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Showing papers in "The Astronomical Journal in 2016"


Journal ArticleDOI
Kyle S. Dawson1, Jean-Paul Kneib2, Will J. Percival3, Shadab Alam4  +155 moreInstitutions (51)
TL;DR: The Extended Baryon Oscillation Spectroscopic Survey (eBOSS) as mentioned in this paper uses four different tracers of the underlying matter density field to expand the volume covered by BOSS and map the large-scale structures over the relatively unconstrained redshift range 0.6 0.87.
Abstract: In a six-year program started in 2014 July, the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) will conduct novel cosmological observations using the BOSS spectrograph at Apache Point Observatory. These observations will be conducted simultaneously with the Time Domain Spectroscopic Survey (TDSS) designed for variability studies and the Spectroscopic Identification of eROSITA Sources (SPIDERS) program designed for studies of X-ray sources. In particular, eBOSS will measure with percent-level precision the distance-redshift relation with baryon acoustic oscillations (BAO) in the clustering of matter. eBOSS will use four different tracers of the underlying matter density field to vastly expand the volume covered by BOSS and map the large-scale-structures over the relatively unconstrained redshift range 0.6 0.6 sample of BOSS galaxies. With ~195,000 new emission line galaxy redshifts, we expect BAO measurements of d_A(z) to an accuracy of 3.1% and H(z) to 4.7% at an effective redshift of z = 0.87. A sample of more than 500,000 spectroscopically confirmed quasars will provide the first BAO distance measurements over the redshift range 0.9 2.1; these new data will enhance the precision of dA(z) and H(z) at z > 2.1 by a factor of 1.44 relative to BOSS. Furthermore, eBOSS will provide improved tests of General Relativity on cosmological scales through redshift-space distortion measurements, improved tests for non-Gaussianity in the primordial density field, and new constraints on the summed mass of all neutrino species. Here, we provide an overview of the cosmological goals, spectroscopic target sample, demonstration of spectral quality from early data, and projected cosmological constraints from eBOSS.

648 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present a survey of the Spanish participation groups in the International Journal of Astronautic and Astronautical Engineering (IoAIAE 2014), which includes the Spanish Ministry of Economy and Competitiveness (MINECO), the Hungarian Academy of Sciences, and the National Science Foundation (NSF).
Abstract: NSF [AST11-09718, AST-907873]; Alfred P. Sloan Foundation; National Science Foundation; U.S. Department of Energy Office of Science; University of Arizona; Brazilian Participation Group; Brookhaven National Laboratory; University of Cambridge; Carnegie Mellon University; University of Florida; French Participation Group; German Participation Group; Harvard University; Instituto de Astrofisica de Canarias; Michigan State/Notre Dame/JINA Participation Group; Johns Hopkins University; Lawrence Berkeley National Laboratory; Max Planck Institute for Astrophysics; Max Planck Institute for Extraterrestrial Physics; New Mexico State University; New York University; Ohio State University; Pennsylvania State University; University of Portsmouth; Princeton University; Spanish Participation Group; University of Tokyo; University of Utah; Vanderbilt University; University of Virginia; University of Washington; Yale University; Spanish Ministry of Economy and Competitiveness (MINECO) [AYA2014-56359-P]; Janos Bolyai Research Scholarship of the Hungarian Academy of Sciences; Spanish Ministry of Economy and Competitiveness [AYA-2011-27754, AYA2014-58082-P]

633 citations


Journal ArticleDOI
TL;DR: SPARC (Spitzer Photometry & Accurate Rotation Curves) as mentioned in this paper is a sample of 175 nearby galaxies with new surface photometry at 3.6 um and high-quality rotation curves from previous HI/Halpha studies.
Abstract: We introduce SPARC (Spitzer Photometry & Accurate Rotation Curves): a sample of 175 nearby galaxies with new surface photometry at 3.6 um and high-quality rotation curves from previous HI/Halpha studies. SPARC spans a broad range of morphologies (S0 to Irr), luminosities (~5 dex), and surface brightnesses (~4 dex). We derive [3.6] surface photometry and study structural relations of stellar and gas disks. We find that both the stellar mass-HI mass relation and the stellar radius-HI radius relation have significant intrinsic scatter, while the HI mass-radius relation is extremely tight. We build detailed mass models and quantify the ratio of baryonic-to-observed velocity (Vbar/Vobs) for different characteristic radii and values of the stellar mass-to-light ratio (M/L) at [3.6]. Assuming M/L=0.5 Msun/Lsun (as suggested by stellar population models) we find that (i) the gas fraction linearly correlates with total luminosity, (ii) the transition from star-dominated to gas-dominated galaxies roughly corresponds to the transition from spiral galaxies to dwarf irregulars in line with density wave theory; and (iii) Vbar/Vobs varies with luminosity and surface brightness: high-mass, high-surface-brightness galaxies are nearly maximal, while low-mass, low-surface-brightness galaxies are submaximal. These basic properties are lost for low values of M/L=0.2 Msun/Lsun as suggested by the DiskMass survey. The mean maximum-disk limit in bright galaxies is M/L=0.7 Msun/Lsun at [3.6]. The SPARC data are publicly available and represent an ideal test-bed for models of galaxy formation.

