Садржај
Слике
Уплоадјуј своје слике
DSS Images Other Images
Везани чланци
Infrared 3-4 μm Spectroscopic Investigations of a Large Sample of Nearby Ultraluminous Infrared Galaxies
We present infrared L-band (3-4 μm) nuclear spectra of a large sampleof nearby ultraluminous infrared galaxies (ULIRGs). ULIRGs classifiedoptically as non-Seyfert galaxies (LINERs, H II regions, andunclassified) are our main targets. Using the 3.3 μm polycyclicaromatic hydrocarbon (PAH) emission and absorption features at 3.1 μmdue to ice-covered dust and at 3.4 μm produced by bare carbonaceousdust, we search for signatures of powerful AGNs deeply buried alongvirtually all lines of sight. The 3.3 μm PAH emission, the signaturesof starbursts, is detected in all but two non-Seyfert ULIRGs, but theestimated starburst magnitudes can account for only a small fraction ofthe infrared luminosities. Three LINER ULIRGs show spectra typical ofalmost pure buried AGNs, namely, strong absorption features with verysmall equivalent width PAH emission. Besides these three sources, 14LINER and three H II ULIRGs' nuclei show strong absorption featureswhose absolute optical depths suggest an energy source more centrallyconcentrated than the surrounding dust, such as a buried AGN. In total,17 out of 27 (63%) LINER and 3 out of 13 (23%) H II ULIRGs' nuclei showsome degree of evidence for powerful buried AGNs, suggesting thatpowerful buried AGNs may be more common in LINER ULIRGs than in H IIULIRGs. The evidence of AGNs is found in non-Seyfert ULIRGs with bothwarm and cool far-infrared colors. These spectra are compared with thoseof 15 ULIRGs' nuclei with optical Seyfert signatures taken forcomparison. The overall spectral properties suggest that the totalamount of dust around buried AGNs in non-Seyfert ULIRGs issystematically larger than that around AGNs in Seyfert 2 ULIRGs. Weargue that the optical (non)detectability of Seyfert signatures inULIRGs is highly dependent on how deeply buried the AGNs are, and thatit is essential to properly evaluate the energetic importance of buriedAGNs in non-Seyfert ULIRGs.
| HS 1216+5032: a physical quasar pair with one radio-loud broad absorption line quasar
We report on new multiwavelength observations of HS 1216+5032, a pairof quasi-stellar objects (QSOs) at z= 1.45 separated by 9.1 arcsec,which has been a perennial candidate for a massive dark lens. We explorehigh signal-to-noise ratio optical spectra from the MMT of bothcomponents, which show that aside from the effects of absorption, theemission-line profiles are quite similar. Near-infrared spectra from theUnited Kingdom Infrared Telescope show identical velocities in Hαemission, but a significant difference in the strength of the narrowcomponent, which is difficult to explain in a lens scenario. Wehighlight that, based on data from the Very Large Array Faint Images ofthe Radio Sky survey, HS 1216+5032B is a radio-loud broad absorptionline QSO, which certifies HS 1216+5032 as a physical quasar pair.Intriguingly, both quasars show spectroscopic evidence for highaccretion rates and large Eddington ratios L/LEdd, supportingthe hypothesis that close galaxy interactions trigger nuclear activity.
| Lithium abundances of the local thin disc stars
Lithium abundances are presented for a sample of 181 nearby F and Gdwarfs with accurate Hipparcos parallaxes. The stars are on circularorbits about the Galactic centre and, hence, are identified as belongingto the thin disc. This sample is combined with two published surveys toprovide a catalogue of lithium abundances, metallicities ([Fe/H]),masses, and ages for 451 F-G dwarfs, almost all belonging to the thindisc. The lithium abundances are compared and contrasted with publishedlithium abundances for F and G stars in local open clusters. The fieldstars span a larger range in [Fe/H] than the clusters for which [Fe/H]~=0.0 +/- 0.2. The initial (i.e. interstellar) lithium abundance of thesolar neighbourhood, as derived from stars for which astration oflithium is believed to be unimportant, is traced from logɛ(Li) =2.2 at [Fe/H]=-1 to logɛ(Li) = 3.2 at +0.1. This form for theevolution is dependent on the assumption that astration of lithium isnegligible for the stars defining the relation. An argument is advancedthat this latter assumption may not be entirely correct, and, theevolution of lithium with [Fe/H] may be flatter than previouslysupposed. A sharp Hyades-like Li dip is not seen among the field starsand appears to be replaced by a large spread among lithium abundances ofstars more massive than the lower mass limit of the dip. Astration oflithium by stars of masses too low to participate in the Li dip isdiscussed. These stars show little to no spread in lithium abundance ata given [Fe/H] and mass.
