Showing papers by "European Southern Observatory published in 2018"
Bela Abolfathi1, D. S. Aguado2, Gabriela Aguilar3, Carlos Allende Prieto2 +361 more•Institutions (94)
TL;DR: SDSS-IV is the fourth generation of the Sloan Digital Sky Survey and has been in operation since 2014 July. as discussed by the authors describes the second data release from this phase, and the 14th from SDSS overall (making this Data Release Fourteen or DR14).
Abstract: The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in operation since 2014 July. This paper describes the second data release from this phase, and the 14th from SDSS overall (making this Data Release Fourteen or DR14). This release makes the data taken by SDSS-IV in its first two years of operation (2014-2016 July) public. Like all previous SDSS releases, DR14 is cumulative, including the most recent reductions and calibrations of all data taken by SDSS since the first phase began operations in 2000. New in DR14 is the first public release of data from the extended Baryon Oscillation Spectroscopic Survey; the first data from the second phase of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2), including stellar parameter estimates from an innovative data-driven machine-learning algorithm known as "The Cannon"; and almost twice as many data cubes from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous release (N = 2812 in total). This paper describes the location and format of the publicly available data from the SDSS-IV surveys. We provide references to the important technical papers describing how these data have been taken (both targeting and observation details) and processed for scientific use. The SDSS web site (www.sdss.org) has been updated for this release and provides links to data downloads, as well as tutorials and examples of data use. SDSS-IV is planning to continue to collect astronomical data until 2020 and will be followed by SDSS-V.
965 citations
European Southern Observatory1, University of Lisbon2, University of Porto3, Max Planck Society4, University of Grenoble5, University of Geneva6, Paris Diderot University7, Leiden University8, University of Cologne9, Dublin Institute for Advanced Studies10, University of California, Berkeley11, Space Telescope Science Institute12
TL;DR: Eisenhauer et al. as mentioned in this paper detect the combined gravitational redshift and relativistic transverse Doppler effect for S2 of z = Δλ / λ ≈ 200 km s−1/c with different statistical analysis methods.
Abstract: The highly elliptical, 16-year-period orbit of the star S2 around the massive black hole candidate Sgr A✻ is a sensitive probe of the gravitational field in the Galactic centre. Near pericentre at 120 AU ≈ 1400 Schwarzschild radii, the star has an orbital speed of ≈7650 km s−1, such that the first-order effects of Special and General Relativity have now become detectable with current capabilities. Over the past 26 years, we have monitored the radial velocity and motion on the sky of S2, mainly with the SINFONI and NACO adaptive optics instruments on the ESO Very Large Telescope, and since 2016 and leading up to the pericentre approach in May 2018, with the four-telescope interferometric beam-combiner instrument GRAVITY. From data up to and including pericentre, we robustly detect the combined gravitational redshift and relativistic transverse Doppler effect for S2 of z = Δλ / λ ≈ 200 km s−1/c with different statistical analysis methods. When parameterising the post-Newtonian contribution from these effects by a factor f , with f = 0 and f = 1 corresponding to the Newtonian and general relativistic limits, respectively, we find from posterior fitting with different weighting schemes f = 0.90 ± 0.09|stat ± 0.15|sys. The S2 data are inconsistent with pure Newtonian dynamics.Key words: Galaxy: center / gravitation / black hole physics⋆ This paper is dedicated to Tal Alexander, who passed away about a week before the pericentre approach of S2.⋆⋆ GRAVITY is developed in a collaboration by the Max Planck Institute for extraterrestrial Physics, LESIA of Paris Observatory/CNRS/Sorbonne Universite/Univ. Paris Diderot and IPAG of Universite Grenoble Alpes/CNRS, the Max Planck Institute for Astronomy, the University of Cologne, the CENTRA – Centro de Astrofisica e Gravitacao, and the European Southern Observatory.⋆⋆⋆ Corresponding author: F. Eisenhauer e-mail: eisenhau@mpe.mpg.de
693 citations
TL;DR: In this article, a selected sample of 50 long-period, low-extinction Milky Way Cepheids measured on the same WFC3 F555W, F814W, and F160W-band photometric system as extragalactic Cepsheids in SN Ia hosts were observed with the optical and near-infrared to mitigate saturation and reduce pixel-to-pixel calibration errors.
Abstract: We present HST photometry of a selected sample of 50 long-period, low-extinction Milky Way Cepheids measured on the same WFC3 F555W, F814W, and F160W-band photometric system as extragalactic Cepheids in SN Ia hosts. These bright Cepheids were observed with the WFC3 spatial scanning mode in the optical and near-infrared to mitigate saturation and reduce pixel-to-pixel calibration errors to reach a mean photometric error of 5 millimags per observation. We use the new Gaia DR2 parallaxes and HST photometry to simultaneously constrain the cosmic distance scale and to measure the DR2 parallax zeropoint offset appropriate for Cepheids. We find a value for the zeropoint offset of -46 +/- 13 muas or +/- 6 muas for a fixed distance scale, higher than found from quasars, as expected, for these brighter and redder sources. The precision of the distance scale from DR2 has been reduced by a factor of 2.5 due to the need to independently determine the parallax offset. The best fit distance scale is 1.006 +/- 0.033, relative to the scale from Riess et al 2016 with H0=73.24 km/s/Mpc used to predict the parallaxes photometrically, and is inconsistent with the scale needed to match the Planck 2016 CMB data combined with LCDM at the 2.9 sigma confidence level (99.6%). At 96.5% confidence we find that the formal DR2 errors may be underestimated as indicated. We identify additional error associated with the use of augmented Cepheid samples utilizing ground-based photometry and discuss their likely origins. Including the DR2 parallaxes with all prior distance ladder data raises the current tension between the late and early Universe route to the Hubble constant to 3.8 sigma (99.99 %). With the final expected precision from Gaia, the sample of 50 Cepheids with HST photometry will limit to 0.5% the contribution of the first rung of the distance ladder to the uncertainty in the Hubble constant.
670 citations
TL;DR: In this paper, the authors describe the processing of the Gaia DR2 data, and describe the criteria used to select the sample published in Gaia DR 2, and explore the data set to assess its quality.
