40 research outputs found
The Type II Supernova Rate in z~0.1 Galaxy Clusters from the Multi-Epoch Nearby Cluster Survey
We present 7 spectroscopically confirmed Type II cluster supernovae (SNeII)
discovered in the Multi-Epoch Nearby Cluster Survey, a supernova survey
targeting 57 low redshift 0.05 < z < 0.15 galaxy clusters with the
Canada-France-Hawaii Telescope. We find the rate of Type II supernovae within
the virial radius of these galaxy clusters to be 0.026 (+0.085 -0.018 stat;
+0.003 -0.001 sys) SNe per century per 1e10 solar masses. Surprisingly, one
SNII is in a red sequence host galaxy that shows no clear evidence of recent
star formation. This is unambiguous evidence in support of ongoing, low-level
star formation in at least some cluster elliptical galaxies, and illustrates
that galaxies that appear to be quiescent cannot be assumed to host only Type
Ia SNe. Based on this single SNII we make the first measurement of the SNII
rate in red sequence galaxies, and find it to be 0.007 (+0.014 -0.007 stat;
+0.009 -0.001 sys) SNe per century per 1e10 solar masses. We also make the
first derivation of cluster specific star formation rates (sSFR) from cluster
SNII rates. We find that for all galaxy types, sSFR is 5.1 (+15.8 -3.1 stat;
+0.9 -0.9 sys) solar masses per year per 1e12 solar masses, and for red
sequence galaxies only, it is 2.0 (+4.2 -0.9 stat; +0.4 -0.4 sys) solar masses
per year per 1e12 solar masses. These values agree with SFRs measured from
infrared and ultraviolet photometry, and H-alpha emission from optical
spectroscopy. Additionally, we use the SFR derived from our SNII rate to show
that although a small fraction of cluster Type Ia SNe may originate in the
young stellar population and experience a short delay time, these results do
not preclude the use of cluster SNIa rates to derive the late-time delay time
distribution for SNeIa.Comment: 16 pages, 5 tables, 6 figures, 2 appendices; accepted to Ap
Halo mass - concentration relation from weak lensing
We perform a statistical weak lensing analysis of dark matter profiles around
tracers of halo mass from galactic- to cluster-size halos. In this analysis we
use 170,640 isolated ~L* galaxies split into ellipticals and spirals, 38,236
groups traced by isolated spectroscopic Luminous Red Galaxies (LRGs) and 13,823
MaxBCG clusters from the Sloan Digital Sky Survey (SDSS) covering a wide range
of richness. Together these three samples allow a determination of the density
profiles of dark matter halos over three orders of magnitude in mass, from
10^{12} M_{sun} to 10^{15} M_{sun}. The resulting lensing signal is consistent
with an NFW or Einasto profile on scales outside the central region. We find
that the NFW concentration parameter c_{200b} decreases with halo mass, from
around 10 for galactic halos to 4 for cluster halos. Assuming its dependence on
halo mass in the form of c_{200b} = c_0 [M/(10^{14}M_{sun}/h)]^{\beta}, we find
c_0=4.6 +/- 0.7 (at z=0.22) and \beta=0.13 +/- 0.07, with very similar results
for the Einasto profile. The slope (\beta) is in agreement with theoretical
predictions, while the amplitude is about two standard deviations below the
predictions for this mass and redshift, but we note that the published values
in the literature differ at a level of 10-20% and that for a proper comparison
our analysis should be repeated in simulations. We discuss the implications of
our results for the baryonic effects on the shear power spectrum: since these
are expected to increase the halo concentration, the fact that we see no
evidence of high concentrations on scales above 20% of the virial radius
suggests that baryonic effects are limited to small scales, and are not a
significant source of uncertainty for the current weak lensing measurements of
the dark matter power spectrum. [ABRIDGED]Comment: 17 pages, 5 figures, accepted to JCAP pending minor revisions that
are included in v2 here on arXi
The bright galaxy population of five medium redshift clusters. II. Quantitative Galaxy Morphology
Aims: Following the study already presented in our previous paper, based on
the Nordic Optical Telescope (NOT) sample, which consists of five clusters of
galaxies within the redshift range 0.18 z 0.25, imaged in the
central 0.5-2 Mpc in very good seeing conditions, we have studied the
quantitative morphology of their bright galaxy population
Methods: We have analyzed the surface brightness profiles of the galaxy
population in those clusters. Previously, we have performed simulations in
order to check the reliability of the fits. We have also derived a quantitative
morphological classification.
Results: The structural parameters derived from these analysis have been
analyzed. We have obtained that the structural parameters of E/S0 galaxies are
similar to those showed by galaxies in low redshift clusters. However, the disc
scales are different. In particular, the scales of the discs of galaxies at
medium redshift clusters are statistically different than those located in
similar galaxies in the Coma cluster. But, the scales of the discs of galaxies
in medium redshift clusters are similar to nearby field galaxies.
