806-661B counterpart is reported in the AllWISE Source Catalog, although the AllWISE Reject Table contains a low-significance positional match (J080715.34-661852.1) with W2 = 17.85 ± 0.41 (Cutri et al. 2013). Both the All-Sky and AllWISE Reject best-fit W2 magnitudes, if taken at face value, would make WD 0806-661B a very blue outlier among Y dwarfs in [4.5]−W2 color, given that the W2 and [4.5] magnitudes of known Y dwarfs generally agree to within ~0.1 mag.
TL;DR: In this paper, the authors analyzed 11 different Halley-type Comets for dust production rates, CO+CO2 production rates and nucleus sizes, and concluded that there was no significant correlation between dust production and heliocentric distance.
Abstract: From the entire dataset of comets observed by NEOWISE, we have analyzed 11 different Halley-Type Comets (HTCs) for dust production rates, CO+CO2 production rates, and nucleus sizes. Incorporating HTCs from previous studies and multiple comet visits we have a total of 21 stacked visits, 13 of which are active and 8 for which we calculated upper limits of production. We determined the nucleus sizes of 27P, P/2006 HR30, P/2012 NJ, and C/2016 S1. Furthermore, we analyzed the relationships between dust production and heliocentric distance, and gas production and heliocentric distance. We concluded that for this population of HTCs, ranging in heliocentric distance from 1.21 AU to 2.66 AU, there was no significant correlation between dust production and heliocentric distance, nor gas production and heliocentric distance.
TL;DR: In this article, Lake et al. describe a data set that results from matching five public red-shift surveys with the AllWISE data release, along with a reanalysis of the data described in Lake et. 2012.
Abstract: The WISE satellite surveyed the entire sky multiple times in four infrared (IR) wavelengths ($3.4,\\ 4.6,\\ 12,$ and $22\\, \\mu$m, Wright et al. 2010). This all-sky IR photometric survey makes it possible to leverage many of the large publicly available spectroscopic redshift surveys to measure galaxy properties in the IR. While characterizing the cross-matching of WISE data to a single survey is a straightforward process, doing it with six different redshift surveys takes a fair amount of space to characterize adequately, because each survey has unique caveats and characteristics that need addressing. This work describes a data set that results from matching five public redshift surveys with the AllWISE data release, along with a reanalysis of the data described in Lake et al. 2012. The combined data set has an additional flux limit of $80\\,\\mu$Jy ($19.14$ AB mag) in WISE's W1 filter imposed in order to limit it to targets with high completeness and reliable photometry in the AllWISE data set. Consistent analysis of all of the data is only possible if the color bias discussed in Ilbert et al. (2004) is addressed (for example: the techniques explored in the first paper in this series Lake et al. 2017b). The sample defined herein is used in this paper's sequel paper, Lake et al. 2017a), to measure the luminosity function of galaxies at $2.4\\, \\mu$m rest frame wavelength, and the selection process of the sample is optimized for this purpose.
TL;DR: Lam et al. as mentioned in this paper identified potentially obscured AGNs using mid-IR color colors from the Wide-Field Infrared Survey Explorer (WISE) catalog using Keck DEIMOS and their physical properties derived from these spectra.
Abstract: Author(s): Lam, Anson; Wright, Edward; Malkan, Matthew | Abstract: While there are numerous criteria for photometrically identifying active galactic nuclei (AGNs), searches in the optical and UV tend to exclude galaxies that are highly dust obscured This is problematic for constraining models of AGN evolution and estimating the AGN contribution to the cosmic X-ray and IR backgrounds, as highly obscured objects tend to be underrepresented in large-scale surveys To address this, we identify potentially obscured AGNs using mid-IR color colors from the Wide-field Infrared Survey Explorer (WISE) catalog This paper presents the results of optical spectroscopy of obscured AGN candidates using Keck DEIMOS, and their physical properties derived from these spectra We find that a $W1-W2g08$ color criterion effectively selects AGNs with a higher median level of $E(B-V)$ extinction compared to the AGNs found in the SDSS DR7 survey This optical extinction can be measured using SED modeling or by using $r-W1$ as a measure of optical to IR flux We find that specific, targeted observations are necessary to find the most highly optically obscured AGNs, and that additional far-IR photometry is necessary to further constrain the dust properties of these AGNs
TL;DR: In this paper, the authors investigate the value of the near-infrared imaging from upcoming surveys for constraining the ellipticities of galaxies, and they select galaxies between 0.5 ≤ z 1.4 and therefore the standard error in NIR-derived ellipticity is about 30% smaller.