Abstract: Context. The Gaia spacecraft of the European Space Agency (ESA) has been securing observations of solar system objects (SSOs) since the beginning of its operations. Data Release 2 (DR2) contains the observations of a selected sample of 14,099 SSOs. These asteroids have been already identified and have been numbered by the Minor Planet Center repository. Positions are provided for each Gaia observation at CCD level. As additional information, complementary to astrometry, the apparent brightness of SSOs in the unfiltered G band is also provided for selected observations.Aims. We explain the processing of SSO data, and describe the criteria we used to select the sample published in Gaia DR2. We then explore the data set to assess its quality.Methods. To exploit the main data product for the solar system in Gaia DR2, which is the epoch astrometry of asteroids, it is necessary to take into account the unusual properties of the uncertainty, as the position information is nearly one-dimensional. When this aspect is handled appropriately, an orbit fit can be obtained with post-fit residuals that are overall consistent with the a-priori error model that was used to define individual values of the astrometric uncertainty. The role of both random and systematic errors is described. The distribution of residuals allowed us to identify possible contaminants in the data set (such as stars). Photometry in the G band was compared to computed values from reference asteroid shapes and to the flux registered at the corresponding epochs by the red and blue photometers (RP and BP).Results. The overall astrometric performance is close to the expectations, with an optimal range of brightness G ~ 12 − 17. In this range, the typical transit-level accuracy is well below 1 mas. For fainter asteroids, the growing photon noise deteriorates the performance. Asteroids brighter than G ~ 12 are affected by a lower performance of the processing of their signals. The dramatic improvement brought by Gaia DR2 astrometry of SSOs is demonstrated by comparisons to the archive data and by preliminary tests on the detection of subtle non-gravitational effects.
584 citations
TL;DR: In this paper, the second data release of the Gaia mission and its power for constraining many different aspects of the dynamics of the satellites of the Milky Way is demonstrated. But the accuracy of the errors, statistical and systematic, are relatively well understood.
Abstract: Context. Aims: The goal of this paper is to demonstrate the outstanding quality of the second data release of the Gaia mission and its power for constraining many different aspects of the dynamics of the satellites of the Milky Way. We focus here on determining the proper motions of 75 Galactic globular clusters, nine dwarf spheroidal galaxies, one ultra-faint system, and the Large and Small Magellanic Clouds. Methods: Using data extracted from the Gaia archive, we derived the proper motions and parallaxes for these systems, as well as their uncertainties. We demonstrate that the errors, statistical and systematic, are relatively well understood. We integrated the orbits of these objects in three different Galactic potentials, and characterised their properties. We present the derived proper motions, space velocities, and characteristic orbital parameters in various tables to facilitate their use by the astronomical community. Results: Our limited and straightforward analyses have allowed us for example to (i) determine absolute and very precise proper motions for globular clusters; (ii) detect clear rotation signatures in the proper motions of at least five globular clusters; (iii) show that the satellites of the Milky Way are all on high-inclination orbits, but that they do not share a single plane of motion; (iv) derive a lower limit for the mass of the Milky Way of 9.1-2.6+6.2 × 1011 M⊙ based on the assumption that the Leo I dwarf spheroidal is bound; (v) derive a rotation curve for the Large Magellanic Cloud based solely on proper motions that is competitive with line-of-sight velocity curves, now using many orders of magnitude more sources; and (vi) unveil the dynamical effect of the bar on the motions of stars in the Large Magellanic Cloud. Conclusions: All these results highlight the incredible power of the Gaia astrometric mission, and in particular of its second data release.
581 citations
Max Planck Society1, University of Chile2, University of Grenoble3, European Southern Observatory4, Leiden University5, University of Oxford6, Paris Diderot University7, INAF8, École normale supérieure de Lyon9, Aix-Marseille University10, University of Tübingen11, University of Bern12, Hungarian Academy of Sciences13, ETH Zurich14, Diego Portales University15, Ludwig Maximilian University of Munich16, Kavli Institute for Theoretical Physics17, California Institute of Technology18, Rice University19, Stockholm University20, University of Cambridge21, Centre national de la recherche scientifique22, Valparaiso University23, University of Arizona24, Monash University, Clayton campus25, University of Geneva26, University of Hawaii at Manoa27, University of Atacama28, Heidelberg University29, University of Michigan30
TL;DR: In this article, the authors detect a point source within the gap of the transition disk at about 195 mas (~22 au) projected separation and detect a signal from an inner disk component.
Abstract: Context. Young circumstellar disks are the birthplaces of planets. Their study is of prime interest to understand the physical and chemical conditions under which planet formation takes place. Only very few detections of planet candidates within these disks exist, and most of them are currently suspected to be disk features.Aims. In this context, the transition disk around the young star PDS 70 is of particular interest, due to its large gap identified in previous observations, indicative of ongoing planet formation. We aim to search for the presence of an embedded young planet and search for disk structures that may be the result of disk–planet interactions and other evolutionary processes.Methods. We analyse new and archival near-infrared images of the transition disk PDS 70 obtained with the VLT/SPHERE, VLT/NaCo, and Gemini/NICI instruments in polarimetric differential imaging and angular differential imaging modes.Results. We detect a point source within the gap of the disk at about 195 mas (~22 au) projected separation. The detection is confirmed at five different epochs, in three filter bands and using different instruments. The astrometry results in an object of bound nature, with high significance. The comparison of the measured magnitudes and colours to evolutionary tracks suggests that the detection is a companion of planetary mass. The luminosity of the detected object is consistent with that of an L-type dwarf, but its IR colours are redder, possibly indicating the presence of warm surrounding material. Further, we confirm the detection of a large gap of ~54 au in size within the disk in our scattered light images, and detect a signal from an inner disk component. We find that its spatial extent is very likely smaller than ~17 au in radius, and its position angle is consistent with that of the outer disk. The images of the outer disk show evidence of a complex azimuthal brightness distribution which is different at different wavelengths and may in part be explained by Rayleigh scattering from very small grains.Conclusions. The detection of a young protoplanet within the gap of the transition disk around PDS 70 opens the door to a so far observationally unexplored parameter space of planetary formation and evolution. Future observations of this system at different wavelengths and continuing astrometry will allow us to test theoretical predictions regarding planet–disk interactions, planetary atmospheres, and evolutionary models.
497 citations
Peking University1, University of Arizona2, Leiden University3, University of Leicester4, University of Cambridge5, University of Milan6, Vassar College7, Smith College8, University of Grenoble9, University of Victoria10, Max Planck Society11, Chinese Academy of Sciences12, Rice University13, University of Paris14, European Southern Observatory15, University of Chicago16, INAF17, Space Telescope Science Institute18, Ames Research Center19
TL;DR: In this article, the authors identify the most frequently revealed substructure in ALMA dust observations of protoplanetary disks, and measure their properties to investigate how they form, including axisymmetric rings and gaps.
