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1.
To investigate the environmental dependence of u ‐, g ‐, r ‐, i ‐, and z ‐band luminosities, we perform comparative studies of luminosity distributions between galaxy members of compact groups (CGs) and isolated galaxies. It is found that for the r, i, and z bands isolated galaxies have a higher proportion of faint galaxies and a lower proportion of luminous galaxies than galaxy members of CGs, but for the u band an opposite trend is observed. The correlation between the g ‐band luminosity and the environment has different trends in different luminosity regions (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

2.
We present a new formula for absolute magnitude determination for late‐type dwarf stars as a function of (g – r) and (r – i) for Sloan photometry. The absolute magnitudes estimated by this approach are brighter than those estimated by colour‐magnitude diagrams, and they reduce the luminosity function rather close to the luminosity function of Hipparcos. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

3.
This paper is the second in a series describing the southern Galactic Disk Survey (GDS) performed at the Univer‐sitätssternwarte Bochum near Cerro Armazones in Chile. Haas et al. (2012, Paper I) presented the survey design and the characteristics of the observations and data. They identified ∼2200 variable stars in an area of 50 square degrees with more than 50 observations in 2011. Here we present the first complete version of the GDS covering all 268 fields with 1323 square degrees along the Galactic disk including revised data from Paper I. The individual fields were observed up to 272 times and comprise a maximum time span between September 2010 and May 2015. We detect a total of 64 151 variable sources, which are presented in a catalog including some of their properties and their light curves. A comparison with the International Variable Star Index (VSX) and All Sky Automated Survey (ASAS) indicates that 56794 of these sources are previously unknown variables. Furthermore, we present U, B, V, r ′, i ′, z ′ photometry for all sources within the GDS, resulting in a new multi‐color catalog of nearly 16×106 sources detected in at least one filter. Both the GDS and the near‐infrared VISTA Variables in the Via Lactea survey (VVV) complement each other in the overlap area of about 300 square degrees enabling future comparison studies. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

4.
For an understanding of Galactic stellar populations in the SDSS filter system well defined stellar samples are needed. The nearby stars provide a complete stellar sample representative for the thin disc population. We compare the filter transformations of different authors applied to the main sequence stars from F to K dwarfs to SDSS filter system and discuss the properties of the main sequence. The location of the mean main sequence in colour‐magnitude diagrams is very sensitive to systematic differences in the filter transformation. A comparison with fiducial sequences of star clusters observed in g ′, r ′, and i ′ show good agreement. Theoretical isochrones from Padua and from Dartmouth have still some problems, especially in the (r – i) colours. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

5.
In 2013–2015 the Laboratory of spectroscopy and photometry of extragalactic objects (LS-PEO) of the Special Astrophysical Observatory together with Armenian specialists upgraded the 1-m Schmidt telescope of the Byurakan Astrophysical Observatory of the National Academy of Sciences of Armenia. We completely redesigned the control system of the telescope: we replaced the actuating mechanisms, developed telescope control software, and made the guiding system. We reworked and prepared a 4k × 4k Apogee (USA) liquid-cooled CCD with RON ~ 11.1 e?, a pixel size of 0.″868, and field of view of about 1□°, and in October 2015 mounted it in the focus of the telescope. The detector is equipped with a turret bearing 20 intermediate-band filters (FWHM = 250 Å) uniformly covering the 4000–9000 Å wavelength range, five broadband filters (u, g, r, i, z SDSS), and three narrow-band filters (5000 Å, 6560 Å and 6760 Å, FWHM = 100 Å). During the first year of test operation of the 1-m telescope we performed pilot observations within the framework of three programs: search for young stellar objects, AGNevolution, and stellar composition of galaxy disks.We confirmed the possibility of efficiently selecting of young objects using observations performed in narrow-band Hα and [SII] filters and the intermediate-band 7500 Å filter. Three-hours long exposures with SDSS g-, r-, and i-band filters allow us to reach the surface brightness level of 28m/□″ when investigating the stellar content of galaxy disks for a sample of nine galaxies. We used observations performed with the 1-m telescope in five broadband (SDSS u, g, r, i, and z) and 15 intermediate-band filters (4000–7500 Å) to construct a sample of quasar candidates with 0.5 < z < 5 (330 objects) in about one-sq. degree SA68 field complete down to RAB = 23m. Spectroscopic observations of 29 objects (19.m5 < R < 22m) carried out at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences confirmed the quasar nature of 28 objects.  相似文献   

