232 research outputs found
Dumb-bell galaxies in southern clusters: Catalog and preliminary statistical results
The dominant galaxy of a rich cluster is often an object whose formation and evolution is closely connected to the dynamics of the cluster itself. Hoessel (1980) and Schneider et al. (1983) estimate that 50 percent of the dominant galaxies are either of the dumb-bell type or have companions at projected distances less than 20 kpc, which is far in excess of the number expected from chance projection (see also Rood and Leir 1979). Presently there is no complete sample of these objects, with the exception of the listing of dumb-bell galaxies in BM type I and I-II clusters in the Abell statistical sample of Rood and Leir (1979). Recent dynamical studies of dumb-bell galaxies in clusters (Valentijn and Casertano, 1988) still suffer from inhomogeneity of the sample. The fact that it is a mixture of optically and radio selected objects may have introduced an unknown biases, for instance if the probability of radio emission is enhanced by the presence of close companions (Stocke, 1978, Heckman et al. 1985, Vettolani and Gregorini 1988) a bias could be present in their velocity distribution. However, this situation is bound to improve: a new sample of Abell clusters in the Southern Hemisphere has been constructed (Abell et al., 1988 hereafter ACO), which has several advantages over the original northern catalog. The plate material (IIIaJ plates) is of better quality and reaches fainter magnitudes. This makes it possible to classify the cluster types with a higher degree of accuracy, as well as to fainter magnitudes. The authors therefore decided to reconsider the whole problem constructing a new sample of dumb-bell galaxies homogeneously selected from the ACO survey. Details of the classification criteria are given
An Atlas of H-alpha and R Images and Radial Profiles of 29 Bright Isolated Spiral Galaxies
Narrow-band H-alpha+[NII] and broadband R images and surface photometry are
presented for a sample of 29 bright (M_B < -18) isolated S0-Scd galaxies within
a distance of 48 Mpc. These galaxies are among the most isolated nearby spiral
galaxies of their Hubble classifications as determined from the Nearby Galaxies
Catalog (Tully 1987a).Comment: To appear in Astrophysical Journal Supplement Series. 17 pages,
including 8 atlas pages in JPEG format. Version with high resolution figures
available at http://www1.union.edu/~koopmanr/preprints.htm
Observations of the nucleus of M100
The galaxy M100 = NGC 4321 is a spiral galaxy in which a bright Type II Supernova was discovered on April 19, 1979. Its spectral evolution was followed with IUE for more than two months (refs. 1,2). At all epochs, the spectrum was dominated by continuous radiation on which emission and absorption features were superimposed. The equivalent width of most of the absorption features appeared not to vary with time suggesting that they originated in the interstellar media of M100 and our own galaxy
The ATESP 5 GHz radio survey. II. Physical properties of the faint radio population
One of the most debated issues about sub-mJy radio sources, which are
responsible for the steepening of the 1.4 GHz source counts, is the origin of
their radio emission. Particularly interesting is the possibility of combining
radio spectral index information with other observational properties to assess
whether the sources are triggered by star formation or nuclear activity. The
aim of this work is to study the optical and near infrared properties of a
complete sample of 131 radio sources with S>0.4 mJy, observed at both 1.4 and 5
GHz as part of the ATESP radio survey. We use deep multi-colour (UBVRIJK)
images, mostly taken in the framework of the ESO Deep Public Survey, to
optically identify and derive photometric redshifts for the ATESP radio
sources. Deep optical coverage and extensive colour information are available
for 3/4 of the region covered by the radio sample. Typical depths of the images
are U~25, B~26, V~25.4, R~25.5, I~24.3, 19.5<K_s<20.2, J<22.2. Optical/near
infrared counterparts are found for ~78% (66/85) of the radio sources in the
region covered by the deep multi-colour imaging, and for 56 of these reliable
estimates of the redshift and type are derived. We find that many of the
sources with flat radio spectra are characterised by high radio-to-optical
ratios (R>1000), typical of classical powerful radio galaxies and quasars.
Flat-spectrum sources with low R values are preferentially identified with
early type galaxies, where the radio emission is most probably triggered by
low-luminosity active galactic nuclei. Considering both early type galaxies and
quasars as sources with an active nucleus, such sources largely dominate our
sample (78%). Flat-spectrum sources associated with early type galaxies are
quite compact (d<10-30 kpc), suggesting core-dominated radio emission.Comment: 15 pages, 13 figures, accepted for pubblication in A&
The ATESP Radio Survey II. The Source Catalogue
This paper is part of a series reporting the results of the Australia
Telescope ESO Slice Project (ATESP) radio survey obtained at 1400 MHz with the
Australia Telescope Compact Array (ATCA) over the region covered by the ESO
Slice Project (ESP) galaxy redshift survey. The survey consists of 16 radio
mosaics with ~8"x14" resolution and uniform sensitivity (1sigma noise level ~79
microJy) over the whole area of the ESP redshift survey (~26 sq. degrees at
decl. -40 degr). Here we present the catalogue derived from the ATESP survey.
We detected 2960 distinct radio sources down to a flux density limit of ~0.5
mJy (6sigma), 1402 being sub-mJy sources. We describe in detail the procedure
followed for the source extraction and parameterization. The internal accuracy
of the source parameters was tested with Monte Carlo simulations and possible
systematic effects (e.g. bandwidth smearing) have been quantified.Comment: 14 pages, 14 Postscript figures, Accepted for publication in A&A
Suppl. Corrected typos and added Journal Referenc
The Angular Power Spectrum of EDSGC Galaxies
We determine the angular power spectrum, C_l, of the Edinburgh/Durham
Southern Galaxy Catalog (EDSGC) and use this statistic to constrain
cosmological parameters. Our methods for determining C_l, and the parameters
that affect it are based on those developed for the analysis of cosmic
microwave background maps. We expect them to be useful for future surveys.
Assuming flat cold dark matter models with a cosmological constant (constrained
by COBE/DMR and local cluster abundances), and a scale--independent bias, b, we
find good fits to the EDSGC angular power spectrum with 1.11 < b < 2.35 and 0.2
< Omega_m < 0.55 at 95% confidence. These results are not significantly
affected by the ``integral constraint'' or extinction by interstellar dust, but
may be by our assumption of Gaussianity.Comment: 11 pages, 9 figures, version to appear in Ap
Redshifts for 2410 Galaxies in the Century Survey Region
The `Century Survey' strip covers 102 square degrees within the limits 8.5h
\leq \alpha_{1950} \leq 16.5h, 29.0 degrees \leq \delta_{1950} \leq 30.0
degrees. The strip passes through the Corona Borealis supercluster and the
outer region of the Coma cluster.
Within the Century Survey region, we have measured 2410 redshifts which
constitute four overlapping complete redshift surveys: (1) 1728 galaxies with
Kron-Cousins R_{phot} \leq 16.13 covering the entire strip, (2) 507 galaxies
with R_{phot} \leq 16.4 in the right ascension range 8h 32m \leq \alpha_{1950}
\leq 10h 45m, (3) 1251 galaxies with absorption- and K-corrected R_{CCD, corr}
\leq 16.2 covering the right ascension range 8.5h \leq \alpha_{1950} \leq 13.5h
and (4) 1255 galaxies with absorption- and K-corrected V_{CCD, corr} \leq 16.7
also covering the right ascension range 8.5h \leq \alpha_{1950} \leq 13.5h. All
of these redshift samples are more than 98 % complete to the specified
magnitude limit.Comment: 18 pages, 9 figures, 3 tables, 2 abbreviated tables. In press, to
appear in Astronomical Journal, Dec. 2001 issu
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