513 citations


Journal ArticleDOI
TL;DR: In this paper, the authors show that the orbits of distant Kuiper Belt objects (KBOs) cluster not only in argument of perihelion, but also in physical space.
Abstract: Recent analyses have shown that distant orbits within the scattered disk population of the Kuiper Belt exhibit an unexpected clustering in their respective arguments of perihelion. While several hypotheses have been put forward to explain this alignment, to date, a theoretical model that can successfully account for the observations remains elusive. In this work we show that the orbits of distant Kuiper Belt objects (KBOs) cluster not only in argument of perihelion, but also in physical space. We demonstrate that the perihelion positions and orbital planes of the objects are tightly confined and that such a clustering has only a probability of 0.007% to be due to chance, thus requiring a dynamical origin. We find that the observed orbital alignment can be maintained by a distant eccentric planet with mass ≳ 10 m_⊕ whose orbit lies in approximately the same plane as those of the distant KBOs, but whose perihelion is 180° away from the perihelia of the minor bodies. In addition to accounting for the observed orbital alignment, the existence of such a planet naturally explains the presence of high-perihelion Sedna-like objects, as well as the known collection of high semimajor axis objects with inclinations between 60° and 150° whose origin was previously unclear. Continued analysis of both distant and highly inclined outer solar system objects provides the opportunity for testing our hypothesis as well as further constraining the orbital elements and mass of the distant planet.

380 citations


Journal ArticleDOI
TL;DR: The final catalog of eclipsing binary systems within the 105 deg^2 Kepler field of view is presented in this paper, where the authors identify several classes of systems including those that exhibit tertiary eclipse events, systems that show clear evidence of additional bodies, heartbeat systems, and systems exhibiting only one eclipse event over the duration of the mission.
Abstract: The primary Kepler Mission provided nearly continuous monitoring of ~200,000 objects with unprecedented photometric precision. We present the final catalog of eclipsing binary systems within the 105 deg^2 Kepler field of view. This release incorporates the full extent of the data from the primary mission (Q0-Q17 Data Release). As a result, new systems have been added, additional false positives have been removed, ephemerides and principal parameters have been recomputed, classifications have been revised to rely on analytical models, and eclipse timing variations have been computed for each system. We identify several classes of systems including those that exhibit tertiary eclipse events, systems that show clear evidence of additional bodies, heartbeat systems, systems with changing eclipse depths, and systems exhibiting only one eclipse event over the duration of the mission. We have updated the period and galactic latitude distribution diagrams and included a catalog completeness evaluation. The total number of identified eclipsing and ellipsoidal binary systems in the Kepler field of view has increased to 2878, 1.3% of all observed Kepler targets. An online version of this catalog with downloadable content and visualization tools is maintained athttp://keplerEBs.villanova.edu.

373 citations


Journal ArticleDOI
TL;DR: In this paper, the authors describe the MaNGA Data Reduction Pipeline algorithms and centralized metadata framework that produce sky-subtracted spectrophotometrically calibrated spectra and rectified three-dimensional data cubes that combine individual dithered observations.
Abstract: Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) is an optical fiber-bundle integral-field unit (IFU) spectroscopic survey that is one of three core programs in the fourth-generation Sloan Digital Sky Survey (SDSS-IV). With a spectral coverage of 3622–10354 A and an average footprint of ~500 arcsec2 per IFU the scientific data products derived from MaNGA will permit exploration of the internal structure of a statistically large sample of 10,000 low-redshift galaxies in unprecedented detail. Comprising 174 individually pluggable science and calibration IFUs with a near-constant data stream, MaNGA is expected to obtain ~100 million raw-frame spectra and ~10 million reduced galaxy spectra over the six-year lifetime of the survey. In this contribution, we describe the MaNGA Data Reduction Pipeline algorithms and centralized metadata framework that produce sky-subtracted spectrophotometrically calibrated spectra and rectified three-dimensional data cubes that combine individual dithered observations. For the 1390 galaxy data cubes released in Summer 2016 as part of SDSS-IV Data Release 13, we demonstrate that the MaNGA data have nearly Poisson-limited sky subtraction shortward of ~8500 A and reach a typical 10σ limiting continuum surface brightness μ = 23.5 AB arcsec-2 in a five-arcsecond-diameter aperture in the g-band. The wavelength calibration of the MaNGA data is accurate to 5 km s-1 rms, with a median spatial resolution of 2.54 arcsec FWHM (1.8 kpc at the median redshift of 0.037) and a median spectral resolution of σ = 72 km s-1.

326 citations


Journal ArticleDOI
TL;DR: In this paper, high-resolution imaging of 382 Kepler Objects of Interest (KOIs) obtained using adaptive-optics imaging and nonredundant aperture mask interferometry (NRM) on the Keck-II telescope was presented.
Abstract: The dynamical influence of binary companions is expected to profoundly influence planetary systems. However, the difficulty of identifying planets in binary systems has left the magnitude of this effect uncertain; despite numerous theoretical hurdles to their formation and survival, at least some binary systems clearly host planets. We present high-resolution imaging of 382 Kepler Objects of Interest (KOIs) obtained using adaptive-optics imaging and nonredundant aperture-mask interferometry (NRM) on the Keck-II telescope. Among the full sample of 506 candidate binary companions to KOIs, we super-resolve some binary systems to projected separations of 0.4; we instead only found 23 companions (a 4.6 sigma deficit), many of which must be wider pairs that are only close in projection. When the binary population is parametrized with a semimajor axis cutoff a_cut and a suppression factor inside that cutoff S_bin, we find with correlated uncertainties that inside a_cut = 47 +59/-23 AU, the planet occurrence rate in binary systems is only S_bin = 0.34 +0.14/-0.15 times that of wider binaries or single stars. Our results demonstrate that a fifth of all solar-type stars in the Milky Way are disallowed from hosting planetary systems due to the influence of a binary companion.

