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1.
  • Fan, Lulu, 1982, et al. (författare)
  • The SCUBA-2 850 mu m Follow-up of WISE-selected, Luminous Dust-obscured Quasars
  • 2017
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 129:982
  • Tidskriftsartikel (refereegranskat)abstract
    • Hot dust-obscured galaxies (Hot DOGs) are a new population recently discovered in the Wide-field Infrared Survey Explorer All-Sky survey. Multiwavelength follow-up observations suggest that they are luminous, dust-obscured quasars at high redshift. Here we present the JCMT SCUBA-2 850 mu m follow-up observations of 10 Hot DOGs. Four out of ten Hot DOGs have been detected at >3 sigma level. Based on the IR SED decomposition approach, we derive the IR luminosities of AGN torus and cold dust components. Hot DOGs in our sample are extremely luminous with most of them having L-IR(tot) > 10(14) L-circle dot. The torus emissions dominate the total IR energy output. However, the cold dust contribution is still non-negligible, with the fraction of the cold dust contribution to the total IR luminosity (similar to 8%-24%) being dependent on the choice of torus model. The derived cold dust temperatures in Hot DOGs are comparable to those in UV bright quasars with similar IR luminosity, but much higher than those in SMGs. Higher dust temperatures in Hot DOGs may be due to the more intense radiation field caused by intense starburst and obscured AGN activities. Fourteen and five submillimeter serendipitous sources in the 10 SCUBA-2 fields around Hot DOGs have been detected at >3 sigma and >3.5 sigma levels, respectively. By estimating their cumulative number counts, we confirm the previous argument that Hot DOGs lie in dense environments. Our results support the scenario in which Hot DOGs are luminous, dust-obscured quasars lying in dense environments, and being in the transition phase between extreme starburst and UV-bright quasars.
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2.
  • Dodkins, Rupert H., et al. (författare)
  • First principle simulator of a stochastically varying image plane for photon-counting high contrast applications
  • 2020
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 132:1016, s. 1-12
  • Tidskriftsartikel (refereegranskat)abstract
    • Optical and near-infrared Microwave Kinetic Inductance Detectors, or MKIDs are low-temperature detectors with inherent spectral resolution that are able to instantly register individual photons with potentially no false counts or readout noise. These properties make MKIDs transformative for exoplanet direct imaging by enabling photon-statistics-based planet-discrimination techniques as well as performing conventional noise-subtraction techniques on shorter timescales. These detectors are in the process of rapid development, and as such, the full extent of their performance enhancing potential has not yet be quantified. MKID Exoplanet Direct Imaging Simulator, or MEDIS, is a general-purpose end-to-end numerical simulator for high-contrast observations with MKIDs. The simulator exploits current optical propagation libraries and augments them with a new MKIDs simulation module to provide a pragmatic model of many of the degradation effects present during the detection process. We use MEDIS to demonstrate how changes in various MKID properties affect the contrast-separation performance when conventional differential imaging techniques are applied to low-flux, short duration observations. We show that to improve performance at close separations will require increasing the maximum count rate or pixel sampling when there is high residual flux after the coronagraph. We predict that taking pixel yield from the value achieved by current instruments of 80% and increasing it to 100% would result in an improvement in contrast of a factor of ∼4 at 3λ/D and ∼8 at 6λ/D. Achieving better contrast performance in this low flux regime would then require exploiting the information encoded in the photon arrival time statistics.
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3.
  • Hsiao, E. Y., et al. (författare)
  • Carnegie Supernova Project-II : The Near-infrared Spectroscopy Program
  • 2019
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 131:995
  • Tidskriftsartikel (refereegranskat)abstract
    • Shifting the focus of Type Ia supernova (SN Ia) cosmology to the near infrared (NIR) is a promising way to significantly reduce the systematic errors, as the strategy minimizes our reliance on the empirical width-luminosity relation and uncertain dust laws. Observations in the NIR are also crucial for our understanding of the origins and evolution of these events, further improving their cosmological utility. Any future experiments in the rest-frame NIR will require knowledge of the SN Ia NIR spectroscopic diversity, which is currently based on a small sample of observed spectra. Along with the accompanying paper, Phillips et al., we introduce the Carnegie Supernova Project-II (CSP-II), to follow-up nearby SNe Ia in both the optical and the NIR. In particular, this paper focuses on the CSP-II NIR spectroscopy program, describing the survey strategy, instrumental setups, data reduction, sample characteristics, and future analyses on the data set. In collaboration with the Harvard-Smithsonian Center for Astrophysics (CfA) Supernova Group, we obtained 661 NIR spectra of 157 SNe Ia. Within this sample, 451 NIR spectra of 90 SNe Ia have corresponding CSP-II follow-up light curves. Such a sample will allow detailed studies of the NIR spectroscopic properties of SNe Ia, providing a different perspective on the properties of the unburned material; the radioactive and stable nickel produced; progenitor magnetic fields; and searches for possible signatures of companion stars.
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4.
  • Kessler, R., et al. (författare)
  • Models and Simulations for the Photometric LSST Astronomical Time Series Classification Challenge (PLAsTiCC)
  • 2019
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 131:1003
  • Tidskriftsartikel (refereegranskat)abstract
    • We describe the simulated data sample for the Photometric Large Synoptic Survey Telescope (LSST) Astronomical Time Series Classification Challenge (PLAsTiCC), a publicly available challenge to classify transient and variable events that will be observed by the LSST, a new facility expected to start in the early 2020s. The challenge was hosted by Kaggle, ran from 2018 September 28 to December 17, and included 1094 teams competing for prizes. Here we provide details of the 18 transient and variable source models, which were not revealed until after the challenge, and release the model libraries at https://doi.org/10.5281/zenodo.2612896. We describe the LSST Operations Simulator used to predict realistic observing conditions, and we describe the publicly available SNANA simulation code used to transform the models into observed fluxes and uncertainties in the LSST passbands (ugrizy). Although PLAsTiCC has finished, the publicly available models and simulation tools are being used within the astronomy community to further improve classification, and to study contamination in photometrically identified samples of SN Ia used to measure properties of dark energy. Our simulation framework will continue serving as a platform to improve the PLAsTiCC models, and to develop new models.
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5.
  • Kim, Y.-L., et al. (författare)
  • New Modules for the SEDMachine to Remove Contaminations from Cosmic Rays and Non-target Light : BYECR and CONTSEP
  • 2022
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 134:1032
  • Tidskriftsartikel (refereegranskat)abstract
    • Currently time-domain astronomy can scan the entire sky on a daily basis, discovering thousands of interesting transients every night. Classifying the ever-increasing number of new transients is one of the main challenges for the astronomical community. One solution that addresses this issue is the robotically controlled Spectral Energy Distribution Machine (SEDM) which supports the Zwicky Transient Facility (ZTF). SEDM with its pipeline pysedm demonstrates that real-time robotic spectroscopic classification is feasible. In an effort to improve the quality of the current SEDM data, we present here two new modules, byecr and contsep. The first removes contamination from cosmic rays, and the second removes contamination from non-target light. These new modules are part of the automated pysedm pipeline and fully integrated with the whole process. Employing byecr and contsep modules together automatically extracts more spectra than the current pysedm pipeline. Using SNID classification results, the new modules show an improvement in the classification rate and accuracy of 2.8% and 1.7%, respectively, while the strength of the cross-correlation remains the same. Improvements to the SEDM astrometry would further boost the improvement of the contsep module. This kind of robotic follow-up with a fully automated pipeline has the potential to provide the spectroscopic classifications for the transients discovered by ZTF and also by the Rubin Observatory's Legacy Survey of Space and Time.
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6.