6.
We present CCD photometry of 16 Abell clusters and one cluster candidate found in POSS-II field 861. The images were taken at the 0.9 m Telescope at Cerro Tololo, in the g, r and i filters of the Gunn–Thuan system. We tested the idea proposed by Garilli et al. (1996) that there is a population of unusually red galaxies which could be associated with either the field or clusters. Garilli et al. (1996) suggest that these galaxies have anomalously red colours, but we find that these objects are all near the limiting magnitude of the images (20m<r<22m) and have colours that are consistent with those expected for stars or field galaxies at z∼0.7. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

7.
We report the discovery of a bright blue quasar: SDSS J022218.03–062511.1. This object was discovered spectroscopically while searching for hot white dwarfs that may be used as calibration sources for large sky surveys such as the Dark Energy Survey or the Large Synoptic Survey Telescope project. We present the calibrated spectrum, spectral line shifts and report a redshift of z = 0.521±0.0015 and a rest‐frame g‐band luminosity of 8.71×1011 L⊙. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

8.
Using two volume-limited Main galaxy samples of the Sloan Digital Sky Survey Data Release 6 (SDSS DR6), we have explored the difference of the environmental dependence of u-, g-, r-, i-, and z-band luminosities between galaxies above and below the value of M r*. It turns out that in the luminous volume-limited sample, all the five band luminosities strongly correlate with local environments. Because the u-band luminosity of galaxies still strongly depends on local environments in the faint volumelimited sample, we conclude that M r* is not an important characteristic parameter for the environmental dependence of the u-band luminosity. It is worth noting that for the u-band, the subsample at low density has a higher proportion of luminous galaxies and a lower proportion of faint galaxies than the one at high density, which is opposite to widely accepted conclusion: luminous galaxies exist preferentially in the densest regions of the universe, but faint galaxies are located preferentially in low density regions. Our results show that the environmental dependence of luminosity is not a single trend in different luminosity regions and for different bands.  相似文献   

9.
We present the first-look analysis of the high-speed multicolour photometry of the bright V361 Hya-type star EO?Ceti (m V=12.3). The observations were gathered with the three-channel ULTRACAM instrument attached to the 4.2-m William Herschel Telescope. The data set has a total time span of 6.2?d and consists of 31 h simultaneous three colour photometry. The main power regions in all three colours are the same as previously reported in the white light photometric campaigns on EO?Ceti. We calculate the frequencies, amplitudes and phases of the significant modes in three colours of the SDSS system, r′, g′ and u′. The amplitudes of the detected modes are the highest in the u′ lightcurve, and the phases are the same in all three colours within the measurement accuracy. The amplitudes of the highest signal-to-noise modes show time variability in all three colours. We analyse the amplitude and phase variations of the five highest signal-to-noise modes in different colours. Even though the amplitudes show variations from night to night, the amplitude ratios are found to be constant to within 2σ level. This result is promising as it allows us to compare the observed amplitude ratios with theoretically calculated amplitude ratios. This may further constrain the mode identification of the highest amplitude modes in EO?Ceti and let us test the proposed seismic and binary evolution models.  相似文献   