Abstract: Rings are the most frequently revealed substructure in ALMA dust observations of protoplanetary disks, but their origin is still hotly debated. In this paper, we identify dust substructures in 12 disks and measure their properties to investigate how they form. This subsample of disks is selected from a high-resolution ($\sim0.12''$) ALMA 1.33 mm survey of 32 disks in the Taurus star-forming region, which was designed to cover a wide range of sub-mm brightness and to be unbiased to previously known substructures. While axisymmetric rings and gaps are common within our sample, spiral patterns and high contrast azimuthal asymmetries are not detected. Fits of disk models to the visibilities lead to estimates of the location and shape of gaps and rings, the flux in each disk component, and the size of the disk. The dust substructures occur across a wide range of stellar mass and disk brightness. Disks with multiple rings tend to be more massive and more extended. The correlation between gap locations and widths, the intensity contrast between rings and gaps, and the separations of rings and gaps could all be explained if most gaps are opened by low-mass planets (super-Earths and Neptunes) in the condition of low disk turbulence ($\alpha=10^{-4}$). The gap locations are not well correlated with the expected locations of CO and N$_2$ ice lines, so condensation fronts are unlikely to be a universal mechanism to create gaps and rings, though they may play a role in some cases.
395 citations
TL;DR: In this paper, the authors determined masses, stellar mass functions, and structural parameters of 112 Milky Way globular clusters by fitting a large set of N-body simulations to their velocity dispersion and surface density profiles.
Abstract: We have determined masses, stellar mass functions, and structural parameters of 112 Milky Way globular clusters by fitting a large set of N-body simulations to their velocity dispersion and surface density profiles. The velocity dispersion profiles were calculated based on a combination of more than 15000 high-precision radial velocities which we derived from archival ESO/VLT and Keck spectra together with similar to 20000 published radial velocities from the literature. Our fits also include the stellar mass functions of the globular clusters, which are available for 47 clusters in our sample, allowing us to self-consistently take the effects of mass segregation and ongoing cluster dissolution into account. We confirm the strong correlation between the global mass functions of globular clusters and their relaxation times recently found by Sollima & Baumgardt (2017). We also find a correlation of the escape velocity from the centre of a globular cluster and the fraction of first generation stars (FG) in the cluster recently derived for 57 globular clusters by Milone et al. (2017), but no correlation between the FG star fraction and the global mass function of a globular cluster. This could indicate that the ability of a globular cluster to keep the wind ejecta from the polluting star(s) is the crucial parameter determining the presence and fraction of second-generation stars and not its later dynamical mass loss.
346 citations
TL;DR: In this article, the position centroids exhibit clockwise looped motion on the sky, on scales of typically 150 μ as over a few tens of minutes, corresponding to about 30% the speed of light.
Abstract: We report the detection of continuous positional and polarization changes of the compact source SgrA* in high states (“flares”) of its variable near-infrared emission with the near-infrared GRAVITY-Very Large Telescope Interferometer (VLTI) beam-combining instrument. In three prominent bright flares, the position centroids exhibit clockwise looped motion on the sky, on scales of typically 150 μ as over a few tens of minutes, corresponding to about 30% the speed of light. At the same time, the flares exhibit continuous rotation of the polarization angle, with about the same 45(±15) min period as that of the centroid motions. Modelling with relativistic ray tracing shows that these findings are all consistent with a near face-on, circular orbit of a compact polarized “hot spot” of infrared synchrotron emission at approximately six to ten times the gravitational radius of a black hole of 4 million solar masses. This corresponds to the region just outside the innermost, stable, prograde circular orbit (ISCO) of a Schwarzschild–Kerr black hole, or near the retrograde ISCO of a highly spun-up Kerr hole. The polarization signature is consistent with orbital motion in a strong poloidal magnetic field.
300 citations
Osaka Sangyo University1, University of Toulouse2, University College London3, Uppsala University4, Johns Hopkins University5, Nagoya University6, Pontifical Catholic University of Chile7, Millennium Institute8, Space Science Institute9, University of Tokyo10, European Southern Observatory11, Graduate University for Advanced Studies12, Institute for the Physics and Mathematics of the Universe13, Heidelberg University14, Osaka University15, The Open University of Japan16
TL;DR: Spectroscopic observations of MACS1149-JD16, a gravitationally lensed galaxy observed when the Universe was less than four per cent of its present age, reveal that star formation began at a redshift of about 15, around 250 million years after the Big Bang.
Abstract: A fundamental quest of modern astronomy is to locate the earliest galaxies and study how they influenced the intergalactic medium a few hundred million years after the Big Bang1–3. The abundance of star-forming galaxies is known to decline4,5 from redshifts of about 6 to 10, but a key question is the extent of star formation at even earlier times, corresponding to the period when the first galaxies might have emerged. Here we report spectroscopic observations of MACS1149-JD16, a gravitationally lensed galaxy observed when the Universe was less than four per cent of its present age. We detect an emission line of doubly ionized oxygen at a redshift of 9.1096 ± 0.0006, with an uncertainty of one standard deviation. This precisely determined redshift indicates that the red rest-frame optical colour arises from a dominant stellar component that formed about 250 million years after the Big Bang, corresponding to a redshift of about 15. Our results indicate that it may be possible to detect such early episodes of star formation in similar galaxies with future telescopes. Observation of the emission line of doubly ionized oxygen at a redshift of 9.1096 reveals that star formation began at a redshift of about 15, around 250 million years after the Big Bang.
271 citations
TL;DR: In this paper, the authors focus on outflows traced by optical and CO emission lines, and highlight the observational uncertainties involved and the assumptions required when deriving kinetic coupling efficiencies (that is, outflow kinetic power as a fraction of AGN luminosity) from typical observations.
Abstract: It is twenty years since the seminal works by Magorrian and co-authors and by Silk and Rees, which, along with other related work, ignited an explosion of publications connecting active galactic nucleus (AGN)-driven outflows to galaxy evolution. With a surge in observations of AGN outflows, studies are attempting to test AGN feedback models directly using the outflow properties. With a focus on outflows traced by optical and CO emission lines, we discuss significant challenges that greatly complicate this task, from both an observational and theoretical perspective. We highlight the observational uncertainties involved and the assumptions required when deriving kinetic coupling efficiencies (that is, outflow kinetic power as a fraction of AGN luminosity) from typical observations. Based on recent models we demonstrate that extreme caution should be taken when comparing observationally derived kinetic coupling efficiencies to coupling efficiencies from fiducial feedback models.
Ohio State University1, Max Planck Society2, University of Alberta3, University of Toulouse4, Hoffmann-La Roche5, Heidelberg University6, Carnegie Institution for Science7, University of Chile8, University of Maryland, College Park9, Australian National University10, ASTRON11, European Southern Observatory12
TL;DR: The European Research Council (ERC) under European Union's Horizon 2020 research and innovation program via the ERC Starting Grant MUSTANG as discussed by the authors has been used for the first time in 2018.