  • Matthews, L. D., et al. (författare)
  • The ALMA phasing system: A beamforming capability for ultra-high-resolution science at (sub)millimeter wavelengths
  • 2018
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 130:983
  • Tidskriftsartikel (refereegranskat)abstract
    • The Atacama Millimeter/submillimeter Array (ALMA) Phasing Project (APP) has developed and deployed the hardware and software necessary to coherently sum the signals of individual ALMA antennas and record the aggregate sum in Very Long Baseline Interferometry (VLBI) Data Exchange Format. These beamforming capabilities allow the ALMA array to collectively function as the equivalent of a single large aperture and participate in global VLBI arrays. The inclusion of phased ALMA in current VLBI networks operating at (sub) millimeter wavelengths provides an order of magnitude improvement in sensitivity, as well as enhancements in u–v coverage and north–south angular resolution. The availability of a phased ALMA enables a wide range of new ultra-high angular resolution science applications, including the resolution of supermassive black holes on event horizon scales and studies of the launch and collimation of astrophysical jets. It also provides a high-sensitivity aperture that may be used for investigations such as pulsar searches at high frequencies. This paper provides an overview of the ALMA Phasing System design, implementation, and performance characteristics.
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7.
  • Ye, Quanzhi, et al. (författare)
  • Toward Efficient Detection of Small Near-Earth Asteroids Using the Zwicky Transient Facility (ZTF)
  • 2019
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 131:1001
  • Tidskriftsartikel (refereegranskat)abstract
    • We describe ZStreak, a semi-real-time pipeline specialized in detecting small, fast-moving, near-Earth asteroids (NEAs), which is currently operating on the data from the newly commissioned Zwicky Transient Facility (ZTF) survey. Based on a prototype originally developed by Waszczak et al. (2017) for the Palomar Transient Factory (PTF), the predecessor of ZTF, ZStreak features an improved machine-learning model that can cope with the 10x data rate increment between PTF and ZTF. Since its first discovery on 2018 February 5 (2018 CL), ZTF/ZStreak has discovered 45 confirmed new NEAs over a total of 232 observable nights until 2018 December 31. Most of the discoveries are small NEAs, with diameters less than similar to 100. m. By analyzing the discovery circumstances, we find that objects having the first to last detection time interval under 2. hr are at risk of being lost. We will further improve real-time follow-up capabilities, and work on suppressing false positives using deep learning.
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8.
  • Adams, S. M., et al. (författare)
  • iPTF Survey for Cool Transients
  • 2018
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 130:985
  • Tidskriftsartikel (refereegranskat)abstract
    • We performed a wide-area (2000 deg2) g and I band experiment as part of a two month extension to the Intermediate Palomar Transient Factory. We discovered 36 extragalactic transients including iPTF17lf, a highly reddened local SN Ia, iPTF17bkj, a new member of the rare class of transitional Ibn/IIn supernovae, and iPTF17be, a candidate luminous blue variable outburst. We do not detect any luminous red novae and place an upper limit on their rate. We show that adding a slow-cadence I band component to upcoming surveys such as the Zwicky Transient Facility will improve the photometric selection of cool and dusty transients.
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9.
  • Ashcraft, Teresa A., et al. (författare)
  • Ultra-deep Large Binocular Camera U-band Imaging of the GOODS-North Field : Depth Versus Resolution
  • 2018
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 130:988
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a study of the trade-off between depth and resolution using a large number of U-band imaging observations in the GOODS-North field from the Large Binocular Camera (LBC) on the Large Binocular Telescope (LBT). Having acquired over 30 hr of data (315 images with 5-6 minutes exposures), we generated multiple image mosaics, starting with the best atmospheric seeing images (FWHM less than or similar to 0 ''.8), which constitute similar to 10% of the total data set. For subsequent mosaics, we added in data with larger seeing values until the final, deepest mosaic included all images with FWHM less than or similar to 1 ''.8 (similar to 94% of the total data set). From the mosaics, we made object catalogs to compare the optimal-resolution, yet shallower image to the lower-resolution but deeper image. We show that the number counts for both images are similar to 90% complete to U-AB less than or similar to 26 mag. Fainter than U-AB similar to 27 mag, the object counts from the optimal-resolution image start to drop-off dramatically (90% between U-AB = 27 and 28 mag), while the deepest image with better surface-brightness sensitivity (mu(AB)(U) less than or similar to 32 mag arcsec(-2)) show a more gradual drop (10% between U-AB similar or equal to 27 and 28 mag). For the brightest galaxies within the GOODS-N field, structure and clumpy features within the galaxies are more prominent in the optimal-resolution image compared to the deeper mosaics. We conclude that for studies of brighter galaxies and features within them, the optimal-resolution image should be used. However, to fully explore and understand the faintest objects, the deeper imaging with lower resolution are also required. Finally, we find-for 220 brighter galaxies with U-AB less than or similar to 23 mag-only marginal differences in total flux between the optimal-resolution and lower-resolution light-profiles to mu(AB)(U) less than or similar to 32 mag arcsec(-2). In only 10% of the cases are the total-flux differences larger than 0.5 mag. This helps constrain how much flux can be missed from galaxy outskirts, which is important for studies of the Extragalactic Background Light.
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10.
  • Bellm, Eric C., et al. (författare)
  • The Zwicky Transient Facility : Surveys and Scheduler
  • 2019
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 131:1000
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a novel algorithm for scheduling the observations of time-domain imaging surveys. Our integer linear programming approach optimizes an observing plan for an entire night by assigning targets to temporal blocks, enabling strict control of the number of exposures obtained per field and minimizing filter changes. A subsequent optimization step minimizes slew times between each observation. Our optimization metric self-consistently weights contributions from time-varying airmass, seeing, and sky brightness to maximize the transient discovery rate. We describe the implementation of this algorithm on the surveys of the Zwicky Transient Facility and present its on-sky performance.
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11.
  • Bellm, Eric C., et al. (författare)
  • The Zwicky Transient Facility : System Overview, Performance, and First Results
  • 2019
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 131:995
  • Tidskriftsartikel (refereegranskat)abstract
    • The Zwicky Transient Facility (ZTF) is a new optical time-domain survey that uses the Palomar 48 inch Schmidt telescope. A custom-built wide-field camera provides a 47 deg(2) field of view and 8 s readout time, yielding more than an order of magnitude improvement in survey speed relative to its predecessor survey, the Palomar Transient Factory. We describe the design and implementation of the camera and observing system. The ZTF data system at the Infrared Processing and Analysis Center provides near-real-time reduction to identify moving and varying objects. We outline the analysis pipelines, data products, and associated archive. Finally, we present on-sky performance analysis and first scientific results from commissioning and the early survey. ZTF's public alert stream will serve as a useful precursor for that of the Large Synoptic Survey Telescope.
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12.
  • Berne, Olivier, et al. (författare)
  • PDRs4All : A JWST Early Release Science Program on Radiative Feedback from Massive Stars
  • 2022
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 134:1035
  • Tidskriftsartikel (refereegranskat)abstract
    • Massive stars disrupt their natal molecular cloud material through radiative and mechanical feedback processes. These processes have profound effects on the evolution of interstellar matter in our Galaxy and throughout the universe, from the era of vigorous star formation at redshifts of 1-3 to the present day. The dominant feedback processes can be probed by observations of the Photo-Dissociation Regions (PDRs) where the far-ultraviolet photons of massive stars create warm regions of gas and dust in the neutral atomic and molecular gas. PDR emission provides a unique tool to study in detail the physical and chemical processes that are relevant for most of the mass in inter- and circumstellar media including diffuse clouds, proto-planetary disks, and molecular cloud surfaces, globules, planetary nebulae, and star-forming regions. PDR emission dominates the infrared (IR) spectra of star-forming galaxies. Most of the Galactic and extragalactic observations obtained with the James Webb Space Telescope (JWST) will therefore arise in PDR emission. In this paper we present an Early Release Science program using the MIRI, NIRSpec, and NIRCam instruments dedicated to the observations of an emblematic and nearby PDR: the Orion Bar. These early JWST observations will provide template data sets designed to identify key PDR characteristics in JWST observations. These data will serve to benchmark PDR models and extend them into the JWST era. We also present the Science-Enabling products that we will provide to the community. These template data sets and Science-Enabling products will guide the preparation of future proposals on star-forming regions in our Galaxy and beyond and will facilitate data analysis and interpretation of forthcoming JWST observations.
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13.