10.
We present BVIc photometry of the brightest stars andcompact star clusters in NGC 2976, a dwarf galaxy in the interacting M81/M82 group. Deep CCD images of the galaxy were obtained with the 6m‐Telescope of the Special Astrophysical Observatory (Russia) at arcsec resolution. About 290 young stars and concentrated young clusters were measured. Supplementary data in the ultraviolet are taken from the literature. The extinction to the measured objects is comparatively low, E(B — V) ∼ 0.15 .. 0.20 mag. We estimate the ages of youngest resolved stars and concentrated star clusters to be ∼5 · 106 years. This population is concentrated in a broad stripe facing M81. In the central disk the population is a bit older, about 8 · 106 years, this may be a hint to an outward spreading star formation process. The metallicity of the disk population is estimatedas solar (z ∼ 0.02) from a fitting to Padova theoretical stellar isochrones.  相似文献   

11.
地基光学天文望远镜是人类探索与研究宇宙的重要手段, 对已有地基光学台址的光学观测环境进行监测分析, 可以为后期设备针对性改造以及观测者调整观测策略提供参考依据, 对提升地基光学设备的观测效能具有重要的意义. 吉林天文观测基地(简称``基地'')隶属于中国科学院国家天文台长春人造卫星观测站, 位于吉林省吉林市大绥河镇小绥河村南沟约5 km处(东经126.3\circ, 北纬43.8\circ, 海拔高度313m). 基地大气视宁度均值范围约为1.3$''$--1.4$''$、天顶附近V波段的天光背景亮度为20.64magcdotarcsec-2、年晴夜数最高可达270余天, 具有良好的天文观测条件. 吉林天文观测基地于2016年投入运行, 现有1.2m光电望远镜、迷你光电阵列望远镜、大视场光电望远镜阵列、新型多功能阵列结构光电探测平台等多台(套)光电望远镜设备. 利用上述设备, 主要围绕空间目标探测与识别、精密轨道确定、光电探测新方法以及变源天体的多色测光等开展相关研究工作, 与多家国内高校及科研院所保持着良好的合作关系.  相似文献   

12.
Online Digitized Sky Survey (DSS) material is often used to obtain information on newly discovered variable stars for older epochs (e.g. Nova progenitors, flare stars, etc.). We present here the results of an investigation of photometry on online DSS material in small fields calibrated by CCD sequences. We compared different source extraction mechanisms and found that even down near to the sensitivity limit, despite the H-compression used for the online material, photometry with an accuracy better than 0.1 mag rms is possible on DSS-II. Our investigation shows that the accuracy depends strongly on the source extraction method. The SuperCOSMOS scans, although retrieved with a higher spatial resolution, do not give us better results. The methods and parameters presented here allow the user to obtain good plate photometry in small fields down to the Schmidt plate survey limits with a few bright CCD calibrators, which may be calibrated with amateur-size telescopes. Especially for the events mentioned above, new field photometry for calibration purposes mostly exists, but the progenitors were not measured photometrically before. Also, the follow-up whether stellar concentrations are newly detected clusters or similar work may be done without using mid-size telescopes. The calibration presented here is a 'local' one for small fields. We show that the method presented here gives higher accuracies than 'global' calibrations of surveys (e.g. Guide Star Catalogue-II (GSC-II), SuperCOSMOS and the US Naval Observatory Astrometry Catalog B).  相似文献   

13.
We describe the current high level interfaces used for communicating with the Robonet‐1.0 Homogeneous Telescope Network. This is a network of three telescopes, the Liverpool Telescope and the Faulkes Telescopes (North and South). We describe our use of RTML and web‐services to enable control of the network by intelligent agents. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

