Star Formation in Bright Rimmed Clouds. I. Millimeter and Submillimeter Molecular Line Surveys

We present the results of the first detailed millimeter and submillimeter molecular line survey of bright rimmed clouds, observed at FCRAO in the CO (J=1-0), C18O (J=1-0), HCO+ (J=1-0), H13CO+ (J=1-0), and N2H+ (J=1-0) transitions, and at the HHT in the CO (J=2-1), HCO+ (J=3-2), HCO+ (J=4-3), H13CO+ (J=3-2), and H13CO+ (J=4-3) molecular line transitions. The source list is composed of a selection of bright rimmed clouds from the catalog of such objects compiled by Sugitani et al. (1991). We also present observations of three Bok globules done for comparison with the bright rimmed clouds. We find that the appearance of the millimeter CO and HCO+ emission is dominated by the morphology of the shock front in the bright rimmed clouds. The HCO+ (J=1-0) emission tends to trace the swept up gas ridge and overdense regions which may be triggered to collapse as a result of sequential star formation. Five of the seven bright rimmed clouds we observe seem to have an outflow, however only one shows the spectral line blue-asymmetric signature that is indicative of infall, in the optically thick HCO+ emission. We also present evidence that in bright rimmed clouds the nearby shock front may heat the core from outside-in thereby washing out the normally observed line infall signatures seen in isolated star forming regions. We find that the derived core masses of these bright rimmed clouds are similar to other low and intermediate mass star forming regions.Comment: 67 pages, including 35 figures and 6 tables. Accepted for publication in ApJ. Version with embedded full-resolution figures available at http://www.astro.umass.edu/~devries/brc1

Embedded Stellar Clusters in the W3/W4/W5 Molecular Cloud Complex

We analyze the embedded stellar content in the vicinity of the W3/W4/W5 HII regions using the FCRAO Outer Galaxy 12CO(J=1-0) Survey, the IRAS Point Source Catalog, published radio continuum surveys, and new near-infrared and molecular line observations. Thirty-four IRAS Point Sources are identified that have far-infrared colors characteristic of embedded star forming regions, and we have obtained K' mosaics and 13CO(J=1-0) maps for 32 of them. Ten of the IRAS sources are associated with an OB star and 19 with a stellar cluster, although three OB stars are not identified with a cluster. Half of the embedded stellar population identified in the K' images is found in just the 5 richest clusters, and 61% is contained in IRAS sources associated with an embedded OB star. Thus rich clusters around OB stars contribute substantially to the stellar population currently forming in the W3/W4/W5 region. Approximately 39% of the cluster population is embedded in small clouds with an average mass of ~130 Mo that are located as far as 100 pc from the W3/W4/W5 cloud complex. We speculate that these small clouds are fragments of a cloud complex dispersed by previous episodes of massive star formation. Finally, we find that 4 of the 5 known embedded massive star forming sites in the W3 molecular cloud are found along the interface with the W4 HII region despite the fact that most of the molecular mass is contained in the interior regions of the cloud. These observations are consistent with the classical notion that the W4 HII region has triggered massive star formation along the eastern edge of the W3 molecular cloud.Comment: to appear in ApJS, see http://astro.caltech.edu/~jmc/papers/w

Genetic Determinants of Glycated Hemoglobin in Type 1 Diabetes

Glycated hemoglobin (HbA(1c)) is an important measure of glycemia in diabetes. HbA(1c) is influenced by environmental and genetic factors both in people with and in people without diabetes. We performed a genome-wide association study (GWAS) for HbA(1c) in a Finnish type 1 diabetes (T1D) cohort, FinnDiane. Top results were examined for replication in T1D cohorts DCCT/EDIC, WESDR, CACTI, EDC, and RASS, and a meta-analysis was performed. Three SNPs in high linkage disequilibrium on chromosome 13 near relaxin family peptide receptor 2 (RXFP2) were associated with HbA(1c) in FinnDiane at genome-wide significance (P <5 x 10(-8)). The minor alleles of rs2085277 and rs1360072 were associated with higher HbA(1c) also in the meta-analysis with RASS (P <5 x 10(-8)), where these variants had minor allele frequencies 1%. Furthermore, these SNPs were associated with HbA(1c) in an East Asian population without diabetes (P 0.013). A weighted genetic risk score created from 55 HbA(1c)-associated variants from the literature was associated with HbA(1c) in FinnDiane but explained only a small amount of variation. Understanding the genetic basis of glycemic control and HbA(1c) may lead to better prevention of diabetes complications.Peer reviewe

