257 research outputs found
Bulge plus disc and S\'ersic decomposition catalogues for 16,908 galaxies in the SDSS Stripe 82 co-adds: A detailed study of the structural measurements
Quantitative characterization of galaxy morphology is vital in enabling
comparison of observations to predictions from galaxy formation theory.
However, without significant overlap between the observational footprints of
deep and shallow galaxy surveys, the extent to which structural measurements
for large galaxy samples are robust to image quality (e.g., depth, spatial
resolution) cannot be established. Deep images from the Sloan Digital Sky
Survey (SDSS) Stripe 82 co-adds provide a unique solution to this problem -
offering magnitudes improvement in depth with respect to SDSS Legacy
images. Having similar spatial resolution to Legacy, the co-adds make it
possible to examine the sensitivity of parametric morphologies to depth alone.
Using the Gim2D surface-brightness decomposition software, we provide public
morphology catalogs for 16,908 galaxies in the Stripe 82 co-adds. Our
methods and selection are completely consistent with the Simard et al. (2011)
and Mendel et al. (2014) photometric decompositions. We rigorously compare
measurements in the deep and shallow images. We find no systematics in total
magnitudes and sizes except for faint galaxies in the -band and the
brightest galaxies in each band. However, characterization of bulge-to-total
fractions is significantly improved in the deep images. Furthermore, statistics
used to determine whether single-S\'ersic or two-component (e.g., bulge+disc)
models are required become more bimodal in the deep images. Lastly, we show
that asymmetries are enhanced in the deep images and that the enhancement is
positively correlated with the asymmetries measured in Legacy images.Comment: 27 pages, 14 figures. MNRAS accepted. Our catalogs are available in
TXT and SQL formats at
http://orca.phys.uvic.ca/~cbottrel/share/Stripe82/Catalogs
Stellar mass functions of galaxies, disks and spheroids at z~0.1
We present the stellar mass functions (SMF) and mass densities of galaxies,
and their spheroid and disk components in the local (z~0.1) universe over the
range 8.9 <= log(M/M_solar) <= 12 from spheroid+disk decompositions and
corresponding stellar masses of a sample of over 600,000 galaxies in the
SDSS-DR7 spectroscopic sample. The galaxy SMF is well represented by a single
Schechter function (M* = 11.116+/-0.011, alpha = -1.145+/-0.008), though with a
hint of a steeper faint end slope. The corresponding stellar mass densities are
(2.670+/-0.110), (1.687+/-0.063) and (0.910+/-0.029)x10^8 M_solar Mpc^-3 for
galaxies, spheroids and disks respectively. We identify a crossover stellar
mass of log(M/M_solar) = 10.3+/-0.030 at which the spheroid and disk SMFs are
equal. Relative contributions of four distinct spheroid/disk dominated
sub-populations to the overall galaxy SMF are also presented. The mean
disk-to-spheroid stellar mass ratio shows a five fold disk dominance at the low
mass end, decreasing monotonically with a corresponding increase in the
spheroidal fraction till the two are equal at a galaxy stellar mass,
log(M/M_solar)=10.479+/-0.013, the dominance of spheroids then grows with
increasing stellar mass. The relative numbers of composite disk and spheroid
dominated galaxies show peaks in their distributions, perhaps indicative of a
preferred galaxy mass. Our characterization of the low redshift galaxy
population provides stringent constraints for numerical simulations to
reproduce.Comment: 30 pages, 18 figures, 5 tables (2 online), Accepted for publication
in MNRA
The signature of dissipation in the mass-size relation: are bulges simply spheroids wrapped in a disc?