  • Bianco, Federica B., et al. (författare)
  • Presto-Color : A Photometric Survey Cadence for Explosive Physics and Fast Transients
  • 2019
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 131:1000
  • Tidskriftsartikel (refereegranskat)abstract
    • We identify minimal observing cadence requirements that enable photometric astronomical surveys to detect and recognize fast and explosive transients and fast transient features. Observations in two different filters within a short time window (e.g., g-and-i, or r-and-z, within <0.5 hr) and a repeat of one of those filters with a longer time window (e.g., >1.5 hr) are desirable for this purpose. Such an observing strategy delivers both the color and light curve evolution of transients on the same night. This allows the identification and initial characterization of fast transient-or fast features of longer timescale transients-such as rapidly declining supernovae, kilonovae, and the signatures of SN ejecta interacting with binary companion stars or circumstellar material. Some of these extragalactic transients are intrinsically rare and generally all hard to find, thus upcoming surveys like the Large Synoptic Survey Telescope (LSST) could dramatically improve our understanding of their origin and properties. We colloquially refer to such a strategy implementation for the LSST as the Presto-Color strategy (rapid-color). This cadence's minimal requirements allow for overall optimization of a survey for other science goals.
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14.
  • Bolli, P., et al. (författare)
  • An international survey of front-end receivers and observing performance of telescopes for radio astronomy
  • 2019
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 131:1002
  • Tidskriftsartikel (refereegranskat)abstract
    • © 2019. The Astronomical Society of the Pacific. This paper presents a survey of microwave front-end receivers installed at radio telescopes throughout the world. This unprecedented analysis was conducted as part of a review of front-end developments for Italian radio telescopes, initiated by the Italian National Institute for Astrophysics in 2016. Fifteen international radio telescopes have been selected to be representative of the instrumentation used for radio astronomical observations in the frequency domain from 300 MHz to 116 GHz. A comprehensive description of the existing receivers is presented and their characteristics are compared and discussed. The observing performances of the complete receiving chains are also presented. An overview of ongoing developments illustrates and anticipates future trends in front-end projects to meet the most ambitious scientific research goals.
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15.
  • Connor, Liam, et al. (författare)
  • Galactic Radio Explorer: An All-sky Monitor for Bright Radio Bursts
  • 2021
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 133:1025
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the Galactic Radio Explorer (GReX), an all-sky monitor to probe the brightest bursts in the radio sky. Building on the success of STARE2, we will search for fast radio bursts emitted from Galactic magnetars as well as bursts from nearby galaxies. GReX will search down to similar to ten microseconds time resolution, allowing us to find new super giant radio pulses from Milky Way pulsars and study their broadband emission. The proposed instrument will employ ultra-wide band (0.7-2 GHz) feeds coupled to a high-performance (receiver temperature <10 K) low noise amplifier originally developed for the DSA-110 and DSA-2000 projects. In GReX Phase I (GReX-I), unit systems will be deployed at Owens Valley Radio Observatory and Big Smoky Valley, Nevada. Phase II will expand the array, placing feeds in India, Australia, and elsewhere in order to build up to continuous coverage of nearly 4 pi steradians and to increase our exposure to the Galactic plane. We model the local magnetar population to forecast for GReX, finding the improved sensitivity and increased exposure to the Galactic plane could lead to dozens of FRB-like bursts per year.
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16.
  • Coughlin, Michael W., et al. (författare)
  • 2900 Square Degree Search for the Optical Counterpart of Short Gamma-Ray Burst GRB 180523B with the Zwicky Transient Facility
  • 2019
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 131:998
  • Tidskriftsartikel (refereegranskat)abstract
    • There is significant interest in the models for production of short gamma-ray bursts (GRBs). Until now, the number of known short GRBs with multi-wavelength afterglows has been small. While the Fermi GRB Monitor detects many GRBs relative to the Neil Gehrels Swift Observatory, the large localization regions makes the search for counterparts difficult. With the Zwicky Transient Facility (ZTF) recently achieving first light, it is now fruitful to use its combination of depth (m(AB) similar to 20.6), field of view (approximate to 47 square degrees), and survey cadence (every similar to 3 days) to perform Target of Opportunity observations. We demonstrate this capability on GRB 180523B, which was recently announced by the Fermi GRB Monitor as a short GRB. ZTF imaged approximate to 2900 square degrees of the localization region, resulting in the coverage of 61.6% of the enclosed probability over two nights to a depth of m(AB) similar to 20.5. We characterized 14 previously unidentified transients, and none were found to be consistent with a short GRB counterpart. This search with the ZTF shows it is an efficient camera for searching for coarsely localized short GRB and gravitational-wave counterparts, allowing for a sensitive search with minimal interruption to its nominal cadence.
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17.
  • Goddi, C., et al. (författare)
  • Calibration of ALMA as a Phased Array. ALMA Observations During the 2017 VLBI Campaign
  • 2019
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 131:1001
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a detailed description of the special procedures for calibration and quality assurance of Atacama Large Millimeter/submillimeter Array (ALMA) observations in Very Long Baseline Interferometry (VLBI) mode. These procedures are required to turn the phased ALMA array into a fully calibrated VLBI station. As an illustration of these methodologies, we present full-polarization observations carried out with ALMA as a phased array at 3 mm (Band 3) and 1.3 mm (Band 6) as part of Cycle-4. These are the first VLBI science observations conducted with ALMA and were obtained during a 2017 VLBI campaign in concert with other telescopes worldwide as part of the Global mm-VLBI Array (GMVA, April 1-3) and the Event Horizon Telescope (EHT, April 5-11) in ALMA Bands 3 and 6, respectively.
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18.
  • Graham, Matthew J., et al. (författare)
  • The Zwicky Transient Facility : Science Objectives
  • 2019
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 131:1001
  • Tidskriftsartikel (refereegranskat)abstract
    • The Zwicky Transient Facility (ZTF), a public-private enterprise, is a new time-domain survey employing a dedicated camera on the Palomar 48-inch Schmidt telescope with a 47 deg(2) field of view and an 8 second readout time. It is well positioned in the development of time-domain astronomy, offering operations at 10% of the scale and style of the Large Synoptic Survey Telescope (LSST) with a single 1-m class survey telescope. The public surveys will cover the observable northern sky every three nights in g and r filters and the visible Galactic plane every night in g and r. Alerts generated by these surveys are sent in real time to brokers. A consortium of universities that provided funding (partnership) are undertaking several boutique surveys. The combination of these surveys producing one million alerts per night allows for exploration of transient and variable astrophysical phenomena brighter than r similar to 20.5 on timescales of minutes to years. We describe the primary science objectives driving ZTF, including the physics of supernovae and relativistic explosions, multi-messenger astrophysics, supernova cosmology, active galactic nuclei, and tidal disruption events, stellar variability, and solar system objects.
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19.
  • Hinkley, Sasha, et al. (författare)
  • The JWST Early Release Science Program for the Direct Imaging and Spectroscopy of Exoplanetary Systems
  • 2022
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 134:1039
  • Tidskriftsartikel (refereegranskat)abstract
    • The direct characterization of exoplanetary systems with high-contrast imaging is among the highest priorities for the broader exoplanet community. As large space missions will be necessary for detecting and characterizing exo-Earth twins, developing the techniques and technology for direct imaging of exoplanets is a driving focus for the community. For the first time, JWST will directly observe extrasolar planets at mid-infrared wavelengths beyond 5 μm, deliver detailed spectroscopy revealing much more precise chemical abundances and atmospheric conditions, and provide sensitivity to analogs of our solar system ice-giant planets at wide orbital separations, an entirely new class of exoplanet. However, in order to maximize the scientific output over the lifetime of the mission, an exquisite understanding of the instrumental performance of JWST is needed as early in the mission as possible. In this paper, we describe our 55 hr Early Release Science Program that will utilize all four JWST instruments to extend the characterization of planetary-mass companions to ∼15 μm as well as image a circumstellar disk in the mid-infrared with unprecedented sensitivity. Our program will also assess the performance of the observatory in the key modes expected to be commonly used for exoplanet direct imaging and spectroscopy, optimize data calibration and processing, and generate representative data sets that will enable a broad user base to effectively plan for general observing programs in future Cycles.
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20.