Abstract: INSU/CNRS (France)
MPG (Germany)
IGN (Spain)
National Science Foundation
1615105
1615109
1653300
Natural Sciences and Engineering Research Council of Canada (NSERC)
RGPIN-2017-03987
Centre National d'Etudes Spatiales (CNES)
German Research Foundation (DFG)
KR4801/1-1
European Research Council (ERC) under European Union's Horizon 2020 research and innovation program via the ERC Starting Grant MUSTANG
714907
CONICYT/FONDECYT, Programa de Iniciacion
Folio 11150220
Programme National "Physique et Chimie du Milieu Interstellaire" (PCMI) of CNRS/INSU
INC/INP
CEA
CNES
Spanish MINECO
ESP2015-68964
AYA2016-79006
European Research Council (ERC) under the European Unions
694343
University of Arizona1, Harvard University2, University of Illinois at Urbana–Champaign3, Diego Portales University4, Massachusetts Institute of Technology5, Aix-Marseille University6, University of Missouri–Kansas City7, University of Cambridge8, Dalhousie University9, European Southern Observatory10, University of Chicago11, Saint Mary's University12, University of California, Davis13, University of Florida14, University College London15, Stanford University16, McMaster University17, University of California, Los Angeles18, National Radio Astronomy Observatory19, Max Planck Society20
TL;DR: Observations of a far-infrared-luminous object at redshift 6.900 (less than 800 million years after the Big Bang) that was discovered in a wide-field survey suggest the presence of a dark-matter halo with a mass of more than 100 billion solar masses, making it among the rarest dark- Matter haloes that should exist in the Universe at this epoch.
Abstract: According to the current understanding of cosmic structure formation, the precursors of the most massive structures in the Universe began to form shortly after the Big Bang, in regions corresponding to the largest fluctuations in the cosmic density field. Observing these structures during their period of active growth and assembly-the first few hundred million years of the Universe-is challenging because it requires surveys that are sensitive enough to detect the distant galaxies that act as signposts for these structures and wide enough to capture the rarest objects. As a result, very few such objects have been detected so far. Here we report observations of a far-infrared-luminous object at redshift 6.900 (less than 800 million years after the Big Bang) that was discovered in a wide-field survey. High-resolution imaging shows it to be a pair of extremely massive star-forming galaxies. The larger is forming stars at a rate of 2,900 solar masses per year, contains 270 billion solar masses of gas and 2.5 billion solar masses of dust, and is more massive than any other known object at a redshift of more than 6. Its rapid star formation is probably triggered by its companion galaxy at a projected separation of 8 kiloparsecs. This merging companion hosts 35 billion solar masses of stars and has a star-formation rate of 540 solar masses per year, but has an order of magnitude less gas and dust than its neighbour and physical conditions akin to those observed in lower-metallicity galaxies in the nearby Universe. These objects suggest the presence of a dark-matter halo with a mass of more than 100 billion solar masses, making it among the rarest dark-matter haloes that should exist in the Universe at this epoch.
Ansgar Reiners1, Mathias Zechmeister1, Jose A. Caballero2, Ignasi Ribas3 +177 more•Institutions (18)
TL;DR: In this article, the CARMENES radial velocity (RV) survey is observing 324 M dwarfs to search for any orbiting planets and the authors present an atlas of high resolution M-dwarf spectra and compare the spectra to atmospheric models.
Abstract: The CARMENES radial velocity (RV) survey is observing 324 M dwarfs to search for any orbiting planets. In this paper, we present the survey sample by publishing one CARMENES spectrum for each M dwarf. These spectra cover the wavelength range 520–1710 nm at a resolution of at least R >80 000, and we measure its RV, Hα emission, and projected rotation velocity. We present an atlas of high-resolution M-dwarf spectra and compare the spectra to atmospheric models. To quantify the RV precision that can be achieved in low-mass stars over the CARMENES wavelength range, we analyze our empirical information on the RV precision from more than 6500 observations. We compare our high-resolution M-dwarf spectra to atmospheric models where we determine the spectroscopic RV information content, Q , and signal-to-noise ratio. We find that for all M-type dwarfs, the highest RV precision can be reached in the wavelength range 700–900 nm. Observations at longer wavelengths are equally precise only at the very latest spectral types (M8 and M9). We demonstrate that in this spectroscopic range, the large amount of absorption features compensates for the intrinsic faintness of an M7 star. To reach an RV precision of 1 m s−1 in very low mass M dwarfs at longer wavelengths likely requires the use of a 10 m class telescope. For spectral types M6 and earlier, the combination of a red visual and a near-infrared spectrograph is ideal to search for low-mass planets and to distinguish between planets and stellar variability. At a 4 m class telescope, an instrument like CARMENES has the potential to push the RV precision well below the typical jitter level of 3–4 m s−1 .
University of Tokyo1, Institute for the Physics and Mathematics of the Universe2, Carnegie Learning3, Mahidol University4, University of Saint Mary5, National Research Council6, University of Lyon7, Tohoku University8, University of Geneva9, Graduate University for Advanced Studies10, Academia Sinica11, Ehime University12, European Southern Observatory13, The Open University of Japan14
TL;DR: In this paper, the authors studied the UV luminosity functions (LFs) at 4, 5, 6, and 7$ on the 100 deg$^2$ sky of the Hyper Suprime-Cam (HSC) strategic program (SSP).
Abstract: We study the UV luminosity functions (LFs) at $z\\sim 4$, $5$, $6,$ and $7$ based on the deep large-area optical images taken by the Hyper Suprime-Cam (HSC) Subaru strategic program (SSP). On the 100 deg$^2$ sky of the HSC SSP data available to date, we make enormous samples consisting of a total of 579,565 dropout candidates at $z\\sim 4-7$ by the standard color selection technique, 358 out of which are spectroscopically confirmed by our follow-up spectroscopy and other studies. We obtain UV LFs at $z \\sim 4-7$ that span a very wide UV luminosity range of $\\sim 0.002 - 100 \\, L_{\\rm UV}^\\ast$ ($-26 2 \\sigma$ significance, and require either double power-law functions or modified Schechter functions that consider a magnification bias due to gravitational lensing.
University of California, Berkeley1, University of Cambridge2, University of Warwick3, Rutgers University4, University of Arizona5, Michigan State University6, University of California, Santa Cruz7, University College Dublin8, University of Warsaw9, Harvard University10, Queen's University Belfast11, University of Pittsburgh12, University of Barcelona13, European Southern Observatory14, University of Kiel15, Heidelberg Institute for Theoretical Studies16, Heidelberg University17, North Carolina State University18, University of Amsterdam19, University of Alabama20, Space Telescope Science Institute21
TL;DR: In this article, a search for hypervelocity runaway double white dwarf (WD) binaries undergoing unstable mass transfer has been performed using Gaia's second data release, followed up with ground-based instruments.
