495 research outputs found
Seyfert's Sextet: A Slowly Dissolving Stephan's Quintet?
We present a multiwavelength study of the highly evolved compact galaxy group
known as Seyfert's Sextet (HCG79: SS). We interpret SS as a 2-3 Gyr more
evolved analog of Stephan's Quintet (HCG92: SQ). We postulate that SS formed by
sequential acquisition of 4-5 primarily late-type field galaxies. Four of the
five galaxies show an early-type morphology which is likely the result of
secular evolution driven by gas stripping. Stellar stripping has produced a
massive/luminous halo and embedded galaxies that are overluminous for their
size. These are interpreted as remnant bulges of the accreted spirals. H79d
could be interpreted as the most recent intruder being the only galaxy with an
intact ISM and uncertain evidence for tidal perturbation. In addition to
stripping activity we find evidence for past accretion events. H79b (NGC6027)
shows a strong counter-rotating emission line component interpreted as an
accreted dwarf spiral. H79a shows evidence for an infalling component of gas
representing feedback or possible cross fueling by H79d. The biggest challenge
to this scenario involves the low gas fraction in the group. If SS formed from
normal field spirals then much of the gas is missing. Finally, despite its
advanced stage of evolution, we find no evidence for major mergers and infer
that SS (and SQ) are telling us that such groups coalesce via slow dissolution.Comment: 70 pages, 19 figures, 15 tables - accepted for publication in the
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SEYFERT\u27S SEXTET: A SLOWLY DISSOLVING STEPHAN\u27S QUINTET?
We present a multiwavelength study of the highly evolved compact galaxy group known as Seyfert\u27s Sextet (HCG79: SS). We interpret SS as a 2-3 Gyr more evolved analog of Stephan\u27s Quintet (HCG92: SQ). We postulate that SS formed by sequential acquisition of 4-5 primarily late-type field galaxies. Four of the five galaxies show an early-type morphology which is likely the result of secular evolution driven by gas stripping. Stellar stripping has produced a massive/luminous halo and embedded galaxies that are overluminous for their size. These are interpreted as remnant bulges of the accreted spirals. H79d could be interpreted as the most recent intruder, being the only galaxy with an intact interstellar medium (ISM) and uncertain evidence for tidal perturbation. In addition to stripping activity we find evidence for past accretion events. H79b (NGC6027) shows a strong counter-rotating emission line component interpreted as an accreted dwarf spiral. H79a shows evidence for an infalling component of gas representing feedback or possible cross-fueling by H79d. The biggest challenge to this scenario involves the low gas fraction in the group. If SS formed from normal field spirals then much of the gas is missing. Finally, despite its advanced stage of evolution, we find no evidence for major mergers and infer that SS (and SQ) are telling us that such groups coalesce via slow dissolution
Relationship between nerve fiber layer hemorrhages and outcomes in central retinal vein occlusion
Copyright 2020 The Authors PURPOSE. To evaluate the depth and pattern of retinal hemorrhage in acute central retinal vein occlusion (CRVO) and to correlate these with visual and anatomic outcomes. METHODS. Retinal hemorrhages were evaluated with color fundus photography and fluorescein angiography at baseline and follow-up. Snellen visual acuity (VA), central foveal thickness (CFT), extent of retinal ischemia, and development of neovascularization were analyzed. RESULTS. 108 eyes from 108 patients were evaluated. Mean age was 63.6 ± 16.1 years with a predilection for the right eye (73.1%). Average follow-up was 17.2 ± 19.2 months. Mean VA at baseline was 20/126 and 20/80 at final follow-up. Baseline (P = 0.005) and final VA (P = 0.02) in eyes with perivascular nerve fiber layer (NFL) hemorrhages were significantly worse than in eyes with deep hemorrhages alone. Baseline CFT was greater in the group with perivascular hemorrhages (826 ± 394 Όm) compared to the group with deep hemorrhages alone (455 ± 273 Όm, P \u3c 0.001). The 10 disc areas of retinal ischemia was more common in patients with perivascular (80.0%) and peripapillary (31.3%) versus deep hemorrhages alone (16.1%, P \u3c 0.001). Neovascularization of the iris was more common, although this differrence was not significant, in the groups with peripapillary (14.3%) and perivascular (2.0%) NFL versus deep hemorrhages alone (0.0%). CONCLUSIONS. NFL retinal hemorrhages at baseline correlate with more severe forms of CRVO, with greater macular edema, poorer visual outcomes, and greater risk of ischemia and neovascularization. This may be related to the organization of the retinal capillary plexus. The depth and pattern of distribution of retinal hemorrhages in CRVO may provide an easily identifiable early biomarker of CRVO prognosis
The VIMOS-VLT Deep Survey. The dependence of clustering on galaxy stellar mass at z~1
Aims: We use the VVDS-Deep first-epoch data to measure the dependence of
galaxy clustering on galaxy stellar mass, at z~0.85.