  • Kasliwal, M. M., et al. (författare)
  • The GROWTH Marshal : A Dynamic Science Portal for Time-domain Astronomy
  • 2019
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 131:997
  • Tidskriftsartikel (refereegranskat)abstract
    • We describe a dynamic science portal called the GROWTH Marshal that allows time-domain astronomers to define science programs; program filters to save sources from different discovery streams; coordinate follow-up with various robotic or classical telescopes; analyze the panchromatic follow-up data; and generate summary tables for publication. The GROWTH marshal currently serves 137 scientists, 38 science programs, and 67 telescopes. Every night, in real time, several science programs apply various customized filters to the 105 nightly alerts from the Zwicky Transient Facility. Here, we describe the schematic and explain the functionality of the various components of this international collaborative platform.
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21.
  • Mahabal, Ashish, et al. (författare)
  • Machine Learning for the Zwicky Transient Facility
  • 2019
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 131:997
  • Tidskriftsartikel (refereegranskat)abstract
    • The Zwicky Transient Facility is a large optical survey in multiple filters producing hundreds of thousands of transient alerts per night. We describe here various machine learning (ML) implementations and plans to make the maximal use of the large data set by taking advantage of the temporal nature of the data, and further combining it with other data sets. We start with the initial steps of separating bogus candidates from real ones, separating stars and galaxies, and go on to the classification of real objects into various classes. Besides the usual methods (e.g., based on features extracted from light curves) we also describe early plans for alternate methods including the use of domain adaptation, and deep learning. In a similar fashion we describe efforts to detect fast moving asteroids. We also describe the use of the Zooniverse platform for helping with classifications through the creation of training samples, and active learning. Finally we mention the synergistic aspects of ZTF and LSST from the ML perspective.
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22.
  • Muthukrishna, Daniel, et al. (författare)
  • RAPID : Early Classification of Explosive Transients Using Deep Learning
  • 2019
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 131:1005
  • Tidskriftsartikel (refereegranskat)abstract
    • We present Real-time Automated Photometric IDentification (RAPID), a novel time series classification tool capable of automatically identifying transients from within a day of the initial alert, to the full lifetime of a light curve. Using a deep recurrent neural network with gated recurrent units (GRUs), we present the first method specifically designed to provide early classifications of astronomical timeseries data, typing 12 different transient classes. Our classifier can process light curves with any phase coverage, and it does not rely on deriving computationally expensive features from the data, making RAPID well suited for processing the millions of alerts that ongoing and upcoming wide-field surveys such as the Zwicky Transient Facility (ZTF), and the Large Synoptic Survey Telescope (LSST) will produce. The classification accuracy improves over the lifetime of the transient as more photometric data becomes available, and across the 12 transient classes, we obtain an average area under the receiver operating characteristic curve of 0.95 and 0.98 at early and late epochs, respectively. We demonstrate RAPID's ability to effectively provide early classifications of observed transients from the ZTF data stream. We have made RAPID available as an open-source software package(8) for machine-learning-based alert brokers to use for the autonomous and quick classification of several thousand light curves within a few seconds.
  •  
23.
  • Ofek, E. O., et al. (författare)
  • A Six-year Image-subtraction Light Curve of SN 2010jl
  • 2019
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 131:999
  • Tidskriftsartikel (refereegranskat)abstract
    • SN 2010jl was a luminous Type Lin supernova (SN), detected in radio, optical, X-ray and hard X-rays. Here we report on its six-year R- and g-band light curves obtained using the Palomar Transient Factory. The light curve was generated using a pipeline based on the proper image-subtraction method and we discuss the algorithm performances. As noted before, the R-band light curve, up to about 300 days after maximum light is well described by a power-law decline with a power-law index of alpha approximate to -0.5. Between day 300 and day 2300 after maximum light, it is consistent with a power-law decline, with a power-law index of about alpha approximate to -3.4. The longevity of the light curve suggests that the massive circumstellar material around the progenitor was ejected on timescales of at least tens of years prior to the progenitor explosion.
  •  
24.
  • Phillips, M. M., et al. (författare)
  • Carnegie Supernova Project-II : Extending the Near-infrared Hubble Diagram for Type Ia Supernovae to z ∼ 0.1
  • 2019
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 131:995
  • Tidskriftsartikel (refereegranskat)abstract
    • The Carnegie Supernova Project-II (CSP-II) was an NSF-funded, four-year program to obtain optical and near-infrared observations of a Cosmology sample of similar to 100 Type. Ia supernovae located in the smooth Hubble flow (0.03 less than or similar to z less than or similar to 0.10). Light curves were also obtained of a Physics sample composed of 90 nearby Type. Ia supernovae at z <= 0.04 selected for near-infrared spectroscopic timeseries observations. The primary emphasis of the CSP-II is to use the combination of optical and near-infrared photometry to achieve a distance precision of better than 5%. In this paper, details of the supernova sample, the observational strategy, and the characteristics of the photometric data are provided. In a companion paper, the near-infrared spectroscopy component of the project is presented.
  •  
25.
  • Runnholm, Axel, et al. (författare)
  • The Lyman Alpha Spectral Database (LASD)
  • 2021
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 133:1021
  • Tidskriftsartikel (refereegranskat)abstract
    • Lyman alpha (Ly alpha) emission from star-forming galaxies is an important tool to study a large range of astrophysical questions: it has the potential to carry information about the source galaxy, its nearby circumgalactic medium, and also the surrounding intergalactic medium. Substantial observational and theoretical work has therefore focused on understanding the details of this emission line. These efforts have been hampered, however, by an absence of spectroscopic reference samples that can be used both as comparisons for observational studies and as critical tests for theoretical work. For this reason, we have compiled a large sample of Ly alpha spectra, at both low and high redshift, and created a publicly available online database, at lasdlyman-alpha.com. The Lyman Alpha Spectral Database (LASD) hosts these spectra, as well as a large set of spectral and kinematic quantities that have been homogeneously measured for the entire sample. As part of this we have developed an automated redshift determination algorithm which we show is accurate to within less than +/- 180 kms(-1) on average, across many different Ly alpha profiles. The measurements can conveniently be viewed online and downloaded in tabular form. The LASD has the capacity for users to easily upload their own Ly alpha spectra, and all the same spectral measurements will be made, reported, and ingested into the database. We actively invite the community to do so, and the LASD is intended to be a long-term community resource. In this paper we present the design of the database as well as descriptions of the underlying algorithms and the initial Ly alpha emitter samples that are in the database.
  •  
26.
  • Sako, Masao, et al. (författare)
  • The Data Release of the Sloan Digital Sky Survey-II Supernova Survey
  • 2018
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 130:988
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper describes the data release of the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey conducted between 2005 and 2007. Light curves, spectra, classifications, and ancillary data are presented for 10,258 variable and transient sources discovered through repeat ugriz imaging of SDSS Stripe 82, a 300 deg(2) area along the celestial equator. This data release is comprised of all transient sources brighter than r similar or equal to 22.5 mag with no history of variability prior to 2004. Dedicated spectroscopic observations were performed on a subset of 889 transients, as well as spectra for thousands of transient host galaxies using the SDSS-III BOSS spectrographs. Photometric classifications are provided for the candidates with good multi-color light curves that were not observed spectroscopically, using host galaxy redshift information when available. From these observations, 4607 transients are either spectroscopically confirmed, or likely to be, supernovae, making this the largest sample of supernova candidates ever compiled. We present a new method for SN host-galaxy identification and derive host-galaxy properties including stellar masses, star formation rates, and the average stellar population ages from our SDSS multi-band photometry. We derive SALT2 distance moduli for a total of 1364 SN. Ia with spectroscopic redshifts as well as photometric redshifts for a further 624 purely photometric SN. Ia candidates. Using the spectroscopically confirmed subset of the three-year SDSS-II SN. Ia sample and assuming a flat.CDM cosmology, we determine Omega(M) = 0.315 +/- 0.093 (statistical error only) and detect a non-zero cosmological constant at 5.7 sigma.
  •  
27.