270 citations


Journal ArticleDOI
TL;DR: The MaNGA Survey (Mapping Nearby Galaxies at Apache Point Observatory) as discussed by the authors is one of the core programs in the Sloan Digital Sky Survey IV, which is obtaining integral field spectroscopy for 10,000 nearby galaxies at a spectral resolution of R ∼ 2000 from 3622 to 10354 A.
Abstract: The MaNGA Survey (Mapping Nearby Galaxies at Apache Point Observatory) is one of three core programs in the Sloan Digital Sky Survey IV. It is obtaining integral field spectroscopy for 10,000 nearby galaxies at a spectral resolution of R ∼ 2000 from 3622 to 10354 A. The design of the survey is driven by a set of science requirements on the precision of estimates of the following properties: star formation rate surface density, gas metallicity, stellar population age, metallicity, and abundance ratio, and their gradients; stellar and gas kinematics; and enclosed gravitational mass as a function of radius. We describe how these science requirements set the depth of the observations and dictate sample selection. The majority of targeted galaxies are selected to ensure uniform spatial coverage in units of effective radius (Re) while maximizing spatial resolution. About two-thirds of the sample is covered out to 1.5Re (Primary sample), and one-third of the sample is covered to 2.5Re (Secondary sample). We describe the survey execution with details that would be useful in the design of similar future surveys. We also present statistics on the achieved data quality, specifically the point-spread function, sampling uniformity, spectral resolution, sky subtraction, and flux calibration. For our Primary sample, the median r-band signal-to-noise ratio is ∼70 per 1.4 A pixel for spectra stacked between 1Re and 1.5Re. Measurements of various galaxy properties from the first-year data show that we are meeting or exceeding the defined requirements for the majority of our science goals.

268 citations


Journal ArticleDOI
TL;DR: The EPIC Variability Extraction and Removal for Exoplanet Science Targets (EVEREST) as discussed by the authors is an open-source pipeline for removing instrumental noise from K2 light curves.
Abstract: We present EPIC Variability Extraction and Removal for Exoplanet Science Targets (EVEREST), an open-source pipeline for removing instrumental noise from K2 light curves. EVEREST employs a variant of pixel level decorrelation to remove systematics introduced by the spacecraft's pointing error and a Gaussian process to capture astrophysical variability. We apply EVEREST to all K2 targets in campaigns 0–7, yielding light curves with precision comparable to that of the original Kepler mission for stars brighter than , and within a factor of two of the Kepler precision for fainter targets. We perform cross-validation and transit injection and recovery tests to validate the pipeline, and compare our light curves to the other de-trended light curves available for download at the MAST High Level Science Products archive. We find that EVEREST achieves the highest average precision of any of these pipelines for unsaturated K2 stars. The improved precision of these light curves will aid in exoplanet detection and characterization, investigations of stellar variability, asteroseismology, and other photometric studies. The EVEREST pipeline can also easily be applied to future surveys, such as the TESS mission, to correct for instrumental systematics and enable the detection of low signal-to-noise transiting exoplanets. The EVEREST light curves and the source code used to generate them are freely available online.

267 citations


Journal ArticleDOI
TL;DR: The IAU Working Group on Nominal Units for Stellar and Planetary Astronomy formed in 2011, uniting experts from the solar, stellar, planetary, exoplanetary, and fundamental astronomy, as well as from general standards as discussed by the authors.
Abstract: In this brief communication we provide the rationale for and the outcome of the International Astronomical Union (IAU) resolution vote at the XXIXth General Assembly in Honolulu, Hawaii, in 2015, on recommended nominal conversion constants for selected solar and planetary properties. The problem addressed by the resolution is a lack of established conversion constants between solar and planetary values and SI units: a missing standard has caused a proliferation of solar values (e.g., solar radius, solar irradiance, solar luminosity, solar effective temperature, and solar mass parameter) in the literature, with cited solar values typically based on best estimates at the time of paper writing. As precision of observations increases, a set of consistent values becomes increasingly important. To address this, an IAU Working Group on Nominal Units for Stellar and Planetary Astronomy formed in 2011, uniting experts from the solar, stellar, planetary, exoplanetary, and fundamental astronomy, as well as from general standards fields to converge on optimal values for nominal conversion constants. The effort resulted in the IAU 2015 Resolution B3, passed at the IAU General Assembly by a large majority. The resolution recommends the use of nominal solar and planetary values, which are by definition exact and are expressed in SI units. These nominal values should be understood as conversion factors only, not as the true solar/planetary properties or current best estimates. Authors and journal editors are urged to join in using the standard values set forth by this resolution in future work and publications to help minimize further confusion.

