Contenuti
Immagini
Carica la tua immagine
DSS Images Other Images
Articoli relazionati
Kinematics and metallicities of globular clusters in M104
We have obtained spectra for globular cluster candidates in M104 withthe Low Dispersion Survey Spectrograph (LDSS-2) on the William HerschelTelescope, confirming 34 objects as M104 globular clusters. We find acluster velocity dispersion of ~260kms^-1, and the projected massestimator gives a mass of 5.0 (3.5,6.7)x10^11Msolar for M104 within aprojected radius of ~330arcsec (14kpc for D=8.55Mpc). Our best estimatefor the mass-to-light ratio is M/L_V_T=16^+5.5_-5.0 within the sameradius. Considering all of the possible sources of uncertainty, we finda lower limit of M/L_V=5.3, which is larger than the M/L_V ratio foundfrom rotation curve analyses inside 180arcsec. We thus conclude that themass-to-light ratio increases with radius, or in other words that M104possesses a dark matter halo. There is a marginal detection of rotationin the M104 cluster system at the 92.5 per cent confidence level; largersamples will be needed to investigate this possibility. Interestingly,the M104 globular cluster and planetary nebulae (PNe) kinematics areroughly consistent inside ~100arcsec. Finally, we find a mean clustermetallicity of [Fe/H]=-0.70+/-0.3, which is more typical of clusters ingiant elliptical (gE)/cD galaxies than it is of clusters in otherspirals.
| A large, complete, volume-limited sample of G-type dwarfs. I. Completion of Stroemgren UVBY photometry
Four-colour photometry of potential dwarf stars of types G0 to K2,selected from the Michigan Spectral Catalogues (Vol. 1-3), has beencarried out. The results are presented in a catalogue containing 4247uvby observations of 3900 stars, all south of δ = -26deg. Theoverall internal rms errors of one observation (transformed to thestandard system) of a program star in the interval 8.5 < V < 10.5are 0.0044, 0.0021, 0.0039, and 0.0059, respectively, in V, b-y, m_1_ ,and c_1_. The purpose of the catalogue, combined with earliercatalogues, is to allow selection of a large, complete, volume-limitedsample of G- and K-type dwarfs, investigate their metallicitydistribution, and compare it to predictions of various models ofgalactic chemical evolution. Future papers in this series will discussthese subjects.
|
Sottometti un nuovo articolo
Link relazionati
Sottometti un nuovo link
Membro dei seguenti gruppi:
|
Osservazione e dati astrometrici
| Costellazione: | Fenice |
| Ascensione retta: | 00h06m27.52s |
| Declinazione: | -52°55'59.3" |
| Magnitudine apparente: | 9.008 |
| Moto proprio RA: | 9.9 |
| Moto proprio Dec: | -1.4 |
| B-T magnitude: | 10.826 |
| V-T magnitude: | 9.159 |
Cataloghi e designazioni:
|
INHABITED SKY