The relation between the stellar mass and size of a galaxy's structural
subcomponents, such as discs and spheroids, is a powerful way to understand the
processes involved in their formation. Using very large catalogues of
photometric bulge+disc structural decompositions and stellar masses from the
Sloan Digital Sky Survey Data Release Seven, we carefully define two large
subsamples of spheroids in a quantitative manner such that both samples share
similar characteristics with one important exception: the 'bulges' are embedded
in a disc and the 'pure spheroids' are galaxies with a single structural
component. Our bulge and pure spheroid subsample sizes are 76,012 and 171,243
respectively. Above a stellar mass of ~ M, the mass-size
relations of both subsamples are parallel to one another and are close to lines
of constant surface mass density. However, the relations are offset by a factor
of 1.4, which may be explained by the dominance of dissipation in their
formation processes. Whereas the size-mass relation of bulges in discs is
consistent with gas-rich mergers, pure spheroids appear to have been formed via
a combination of 'dry' and 'wet' mergers.Comment: Accepted for publication in MNRAS, 6 pages, 3 figure
Bulge mass is king: The dominant role of the bulge in determining the fraction of passive galaxies in the Sloan Digital Sky Survey
We investigate the origin of galaxy bimodality by quantifying the relative
role of intrinsic and environmental drivers to the cessation (or `quenching')
of star formation in over half a million local Sloan Digital Sky Survey (SDSS)
galaxies. Our sample contains a wide variety of galaxies at z=0.02-0.2, with
stellar masses of 8 < log(M*/M_sun) < 12, spanning the entire morphological
range from pure disks to spheroids, and over four orders of magnitude in local
galaxy density and halo mass. We utilise published star formation rates and add
to this recent GIM2D photometric and stellar mass bulge + disk decompositions
from our group. We find that the passive fraction of galaxies increases steeply
with stellar mass, halo mass, and bulge mass, with a less steep dependence on
local galaxy density and bulge-to-total stellar mass ratio (B/T). At fixed
internal properties, we find that central and satellite galaxies have different
passive fraction relationships. For centrals, we conclude that there is less
variation in the passive fraction at a fixed bulge mass, than for any other
variable, including total stellar mass, halo mass, and B/T. This implies that
the quenching mechanism must be most tightly coupled to the bulge. We argue
that radio-mode AGN feedback offers the most plausible explanation of the
observed trends.Comment: Accepted to MNRAS. 32 pages, 27 figures. [This version is virtually
identical to v1
Transcatheter Tricuspid Valve Intervention: Current Perspective
Tricuspid regurgitation (TR) adversely impacts both quality of life and long-term survival, which generates interest in therapeutic approaches to mitigate these effects. Historically, therapeutic options for TR were limited to surgical approaches, which are often complicated by significant morbidity and mortality in elderly patients with multiple comorbidities. This gap in therapeutic options led to the rapid evolution of transcatheter tricuspid valve intervention (TTVI), with a wide variety of approaches pursued and early results suggesting that TTVI improves clinical outcomes. Numerous strategies, including edge-to-edge repair, annular reduction, spacers, caval valve implantation, and transcatheter tricuspid valve replacement form the basis of TTVI today. In this review, the authors discuss the current state of each approach
Evidence for a non-universal stellar initial mass function in low-redshift high-density early-type galaxies
We determine an absolute calibration of stellar mass-to-light ratios for the
densest \simeq 3% of early-type galaxies in the local universe (redshift
z\simeq 0.08) from SDSS DR7. This sample of \sim 4000 galaxies has, assuming a
Chabrier IMF, effective stellar surface densities, Sigma_e > 2500 M_sun/pc^2,
stellar population synthesis (SPS) stellar masses log_10(M_sps/M_sun)<10.8, and
aperture velocity dispersions of sigma_ap=168^{+37}_{-34} km/s (68% range). In
contrast to typical early-type galaxies, we show that these dense early-type
galaxies follow the virial fundamental plane, which suggests that
mass-follows-light. With the additional assumption that any dark matter does
not follow the light, the dynamical masses of dense galaxies provide a direct
measurement of stellar masses. Our dynamical masses (M_dyn), obtained from the
spherical Jeans equations, are only weakly sensitive to the choice of
anisotropy (\beta) due to the relatively large aperture of the SDSS fiber for
these galaxies: R_ap \simeq 1.5 R_e. Assuming isotropic orbits (\beta=0) we