14.
We present the first deep, optical, wide‐field imaging survey of the young open cluster Collinder 359, complemented by near‐infrared follow‐up observations. This study is part of a large programme aimed at examining the dependence of the mass function on environment and time. We have surveyed 1.6 square degree in the cluster in the I and z filters with the CFH12K camera on the Canada‐France‐Hawaii 3.6m telescope down to completeness and detection limits in both filters of 22.0m and 24.0m, respectively. Based on their location in the optical (I‐z ,I ) colour‐magnitude diagram, we have extracted new cluster member candidates in Collinder 359 spanning 1.3‐0.04 M⊙, assuming an age of 100 Myr and a distance of 450 pc for the cluster.We have used the 2MASS database as well as our own near‐infrared photometry to confirm the membership of the optically‐selected cluster candidates. Additionally, we have obtained optical spectroscopy and employed chromospheric activity as a further criterion to assess the membership of candidates. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

15.
The NST (New Solar Telescope), a 1.6 m clear aperture, off‐axis telescope, is in its commissioning phase at Big Bear Solar Observatory (BBSO). It will be the most capable, largest aperture solar telescope in the US until the 4 m ATST (Advanced Technology Solar Telescope) comes on‐line late in the next decade. The NST will be outfitted with state‐of‐the‐art scientific instruments at the Nasmyth focus on the telescope floor and in the Coudé Lab beneath the telescope. At the Nasmyth focus, several filtergraphs already in routine operation have offered high spatial resolution photometry in TiO 706 nm, Hα 656 nm, G‐band 430 nm and the near infrared (NIR), with the aid of a correlation tracker and image reconstruction system. Also, a Cryogenic Infrared Spectrograph (CYRA) is being developed to supply high signal‐to‐noise‐ratio spectrometry and polarimetry spanning 1.0 to 5.0 μm. The Coudé Lab instrumentation will include Adaptive Optics (AO), InfraRed Imaging Magnetograph (IRIM), Visible Imaging Magnetograph (VIM), and Fast Imaging Solar Spectrograph (FISS). A 308 sub‐aperture (349‐actuator deformable mirror) AO system will enable nearly diffraction limited observations over the NST's principal operating wavelengths from 0.4 μm through 1.7 μm. IRIM and VIM are Fabry‐Pérot based narrow‐band tunable filters, which provide high resolution two‐dimensional spectroscopic and polarimetric imaging in the NIR and visible respectively. FISS is a collaboration between BBSO and Seoul National University focussing on chromosphere dynamics. This paper reports the up‐to‐date progress on these instruments including an overview of each instrument and details of the current state of design, integration, calibration and setup/testing on the NST (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

16.
We present an RI photometric survey covering an area of 430 arcmin2 around the multiple star σ Orionis. The observations were conducted with the 0.8 m IAC‐80 Telescope at the Teide Observatory. The survey limiting R and I magnitudes are 22.5 and 21, and completeness magnitudes 21 and 20, respectively. We have selected 53 candidates from the I vs. R–I colour‐magnitude diagram (I = 14–20) that follow the previously known photometric sequence of the cluster. Adopting an age of 2–4 Myr for the cluster, we find that these objects span a mass range from 0.35 M⊙ to 0.015 M⊙. We have performed J‐band photometry of 52 candidates and Ks photometry for 12 of them, with the result that 50 follow the expected infrared sequence for the cluster, thus confirming with great confidence that the majority of the candidates are bona fide members. JHKs photometry from the Two Micron All Sky Survey (2MASS) is available for 50 of the candidates and are in good agreement with our data. Out of 48 candidates, which have photometric accuracies better than 0.1 mag in all bands, only three appear to show near‐infrared excesses. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

17.
In January 2009, first light observations with the NST (New Solar Telescope) in Big Bear Solar Observatory (BBSO) were made. NST has a 1.7 m primary with a 1.6 m clear aperture. First observational results in TiO and Hα are shown and discussed. The NST primary mirror is the most aspheric telescope mirror deployed to date. The NST is early in its commissioning, and the plans for this phase will be sketched. Lessons learned in building and implementing the NST are germane for the ATST and EST telescopes and will be discussed. The NST has an off‐axis Gregorian configuration consisting of a parabolic primary, heat‐stop, elliptical secondary and diagonal flats. The focal ratio of the primary mirror is f/2.4. The working wavelength range covers from 0.4 to 1.7 µm in the Coudé Lab beneath the telescope and all wavelengths including the far infrared at the Nasmyth focus on the dome floor (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