258 citations


Journal ArticleDOI
TL;DR: In this article, the authors presented 1625 new 15 GHz (2 cm) VLBA images of 295 jets associated with active galactic nuclei (AGNs) from the MOJAVE and 2 cm surveys, spanning observations between 1994 Aug 31 and 2013 Aug 20.
Abstract: We present 1625 new 15 GHz (2 cm) VLBA images of 295 jets associated with active galactic nuclei (AGNs) from the MOJAVE and 2 cm VLBA surveys, spanning observations between 1994 Aug 31 and 2013 Aug 20. For 274 AGNs with at least 5 VLBA epochs, we have analyzed the kinematics of 961 individual bright features in their parsec-scale jets. A total of 122 of these jets have not been previously analyzed by the MOJAVE program. In the case of 451 jet features that had at least 10 epochs, we also examined their kinematics for possible accelerations. At least half of the well-sampled features have non-radial and/or accelerating trajectories, indicating that non-ballistic motion is common in AGN jets. Since it is impossible to extrapolate any accelerations that occurred before our monitoring period, we could only determine reliable ejection dates for ∼ 24% of those features that had significant proper motions. The distribution of maximum apparent jet speeds in all 295 AGNs measured by our program to date is

Journal ArticleDOI
TL;DR: In this article, the distribution of rotation periods in the Pleiades was explored and the relationship between P and (V - K_s) was found to follow the overall trends found in other studies.
Abstract: Young (125 Myr), populous (>1000 members), and relatively nearby, the Pleiades has provided an anchor for stellar angular momentum models for both younger and older stars. We used K2 to explore the distribution of rotation periods in the Pleiades. With more than 500 new periods for Pleiades members, we are vastly expanding the number of Pleiades with periods, particularly at the low-mass end. About 92% of the members in our sample have at least one measured spot-modulated rotation period. For the ~8% of the members without periods, non-astrophysical effects often dominate (saturation, etc.), such that periodic signals might have been detectable, all other things being equal. We now have an unusually complete view of the rotation distribution in the Pleiades. The relationship between P and (V - K_s)_0 follows the overall trends found in other Pleiades studies. There is a slowly rotating sequence for 1.1 ≾ (V - K_s)_0 ≾ 3.7 and a primarily rapidly rotating population for (V - K_s)_0 ≳ 5.0. There is a region in which there seems to be a disorganized relationship between P and (V - K_s)_0 for 3.7 ≾ (V - K_s)_0 ≾ 5.0. Paper II continues the discussion, focusing on multiperiod structures, and Paper III speculates about the origin and evolution of the period distribution in the Pleiades.

Journal ArticleDOI
TL;DR: In this paper, a Mass-Luminosity Relation (MLR) for red dwarfs spanning a range of masses from 0.62 Msun to the end of the stellar main sequence at 0.08 Msun is presented.
Abstract: We present a Mass-Luminosity Relation (MLR) for red dwarfs spanning a range of masses from 0.62 Msun to the end of the stellar main sequence at 0.08 Msun. The relation is based on 47 stars for which dynamical masses have been determined, primarily using astrometric data from Fine Guidance Sensors (FGS) 3 and 1r, white-light interferometers on the Hubble Space Telescope (HST), and radial velocity data from McDonald Observatory. For our HST/FGS sample of 15 binaries component mass errors range from 0.4% to 4.0% with a median error of 1.8%. With these and masses from other sources, we construct a V-band MLR for the lower main sequence with 47 stars, and a K-band MLR with 45 stars with fit residuals half of those of the V-band. We use GJ 831 AB as an analysis example, obtaining an absolute trigonometric parallax, pi_abs = 125.3 +/- 0.3 milliseconds of arc, with orbital elements yielding MA = 0.270 +/- 0.004 Msun and MB = 0.145 +/- 0.002 Msun. The mass precision rivals that derived for eclipsing binaries. A remaining major task is the interpretation of the intrinsic cosmic scatter in the observed MLR for low mass stars in terms of physical effects. In the meantime, useful mass values can be estimated from the MLR for the ubiquitous red dwarfs that account for 75% of all stars, with applications ranging from the characterization of exoplanet host stars to the contribution of red dwarfs to the mass of the Universe.

Journal ArticleDOI
TL;DR: In this article, the Michigan/Magellan fiber system was used to detect high levels of r-process material in Reticulum 2 (Ret 2) stars, including 12 elements heavier than the Fe group, and the abundances of other alpha and Fe-group elements closely resemble those in ultra-faint dwarf galaxies and metal-poor halo stars.
Abstract: The ultra-faint dwarf galaxy Reticulum 2 (Ret 2) was recently discovered in images obtained by the Dark Energy Survey. We have observed the four brightest red giants in Ret 2 at high spectral resolution using the Michigan/Magellan Fiber System. We present detailed abundances for as many as 20 elements per star, including 12 elements heavier than the Fe group. We confirm previous detection of high levels of r-process material in Ret 2 (mean [Eu/Fe]=+1.69+/-0.05) found in three of these stars (mean [Fe/H]=-2.88+/-0.10). The abundances closely match the r-process pattern found in the well-studied metal-poor halo star CS22892-052. Such r-process-enhanced stars have not been found in any other ultra-faint dwarf galaxy, though their existence has been predicted by at least one model. The fourth star in Ret 2 ([Fe/H]=-3.42+/-0.20) contains only trace amounts of Sr ([Sr/Fe]=-1.73+/-0.43) and no detectable heavier elements. One r-process enhanced star is also enhanced in C (natal [C/Fe]=+1.1). This is only the third such star known, which suggests that the nucleosynthesis sites leading to C and r-process enhancements are decoupled. The r-process-deficient star is enhanced in Mg ([Mg/Fe]=+0.81+/-0.14), and the other three stars show normal levels of alpha-enhancement (mean [Mg/Fe]=+0.34+/-0.03). The abundances of other alpha and Fe-group elements closely resemble those in ultra-faint dwarf galaxies and metal-poor halo stars, suggesting that the nucleosynthesis that led to the large r-process enhancements either produced no light elements or produced light-element abundance signatures indistinguishable from normal supernovae.

