38 research outputs found
Measurement of β-hydroxybutyrate in cats with nonketotic diabetes mellitus, diabetic ketosis, and diabetic ketoacidosis
Diabetic ketoacidosis (DKA) is a life-threatening complication of diabetes
mellitus (DM). The standard method of detection of ketone bodies is the
dipstick method, which detects semiquantitatively acetoacetate, but not
β-hydroxybutyrate (β-HB). The objectives of the current study were to assess
the diagnostic utility of β-HB to diagnose diabetic ketosis (DK) and DKA in
cats and to establish a cut-off value for the diagnosis of DKA. Sixty-two cats
were included in the study. Eleven cats were healthy (group 1); in the
remainder of cats (51), a diagnosis of DM was based on hyperglycemia,
glucosuria, and increased fructosamine concentrations. Nineteen of 51 cats
suffered from nonketotic diabetes mellitus (group 2). In 11 cats, plasma
ketone bodies were detected with the dipstick method (diabetic ketosis, group
3). In 21 cats, plasma ketone bodies and metabolic acidosis were present (DKA,
group 4). Plasma β-HB was measured in all cats by an enzymatic method
(spectrophotometry). A cut-off value for the diagnosis of DKA was calculated
based on the receiver operating characteristic curve. In healthy cats, the
β-HB concentration ranged from 0 to 0.1 mmol/l; in cats of group 2, from 0 to
0.9 mmol/l (median: 0.1 mmol/l); in cats of group 3, from 0.6 to 6.8 mmol/l
(median: 1.7 mmol/l); and in cats of group 4, from 3.8 to 12.2 mmol/l (median:
7.9 mmol/l). A cut-off value of 2.4 mmol/l revealed 100% sensitivity and 87%
specificity to diagnose DKA. Beta-hydroxybutyrate is a useful parameter for
the diagnosis of diabetic ketosis and DKA in cats
On the Formation of Multiple Stellar Populations in Globular Clusters
Nearly all globular clusters (GCs) studied to date show evidence for multiple
stellar populations, in stark contrast to the conventional view that GCs are a
mono-metallic, coeval population of stars. Building on earlier work, we propose
a simple physical model for the early evolution (several 10^8 yr) of GCs. We
consider the effects of stellar mass-loss, type II and prompt type Ia
supernovae, ram pressure, and accretion from the ambient ISM on the development
of a young GC's own gas reservoir. In our model, type II SNe from a first
generation of star formation clears the GC of its initial gas reservoir. Over
the next several 10^8 yr, mass lost from AGB stars and matter accreted from the
ambient ISM collect at the center of the GC. This material must remain quite
cool (T~10^2K), but does not catastrophically cool on a crossing time because
of the high Lyman-Werner flux density in young GCs. The collection of gas
within the GC must compete with ram pressure from the ambient ISM. After
several 10^8 yr, the Lyman-Werner photon flux density drops by more than three
orders of magnitude, allowing molecular hydrogen and then stars to form. After
this second generation of star formation, type II SNe from the second
generation and then prompt type Ia SNe associated with the first generation
maintain a gas-free GC, thereby ending the cycle of star formation events. Our
model makes clear predictions for the presence or absence of multiple stellar
populations within GCs as a function of GC mass and formation environment.