Methods: We measure the projected correlation function wp(rp) for sub-samples
with 0.5<z<1.2 covering different mass ranges between 10^9 and 10^11 Msun. We
quantify in detail the observational selection biases using 40 mock catalogues
built from the Millennium run and semi-analytic models.
Results: Our simulations indicate that serious incompleteness in mass is
present only for log(M/Msun)<9.5. In the mass range log(M/Msun)=[9.0-9.5], the
photometric selection function of the VVDS misses 2/3rd of the galaxies. The
sample is virtually 100% complete above 10^10 Msun. We present the first direct
evidence for a clear dependence of clustering on the galaxy stellar mass at
z~0.85. The clustering length increases from r0 ~ 2.76 h^-1 Mpc for galaxies
with mass M>10^9 Msun to r0 ~ 4.28 h^-1 Mpc for galaxies more massive than
10^10.5 Msun. At the same time, the slope increases from ~ 1.67 to ~ 2.28.
A comparison of the observed wp(rp) to local measurements by the SDSS shows
that the evolution is faster for objects less massive than ~10^10.5 Msun. This
is interpreted as a higher dependence on redshift of the linear bias b_L for
the more massive objects. While for the most massive galaxies b_L decreases
from 1.5+/-0.2 at z~0.85 to 1.33+/-0.03 at z~0.15, the less massive population
maintains a virtually constant value b_L~1.3. This result is in agreement with
a scenario in which more massive galaxies formed at high redshift in the
highest peaks of the density field, while less massive objects form at later
epochs from the more general population of dark-matter halos.Comment: 13 pages, 10 figures, accepted in A&
The VIMOS Public Extragalactic Redshift Survey (VIPERS). Never mind the gaps: comparing techniques to restore homogeneous sky coverage
[Abridged] Non-uniform sampling and gaps in sky coverage are common in galaxy
redshift surveys, but these effects can degrade galaxy counts-in-cells and
density estimates. We carry out a comparison of methods that aim to fill the
gaps to correct for the systematic effects. Our study is motivated by the
analysis of the VIMOS Extragalactic Redshift Survey (VIPERS), a flux-limited
survey (i<22.5) based on one-pass observations with VIMOS, with gaps covering
25% of the surveyed area and a mean sampling rate of 35%. Our findings are
applicable to other surveys with similar observing strategies. We compare 1)
two algorithms based on photometric redshift, that assign redshifts to galaxies
based on the spectroscopic redshifts of the nearest neighbours, 2) two Bayesian
methods, the Wiener filter and the Poisson-Lognormal filter. Using galaxy mock
catalogues we quantify the accuracy of the counts-in-cells measurements on
scales of R=5 and 8 Mpc/h after applying each of these methods. We also study
how they perform to account for spectroscopic redshift error and inhomogeneous
and sparse sampling rate. We find that in VIPERS the errors in counts-in-cells
measurements on R<10 Mpc/h scales are dominated by the sparseness of the
sample. All methods underpredict by 20-35% the counts at high densities. This
systematic bias is of the same order as random errors. No method outperforms
the others. Random and systematic errors decrease for larger cells. We show
that it is possible to separate the lowest and highest densities on scales of 5
Mpc/h at redshifts 0.5<z<1.1, over a large volume such as in VIPERS survey.
This is vital for the characterisation of cosmic variance and rare populations
(e.g, brightest galaxies) in environmental studies at these redshifts.Comment: 17 pages, 13 figures, accepted for publication in A&A (revised
version after minor revision and language editing
Characteristics of self-care interventions for patients with a chronic condition: A scoping review
Background: Self-care is a fundamental element of treatment for patients with a chronic condition and a major focus of many interventions. A large body of research exists describing different types of self-care interventions, but these studies have never been compared across conditions. Examination of heterogeneous interventions could provide insights into effective approaches that should be used in diverse patient populations.