Conclusions: The results suggest that the evolution of the disc component of
galaxies in clusters is faster than in field ones. Mechanisms like galaxy
harassment showing timescales of Gyr could be the responsible of this
disc scale evolution. This indicates that spiral galaxies in clusters have
suffered a strong evolution in the last 2.5 Gyr or that Coma is in some way
anomalous.Comment: 13 pages, 10 figures, Accepted for publication in A&
Far Ultraviolet Emission in the A2597 and A2204 Brightest Cluster Galaxies
We use the Hubble Space Telescope ACS/SBC and Very Large Telescope FORS
cameras to observe the Brightest Cluster Galaxies in Abell 2597 and Abell 2204
in the far-ultraviolet (FUV) F150LP and optical U, B, V, R, I Bessel filters.
The FUV and U band emission is enhanced in bright, filamentary structures
surrounding the BCG nuclei. These filaments can be traced out to 20 kpc from
the nuclei in the FUV. Excess FUV and U band light is determined by removing
emission due to the underlying old stellar population and mapped with 1 arcsec
spatial resolution over the central 20 kpc regions of both galaxies. We find
the FUV and U excess emission to be spatially coincident and a stellar
interpretation requires the existence of a significant amount of 10000-50000 K
stars. Correcting for nebular continuum emission and dust intrinsic to the BCG
further increases the FUV to U band emission ratio and implies that stars alone
may not suffice to explain the observations. However, lack of detailed
information on the gas and dust distribution and extinction law in these
systems prevents us from ruling out a purely stellar origin. Non-stellar
processes, such as the central AGN, Scattering, Synchrotron and Bremsstrahlung
emission are investigated and found to not be able to explain the FUV and U
band measurements in A2597. Contributions from non-thermal processes not
treated here should be investigated. Comparing the FUV emission to the optical
H-alpha line emitting nebula shows good agreement on kpc-scales in both A2597
and A2204. In concordance with an earlier investigation by O'Dea et al. (2004)
we find that O-stars can account for the ionising photons necessary to explain
the observed H-alpha line emission.Comment: accepted by mnra
The impact of mergers on relaxed X-ray clusters - III. Effects on compact cool cores
(Abridged) We use the simulations presented in Poole et al. 2006 to examine
the effects of mergers on compact cool cores in X-ray clusters. We propose a
scheme for classifying the morphology of clusters based on their surface
brightness and entropy profiles. Three dominant morphologies emerge: two
hosting compact cores and central temperatures which are cool (CCC systems) or
warm (CWC systems) and one hosting extended cores which are warm (EWC systems).
We find that CCC states are disrupted only after direct collisions between
cluster cores in head-on collisions or during second pericentric passage in
off-axis mergers. By the time they relax, our remnant cores have generally been
heated to warm core (CWC or EWC) states but subsequently recover CCC states.
The only case resulting in a long-lived EWC state is a slightly off-axis 3:1
merger for which the majority of shock heating occurs during the accretion of a
low-entropy stream formed from the disruption of the secondary's core.
Compression prevents core temperatures from falling until after relaxation thus
explaining the observed population of relaxed CWC systems with no need to
invoke AGN feedback. The morphological segregation observed in the L_x-T_x and
beta-r_c scaling relations is reflected in our simulations as well. However,
none of the cases we have studied produce sufficiently high remnant central
entropies to account for the most under-luminous EWC systems observed. Lastly,
systems which initially host central metallicity gradients do not yield merger
remnants with flat metallicity profiles. Taken together, these results suggest
that once formed, compact core systems are remarkably stable against disruption
from mergers. It remains to be demonstrated exactly how the sizable observed
population of extended core systems was formed.Comment: 19 pages, 8 figures, submitted for publication in MNRA
A Giant Metrewave Radio Telescope/Chandra view of IRAS 09104+4109: A type 2 QSO in a cooling flow
IRAS 09104+4109 is a rare example of a dust enshrouded type 2 QSO in the
centre of a cool-core galaxy cluster. Previous observations of this z=0.44
system showed that as well as powering the hyper-luminous infrared emission of
the cluster-central galaxy, the QSO is associated with a double-lobed radio
source. However, the steep radio spectral index and misalignment between the
jets and ionised optical emission suggested that the orientation of the QSO had
recently changed. We use a combination of new, multi-band Giant Metrewave Radio
Telescope observations and archival radio data to confirm that the jets are no
longer powered by the QSO, and estimate their age to be 120-160 Myr. This is in
agreement with the ~70-200 Myr age previously estimated for star-formation in
the galaxy. Previously unpublished Very Long Baseline Array data reveal a 200
pc scale double radio source in the galaxy core which is more closely aligned
with the current QSO axis and may represent a more recent period of jet
activity. These results suggest that the realignment of the QSO, the cessation
of jet activity, and the onset of rapid star-formation may have been caused by
a gas-rich galaxy merger. A Chandra X-ray observation confirms the presence of
cavities associated with the radio jets, and we estimate the energy required to
inflate them to be ~7.7x10^60 erg. The mechanical power of the jets is
sufficient to balance radiative cooling in the cluster, provided they are
efficiently coupled to the intra-cluster medium (ICM). We find no evidence of