Analyzing intermediate-age LMC clusters, we find evidence for a mass threshold
of ~10^4 Msun below which LMC clusters appear to be truly coeval. This
threshold mass is consistent with our predictions for the mass at which ram
pressure is capable of clearing gas from clusters in the LMC at the present
epoch. (ABRIDGED)Comment: 13 pages, 5 figures, ApJ in pres
Deep CO(1–0) Observations of z = 1.62 Cluster Galaxies with Substantial Molecular Gas Reservoirs and Normal Star Formation Efficiencies
We present an extremely deep CO(1–0) observation of a confirmed z = 1.62 galaxy cluster. We detect two spectroscopically confirmed cluster members in CO(1–0) with signal-to-noise ratio . Both galaxies have log(/) > 11 and are gas rich, with /(+) ~ 0.17–0.45. One of these galaxies lies on the star formation rate (SFR)– sequence, while the other lies an order of magnitude below. We compare the cluster galaxies to other SFR-selected galaxies with CO measurements and find that they have CO luminosities consistent with expectations given their infrared luminosities. We also find that they have gas fractions and star formation efficiencies (SFE) comparable to what is expected from published field galaxy scaling relations. The galaxies are compact in their stellar light distribution, at the extreme end for all high-redshift star-forming galaxies. However, their SFE is consistent with other field galaxies at comparable compactness. This is similar to two other sources selected in a blind CO survey of the HDF-N. Despite living in a highly quenched protocluster core, the molecular gas properties of these two galaxies, one of which may be in the process of quenching, appear entirely consistent with field scaling relations between the molecular gas content, stellar mass, star formation rate, and redshift. We speculate that these cluster galaxies cannot have any further substantive gas accretion if they are to become members of the dominant passive population in clusters
Automated Morphological Classification of SDSS Red Sequence Galaxies
(abridged) In the last decade, the advent of enormous galaxy surveys has
motivated the development of automated morphological classification schemes to
deal with large data volumes. Existing automated schemes can successfully
distinguish between early and late type galaxies and identify merger
candidates, but are inadequate for studying detailed morphologies of red
sequence galaxies. To fill this need, we present a new automated classification
scheme that focuses on making finer distinctions between early types roughly
corresponding to Hubble types E, S0, and Sa. We visually classify a sample of
984 non-starforming SDSS galaxies with apparent sizes >14". We then develop an
automated method to closely reproduce the visual classifications, which both
provides a check on the visual results and makes it possible to extend
morphological analysis to much larger samples. We visually classify the
galaxies into three bulge classes (BC) by the shape of the light profile in the
outer regions: discs have sharp edges and bulges do not, while some galaxies
are intermediate. We separately identify galaxies with features: spiral arms,
bars, clumps, rings, and dust. We find general agreement between BC and the
bulge fraction B/T measured by the galaxy modeling package GIM2D, but many
visual discs have B/T>0.5. Three additional automated parameters -- smoothness,
axis ratio, and concentration -- can identify many of these high-B/T discs to
yield automated classifications that agree ~70% with the visual classifications
(>90% within one BC). Both methods are used to study the bulge vs. disc
frequency as a function of four measures of galaxy 'size': luminosity, stellar
mass, velocity dispersion, and radius. All size indicators show a fall in disc
fraction and a rise in bulge fraction among larger galaxies.Comment: 24 pages, 20 figures, MNRAS accepte
Evolution in the Disks and Bulges of Group Galaxies since z=0.4
We present quantitative morphology measurements of a sample of optically
selected group galaxies at 0.3 < z < 0.55 using the Hubble Space Telescope
(HST) Advanced Camera for Surveys (ACS) and the GIM2D surface
brightness--fitting software package. The group sample is derived from the
Canadian Network for Observational Cosmology Field Redshift survey (CNOC2) and
follow-up Magellan spectroscopy. We compare these measurements to a similarly
selected group sample from the Millennium Galaxy Catalogue (MGC) at 0.05 < z <
0.12. We find that, at both epochs, the group and field fractional bulge
luminosity (B/T) distributions differ significantly, with the dominant
difference being a deficit of disk--dominated (B/T < 0.2) galaxies in the group
samples. At fixed luminosity, z=0.4 groups have ~ 5.5 +/- 2 % fewer
disk--dominated galaxies than the field, while by z=0.1 this difference has
increased to ~ 19 +/- 6 %. Despite the morphological evolution we see no
evidence that the group environment is actively perturbing or otherwise
affecting the entire existing disk population. At both redshifts, the disks of
group galaxies have similar scaling relations and show similar median
asymmetries as the disks of field galaxies. We do find evidence that the
fraction of highly asymmetric, bulge--dominated galaxies is 6 +/- 3 % higher in
groups than in the field, suggesting there may be enhanced merging in group
environments. We replicate our group samples at z=0.4 and z=0 using the
semi-analytic galaxy catalogues of Bower et al (2006). This model accurately
reproduces the B/T distributions of the group and field at z=0.1. However, the
model does not reproduce our finding that the deficit of disks in groups has
increased significantly since z=0.4.Comment: Accepted for publication in MNRAS. 20 pages, 17 figure
Extending the M_(bh)-sigma diagram with dense nuclear star clusters
Abridged: Four new nuclear star cluster masses, M_nc, plus seven upper
limits, are provided for galaxies with previously determined black hole masses,
M_bh. Together with a sample of 64 galaxies with direct M_bh measurements, 13
of which additionally now have M_nc measurements rather than only upper limits,
plus an additional 29 dwarf galaxies with available M_nc measurements and
velocity dispersions sigma, an (M_bh + M_nc)-sigma diagram is constructed.