18.
DDO 68 (UGC 5340) is the second most metal-poor star-forming galaxy (12 + log(O/H) = 7.14). Its peculiar optical morphology and its HI distribution and kinematics are indicative of a merger origin. We use the u, g, r, and i photometry based on the SDSS images of DDO 68 to estimate its stellar population ages. The Hα images of DDO 68 were used to select several representative regions without nebular emission. The derived colors were analyzed by comparison with the PEGASE2 evolutionary tracks for various star formation (SF) scenarios, including the two extreme cases: (i) an instantaneous starburst and (ii) continuous SF with a constant rate. The (u − g) and (g − r) colors for all of the selected regions are consistent with the scenario of several “instantaneous” SF episodes with ages between ∼0.05 and ∼1 Gyr. The total mass of the visible stars in DDO 68 was estimated by comparing the colors and fluxes of the observed stellar subsystems with PEGASE2 models to be ∼2.4 × 107 M ⊙. This accounts for ∼6% of the total baryonic mass of the galaxy. All of the available data are consistent with the fact that DDO 68 is a very rare candidate for young galaxies. The bulk of its stars were formed during the recent (with the first encounter ∼1 Gyr ago) merger of two very gas-rich disks. DDO 68 is closest in its properties to cosmologically young low-mass galaxies. This article was submitted by the authors in English.  相似文献   

19.
The spectral energy distributions for pure-hydrogen (DA) hot white dwarfs can be accurately predicted by model atmospheres. This makes it possible to define spectrophotometric calibrators by scaling the theoretical spectral shapes with broad-band photometric observations – a strategy successfully exploited for the spectrographs onboard the Hubble Space Telescope ( HST ) using three primary DA standards. Absolute fluxes for non-DA secondary standards, introduced to increase the density of calibrators in the sky, need to be referred to the primary standards, but a far better solution would be to employ a network of DA stars scattered throughout the sky. We search for blue objects in the sixth data release of the Sloan Digital Sky Survey (SDSS) and fit DA model fluxes to identify suitable candidates. Reddening needs to be considered in the analysis of many of these stars. We propose a list of nine pure-hydrogen white dwarfs with absolute fluxes with estimated uncertainties below 3 per cent, including four objects with estimated errors <2 per cent, as candidates for spectrophotometric standards in the range  14 < g < 18  , and provide model-based fluxes scaled to match the SDSS broad-band fluxes for each. We apply the same method to the three HST DA standards, linking the zero point of their absolute fluxes to ugr magnitudes transformed from photometry obtained with the US Naval Observatory 1-m telescope. For these stars, we estimate uncertainties of <1 per cent in the optical, finding good consistency with the fluxes adopted for HST calibration.  相似文献   

20.
We present relative astrometry and differential photometry measurements for a sample of nearby southern orbital binaries making use of the technique of Adaptive Optics. The observations were made in December 2000, with the ADONIS camera mounted at the 3.6‐m ESO telescope from La Silla Observatory, equipped with the broad‐band near‐infrared filters (J ‐, H ‐, K ‐passbands). Our sample contains stars which do not fit very well the empirical mean mass‐luminosity relation (according to our previous study), but for which accurate parallaxes (determined by the Hipparcos satellite) and high‐quality orbits were available thanks to many previous efforts. We derived accurate positions and J, H, K magnitudes of the individual components of those binaries. The individual stellar components have near‐infrared colour indices well grouped in those plots and are comparable to standard single stars. The data reduction procedure used for deriving those results is described in detail. It is based on a least‐squares fit of Moffat‐Lorentz profiles in direct imaging for well‐resolved systems and on Fourier analysis for very close pairs. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

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