Оглавление
Изображения
Загрузить ваше изображение
DSS Images Other Images
Публикации по объекту
The Kinematics of Thick Disks in Nine External Galaxies
We present kinematic measurements of thin- and thick-disk components ina sample of nine edge-on galaxies. We extract stellar and ionized gasrotation curves at and above the galaxies' midplanes using the Ca IItriplet absorption features and Hα emission lines measured withthe GMOS spectrographs on Gemini-North and Gemini-South. For the highermass galaxies in the sample, we fail to detect differences between thethin- and thick-disk kinematics. In the lower mass galaxies, there is awide range of thick-disk behavior, including thick disks withsubstantial lag and one counterrotating thick disk. We compare ourrotation curves with expectations from thick-disk formation models andconclude that the wide variety of thick-disk kinematics favors aformation scenario in which thick-disk stars are accreted or formedduring merger events as opposed to models that form thick disks throughgradual thin-disk heating.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| The Kinematics of Thick Disks in External Galaxies
We present kinematic measurements of the thick and thin disks in twoedge-on galaxies. We have derived stellar rotation curves at and abovethe galaxies' midplanes using Ca II triplet features measured with theGMOS spectrograph on Gemini North. In one galaxy, FGC 1415, thekinematics above the plane shows clear rotation that lags that of themidplane by ~20%-50%, similar to the behavior seen in the Milky Way.However, the kinematics of the second galaxy, FGC 227, is quitedifferent. The rotation above the plane is extremely slow, showing<~25% of the rotation speed of the stars at the midplane. Wedecompose the observed rotation curves into a superposition of thick-and thin-disk kinematics, using two-dimensional fits to the galaxyimages to determine the fraction of thick-disk stars at each position.We find that the thick disk of FGC 1415 rotates at 30%-40% of therotation speed of the thin disk. In contrast, the thick disk of FGC 227is very likely counterrotating if it is rotating at all. Theseobservations are consistent with the velocity dispersion profiles thatwe measure for each galaxy. The detection of counterrotating thick disksconclusively rules out models in which the thick disk forms eitherduring monolithic collapse or from vertical heating of an earlier thindisk. Instead, the data strongly support models in which the thick diskforms from direct accretion of stars from infalling satellites.
| Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters
The availability of the Hipparcos Catalogue has triggered many kinematicand dynamical studies of the solar neighbourhood. Nevertheless, thosestudies generally lacked the third component of the space velocities,i.e., the radial velocities. This work presents the kinematic analysisof 5952 K and 739 M giants in the solar neighbourhood which includes forthe first time radial velocity data from a large survey performed withthe CORAVEL spectrovelocimeter. It also uses proper motions from theTycho-2 catalogue, which are expected to be more accurate than theHipparcos ones. An important by-product of this study is the observedfraction of only 5.7% of spectroscopic binaries among M giants ascompared to 13.7% for K giants. After excluding the binaries for whichno center-of-mass velocity could be estimated, 5311 K and 719 M giantsremain in the final sample. The UV-plane constructed from these datafor the stars with precise parallaxes (σπ/π≤20%) reveals a rich small-scale structure, with several clumpscorresponding to the Hercules stream, the Sirius moving group, and theHyades and Pleiades superclusters. A maximum-likelihood method, based ona Bayesian approach, has been applied to the data, in order to make fulluse of all the available stars (not only those with precise parallaxes)and to derive the kinematic properties of these subgroups. Isochrones inthe Hertzsprung-Russell diagram reveal a very wide range of ages forstars belonging to these groups. These groups are most probably relatedto the dynamical perturbation by transient spiral waves (as recentlymodelled by De Simone et al. \cite{Simone2004}) rather than to clusterremnants. A possible explanation for the presence of younggroup/clusters in the same area of the UV-plane is that they have beenput there by the spiral wave associated with their formation, while thekinematics of the older stars of our sample has also been disturbed bythe same wave. The emerging picture is thus one of dynamical streamspervading the solar neighbourhood and travelling in the Galaxy withsimilar space velocities. The term dynamical stream is more appropriatethan the traditional term supercluster since it involves stars ofdifferent ages, not born at the same place nor at the same time. Theposition of those streams in the UV-plane is responsible for the vertexdeviation of 16.2o ± 5.6o for the wholesample. Our study suggests that the vertex deviation for youngerpopulations