  • Smith, K. W., et al. (författare)
  • Design and Operation of the ATLAS Transient Science Server
  • 2020
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 132:1014
  • Tidskriftsartikel (refereegranskat)abstract
    • The Asteroid Terrestrial impact Last Alert System (ATLAS) system consists of two 0.5 m Schmidt telescopes with cameras covering 29 square degrees at plate scale of 1.86 arcsec per pixel. Working in tandem, the telescopes routinely survey the whole sky visible from Hawaii (above delta > -50 degrees) every two nights, exposing four times per night, typically reaching o < 19 magnitude per exposure when the moon is illuminated and c < 19.5 magnitude per exposure in dark skies. Construction is underway of two further units to be sited in Chile and South Africa which will result in an all-sky daily cadence from 2021. Initially designed for detecting potentially hazardous near earth objects, the ATLAS data enable a range of astrophysical time domain science. To extract transients from the data stream requires a computing system to process the data, assimilate detections in time and space and associate them with known astrophysical sources. Here we describe the hardware and software infrastructure to produce a stream of clean, real, astrophysical transients in real time. This involves machine learning and boosted decision tree algorithms to identify extragalactic and Galactic transients. Typically we detect 10-15 supernova candidates per night which we immediately announce publicly. The ATLAS discoveries not only enable rapid follow-up of interesting sources but will provide complete statistical samples within the local volume of 100 Mpc. A simple comparison of the detected supernova rate within 100 Mpc, with no corrections for completeness, is already significantly higher (factor 1.5 to 2) than the current accepted rates.
  •  
28.
  • Tinyanont, S., et al. (författare)
  • Keck Infrared Transient Survey. I. Survey Description and Data Release 1
  • 2024
  • Ingår i: Publications of the Astronomical Society of the Pacific. - 0004-6280 .- 1538-3873. ; 136:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the Keck Infrared Transient Survey, a NASA Key Strategic Mission Support program to obtain near-infrared (NIR) spectra of astrophysical transients of all types, and its first data release, consisting of 105 NIR spectra of 50 transients. Such a data set is essential as we enter a new era of IR astronomy with the James Webb Space Telescope (JWST) and the upcoming Nancy Grace Roman Space Telescope (Roman). NIR spectral templates will be essential to search JWST images for stellar explosions of the first stars and to plan an effective Roman SN Ia cosmology survey, both key science objectives for mission success. Between 2022 February and 2023 July, we systematically obtained 274 NIR spectra of 146 astronomical transients, representing a significant increase in the number of available NIR spectra in the literature. Here, we describe the first release of data from the 2022A semester. We systematically observed three samples: a flux-limited sample that includes all transients <17 mag in a red optical band (usually ZTF r or ATLAS o bands); a volume-limited sample including all transients within redshift z < 0.01 (D ≈ 50 Mpc); and an SN Ia sample targeting objects at phases and light-curve parameters that had scant existing NIR data in the literature. The flux-limited sample is 39% complete (60% excluding SNe Ia), while the volume-limited sample is 54% complete and is 79% complete to z = 0.005. Transient classes observed include common Type Ia and core-collapse supernovae, tidal disruption events, luminous red novae, and the newly categorized hydrogen-free/helium-poor interacting Type Icn supernovae. We describe our observing procedures and data reduction using PypeIt, which requires minimal human interaction to ensure reproducibility.
  •  
29.
  • Usher, Christopher, et al. (författare)
  • Rubin Observatory LSST Stars Milky Way and Local Volume Star Clusters Roadmap
  • 2023
  • Ingår i: Publications of the Astronomical Society of the Pacific. - 0004-6280 .- 1538-3873. ; 135:1049
  • Tidskriftsartikel (refereegranskat)abstract
    • The Vera C. Rubin Observatory will undertake the Legacy Survey of Space and Time, providing an unprecedented, volume-limited catalog of star clusters in the Southern Sky, including Galactic and extragalactic star clusters. The Star Clusters subgroup of the Stars, Milky Way and Local Volume Working Group has identified key areas where Rubin Observatory will enable significant progress in star cluster research. This roadmap represents our science cases and preparation for studies of all kinds of star clusters from the Milky Way out to distances of tens of megaparsecs.
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30.
  • Wright, Gillian, et al. (författare)
  • The Mid-infrared Instrument for JWST and Its In-flight Performance
  • 2023
  • Ingår i: Publications of the Astronomical Society of the Pacific. - 0004-6280 .- 1538-3873. ; 135:1046
  • Tidskriftsartikel (refereegranskat)abstract
    • The Mid-Infrared Instrument (MIRI) extends the reach of the James Webb Space Telescope (JWST) to 28.5 μm. It provides subarcsecond-resolution imaging, high sensitivity coronagraphy, and spectroscopy at resolutions of λ/Δλ ∼ 100-3500, with the high-resolution mode employing an integral field unit to provide spatial data cubes. The resulting broad suite of capabilities will enable huge advances in studies over this wavelength range. This overview describes the history of acquiring this capability for JWST. It discusses the basic attributes of the instrument optics, the detector arrays, and the cryocooler that keeps everything at approximately 7 K. It gives a short description of the data pipeline and of the instrument performance demonstrated during JWST commissioning. The bottom line is that the telescope and MIRI are both operating to the standards set by pre-launch predictions, and all of the MIRI capabilities are operating at, or even a bit better than, the level that had been expected. The paper is also designed to act as a roadmap to more detailed papers on different aspects of MIRI.
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31.
  • Boldt, Luis N., et al. (författare)
  • Near-Infrared K Corrections of Type Ia Supernovae and their Errors
  • 2014
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 126:938, s. 324-337
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper we use near-infrared (NIR) spectral observations of Type Ia supernovae (SNe Ia) to study the uncertainties inherent in NIR K corrections. To do so, 75 previously published NIR spectra of 33 SNe Ia are employed to determine K-correction uncertainties in the YJHK(s) passbands as a function of temporal phase and redshift. The resultant K corrections are then fed into an interpolation algorithm that provides mean K corrections as a function of temporal phase and robust estimates of the associated errors. These uncertainties are both statistical and intrinsic-i.e., due to the diversity of spectral features from object to object and must be included in the overall error budget of cosmological parameters constrained through the use of NIR observations of SNe Ia. Intrinsic variations are likely the dominant source of error for all four passbands at maximum light. Given the present data, the total Y-band K-correction uncertainties at maximum are smallest, amounting to +/- 0.04 mag at a redshift of z = 0.08. The J-band K-term errors are also reasonably small (+/- 0.06 mag), but intrinsic variations of spectral features and noise introduced by telluric corrections in the H-band currently limit its total K-correction errors at maximum to +/- 0.10 mag at z = 0.08. Finally, uncertainties in the K-s-band K terms at maximum amount to +/- 0.07 mag at this same redshift. These results are largely constrained by the small number of published NIR spectra of SNe Ia, which do not yet allow spectral templates to be constructed as a function of the light curve decline rate.
  •  
32.
  • Bouchet, P., et al. (författare)
  • The Mid-Infrared Instrument for the James Webb Space Telescope, III: MIRIM, The MIRI Imager
  • 2015
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 127:953, s. 612-622
  • Tidskriftsartikel (refereegranskat)abstract
    • In this article, we describe the Mid-Infrared Imager Module (MIRIM), which provides broadband imaging in the 5-27 mu m wavelength range for the James Webb Space Telescope. The imager has a 0 ''.11 pixel scale and a total unobstructed view of 74 '' x 113 '' The remainder of its nominal 113 '' x 113 '' field is occupied by the coronagraphs and the low-resolution spectrometer. We present the instrument optical and mechanical design. We show that the test data, as measured during the test campaigns undertaken at CEA-Saclay, at the Rutherford Appleton Laboratory, and at the NASA Goddard Space Flight Center, indicate that the instrument complies with its design requirements and goals. We also discuss the operational requirements (multiple dithers and exposures) needed for optimal scientific utilization of the MIRIM.
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33.
