201 research outputs found
Near infrared observations of quasars with extended ionized envelopes
We have observed a sample of 15 and 8 quasars with redshifts between 0.11 and
0.87 (mean value 0.38) in the J and K' bands respectively. Eleven of the
quasars were previously known to be associated with extended emission line
regions. After deconvolution of the image, substraction of the PSF when
possible, and identification of companions with the help of HST archive images
when available, extensions are seen for at least eleven quasars. However,
average profiles are different from that of the PSF in only four objects, for
which a good fit is obtained with an law, suggesting that the
underlying galaxies are ellipticals. Redshifts were available in the literature
for surrounding objects in five quasar fields. For these objects, one to five
companion galaxies were found. One quasar even belongs to a richness class 1
cluster. Most other quasars in our sample have nearby galaxies in projection
which may also be companions. Environmental effects are therefore probably
important to account for the properties of these objects.Comment: Accepted for publication in A&A
Integral field spectroscopy of the radio galaxy 3C 171
We have performed integral field spectroscopy of the radio galaxy 3C 171
(redshift z=0.238) with the TIGER instrument at the Canada France Hawaii
telescope in the Hbeta-[OIII]4959-5007 wavelength region. We present the
reconstructed Hbeta and [OIII] images and compare them to the HST and radio
maps. We discuss the variations of the [OIII]/Hbeta line ratio throughout the
nebulosity. We also analyze the velocity field in detail, in particular the
presence of several components. We find that the kinematics derived with
emission lines in the central region (inside 1 arcsec) are compatible with a
disk-like rotation of low amplitude (50 km/s). The continuum surface brightness
profile follows an r^{1/4} law, suggesting that the underlying galaxy is an
elliptical with an effective radius of 15 kpc.
We have fit two components in the region centered 2.7 arcsec to the West and
of extension 3 arcsec^2. We find that the blueshifted component is an extension
of the central part, whereas the second one is redshifted by 600 km/s. In both
components, line ratios and FWHM are compatible with the presence of shocks
induced by jet-cloud interactions.Comment: 8 pages, 15 figures. Accepted for publication in A&A Main Journal
(July, 3rd
A catalogue of velocities in the cluster of galaxies Abell 85
We present a catalogue of velocities for 551 galaxies (and give the
coordinates of 39 stars misclassified as galaxies in our photometric plate
catalogue) in a region covering about 100'100' (0.940.94 Mpc
for an average redshift of 0.0555, assuming H=50 km s
Mpc) in the direction of the rich cluster Abell 85. This catalogue
includes previously published redshifts by Beers et al. (1991) and Malumuth et
al. (1992), together with our 367 new measurements. A total of 305 galaxies
have velocities in the interval 13350-20000 km s, and will be considered
as members of the cluster. Abell 85 therefore becomes one of the clusters with
the highest number of measured redshifts; its optical properties are being
investigated in a companion paper.Comment: Accepted for publication in A&AS, Table 4 available in electronic
form onl
A hot X-ray filament associated with A3017 galaxy cluster
Recent simulations and observations have shown large scale filaments in the
cosmic web connecting nodes, with accreting materials (baryonic and dark
matter) flowing through them. Current high sensitivity observations also show
that the propagation of shocks through filaments can heat them up, and make
filaments visible between two or more galaxy clusters or around massive
clusters, based on optical and/or X-ray observations. We are reporting here the
special case of the cluster A3017 associated with a hot filament. The
temperature of the filament is 3.4 ~keV and its length is
1 Mpc. We have analysed its archival {\it Chandra} data and report
various properties. We also analysed GMRT 235/610 MHz radio data. Radio
observations have revealed symmetric two-sided lobes which fill cavities in the
A3017 cluster core region, associated with central AGN. In the radio map, we
also noticed a peculiar linear vertical radio structure in the X-ray filament
region which might be associated with a cosmic filament shock. This radio
structure could be a radio phoenix or old plasma where an old relativistic
population is re-accelerated by shock propagation. Finally we put an upper
limit on the radio luminosity of the filament region
A Redshift Survey of Nearby Galaxy Groups: the Shape of the Mass Density Profile
We constrain the mass profile and orbital structure of nearby groups and
clusters of galaxies. Our method yields the joint probability distribution of
the density slope n, the velocity anisotropy beta, and the turnover radius r0
for these systems. The measurement technique does not use results from N-body
simulations as priors. We incorporate 2419 new redshifts in the fields of 41
systems of galaxies with z < 0.04. The new groups have median velocity
dispersion sigma=360 km/s. We also use 851 archived redshifts in the fields of
8 nearly relaxed clusters with z < 0.1. Within R < 2 r200, the data are
consistent with a single power law matter density distribution with slope n =
1.8-2.2 for systems with sigma < 470 km/s, and n = 1.6-2.0 for those with sigma
> 470 km/s (95% confidence). We show that a simple, scale-free phase space
distribution function f(E,L^2) ~ (-E)^(alpha-1/2) L^(-2 \beta) is consistent
with the data as long as the matter density has a cusp. Using this DF, matter
density profiles with constant density cores (n=0) are ruled out with better
than 99.7% confidence.Comment: 22 pages; accepted for publication in the Astrophysical Journa
Balmer Line Variations in the Radio-Loud AGN PG 1512+370
We present spectroscopic observations of the quasar PG~1512+370, covering the
Hbeta line spectral range and collected at moderate resolution (2-7 A FWHM)
from 1988 to 1996. The observations show that the blue wing of the Hbeta broad
profile component has changed significantly in flux and shape between 1988 and
1990 and between 1995 and 1996. A displaced blue peak on the Hbeta profile,
visible in 1988, but not in the 1990-1995 spectra, is revealed again in one of
the spectra obtained in 1996. The blue peak (in both the 1988 and 1996 spectra)
is centered at Delta v_r ~ -3000 +/- 500 km/s from the rest frame defined by
the narrow component of Hbeta, and the OIII lambda4959,5007 lines.