direct radiative heating and conclude that the QSO either lacks the radiative
luminosity to heat the ICM, or that it requires longer than 100-200 Myr to
significantly impact its environment. [Abridged]Comment: 23 pages, 18 figures and 7 tables. Accepted for publication in MNRA
Planck intermediate results. III. The relation between galaxy cluster mass and Sunyaev-Zeldovich signal
We examine the relation between the galaxy cluster mass M and
Sunyaev-Zeldovich (SZ) effect signal D_A^2 Y for a sample of 19 objects for
which weak lensing (WL) mass measurements obtained from Subaru Telescope data
are available in the literature. Hydrostatic X-ray masses are derived from
XMM-Newton archive data and the SZ effect signal is measured from Planck
all-sky survey data. We find an M_WL-D_A^2 Y relation that is consistent in
slope and normalisation with previous determinations using weak lensing masses;
however, there is a normalisation offset with respect to previous measures
based on hydrostatic X-ray mass-proxy relations. We verify that our SZ effect
measurements are in excellent agreement with previous determinations from
Planck data. For the present sample, the hydrostatic X-ray masses at R_500 are
on average ~ 20 per cent larger than the corresponding weak lensing masses, at
odds with expectations. We show that the mass discrepancy is driven by a
difference in mass concentration as measured by the two methods, and, for the
present sample, the mass discrepancy and difference in mass concentration is
especially large for disturbed systems. The mass discrepancy is also linked to
the offset in centres used by the X-ray and weak lensing analyses, which again
is most important in disturbed systems. We outline several approaches that are
needed to help achieve convergence in cluster mass measurement with X-ray and
weak lensing observations.Comment: 19 pages, 9 figures, matches accepted versio
Residual Cooling and Persistent Star Formation amid AGN Feedback in Abell 2597
New Chandra X-ray and Herschel FIR observations enable a multiwavelength
study of active galactic nucleus (AGN) heating and intracluster medium (ICM)
cooling in the brightest cluster galaxy of Abell 2597. The new Chandra
observations reveal the central < 30 kiloparsec X-ray cavity network to be more
extensive than previously thought, and associated with enough enthalpy to
theoretically inhibit the inferred classical cooling flow. Nevertheless, we
present new evidence, consistent with previous results, that a moderately
strong residual cooling flow is persisting at 4%-8% of the classically
predicted rates in a spatially structured manner amid the feedback-driven
excavation of the X-ray cavity network. New Herschel observations are used to
estimate warm and cold dust masses, a lower-limit gas-to-dust ratio, and a star
formation rate consistent with previous measurements. The cooling time profile
of the ambient X-ray atmosphere is used to map the locations of the
observational star formation entropy threshold as well as the theoretical
thermal instability threshold. Both lie just outside the < 30 kpc central
region permeated by X-ray cavities, and star formation as well as ionized and
molecular gas lie interior to both. The young stars are distributed in an
elongated region that is aligned with the radio lobes, and their estimated ages
are both younger and older than the X-ray cavity network, suggesting both
jet-triggered as well as persistent star formation over the current AGN
feedback episode. Bright X-ray knots that are coincident with extended Ly-alpha
and FUV continuum filaments motivate a discussion of structured cooling from
the ambient hot atmosphere along a projected axis that is perpendicular to
X-ray cavity and radio axis. We conclude that the cooling ICM is the dominant
contributor of the cold gas reservoir fueling star formation and AGN activity
in the Abell 2597 BCG.Comment: 20 pages, 7 figures; Accepted for publication in MNRA
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Viral testing of 10 cases of Theiler's disease and 37 in-contact horses in the absence of equine biologic product administration: A prospective study (2014-2018)
Background A novel equine parvovirus (EqPV-H) was recently discovered in the equine liver with Theiler's disease. Objectives To determine the prevalence of EqPV-H infection in naturally occurring Theiler's disease cases and in-contact horses in the absence of historical equine biologic product administration. Animals Ten cases of Theiler's disease from 6 separate properties were included in the study, based on the criteria of acute onset of clinical signs of liver failure with laboratory or histopathologic findings characteristic of Theiler's disease and no history of receiving an equine biologic product within the preceding 4 months. In addition, 37 in-contact horses from 4 of the 6 properties were screened for EqPV-H infection and hepatitis. Methods In prospective case series, cases were diagnosed with Theiler's disease by the attending veterinarian and were tested for EqPV-H by PCR of liver or serum. In-contact horses were assessed via serum chemistry and PCR at the attending veterinarian's discretion. Hepatitis was defined as serum gamma-glutamyltransferase activity above reference interval. The association of EqPV-H with hepatitis was determined by Fisher's exact test. Results Nine of 10 (90%) Theiler's disease cases and 54% of tested in-contact horses were EqPV-H positive. Hepatitis was significantly associated with EqPV-H infection (P = .036). Conclusions and Clinical Importance Although further study is required to identify EqPV-H as the causative agent of Theiler's disease, EqPV-H appears strongly associated with cases of fatal Theiler's disease and subclinical hepatitis in horses in contact with those cases. The prevalence of EqPV-H infection on affected properties can be high