  • Branch, David, et al. (författare)
  • Comparative direct analysis of type Ia supernova spectra. IV. Postmaximum
  • 2008
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 120:864, s. 135-149
  • Tidskriftsartikel (refereegranskat)abstract
    • A comparative study of optical spectra of Type Ia supernovae ( SNe Ia) obtained near 1 week, 3 weeks, and 3 months after maximum light is presented. Most members of the four groups that were defined on the basis of maximum light spectra in Paper II ( core normal, broad line, cool, and shallow silicon) develop highly homogeneous postmaximum spectra, although there are interesting exceptions. Comparisons with SYNOW synthetic spectra show that most of the spectral features can be accounted for in a plausible way. The fits show that 3 months after maximum light, when SN Ia spectra are often said to be in the nebular phase and to consist of forbidden emission lines, the spectra actually remain dominated by resonance- scattering features of permitted lines, primarily those of Fe II. Even in SN 1991bg, which is said to have made a very early transition to the nebular phase, there is no need to appeal to forbidden lines at 3 weeks postmaximum, and at 3 months postmaximum the only clear identification of a forbidden line is [Ca II]lambda lambda 7291, 7324. Recent studies of SN Ia rates indicate that most of the SNe Ia that have ever occurred have been "" prompt"" SNe Ia, produced by young (similar to 10(8) yr) stellar populations, while most of the SNe Ia that occur at low redshift today are "" tardy,"" produced by an older ( several Gyr) population. We suggest that the shallow silicon SNe Ia tend to be the prompt ones.
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34.
  • Clocchiatti, Alejandro, et al. (författare)
  • Late-time HST photometry of SN1994I : Hints of positron annihilation energy deposition
  • 2008
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 120:865, s. 290-300
  • Tidskriftsartikel (refereegranskat)abstract
    • We present multicolor Hubble Space Telescope ( HST) WFPC2 broadband observations of the Type Ic SN 1994I obtained similar to 280 d after maximum light. We measure the brightness of the SN and, relying on the detailed spectroscopic database of SN 1994I, we transform the ground-based photometry obtained at early times to the HST photometric system, deriving light curves for the WFPC2 F439W, F555W, F675W, and F814W passbands that extend from 7 days before to 280 days after maximum. We use the multicolor photometry to build a quasi-bolometric light curve of SN 1994I, and compare it with similarly constructed light curves of other supernovae. In doing so, we propose and test a scaling in energy and time that allows for a more meaningful comparison of the exponential tails of different events. Through comparison with models, we find that the late-time light curve of SN 1994I is consistent with that of spherically symmetric ejecta in homologous expansion, for which the ability to trap the gamma-rays produced by the radioactive decay of Co-56 diminishes roughly as the inverse of time squared. We also find that by the time of the HST photometry, the light curve was significantly energized by the annihilation of positrons.
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35.
  • Dent, W. R. F., et al. (författare)
  • GASPS-A Herschel Survey of Gas and Dust in Protoplanetary Disks: Summary and Initial Statistics
  • 2013
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 125:927, s. 477-505
  • Tidskriftsartikel (refereegranskat)abstract
    • We describe a large-scale far-infrared line and continuum survey of protoplanetary disk through to young debris disk systems carried out using the ACS instrument on the Herschel Space Observatory. This Open Time Key program, known as GASPS (Gas Survey of Protoplanetary Systems), targeted similar to 250 young stars in narrow wavelength regions covering the [OI] fine structure line at 63 mu m the brightest far-infrared line in such objects. A subset of the brightest targets were also surveyed in [OI]145 mu m, [CII] at 157 mu m, as well as several transitions of H2O and high-excitation CO lines at selected wavelengths between 78 and 180 mu m. Additionally, GASPS included continuum photometry at 70, 100 and 160 mu m, around the peak of the dust emission. The targets were SED Class II-III T Tauri stars and debris disks from seven nearby young associations, along with a comparable sample of isolated Herbig AeBe stars. The aim was to study the global gas and dust content in a wide sample of circumstellar disks, combining the results with models in a systematic way. In this overview paper we review the scientific aims, target selection and observing strategy of the program. We summarise some of the initial results, showing line identifications, listing the detections, and giving a first statistical study of line detectability. The [OI] line at 63 mu m was the brightest line seen in almost all objects, by a factor of similar to 10. Overall [OI]63 mu m detection rates were 49%, with 100% of HAeBe stars and 43% of T Tauri stars detected. A comparison with published disk dust masses (derived mainly from sub-mm continuum, assuming standard values of the mm mass opacity) shows a dust mass threshold for [OI] 63 mu m detection of similar to 10(-5) M-circle dot. Normalising to a distance of 140 pc, 84% of objects with dust masses >= 10(-5) M-circle dot can be detected in this line in the present survey; 32% of those of mass 10(-6)-10(-5) M-circle dot, and only a very small number of unusual objects with lower masses can be detected. This is consistent with models with a moderate UV excess and disk flaring. For a given disk mass, [OI] detectability is lower for M stars compared with earlier spectral types. Both the continuum and line emission was, in most systems, spatially and spectrally unresolved and centred on the star, suggesting that emission in most cases was from the disk. Approximately 10 objects showed resolved emission, most likely from outflows. In the GASPS sample, [OI] detection rates in T Tauri associations in the 0.3-4 Myr age range were similar to 50%. For each association in the 5-20 Myr age range, similar to 2 stars remain detectable in [OI]63 mu m, and no systems were detected in associations with age >20 Myr. Comparing with the total number of young stars in each association, and assuming a ISM-like gas/dust ratio, this indicates that similar to 18% of stars retain a gas-rich disk of total mass similar to 1 M-Jupiter for 1-4 Myr, 1-7% keep such disks for 5-10 Myr, but none are detected beyond 10-20 Myr. The brightest [OI] objects from GASPS were also observed in [OI]145 mu m, [CII]157 mu m and CO J = 18 - 17, with detection rates of 20-40%. Detection of the [CII] line was not correlated with disk mass, suggesting it arises more commonly from a compact remnant envelope.
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36.
  • Flicker, Ralf, et al. (författare)
  • Hokupa'a anisoplanatism and Mauna Kea turbulence characterization
  • 2002
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 1538-3873 .- 0004-6280. ; 114:799, s. 1006-1015
  • Tidskriftsartikel (refereegranskat)abstract
    • A data set of adaptive optics images has been analyzed in order to study the effects of angular anisoplanatism and to characterize Mauna Kea nighttime turbulence. The data set consists of a selection of Galactic center images obtained with the adaptive optics instrument Hokupa'a and the near-infrared camera QUIRC on the Gemini-North 8 m telescope. Using the Strehl ratio and the FWHM as tracers for anisoplanatism in the images, it is possible to draw conclusions about the effective turbulence height (h) over bar by model-fitting synthetic data. From the relatively small statistical sample, we obtain a median (h) over bar =3.5 km, with 10th and 90th percentiles being 2.2 and 5.6 km. The implications of these findings for a turbulence-conjugated adaptive optics system are addressed. We also find the Zernike modal equivalent of Hokupa'a to be Napproximate to18, i.e., on the average slightly better than 4 radial degrees.
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37.
  • Hernandez, Olivier, et al. (författare)
  • GHαFaS: Galaxy Hα Fabry-Perot System for the William Herschel Telescope
  • 2008
  • Ingår i: Publications of the Astronomical Society of the Pacific: PASP. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 120, s. 15-
  • Tidskriftsartikel (populärvet., debatt m.m.)abstract
    • GHαFaS, a new Fabry-Perot system, is now available at the William Herschel Telescope (WHT). It was mounted, for the first time, at the Nasmyth focus of the 4.2-m WHT on La Palma in 2007 July. Using modern technology, with a spectral resolution of the order R˜15,000, and with a seeing-limited spatial resolution, GHαFaS will provide a new look at the Hα-emitting gas over a 4.8' circular field in the nearby universe. Many science programs can be done on a 4.2-m class telescope in world-class seeing conditions with a scanning Fabry-Perot. Not only galaxies but H II regions, planetary nebulae, supernova remnants, and the diffuse interstellar medium are subjects for which unique data can be aquired rapidly. Astronomers from the Laboratoire d'Astrophysique Expérimentale (LAE) in Montréal, the Laboratoire d'Astrophysique de Marseille (LAM-OAMP), and the Instituto de Astrofísica de Canarias (IAC), have inaugurated GHαFaS by studying in detail the dynamics of some nearby spiral galaxies. A robust set of state-of-the-art tools for reducing and analyzing the data cubes obtained with GHαFaS has also been developed.