Abstract: Double detonations in double white dwarf (WD) binaries undergoing unstable mass transfer have emerged in recent years as one of the most promising Type Ia supernova (SN Ia) progenitor scenarios. One potential outcome of this "dynamically driven double-degenerate double-detonation" (D6) scenario is that the companion WD survives the explosion and is flung away with a velocity equal to its >1000 km s−1 pre-SN orbital velocity. We perform a search for these hypervelocity runaway WDs using Gaia's second data release. In this paper, we discuss seven candidates followed up with ground-based instruments. Three sources are likely to be some of the fastest known stars in the Milky Way, with total Galactocentric velocities between 1000 and 3000 km s−1, and are consistent with having previously been companion WDs in pre-SN Ia systems. However, although the radial velocity of one of the stars is >1000 km s−1, the radial velocities of the other two stars are puzzlingly consistent with 0. The combined five-parameter astrometric solutions from Gaia and radial velocities from follow-up spectra yield tentative 6D confirmation of the D6 scenario. The past position of one of these stars places it within a faint, old SN remnant, further strengthening the interpretation of these candidates as hypervelocity runaways from binary systems that underwent SNe Ia.
Max Planck Society1, University of Grenoble2, University of Chile3, Paris Diderot University4, University of Oxford5, Space Telescope Science Institute6, University of Geneva7, INAF8, Aix-Marseille University9, Université Paris-Saclay10, ETH Zurich11, Stockholm University12, École normale supérieure de Lyon13, University of Atacama14, University of Michigan15, Leiden University16, University of Bern17, Hungarian Academy of Sciences18, European Southern Observatory19, Diego Portales University20
TL;DR: In this article, the spectral properties of PDS 70 b have been characterized using spectrophotometry of the entire near-infrared range (0.96-3.8 μ m).
Abstract: Context . The observation of planets in their formation stage is a crucial but very challenging step in understanding when, how, and where planets form. PDS 70 is a young pre-main sequence star surrounded by a transition disk, in the gap of which a planetary-mass companion has recently been discovered. This discovery represents the first robust direct detection of such a young planet, possibly still at the stage of formation.Aims . We aim to characterize the orbital and atmospheric properties of PDS 70 b, which was first identified on May 2015 in the course of the SHINE survey with SPHERE, the extreme adaptive-optics instrument at the VLT.Methods . We obtained new deep SPHERE/IRDIS imaging and SPHERE/IFS spectroscopic observations of PDS 70 b. The astrometric baseline now covers 6 yr, which allowed us to perform an orbital analysis. For the first time, we present spectrophotometry of the young planet which covers almost the entire near-infrared range (0.96–3.8 μ m). We use different atmospheric models covering a large parameter space in temperature, log g , chemical composition, and cloud properties to characterize the properties of the atmosphere of PDS 70 b.Results . PDS 70 b is most likely orbiting the star on a circular and disk coplanar orbit at ~22 au inside the gap of the disk. We find a range of models that can describe the spectrophotometric data reasonably well in the temperature range 1000–1600 K and log g no larger than 3.5 dex. The planet radius covers a relatively large range between 1.4 and 3.7 R J with the larger radii being higher than expected from planet evolution models for the age of the planet of 5.4 Myr.Conclusions . This study provides a comprehensive data set on the orbital motion of PDS 70 b, indicating a circular orbit and a motion coplanar with the disk. The first detailed spectral energy distribution of PDS 70 b indicates a temperature typical of young giant planets. The detailed atmospheric analysis indicates that a circumplanetary disk may contribute to the total planetflux.
TL;DR: In this paper, the authors presented the results from a survey of 25 Galactic globular clusters with the MUSE integral-field spectrograph, which provided unique multiplex capabilities in crowded stellar fields and allowed them to acquire samples of up to 20 000 stars within the half-light radius of each cluster.
Abstract: This is the first of a series of papers presenting the results from our survey of 25 Galactic globular clusters with the MUSE integral-field spectrograph. In combination with our dedicated algorithm for source deblending, MUSE provides unique multiplex capabilities in crowded stellar fields and allows us to acquire samples of up to 20 000 stars within the half-light radius of each cluster. The present paper focuses on the analysis of the internal dynamics of 22 out of the 25 clusters, using about 500 000 spectra of 200 000 individual stars. Thanks to the large stellar samples per cluster, we are able to perform a detailed analysis of the central rotation and dispersion fields using both radial profiles and two-dimensional maps. The velocity dispersion profiles we derive show a good general agreement with existing radial velocity studies but typically reach closer to the cluster centres. By comparison with proper motion data we derive or update the dynamical distance estimates to 14 clusters. Compared to previous dynamical distance estimates for 47 Tuc, our value is in much better agreement with other methods. We further find significant (>3sigma) rotation in the majority (13/22) of our clusters. Our analysis seems to confirm earlier findings of a link between rotation and the ellipticities of globular clusters. In addition, we find a correlation between the strengths of internal rotation and the relaxation times of the clusters, suggesting that the central rotation fields are relics of the cluster formation that are gradually dissipated via two-body relaxation.
TL;DR: In this article, the surface density of the millimeter dust grains using the 3D radiative transfer disk code DALI was determined, based on high angular resolution ALMA 1.3 mm observations of the protoplanetary system AS 209 in the Ophiuchus star forming region.
Abstract: This paper presents new high angular resolution ALMA 1.3 mm dust continuum observations of the protoplanetary system AS 209 in the Ophiuchus star forming region. The dust continuum emission is characterized by a main central core and two prominent rings at r = 75 au and r = 130 au intervaled by two gaps at r = 62 au and r = 103 au. The two gaps have different widths and depths, with the inner one being narrower and shallower. We determined the surface density of the millimeter dust grains using the 3D radiative transfer disk code DALI. According to our fiducial model the inner gap is partially filled with millimeter grains while the outer gap is largely devoid of dust. The inferred surface density is compared to 3D hydrodynamical simulations (FARGO-3D) of planet-disk interaction. The outer dust gap is consistent with the presence of a giant planet ( M planet ~ 0.7 M Saturn ); the planet is responsible for the gap opening and for the pile-up of dust at the outer edge of the planet orbit. The simulations also show that the same planet could be the origin of the inner gap at r = 62 au. The relative position of the two dust gaps is close to the 2:1 resonance and we have investigated the possibility of a second planet inside the inner gap. The resulting surface density (including location, width and depth of the two dust gaps) are in agreement with the observations. The properties of the inner gap pose a strong constraint to the mass of the inner planet ( M planet M J ). In both scenarios (single or pair of planets), the hydrodynamical simulations suggest a very low disk viscosity ( α −4 ). Given the young age of the system (0.5–1 Myr), this result implies that the formation of giant planets occurs on a timescale of ≲1 Myr.
