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Colours Line Strengths and Stellar Kinematics of NGC2663 and NGC5018
Results of the analysis of broad-band optical images and long-slitspectra of the two elliptical galaxies NGC 2663 and 5018 are presented.Line-strength profiles of Mg_2_, Fe_5270_ and Fe_5335_ have been derivedfor both galaxies, together with rotational velocity and velocitydispersion curves at three and four position angles (PAs) for NGC 2663and 5018, respectively. The measurements extend to about 1.8 effectiveradii for NGC 2663, and to about 3 effective radii for NGC 5018.Axisymmetric dynamical models with distribution function f= f(E, J_z_)(i.e. depending only on the energy E and the angular momentum along thesymmetry axis J_z_) have been fitted to the kinematic profiles of bothgalaxies, to derive information about the intrinsic shapes of theluminous galaxies and the sizes and shapes of possible dark haloes. Inagreement with what has been found for other ellipticals: (i) versus Mg_2_ shows, within both galaxies, a steeper slope than thatshown by galactic nuclei, and (ii) the slope is approximately equal inthe two galaxies and constant within each galaxy (over the whole radialrange, to ~2R_e_). A shift is observed between the two galaxies,implying different [Mg/Fe] abundance ratios. In NGC 2663, the derived[Mg/Fe] abundance ratio is (as is normally found in ellipticals) largerthan solar; its colour [d(B - R )/d log r = - 0.08] and Mg_2_ (dMg_2_/dlog r = - 0.06) gradients are consistent with each other and with achange in metallicity only. The galaxy shows a hint of counter-rotationwithin the innermost 20 arcsec and minor axis rotation. Any oblate orprolate model fitting its kinematics along any two position angles failsto fit the third position angle available, the discrepancy with the databeing a systematic shift. Most probably, this galaxy is a triaxialobject (observed V_rot_/σ~ 0.15 with e~0.3, anisotropy parameterδ >= 0.2-0.3); alternatively, it might be prolate but alwayswith an anisotropic velocity dispersion tensor. In NGC 5018, an almostflat velocity dispersion profile is observed out to the last measuredpoint. Assuming that the galaxy is an axisymmetric rotator, such a flata profile can be reproduced at a confidence level >~ 5 sigma only ifa very massive dark matter halo surrounds the luminous component (M_D_ ~6 M_lum_). A rather strong (B-R) colour gradient is observed in NGC 5018[d(B- R)/dlog r= -0.13], despite its shallow Mg_2_ gradient (dMg_2_/dlogr= - 0.04). Although the whole galaxy is blue, its central (B - R)colour and the observed patchy structure in the (B - R) colour mapsuggest a considerable amount of extinction in its central regions. Ifthe dust follows the Galactic extinction law, at 1550 A one could evenexpect ~2 mag of extinction. This might hide a younger stellarpopulation diluting the Mg_2_ line strength, and might explain the lackof UV flux reported by other authors. The dilution of Mg_2_ would alsoexplain the solar [Mg/Fe] abundance ratio.
| Evolved GK stars near the sun. I - The old disk population
A sample of nearly two thousand GK giants with intermediate band, (R,I),DDO and Geneva photometry has been assembled. Astrometric data is alsoavailable for most of the stars. The some 800 members of the old diskpopulation in the sample yield accurate luminosities (from two sources),reddening values and chemical abundances from calibrations of thephotometric parameters. Less than one percent of the objects arepeculiar in the sense that the flux distribution is abnormal. Thepeculiarity is signaled by strong CH (and Ba II) and weak CH. The CH+stars are all spectroscopic binaries, probably with white dwarfcompanions, whereas the CH- stars are not. A broad absorption band,centered near 3500 A, is found in the CH+ stars whereas the CH- objectshave a broad emission feature in the same region. The intensity of theseabsorptions and emissions are independent of the intensity of abnormalspectral features. Ten percent of the old disk sample have a heavyelement abundance from one and a half to three times the solar value.The distribution of the heavy element abundances is nearly a normal onewith a peak near solar abundance and ranges three times to one sixthsolar. The distribution of the (U, V) velocities is independent of theheavy element abundance and does not appear to be random. Ten percent ofthe old disk stars show a CN anomaly, equally divided between CN strongand CN weak. Several stars of individual astrometric or astrophysicalimportance are isolated.
| Large and kinematically unbiased samples of G- and K-type stars. IV - Evolved stars of the old disk population
Modified Stromgren and (R,I) photometry, along with DDO and Genevaphotometry, are presented for a complete sample of evolved old-disk Gand K giants in the Bright Star Catalogue. Stars with ages of between1.5 x 10 to the 9th and 10 to the 10th yr are found to have anear-normal distribution of heavy element abundances, centered on anFe/H abundance ratio of -0.1 dex. The old disk clusters NGC 3680 and IC4651 contain red-straggler young-disk giants that are probablycontemporaries of the blue stragglers in the clusters.
| Large and kinematically unbiased samples of G- and K-type stars. II - Observations of evolved stars in the Bright Star sample. III - Evolved young disk stars in the Bright Star sample
Four color and RI observations were obtained for a large sample ofG-type and K-type stars in the Bright Star Catalogue. Data are firstpresented for 110 evolved stars. Photometry of evolved young diskpopulation stars have then been calibrated for luminosity, reddening,and metallicity on the basis of results for members of the Hyades andSirius superclusters. New DDO results are given for 120 stars.
| Radial velocities of southern stars obtained with the photoelectric scanner CORAVEL. III - 790 late-type bright stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&AS...59...15A&db_key=AST
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | דג מעופף |
| התרוממות ימנית: | 07h06m14.10s |
| סירוב: | -68°50'14.0" |
| גודל גלוי: | 6.47 |
| מרחק: | 153.61 פארסק |
| תנועה נכונה: | 5.3 |
| תנועה נכונה: | -2.5 |
| B-T magnitude: | 7.797 |
| V-T magnitude: | 6.59 |
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INHABITED SKY
