- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Enhancing the H <sub/>2</sub> O Megamaser Detection Rate Using Optical and Mid-infrared Photometry
摘要： Water megamasers from circumnuclear disks in galaxy centers provide the most accurate measurements of supermassive black hole masses and uniquely probe the subparsec accretion processes. At the same time, these systems offer independent crucial constraints of the Hubble constant in the nearby universe, and thus, the arguably best single constraint on the nature of dark energy. The chances of finding these golden standards are, however, abysmally low, at ～3% overall for any level of water maser emission detected at 22 GHz and ～1% for those exhibiting disk-like configuration. We provide here a thorough summary of the current state of detection of water megamaser disks along with a novel investigation of the likelihood of increasing their detection rates based on a multivariate parameter analysis of the optical and mid-infrared (mid-IR) photometric properties of the largest database of galaxies surveyed for 22 GHz emission. We find that galaxies with water megamaser emission tend to be associated with strong emission in all Wide-field Infrared Survey Explorer mid-IR wavelengths, with the strongest enhancement in the W4 band, at 22 μm, as well as with previously proposed and newly found indicators of active galactic nucleus strength in the mid-IR, such as red W1?W2 and W1?W4 colors, and the integrated mid-IR luminosity of the host galaxy. These trends offer a potential boost of the megamaser detection rates to 6%–15%, or a factor of 2–8 relative to the current rates, depending on the chosen sample selection criteria, while fostering real chances for discovering ～20 new megamaser disks.
关键词： infrared: galaxies,surveys,galaxies: nuclei,galaxies: active,masers
更新于2025-09-10 09:29:36
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High density fiber postitioner system for massive spectroscopic surveys
摘要： We describe here a novel design of a fast high-density robotized fiber positioner system for massive spectroscopic surveys. The fiber positioners are compact, robust, and they can be coordinated, allowing for a high spatial density. Furthermore, the high absolute accuracy removes the need for a metrology system and reduces the reconfiguration time. First, we present the requirements for such a high-density fiber positioner system and put them in relation with the science goals. Then, we discuss the positioner design that accomplishes these requirements (including mechanical design, local control electronics board, overall communication solution, and observation sequencing). Finally, the performance of the proposed design is measured using 25 mm pitch prototypes of the positioners, through a dedicated novel designed test-bench. The related results show that our prototypes fulfil the requirements particularly in terms of positioning precision (<20 μm rms for one single open loop move) and partially in tilt (<0.15 deg).
关键词： cosmology: observations,telescopes,techniques: spectroscopic,surveys,large-scale structure of Universe,dark energy
更新于2025-09-10 09:29:36
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Evaluating the service quality of solar product companies using SERVQUAL model
摘要： Purpose – This study aims to consider a five-factor model to evaluate the service quality of solar product companies in the context of rural Punjab (India) and validate the proposed model. In addition, the study considered the factors which affect the service quality of solar product companies. Design/methodology/approach – A five-factor model of service quality has been tested for reliability and validity by confirmatory factor analysis. For determining satisfaction of the solar product users, SERVQUAL model/gap analysis has been applied. Five dimensions, namely tangibility, reliability, responsiveness, assurance and empathy have been considered to assess the overall satisfaction level. A modified scale of Parasuraman incorporated in 1985 has been used as a survey instrument for research. A sample size of 345 solar submersible pump users was selected. Findings – The study concluded that dimensions such as reliability, responsiveness, assurance and empathy have lesser gap. The major gap has been found in the tangibility dimension which includes variables like modern design of solar energy products, facilities and attractiveness, variety of solar products and performance of solar products, etc. Research limitations/implications – As primary data are concerned, the biasness of the respondents may affect the results of the study. The survey has been conducted in the Punjab region, and a sample size is 345 only which may not reflect the broader picture. Practical implications – Solar energy has huge benefits in the Indian agriculture sector. The erratic state of power supply in India casts important costs on agriculture productivity. One such segment concerns systems, an important input for agriculture production. The study has implications for solar energy product manufacturers, as it makes them aware about customer perception toward services of solar product companies. Social implications – To decrease pollution and to save the environment, solar energy technologies have a good potential energy source and to meet the global energy demand, as it is the most promising and reliable energy source. Originality/value – The existing studies in the context of service quality of solar product companies in Punjab have been majorly confined to proposing key drivers toward adoption of renewable energy sources. By providing an insight into the satisfaction level of farmers for solar submersible pumps, the proposed study attempts to fill the gap. As the study relates to solar product users in rural Punjab, the findings will be of additional value to solar product companies which are manufacturing solar products. Therefore, it is expected that this research will fill the gap in literature by studying empirically the service quality of solar product companies.
