37 research outputs found
Revealing the Young Starburst in Haro 3 with Radio and Infrared Imaging
The Wolf-Rayet galaxy Haro 3 (Mrk 35, NGC 3353) was observed at the near-IR
and radio wavelengths as part of ongoing program to study the earliest stages
of starbursts. These observations confirm that the current episode of star
formation is dominated by a single region (region A). While there are knots of
recent (~10 Myr) star formation outside of region A, the sources of ionizing
radiation as observed in both radio and Br-gamma observations are almost
exclusively associated with region A. The derived ionizing flux implies a star
formation rate of ~0.6 solar masses per year localized within a radius of ~0.1
kpc. A comparison with observations from HST indicates that one or more of the
star clusters in region A are optically obscured. The star clusters in region A
have ages at least as young as ~5 Myr, and possibly as young as ~0.1 Myr. The
star cluster that appears to be the youngest also exhibits a near-IR excess in
its colors, possibly indicating natal dust in very close proximity to the
ionizing stars. The difference between optical- and radio-determined ionizing
fluxes as well as the near-IR colors indicate an average extinction value of
A_V ~2.5 in region A. The total stellar mass associated with the current
starburst in region A is inferred from both the near-IR and radio observations
to be ~10^6 solar masses. The other main stellar concentrations observed in the
near-IR (Regions B1 and B2) are somewhat older than region A, with ages ~8-10
Myr, and the near-IR observations indicate they have stellar masses of ~8x10^4
and ~2x10^4 solar masses, respectively.Comment: 17 pages, 3 figures, to appear in AJ August 200
Absolute diffuse calibration of IRAC through mid-infrared and radio study of HII regions
We investigate the diffuse absolute calibration of the InfraRed Array Camera
on the Spitzer Space Telescope at 8.0microns using a sample of 43 HII regions
with a wide range of morphologies near GLON=312deg. For each region we
carefully measure sky-subtracted,point-source- subtracted, areally-integrated
IRAC 8.0-micron fluxes and compare these with Midcourse Space eXperiment (MSX)
8.3-micron images at two different spatial resolutions, and with radio
continuum maps. We determine an accurate median ratio of IRAC
8.0-micron/MSX\8.3-micron fluxes, of 1.55+/-0.15. From robust spectral energy
distributions of these regions we conclude that the present 8.0-micron diffuse
calibration of the SST is 36% too high compared with the MSX validated
calibration, perhaps due to scattered light inside the camera. This is an
independent confirmation of the result derived for the diffuse calibration of
IRAC by the Spitzer Science Center (SSC).
From regression analyses we find that 843-MHz radio fluxes of HII regions and
mid-infrared (MIR) fluxes are linearly related for MSX at 8.3-microns and
Spitzer at 8.0 microns, confirming the earlier MSX result by Cohen & Green. The
median ratio of MIR/843-MHz diffuse continuum fluxes is 600 times smaller in
nonthermal than thermal regions, making it a sharp discriminant. The ratios are
largely independent of morphology up to a size of ~24 arcsec. We provide
homogeneous radio and MIR morphologies for all sources. MIR morphology is not
uniquely related to radio structure. Compact regions may have MIR filaments
and/or diffuse haloes, perhaps infrared counter- parts to weakly ionized radio
haloes found around compact HII regions. We offer two IRAC colour-colour plots
as quantitative diagnostics of diffuse HII regions.Comment: 29 pages, LaTeX (aastex), incl. 31 PostScript (ps,eps) figures and 5
tables. Accepted by MNRAS (main journal). Replaced an unused file and added
this URL for people wishing to download a version with high-resolution
images: http://www.astro.wisc.edu/sirtf/martin.hii.accepted.pd
Spitzer IRAC observations of newly-discovered planetary nebulae from the Macquarie-AAO-Strasbourg H-alpha Planetary Nebula Project
We compare H-alpha, radio continuum, and Spitzer Space Telescope (SST) images
of 58 planetary nebulae (PNe) recently discovered by the Macquarie-AAO-Strasbo-
urg H-alpha PN Project (MASH) of the SuperCOSMOS H-alpha Survey. Using InfraRed