Journal ArticleDOI
TL;DR: In this article, the authors present fits to the broadband photometric spectral energy distributions (SEDs) of 158 eclipsing binaries (EBs) in the Tycho-2 catalog, which have highly precise stellar radii, effective temperatures, and in many cases metallicities previously determined in the literature, and thus have bolometric luminosities that are typically good to 10%.
Abstract: We present fits to the broadband photometric spectral energy distributions (SEDs) of 158 eclipsing binaries (EBs) in the Tycho-2 catalog. These EBs were selected because they have highly precise stellar radii, effective temperatures, and in many cases metallicities previously determined in the literature, and thus have bolometric luminosities that are typically good to 10%. In most cases the available broadband photometry spans a wavelength range 0.4–10 μm, and in many cases spans 0.15–22 μm. The resulting SED fits, which have only extinction as a free parameter, provide a virtually model-independent measure of the bolometric flux at Earth. The SED fits are satisfactory for 156 of the EBs, for which we achieve typical precisions in the bolometric flux of ≈3%. Combined with the accurately known bolometric luminosity, the result for each EB is a predicted parallax that is typically precise to 5%. These predicted parallaxes—with typical uncertainties of 200 μas—are 4–5 times more precise than those determined by Hipparcos for 99 of the EBs in our sample, with which we find excellent agreement. There is no evidence among this sample for significant systematics in the Hipparcos parallaxes of the sort that notoriously afflicted the Pleiades measurement. The EBs are distributed over the entire sky, span more than 10 mag in brightness, reach distances of more than 5 kpc, and in many cases our predicted parallaxes should also be more precise than those expected from the Gaia first data release. The EBs studied here can thus serve as empirical, independent benchmarks for these upcoming fundamental parallax measurements.

Journal ArticleDOI
TL;DR: In a previous work as discussed by the authors, we presented the results of the NASA Exoplanet Science Institute Sagan Postdoctoral Fellowship (PSIPF) and the David and Lucile Packard Foundation (DFPF).
Abstract: GO Treasury Program [13467]; NASA [NAS 5-26555]; David and Lucile Packard Foundation; NASA - Space Telescope Science Institute [51362]; NASA Exoplanet Science Institute Sagan Postdoctoral Fellowship

Journal ArticleDOI
TL;DR: In this article, a super-Neptune-sized (5.04(-0.37) + 0.34) R-circle plus) planet transiting K2-33 (2MASS J16101473-1919095), a late-type (M3) pre-main-sequ...
Abstract: We confirm and characterize a close-in (P-orb = 5.425 days), super-Neptune sized (5.04(-0.37)(+0.34) R-circle plus) planet transiting K2-33 (2MASS J16101473-1919095), a late-type (M3) pre-main-sequ ...

Journal ArticleDOI
TL;DR: In this paper, a forced photometry technique was used to define the sources whose fluxes are to be measured in the WISE images, using measured SDSS source positions, star-galaxy classification, and galaxy profiles.
Abstract: © 2016. The American Astronomical Society. All rights reserved.We present photometry of images from the Wide-Field Infrared Survey Explorer (WISE) of over 400 million sources detected by the Sloan Digital Sky Survey (SDSS). We use a forced photometry technique, using measured SDSS source positions, star-galaxy classification, and galaxy profiles to define the sources whose fluxes are to be measured in the WISE images. We perform photometry with The Tractor image modeling code, working on our unWISE coaddds and taking account of the WISE point-spread function and a noise model. The result is a measurement of the flux of each SDSS source in each WISE band. Many sources have little flux in the WISE bands, so often the measurements we report are consistent with zero given our uncertainties. However, for many sources we get 3σ or 4σ measurements; these sources would not be reported by the official WISE pipeline and will not appear in the WISE catalog, yet they can be highly informative for some scientific questions. In addition, these small-signal measurements can be used in stacking analyses at the catalog level. The forced photometry approach has the advantage that we measure a consistent set of sources between SDSS and WISE, taking advantage of the resolution and depth of the SDSS images to interpret the WISE images; objects that are resolved in SDSS but blended together in WISE still have accurate measurements in our photometry. Our results, and the code used to produce them, are publicly available at http://unwise.me.

