13 research outputs found
Rich Cluster and Non-Cluster Radio Galaxies & the (P,D) Diagram for a Large Number of FR I and FR II Sources
We present a comparison of the optical and radio properties of radio sources
inside and outside the cores of rich clusters from combined samples of more
than 380 radio sources. We also examine the nature of FR I and FR II host
galaxies, and in particular, we illustrate the importance of selection effects
in propagating the misconception that FR I's and FR II's are found in hosts of
very different optical luminosity. Given the large sample size, we also discuss
the power-size (P,D) distributions as a function of optical luminosity.Comment: to appear in Life Cycles of Radio Galaxies, ed. J. Biretta et al.,
New Astronomy Reviews; 6 pages, including 2 figure
Radio Source Heating in the ICM: The Example of Cygnus A
One of the most promising solutions for the cooling flow problem involves
energy injection from the central AGN. However it is still not clear how
collimated jets can heat the ICM at large scale, and very little is known
concerning the effect of radio lobe expansion as they enter into pressure
equilibrium with the surrounding cluster gas. Cygnus A is one of the best
examples of a nearby powerful radio galaxy for which the synchrotron emitting
plasma and thermal emitting intra-cluster medium can be mapped in fine detail,
and previous observations have inferred possible shock structure at the
location of the cocoon. We use new XMM-Newton observations of Cygnus A, in
combination with deep Chandra observations, to measure the temperature of the
intra-cluster medium around the expanding radio cavities. We investigate how
inflation of the cavities may relate to shock heating of the intra-cluster gas,
and whether such a mechanism is sufficient to provide enough energy to offset
cooling to the extent observed.Comment: To appear in the Proceedings of "Heating vs. Cooling in Galaxies and
Clusters of Galaxies", August 2006, Garching (Germany), Eds. H. Boehringer,
G.W. Pratt, A. Finoguenov, P. Schuecker, Springer-Verlag series "ESO
Astrophysics Symposia", p.101, in press. 8 pages, 3 multiple figure
The lifecycle of powerful AGN outflows
During the course of this conference, much evidence was presented that points
to an intimate connection between the energetic outflows driven by AGN and the
energy budget and quite possibly also the evolution of their gaseous
environments. However, it is still not clear if and how the AGN activity is
triggered by the cooling gas, how long the activity lasts for and how these
effects give rise to the observed distribution of morphologies of the outflows.
In this contribution we concentrate on the high radio luminosity end of the AGN
population. While most of the heating of the environmental gas may be due to
less luminous and energetic outflows, these more powerful objects have a very
profound influence on their surroundings. We will describe a simple model for
powerful radio galaxies and radio-loud quasars that explains the dichotomy of
their large-scale radio morphologies as well as their radio luminosity
function.Comment: 6 pages, contribution to 'Heating vs. coooling in galaxies and galaxy
clusters', Garching 2006, proceedings to be published by Springer (ESO
Astrophysics Symposia), eds. H. Boehringer, P. Schuecker, G.W. Pratt & A.
Finogueno
Detailed Study of the Ursa Major Supercluster of Galaxies Using the 2MASS and SDSS Catalogs
We study the infrared (K_s band) properties of clusters of galaxies in the
Ursa Major supercluster using data from 2MASS (Two-Micron All-Sky Survey) and
SDSS (Sloan Digital Sky Survey). We identified three large filaments with mean
redshifts of z = 0.051, 0.060, and 0.071. All clusters of the supercluster are
located in these filaments. We determined the total K_s-band luminosities and
masses for 11 clusters of galaxies within comparable physical regions (within a
radius R_200 close to the virial radius) using a homogeneous method. We
constructed a combined luminosity function for the supercluster in this region,
which can be described by the Schechter function with the following parameters:
M*_K = -24^m.50 and \alpha = -0.98. The infrared luminosities of the clusters
of galaxies correlate with their masses; the M/L_K ratios of the systems
increase with their masses (luminosities), with most of the Ursa Major clusters
of galaxies (particularly the richer ones) closely following the relations
derived previously for a large sample of clusters and groups of galaxies. The
total mass-to-infrared-luminosity ratio is 52 M_{\odot}/L_{\odot} for six Abell
clusters and 49 M_{\odot}/L_{\odot} for all of the clusters, except Anon2.Comment: 16 pages, 5 figure
The Diversity of Extremely Red Objects
We present a multi-wavelength study of Extremely Red Objects (EROs) employing
deep RIzJHK photometry of a 8.5'x8.5' region to identify 68 EROs with R-K>5.3
and K<20.5 (5-sigma). This is combined with an extremely deep 1.4-GHz radio map
(sigma=3.5uJy), sensitive enough to detect an active galaxy with L_1.4>10^23
W/Hz at z>1 or a SFR of >25Mo/yr. We detect radio emission from 21 EROs at
>12.6uJy and resolve a third of these with our 1.6'' FWHM beam. The SEDs of
most of these radio EROs are consistent with dust-reddened starbursts at z~1.
At z~1 the radio luminosities of these EROs indicate far-infrared luminosities
of L_FIR>10^12 Lo, meaning half are ultraluminous infrared galaxies. We
conclude that >16+/-5% of EROs with K<20.5 are luminous infrared galaxies at
z>1. We also photometrically classify the EROs to investigate the mix of
dusty/active and evolved/passive systems in the radio-undetected EROs. We
suggest that at least 30%, and perhaps up to ~60%, of all EROs with R-K>5.3 and
K1. The SFD in this optically faint
(R>26) population is rho^* (0.1-100Mo)=0.11+/-0.03 Mo/yr/Mpc^3, comparable to
that in H-alpha emitting galaxies at z~1, and greater than that in UV-selected
samples at these epochs. This support the claim of a strong increase in
obscured star formation at high redshifts. Using the observed counts of the
radio-detected EROs we model the break in the K-band number counts of all EROs
at K~19-20 and propose that the passive ERO class dominates the total
population in a narrow range around K~20, with dusty EROs dominating at fainter
magnitudes. [Abridged]Comment: 19 pages, 7 figures, to appear in ApJ Dec 20 2002 v581 n2 revised to
comply with proof cop
Assessment of environments for Mars Science Laboratory entry, descent, and surface operations
The Mars Science Laboratory mission aims to land a car-sized rover on Mars’surface and operate it for at least one Mars year in order to assess whether its field area was ever capable of supporting microbial life. Here we describe the approach used to identify, characterize, and assess environmental risks to the landing and rover surface operations. Novel entry, descent, and landing approaches will be used to accurately deliver the 900-kg rover, including the ability to sense and “fly out” deviations from a best-estimate atmospheric state. A joint engineering and science team developed methods to estimate the range of potential atmospheric states at the time of arrival and to quantitatively assess the spacecraft’s performance and risk given its particular sensitivities to atmospheric conditions. Numerical models are used to calculate the atmospheric parameters, with observations used to define model cases, tune model parameters, and validate results. This joint program has resulted in a spacecraft capable of accessing, with minimal risk, the four finalist sites chosen for their scientific merit. The capability to operate the landed rover over the latitude range of candidate landing sites, and for all seasons, was verified against an analysis of surface environmental conditions described here. These results, from orbital and model data sets, also drive engineering simulations of the rover’s thermal state that are used to plan surface operations