| The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of 14 000 F and G dwarfs
We present and discuss new determinations of metallicity, rotation, age,kinematics, and Galactic orbits for a complete, magnitude-limited, andkinematically unbiased sample of 16 682 nearby F and G dwarf stars. Our63 000 new, accurate radial-velocity observations for nearly 13 500stars allow identification of most of the binary stars in the sampleand, together with published uvbyβ photometry, Hipparcosparallaxes, Tycho-2 proper motions, and a few earlier radial velocities,complete the kinematic information for 14 139 stars. These high-qualityvelocity data are supplemented by effective temperatures andmetallicities newly derived from recent and/or revised calibrations. Theremaining stars either lack Hipparcos data or have fast rotation. Amajor effort has been devoted to the determination of new isochrone agesfor all stars for which this is possible. Particular attention has beengiven to a realistic treatment of statistical biases and errorestimates, as standard techniques tend to underestimate these effectsand introduce spurious features in the age distributions. Our ages agreewell with those by Edvardsson et al. (\cite{edv93}), despite severalastrophysical and computational improvements since then. We demonstrate,however, how strong observational and theoretical biases cause thedistribution of the observed ages to be very different from that of thetrue age distribution of the sample. Among the many basic relations ofthe Galactic disk that can be reinvestigated from the data presentedhere, we revisit the metallicity distribution of the G dwarfs and theage-metallicity, age-velocity, and metallicity-velocity relations of theSolar neighbourhood. Our first results confirm the lack of metal-poor Gdwarfs relative to closed-box model predictions (the ``G dwarfproblem''), the existence of radial metallicity gradients in the disk,the small change in mean metallicity of the thin disk since itsformation and the substantial scatter in metallicity at all ages, andthe continuing kinematic heating of the thin disk with an efficiencyconsistent with that expected for a combination of spiral arms and giantmolecular clouds. Distinct features in the distribution of the Vcomponent of the space motion are extended in age and metallicity,corresponding to the effects of stochastic spiral waves rather thanclassical moving groups, and may complicate the identification ofthick-disk stars from kinematic criteria. More advanced analyses of thisrich material will require careful simulations of the selection criteriafor the sample and the distribution of observational errors.Based on observations made with the Danish 1.5-m telescope at ESO, LaSilla, Chile, and with the Swiss 1-m telescope at Observatoire deHaute-Provence, France.Complete Tables 1 and 2 are only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/989
| ERO R1 in the Field of CL 0939+4713: Evidence for an S0-like Galaxy at z ~ 1.5
We present further observations of the extremely red object EROJ094258+4659.2, identified earlier by Iye et al. as ERO R1 in their deepimages of the cluster A851. We estimate its redshift independently byeight-band photometric redshift determination and cross-correlation of anew H-band spectrum with the optical spectra of local E/S0 galaxies andconclude that it lies at z~1.5. Although its colors are consistent withboth an elliptical galaxy and an S0 galaxy at that redshift, itselongated shape and exponential luminosity profile suggest the presenceof an evolved stellar disk component. We rule out the possibility thatthese properties are strongly influenced by gravitational lensing by theforeground cluster and therefore conclude that this object is morelikely to be an S0-like galaxy rather than a lensed elliptical. TheH-band spectrum does not show strong Hα emission, and the starformation rate therefore appears to be very modest. The presence of sucha galaxy with an apparently relaxed disk of stars at this high redshiftprovides a new and strong constraint on theoretical models that aim toexplain the formation and evolution of galaxies.On the basis of data collected at Subaru Telescope, which is operated bythe National Astronomical Observatory of Japan and, in part, onobservations with the NASA/ESA Hubble Space Telescope, obtained from thedata archive at the Space Telescope Science Institute, which is operatedby AURA, Inc., under NASA contract NAS5-26555.
| Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
We complete construction of a catalog containing improved astrometry andnew optical/infrared photometry for the vast majority of NLTT starslying in the overlap of regions covered by POSS I and by the secondincremental Two Micron All Sky Survey (2MASS) release, approximately 44%of the sky. The epoch 2000 positions are typically accurate to 130 mas,the proper motions to 5.5 mas yr-1, and the V-J colors to0.25 mag. Relative proper motions of binary components are measured to 3mas yr-1. The false-identification rate is ~1% for11<~V<~18 and substantially less at brighter magnitudes. Theseimprovements permit the construction of a reduced proper-motion diagramthat, for the first time, allows one to classify NLTT stars intomain-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We inturn use this diagram to analyze the properties of both our catalog andthe NLTT catalog on which it is based. In sharp contrast to popularbelief, we find that NLTT incompleteness in the plane is almostcompletely concentrated in MS stars, and that SDs and WDs are detectedalmost uniformly over the sky δ>-33deg. Our catalogwill therefore provide a powerful tool to probe these populationsstatistically, as well as to reliably identify individual SDs and WDs.
| Statistical cataloging of archival data for luminosity class IV-V stars. II. The epoch 2001 [Fe/H] catalog
This paper describes the derivation of an updated statistical catalog ofmetallicities. The stars for which those metallicities apply are ofspectral types F, G, and K, and are on or near the main sequence. Theinput data for the catalog are values of [Fe/H] published before 2002February and derived from lines of weak and moderate strength. Theanalyses used to derive the data have been based on one-dimensional LTEmodel atmospheres. Initial adjustments which are applied to the datainclude corrections to a uniform temperature scale which is given in acompanion paper (see Taylor \cite{t02}). After correction, the data aresubjected to a statistical analysis. For each of 941 stars considered,the results of that analysis include a mean value of [Fe/H], an rmserror, an associated number of degrees of freedom, and one or moreidentification numbers for source papers. The catalog of these resultssupersedes an earlier version given by Taylor (\cite{t94b}).Catalog is only available in electronic form at the CDS via anonymousftp cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/398/731
| Statistical cataloging of archival data for luminosity class IV-V stars. I. The epoch 2001 temperature catalog
This paper is one of a pair in which temperatures and metallicitycatalogs for class IV-V stars are considered. The temperature catalogdescribed here is derived from a calibration based on stellar angulardiameters. If published calibrations of this kind are compared by usingcolor-index transformations, temperature-dependent differences among thecalibrations are commonly found. However, such differences are minimizedif attention is restricted to calibrations based on Johnson V-K. Acalibration of this sort from Di Benedetto (\cite{dib98}) is thereforetested and adopted. That calibration is then applied to spectroscopicand photometric data, with the latter predominating. Cousins R-Iphotometry receives special attention because of its high precision andlow metallicity sensitivity. Testing of temperatures derived from thecalibration suggests that their accuracy and precision are satisfactory,though further testing will be warranted as new results appear. Thesetemperatures appear in the catalog as values of theta equiv5040/T(effective). Most of these entries are accompanied by measured orderived values of Cousins R-I. Entries are given for 951 stars.Catalog is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/398/721
| Optical and infrared spectroscopy of the type IIn SN 1998S: days 3-127
We present contemporary optical and infrared spectroscopic observationsof the type IIn SN 1998S covering the period between 3 and 127 daysafter discovery. During the first week the spectra are characterized byprominent broad H, He and Ciii/Niii emission lines with narrow peaks,superimposed on a very blue continuum (T~24000K). In the following twoweeks the Ciii/Niii emission vanished, together with the broad emissioncomponents of the H and He lines. Broad, blueshifted absorptioncomponents appeared in the spectra. The temperature of the continuumalso dropped to ~14000K. By the end of the first month the spectrumcomprised broad, blueshifted absorptions in H, He, Siii, Feii and Scii.By day 44, broad emission components in H and He reappeared in thespectra. These persisted to as late as days ~100-130, becomingincreasingly asymmetric. We agree with Leonard et al. that the broademission lines indicate interaction between the ejecta and circumstellarmaterial (CSM) emitted by the progenitor. We also agree that theprogenitor of SN 1998S appears to have gone through at least two phasesof mass-loss, giving rise to two CSM