TL;DR: ‘Oumuamua—the first known interstellar object to have entered the Solar System—is probably a comet, albeit with unusual dust and chemical properties owing to its origin in a distant solar system.
Abstract: ‘Oumuamua (1I/2017 U1) is the first known object of interstellar origin to have entered the Solar System on an unbound and hyperbolic trajectory with respect to the Sun1. Various physical observations collected during its visit to the Solar System showed that it has an unusually elongated shape and a tumbling rotation state1–4 and that the physical properties of its surface resemble those of cometary nuclei5,6, even though it showed no evidence of cometary activity1,5,7. The motion of all celestial bodies is governed mostly by gravity, but the trajectories of comets can also be affected by non-gravitational forces due to cometary outgassing8. Because non-gravitational accelerations are at least three to four orders of magnitude weaker than gravitational acceleration, the detection of any deviation from a purely gravity-driven trajectory requires high-quality astrometry over a long arc. As a result, non-gravitational effects have been measured on only a limited subset of the small-body population9. Here we report the detection, at 30σ significance, of non-gravitational acceleration in the motion of ‘Oumuamua. We analyse imaging data from extensive observations by ground-based and orbiting facilities. This analysis rules out systematic biases and shows that all astrometric data can be described once a non-gravitational component representing a heliocentric radial acceleration proportional to r−2 or r−1 (where r is the heliocentric distance) is included in the model. After ruling out solar-radiation pressure, drag- and friction-like forces, interaction with solar wind for a highly magnetized object, and geometric effects originating from ‘Oumuamua potentially being composed of several spatially separated bodies or having a pronounced offset between its photocentre and centre of mass, we find comet-like outgassing to be a physically viable explanation, provided that ‘Oumuamua has thermal properties similar to comets.
University of Chicago1, University of Colorado Boulder2, University of Melbourne3, Cardiff University4, Fermilab5, National Institute of Standards and Technology6, Argonne National Laboratory7, University of KwaZulu-Natal8, Stanford University9, California Institute of Technology10, University of California, Berkeley11, Canadian Institute for Advanced Research12, McGill University13, Harvey Mudd College14, European Southern Observatory15, University of Illinois at Urbana–Champaign16, University of California, Davis17, Lawrence Berkeley National Laboratory18, University of Michigan19, University of Toronto20, University of Minnesota21, Case Western Reserve University22, School of the Art Institute of Chicago23, Harvard University24, University of Maryland, College Park25, University of California, Los Angeles26
TL;DR: Henning et al. as discussed by the authors measured the E-mode polarization angular power spectrum (EE) and temperature-E-mode cross-power spectrum (TE) of the cosmic microwave background (CMB) using 150 GHz data from three seasons of SPTpol observations.
Abstract: Author(s): Henning, JW; Sayre, JT; Reichardt, CL; Ade, PAR; Anderson, AJ; Austermann, JE; Beall, JA; Bender, AN; Benson, BA; Bleem, LE; Carlstrom, JE; Chang, CL; Chiang, HC; Cho, HM; Citron, R; Moran, CC; Crawford, TM; Crites, AT; Haan, TD; Dobbs, MA; Everett, W; Gallicchio, J; George, EM; Gilbert, A; Halverson, NW; Harrington, N; Hilton, GC; Holder, GP; Holzapfel, WL; Hoover, S; Hou, Z; Hrubes, JD; Huang, N; Hubmayr, J; Irwin, KD; Keisler, R; Knox, L; Lee, AT; Leitch, EM; Li, D; Lowitz, A; Manzotti, A; McMahon, JJ; Meyer, SS; Mocanu, L; Montgomery, J; Nadolski, A; Natoli, T; Nibarger, JP; Novosad, V; Padin, S; Pryke, C; Ruhl, JE; Saliwanchik, BR; Schaffer, KK; Sievers, C; Smecher, G; Stark, AA; Story, KT; Tucker, C; Vanderlinde, K; Veach, T; Vieira, JD; Wang, G; Whitehorn, N; Wu, WLK; Yefremenko, V | Abstract: We present measurements of the E-mode polarization angular auto-power spectrum (EE) and temperature-E-mode cross-power spectrum (TE) of the cosmic microwave background (CMB) using 150 GHz data from three seasons of SPTpol observations. We report the power spectra over the spherical harmonic multipole range 50 l l ≤ 8000 and detect nine acoustic peaks in the EE spectrum with high signal-to-noise ratio. These measurements are the most sensitive to date of the EE and TE power spectra at l g 1050 and l g 1475, respectively. The observations cover 500 , a fivefold increase in area compared to previous SPTpol analyses, which increases our sensitivity to the photon diffusion damping tail of the CMB power spectra enabling tighter constraints on ΛCDM model extensions. After masking all sources with unpolarized flux mJy, we place a 95% confidence upper limit on residual polarized point-source power of at Dl = l(l+1)ll/2π l 0.107 μK2 at l = 3000, suggesting that the EE damping tail dominates foregrounds to at least l= 4050 with modest source masking. We find that the SPTpol data set is in mild tension with the ΛCDM model (2.1 δ), and different data splits prefer parameter values that differ at the ∼ 1 δ level. When fitting SPTpol data at l l 1000, we find cosmological parameter constraints consistent with those for Planck temperature. Including SPTpol data at lg 1000 results in a preference for a higher value of the expansion rate (H071.3 ± 2.1 Km s-1 Mpc-1) and a lower value for present-day density fluctuations (δ8 =0.77 ±0.02).
TL;DR: In this paper, the masses of confirmed exoplanets and compared their dependence on stellar mass with the same dependence for protoplanetary disk masses measured in ∼1-3 Myr old star-forming regions.
Abstract: When and how planets form in protoplanetary disks is still a topic of discussion. Exoplanet detection surveys and protoplanetary disk surveys are now providing results that are leading to new insights. We collect the masses of confirmed exoplanets and compare their dependence on stellar mass with the same dependence for protoplanetary disk masses measured in ∼1–3 Myr old star-forming regions. We recalculated the disk masses using the new estimates of their distances derived from Gaia DR2 parallaxes. We note that single and multiple exoplanetary systems form two different populations, probably pointing to a different formation mechanism for massive giant planets around very low-mass stars. While expecting that the mass in exoplanetary systems is much lower than the measured disk masses, we instead find that exoplanetary systems masses are comparable or higher than the most massive disks. This same result is found by converting the measured planet masses into heavy element content (core masses for the giant planets and full masses for the super-Earth systems) and by comparing this value with the disk dust masses. Unless disk dust masses are heavily underestimated, this is a big conundrum. An extremely efficient recycling of dust particles in the disk cannot solve this conundrum. This implies that either the cores of planets have formed very rapidly (<0.1–1 Myr) and a large amount of gas is expelled on the same timescales from the disk, or that disks are continuously replenished by fresh planet-forming material from the environment. These hypotheses can be tested by measuring disk masses in even younger targets and by better understanding if and how the disks are replenished by their surroundings.