Objectives: To provide a comprehensive and standardized cross-condition overview of interventions to enhance self-care in patients with a chronic condition. Specific aims were to: 1) identify what self-care concepts and behaviors are evaluated in self-care interventions; 2) classify and quantify heterogeneity in mode and type of delivery; 3) quantify the behavior change techniques used to enhance self-care behavior; and 4) assess the dose of self-care interventions delivered.
Design: Scoping review DATA SOURCES: Four electronic databases - PubMed, EMBASE, PsychINFO and CINAHL - were searched from January 2008 through January 2019.
Eligibility criteria for study selection: Randomized controlled trials (RCTs) with concealed allocation to the intervention were included if they compared a behavioral or educational self- care intervention to usual care or another self-care intervention and were conducted in adults. Nine common chronic conditions were included: hypertension, coronary artery disease, arthritis, chronic kidney disease, heart failure, stroke, asthma, chronic obstructive lung disease, and type 2 diabetes mellitus. Diagnoses that are psychiatric (e.g. schizophrenia), acute rather than chronic, or benefitting little from self-care (e.g. dementia) were excluded. Studies had to be reported in English with full-text available.
Results: 9309 citations were considered and 233 studies were included in the final review. Most studies addressed type 2 diabetes mellitus (n = 85; 36%), hypertension (n = 32; 14%) or heart failure (n = 27; 12%). The majority (97%) focused on healthy behaviors like physical activity (70%), dietary intake (59%), and medication management (52%). Major deficits found in self-care interventions included a lack of attention to the psychological consequences of chronic illness, technology and behavior change techniques were rarely used, few studies focused on helping patients manage signs and symptoms, and the interventions were rarely innovative. Research reporting was generally poor.
Conclusions: Major gaps in targeted areas of self-care were identified. Opportunities exist to improve the quality and reporting of future self-care intervention research. Registration: The study was registered in the PROSPERO database (#123,719)
Physical properties of galaxies and their evolution in the VIMOS VLT Deep Survey. II. Extending the mass-metallicity relation to the range z=0.89-1.24
Aims. We present a continuation of our study about the relation between
stellar mass and gas-phase metallicity in the VIMOS VLT Deep Survey (VVDS). In
this work we extend the determination of metallicities up to redshift = 1.24
for a sample of 42 star-forming galaxies with a mean redshift value of 0.99.
Methods. For a selected sample of emission-line galaxies, we use both
diagnostic diagrams and empirical calibrations based on [OII] emission lines
along with the empirical relation between the intensities of the [OIII] and
[NeIII] emission lines and the theoretical ratios between Balmer recombination
emission lines to identify star-forming galaxies and to derive their
metallicities. We derive stellar masses by fitting the whole spectral energy
distribution with a set of stellar population synthesis models. Results. These
new methods allow us to extend the mass-metallicity relation to higher
redshift. We show that the metallicity determinations are consistent with more
established strong-line methods. Taken together this allows us to study the
evolution of the mass-metallicity relation up to z = 1.24 with good control of
systematic uncertainties. We find an evolution with redshift of the average
metallicity of galaxies very similar to those reported in the literature: for a
given stellar mass, galaxies at z = 1 have, on average, a metallicity = 0.3 dex
lower than galaxies in the local universe. However we do not see any
significant metallicity evolution between redshifts z = 0.7 (Paper I) and z =
1.0 (this paper). We find also the same flattening of the mass-metallicity
relation for the most massive galaxies as reported in Paper I at lower
redshifts, but again no apparent evolution of the slope is seen between z = 0.7
and z = 1.0.Comment: 9 pages and 8 figures. In press in Astronomy & Astrophysic
The VIMOS VLT Deep Survey: the group catalogue
[Abridged] We present a homogeneous and complete catalogue of optical groups
identified in the purely flux limited (17.5<=I<=24.0) VIMOS-VLT Deep Survey
(VVDS). We use mock catalogues extracted from the MILLENNIUM simulation, to
correct for potential systematics that might affect the overall distribution as
well as the individual properties of the identified systems. Simulated samples
allow us to forecast the number and properties of groups that can be
potentially found in a survey with VVDS-like selection functions. We use them
to correct for the expected incompleteness and also to asses how well galaxy
redshifts trace the line-of-sight velocity dispersion of the underlying mass
overdensity. In particular, we train on these mock catalogues the adopted
group-finding technique (the Voronoi-Delaunay Method, VDM). The goal is to
