Contenidos
Imágenes
Subir su imagen
DSS Images Other Images
Artículos relacionados
Black Hole Masses of Active Galaxies with Double-peaked Balmer Emission Lines
We have obtained near-IR spectra of five AGNs that exhibit double-peakedBalmer emission lines (NGC 1097, Pictor A, PKS 0921-213, 1E0450.30-1817, and IRAS 0236.6-3101). The stellar velocity dispersions ofthe host galaxies were measured from the Ca II λλ8494,8542, 8662 absorption lines and were found to range from 140 to 200 kms-1. Using the well-known correlation between the black holemass and the stellar velocity dispersion, the black hole masses in thesegalaxies were estimated to range from 4×107 to1.2×108 Msolar. We supplement theobservations presented here with estimates of the black holes masses forfive additional double-peaked emitters (Arp 102B, 3C 390.3, NGC 4579,NGC 4203, and M81) obtained by other authors using similar methods.Using these black hole masses, we infer the ratio of the bolometricluminosity to the Eddington luminosity,(Lbol/LEdd). We find that two objects (Pictor Aand PKS 0921-213) have Lbol/LEdd~0.2, whereas theother objects have Lbol/LEdd<~10-2(nearby, low-luminosity double-peaked emitters are the most extreme,with Lbol/LEdd<~10-4). The physicaltimescales in the outer regions of the accretion disks (atr~103GM/c2) in these objects were also estimatedand range from a few months for the dynamical timescale to severaldecades for the sound crossing timescale. The profile variability inthese objects is typically an order of magnitude longer than thedynamical time, but we note that variability occurring on the dynamicaltimescale has not been ruled out by the observations.Based on observations carried out at Cerro Tololo Inter-AmericanObservatory, which is operated by AURA, Inc., under a cooperativeagreement with the National Science Foundation.
| The Identification of IRAS Point Sources - Part One - a 304-DEGREE Field Centred on the South Galactic Pole
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986MNRAS.223..279W&db_key=AST
| A kinematic and abundance survey at the galactic poles
The DDO intermediate band system is used to obtain detailed informationabout abundance gradients and velocity dispersions in the galaxy, withan emphasis on the properties of halo stars in the range of from 1 to 5kpc. The DDO abundance index is calibrated agianst (Fe/H) for metal-poorstars, with a resulting gradient of about -0.2 per kpc. However, whenthe sample is divided into two subsamples with (Fe/H) less than -0.5 andequal to or greater than -0.5, the gradients are -0.14 and 0.00,respectively. DDO observations of about 1000 stars, mostly G5-K5 giants,show that the velocity dispersion increases both with decrease inmetallicity and increase in z distance. The abundances found for high-zstars are similar to the A-star results of Rodgers (1971) in that abouthalf the K giants above 1 kpc appear to have solar abundances.
| The K-giant population at the South Galactic Pole
CN anomalies and distances from the galactic plane have been derivedthrough DDO photometry for 171 late-type giant and subgiant stars nearthe South Galactic Pole. The previously found trend of the difference inCN concentration with distance (approximately equal to 0.09/kpc) holdsto approximately 2 kpc, but at greater distances from the plane theslope becomes approximately zero. The giants beyond 2 kpc are ofessentially normal composition or only slightly underabundant in heavierelements.
|
Enviar un nuevo artículo
Enlaces relacionados
- - No se han encontrado enlaces -
En viar un nuevo enlace
Miembro de los siguientes grupos:
|
Datos observacionales y astrométricos
| Constelación: | Escultor |
| Ascensión Recta: | 00h40m33.34s |
| Declinación: | -29°25'15.1" |
| Magnitud Aparente: | 6.748 |
| Distancia: | 205.339 parsecs |
| Movimiento Propio en Ascensión Recta: | 19.1 |
| Movimiento Propio en Declinación: | 9.1 |
| B-T magnitude: | 7.989 |
| V-T magnitude: | 6.851 |
Catálogos y designaciones:
|