Liverpool John Moores University1, University of Hamburg2, Monash University, Clayton campus3, University of Western Australia4, University of St Andrews5, Cardiff University6, University of Edinburgh7, Ames Research Center8, University of New South Wales9, University of the Western Cape10, Max Planck Society11, University of Bonn12, Australian Astronomical Observatory13, University of Sussex14, Vanderbilt University15, Durham University16, Macquarie University17, Swinburne University of Technology18, University of Nottingham19, University of Sydney20, University of Bristol21, Australian National University22, European Space Research and Technology Centre23, University of Louisville24, Leiden University25, University of Copenhagen26, Queen Mary University of London27, European Southern Observatory28
TL;DR: The Galaxy And Mass Assembly (GAMA) survey as discussed by the authors is a spectroscopic redshift and multiwavelength photometric survey in three equatorial regions each of 60.0, G12, and G15.
Abstract: We describe data release 3 (DR3) of the Galaxy And Mass Assembly (GAMA) survey. The GAMA survey is a spectroscopic redshift and multiwavelength photometric survey in three equatorial regions each of 60.0 deg2 (G09, G12, and G15), and two southern regions of 55.7 deg2 (G02) and 50.6 deg2 (G23). DR3 consists of: the first release of data covering the G02 region and of data on H-ATLAS (Herschel – Astrophysical Terahertz Large Area Survey) sources in the equatorial regions; and updates to data on sources released in DR2. DR3 includes 154 809 sources with secure redshifts across four regions. A subset of the G02 region is 95.5 per cent redshift complete to r < 19.8 mag over an area of 19.5 deg2, with 20 086 galaxy redshifts, that overlaps substantially with the XXL survey (X-ray) and VIPERS (redshift survey). In the equatorial regions, the main survey has even higher completeness (98.5 per cent), and spectra for about 75 per cent of H-ATLAS filler targets were also obtained. This filler sample extends spectroscopic redshifts, for probable optical counterparts to H-ATLAS submillimetre sources, to 0.8 mag deeper (r < 20.6 mag) than the GAMA main survey. There are 25 814 galaxy redshifts for H-ATLAS sources from the GAMA main or filler surveys. GAMA DR3 is available at the survey website (www.gama-survey.org/dr3/).
TL;DR: In this article, the authors compared the tension between H 0 to the value inferred from CMB observations assuming ΛCDM, making it important to check for potential systematic uncertainties in either approach.
Abstract: The most precise local measurements of H 0 rely on observations of Type Ia supernovae (SNe Ia) coupled with Cepheid distances to SN Ia host galaxies. Recent results have shown tension comparing H 0 to the value inferred from CMB observations assuming ΛCDM, making it important to check for potential systematic uncertainties in either approach. To date, precise local H 0 measurements have used SN Ia distances based on optical photometry, with corrections for light curve shape and colour. Here, we analyse SNe Ia as standard candles in the near-infrared (NIR), where luminosity variations in the supernovae and extinction by dust are both reduced relative to the optical. From a combined fit to 9 nearby calibrator SNe with host Cepheid distances from and 27 SNe in the Hubble flow, we estimate the absolute peak J magnitude M J = −18.524 ± 0.041 mag and H 0 = 72.8 ± 1.6 (statistical) ±2.7 (systematic) km s-1 Mpc-1 . The 2.2% statistical uncertainty demonstrates that the NIR provides a compelling avenue to measuring SN Ia distances, and for our sample the intrinsic (unmodeled) peak J magnitude scatter is just ~0.10 mag, even without light curve shape or colour corrections. Our results do not vary significantly with different sample selection criteria, though photometric calibration in the NIR may be a dominant systematic uncertainty. Our findings suggest that tension in the competing H 0 distance ladders is likely not a result of supernova systematics that could be expected to vary between optical and NIR wavelengths, like dust extinction. We anticipate further improvements in H 0 with a larger calibrator sample of SNe Ia with Cepheid distances, more Hubble flow SNe Ia with NIR light curves, and better use of the full NIR photometric data set beyond simply the peak J -band magnitude.
TL;DR: Observations of 13CO and C18O emission for a sample of four dust-enshrouded starbursts at redshifts of approximately two to three reveal that massive stars are more numerous in starburst events than in ordinary star-forming spiral galaxies.
Abstract: All measurements of cosmic star formation must assume an initial distribution of stellar masses-the stellar initial mass function-in order to extrapolate from the star-formation rate measured for typically rare, massive stars (of more than eight solar masses) to the total star-formation rate across the full stellar mass spectrum 1 . The shape of the stellar initial mass function in various galaxy populations underpins our understanding of the formation and evolution of galaxies across cosmic time 2 . Classical determinations of the stellar initial mass function in local galaxies are traditionally made at ultraviolet, optical and near-infrared wavelengths, which cannot be probed in dust-obscured galaxies2,3, especially distant starbursts, whose apparent star-formation rates are hundreds to thousands of times higher than in the Milky Way, selected at submillimetre (rest-frame far-infrared) wavelengths4,5. The 13C/18O isotope abundance ratio in the cold molecular gas-which can be probed via the rotational transitions of the 13CO and C18O isotopologues-is a very sensitive index of the stellar initial mass function, with its determination immune to the pernicious effects of dust. Here we report observations of 13CO and C18O emission for a sample of four dust-enshrouded starbursts at redshifts of approximately two to three, and find unambiguous evidence for a top-heavy stellar initial mass function in all of them. A low 13CO/C18O ratio for all our targets-alongside a well tested, detailed chemical evolution model benchmarked on the Milky Way 6 -implies that there are considerably more massive stars in starburst events than in ordinary star-forming spiral galaxies. This can bring these extraordinary starbursts closer to the 'main sequence' of star-forming galaxies 7 , although such main-sequence galaxies may not be immune to changes in initial stellar mass function, depending on their star-formation densities.
Academia Sinica1, University of Arizona2, Harvard University3, University of California, Berkeley4, University of Nevada, Las Vegas5, European Southern Observatory6, University of Chile7, California Institute of Technology8, Kogakuin University9, Russian Academy of Sciences10, University of Tokyo11, University of Oklahoma12
TL;DR: In this paper, Russian Science Foundation and National Aeronautics and Space Administration (NAOJ ALMA Scientific Research Grant) were used for the development of the ALMA project.
