1,915 research outputs found
Deep Herschel view of obscured star formation in the Bullet cluster
We use deep, five band (100â500 ÎŒm) data from the Herschel Lensing Survey (HLS) to fully constrain the obscured star formation rate, SFR_(FIR), of galaxies in the Bullet cluster (z = 0.296), and a smaller background system (z = 0.35) in the same field. Herschel detects 23 Bullet cluster members with a total SFRFIR = 144±14 M_â yr^(-1). On average, the background system contains brighter far-infrared (FIR) galaxies, with ~50% higher SFRFIR (21 galaxies; 207 ± 9 M_â yr^(-1)). SFRs extrapolated from 24 ÎŒm flux via recent templates (SFR_(24 ”m)) agree well with SFRFIR for ~60% of the cluster galaxies. In the remaining ~40%, SFR24 ”m underestimates SFR_(FIR) due to a significant excess in observed S_(100)/S_(24) (rest frame S_(75)/S_(18)) compared to templates of the same FIR luminosity
Accretion-Inhibited Star Formation in the Warm Molecular Disk of the Green-valley Elliptical Galaxy NGC 3226
We present archival Spitzer photometry and spectroscopy, and Herschel
photometry, of the peculiar "Green Valley" elliptical galaxy NGC~3226. The
galaxy, which contains a low-luminosity AGN, forms a pair with NGC~3227, and is
shown to lie in a complex web of stellar and HI filaments. Imaging at 8 and
16m reveals a curved plume structure 3 kpc in extent, embedded within the
core of the galaxy, and coincident with the termination of a 30 kpc-long HI
tail. In-situ star formation associated with the IR plume is identified from
narrow-band HST imaging. The end of the IR-plume coincides with a warm
molecular hydrogen disk and dusty ring, containing 0.7-1.1 10
M detected within the central kpc. Sensitive upper limits to the
detection of cold molecular gas may indicate that a large fraction of the H
is in a warm state. Photometry, derived from the UV to the far-IR, shows
evidence for a low star formation rate of 0.04 M yr
averaged over the last 100 Myrs. A mid-IR component to the Spectral Energy
Distribution (SED) contributes 20 of the IR luminosity of the galaxy,
and is consistent with emission associated with the AGN. The current measured
star formation rate is insufficient to explain NGC3226's global UV-optical
"green" colors via the resurgence of star formation in a "red and dead" galaxy.
This form of "cold accretion" from a tidal stream would appear to be an
inefficient way to rejuvenate early-type galaxies, and may actually inhibit
star formation.Comment: Accepted for Publication ApJ Oct 201
IRAC Observations of M81
IRAC images of M81 show three distinct morphological constituents: a smooth
distribution of evolved stars with bulge, disk, and spiral arm components; a
clumpy distribution of dust emission tracing the spiral arms; and a pointlike
nuclear source. The bulge stellar colors are consistent with M-type giants, and
the disk colors are consistent with a slightly younger population. The dust
emission generally follows the blue and ultraviolet emission, but there are
large areas that have dust emission without ultraviolet and smaller areas with
ultraviolet but little dust emission. The former are presumably caused by
extinction, and the latter may be due to cavities in the gas and dust created
by supernova explosions. The nucleus appears fainter at 8 um than expected from
ground-based 10 um observations made four years ago.Comment: ApJS in press (Spitzer special issue); 15 pages, 3 figures. Changes:
unused references removed, numbers and labels in Table 1 change
Osteoarthritis, cerebrovascular dysfunction and the common denominator of inflammation: a narrative review
© 2018 The Author(s) Objective: Population-based cohort studies suggest an association between osteoarthritis (OA) and cerebrovascular disease, yet the mechanisms underlying vascular comorbidities in OA remain unclear. The purpose of this narrative review is to discuss the literature examining inflammation in OA with a focus on physiological mechanisms, and whether overlapping mechanisms exist in cerebrovascular dysfunction. Method: A literature search was conducted in PubMed using combinations of search terms: osteoarthritis, cerebrovascular (disease/dysfunction/risk), cardiovascular (disease/dysfunction/risk), aging/ageing, inflammation, inflammatory mediators, cytokine, c-reactive protein, interleukin, advanced glycation end-products, metabolic syndrome, reactive oxidative species, cognitive impairment, (vascular-related) dementia, small cerebral vessel disease, endothelial function, bloodâbrain barrier, gender/sex, hypertension, peripheral vascular health, and physical activity. Reference lists of identified articles were also researched manually. Results: Overlapping inflammatory factors that may contribute to onset and progression of both OA and cerebrovascular dysfunction are presented. We describe oxidative mechanisms involving pro-inflammatory cytokines and oxidative species, advanced glycation end-products, sex hormones, microvascular dysfunction and osteoprotegerin, and their specific roles in potentially contributing to OA and cerebrovascular dysfunction. Conclusion: Synthesis of the current literature suggests future investigations may benefit from directly testing cerebrovascular hemodynamics and cognitive function in individuals with or at risk of OA to elucidate common physiological mechanisms