关键词： Surveys,Confirmatory factor analysis,Energy sector,Solar energy,Solar energy products,Factor analysis
更新于2025-09-10 09:29:36
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NELIOTA: The wide-field, high-cadence, lunar monitoring system at the prime focus of the Kryoneri telescope
摘要： We present the technical specifications and first results of the ESA-funded, lunar monitoring project "NELIOTA" (NEO Lunar Impacts and Optical TrAnsients) at the National Observatory of Athens, which aims to determine the size-frequency distribution of small near-Earth objects (NEOs) via detection of impact flashes on the surface of the Moon. For the purposes of this project a twin camera instrument was specially designed and installed at the 1.2 m Kryoneri telescope utilizing the fast-frame capabilities of scientific Complementary Metal-Oxide Semiconductor detectors (sCMOS). The system provides a wide field-of-view (17.0'×14.4') and simultaneous observations in two photometric bands (R and I), reaching limiting magnitudes of 18.7 mag in 10 s in both bands at a 2.5 signal-to-noise ratio (S/N) level. This makes it a unique instrument that can be used for the detection of NEO impacts on the Moon, as well as for any astronomy projects that demand high-cadence multicolor observations. The wide field-of-view ensures that a large portion of the Moon is observed, while the simultaneous, high-cadence, monitoring in two photometric bands makes possible the determination of the temperatures of the impacts on the Moon’s surface and the validation of the impact flashes from a single site. Considering the varying background level on the Moon’s surface we demonstrate that the NELIOTA system can detect NEO impact flashes at a 2.5 S/N level of ～12.4 mag in the I-band and R-band for observations made at low lunar phases (～0.1). We report 31 NEO impact flashes detected during the first year of the NELIOTA campaign. The faintest flash was at 11.24 mag in the R-band (about two magnitudes fainter than ever observed before) at lunar phase 0.32. Our observations suggest a detection rate of 1.96 × 10?7 events km?2 h?1.
关键词： Moon,telescopes,techniques: miscellaneous,instrumentation: detectors,surveys
更新于2025-09-09 09:28:46
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The VIMOS Ultra-Deep Survey: ~10?000 galaxies with spectroscopic redshifts to study galaxy assembly at early epochs 2 < <i>z</i> ? 6
摘要： We present the VIMOS Ultra Deep Survey (VUDS), a spectroscopic redshift survey of ～10 000 very faint galaxies to study the main phase of galaxy assembly in 2 < z (cid:4) 6. The survey covers 1 deg2 in three separate ?elds: COSMOS, ECDFS, and VVDS-02h, with the selection of targets based on an inclusive combination of photometric redshifts and colour properties. Spectra covering 3650 < λ < 9350 ? are obtained with VIMOS on the ESO-VLT with integration times of 14h. Here we present the survey strategy, target selection, data processing, and the redshift measurement process with an emphasis on the speci?c methods used to adapt to this high-redshift range. We discuss the spectra quality and redshift reliability and derive a success rate in redshift measurement of 91%, or 74% by limiting the dataset to the most reliable measurements, down to a limiting magnitude iAB = 25. Measurements are performed all the way down to iAB = 27. The mean redshift of the main sample is z ～ 3 and extends over a broad redshift range mainly in 2 < z < 6. At 3 < z < 5, the galaxies cover a wide range of luminosities ?23 < MNUV < ?20.5, stellar mass 109 M(cid:5) < M? < 1011 M(cid:5), and star formation rates 1 M(cid:5)/yr < SFR < 103 M(cid:5)/yr. We discuss the spectral properties of galaxies using individual as well as stacked spectra. The comparison between spectroscopic and photometric redshifts as well as colour selection demonstrate the e?ectiveness of our selection scheme. From about ～90% of the data analysed so far, we expect to assemble >6000 galaxies with reliable spectroscopic redshifts in 2 < z < 6 when complete. This makes the VUDS the largest survey at these redshifts and o?ers the opportunity for unprecedented studies of the star-forming galaxy population and its distribution in large-scale structures during the main phase of galaxy assembly.