Array Camera (IRAC) data we define the IR colors of PNe and demonstrate good
isolation between these colors and those of many other types of astronomical
object. The only substantive contamination of PNe in the color-color plane we
illustrate is due to YSOs. However, this ambiguity is readily resolved by the
unique optical characteristics of PNe and their environs. We also examine the
relationships between optical and MIR morphologies from 3.6 to 8.0um and
explore the ratio of mid-infrared (MIR) to radio nebular fluxes, which is a
valuable discriminant between thermal and nonthermal emission. MASH emphasizes
late evolutionary stages of PNe compared with previous catalogs, enabling study
of the changes in MIR and radio flux that attend the aging process. Spatially
integrated MIR energy distributions were constructed for all MASH PNe observed
by the GLIMPSE Legacy Project, using the H-alpha morphologies to establish the
dimensions for the calculations of the Midcourse Space Experiment (MSX), IRAC,
and radio continuum (from the Molonglo Observatory Synthesis Telescope and the
Very Large Array) flux densities. The ratio of IRAC 8.0-um to MSX 8.3-um flux
densities provides a measure of the absolute diffuse calibration of IRAC at 8.0
um. We independently confirm the aperture correction factor to be applied to
IRAC at 8.0um to align it with the diffuse calibration of MSX. The result
agrees with the recommendations of the Spitzer Science Center and with results
from a parallel study of HII regions. These PNe probe the diffuse calibration
of IRAC on a spatial scale of 9-77 arcsec.Comment: 48 pages, LaTeX (aastex), incl. 18 PostScript (eps) figures and 3
tables. Accepted by Astrophysical Journa
Case report: intra-tendinous ganglion of the anterior cruciate ligament in a young footballer
A 20-year-old male medical student and keen rugby player presented with a 12-month history of progressively worsening right knee pain and stiffness with no history of trauma. Clinical examination revealed effusion and posterior knee pain exacerbated by end range movement and an extension lag of 15 degrees. Physiotherapy to improve the range of motion proved unsuccessful. Magnetic resonance imaging showed that the ACL was grossly thickened and displaced by material reported as mucoid in nature. There were also areas of focally high signal in relation to its tibial attachment and intra osseous small cysts. Arthroscopic examination revealed a ganglion related to the tibial attachment of the ACL and gross thickening and discoloration of the ACL. Biopsies were taken showing foci of mucoid degeneration in the ACL. A large intra-ACL mass of brownish coloured tissue was excised arthroscopically. Already at 2 weeks follow up the patient had greatly improved range of movement and was pain free. However, upon returning to rugby, joint instability was noticed and a tear of the ACL was confirmed.
This rare clinical condition can be diagnosed with MRI and arthroscopic debridement effectively relieves symptoms. This case report illustrates that augmentation or reconstruction may end up being the definitive treatment for athletes. It may also offer some support to the argument that mucoid degeneration and ganglion cyst formation share a similar pathogenesis to intra-osseous cyst formation
G313.3+00.3: A New Planetary Nebula discovered by the Australia Telescope Compact Array and the Spitzer Space Telescope
We present a new planetary nebula, first identified in images from the
Australia Telescope Compact Array, although not recognized at that time. Recent
observations with the Spitzer Space Telescope during the GLIMPSE Legacy program
have rediscovered the object. The high-resolution radio and infrared images
enable the identification of the central star or its wind, the recognition of
the radio emission as thermal, and the probable presence of polycylic aromatic
hydrocarbons in and around the source. These lead to the conclusion that
G313.3+00.3 is a planetary nebula. This object is of particular interest
because it was discovered solely through radio and mid-infrared imaging,
without any optical (or near-infrared) confirmation, and acts as a proof of
concept for the discovery of many more highly extinguished planetary nebulae.
