512 research outputs found
The census of nuclear activity of late-type galaxies in the Virgo cluster
The first spectroscopic census of AGNs associated to late-type galaxies in
the Virgo cluster is carried on by observing 213 out of a complete set of 237
galaxies more massive than M_dyn>10^{8.5} solar masses. Among them, 77 are
classified as AGNs (including 21 transition objects, 47 LINERs and 9 Seyferts),
and comprize 32% of the late-type galaxies in Virgo. Due to spectroscopic
incompleteness at most 21 AGNs are missed in the survey, so that the fraction
would increase up to 41%. Using corollary Near-IR observations, that enable us
to estimate galaxies dynamical masses, it is found that AGNs are hosted
exclusively in massive galaxies, i.e. M_dyn\gsim 10^{10} solar masses. Their
frequency increases steeply with the dynamical mass from zero at
M_dyn\approx10^{9.5} solar masses to virtually 1 at M_dyn>10^{11.5} solar
masses. These frequencies are consistent with the ones of low luminosity AGNs
found in the general field by the SDSS. Massive galaxies that harbor AGNs
commonly show conspicuous r-band star-like nuclear enhancements. Conversely
they often, but not necessarily contain massive bulges. Few well known AGNs
(e.g. M61, M100, NGC4535) are found in massive Sc galaxies with little or no
bulge. The AGN fraction seems to be only marginally sensitive to galaxy
environment. We infer the black hole masses using the known scaling relations
of quiescent black holes. No black holes lighter than \msol are
found active in our sample.Comment: The paper contains 13 figures and 5 tables; accepted for publication
in MNRA
The Arecibo Galaxy Environment Survey V : The Virgo Cluster (I)
We present 21 cm observations of a 10 2 degree region in the Virgo
cluster, obtained as part of the Arecibo Galaxy Environment Survey. 289 sources
are detected over the full redshift range (-2,000 + 20,000
km/s) with 95 belonging to the cluster ( 3,000 km/s). We combine
our observations with data from the optically selected Virgo Cluster Catalogue
(VCC) and the Sloan Digital Sky Survey (SDSS). Most of our detections can be
clearly associated with a unique optical counterpart, and 30% of the cluster
detections are new objects fainter than the VCC optical completeness limit. 7
detections may have no optical counterpart and we discuss the possible origins
of these objects. 7 detections appear associated with early-type galaxies. We
perform HI stacking on the HI-undetected galaxies listed in the VCC in this
region and show that they must have significantly less gas than those actually
detected in HI. Galaxies undetected in HI in the cluster appear to be really
devoid of gas, in contrast to a sample of field galaxies from ALFALFA.Comment: 23 pages, 22 figures, 4 table
1.65 micron H-band Surface Photometry of Galaxies. X: Structural and Dynamical Properties of Elliptical Galaxies
We analyse the structural and dynamical properties of a sample of 324 nearby
elliptical and dwarf elliptical galaxies observed during an extensive NIR
survey in H-band (1.65 micron). The Fundamental Plane (FP) is determined and a
significant tilt is assessed. The origins of such a tilt are investigated by
means of a spherically symmetric, isotropic pressure supported dynamical model
relying on the observed surface brightness profiles. The systematic variation
of the shape coefficient converting the measured central velocity dispersion into the virial rms velocity is found to be the main
cause of the tilt, due to aperture effects. Moreover the ratio between the
dynamical mass and the total H-band luminosity turns out to be
roughly constant along the luminosity sequence of ellipticals: H-band
luminosity is therefore a reliable and cheap estimator of the dynamical mass of
the Es.Comment: 28 pages, 6 figures, accepted for publication on Ap
A highly-ionized region surrounding SN Refsdal revealed by MUSE
Supernova (SN) Refsdal is the first multiply-imaged, highly-magnified, and
spatially-resolved SN ever observed. The SN exploded in a highly-magnified
spiral galaxy at z=1.49 behind the Frontier Fields Cluster MACS1149, and
provides a unique opportunity to study the environment of SNe at high z. We