We discuss several conflicting interpretations of the data. We find that the
variability of the Hbeta blue wing is consistent with Balmer line emission from
regions whose motion is predominantly radial, if variations of the blue wing
are a response to continuum changes. Alternatively, we note that observed Hbeta
line profile variations are consistent with a variable line component as in a
``binary black hole'' scenario. More frequent observations of Hbeta are needed
to distinguish among these hypotheses.Comment: 19 pages, 1 embedded figure (eps), to appear in ApJ 49
Coma cluster object populations down to M_R~-9.5
This study follows a recent analysis of the galaxy luminosity functions and
colour-magnitude red sequences in the Coma cluster (Adami et al. 2007). We
analyze here the distribution of very faint galaxies and globular clusters in
an east-west strip of arcmin crossing the Coma cluster
center (hereafter the CS strip) down to the unprecedented faint absolute
magnitude of M. This work is based on deep images obtained at the
CFHT with the CFH12K camera in the B, R, and I bands. The analysis shows that
the observed properties strongly depend on the environment, and thus on the
cluster history. When the CS is divided into four regions, the westernmost
region appears poorly populated, while the regions around the brightest
galaxies NGC 4874 and NGC 4889 (NGC 4874 and NGC 4889 being masked) are
dominated by faint blue galaxies. They show a faint luminosity function slope
of -2, very significantly different from the field estimates. Results are
discussed in the framework of galaxy destruction (which can explain part of the
very faint galaxy population) and of structures infalling on to Coma.Comment: To be published in A&
A Turn-over in the Galaxy Luminosity Function of the Coma Cluster Core?
Our previous study of the faint end (R21.5) of the galaxy luminosity
function (GLF) was based on spectroscopic data in a small region near the Coma
cluster center. In this previous study Adami et al. (1998) suggested, with
moderate statistical significance, that the number of galaxies actually
belonging to the cluster was much smaller than expected. This led us to
increase our spectroscopic sample. Here, we have improved the statistical
significance of the results of the Coma GLF faint end study (R22.5) by
using a sample of 85 redshifts. This includes both new spectroscopic data and a
literature compilation. The relatively small number of faint galaxies belonging
to Coma that was suggested by Adami et al. (1998) and Secker et al. (1998) has
been confirmed with these new observations. We also confirm that the
color-magnitude relation is not well suited for finding the galaxies inside the
Coma cluster core, close to the center at magnitudes fainter than R19. We
show that there is an enhancement in the Coma line of sight of field galaxies
compared to classical field counts. This can be explained by the contribution
of groups and of a distant cluster along the line of sight. The
result is that the Coma GLF appears to turn-over or at least to become flat for
the faint galaxies. We suggest that this is due to environmental effects.Comment: 8 pages, 6 postscript figures, accepted in A&A, new table 1, updated
figure
A kinematical analysis of NGC 2992
We present long slit spectroscopy for the [OIII] and H wavelength
ranges along nine different position angles for the Sa Seyfert 1.9 galaxy NGC
2992. Double profiles are present in several regions, suggesting that the gas
is not simply following galaxy rotation. A simple kinematical model, which
takes into account circular rotation together with a constant radial outflow,
seems to be a good approximation to account for the observed kinematics.Comment: Accepted for publication in Astronomy & Astrophysic
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