Given that major dry galaxy merger events preserve the M_bh/L ratio, and given
that L ~ sigma^5 for luminous galaxies, it is first noted that the observation
M_bh ~ sigma^5 is consistent with expectations. For the fainter elliptical
galaxies it is known that L ~ sigma^2, and assuming a constant M_nc/L ratio
(Ferrarese et al.), the expectation that M_nc ~ sigma^2 is in broad agreement
with our new observational result that M_nc ~ sigma^{1.57\pm0.24}. This
exponent is however in contrast to the value of ~4 which has been reported
previously and interpreted in terms of a regulating feedback mechanism from
stellar winds.Comment: 6 pages, 2 figures. Submitted 08/08/2011 to MNRAS, first referee
report received 19/01/2012, accepted 10/02/201
The Shapes of BCGs and normal Ellipticals in Nearby Clusters
We compare the apparent axial ratio distributions of Brightest Cluster
Galaxies (BCGs) and normal ellipticals (Es) in our sample of 75 galaxy clusters
from the WINGS survey. Most BCGs in our clusters (69%) are classified as cD
galaxies. The sample of cDs has been completed by 14 additional cDs (non-BCGs)
we found in our clusters. We find that: (i) Es have triaxial shape, the
triaxiality sharing almost evenly the intrinsic axial ratios parameter space,
with a weak preference for prolateness; (ii) the BCGs have triaxial shape as
well. However, their tendence towards prolateness is much stronger than in the
case of Es. Such a strong prolateness appears entirely due to the sizeable
(dominant) component of cDs inside the WINGS sample of BCGs. In fact, while the
'normal'(non-cD) BCGs do not differ from Es, as far as the shape distribution
is concerned, the axial ratio distribution of BCG_cD galaxies is found to
support quite prolate shapes; (iii) our result turns out to be strongly at
variance with the only similar, previous analysis by Ryden et al.(1993)(RLP93),
where BCGs and Es were found to share the same axial ratio distribution; (iv)
our data suggest that the above discrepancy is mainly caused by the different
criteria that RLP93 and ourselves use to select the cluster samples, coupled
with a preference of cDs to reside in powerful X-ray emitting clusters; (v) the
GIF2 N-body results suggest that the prolateness of the BCGs (in particular the
cDs) could reflect the shape of the associated dark matter halos.Comment: 18 pages, 9 figures, 2 tables. Accepted for publication in MNRA
Are luminous radio-loud active galactic nuclei triggered by galaxy interactions?
We present the results of a comparison between the optical morphologies of a
complete sample of 46 southern 2Jy radio galaxies at intermediate redshifts
(0.05<z<0.7) and those of two control samples of quiescent early-type galaxies:
55 ellipticals at redshifts z<0.01 from the Observations of Bright Ellipticals
at Yale (OBEY) survey, and 107 early-type galaxies at redshifts 0.2<z<0.7 in
the Extended Groth Strip (EGS). Based on these comparisons, we discuss the role
of galaxy interactions in the triggering of powerful radio galaxies (PRGs). We
find that a significant fraction of quiescent ellipticals at low and
intermediate redshifts show evidence for disturbed morphologies at relatively
high surface brightness levels, which are likely the result of past or on-going
galaxy interactions. However, the morphological features detected in the galaxy
hosts of the PRGs (e.g. tidal tails, shells, bridges, etc.) are up to 2
magnitudes brighter than those present in their quiescent counterparts. Indeed,
if we consider the same surface brightness limits, the fraction of disturbed
morphologies is considerably smaller in the quiescent population (53% at z<0.2
and 48% at 0.2<z<0.7) than in the PRGs (93% at z<0.2 and 95% at 0.2<z<0.7
considering strong-line radio galaxies only). This supports a scenario in which
PRGs represent a fleeting active phase of a subset of the elliptical galaxies
that have recently undergone mergers/interactions. However, we demonstrate that
only a small proportion (<20%) of disturbed early-type galaxies are capable of
hosting powerful radio sources.Comment: 20 pages, 7 figures, accepted for publication in MNRA