280 research outputs found
Analyse cinématique de l'hydrogène ionisé et étude du gaz ionisé diffus de trois galaxies du Groupe Sculpteur : NGC253, NGC300 et NGC247
Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal
A volume-limited sample of X-ray galaxy groups and clusters - II. X-ray cavity dynamics
We present the results of our study of a volume-limited sample (z <= 0.071)
of 101 X-ray galaxy groups and clusters, in which we explore the X-ray cavity
energetics. Out of the 101 sources in our parent sample, X-ray cavities are
found in 30 of them, all of which have a central cooling time of less than3
Gyr. New X-ray cavities are detected in three sources. We focus on the subset
of sources that have a central cooling time of less than 3 Gyr, whose active
galactic nucleus (AGN) duty cycle is approximately 61 percent (30/49). This
rises to over 80 percent for a central cooling time of less than 0.5 Gyr. When
projection effects and central radio source detection rates are considered, the
actual duty cycle is probably much higher. In addition, we show that data
quality strongly affects the detection rates of X-ray cavities. After
calculating the cooling luminosity and cavity powers of each source with
cavities, it is evident that the bubbling process induced by the central AGN
has to be, on average, continuous, to offset cooling. We find that the radius
of the cavities, r, loosely depends on the ambient gas temperature as T^0.5,
above about 1.5 keV, with much more scatter below that temperature. Finally, we
show that, at a given location in a group or cluster, larger bubbles travel
faster than smaller ones. This means that the bubbles seen at larger distances
from cluster cores could be the result of the merging of several smaller
bubbles, produced in separate AGN cycles.Comment: Accepted for publication in MNRAS; 26 pages (including 10 pages of
images), 8 figures, 2 tables. Higher resolution images will be available as
online materia
Unraveling the Mysteries of Galaxy Clusters: Recurrent Inference Deconvolution of X-ray Spectra
In the realm of X-ray spectral analysis, the true nature of spectra has
remained elusive, as observed spectra have long been the outcome of convolution
between instrumental response functions and intrinsic spectra. In this study,
we employ a recurrent neural network framework, the Recurrent Inference Machine
(RIM), to achieve the high-precision deconvolution of intrinsic spectra from
instrumental response functions. Our RIM model is meticulously trained on
cutting-edge thermodynamic models and authentic response matrices sourced from
the Chandra X-ray Observatory archive. Demonstrating remarkable accuracy, our
model successfully reconstructs intrinsic spectra well below the 1-sigma error
level. We showcase the practical application of this novel approach through
real Chandra observations of the galaxy cluster Abell 1550 - a vital
calibration target for the recently launched X-ray telescope, XRISM. This work
marks a significant stride in the domain of X-ray spectral analysis, offering a
promising avenue for unlocking hitherto concealed insights into spectra.Comment: NeurIPS 2023 ML4PS accepted conference abstrac
Deep H{\alpha} Observations of NGC 253: a Very Extended and Possibly Declining Rotation Curve?
This study presents a deep H{\alpha} kinematical analysis of the Sculptor
Group galaxy NGC253. The Fabry-Perot data were taken with the 36-cm Marseille
Telescope in La Silla, Chile, using an EMCCD detector. Typical emission
measures of ~0.1 cm^-6 pc are reached. The observations allow the detection of
the Diffuse Ionized Gas component through [N II] emission at very large radii
of 11.5', 12.8' and 19.0', on the receding side of the galaxy. No H{\alpha}
emission is observed at radii larger than the neutral component (11.5'). The
very extended rotation curve confirms previous results and shows signs of a
significant decline, on the order of 30 per cent vmax . Using the rotation
data, mass models are constructed with and without the outer [N II] data
points, and similar results are found. The declining part of the rotation curve
is very well modeled, and seems to be truly declining.Comment: Accepted for publication in MNRAS. 16 pages, 10 figures, 4 table
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