could have the same dynamical origin. The underlyingvelocity ellipsoid, extracted by the maximum-likelihood method afterremoval of the streams, is not centered on the value commonly acceptedfor the radial antisolar motion: it is centered on < U > =-2.78±1.07 km s-1. However, the full data set(including the various streams) does yield the usual value for theradial solar motion, when properly accounting for the biases inherent tothis kind of analysis (namely, < U > = -10.25±0.15 kms-1). This discrepancy clearly raises the essential questionof how to derive the solar motion in the presence of dynamicalperturbations altering the kinematics of the solar neighbourhood: doesthere exist in the solar neighbourhood a subset of stars having no netradial motion which can be used as a reference against which to measurethe solar motion?Based on observations performed at the Swiss 1m-telescope at OHP,France, and on data from the ESA Hipparcos astrometry satellite.Full Table \ref{taba1} is 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/430/165}
| A Large-Scale Jet and FR I Radio Source in a Spiral Galaxy: The Host Properties and External Environment
We have identified a large (~200 h-175 kpc),powerful double radio source whose host galaxy is clearly a disk andmost likely a spiral. This FR I-like radio galaxy is located very nearthe center of the richness class 0 cluster A428. The existence of suchan object violates a fundamental paradigm for radio-loud active galacticnuclei (AGNs). In our first paper, we showed that this object was mostconsistent with a spiral host classification with optical emission-lineratios and colors suggestive of an active nucleus. However, we were notable to confirm actual radio jet emission based on the maps available atthat time. In this paper, we present new, higher resolution radioimaging, a radio/millimeter continuum spectrum for the nucleus, adetection of H I absorption against the bright radio core, an upperlimit to CO emission and the gas mass, and 70 (68 new) optical redshiftsmeasured in the direction of A428. We confirm the existence of a radiojet at 20 cm, extending 42 h-175 into the southernlobe. At 3.6 cm, we also detect a nuclear jet similar in length to thatin M87, although 10 times weaker. We believe that this is the firstdetection of a radio jet on these scales in a disk/spiral host galaxy.The nuclear radio spectrum is similar to many blazar- or quasar-likeobjects, suggesting that the galaxy harbors an imbedded and obscuredAGN. We model a turnover in the spectrum at low frequencies as a resultof free-free absorption. We detect very strong and narrow H Iabsorption, with nearly the entire 20 cm continuum flux of the corebeing absorbed, implying an unusually large optical depth (τ~1). Themost consistent model is that we are viewing the nucleus through adisklike distribution of gas in the interstellar medium, possiblythrough a spiral arm or a warp to account for the above-average columndensity. From the radial velocity distribution, we find that A428 is infact made up of at least two clumps of galaxies separated by ~3300 kms-1, which themselves appear to be imbedded in a nearlycontinuous distribution of galaxies over 13,000 km s-1 invelocity space. Thus, the environment around this unusual radio sourceis more like that of a poor galaxy group imbedded in a filament-likestructure viewed end-on.
| The Evolution of Early-Type Galaxies in Distant Clusters. II. Internal Kinematics of 55 Galaxies in the z=0.33 Cluster CL 1358+62
We define a large sample of galaxies for use in a study of thefundamental plane in the intermediate redshift cluster Cl 1358+62 atz=0.33. We have analyzed high-resolution spectra for 55 members of thecluster. The data were acquired with the Low-Resolution ImagingSpectrograph on the Keck I 10 m telescope. A new algorithm for measuringvelocity dispersions is presented and used to measure the internalkinematics of the galaxies. This algorithm has been tested against theFourier fitting method so that the data presented here can be comparedwith those measured previously in nearby galaxies. We have measuredcentral velocity dispersions suitable for use in a fundamental planeanalysis. The data have a high signal-to-noise ratio (S/N) and theresulting random errors on the dispersions are very low, typically lessthat 5%. Uncertainties due to mismatch of the stellar templates havebeen minimized through several tests, and the total systematic error isof order ~5%. Good seeing enabled us to measure velocity dispersionprofiles and rotation curves for most of the sample, and although alarge fraction of the galaxies display a high level of rotation, thegradients of the total second moment of the kinematics are all veryregular and similar to those in nearby galaxies. We conclude that thedata therefore can be reliably corrected for aperture size in a mannerconsistent with nearby galaxy samples. Based on observations obtained atthe W. M. Keck Observatory, which is operated jointly by the CaliforniaInstitute of Technology and the University of California.