zones. Examination of the spectraindicates that the inner zone extended to <=90au, while the outer CSMextended from 185au to over 1800au. We also present high-resolutionspectra obtained at days 17 and 36. These spectra exhibit narrow P CygniHi and Hei lines superimposed on shallower, broader absorptioncomponents. Narrow lines of [Nii], [Oiii], [Neiii] and [Feiii] are alsoseen. We attribute the narrow lines to recombination and heatingfollowing ionization of the outer CSM shell by the UV/X-ray flash atshock breakout. Using these lines, we show that the outer CSM had avelocity of 40-50kms-1. Assuming a constant velocity, we caninfer that the outer CSM wind commenced more than 170 years ago, andceased about 20 years ago, while the inner CSM wind may have commencedless than 9 years ago. During the era of the outer CSM wind the outflowfrom the progenitor was high - at least~2×10-5Msolaryr-1. Thiscorresponds to a mass-loss of at least ~0.003Msolar,suggesting a massive progenitor. The shallower, broader absorption is ofwidth ~350kms-1, and may have arisen from a component of theouter CSM shell produced when the progenitor was going through a laterblue supergiant phase. Alternatively, it may have been produced by theacceleration of the outer CSM by the radiation pressure of the UVprecursor. We also describe and model first-overtone emission in carbonmonoxide observed in SN 1998S. We deduce a CO mass of~10-3Msolar moving at ~2200kms-1, andinfer a mixed metal/He core of about 4Msolar, againindicating a massive progenitor. Only three core-collapse supernovaehave been observed in the K band at post-100 days, and all three haveexhibited emission from CO.
| Energy Diagnoses of Nine Infrared Luminous Galaxies Based on 3-4 Micron Spectra
The energy sources of nine infrared luminous galaxies (IRLGs) arediagnosed based on their ground-based 3-4 μm spectra. Both theequivalent width of the 3.3 μm polycyclic aromatic hydrocarbon (PAH)emission feature and the 3.3 μm PAH to far-infrared luminosity ratio(L3.3/LFIR) are analyzed. Assuming that nuclearcompact starburst activity in these sources produces the 3.3 μm PAHemission as strongly as that in starburst galaxies with lowerfar-infrared luminosities, the following results are found. For sixIRLGs, both the observed equivalent widths and theL3.3/LFIR ratios are too small to explain the bulkof their far-infrared luminosities by compact starburst activity,indicating that active galactic nucleus (AGN) activity is a dominantenergy source. For the other three IRLGs, while the 3.3 μm PAHequivalent widths are within the range of starburst galaxies, theL3.3/LFIR ratios after correction for screen dustextinction are a factor of ~3 smaller. The uncertainty in the dustextinction correction factor and in the scatter of the intrinsicL3.3/LFIR ratios for starburst galaxies does notallow a determination of the ultimate energy sources for these threeIRLGs.
| A catalogue of [Fe/H] determinations: 1996 edition
A fifth Edition of the Catalogue of [Fe/H] determinations is presentedherewith. It contains 5946 determinations for 3247 stars, including 751stars in 84 associations, clusters or galaxies. The literature iscomplete up to December 1995. The 700 bibliographical referencescorrespond to [Fe/H] determinations obtained from high resolutionspectroscopic observations and detailed analyses, most of them carriedout with the help of model-atmospheres. The Catalogue is made up ofthree formatted files: File 1: field stars, File 2: stars in galacticassociations and clusters, and stars in SMC, LMC, M33, File 3: numberedlist of bibliographical references The three files are only available inelectronic form at the Centre de Donnees Stellaires in Strasbourg, viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5), or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| Optical Polarization of 1000 Stars Within 50-PARSECS from the Sun
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..101..551L&db_key=AST
| Lithium depletion and rotation in main-sequence stars
Lithium abundances were measured in nearly 200 old disk-population Fstars to examine the effects of rotational braking on the depletion ofLi. The sample was selected to be slightly evolved off the main sequenceso that the stars have completed all the Li depletion they will undergoon the main sequence. A large scatter in Li abundances in the late Fstars is found, indicating that the Li depletion is not related to ageand spectral type alone. Conventional depletion mechanisms likeconvective overshoot and microscopic diffusion are unable to explain Lidepletion in F stars with thin convective envelopes and are doubly taxedto explain such a scatter. No correlation is found between Li abundanceand the present projected rotational velocity and some of the most rapidrotators are undepleted, ruling out meridional circulation as the causeof Li depletion. There is a somewhat larger spread in Li abundances inthe spun-down late F stars compared to the early F stars which shouldremain rotationally unaltered on the main sequence.