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38.
  • Johansson, Sveneric, et al. (författare)
  • Astrophysical Lasers with Radiation Pumping by Accidental Resonance
  • 2003
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 1538-3873 .- 0004-6280. ; 115:814, s. 1375-1382
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper we consider a general problem of astrophysical lasersoperating with optical pumping by accidental resonance (PAR) with strongspontaneous emission lines of other elements. The origin of populationinversion and the coefficient of amplification due to the opticalexcitation of atoms (ions) by a four-level scheme with PAR are analyzed.We elucidate conclusively the question of the manifestation ofastrophysical lasers in the optical region of the spectrum, which inprinciple differs from that of astrophysical masers in the microwaverange.
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39.
  • Kattner, ShiAnne, et al. (författare)
  • The Standardizability of Type Ia Supernovae in the Near-Infrared : Evidence for a Peak-Luminosity Versus Decline-Rate Relation in the Near-Infrared
  • 2012
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 124:912, s. 114-127
  • Tidskriftsartikel (refereegranskat)abstract
    • We analyze the standardizability of Type Ia supernovae (SNe Ia) in the near-infrared (NIR) by investigating the correlation between observed peak NIR (Y JH) absolute magnitude and postmaximum B-band decline rate [Delta m(15)(B)]. A sample of 27 low-redshift SNe Ia with well-observed NIR light curves observed by the Carnegie Supernova Project (CSP) between 2004 and 2007 is used. All 27 objects have premaximum coverage in optical bands, with a subset of 13 having premaximum NIR observations as well; coverage of the other 14 begins shortly after NIR maximum brightness. We describe the methods used to derive light-curve parameters (absolute peak magnitudes and decline rates) from both spline-and template-fitting procedures, and we confirm prior findings that fitting templates to SNe Ia light curves in the NIR is problematic due to the diversity of postmaximum behavior of objects that are characterized by similar Delta m(15)(B) values, especially at high decline rates. Nevertheless, we show that NIR light curves can be reasonably fit with a template, especially if the observations begin within 5 days after NIR maximum. SNe Ia appear to be better standardizable candles in the NIR bands than in the optical bands. For the subset of 13 objects in our data set that excludes the highly reddened and fast-declining SNe Ia and includes only those objects for which NIR observations began prior to 5 days after maximum light, we find modest (1.7 sigma) evidence for a peak-luminosity versus decline-rate relation in Y, and stronger evidence (2.8 sigma) in J and H. Using R-V values differing from the canonical value (R-V = 3.1) is shown to have little effect on the results. A Hubble diagram is presented for the NIR bands and the B band. The resulting scatter for the combined NIR bands is 0.13 mag, while the B band produces a scatter of 0.22 mag. Finally, we find evidence for a bimodal distribution in the NIR absolute magnitudes of fast-declining SNe Ia [Delta m(15)(B) > 1.7]. These data suggest that applying a correction to SNe Ia peak luminosities for decline rate is likely to be beneficial in the J and H bands to make SNe Ia more precise distance indicators, but of only marginal importance in the Y band.
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40.
  • Kessler, Richard, et al. (författare)
  • Results from the Supernova Photometric Classification Challenge
  • 2010
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 122:898, s. 1415-1431
  • Tidskriftsartikel (refereegranskat)abstract
    • We report results from the Supernova Photometric Classification Challenge (SNPhotCC), a publicly released mix of simulated supernovae (SNe), with types (Ia, Ibc, and II) selected in proportion to their expected rates. The simulation was realized in the griz filters of the Dark Energy Survey (DES) with realistic observing conditions (sky noise, point-spread function, and atmospheric transparency) based on years of recorded conditions at the DES site. Simulations of non-Ia-type SNe are based on spectroscopically confirmed light curves that include unpublished non-Ia samples donated from the Carnegie Supernova Project (CSP), the Supernova Legacy Survey (SNLS), and the Sloan Digital Sky Survey-II (SDSS-II). A spectroscopically confirmed subset was provided for training. We challenged scientists to run their classification algorithms and report a type and photo-z for each SN. Participants from 10 groups contributed 13 entries for the sample that included a host-galaxy photo-z for each SN and nine entries for the sample that had no redshift information. Several different classification strategies resulted in similar performance, and for all entries the performance was significantly better for the training subset than for the unconfirmed sample. For the spectroscopically unconfirmed subset, the entry with the highest average figure of merit for classifying SNe Ia has an efficiency of 0.96 and an SN Ia purity of 0.79. As a public resource for the future development of photometric SN classification and photo-z estimators, we have released updated simulations with improvements based on our experience from the SNPhotCC, added samples corresponding to the Large Synoptic Survey Telescope (LSST) and the SDSS-II, and provided the answer keys so that developers can evaluate their own analysis.
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41.
  • Rieke, G. H., et al. (författare)
  • The Mid-Infrared Instrument for the James Webb Space Telescope, I: Introduction
  • 2015
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 127:953, s. 584-594
  • Tidskriftsartikel (refereegranskat)abstract
    • MIRI (the Mid-Infrared Instrument for the James Webb Space Telescope [JWST]) operates from 5 to 28: 5 mu m and combines over this range: (1) unprecedented sensitivity levels; (2) subarcsecond angular resolution; (3) freedom from atmospheric interference; (4) the inherent stability of observing in space; and (5) a suite of versatile capabilities including imaging, low- and medium-resolution spectroscopy (with an integral field unit), and coronagraphy. We illustrate the potential uses of this unique combination of capabilities with various science examples: (1) imaging exoplanets; (2) transit and eclipse spectroscopy of exoplanets; (3) probing the first stages of star and planet formation, including identifying bioactive molecules; (4) determining star formation rates and mass growth as galaxies are assembled; and (5) characterizing the youngest massive galaxies.
  •  
42.
  • van Dishoeck, E. F., et al. (författare)
  • Water in Star-forming Regions with the Herschel Space Observatory (WISH). I. Overview of Key Program and First Results
  • 2011
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 123:900, s. 138-170
  • Tidskriftsartikel (refereegranskat)abstract
    • Water In Star-forming regions with Herschel (WISH) is a key program on the Herschel Space Observatory designed to probe the physical and chemical structures of young stellar objects using water and related molecules and to follow the water abundance from collapsing clouds to planet-forming disks. About 80 sources are targeted, covering a wide ranee of luminosities-from low ( 10(5) L-circle dot)-and a wide range of evolutionary stages-from cold prestellar cores to warm protostellar envelopes and outflows to disks around young stars. Both the HIFI and PACS instruments are used to observe a variety of lines of H2O, (H2O)-O-18 and chemically related species at the source position and in small maps around the protostars and selected outflow positions. In addition, high-frequency lines of CO, (CO)-C-13, and (CO)-O-18 are obtained with Herschel and are complemented by ground-based observations of dust continuum, HDO, CO and its isotopologs, and other molecules to ensure a self-consistent data set for analysis. An overview of the scientific motivation and observational strategy of the program is given, together with the modeling approach and analysis tools that have been developed. Initial science results are presented. These include a lack of water in cold gas at abundances that are lower than most predictions, strong water emission from shocks in protostellar environments, the importance of UV radiation in heating the gas along outflow walls across the full range of luminosities, and surprisingly widespread detection of the chemically related hydrides OH+ and H2O+ in outflows and foreground gas. Quantitative estimates of the energy budget indicate that H2O is generally not the dominant coolant in the warm dense gas associated with protostars. Very deep limits on the cold gaseous water reservoir in the outer regions of protoplanetary disks are obtained that have profound implications for our understanding of grain growth and mixing in disks.
  •  
43.