Journal ArticleDOI
TL;DR: In this article, the authors conducted a systematic search for galaxies that are being stripped of their gas at low-z (z=0.04-0.07) in different environments, selecting galaxies with varying degrees of morphological evidence for stripping.
Abstract: Galaxies that are being stripped of their gas can sometimes be recognized from their optical appearance. Extreme examples of stripped galaxies are the so-called ``jellyfish galaxies'', that exhibit tentacles of debris material with a characteristic jellyfish morphology. We have conducted the first systematic search for galaxies that are being stripped of their gas at low-z (z=0.04-0.07) in different environments, selecting galaxies with varying degrees of morphological evidence for stripping. We have visually inspected B and V-band images and identified 344 candidates in 71 galaxy clusters of the OMEGAWINGS+WINGS sample and 75 candidates in groups and lower mass structures in the PM2GC sample. We present the atlas of stripping candidates and a first analysis of their environment and their basic properties, such as morphologies, star formation rates and galaxy stellar masses. Candidates are found in all clusters and at all clustercentric radii, and their number does not correlate with the cluster velocity dispersion sigma or X-ray luminosity L_X. Interestingly, convincing cases of candidates are also found in groups and lower mass haloes (10^{11}-10^{14} M_{sun}), although the physical mechanism at work needs to be securely identified. All the candidates are disky, have stellar masses ranging from log M/M_{sun} 11.5 and the majority of them form stars at a rate that is on average a factor of 2 higher (2.5 sigma) compared to non-stripped galaxies of similar mass. The few post-starburst and passive candidates have weak stripping evidence. We conclude that the stripping phenomenon is ubiquitous in clusters and could be present even in groups and low mass haloes. Further studies will reveal the physics of the gas stripping and clarify the mechanisms at work.

Journal ArticleDOI
TL;DR: The discovery of DGSAT I, an ultra-diffuse, quenched galaxy located 10fdg4 in projection from the Andromeda galaxy (M31), was reported in this paper.
Abstract: We report the discovery of DGSAT I, an ultra-diffuse, quenched galaxy located 10fdg4 in projection from the Andromeda galaxy (M31). This low-surface brightness galaxy (μV = 24.8 mag arcsec−2), found with a small amateur telescope, appears unresolved in sub-arcsecond archival Subaru/Suprime-Cam images, and hence has been missed by optical surveys relying on resolved star counts, in spite of its relatively large effective radius (Re(V) = 12'') and proximity (15') to the well-known dwarf spheroidal galaxy And II. Its red color (V − I = 1.0), shallow Sersic index (nV = 0.68), and the absence of detectable Hα emission are typical properties of dwarf spheroidal galaxies and suggest that it is mainly composed of old stars. Initially interpreted as an interesting case of an isolated dwarf spheroidal galaxy in the local universe, our radial velocity measurement obtained with the BTA 6 m telescope (Vh = 5450 ± 40 km s−1) shows that this system is an M31-background galaxy associated with the filament of the Pisces-Perseus supercluster. At the distance of this cluster (~78 Mpc), DGSAT I would have an Re ~ 4.7 kpc and MV ~ −16.3. Its properties resemble those of the ultra-diffuse galaxies (UDGs) recently discovered in the Coma cluster. DGSAT I is the first case of these rare UDGs found in this galaxy cluster. Unlike the UDGs associated with the Coma and Virgo clusters, DGSAT I is found in a much lower density environment, which provides a fresh constraint on the formation mechanisms for this intriguing class of galaxy.

Journal ArticleDOI
TL;DR: In this paper, the repeatability, reliability, and accuracy of differential exoplanet eclipse depth measurements made using the InfraRed Array Camera (IRAC) on the Spitzer Space Telescope during the post-cryogenic mission were examined.
Abstract: We examine the repeatability, reliability, and accuracy of differential exoplanet eclipse depth measurements made using the InfraRed Array Camera (IRAC) on the Spitzer Space Telescope during the post-cryogenic mission. We have re-analyzed an existing 4.5 μm data set, consisting of 10 observations of the XO-3b system during secondary eclipse, using seven different techniques for removing correlated noise. We find that, on average, for a given technique, the eclipse depth estimate is repeatable from epoch to epoch to within 156 parts per million (ppm). Most techniques derive eclipse depths that do not vary by more than a factor 3 of the photon noise limit. All methods but one accurately assess their own errors: for these methods, the individual measurement uncertainties are comparable to the scatter in eclipse depths over the 10 epoch sample. To assess the accuracy of the techniques as well as to clarify the difference between instrumental and other sources of measurement error, we have also analyzed a simulated data set of 10 visits to XO-3b, for which the eclipse depth is known. We find that three of the methods (BLISS mapping, Pixel Level Decorrelation, and Independent Component Analysis) obtain results that are within three times the photon limit of the true eclipse depth. When averaged over the 10 epoch ensemble, 5 out of 7 techniques come within 60 ppm of the true value. Spitzer exoplanet data, if obtained following current best practices and reduced using methods such as those described here, can measure repeatable and accurate single eclipse depths, with close to photon-limited results.

