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Notes for object ABELL 2744

4 note(s) found in NED.


1. 2007AJ....134..466K
Re:AC 118
AC 118 (A2744) is a richness class 3, Bautz-Morgan type III cluster at a
redshift of 0.31. This cluster has two main clumps of galaxies separated by 1
h^-1^_70_ Mpc, with a third bright elliptical in a small group that is 1.2
h^-1^_70_ Mpc distant from the center of the other clumps. The BCG is 0.23 +/-
0.04 mag brighter than the second-ranked galaxy. The Chandra X-ray data suggest
that there are probably three clusters here, at least two of which are
interacting. The gas distribution, along with abundance ratios, suggests that
the third, smaller group might be the core of one of the interacting clusters
that has moved beyond the scene of the interaction where the hot gas is
detected. From velocity measurements Girardi & Mezzetti (2001) also found two
populations of galaxies with distinctly different velocity dispersions. The
presence of a large radio halo and radio relic are yet more evidence for
dynamical activity in this cluste r (Govoni et al. 2001). Mass estimates for
this cluster range from ~3 * 10^13^ M_sun_ from X-ray data to ~3 * 10^15^ M_sun_
from the velocity dispersion data. This cluster clearly violates assumptions of
sphericity and hydrostatic equilibrium, which leads to the large variations. The
two velocity-dispersion peaks have a total mass of (38 +/- 37) * 10^14^
h^-1^_70_ M_sun_; we adopt this mass throughout the paper.
AC 118, at the same redshift as AC 114, also shows a significant fraction of
blue galaxies, which leads to a wider red cluster sequence (1 {sigma} = 0.3 mag)
than at lower redshifts. We adopt the Busarello et al. (2002) R- and V-band
luminosity distributions based on photometric redshifts and background counts
from a nearby, large-area survey. Integrating the luminosity distribution from
very dim dwarf galaxies (M_R_ = -11.6) to infinity gives a total luminosity for
AC 118 of (4.5 +/- 0.2) * 10^11 L_sun_ in V and (4.2 +/- 0.4) * 10^12^ L_sun_ in
the r band inside of 0.25r_virial_. For the purpose of comparison with other
clusters, we adopt the cluster flux from the CMD, which gives (5.4 +/- 1.6) *
10^11^ L_sun_ in B and (4.4 +/- 0.1) * 10^12^ L_sun_ in r inside of 0.94
h^-1^_70_ Mpc, which is one-quarter of the virial radius of this cluster.
Figure 13 shows the relevant plots for this cluster. There are at least
two, if not three groupings of diffuse light that do not have a common center.
The possible third is mostly obscured behind the mask of a saturated star. We
are unable to fit a centralized profile to this ICL. The total flux in the ICL
as measured in manually placed elliptical annuli is (7.0 +/- 1.0) * 10^11^
L_sun_ in r and (6.7 +/- 1.7) * 10^10^ L_sun_ in B, which makes for ICL
fractions of 14% +/- 5% in r and 11% +/- 5% in B. We estimate the color of the
ICL to be V - r [IMAGE] 1.0 +/- 0.8, which is significantly redder (0.6 mag)
than the RCS. We have no color profile information.

2. 2002ApJ...576..688B
Re:ABELL 2744
A2744.-The most distant cluster of this sample (z = 0.31, Abell richness
class 3) has clear evidence of strong soft excess emission in our 13.8
ks PSPC observation, at the level of ~50%. The cluster is a strong
X-ray emitter and is detected out to a radius of ~2 Mpc. Detected soft
excess emission implies thermal and nonthermal luminosities of order
10^43^ ergs s^-1^ in the 0.2-0.4 keV band (see Table 3), the highest to
date.

3. 2001A&A...369..441G
Re:ABELL 2744
3.3 A2744
The radio halo in A2744 was found by Giovannini et al. (1999) during a
search for new radio halos and cluster relics among the candidates
extracted from the NRAO VLA Sky Survey (NVSS, Condon et al. 1998). The
cluster A2744, located at a redshift of 0.308 (Struble & Rood 1999), was
re-observed with the VLA at 1.4 GHz in C and D configuration (Govoni et al.
2001, in preparation). We analyzed the resulting map, which has an angular
resolution of 50" x 50".
The X-ray image results from 13600 s exposure time and was obtained from
Rosat PSPC archive data, by binning the photon events in a two dimensional
grid and then smoothing with a Gaussian function with {sigma} = 30". The
X-ray background, of about 1.0 x 10^-7^ cts sec^-1^ arcsec^-2^, was
determined by fitting the X-ray surface brightness profile with a
hydrostatic isothermal model (Cavaliere & Fusco-Femiano 1981).
The X-ray image shows morphological substructures, which are possible
indication of a recent merger.
In Fig. 8 we present the overlay between the radio (contours) and the
X-ray image (grey-scale) of A2744. The elongated diffuse radio emission in
the peripheral North-East region of the cluster is classified as a cluster
relic, and, therefore, excluded from the analysis.
We performed the analysis of the radio and the X-ray morphology using a
grid with a cell size of 51" (285 kpc), and concentric rings with a
thickness of 30". Since this cluster is at a large distance, the gridding
corresponds to cells of large linear size. However, both the X-ray emission
and the radio halo are well resolved (FWHM of X-ray and radio profiles
~170" from Fig. 10). Therefore, although the number of statistically
independent cells and rings in the cluster is lower than in other clusters,
it allows us to perform a quantitative analysis.
The absence of X-ray point sources with an optical or radio counterpart
doesn't allow us to check if the offset between the X-ray and the radio
peaks is real or not. We note that the offset (~30") is within the cell
size (51").
Results are presented in Figs. 9 and 10. The shape of the two brightness
profiles is perfectly coincident and in this case we get a linear
F_Radio_ - F_X_ relation (a = 0.24 +/- 0.07, b = 0.99 +/- 0.05).

4. 1999NewA....4..141G
Re:ABELL 2744
A 2744. Beside the centrally located radio emission, there is also
extended structure toward NE which could be either a relic or still
related to the halo.


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