Abstract: We investigate the value of the near-infrared imaging from upcoming surveys for constraining the ellipticities of galaxies. We select galaxies between 0.5 ≤ z 1.0, the NIR-selected source density is higher by a factor of 1.4 and therefore the standard error in NIR-derived ellipticities is about 30% smaller, implying a more precise ellipticity measurement. The good performance of the NIR is mainly because galaxies have an intrinsically smoother light distribution in the NIR bands than in the optical, the latter tracing the clumpy star-forming regions. In addition, the NIR bands have a higher surface brightness per pixel than the optical images, while being less affected by dust attenuation. Despite the worse spatial sampling and resolution of Euclid NIR compared to optical, the NIR approach yields equivalent or more precise galaxy ellipticity measurements. If systematics that affect shape such as dithering strategy and point-spread function undersampling can be mitigated, inclusion of the NIR can improve galaxy ellipticity measurements over all redshifts. This is particularly important for upcoming weak lensing surveys, such as with Euclid and WFIRST.
Abstract: We identify new Y- and T-type brown dwarfs from the WISE All Sky data release using images obtained in filters that divide the traditional near-infrared H and J bands into two halves -- specifically CH4s & CH4l in the H and J2 & J3 in the J. This proves to be very effective at identifying cool brown dwarfs via the detection of their methane absorption, as well as providing preliminary classification using methane colours and WISE-to-near-infrared colours. New and updated calibrations between T/Y spectral types and CH4s-CH4l, J3-W2, and CH4s-W2 colours are derived, producing classification estimates good to a few spectral sub-types. We present photometry for a large sample of T and Y dwarfs in these filters, together with spectroscopy for 23 new ultra-cool dwarfs - two Y dwarfs and twenty one T dwarfs. We identify a further 8 new cool brown dwarfs, which we have high confidence are T dwarfs based on their methane photometry. We find that, for objects observed on a 4m-class telescope at J band magnitudes of ~20 or brighter, CH4s-CH4l is the more powerful colour for detecting objects and then estimating spectral types. Due to the lower sky background in the J-band, the J3 and J2 bands are more useful for identifying fainter cool dwarfs at J>22. The J3-J2 colour is poor at estimating spectral types. But fortunately, once J3-J2 confirms that an object is a cool dwarf, the J3-W2 colour is very effective at estimating approximate spectral types.
TL;DR: In this article, the authors investigate the value of the near-infrared imaging from upcoming surveys for constraining the ellipticities of galaxies and select galaxies between 0.5 1.4 and 1.0.
Abstract: We investigate the value of the near-infrared imaging from upcoming surveys for constraining the ellipticities of galaxies. We select galaxies between 0.5 1.0, the NIR-selected source density is higher by a factor of 1.4 and therefore the standard error in NIR-derived ellipticities is about 30% smaller, implying a more precise ellipticity measurement. The good performance of the NIR is mainly because galaxies have an intrinsically smoother light distribution in the NIR bands than in the optical, the latter tracing the clumpy star-forming regions. In addition, the NIR bands have a higher surface brightness per pixel than the optical images, while being less affected by dust attenuation. Despite the worse spatial sampling and resolution of Euclid NIR compared to optical, the NIR approach yields equivalent or more precise galaxy ellipticity measurements. If systematics that affect shape such as dithering strategy and point spread function undersampling can be mitigated, inclusion of the NIR can improve galaxy ellipticity measurements over all redshifts. This is particularly important for upcoming weak lensing surveys, such as with Euclid and WFIRST.
University of Connecticut1, California Institute of Technology2, University of Michigan3, Jet Propulsion Laboratory4, Space Telescope Science Institute5, Johns Hopkins University6, University of Massachusetts Amherst7, University of California, Irvine8, Goddard Space Flight Center9, University of British Columbia10, University of Maryland, College Park11, Ames Research Center12, University of California, Santa Cruz13, Cornell University14, Harvard University15, University of Florida16, University of California, San Diego17, University of Arizona18, University of Illinois at Urbana–Champaign19, University of California, Los Angeles20, NASA Headquarters21, University of Paris22, Netherlands Institute for Space Research23, University of Tokyo24
TL;DR: The Origins Space Telescope (OSST) as discussed by the authors is one of four large mission concept studies sponsored by NASA for review in the 2020 US Astrophysics Decadal Survey, which will open unprecedented discovery space in the infrared, unveiling our cosmic origins.
Abstract: The Origins Space Telescope, one of four large Mission Concept studies sponsored by NASA for review in the 2020 US Astrophysics Decadal Survey, will open unprecedented discovery space in the infrared, unveiling our cosmic origins. We briefly describe in this article the key science themes and architecture for OST. With a sensitivity gain of up to a factor of 1,000 over any previous or planned mission, OST will open unprecedented discovery space, allow us to peer through an infrared window teeming with possibility. OST will fundamentally change our understanding of our cosmic origins - from the growth of galaxies and black holes, to uncovering the trail of water, to life signs in nearby Earth-size planets, and discoveries never imagined. Built to be highly adaptable, while addressing key science across many areas of astrophysics, OST will usher in a new era of infrared astronomy.