关键词： cosmology: observations,galaxies: formation,galaxies: evolution,surveys,large-scale structure of Universe,galaxies: high-redshift
更新于2025-09-04 15:30:14
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Surface photometry of WINGS galaxies with GASPHOT
摘要： Aims. We present the B, V, and K band surface photometry catalogs obtained by running the automatic software GASPHOT on galaxies from the WINGS cluster survey with isophotal areas larger than 200 pixels. The catalogs can be downloaded at the Centre de Données Astronomiques de Strasbourg. Methods. The luminosity growth curves of stars and galaxies in a given catalog relative to a given cluster image were obtained simultaneously by slicing the image with a fixed surface brightness step in several SExtractor runs. Then, using a single Sersic law convolved with a space-varying point spread function (PSF), GASPHOT performed a simultaneous χ2 best-fit of the major- and minor-axis luminosity growth curves of galaxies. We outline the GASPHOT performances and compare our surface photometry with that obtained by SExtractor, GALFIT, and GIM2D. This analysis is aimed at providing statistical information about the accuracy that is generally achieved by the softwares for automatic surface photometry of galaxies. Results. The GASPHOT catalogs provide the parameters of the Sersic law that fit the luminosity profiles for each galaxy and for each photometric band. They are the sky coordinates of the galaxy center (RA, Dec), the total magnitude (m), the semi-major axis of the effective isophote (Re), the Sersic index (n), the axis ratio (b/a), and a flag parameter (QFLAG) that generally indicates the fit quality. The WINGS-GASPHOT database includes 41 463 galaxies in the B band, 42 275 in the V band, and 71 687 in the K band. The bright early-type galaxies have higher Sersic indices and larger effective radii, as well as redder colors in their center. In general, the effective radii increase systematically from the K to the V and B band. Conclusions. The GASPHOT photometry agrees well with the surface photometry obtained by GALFIT and GIM2D, and with the aperture photometry provided by SExtractor. In particular, the direct comparison of structural parameters derived by different softwares for common galaxies indicates that the systematic differences are small in general. The only significant deviations are most likely due to the peculiar (and very accurate) image processing adopted by WINGS for large galaxies. The main advantages of GASPHOT with respect to other tools are (i) the automatic finding of the local PSF; (ii) the short CPU execution time; and (iii) the remarkable stability against the choice of the initial-guess parameters. All these characteristics make GASPHOT an ideal tool for blind surface photometry of large galaxy samples in wide-field CCD mosaics.
关键词： surveys,catalogs,galaxies: clusters: general
更新于2025-09-04 15:30:14
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The OmegaWhite survey for short-period variable stars – III: follow-up photometric and spectroscopic observations
摘要： We present photometric and spectroscopic follow-up observations of short-period variables discovered in the OmegaWhite survey, a wide-field high-cadence g-band synoptic survey targeting the Galactic Plane. We have used fast photometry on the SAAO 1.0- and 1.9-m telescopes to obtain light curves of 27 variables, and use these results to validate the period and amplitude estimates from the OmegaWhite processing pipeline. Furthermore, 57 sources (44 unique, 13 with new light curves) were selected for spectroscopic follow-up using either the SAAO 1.9-m telescope or the Southern African Large Telescope. We find that many of these variables have spectra which are consistent with being δ Scuti-type pulsating stars. At higher amplitudes, we detect four possible pulsating white dwarf/subdwarf sources and an eclipsing cataclysmic variable. Due to their rarity, these targets are ideal candidates for detailed follow-up studies. From spectroscopy, we confirm the symbiotic binary star nature of two variables identified as such in the SIMBAD database. We also report what could possibly be the first detection of the ‘Bump Cepheid’ phenomena in a δ Scuti star, with OW J175848.21–271653.7 showing a pronounced 22 per cent amplitude dip lasting 3 min during each pulsational cycle peak. However, the precise nature of this target is still uncertain as it exhibits the spectral features of a B-type star.
