目录
图像
上传图像
DSS Images Other Images
相关文章
The QDOT all-sky IRAS galaxy redshift survey
We describe the construction of the QDOT survey, which is publiclyavailable from an anonymous FTP account. The catalogue consists ofinfrared properties and redshifts of an all-sky sample of 2387 IRASgalaxies brighter than the IRAS PSC 60-μm completeness limit(S_60>0.6Jy), sparsely sampled at a rate of one-in-six. At |b|>10deg, after removing a small number of Galactic sources, the redshiftcompleteness is better than 98per cent (2086/2127). New redshifts for1401 IRAS sources were obtained to complete the catalogue; themeasurement and reduction of these are described, and the new redshiftstabulated here. We also tabulate all sources at |b|>10 deg with noredshift so far, and sources with conflicting alternative redshiftseither from our own work, or from published velocities. A list of 95ultraluminous galaxies (i.e. with L_60μm>10^12 L_solar) is alsoprovided. Of these, ~20per cent are AGN of some kind; the broad-lineobjects typically show strong Feii emission. Since the publication ofthe first QDOT papers, there have been several hundred velocity changes:some velocities are new, some QDOT velocities have been replaced by moreaccurate values, and some errors have been corrected. We also present anew analysis of the accuracy and linearity of IRAS 60-μm fluxes. Wefind that the flux uncertainties are well described by a combination of0.05-Jy fixed size uncertainty and 8per cent fractional uncertainty.This is not enough to cause the large Malmquist-type errors in the rateof evolution postulated by Fisher et al. We do, however, find marginalevidence for non-linearity in the PSC 60-μm flux scale, in the sensethat faint sources may have fluxes overestimated by about 5per centcompared with bright sources. We update some of the previous scientificanalyses to assess the changes. The main new results are as follows. (1)The luminosity function is very well determined overall but is uncertainby a factor of several at the very highest luminosities(L_60μm>5x10^12L_solar), as this is where the remainingunidentified objects are almost certainly concentrated. (2) Thebest-fitting rate of evolution is somewhat lower than our previousestimate; expressed as pure density evolution with density varying as(1+z)^p, we find p=5.6+/-2.3. Making a rough correction for the possible(but very uncertain) non-linearity of fluxes, we find p=4.5+/-2.3. (3)The dipole amplitude decreases a little, and the implied value of thedensity parameter, assuming that IRAS galaxies trace the mass, isΩ=0.9(+0.45, -0.25). (4) Finally, the estimate of density varianceon large scales changes negligibly, still indicating a significantdiscrepancy from the predictions of simple cold dark matter cosmogonies.
| Imaging and spectroscopy of ten southern galaxies selected from a catalogue of peculiar galaxies
We present BVRI broad band photometry and long slit spectroscopy for asample of ten southern galaxies selected from the Aguero Catalogue ofPeculiar Galaxies. The analysis of the images shows that only fourgalaxies of the sample are truly peculiar galaxies and four are normalspirals. The remaining two galaxies, a normal spiral and a SO, form aninteracting pair. Despite the rather complicated structure of thepeculiar galaxies we did not find evidence of mergers in our analysis ofimages and rotation curves. Almost all galaxies in our sample show starforming regions with very blue colors, (B-V) ranging from 0.2 to 0.6.The SO galaxy shows a very interesting structure in the V-I color mapsuggesting that star formation events have occurred in concentric annulicentered in the nucleus. In our photometric analysis we did not findcharacteristics that could distinguish between normal and peculiargalaxies. We obtained the ``pure-emission'' line spectra for sixgalaxies of the sample by subtracting appropriate templates. Thesetemplates correspond to ellipticals selected from our library ofspectra. This subtraction technique provides a powerful tool tocalculate line flux ratios uncontaminated by the underlying stellarpopulation. Our spectroscopic analysis confirms that the spiral galaxyof the interacting system AM 2054-433 has a LINER-type nucleus. In thenormal galaxy ESO 316-29 we find evidence of a LINER nucleus and wereport a new Seyfert 2 galaxy, AM 2054-433 N. For this SO galaxy theline flux ratios measured from the pure-emission spectrum are indicativeof a Seyfert 2 rather than a LINER nucleus as it was previously reportedby other authors. Three of the four peculiar galaxies in our sample havemuch higher star-formation rate than normal galaxies, as measured byHα + [NII] line emission. The observed EW(Hα + [NII]) valuesfor these peculiar galaxies are around 60 Angstroms, compared to 22Angstroms for normal galaxies. Whole-aperture spectra for these peculiargalaxies show very similar EW(Hα + [NII]) values to those observedin their nuclear region suggesting that a global starburst has occurred.Although our sample is small the results presented suggest that peculiarmorphology and global starburst events are closely related.
| A wide angle redshift survey of the Hydra-Centaurus region
Spectroscopic observations of 266 galaxies in the Hya-Cen region arereported. Redshift data obtained at 350-700 nm with dispersion 21 nm/mmusing the UNIT spectrograph and RPCS detector on the 1.9-m RadcliffeReflector telescope at SAO during March 1985, May 1986, and March 1987are presented in tables and graphs and briefly characterized. It isshown that the Hya supercluster is separated from the Cen superclusterby a large void at right ascension 11 h 40 min, declination -35 deg, andradial velocity 5200 km/sec; a bridge of galaxies at velocity about 3200km/sec connects the two superclusters.
| Southern Galaxy Catalogue.
Not Available
| The Antlia cluster of galaxies and its environment - The Hydra I-Centaurus supercluster
The small Antlia cluster of galaxies was investigated by measuring manyradial velocities for galaxies from the Lauberts catalog in the Antliaregion. Apart from the Antlia cluster itself, four more small groupswere identified. These five systems form a tiny but not bound Antliamini-supercluster. The mini-supercluster consists of small groups andclusters and of a dispersed component of field galaxies. The five galaxysystems are also part of the large Hydra I-Centaurus supercluster. Thislarge supercluster belongs now to the class of well observed ones. Ithas a chain-like filamentary structure. This supercluster seems to beconnected to the Local Supercluster via two very extended but very loosegroups. The total structure is the triangle-shaped Virgo-HydraI-Centaurus supercluster.
|
提交文章
相关链接
提交链接
下列团体成员
|
观测天体数据
目录:
|