Abstract: Russian Science Foundation
17-12-01168
Jet Propulsion Laboratory, California Institute of Technology
National Aeronautics and Space Administration
NAOJ ALMA Scientific Research Grant
2016-02A
Institute for the Physics and Mathematics of the Universe1, University of Tokyo2, The Open University of Japan3, Ehime University4, Osaka Sangyo University5, University of Tsukuba6, Nagoya University7, Graduate University for Advanced Studies8, European Southern Observatory9, University of Hyogo10, Academia Sinica Institute of Astronomy and Astrophysics11
Peking University1, University of Arizona2, Leiden University3, University of Leicester4, University of Cambridge5, University of Milan6, Vassar College7, Smith College8, University of Grenoble9, University of Victoria10, Chinese Academy of Sciences11, Max Planck Society12, Rice University13, University of Paris14, European Southern Observatory15, University of Chicago16, INAF17, Space Telescope Science Institute18, Ames Research Center19
TL;DR: In this article, the authors identify the most frequently revealed substructure in ALMA dust observations of protoplanetary disks, and measure their properties to investigate how they form, including axisymmetric rings and gaps.
Abstract: Rings are the most frequently revealed substructure in ALMA dust observations of protoplanetary disks, but their origin is still hotly debated. In this paper, we identify dust substructures in 12 disks and measure their properties to investigate how they form. This subsample of disks is selected from a high-resolution ($\sim0.12''$) ALMA 1.33 mm survey of 32 disks in the Taurus star-forming region, which was designed to cover a wide range of sub-mm brightness and to be unbiased to previously known substructures. While axisymmetric rings and gaps are common within our sample, spiral patterns and high contrast azimuthal asymmetries are not detected. Fits of disk models to the visibilities lead to estimates of the location and shape of gaps and rings, the flux in each disk component, and the size of the disk. The dust substructures occur across a wide range of stellar mass and disk brightness. Disks with multiple rings tend to be more massive and more extended. The correlation between gap locations and widths, the intensity contrast between rings and gaps, and the separations of rings and gaps could all be explained if most gaps are opened by low-mass planets (super-Earths and Neptunes) in the condition of low disk turbulence ($\alpha=10^{-4}$). The gap locations are not well correlated with the expected locations of CO and N$_2$ ice lines, so condensation fronts are unlikely to be a universal mechanism to create gaps and rings, though they may play a role in some cases.
TL;DR: In this article, the authors used the Markov Chain Monte Carlo method to fit the mean RAR to 175 individual galaxies in the SPARC database, marginalizing over stellar mass-to-light ratio, galaxy distance, and disk inclination.
Abstract: Galaxies follow a tight radial acceleration relation (RAR): the acceleration observed at every radius correlates with that expected from the distribution of baryons. We use the Markov Chain Monte Carlo method to fit the mean RAR to 175 individual galaxies in the SPARC database, marginalizing over stellar mass-to-light ratio ($\Upsilon_{\star}$), galaxy distance, and disk inclination. Acceptable fits with astrophysically reasonable parameters are found for the vast majority of galaxies. The residuals around these fits have an rms scatter of only 0.057 dex ($\sim$13$\%$). This is in agreement with the predictions of modified Newtonian dynamics (MOND). We further consider a generalized version of the RAR that, unlike MOND, permits galaxy-to-galaxy variation in the critical acceleration scale. The fits are not improved with this additional freedom: there is no credible indication of variation in the critical acceleration scale. The data are consistent with the action of a single effective force law. The apparent universality of the acceleration scale and the small residual scatter are key to understanding galaxies.
University of Tokyo1, Institute for the Physics and Mathematics of the Universe2, Carnegie Institution for Science3, Mahidol University4, Subaru5, University of California, Santa Barbara6, The Open University of Japan7, Ehime University8, National Tsing Hua University9, Graduate University for Advanced Studies10, European Southern Observatory11, Academia Sinica Institute of Astronomy and Astrophysics12
TL;DR: Shibuya et al. as discussed by the authors presented Lyα and UV-nebular emission line properties of bright Lyα emitters (LAEs) at z = 6-7 with a luminosity of log LLyα/[erg s-1] = 43-44 identified in the 21 deg2 area of the SILVERRUSH early sample developed with the Subaru Hyper Suprime-Cam survey data.
Abstract: Author(s): Shibuya, T; Ouchi, M; Harikane, Y; Rauch, M; Ono, Y; Mukae, S; Higuchi, R; Kojima, T; Yuma, S; Lee, CH; Furusawa, H; Konno, A; Martin, CL; Shimasaku, K; Taniguchi, Y; Kobayashi, MAR; Kajisawa, M; Nagao, T; Goto, T; Kashikawa, N; Komiyama, Y; Kusakabe, H; Momose, R; Nakajima, K; Tanaka, M; Wang, SY | Abstract: We present Lyα and UV-nebular emission line properties of bright Lyα emitters (LAEs) at z = 6-7 with a luminosity of log LLyα/[erg s-1] = 43-44 identified in the 21 deg2 area of the SILVERRUSH early sample developed with the Subaru Hyper Suprime-Cam survey data. Our optical spectroscopy newly confirms 21 bright LAEs with clear Lyα emission, and contributes to making a spectroscopic sample of 96 LAEs at z = 6-7 in SILVERRUSH. From the spectroscopic sample, we select seven remarkable LAEs as bright as Himiko and CR7 objects, and perform deep Keck/MOSFIRE and Subaru/nuMOIRCS near-infrared spectroscopy reaching the 3 σ flux limit of ∼2 × 10-18 erg s-1 for the UV-nebular emission lines of He II λ1640, CIV λλ1548,1550, and OIII]λλ1661,1666. Except for one tentative detection of C IV, we find no strong UV-nebular lines down to the flux limit, placing the upper limits of the rest-frame equivalent widths (EW0) of ∼2-4 A for CIV, He II, and OIII] lines. We also investigate the VLT/X-SHOOTER spectrum of CR7 whose 6 σ detection of He II is claimed by Sobral et al. Although two individuals and the ESO archive service carefully reanalyzed the X-SHOOTER data that are used in the study of Sobral et al., no He II signal of CR7 is detected, supportive of weak UV-nebular lines of the bright LAEs even for CR7. The spectral properties of these bright LAEs are thus clearly different from those of faint dropouts at z ∼ 7 that have strong UV-nebular lines shown in the various studies. Comparing these bright LAEs and the faint dropouts, we find anti-correlations between the UV-nebular line EW0 and the UV-continuum luminosity, which are similar to those found at z ∼ 2-3.