Meta-genome-wide association studies identify a locus on chromosome 1 and multiple variants in the MHC region for serum C-peptide in type 1 diabetes

Aims/hypothesis The aim of this study was to identify genetic variants associated with beta cell function in type 1 diabetes, as measured by serum C-peptide levels, through meta-genome-wide association studies (meta-GWAS). Methods: We performed a meta-GWAS to combine the results from five studies in type 1 diabetes with cross-sectionally measured stimulated, fasting or random C-peptide levels, including 3479 European participants. The p values across studies were combined, taking into account sample size and direction of effect. We also performed separate meta-GWAS for stimulated (n = 1303), fasting (n = 2019) and random (n = 1497) C-peptide levels. Results: In the meta-GWAS for stimulated/fasting/random C-peptide levels, a SNP on chromosome 1, rs559047 (Chr1:238753916, T>A, minor allele frequency [MAF] 0.24–0.26), was associated with C-peptide (p = 4.13 × 10−8), meeting the genome-wide significance threshold (p T, MAF 0.07–0.10, p = 8.43 × 10−8). In the stimulated C-peptide meta-GWAS, rs61211515 (Chr6:30100975, T/–, MAF 0.17–0.19) in the MHC region was associated with stimulated C-peptide (β [SE] = − 0.39 [0.07], p = 9.72 × 10−8). rs61211515 was also associated with the rate of stimulated C-peptide decline over time in a subset of individuals (n = 258) with annual repeated measures for up to 6 years (p = 0.02). In the meta-GWAS of random C-peptide, another MHC region, SNP rs3135002 (Chr6:32668439, C>A, MAF 0.02–0.06), was associated with C-peptide (p = 3.49 × 10−8). Conditional analyses suggested that the three identified variants in the MHC region were independent of each other. rs9260151 and rs3135002 have been associated with type 1 diabetes, whereas rs559047 and rs61211515 have not been associated with a risk of developing type 1 diabetes. Conclusions/interpretation We identified a locus on chromosome 1 and multiple variants in the MHC region, at least some of which were distinct from type 1 diabetes risk loci, that were associated with C-peptide, suggesting partly non-overlapping mechanisms for the development and progression of type 1 diabetes. These associations need to be validated in independent populations. Further investigations could provide insights into mechanisms of beta cell loss and opportunities to preserve beta cell function. Electronic supplementary material The online version of this article (10.1007/s00125-018-4555-9) contains peer-reviewed but unedited supplementary material, which is available to authorised users

Large-scale (CO)-C-13 J=5 -\u3e 4 and [C I] mapping Of Orion A

We present maps of the 13CO J = 5 → 4 (551 GHz) and [C I] 3P1 → 3P0 (492 GHz) emission in the Orion A molecular cloud, covering a 05 × 2° area. A large velocity gradient (LVG) analysis of 13CO J = 5 → 4 and J = 1 → 0 suggests that the gas temperatures in the northern part of OMC-1 (north of Δδ = -20\u27) are ~45 K and are, on average, at least 20 K higher than those to the south. The average 13CO column density is log(N/cm-2) = 16.4 ± 0.3 and is fairly constant throughout the cloud, even in the low-temperature region south of BN/KL. LVG modeling of the [C I] emission shows a typical C0 column density of 2 × 1017 cm-2, which yields a C/CO abundance ratio in the cloud of ~0.1 (rising to levels in excess of 0.5 at the cloud edges). Comparison of the Δ-variance (which measures spatial structure in a manner similar to a power spectrum) of the Submillimeter Wave Astronomy Satellite [C I], Five College Radio Astronomy Observatory 13CO J = 1 → 0, and CS J = 1 → 0 velocity-integrated maps suggests that the [C I] and 13CO emission arise from the same gas. In contrast, the CS emission likely originates in gas that is considerably more clumpy