Remote sensing, geographical information system and spatial analysis for schistosomiasis epidemiology and ecology in Africa
Beginning in 1970, the potential of remote sensing (RS) techniques, coupled with geographical information systems (GIS), to improve our understanding of the epidemiology and control of schistosomiasis in Africa, has steadily grown. In our current review, working definitions of RS, GIS and spatial analysis are given, and applications made to date with RS and GIS for the epidemiology and ecology of schistosomiasis in Africa are summarised. Progress has been made in mapping the prevalence of infection in humans and the distribution of intermediate host snails. More recently, Bayesian geostatistical modelling approaches have been utilized for predicting the prevalence and intensity of infection at different scales. However, a number of challenges remain; hence new research is needed to overcome these limitations. First, greater spatial and temporal resolution seems important to improve risk mapping and understanding of transmission dynamics at the local scale. Second, more realistic risk profiling can be achieved by taking into account information on people's socio-economic status; furthermore, future efforts should incorporate data on domestic access to clean water and adequate sanitation, as well as behavioural and educational issues. Third, high-quality data on intermediate host snail distribution should facilitate validation of infection risk maps and modelling transmission dynamics. Finally, more emphasis should be placed on risk mapping and prediction of multiple species parasitic infections in an effort to integrate disease risk mapping and to enhance the cost-effectiveness of their contro
The Spitzer Spirals, Bridges, and Tails Interacting Galaxy Survey: Interaction-Induced Star Formation in the Mid-Infrared
We present Spitzer mid-infrared imaging of a sample of 35 tidally-distorted pre-merger interacting galaxy pairs selected from the Arp Atlas. We compare their global mid-infrared properties with those of normal galaxies from the SINGS Spitzer Legacy survey, and separate the disk emission from that of the tidal features. The [8.0 micron] - [24 micron], [3.6 micron] - [24 micron], and [5.8 micron] - [8.0 micron] colors of these optically-selected interacting galaxies are redder on average than those of spirals, implying enhancements to the mass-normalized star formation rates (SFRs) of a factor of ~2. Furthermore, the 24 micron emission in the Arp galaxies is more centrally concentrated than that in the spirals, suggesting that gas is being concentrated into the inner regions and fueling central star formation. No significant differences can be discerned in the shorter wavelength Spitzer colors of the Arp galaxies compared to the spirals, thus these quantities are less sensitive to star formation enhancements. No strong trend of Spitzer color with pair separation is visible in our sample; this may be because our sample was selected to be tidally disturbed. The tidal features contribute <10% of the total Spitzer fluxes on average. The SFRs implied for the Arp galaxies by the Spitzer 24 micron luminosities are relatively modest, ~1 M(sun)/yr on average
Spatially Resolved Spitzer-IRS Spectroscopy of the Central Region of M82
We present high spatial resolution (~ 35 parsec) 5-38 um spectra of the
central region of M82, taken with the Spitzer Infrared Spectrograph. From these
spectra we determined the fluxes and equivalent widths of key diagnostic
features, such as the [NeII]12.8um, [NeIII]15.5um, and H_2 S(1)17.03um lines,
and the broad mid-IR polycyclic aromatic hydrocarbon (PAH) emission features in
six representative regions and analysed the spatial distribution of these lines
and their ratios across the central region. We find a good correlation of the
dust extinction with the CO 1-0 emission. The PAH emission follows closely the
ionization structure along the galactic disk. The observed variations of the
diagnostic PAH ratios across M82 can be explained by extinction effects, within
systematic uncertainties. The 16-18um PAH complex is very prominent, and its
equivalent width is enhanced outwards from the galactic plane. We interpret
