1,720,974 research outputs found
The Tully-Fisher relation of spiral galaxies
No full textThe Tully-Fisher (TF) relation is an empirically establish correlation between the luminosity of a spiral galaxy and its rotational velocity (Tully-Fisher, 1977). We used the Tully-Fisher relation to probe the dark matter (DM) distribution in the optical regions of spiral galaxies. We investigated a sample of rotation curves that includes 957 galaxies. We applied a new technique that takes advantage of the full knowledge of the galaxy rotation curves
The radial Tully-Fisher relation for spiral galaxies - I
Get PDFWe find a new Tully-Fisher-like relation for spiral galaxies holding at different galactocentric radii. This radial Tully-Fisher relation allows us to investigate the distribution of matter in the optical regions of spiral galaxies. This relation, applied to three different samples of rotation curves of spiral galaxies, directly proves that: (i) the rotation velocity of spirals is a good measure of their gravitational potential and both the rotation curve's amplitudes and profiles are well predicted by galaxy luminosity, (ii) the existence of a dark component, less concentrated than the luminous one, and (iii) a scaling law, according to which, inside the disc optical size: M-dark/M-lum = 0.5(L-B/10(11) L-B circle dot)(-0.7)
Probing dark matter haloes of spiral galaxies at poorly explored distances using satellite kinematics
No full textAims: We present the results of a pilot project designed to study the distribution of dark matter haloes out to very large radii in spiral galaxies. As dynamical probe, we use their rotation curves and the motions of satellite galaxies. In this pilot stage, we observed seven late-type spiral galaxies of about the same luminosity MR ~ -22 (and approximately the same mass). We investigate the kinematics of these galaxies, and the radial and angular distribution of their satellites.
Methods: Using VIMOS at the VLT, we carried out a spectroscopic survey in seven 14' × 14' fields each around a late-type isolated spiral galaxy. We obtained radial velocities and spatial distributions for 77 candidate satellites. After removing the interlopers, we are left with 61 true satellites. In combination with the rotation curves of the primary galaxies, satellites are used to probe the gravitational potential of the primaries and derive the dark matter halo properties by means of standard mass modeling techniques.
Results: We find (a) that the dark matter haloes of luminous spirals (MR ~ -22) have virial radii of ~400 kpc and virial masses of 3.5 × 1012 Msun; (b) that the radial velocity and angular distributions of the satellites around the primaries are isotropic; and (c) that the resulting mass distribution is in good agreement with that found in the optical regions of spirals and described by the universal rotation curve of spirals once extrapolated to large radii. The results obtained in this pilot phase of the project are already interesting and limited only by small number statistics. The full project involving an order of magnitude more targets, would very likely provide us with a definitive picture of the dark matter distribution around spirals out to their virial radii and beyond
The disc mass of spiral galaxies
Get PDFWe derive the disk masses of 18 spiral galaxies of different luminosity and Hubble Type, both by mass modelling their rotation curves and by fitting their SED with spectro-photometric models. The good agreement of the estimates obtained from these two different methods allows us to quantify the reliability of their performance and to derive very accurate stellar mass-to-light ratio vs color (and stellar mass) relationships
The universal rotation curve of spiral galaxies - II. The dark matter distribution out to the virial radius
Get PDFIn the current ΛCDM cosmological scenario, N-body simulations provide us with a universal mass profile, and consequently a universal equilibrium circular velocity of the virialized objects, as galaxies. In this paper we obtain, by combining kinematical data of their inner regions with global observational properties, the universal rotation curve of disc galaxies and the corresponding mass distribution out to their virial radius. This curve extends the results of Paper I, concerning the inner luminous regions of Sb-Im spirals, out to the edge of the galaxy haloes
Y, Ba, and La abundance in the stars of open clusters and Galactic field
Get PDFThe lanthanum abundances were determined by the synthetic spectrum method using the VLT spectra of 30 stars of eight open clusters, namely Ruprecht 4, Ruprecht 7, Berkeley 25, Berkeley 73, Berkeley 75 and NGC 6192, NGC 6404, NGC 6583. The analyses of the behaviour of the yttrium, barium, and lanthanum abundances with ages in the stars of the open clusters and galactic field were carried out. We found that the scatter of the barium abundances is larger than those of the yttrium and lanthanum. The resulting scatter can be caused by both real causes and methods of abundance determinations (using the equivalent widths of the lines, LTE approach, etc.). The traced trends of Y, Ba, La abundances with the age can indicate the growth of contribution in the n-capture enrichments from low-mass AGB stars. Comparison of the barium and lanthanum abundances with ages for a thin disc stars (\citealt{mis13a}) and those obtained by us for the open cluster stars, shows that the lanthanum as well as barium demonstrates large values for several clusters, but its value is only reaches 0.3 dex. The barium overabundance in the cluster Ruprecht 7 may be indicative of other ways (not AGB stars) barium enrichment
Yttrium and barium in open clusters
No full textBased on the VLT high-resolution spectra for stars of five open clusters: Ruprecht 4, Ruprecht 7, Berkeley 25, Berkeley 73, and Berkeley 75 (G. Carraro et al., 2007) we determined the yttrium and barium abundances using the synthetic-spectrum method. Barium abundance was calculated under a non-LTE approximation. We analyzed the correlation between yttrium and barium abundances and the ages of open clusters and stars of the Galactic thin disk
Barium and yttrium abundance in intermediate-age and old open clusters
Get PDFBarium is a neutron-capture element that, in open clusters, is frequently overabundant with respect to iron. A clear explanation for this is still missing. Additionally, its gradient across the Galactic disc is poorly constrained. We measure the abundance of yttrium and barium using the synthetic spectrum method from UVES high-resolution spectra of eight distant open clusters, namely Ruprecht 4, Ruprecht 7, Berkeley 25, Berkeley 73, Berkeley 75, NGC 6192, NGC 6404 and NGC 6583. The barium abundance was estimated using non-local thermodynamic equilibrium approximation. We confirm that barium is indeed overabundant in most clusters, especially young clusters. Finally, we investigated the trend of yttrium and barium abundances as a function of distance in the Galaxy and ages. Several scenarios for the barium overabundance are then discussed
On the subject of the Ba overabundance in the open clusters stars
Get PDFFor eight distant open clusters, namely Ruprecht 4, Ruprecht 7, Berkeley 25, Berkeley 73, Berkeley 75, NGC 6192, NGC 6404, and NGC 6583, we determined the yttrium and barium abundances using the UVES, VLT spectra (ESO, Chile). The stars of one young cluster (Ruprecht 7) demonstrate significant barium overabundance(∼0.55 dex) that can not be due to the determination error. We have considered the Ba abundance determination errors due to LTE approach, saturation of the lines, synthetic and observed barium line fitting, and the causes of the Ba overabundance associated with the Galactic disc enrichment or the origin of open clusters. Possible explanation for this overabundance can be the origin of n-capture elements enrichment of the clusters (galactic or extragalactic) or additional sources of the Ba production
Rotation curves of luminous spiral galaxies
No full textWe have investigated the stellar light distribution and the rotation curves of high-luminosity spiral galaxies in the local Universe. The sample contains 30 high-quality extended H\alpha and H I rotation curves. The stellar disk scale-length of these objects was measured or taken from the literature. We find that in the outermost parts of the stellar disks of these massive objects, the rotation curves agree with the Universal Rotation Curve (Salucci et al. 2007), however a few rotation curves of the sample show a divergence
- …