| Third preliminary catalogue of stars observed with the photoelectric astrolabe of the Beijing Astronomical Observatory.
Not Available
| Photoelectric Photometry Observations in V and B of Some 15 Nearby Stars: I
Results of photoelectric observations in V and B light on the Johnsonstandard system are presented for 15 nearby stars ranging in spectraltype from late F to early K along with determinations of their V and Bmagnitudes and B-V color indexes.
| Some Cross-Reference Lists for the Catalog of Possible Nearby Stars
Not Available
| MK spectral types for some F and G stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1979PASP...91...83C&db_key=AST
| Possible nearby stars brighter than tenth magnitude
Basic data are compiled for 447 stars brighter than 10th visualmagnitude which may be within 25 pc of the sun and are missing from boththe Gliese (1969) and the Woolley et al. (1970) catalogs of nearbystars. The list includes 245 stars with photometric parallaxes, 17 starswith trigonometric parallaxes, and nine stars with dynamical parallaxes,all of which parallaxes are at least 0.040 arcsec, as well as 176 likelycandidates. The stars are grouped into six categories according to thereliability of absolute-magnitude estimates and ranked within each groupon the basis of calculated distance. The distance estimates incorporatea kinematic correction to the photometric parallaxes which is based onthe size of a star's proper motion. A list of stars brighter than 10thmag which appear in the Gliese but not in the Woolley et al. catalog isalso provided to facilitate cross-reference with existing catalogs ofnearby stars.
| Absolute luminosity calibration of F stars
Luminosity calibrations are performed for a restricted sample of 706F-type field stars of all luminosity classes and a similarly restrictedsample of 251 main-sequence F stars. The samples are restricted withrespect to values of photometric and metallicity indices, propermotions, radial velocities, and apparent magnitudes. Both linear andsecond-order relations between absolute magnitude and the photometricindices beta, /c1/ or (b-y), /c1/ are considered.These relations are calibrated by the statistical parallax method basedon the principle of maximum likelihood. The possible effect ofinterstellar absorption on the calibration results is investigated alongwith an effect of a photometric correction to the absolute magnitudes.The results obtained are compared with those of Crawford (1975) as wellas with the trigonometric parallaxes. The coefficients of thecalibration relations are derived from the trigonometric parallaxes, andpoor agreement is indicated. It is concluded that the trigonometricparallaxes must be used very carefully and only for nearby stars.
| Spectral classification of the bright F stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976PASP...88...95C&db_key=AST
| Luminosity and velocity distribution of high-luminosity red stars. III. Old-disk-population giants
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973PASP...85..542E&db_key=AST
| Photoelectric UBV observations made on the Palomar 20-inch telescope
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973MNRAS.164..133P&db_key=AST
| Stellar Convection Zones, Chromospheres, and Rotation
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966ApJ...144..695W&db_key=AST
| Dependence of Chromospheric Activity upon Age in Main-Sequence Stars: Additional Evidence.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1964ApJ...140.1401W&db_key=AST
|
Додај нови чланак
Линкови у сродству са темом
Додај нови линк
Чланови следећих група \:
|
Посматрања и Астрометриски подаци
| Сазвежђа: | Ловачки пси |
| Ректацензија: | 12h30m02.90s |
| Deклинација: | +51°32'08.0" |
| Apparent магнитуда: | 6.21 |
| Даљина: | 45.147 parsecs |
| Proper motion RA: | -292.6 |
| Proper motion Dec: | 24.9 |
| B-T magnitude: | 6.832 |
| V-T magnitude: | 6.27 |
Каталог и designations:
|
INHABITED SKY
