Ýçindekiler
Görüntüler
Resim Yükleyin
DSS Images Other Images
Ýlgili Makaleler
The supermassive black hole of FornaxA
The radio galaxy FornaxA (NGC 1316) is a prominent merger remnant in theoutskirts of the Fornax cluster. Its giant radio lobes suggest thepresence of a powerful active galactic nuclei (AGN) and thus a centralsupermassive black hole (SMBH). FornaxA now seems to be in a transitionstate between active black hole growth and quiescence, as indicated bythe strongly declined activity of the nucleus. Studying objects in thisevolutionary phase is particularly important in order to understand thelink between bulge formation and black hole growth, which is manifestedin the M•-? relation between black hole mass andbulge velocity dispersion. So far, a measurement of the SMBH mass hasnot been possible in FornaxA, as it is enshrouded in dust which makesoptical measurements impossible. We present high-resolution adaptiveoptics assisted integral-field data of FornaxA, taken with SINFONI atthe Very Large Telescope in the K band, where the influence of dust isnegligible. The achieved spatial resolution is 0.085 arcsec, which isabout a fifth of the diameter of the expected sphere of influence of theblack hole. The stellar kinematics was measured using the region aroundthe CO bandheads at 2.3 ?m. FornaxA does not rotate inside the inner~3 arcsec. The velocity dispersion increases towards the centre. Theweak AGN emission affects the stellar kinematics in the inner ~0.06arcsec only. Beyond this radius, the stellar kinematics appears relaxedin the central regions. We use axisymmetric orbit models to determinethe mass of the SMBH in the centre of FornaxA. The three-dimensionalnature of our data provides the possibility to directly test theconsistency of the data with axisymmetry by modelling each of the fourquadrants separately. According to our dynamical models, consistent SMBHmasses M• and dynamical Ks-band mass-to-lightratios ? are obtained for all quadrants, with = 1.3 × 108Msolar[rms(M•) = 0.4 × 108Msolar]and = 0.68 [rms(?) = 0.03], confirming theassumption of axisymmetry. For the folded and averaged data, we findM• = 1.5+0.75-0.8 ×108Msolar and ? =0.65+0.075-0.05 (3? errors). Thus, the blackhole mass of FornaxA is consistent within the error with the Tremaine etal. M•-? relation, but is a factor of ~4 smallerthan expected from its bulge mass and the Marconi & Hunt relation.Based on observations at the European Southern Observatory (ESO) VeryLarge Telescope [076.B-0457(A)] and archival ESO La Silla [66.C-0310(A)]and NASA/ESA Hubble Space Telescope data (GO Proposal 7458), obtainedfrom the ESO/ST-ECF Science Archive Facility.E-mail: nnowak@mpe.mpg.de
| Central K-band kinematics and line strength maps of NGC 1399
In this paper we present for the first time high spatial resolutionK-band maps of the central kinematical and near-infrared spectralproperties of the giant cD galaxy in the Fornax cluster, NGC 1399. Weconfirm the presence of a central velocity dispersion dip within r ≤0.2 arcsec seen in previous long-slit studies. Our velocity dispersionmaps give evidence of a non-symmetric structure in this central area byshowing three σ peaks to the north-east, south-east and west ofthe galaxy centre. Additionally we measure near-IR line strength indicesat unprecedented spatial resolution in NGC 1399. The most importantfeatures we observe in our 2-dimensional line strength maps are drops inNa I and CO (2-0) line strength in the nuclear region of the galaxy,coinciding spatially with the drop in σ. The observed linestrength and velocity dispersion changes suggest a scenario where thecentre of NGC 1399 harbours a dynamically cold subsystem with a distinctstellar population.Based on observation collected at the ESO Paranal La Silla Observatory,Chile, during the Science Verification of SINFONI.
| Hipparcos red stars in the HpV_T2 and V I_C systems
For Hipparcos M, S, and C spectral type stars, we provide calibratedinstantaneous (epoch) Cousins V - I color indices using newly derivedHpV_T2 photometry. Three new sets of ground-based Cousins V I data havebeen obtained for more than 170 carbon and red M giants. These datasetsin combination with the published sources of V I photometry served toobtain the calibration curves linking Hipparcos/Tycho Hp-V_T2 with theCousins V - I index. In total, 321 carbon stars and 4464 M- and S-typestars have new V - I indices. The standard error of the mean V - I isabout 0.1 mag or better down to Hp~9 although it deteriorates rapidly atfainter magnitudes. These V - I indices can be used to verify thepublished Hipparcos V - I color indices. Thus, we have identified ahandful of new cases where, instead of the real target, a random fieldstar has been observed. A considerable fraction of the DMSA/C and DMSA/Vsolutions for red stars appear not to be warranted. Most likely suchspurious solutions may originate from usage of a heavily biased color inthe astrometric processing.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA 1997).}\fnmsep\thanks{Table 7 is onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/397/997
| New periodic variables from the Hipparcos epoch photometry
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
| Stars with the Largest Hipparcos Photometric Amplitudes
A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
| Hipparcos: The Stars
Not Available
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| Classification and Identification of IRAS Sources with Low-Resolution Spectra
IRAS low-resolution spectra were extracted for 11,224 IRAS sources.These spectra were classified into astrophysical classes, based on thepresence of emission and absorption features and on the shape of thecontinuum. Counterparts of these IRAS sources in existing optical andinfrared catalogs are identified, and their optical spectral types arelisted if they are known. The correlations between thephotospheric/optical and circumstellar/infrared classification arediscussed.
| IRAS catalogues and atlases - Atlas of low-resolution spectra
Plots of all 5425 spectra in the IRAS catalogue of low-resolutionspectra are presented. The catalogue contains the average spectra ofmost IRAS poiont sources with 12 micron flux densities above 10 Jy.
|
Yeni bir Makale Öner
Ýlgili Baðlantýlar
Yeni Bir Baðlantý Öner
sonraki gruplarýn üyesi:
|
Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Kurt |
| Sað Açýklýk: | 15h51m41.18s |
| Yükselim: | -38°09'29.3" |
| Görünürdeki Parlaklýk: | 9.107 |
| özdevim Sað Açýklýk: | -1.8 |
| özdevim Yükselim: | -1 |
| B-T magnitude: | 10.95 |
| V-T magnitude: | 9.26 |
Kataloglar ve belirtme:
|