fine-tune its free parameters, recover in a robust and unbiased way the
redshift and velocity dispersion distributions of groups and maximize the level
of completeness (C) and purity (P) of the group catalogue. We identify 318 VVDS
groups with at least 2 members within 0.2<=z<=1.0, among which 144 (/30) with
at least 3 (/5) members. The sample has globally C=60% and P=50%. Nearly 45% of
the groups with at least 3 members are still recovered if we run the algorithm
with a parameter set which maximizes P (75%). We exploit the group sample to
study the redshift evolution of the fraction f_b of blue galaxies (U-B<=1)
within 0.2<=z<=1. We find that f_b is significantly lower in groups than in the
whole ensemble of galaxies irrespectively of their environment. These
quantities increase with redshift, with f_b in groups showing a marginally
significant steeper increase. We also confirm that, at any explored redshift,
f_b decreases for increasing group richness, and we extend towards fainter
luminosities the magnitude range over which this result holds.Comment: Submitted to A&A, revised version after referee comments, Table 5
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The VIMOS Public Extragalactic Redshift Survey (VIPERS). Exploring the dependence of the three-point correlation function on stellar mass and luminosity at 0.5<z<1.1
The three-point correlation function (3PCF) is a powerful probe to
investigate the clustering of matter in the Universe in a complementary way
with respect to lower-order statistics, providing additional information with
respect to the two-point correlation function and allowing us to shed light on
biasing, nonlinear processes, and deviations from Gaussian statistics. In this
paper, we analyse the first data release of the VIMOS Public Extragalactic
Redshift Survey (VIPERS), determining the dependence of the three-point
correlation function on luminosity and stellar mass at . We
exploit the VIPERS Public Data Release 1, consisting of more than 50,000
galaxies with B-band magnitudes in the range and stellar masses in the range
. We measure both the
connected 3PCF and the reduced 3PCF in redshift space, probing different
configurations and scales, in the range [Mpc/h]. We find a
significant dependence of the reduced 3PCF on scales and triangle shapes, with
stronger anisotropy at larger scales ( Mpc/h) and an almost flat trend
at smaller scales, Mpc/h. Massive and luminous galaxies present a
larger connected 3PCF, while the reduced 3PCF is remarkably insensitive to
magnitude and stellar masses in the range we explored. These trends, already
observed at low redshifts, are confirmed for the first time to be still valid
up to , providing support to the hierarchical scenario for which massive
and bright systems are expected to be more clustered. The possibility of using
the measured 3PCF to provide independent constraints on the linear galaxy bias
has also been explored, showing promising results in agreement with other
probes.Comment: 12 pages, 11 figures, 2 tables, accepted for publication in A&
The Vimos VLT Deep Survey: Stellar mass segregation and large-scale galaxy environment in the redshift range 0.2<z<1.4
Hierarchical models of galaxy formation predict that the properties of a dark
matter halo depend on the large-scale environment surrounding the halo. As a
result of this correlation, we expect massive haloes to be present in larger
number in overdense regions than in underdense ones. Given that a correlation
exists between a galaxy stellar mass and the hosting dark matter halo mass, the
segregation in dark matter halo mass should then result in a segregation in the
distribution of stellar mass in the galaxy population. In this work we study
the distribution of galaxy stellar mass and rest-frame optical color as a
function of the large-scale galaxy distribution using the VLT VIMOS Deep Survey
sample, in order to verify the presence of segregation in the properties of the
galaxy population. We use the VVDS redshift measurements and multi-band
photometric data to derive estimates of the stellar mass, rest-frame optical
color, and of the large-scale galaxy density, on a scale of approximately 8
Mpc, for a sample of 5619 galaxies in the redshift range 0.2<z<1.4. We observe
a significant mass and optical color segregation over the whole redshift
interval covered by our sample, such that the median value of the mass
distribution is larger and the rest-frame optical color is redder in regions of
high galaxy density. The amplitude of the mass segregation changes little with
redshift, at least in the high stellar mass regime that we can uniformely
sample over the 0.2<z<1.4 redshift interval. The color segregation, instead,
decreases significantly for z>0.7. However, when we consider only galaxies in
narrow bins of stellar mass, in order to exclude the effects of the stellar
mass segregation on the galaxy properties, we do not observe any more any
significant color segregation.Comment: 7 pages, 5 figures; accepted for publication in Astronomy and
Astrophysic
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