this as a consequence of the variation of the UV radiation field. The EWs of
the 11.3um PAH feature and the H_2 S(1) line correlate closely, and we conclude
that shocks in the outflow regions have no measurable influence on the H_2
emission. The [NeIII]/[NeII] ratio is on average low at ~0.18, and shows little
variations across the plane, indicating that the dominant stellar population is
evolved (5 - 6 Myr) and well distributed. There is a slight increase of the
ratio with distance from the galactic plane of M82 which we attribute to a
decrease in gas density. Our observations indicate that the star formation rate
has decreased significantly in the last 5 Myr. The quantities of dust and
molecular gas in the central area of the galaxy argue against starvation and
for negative feedback processes, observable through the strong extra-planar
outflows.Comment: 15 pages, 12 figures, 3 tables, ApJ, emulateap
Association between changes in knee load and effusion-synovitis: evidence of mechano-inflammation in knee osteoarthritis using high tibial osteotomy as a model
Objective: Although mechanically-induced inflammation is an appealing explanation linking different etiologic factors in osteoarthritis (OA), clinical research investigating changes in both biomechanics and joint inflammation is limited. The purpose of this study was to evaluate the association between change in surrogate measures of knee load and knee effusion-synovitis in patients with medial compartment knee OA undergoing high tibial osteotomy (HTO). Methods: Thirty-six patients with medial compartment knee OA and varus alignment underwent 3D gait analysis and 3T magnetic resonance imaging (MRI) preoperatively and 1 year after medial opening wedge HTO. Primary outcome measures were the change in the external knee adduction moment impulse during walking and change in knee suprapatellar effusion-synovitis volume manually segmented on MRI by one blinded assessor. Results: Mean (SD) knee adduction moment impulse [24.0 (6.5) Nmâąs] and knee effusion-synovitis volume [8976.7 (8016.9) mm3] suggested substantial preoperative medial knee load and inflammation. 1-year postoperative changes in knee adduction moment impulse [â10.1 Nmâąs (95%CI: â12.7, â7.4)], and knee effusion-synovitis volume [â1856 mm3 (95%CI: â3830, 117)] were positively correlated [r = 0.60 (95% CI 0.34, 0.78)]. Simple linear regression suggested a 448 mm3 (95%CI: 241, 656) reduction in knee effusion-synovitis volume per 1 Nmâąs reduction in knee adduction moment impulse. Change in knee adduction moment impulse explained 36% (R2 = 0.36) of the variance of change in knee effusion-synovitis volume. Conclusions: Reduction in medial knee load is positively associated with reduction in knee inflammation after HTO, suggesting the phenomenon of mechano-inflammation in patients with knee OA
Powerful H Line-cooling in Stephan's Quintet : I - Mapping the Significant Cooling Pathways in Group-wide Shocks
We present results from the mid-infrared spectral mapping of Stephan's
Quintet using the Spitzer Space Telescope. A 1000 km/s collision has produced a
group-wide shock and for the first time the large-scale distribution of warm
molecular hydrogen emission is revealed, as well as its close association with
known shock structures. In the main shock region alone we find 5.0
M of warm H spread over 480 kpc and
additionally report the discovery of a second major shock-excited H
feature. This brings the total H line luminosity of the group in excess of
10 erg/s. In the main shock, the H line luminosity exceeds, by a
factor of three, the X-ray luminosity from the hot shocked gas, confirming that
the H-cooling pathway dominates over the X-ray. [Si II]34.82m
emission, detected at a luminosity of 1/10th of that of the H, appears to
trace the group-wide shock closely and in addition, we detect weak
[FeII]25.99m emission from the most X-ray luminous part of the shock.
Comparison with shock models reveals that this emission is consistent with
regions of fast shocks (100 < < 300 km/s) experiencing depletion of
iron and silicon onto dust grains. Star formation in the shock (as traced via
ionic lines, PAH and dust emission) appears in the intruder galaxy, but most
strikingly at either end of the radio shock. The shock ridge itself shows
little star formation, consistent with a model in which the tremendous H
power is driven by turbulent energy transfer from motions in a post-shocked
layer. The significance of the molecular hydrogen lines over other measured
sources of cooling in fast galaxy-scale shocks may have crucial implications
for the cooling of gas in the assembly of the first galaxies.Comment: 23 pages, 15 figures, Accepted to Ap
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