Оглавление
Изображения
Загрузить ваше изображение
DSS Images Other Images
Публикации по объекту
X-shaped radio galaxies as observational evidence for the interaction of supermassive binary black holes and accretion disc at parsec scale
In the hierarchical galaxy formation model, today's galaxies are theproduct of frequent galaxy merging, triggering the activity of activegalactic nuclei and forming a supermassive black hole binary. A binarymay become stalling at the parsec scale and is expected to be detectedin nearby normal galaxies, which is inconsistent with observations. Inthis paper, we investigate the interaction of the supermassive binaryblack holes (SMBBHs) and an accretion disc and show that the stallingcan be avoided due to the interaction and a rapid coalescence of SMMBHscan be reached. A binary formed during galaxy merging within Hubble timeis most likely inclined with a random inclination angle and twists theaccretion disc, aligning the inner part of the disc with the orbitalplane on a time-scale ~103 yr. The twisted inner discsubsequently realigns the rotating central supermassive black hole on atime-scale <~105 yr due to the Bardeen-Petterson effect.It is shown that the detected X-shaped structure in some FR II radiogalaxies may be due to the interaction-realignment of the binary andaccretion disc occurring within the parsec scale of the galaxy centre.The configuration is very consistent with the observations of X-shapedradio sources. The X-shaped radio feature forms only in FR II radiosources due to the strong interaction between the binary and a standarddisc, while the absence of X-shaped FR I radio galaxies is due to thefact that the interaction between the binary and the radiativelyinefficient accretion flow in FR I radio sources is negligible. Thedetection rate, λX~ 7 per cent, of the X-shapedstructure in a sample of low-luminous FR II radio galaxies implies thatthe X-shaped feature forms in nearly all FR II radio sources of anaverage lifetime tlife~ 108 yr. This is consistentwith the estimates of the net lifetime of quasi-stellar objects andradio galaxies and with the picture that the activity of active galacticnuclei is triggered by galaxy merging. As the jet orients vertically tothe accretion disc, which is supposed to be aligned with the galacticplane of the host galaxy, the old wings in the X-shaped radio sourcesare expected to be aligned with the minor axis of the host galaxy whilethe orientation of the active jet distributes randomly. It is suggestedby the model that the binary would remain misaligned with the outer discfor most of the disc viscous time or the lifetime of the FR II radiogalaxies and the orientation of the jet in most FR II radio galaxiesdistributes randomly. As the binary-disc interaction in FR I radiogalaxies is negligible or a source evolves from FR II to FR I type afterthe binary becomes aligned with the outer disc, the jets in most FR Iradio galaxies are expected to be vertical to the accretion disc andthus the major axis of the host galaxy. We discuss the relationship ofX-shaped and double-double radio galaxies (DDRGs) and suggest that allX-shaped radio sources would evolve into DDRGs after the coalescence ofthe SMBBHs and that most radio sources evolve from FR II to FR I typeafter an interruption of jet formation, implying that the average sizeof FR I radio sources is smaller than that of FR II radio galaxies. Themodel is applied to two X-shaped radio sources 4C +01.30 and 3C 293 andone DDRG source J0116-473 with a bar-like feature. We show that theSMBBHs in the three objects are minor with mass ratio q~ 0.1-0.3.
| The ISOPHOT 170 μm Serendipity Survey II. The catalog of optically identified galaxies%
The ISOPHOT Serendipity Sky Survey strip-scanning measurements covering≈15% of the far-infrared (FIR) sky at 170 μm were searched forcompact sources associated with optically identified galaxies. CompactSerendipity Survey sources with a high signal-to-noise ratio in at leasttwo ISOPHOT C200 detector pixels were selected that have a positionalassociation with a galaxy identification in the NED and/or Simbaddatabases and a galaxy counterpart visible on the Digitized Sky Surveyplates. A catalog with 170 μm fluxes for more than 1900 galaxies hasbeen established, 200 of which were measured several times. The faintest170 μm fluxes reach values just below 0.5 Jy, while the brightest,already somewhat extended galaxies have fluxes up to ≈600 Jy. For thevast majority of listed galaxies, the 170 μm fluxes were measured forthe first time. While most of the galaxies are spirals, about 70 of thesources are classified as ellipticals or lenticulars. This is the onlycurrently available large-scale galaxy catalog containing a sufficientnumber of sources with 170 μm fluxes to allow further statisticalstudies of various FIR properties.Based on observations with ISO, an ESA project with instruments fundedby ESA Member States (especially the PI countries: France, Germany, TheNetherlands and the UK) and with the participation of ISAS and NASA.Members of the Consortium on the ISOPHOT Serendipity Survey (CISS) areMPIA Heidelberg, ESA ISO SOC Villafranca, AIP Potsdam, IPAC Pasadena,Imperial College London.Full Table 4 and Table 6 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/cgi-bin/qcat?J/A+A/422/39
| Physical Coupling of Kazarian Galaxies with Surrounding Galaxies
Results from a statistical study of Kazarian galaxies and the objectssurrounding them are presented. It is shown that: (1) the sample ofKazarian galaxies up to 16m.0 is complete. (2) Roughly 35.7% of theKazarian galaxies are members of clusters, 14.0% of groups, and 13.6% ofbinary systems, while 36.7% are single galaxies. (3) Of the 580 Kazariangalaxies, roughly 61.2% are infrared, 8.8% radio, and 2.8% x-raysources. (4) The relative numbers of Kazarian galaxies for completesamples of I, R, and X in the different groups are systematically higherthan the corresponding numbers for samples of all Kazarian galaxies.
| Morphological classification of new galaxies with a UV excess
The results of a morphological classification of 580 galaxies with a UVexcess, included in the lists in [M. A. Kazarian, Astrofizika,15, 5(1979); ibid.,15, 193 (1979); M. A. Kazarian and É. S. Kazarian,ibid.,16, 17 (1980); ibid.,18, 512 (1982); ibid.,19, 213 (1983)], arepresented. For this we have developed a set of symbols, using the typesE, S, and Ir introduced by Hubble, as well as symbols introduced byother authors and us. This set enabled us to make the morphologicalclassification. Direct photographs obtained on the 2.6-m and 6-mtelescopes were used to classify 141 of the galaxies (over 24%), whilePalomar Atlas charts were used for the remaining 439 galaxies. Thesegalaxies were divided into two groups based on classificationconditions, and data on each group are given in Tables 1 and 2,respectively. The results for each group, given in Table 3, show thatwith the transition from early types, such as C and E, to later types,such as S and Ir, the relative number of galaxies going into one group(Table 1), in which the classification was based on direct photographs,increases in comparison with the number going into the other group(Table 2).
|
Добавить новую статью
Внешние ссылки
- - Внешних ссылок не найдено -
Добавить внешнюю ссылку
Группы:
|
Наблюдательные данные и астрометрия
Каталоги и обозначения:
|