Journal ArticleDOI
TL;DR: In this paper, the authors derived parameters and abundances for 1002 stars of spectral types F, G, and K of luminosity class IV and V. The question is: are these stars enhanced or is the Sun somewhat metal-poor relative to these stars? The consistency of the abundances derived here argues for the latter view.
Abstract: Parameters and abundances for 1002 stars of spectral types F, G, and K of luminosity class IV and V have been derived. After culling the sample for rotational velocity and effective temperature, 867 stars remain for discussion. Twenty-eight elements are considered in the analysis. The {\alpha}, iron-peak, and Period 5 transition metal abundances for these stars show a modest enhancement over solar averaging about 0.05 dex. The lanthanides are more abundant averaging about +0.2 dex over solar. The question is: Are these stars enhanced or is the Sun somewhat metal-poor relative to these stars? The consistency of the abundances derived here argues for the latter view. Lithium, carbon, and oxygen abundances have been derived. The stars show the usual lithium astration as a function of mass / temperature. There are more than 100 planet-hosts in the sample, and there is no discernible difference in their lithium content relative to the remaining stars. The carbon and oxygen abundances show the well-known trend of decreasing [x/Fe] ratio with increasing [Fe/H].

Journal ArticleDOI
TL;DR: In this paper, the outer four planets are in a rare dynamical configuration with four interconnected three-body resonances that are librating with few degree amplitudes, and they are assumed to have similar masses but different radii.
Abstract: Kepler has discovered hundreds of systems with multiple transiting exoplanets which hold tremendous potential both individually and collectively for understanding the formation and evolution of planetary systems. Many of these systems consist of multiple small planets with periods less than ~50 days known as Systems with Tightly spaced Inner Planets, or STIPs. One especially intriguing STIP, Kepler-80 (KOI-500), contains five transiting planets: f, d, e, b, and c with periods of 1.0, 3.1, 4.6, 7.1, and 9.5 days, respectively. We provide measurements of transit times and a transit timing variation (TTV) dynamical analysis. We find that TTVs cannot reliably detect eccentricities for this system, though mass estimates are not affected. Restricting the eccentricity to a reasonable range, we infer masses for the outer four planets (d, e, b, and c) to be , , , and Earth masses, respectively. The similar masses but different radii are consistent with terrestrial compositions for d and e and ~2% H/He envelopes for b and c. We confirm that the outer four planets are in a rare dynamical configuration with four interconnected three-body resonances that are librating with few degree amplitudes. We present a formation model that can reproduce the observed configuration by starting with a multi-resonant chain and introducing dissipation. Overall, the information-rich Kepler-80 planets provide an important perspective into exoplanetary systems.

Journal ArticleDOI
TL;DR: In this article, the authors detect the Doppler signal of Kepler-21b with a RV semiamplitude K = 2.00 ± 0.04 R and an orbital period of about 2.7857 days.
Abstract: HD 179070, aka Kepler-21, is a V = 8.25 F6IV star and the brightest exoplanet host discovered by Kepler. An early detailed analysis by Howell et al. of the first 13 months (Q0–Q5) of Kepler light curves revealed transits of a planetary companion, Kepler-21b, with a radius of about 1.60 ± 0.04 R⊕ and an orbital period of about 2.7857 days. However, they could not determine the mass of the planet from the initial radial velocity (RV) observations with Keck-HIRES, and were only able to impose a 2σ upper limit of 10 M⊕. Here, we present results from the analysis of 82 new RV observations of this system obtained with HARPS-N, together with the existing 14 HIRES data points. We detect the Doppler signal of Kepler-21b with a RV semiamplitude K = 2.00 ± 0.65 m s^(-1), which corresponds to a planetary mass of 5.1 ± 1.7 M⊕. We also measure an improved radius for the planet of 1.639 +0.019/−0.015 R⊕, in agreement with the radius reported by Howell et al. We conclude that Kepler-21b, with a density of 6.4 ± 2.1 g cm^(-3), belongs to the population of small, ≾6 M⊕ planets with iron and magnesium silicate interiors, which have lost the majority of their envelope volatiles via stellar winds or gravitational escape. The RV analysis presented in this paper serves as an example of the type of analysis that will be necessary to confirm the masses of TESS small planet candidates.


Journal ArticleDOI
TL;DR: In this article, a review of the most widely used correlated-noise estimators in the exoplanet field, the time-averaging, residual-permutation, and wavelet-likelihood methods, is presented.
Abstract: Time-correlated noise is a significant source of uncertainty when modeling exoplanet light-curve data. A correct assessment of correlated noise is fundamental to determine the true statistical significance of our findings. Here we review three of the most widely used correlated-noise estimators in the exoplanet field, the time-averaging, residual-permutation, and wavelet-likelihood methods. We argue that the residual-permutation method is unsound in estimating the uncertainty of parameter estimates. We thus recommend to refrain from this method altogether. We characterize the behavior of the time averaging's rms-vs.-bin-size curves at bin sizes similar to the total observation duration, which may lead to underestimated uncertainties. For the wavelet-likelihood method, we note errors in the published equations and provide a list of corrections. We further assess the performance of these techniques by injecting and retrieving eclipse signals into synthetic and real Spitzer light curves, analyzing the results in terms of the relative-accuracy and coverage-fraction statistics. Both the time-averaging and wavelet-likelihood methods significantly improve the estimate of the eclipse depth over a white-noise analysis (a Markov-chain Monte Carlo exploration assuming uncorrelated noise). However, the corrections are not perfect, when retrieving the eclipse depth from Spitzer datasets, these methods covered the true (injected) depth within the 68\% credible region in only $\sim$45--65\% of the trials. Lastly, we present our open-source model-fitting tool, Multi-Core Markov-Chain Monte Carlo ({MC$^3$}). This package uses Bayesian statistics to estimate the best-fitting values and the credible regions for the parameters for a (user-provided) model. {MC$^3$} is a Python/C code, available at this https URL.