exploit the time delay between multiple images to determine the properties of
the SN and its environment, before, during, and after the SN exploded. We use
the integral-field spectrograph MUSE on the VLT to simultaneously target all
observed and model-predicted positions of SN Refsdal. We find MgII emission at
all positions of SN Refsdal, accompanied by weak FeII* emission at two
positions. The measured ratios of [OII] to MgII emission of 10-20 indicate a
high degree of ionization with low metallicity. Because the same high degree of
ionization is found in all images, and our spatial resolution is too coarse to
resolve the region of influence of SN Refsdal, we conclude that this high
degree of ionization has been produced by previous SNe or a young and hot
stellar population. We find no variability of the [OII] line over a period of
57 days. This suggests that there is no variation in the [OII] luminosity of
the SN over this period, or that the SN has a small contribution to the
integrated [OII] emission over the scale resolved by our observations.Comment: 5 pages, 4 figures, accepted for publication in A&
The story of supernova 'Refsdal' told by MUSE
We present MUSE observations in the core of the HFF galaxy cluster MACS
J1149.5+2223, where the first magnified and spatially-resolved multiple images
of SN 'Refsdal' at redshift 1.489 were detected. Thanks to a DDT program with
the VLT and the extraordinary efficiency of MUSE, we measure 117 secure
redshifts with just 4.8 hours of total integration time on a single target
pointing. We spectroscopically confirm 68 galaxy cluster members, with redshift
values ranging from 0.5272 to 0.5660, and 18 multiple images belonging to 7
background, lensed sources distributed in redshifts between 1.240 and 3.703.
Starting from the combination of our catalog with those obtained from extensive
spectroscopic and photometric campaigns using the HST, we select a sample of
300 (164 spectroscopic and 136 photometric) cluster members, within
approximately 500 kpc from the BCG, and a set of 88 reliable multiple images
associated to 10 different background source galaxies and 18 distinct knots in
the spiral galaxy hosting SN 'Refsdal'. We exploit this valuable information to
build 6 detailed strong lensing models, the best of which reproduces the
observed positions of the multiple images with a rms offset of only 0.26". We
use these models to quantify the statistical and systematic errors on the
predicted values of magnification and time delay of the next emerging image of
SN 'Refsdal'. We find that its peak luminosity should should occur between
March and June 2016, and should be approximately 20% fainter than the dimmest
(S4) of the previously detected images but above the detection limit of the
planned HST/WFC3 follow-up. We present our two-dimensional reconstruction of
the cluster mass density distribution and of the SN 'Refsdal' host galaxy
surface brightness distribution. We outline the roadmap towards even better
strong lensing models with a synergetic MUSE and HST effort.Comment: 21 pages, 9 figures, 6 tables; accepted for publication in the
Astrophysical Journal - extra information on data analysis added, all model
predictions and results unchange
Blueshifted galaxies in the Virgo Cluster
We examine a sample of 65 galaxies in the Virgo cluster with negative radial
velocities relative to the Local Group. Some features of this sample are
pointed out. All of these objects are positioned compactly within a virial zone
of radius 6{\deg} in the cluster, but their centroid is displaced relative to
the dynamic center of the cluster, M87, by 1.1{\deg} to the northwest. The
dwarf galaxies in this sample are clumped on a scale of ~10' (50 kpc). The
observed asymmetry in the distribution of the blueshifted galaxies may be
caused by infall of a group of galaxies around M86 onto the main body of the
cluster. We offer another attempt to explain this phenomenon, assuming a mutual
tangential velocity of ~300 km/s between the Local Group and the Virgo cluster
owing to their being repelled from the local cosmological void.Comment: 10 pages, 4 figures, 1 table. Published in Astrophysics, Vol. 53, No.