| The Vienna-KPNO search for Doppler-imaging candidate stars. I. A catalog of stellar-activity indicators for 1058 late-type Hipparcos stars
We present the results from a spectroscopic Ca ii H&K survey of 1058late-type stars selected from a color-limited subsample of the Hipparcoscatalog. Out of these 1058 stars, 371 stars were found to showsignificant H&K emission, most of them previously unknown; 23% withstrong emission, 36% with moderate emission, and 41% with weak emission.These spectra are used to determine absolute H&K emission-linefluxes, radial velocities, and equivalent widths of theluminosity-sensitive Sr ii line at 4077 Ä. Red-wavelengthspectroscopic and Strömgren y photometric follow-up observations ofthe 371 stars with H&K emission are used to additionally determinethe absolute Hα -core flux, the lithium abundance from the Li i6708 Å equivalent width, the rotational velocity vsin i, theradial velocity, and the light variations and its periodicity. Thelatter is interpreted as the stellar rotation period due to aninhomogeneous surface brightness distribution. 156 stars were found withphotometric periods between 0.29 and 64 days, 11 additional systemsshowed quasi-periodic variations possibly in excess of ~50 days. Further54 stars had variations but no unique period was found, and four starswere essentially constant. Altogether, 170 new variable stars werediscovered. Additionally, we found 17 new SB1 (plus 16 new candidates)and 19 new SB2 systems, as well as one definite and two possible new SB3systems. Finally, we present a list of 21 stars that we think are mostsuitable candidates for a detailed study with the Doppler-imagingtechnique. Tables A1--A3 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Fundamental plane distances to early-type field galaxies in the South Equatorial Strip. I. The spectroscopic data
Radial velocities and central velocity dispersions are derived for 238E/S0 galaxies from medium-resolution spectroscopy. New spectroscopicdata have been obtained as part of a study of the Fundamental Planedistances and peculiar motions of early-type galaxies in three selecteddirections of the South Equatorial Strip, undertaken in order toinvestigate the reality of large-scale streaming motion; results of thisstudy have been reported in Müller et al. (1998). The new APM SouthEquatorial Strip Catalog (-17fdg 5 < delta < +2fdg 5) was used toselect the sample of field galaxies in three directions: (1) 15h10 -16h10; (2) 20h30 - 21h50; (3) 00h10 - 01h30. The spectra obtained have amedian S/N per Å of 23, an instrumental resolution (FWHM) of ~ 4Å, and the spectrograph resolution (dispersion) is ~ 100 kms-1. The Fourier cross-correlation method was used to derivethe radial velocities and velocity dispersions. The velocity dispersionshave been corrected for the size of the aperture and for the galaxyeffective radius. Comparisons of the derived radial velocities with datafrom the literature show that our values are accurate to 40 kms-1. A comparison with results from Jo rgensen et al. (1995)shows that the derived central velocity dispersion have an rms scatterof 0.036 in log sigma . There is no offset relative to the velocitydispersions of Davies et al. (1987).
| The Stellar and Gaseous Kinematics in NGC 253
This paper presents observations made at intermediate spectral andspatial resolutions along the major and minor axes of the starburstgalaxy NGC 253. The spectral ranges analyzed are in the region of thestellar Mg I b (~5175 Angstroms) line, in the near-IR Ca II triplet(~8550 Angstroms) absorption features, and in the region of the H alphaemission line. We compare the shape of the stellar features with thoseof reference stars and determine the line-of-sight velocity distributionof the stellar component by using a two-dimensional Gaussiandecomposition algorithm, and we show for the first time the rotationcurve of the stellar component in NGC 253. Comparing the recessionvelocity curves of the gas and stars, we show that the stellar componenthas a decoupled kinematics with respect to the gas, displaying ashallower velocity gradient and larger velocity dispersion than the gasin the inner regions. The minor-axis kinematics, together with thekinematics across the central 40" along the major axis, suggest thepresence of a rotating body with a kinematically misaligned axis withrespect to the main disk of the galaxy. The asymmetries in the LOSvelocity distribution along the minor axis, together with the steepvelocity gradient of the gaseous component, suggest a merger scenario asthe source of these kinematic signatures. The enclosed mass in thecentral regions is computed to be (2.4 +/- 0.5) x 107 Mȯ for aradius of r = 0."7 (10 pc). A double gaseous component in the central 6"is detected from the [S III] lambda 9069 Angstroms data along the minoraxis; this seems to be the signature of a superbubble, due to asupernova rate of 0.05 yr-1.
| 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.
