A STUDY OF CARBON-MONOXIDE AND NEUTRAL CARBON IN THE S106 MOLECULAR CORE

Maps are presented of J=2-1 and J=3-2 (CO)-O-18 emission from the molecular environment of the bipolar nebula S106, together with complementary observations of the P-3(1)-P-3(0), C I emission. Line splitting observed extensively over the E molecular cloud suggests that it is best explained as the expanding remnant of a thick toroid surrounding the optical lobes. The poor correlation between the observed molecular line emission and dust continuum emission in the E cloud is probably due to a large temperature gradient. Strong C I emission from the protostellar candidate S106 FIR suggests the nearby presence of a powerful source of far-UV radiation, whose energy supply is unlikely to arise from gravitational contraction of a protostar. It is probable that this source is the star S106 LR, which also heats S106 FIR. There is evidence, in both C I and (CO)-O-18, for a predominantly blueshifted outflow from S106 IR, best interpreted as a stellar wind-driven shock into the toroidal remnant. (CO)-O-18 and (CO)-C-13 appear to be depleted, relative to canonical values for their abundances, in S106 FIR, despite its high optical extinction, which should discourage selective photodissociation. Elsewhere in the cloud the C I line profiles show a resemblance to those of (CO)-O-18, with intensity equivalent to a few photodissociation regions (PDRs) along the line of sight.

Restoration of adipose function in obese, glucose-tolerant men following pioglitazone treatment is associated with CCAAT enhancer-binding protein β upregulation

Obese AT (adipose tissue) exhibits increased macrophage number. Pro-inflammatory CD16+ peripheral monocyte numbers are also reported to increase with obesity. The present study was undertaken to simultaneously investigate obesity-associated changes in CD16+ monocytes and ATMs (AT macrophages). In addition, a pilot randomized placebo controlled trial using the PPAR (peroxisome-proliferator-activated receptor) agonists, pioglitazone and fenofibrate was performed to determine their effects on CD14+/CD16+ monocytes, ATM and cardiometabolic and adipose dysfunction indices. Obese glucose-tolerant men (n=28) were randomized to placebo, pioglitazone (30 mg/day) and fenofibrate (160 mg/day) for 12 weeks. A blood sample was taken to assess levels of serum inflammatory markers and circulating CD14+/CD16+ monocyte levels via flow cytometry. A subcutaneous AT biopsy was performed to determine adipocyte cell surface and ATM number, the latter was determined via assessment of CD68 expression by IHC (immunohistochemistry) and real-time PCR. Subcutaneous AT mRNA expression of CEBPß (CCAAT enhancer-binding protein ß), SREBP1c (sterol-regulatory-element-binding protein 1c), PPAR?2, IRS-1 (insulin receptor substrate-1), GLUT4 (glucose transporter type 4) and TNFa (tumour necrosis factor a) were also assessed. Comparisons were made between obese and lean controls (n=16) at baseline, and pre- and post-PPAR agonist treatment. Obese individuals had significantly increased adipocyte cell surface, percentage CD14+/CD16+ monocyte numbers and ATM number (all P=0.0001). Additionally, serum TNF-a levels were significantly elevated (P=0.017) and adiponectin levels reduced (total: P=0.0001; high: P=0.022) with obesity. ATM number and percentage of CD14+/CD16+ monocytes correlated significantly (P=0.05). Pioglitazone improved adiponectin levels significantly (P=0.0001), and resulted in the further significant enlargement of adipocytes (P=0.05), without effect on the percentage CD14+/CD16+ or ATM number. Pioglitazone treatment also significantly increased subcutaneous AT expression of CEBPß mRNA. The finding that improvements in obesity-associated insulin resistance following pioglitazone were associated with increased adipocyte cell surface and systemic adiponectin levels, supports the centrality of AT to the cardiometabolic derangement underlying the development of T2D (Type 2 diabetes) and CVD (cardiovascular disease).

Progenitors of Core-Collapse Supernovae

Knowledge of the progenitors of core-collapse supernovae is a fundamental component in understanding the explosions. The recent progress in finding such stars is reviewed. The minimum initial mass that can produce a supernova (SN) has converged to 8 +/- 1 M-circle dot from direct detections of red supergiant progenitors of II-P SNe and the most massive white dwarf progenitors, although this value is model dependent. It appears that most type Ibc SNe arise from moderate mass interacting binaries. The highly energetic, broad-lined Ic SNe are likely produced by massive, Wolf-Rayet progenitors. There is some evidence to suggest that the majority of massive stars above similar to 20 M-circle dot may collapse quietly to black holes and that the explosions remain undetected. The recent discovery of a class of ultrabright type H SNe and the direct detection of some progenitor stars bearing luminous blue variable characteristics suggest some very massive stars do produce highly energetic explosions. The physical mechanism is under debate, and these SNe pose a challenge to stellar evolutionary theory.

Core-collapse supernovae in low-metallicity environments and future all-sky transient surveys

Aims. Massive stars in low-metallicity environments may produce exotic explosions such as long-duration gamma-ray bursts and pair-instability supernovae when they die as core-collapse supernovae (CCSNe). Such events are predicted to be relatively common in the early Universe during the first episodes of star-formation. To understand these distant explosions it is vital to study nearby CCSNe arising in low-metallicity environments to determine if the explosions have different characteristics to those studied locally in high-metallicity galaxies. Many of the nearby supernova searches concentrate their efforts on high star-formation rate galaxies, hence biasing the discoveries to metal rich regimes. Here we determine the feasibility of searching for these CCSNe in metal-poor dwarf galaxies using various survey strategies.

Hubble Space Telescope imaging of the progenitor sites of six nearby core-collapse supernovae

The search for the progenitors of six core-collapse supernovae (CCSNe) in archival Hubble Space Telescope (HST) WFPC2 pre-explosion imaging is presented. These SNe are 1999an, 1999br, 1999ev, 2000ds, 2000ew and 2001B. Post-explosion imaging of the SNe, with the HST ACS/WFC, has been utilized with the technique of differential astrometry to identify the progenitor locations on the pre-explosion imaging. SNe 1999br, 1999ev, 2000ew and 2001B are recovered in late-time imaging, and estimates of the progenitor locations on the pre-explosion imaging, with subpixel accuracy, have been made. Only the progenitor of the Type II-P SN 1999ev has been recovered, on pre-explosion F555W imaging, at a 4.8 sigma significance level. Assuming a red supergiant progenitor, the pre-explosion observation is consistent with M-ZAMS = 15-18 M-circle dot. The progenitors of the other five SNe were below the 3 sigma detection threshold of the pre-explosion observations. The detection thresholds were translated to mass limits for the progenitors by comparison with stellar evolution models. Pre-explosion observations of the peculiarly faint SN 1999br limit the mass of a red supergiant progenitor to M-ZAMS

A comparison between star formation rate diagnostics and rate of core collapse supernovae within 11 Mpc

Aims. The core collapse supernova rate provides a strong lower limit for the star formation rate (SFR). Progress in using it as a cosmic SFR tracer requires some confidence that it is consistent with more conventional SFR diagnostics in the nearby Universe. This paper compares standard SFR measurements based on H alpha, far ultraviolet (FUV) and total infrared (TIR) galaxy luminosities with the observed core collapse supernova rate in the same galaxy sample. The comparison can be viewed from two perspectives. Firstly, by adopting an estimate of the minimum stellar mass to produce a core collapse supernova one can determine a SFR from supernova numbers. Secondly, the radiative SFR can be assumed to be robust and then the supernova statistics provide a constrain on the minimum stellar mass for core collapse supernova progenitors.