1, pp. 32-41, 201
The Herschel Virgo Cluster Survey: I. Luminosity functions
We describe the Herschel Virgo Cluster Survey (HeViCS) and the first data
obtained as part of the Science Demonstration Phase (SDP). The data cover a
central 4x4 sq deg region of the cluster. We use SPIRE and PACS photometry data
to produce 100, 160, 250, 350 and 500 micron luminosity functions (LFs) for
optically bright galaxies that are selected at 500 micron and detected in all
bands. We compare these LFs with those previously derived using IRAS, BLAST and
Herschel-ATLAS data. The Virgo Cluster LFs do not have the large numbers of
faint galaxies or examples of very luminous galaxies seen previously in surveys
covering less dense environments.Comment: Letter accepted for publication in A&A (Herschel special issue
The Environmental Dependence of the Infrared Luminosity and Stellar Mass Functions
We investigate the dependence of the galaxy infrared luminosity function (LF)
and the associated stellar mass function (SMF) on environment and spectral type
using photometry from the Two Micron All Sky Survey and redshifts from the Las
Campanas Redshift Survey for galaxies brighter than M_J<-19+5 log h. In the
field environment, galaxies with emission lines have LFs with much steeper
faint end slopes (alpha_J=-1.39) than galaxies without emission lines
(alpha_J=-0.59). In the cluster environment, however, even the non-emission
line galaxies have a steep faint-end LF (alpha_J=-1.22). There is also a
significant (95%) difference between the overall cluster and field LFs, . All of these variations are more
pronounced in the SMFs, which we compute by relating the strength of the 4000 A
break in the optical spectra to a mass-to-light ratio.Comment: 14 pages, 13 figures, emulateapj style ApJ, post-referee. Very minor
changes, mostly typographical in natur
The Arecibo Galaxy Environment Survey: II. A HI view of the Abell cluster 1367 and its outskirts
We present 21 cm HI line observations of 5x1 square degrees centered on the
local Abell cluster 1367 obtained as part of the Arecibo Galaxy Environment
Survey. One hundred sources are detected (79 new HI measurements and 50 new
redshifts), more than half belonging to the cluster core and its infalling
region. Combining the HI data with SDSS optical imaging we show that our HI
selected sample follows scaling relations similar to the ones usually observed
in optically selected samples. Interestingly all galaxies in our sample appear
to have nearly the same baryon fraction independently of their size, surface
brightness and luminosity. The most striking difference between HI and
optically selected samples resides in their large scale distribution: whereas
optical and X-ray observations trace the cluster core very well, in HI there is
almost no evidence of the presence of the cluster. Some implications on the
determination of the cluster luminosity function and HI distribution for
samples selected at different wavelength are also discussed.Comment: 22 pages, 15 figures, 4 tables. Accepted for publication on MNRAS
Main Journal. High resolution version of this paper can be downloaded at
http://www.astro.cf.ac.uk/pub/Luca.Cortese/papers/ages_a1367.pdf . Datacubes
and catalogs can be downloaded at http://www.naic.edu/~ages/public_data.htm
The EuroHeart Failure Survey programme—a survey on the quality of care among patients with heart failure in Europe Part 2: treatment
National surveys suggest that treatment of heart failure in daily practice differs from guidelines and is characterized by underuse of recommended medications. Accordingly, the Euro, Heart Failure Survey was conducted to ascertain how patients hospitalized for heart failure are managed in Europe and if national variations occur in the treatment of this condition.
Methods The survey screened discharge summaries of 11 304 patients over a 6-week period in 115 hospitals from 24 countries belonging to the ESC to study their medical treatment.
Results Diuretics (mainly loop diuretics) were prescribed in 86.9% followed by ACE inhibitors (61.8%), beta-blockers (36.9%), cardiac glycosides (35.7%), nitrates (32.1%), calcium. channel blockers (21.2%) and spironolactone (20.5%). 44.6% of the population used four or more different drugs. Only 17.2% were under the combination of diuretic, ACE inhibitors and beta-blockers. Important local variations were found in the rate of prescription of ACE inhibitors and particularly beta-blockers. Daily dosage of ACE inhibitors and particularly of beta-blockers was on average below the recommended target dose. Modelling-analysis of the prescription of treatments indicated that the aetiology of heart failure, age, co-morbid factors and type of hospital ward influenced the rate of prescription. Age 70 years, in patients with respiratory disease and increased in cardiology wards, in ischaemic heart failure and in mate subjects. Prescription of cardiac glycosides was significantly increased in patients with supraventricular tachycardia/atrial fibrillation. Finally, the rate of prescription of antithrombotic agents was increased in the presence of supraventricular arrhythmia, ischaemic heart disease, mate subjects but was decreased in patients over 70.
Conclusion Our results suggest that the prescription of recommended medications including ACE inhibitors and beta-blockers remains limited and that the daily dosage remains tow, particularly for beta-blockers. The survey also identifies several important factors including age, gender, type of hospital ward, co morbid factors which influence the prescription of heart failure medication at discharge
- …