关键词： techniques: photometric,Galaxy: bulge,binaries: close,methods: observational,methods: data analysis,surveys
更新于2025-09-04 15:30:14
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Revised Exoplanet Radii and Habitability Using <i>Gaia</i> Data Release 2
摘要： Accurate stellar properties are crucial for determining exoplanet characteristics. Gaia DR2 presents revised distances, luminosities, and radii for 1.6 billion stars. Here, we report the calculation of revised radii and densities for 320 non-Kepler exoplanets using this data and present updated calculations of the incident ?ux received by 690 known exoplanets. This allows us to reassess the likelihood that those planets orbit in the habitable zone of their host stars. As a result of this analysis, three planets can be added to the catalog of potentially habitable worlds: HIP?67537?b, HD?148156?b, and HD?106720?b. In addition, the changed parameterization of BD?+49?898 means that its planet, BD?+49?898?b, now receives an incident ?ux that places it outside the optimistic habitable zone region, as de?ned by Kopparapu et al. We ?nd that use of the new Gaia data results in a mean increase in the calculated exoplanet radius of 3.76%. Previously, CoRoT-3 b had been reported as having the highest density of all known exoplanets. Here, we use updated information to revise the calculated density of CoRoT-3?b from 26.4 to 16.1?±?3.98 g cm?3. We also report in our data set, KELT-1?b, with a density of 22.1+5.62?9.16 g cm?3. Overall, our results highlight the importance of ensuring the parameterizations of known exoplanets are revisited whenever signi?cant improvements are made to the precision of the stellar parameters upon which they are based.
关键词： planets and satellites: fundamental parameters,astrobiology,planets and satellites: general,surveys,catalogs
更新于2025-09-04 15:30:14
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Remote Sensing Is Changing Our View of the Coast: Insights from 40 Years of Monitoring at Narrabeen-Collaroy, Australia
摘要： Narrabeen-Collaroy Beach, located on the Northern Beaches of Sydney along the Pacific coast of southeast Australia, is one of the longest continuously monitored beaches in the world. This paper provides an overview of the evolution and international scientific impact of this long-term beach monitoring program, from its humble beginnings over 40 years ago using the rod and tape measure Emery field survey method; to today, where the application of remote sensing data collection including drones, satellites and crowd-sourced smartphone images, are now core aspects of this continuing and much expanded monitoring effort. Commenced in 1976, surveying at this beach for the first 30 years focused on in-situ methods, whereby the growing database of monthly beach profile surveys informed the coastal science community about fundamental processes such as beach state evolution and the role of cross-shore and alongshore sediment transport in embayment morphodynamics. In the mid-2000s, continuous (hourly) video-based monitoring was the first application of routine remote sensing at the site, providing much greater spatial and temporal resolution over the traditional monthly surveys. This implementation of video as the first of a now rapidly expanding range of remote sensing tools and techniques also facilitated much wider access by the international research community to the continuing data collection program at Narrabeen-Collaroy. In the past decade the video-based data streams have formed the basis of deeper understanding into storm to multi-year response of the shoreline to changing wave conditions and also contributed to progress in the understanding of estuary entrance dynamics. More recently, ‘opportunistic’ remote sensing platforms such as surf cameras and smartphones have also been used for image-based shoreline data collection. Commencing in 2011, a significant new focus for the Narrabeen-Collaroy monitoring program shifted to include airborne lidar (and later Unmanned Aerial Vehicles (UAVs)), in an enhanced effort to quantify the morphological impacts of individual storm events, understand key drivers of erosion, and the placing of these observations within their broader regional context. A fixed continuous scanning lidar installed in 2014 again improved the spatial and temporal resolution of the remote-sensed data collection, providing new insight into swash dynamics and the often-overlooked processes of post-storm beach recovery. The use of satellite data that is now readily available to all coastal researchers via Google Earth Engine continues to expand the routine data collection program and provide key insight into multi-decadal shoreline variability. As new and expanding remote sensing technologies continue to emerge, a key lesson from the long-term monitoring at Narrabeen-Collaroy is the importance of a regular re-evaluation of what data is most needed to progress the science.
关键词： Argus,CoastSnap,Google Earth Engine,surfcams,Unmanned Aerial Vehicle,coastal imaging,lidar,RTK-GPS surveys
更新于2025-09-04 15:30:14