| Nine Seasons of Velocity Measurements in the Draco and Ursa Minor Dwarf Spheroidal Galaxies with the MMT Echelle
We have used the Multiple Mirror Telescope echelle spectrograph tomeasure 112 velocities of 42 stars in the Draco and Ursa Minor dwarfspheroidal galaxies and three velocities of three foreground starsbetween 1982 April and 1990 September. We used 11 A resolution spectraobtained with the MX multifiber spectrograph at the Steward 90" to findadditional giant candidates; 5 UMi and 13 Draco stars were then observedat the MMT and added to the original sample of velocity members. Inaddition, the MX spectra were used to eliminate 74 stars in thedirection of UMI and 59 stars in Draco as likely foreground dwarfs. Wedetected 7 velocity variables, defined as those stars whose probabilityof exceeding the measured X^2^ by chance is less than 1.5%. Three ofthese stars are Carbon (C) stars (UMi K and VA 335 and Draco C1); twohave emission lines (Draco CI and UMi M). We show that the C star DracoC4, with a proper motion membership probability of 7%, has a velocityconsistent with membership. It is not surprising that these C (mostlikely CH) stars are binaries because McClure has shown that mostGalactic CH stars are in binary systems. Of the remaining 35 stars, only4 are velocity variables, with measured velocity extrema of 29.1 kms^-1^ (UMi M), 7.2 km s^-1^ (Draco XI-2), 9.0 km s^-1^ (Draco 24), and8.3 km s^-1^ (Draco 473). The velocity dispersions are 10.1 +/- 1.7 kms^-1^ for UMi, and 9.9 +/- 1.4 km s^-1^ for Draco. These dispersionschange to 10.5 +/- 2.0 for UMi, and 8.2 +?- 1.3 for Draco if weeliminate the velocity variables. Our dispersion for UMi differs fromthat of Hargreaves et al. [MNRAS, 271,693 (1994b)] by 1.3σ of thecombined errors. These velocities are combined with the one-componentKing models of Pryor & Kormendy [AJ, 100,127 (1990)] to give M/L =73 for UMi, and 77 for Draco.
| CA II H and K measurements made at Mount Wilson Observatory, 1966-1983
Summaries are presented of the photoelectric measurements of stellar CaII H and K line intensity made at Mount Wilson Observatory during theyears 1966-1983. These results are derived from 65,263 individualobservations of 1296 stars. For each star, for each observing season,the maximum, minimum, mean, and variation of the instrumental H and Kindex 'S' are given, as well as a measurement of the accuracy ofobservation. A total of 3110 seasonal summaries are reported. Factorswhich affect the ability to detect stellar activity variations andaccurately measure their amplitudes, such as the accuracy of the H and Kmeasurements and scattered light contamination, are discussed. Relationsare given which facilitate intercomparison of 'S' values with residualintensities derived from ordinary spectrophotometry, and for convertingmeasurements to absolute fluxes.
| Spectroscopy of V471 Tau. I - Review of basic properties
Spectroscopic observations of the eclipsing binary V471 Tau are reportedand analyzed. Data obtained mainly in the red band at Mt. WilsonObservatory and KPNO during the period 1975-1983 are compiled inextensive tables and graphs, and the radial velocity of the K dwarfcomponent is determined using a Griffin-mask technique. Resultsdiscussed include: (1) distance 44 + or - 6 pc, (consistent withmembership in the Hyades), (2) apparent period variation consistent witha third component, (3) emissionlike features affecting theradial-velocity determination, (4) transient features consistent withthe presence of flares, and (5) phase-coherent variation in H-alpha(attributed to the action of the white-dwarf Lyman continuum emission onthe K dwarf).
| Cluster population incompleteness bias and the value of H(0) from the Tully-Fisher B0(T) relation
Data on the Virgo cluster and ten more distant clusters are the basis ofan evaluation of the influence of the cluster population incompletenessbias on the B-band Tully-Fisher relation. The data are well fitted by atheoretical curve that is obtained for a Hubble constant value of 72 +or - 5 km/sec per Mpc in the de Vaucouleurs local scale, confirming theconstant's previous determination in light of a study of the Malmquistbias for field galaxies. The true value for the Hubble constant isconcluded to lie within the 50-75 range, depending on the primarycalibration.
| Standard Velocity Stars
Not Available
| Photoelectric radial velocities, paper 6 Heard's IAU standard stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975MNRAS.171..407G&db_key=AST
| The establishment of 21 new ninth magnitude IAU standard radial velocity stars
Not Available
|
Добавить новую статью
Внешние ссылки
- - Внешних ссылок не найдено -
Добавить внешнюю ссылку
Группы:
|
Наблюдательные данные и астрометрия
| Созвездие: | Андромеда |
| Прямое восхождение: | 00h46m27.04s |
| Склонение: | +30°57'05.6" |
| Видимая звёздная величина: | 7.31 |
| Расстояние: | 180.505 парсек |
| Собственное движение RA: | -40.5 |
| Собственное движение Dec: | -28.3 |
| B-T magnitude: | 8.769 |
| V-T magnitude: | 7.431 |
Каталоги и обозначения:
|