Journal ArticleDOI
TL;DR: The results from the cross-calibration campaigns in 2012 on 3C 273 and in 2013 on PKS 2155-304 between the then active X-ray observatories Chandra, NuSTAR, Suzaku, Swift, and XMM-Newton are presented in this article.
Abstract: On behalf of the International Astronomical Consortium for High Energy Calibration, we present results from the cross-calibration campaigns in 2012 on 3C 273 and in 2013 on PKS 2155-304 between the then active X-ray observatories Chandra, NuSTAR, Suzaku, Swift, and XMM-Newton. We compare measured fluxes between instrument pairs in two energy bands, 1–5 keV and 3–7 keV, and calculate an average cross-normalization constant for each energy range. We review known cross-calibration features and provide a series of tables and figures to be used for evaluating cross-normalization constants obtained from other observations with the above mentioned observatories.

Journal ArticleDOI
TL;DR: In this paper, the authors presented a Wide-Field Infrared Survey Explorer (WISE) image of the Milky Way bulge, produced by downsampling the publicly available "unWISE" coadds.
Abstract: The Milky Way bulge has a boxy/peanut morphology and an X-shaped structure. This X-shape has been revealed by the "split in the red clump" from star counts along the line of sight toward the bulge, measured from photometric surveys. This boxy, X-shaped bulge morphology is not unique to the Milky Way and such bulges are observed in other barred spiral galaxies. N-body simulations show that boxy and X-shaped bulges are formed from the disk via dynamical instabilities. It has also been proposed that the Milky Way bulge is not X-shaped, but rather, the apparent split in the red clump stars is a consequence of different stellar populations, in an old classical spheroidal bulge. We present a Wide-Field Infrared Survey Explorer (WISE) image of the Milky Way bulge, produced by downsampling the publicly available "unWISE" coadds. The WISE image of the Milky Way bulge shows that the X-shaped nature of the Milky Way bulge is self-evident and irrefutable. The X-shape morphology of the bulge in itself and the fraction of bulge stars that comprise orbits within this structure has important implications for the formation history of the Milky Way, and, given the ubiquity of boxy X-shaped bulges, spiral galaxies in general.

Journal ArticleDOI
TL;DR: The final Kepler Data Processing Pipeline search for transiting planet signals in the full 17-quarter primary mission data set was reported in this article, with a recovery rate of 99.8%.
Abstract: We present results of the final Kepler Data Processing Pipeline search for transiting planet signals in the full 17-quarter primary mission data set. The search includes a total of 198,709 stellar targets, of which 112,046 were observed in all 17 quarters and 86,663 in fewer than 17 quarters. We report on 17,230 targets for which at least one transit signature is identified that meets the specified detection criteria: periodicity, minimum of three observed transit events, detection statistic (i.e., signal-to-noise ratio) in excess of the search threshold, and passing grade on three statistical transit consistency tests. Light curves for which a transit signal is identified are iteratively searched for additional signatures after a limb-darkened transiting planet model is fitted to the data and transit events are removed. The search for additional planets adds 16,802 transit signals for a total of 34,032; this far exceeds the number of transit signatures identified in prior pipeline runs. There was a strategic emphasis on completeness over reliability for the final Kepler transit search. A comparison of the transit signals against a set of 3402 well-established, high-quality Kepler Objects of Interest yields a recovery rate of 99.8%. The high recovery rate must be weighed against a large number of false-alarm detections. We examine characteristics of the planet population implied by the transiting planet model fits with an emphasis on detections that would represent small planets orbiting in the habitable zone of their host stars.

Journal ArticleDOI
TL;DR: In this article, the first transiting planet was discovered in the intermediate-age (800 Myr) Beehive cluster (Praesepe) by using the Kepler spacecraft.
Abstract: Open clusters have been the focus of several exoplanet surveys, but only a few planets have so far been discovered. The Kepler spacecraft revealed an abundance of small planets around small cool stars, therefore, such cluster members are prime targets for exoplanet transit searches. Kepler's new mission, K2, is targeting several open clusters and star-forming regions around the ecliptic to search for transiting planets around their low-mass constituents. Here, we report the discovery of the first transiting planet in the intermediate-age (800 Myr) Beehive cluster (Praesepe). K2-95 is a faint (K_p = 15.5 mag) M3.0 ± 0.5 dwarf from K2's Campaign 5 with an effective temperature of 3471 ± 124 K, approximately solar metallicity and a radius of 0.402 ± 0.050 R⊙. We detected a transiting planet with a radius of 3.47^(+0.78)_(-0.53) R⊕ and an orbital period of 10.134 days. We combined photometry, medium/high-resolution spectroscopy, adaptive optics/speckle imaging, and archival survey images to rule out any false-positive detection scenarios, validate the planet, and further characterize the system. The planet's radius is very unusual as M-dwarf field stars rarely have Neptune-sized transiting planets. The comparatively large radius of K2-95b is consistent with the other recently discovered cluster planets K2-25b (Hyades) and K2-33b (Upper Scorpius), indicating systematic differences in their evolutionary states or formation. These discoveries from K2 provide a snapshot of planet formation and evolution in cluster environments and thus make excellent laboratories to test differences between field-star and cluster planet populations.