G313.3+00.3 is well-resolved by both the instruments with which it was
identified, and suffers extreme reddening due to its location in the
Scutum-Crux spiral arm.Comment: 18 pages, LaTeX (aastex), incl. 8 PostScript (eps) figures and 1
table. Accepted by ApJ (Part 1
Evolution of Asthma Severity in a Cohort of Young Adults: Is There Any Gender Difference?
INTRODUCTION:Little is known about the distribution of asthma severity in men and women in the general population. The objective of our study was to describe asthma severity and change in severity according to gender in a cohort of adult asthmatics METHODS:Subjects with asthma were identified from random samples of the 22 to 44 year-olds from the general population, screened for asthma from 1991 to 1993 in 48 centers from 22 countries and followed-up during 1998-2002, as part of the European Community Respiratory Health Survey (ECRHS). All participants to follow-up with current asthma at baseline were eligible for the analysis. To assess change over the follow-up, asthma severity at the two surveys was defined using standardized data on respiratory symptoms, lung function and medication according to the Global Initiative for Asthma (GINA) Guidelines. Another quantitative score (Ronchetti) further considering hospitalizations was also analysed. RESULTS:The study included 685 subjects with asthma followed-up over a mean period of 8.65 yr (min 4.3-max 11.7). At baseline, asthma severity according to GINA was distributed as intermittent: 40.7%, 31.7% as mild persistent, 14% as moderate persistent, and 13.5% as severe persistent. Using the Ronchetti score derived classification, the distribution of asthma severity was 58% mild, (intermittent and mild persistent), 25.8% moderate, and 15.4% severe. Whatever the classification, there was no significant difference in the severity distribution between men and women. There was also no gender difference in the severity distribution among incident cases which developed asthma between the two surveys. Men with moderate-to-severe asthma at baseline were more likely than women to have moderate-to-severe asthma at follow-up. Using GINA, 69.2% of men vs. 53.1% of women (p = 0.09) with moderate-to-severe asthma at baseline were still moderate-to-severe at follow-up. Using Ronchetti score, 53.3% of men vs. 36.2% of women (p = 0.03) with moderate-to-severe asthma at baseline were still moderate-to-severe at follow-up. CONCLUSIONS:There was no gender difference in asthma severity at the two surveys. However, our findings suggest that asthma severity might be less stable in women than in men
Spatially restricted patterning cues provided by heparin-binding VEGF-A control blood vessel branching morphogenesis
Branching morphogenesis in the mammalian lung and Drosophila trachea relies on the precise localization of secreted modulators of epithelial growth to select branch sites and direct branch elongation, but the intercellular signals that control blood vessel branching have not been previously identified. We found that VEGF(120/120) mouse embryos, engineered to express solely an isoform of VEGF-A that lacks heparin-binding, and therefore extracellular matrix interaction domains, exhibited a specific decrease in capillary branch formation. This defect was not caused by isoform-specific differences in stimulating endothelial cell proliferation or by impaired isoform-specific signaling through the Nrp1 receptor. Rather, changes in the extracellular localization of VEGF-A in heparin-binding mutant embryos resulted in an altered distribution of endothelial cells within the growing vasculature. Instead of being recruited into additional branches, nascent endothelial cells were preferentially integrated within existing vessels to increase lumen caliber. The disruption of the normal VEGF-A concentration gradient also impaired the directed extension of endothelial cell filopodia, suggesting that heparin-binding VEGF-A isoforms normally provide spatially restricted stimulatory cues that polarize and thereby guide sprouting endothelial cells to initiate vascular branch formation. Consistent with this idea, we found opposing defects in embryos harboring only a heparin-binding isoform of VEGF-A, including excess endothelial filopodia and abnormally thin vessel branches in ectopic sites. We conclude that differential VEGF-A isoform localization in the extracellular space provides a control point for regulating vascular branching pattern