find a median log_{10} (M_dyn/M_sps) = 0.233 \pm 0.003, consistent with a
Salpeter IMF, while more bottom heavy IMFs and standard Milky-Way IMFs are
strongly disfavored. Our results are consistent with, but do not require, a
dependence of the IMF on dynamical mass or velocity dispersion. We find
evidence for a color dependence to the IMF such that redder galaxies have
heavier IMFs with M_dyn/M_sps \propto (g-r)^{1.13\pm0.09}. This may reflect a
more fundamental dependence of the IMF on the age or metallicity of a stellar
population, or the density at which the stars formed.Comment: 5 pages, 6 figures, accepted to MNRAS Letters, minor changes to
previous versio
Spontaneous coronary artery dissection in cardiac sarcoidosis
Cardiac sarcoidosis (CS) is increasingly recognized as a cause of diverse cardiac manifestations. Spontaneous coronary artery dissection (SCAD) has emerged as an important cause of acute coronary syndrome especially among young females. The prevalence of sarcoidosis in the causal spectrum of SCAD has not been described before but sarcoidosis is cited as a potential yet rare cause of SCAD. We aimed to examine the frequency and characteristics of SCAD in CS. Searching two prospective CS registries with 481 CS patients, we found only one case of manifest SCAD. She is a 61-year-old female previously diagnosed with endomyocardial biopsy confirmed CS. She presented with chest pain and elevated troponin. Coronary angiogram revealed two-vessel SCAD. Fluorodeoxyglucose positron emission tomography scan showed likely reactivation of CS. The patient was treated with dual antiplatelet therapy and immunosuppression. Repeat angiogram showed complete resolution of the coronary lesions.Peer reviewe
What shapes a galaxy? - Unraveling the role of mass, environment and star formation in forming galactic structure
We investigate the dependence of galaxy structure on a variety of galactic
and environmental parameters for ~500,000 galaxies at z<0.2, taken from the
Sloan Digital Sky Survey data release 7 (SDSS-DR7). We utilise bulge-to-total
stellar mass ratio, (B/T)_*, as the primary indicator of galactic structure,
which circumvents issues of morphological dependence on waveband. We rank
galaxy and environmental parameters in terms of how predictive they are of
galaxy structure, using an artificial neural network approach. We find that
distance from the star forming main sequence (Delta_SFR), followed by stellar
mass (M_*), are the most closely connected parameters to (B/T)_*, and are
significantly more predictive of galaxy structure than global star formation
rate (SFR), or any environmental metric considered (for both central and
satellite galaxies). Additionally, we make a detailed comparison to the
Illustris hydrodynamical simulation and the LGalaxies semi-analytic model. In
both simulations, we find a significant lack of bulge-dominated galaxies at a
fixed stellar mass, compared to the SDSS. This result highlights a potentially
serious problem in contemporary models of galaxy evolution.Comment: Accepted to MNRAS. 31 pages, 15 figure
Compact groups in theory and practice -- IV. The connection to large-scale structure
We investigate the properties of photometrically-selected compact groups
(CGs) in the Sloan Digital Sky Survey. In this paper, the fourth in a series,
we focus on understanding the characteristics of our observed CG sample with
particular attention paid to quantifying and removing contamination from
projected foreground or background galaxies. Based on a simple comparison of
pairwise redshift likelihoods, we find that approximately half of compact
groups in the parent sample contain one or more projected (interloping)
members; our final clean sample contains 4566 galaxies in 1086 compact groups.
We show that half of the remaining CGs are associated with rich groups (or
clusters), i.e. they are embedded sub-structure. The other half have spatial
distributions and number-density profiles consistent with the interpretation
that they are either independently distributed structures within the field
(i.e. they are isolated) or associated with relatively poor structures.
Comparisons of late-type and red-sequence fractions in radial annuli show that
galaxies around apparently isolated compact groups resemble the field
population by 300 to 500 kpc from the group centre. In contrast, the galaxy
population surrounding embedded compact groups appears to remain distinct from
the field out beyond 1 to 2 Mpc, consistent with results for rich groups. We
take this as additional evidence that the observed distinction between compact
groups, i.e. isolated vs. embedded, is a separation between different host
environments.Comment: 15 pages, 11 figures. Accepted for publication in MNRA
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