  • van Groningen, E., et al. (författare)
  • An algorithm for the relative scaling of spectra
  • 1992
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 104:678, s. 700-703703
  • Tidskriftsartikel (refereegranskat)abstract
    • A method is described for the automatic relative scaling of spectra in which one or more lines with constant flux are present. The algorithm takes into account differences in spectral resolution, flux factors, and spectral shifts. It was developed for the relative calibration of series of optical spectra obtained in variability studies of active galactic nuclei but it also can be used for other purposes, e.g., the subtraction of an underlying stellar continuum in AGN with a template spectrum. Tests show that a high degree of accuracy is obtained, and that the method is superior to scaling the spectra by eye or measuring narrow-band fluxes
  •  
44.
  • Wallerstein, George, et al. (författare)
  • Line Identifications in the Spectrum of eta Carinae as Observed in 1990-1991 with CCD Detectors
  • 2001
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 1538-3873 .- 0004-6280. ; 113:788, s. 1210-1214
  • Tidskriftsartikel (refereegranskat)abstract
    • We have used the Cerro Tololo Inter-American Observatory telescopes andspectrographs to record emission lines in eta Carinae from 3093 to8956 Å with a gap between 4432 and 5696 Å. A resolving powerof about 20,000 was used throughout. Accurate wavelengths, peakintensities relative to the local continuum, and line identificationsare presented. The data are briefly discussed with respect to the stateof ionization present, the presence of oxygen lines, and the use of [SII] lines to derive a lower limit on the local electron density. We alsotabulate the wavelengths of interstellar absorption lines and diffuseinterstellar bands.
  •  
45.
  • Way, Michael J., et al. (författare)
  • Can Self-Organizing Maps Accurately Predict Photometric Redshifts?
  • 2012
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 124:913, s. 274-279
  • Tidskriftsartikel (refereegranskat)abstract
    • We present an unsupervised machine-learning approach that can be employed for estimating photometric redshifts. The proposed method is based on a vector quantization called the self-organizing-map (SOM) approach. A variety of photometrically derived input values were utilized from the Sloan Digital Sky Survey's main galaxy sample, luminous red galaxy, and quasar samples, along with the PHAT0 data set from the Photo-z Accuracy Testing project. Regression results obtained with this new approach were evaluated in terms of root-mean-square error (RMSE) to estimate the accuracy of the photometric redshift estimates. The results demonstrate competitive RMSE and outlier percentages when compared with several other popular approaches, such as artificial neural networks and Gaussian process regression. SOM RMSE results (using Delta z = z(phot) - z(spec)) are 0.023 for the main galaxy sample, 0.027 for the luminous red galaxy sample, 0.418 for quasars, and 0.022 for PHAT0 synthetic data. The results demonstrate that there are nonunique solutions for estimating SOM RMSEs. Further research is needed in order to find more robust estimation techniques using SOMs, but the results herein are a positive indication of their capabilities when compared with other well-known methods.
  •  
46.
  • Wells, M., et al. (författare)
  • The Mid-Infrared Instrument for the James Webb Space Telescope, VI: The Medium Resolution Spectrometer
  • 2015
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 127:953, s. 646-664
  • Tidskriftsartikel (refereegranskat)abstract
    • We describe the design and performance of the Medium Resolution Spectrometer (MRS) for the JWST-MIRI instrument. The MRS incorporates four coaxial spectral channels in a compact opto-mechanical layout that generates spectral images over fields of view up to 7.7 x 7.7 '' in extent and at spectral resolving powers ranging from 1300 to 3700. Each channel includes an all-reflective integral field unit (IFU): an "image slicer" that reformats the input field for presentation to a grating spectrometer. Two 1024 x 1024 focal plane detector arrays record the output spectral images with an instantaneous spectral coverage of approximately one third of the full wavelength range of each channel. The full 5-28.5 mu m spectrum is then obtained by making three exposures using gratings and pass-band-determining filters that are selected using just two three-position mechanisms. The expected on-orbit optical performance is presented, based on testing of the MIRI Flight Model and including spectral and spatial coverage and resolution. The point spread function of the reconstructed images is shown to be diffraction limited and the optical transmission is shown to be consistent with the design expectations.
  •  
47.
  • Wright, G. S., et al. (författare)
  • The Mid-Infrared Instrument for the James Webb Space Telescope, II: Design and Build
  • 2015
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 127:953, s. 595-611
  • Tidskriftsartikel (refereegranskat)abstract
    • The Mid-InfraRed Instrument (MIRI) on the James Webb Space Telescope (JWST) provides measurements over the wavelength range 5 to 28: 5 mu m. MIRI has, within a single "package," four key scientific functions: photometric imaging, coronagraphy, single-source low-spectral resolving power (R similar to 100) spectroscopy, and medium-resolving power (R similar to 1500 to 3500) integral field spectroscopy. An associated cooler system maintains MIRI at its operating temperature of
  •  
48.
  • Wright, J. T., et al. (författare)
  • The Exoplanet Orbit Database
  • 2011
  • Ingår i: Publications of the Astronomical Society of the Pacific. - 0004-6280 .- 1538-3873. ; 123:902, s. 412-422
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a database of well-determined orbital parameters of exoplanets, and their host stars' properties. This database comprises spectroscopic orbital elements measured for 427 planets orbiting 363 stars from radial velocity and transit measurements as reported in the literature. We have also compiled fundamental transit parameters, stellar parameters, and the method used for the planets discovery. This Exoplanet Orbit Database includes all planets with robust, well measured orbital parameters reported in peer-reviewed articles. The database is available in a searchable, filterable, and sortable form online through the Exoplanets Data Explorer table, and the data can be plotted and explored through the Exoplanet Data Explorer plotter. We use the Data Explorer to generate publication-ready plots, giving three examples of the signatures of exoplanet migration and dynamical evolution: We illustrate the character of the apparent con-elation between mass and period in exoplanet orbits, the different selection biases between radial velocity and transit surveys, and that the multiplanet systems show a distinct semimajor-axis distribution from apparently singleton systems.
  •  
49.
  • Eversberg, T, et al. (författare)
  • The William-Wehlau Spectropolarimeter: Observing hot stars in all four Stokes parameters
  • 1998
  • Ingår i: PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC. - : ASTRONOMICAL SOC PACIFIC. - 0004-6280. ; 110:753, s. 1356-1369
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • We introduce a new polarimeter unit, which, mounted at the Cassegrain focus of any telescope and fiber-connected to a fixed CCD spectrograph, is able to measure all Stokes parameters I, Q, U, and V across spectral Lines of bright stellar targets and other
  •  
50.
  • Jones, Amy M., et al. (författare)
  • SDSS-IV from 2014 to 2016 : A Detailed Demographic Comparison over Three Years
  • 2023
  • Ingår i: Publications of the Astronomical Society of the Pacific. - 0004-6280. ; 135:1054
  • Tidskriftsartikel (refereegranskat)abstract
    • The Sloan Digital Sky Survey (SDSS) is one of the largest international astronomy organizations. We present demographic data based on surveys of its members from 2014, 2015 and 2016, during the fourth phase of SDSS (SDSS-IV). We find about half of SDSS-IV collaboration members were based in North America, a quarter in Europe, and the remainder in Asia and Central and South America. Overall, 26%-36% are women (from 2014 to 2016), up to 2% report non-binary genders. 11%-14% report that they are racial or ethnic minorities where they live. The fraction of women drops with seniority, and is also lower among collaboration leadership. Men in SDSS-IV were more likely to report being in a leadership role, and for the role to be funded and formally recognized. SDSS-IV collaboration members are twice as likely to have a parent with a college degree, than the general population, and are ten times more likely to have a parent with a PhD. This trend is slightly enhanced for female collaboration members. Despite this, the fraction of first generation college students is significant (31%). This fraction increased among collaboration members who are racial or ethnic minorities (40%-50%), and decreased among women (15%-25%). SDSS-IV implemented many inclusive policies and established a dedicated committee, the Committee on INclusiveness in SDSS. More than 60% of the collaboration agree that the collaboration is inclusive; however, collaboration leadership more strongly agree with this than the general membership. In this paper, we explain these results in full, including the history of inclusive efforts in SDSS-IV. We conclude with a list of suggested recommendations based on our findings, which can be used to improve equity and inclusion in large astronomical collaborations, which we argue is not only moral, but will also optimize their scientific output.
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