The Cloud Factory II: gravoturbulent kinematics of resolved molecular clouds in a galactic potential

Interstellar matter and star formatio

The HI/OH/Recombination line survey of the inner Milky Way (THOR): data release 2 and Hi overview

Context. The Galactic plane has been observed extensively by a large number of Galactic plane surveys from infrared to radio wavelengths at an angular resolution below 40". However, a 21 cm line and continuum survey with comparable spatial resolution is still missing. Aims. The first half of THOR data (l = 14.0 37.9, and l = 47.1 51.2, |b| < 1.25) has been published in our data release 1 paper (Beuther et al. 2016). With this data release 2 paper, we publish all the remaining spectral line data and Stokes I continuum data with high angular resolution (1000–4000) including a new H i dataset for the whole THOR survey region (l = 14.0 67.4 and |b| < 1.25). As we have published the results of OH lines and continuum emission elsewhere, we concentrate on the H i analysis in this paper. Methods. With the Karl G. Jansky Very Large Array (VLA) in C-configuration, we observed a large portion of the first Galactic quadrant achieving an angular resolution of < 40. At L Band, the WIDAR correlator at the VLA was set to cover the 21 cm H i line, four OH transitions, a series of Hn↵ radio recombination lines (RRLs; n = 151 to 186), and eight 128 MHz wide continuum spectral windows (SPWs) simultaneously. Results. We publish all OH and RRL data from the C-configuration observations, and a new H i dataset combining VLA C+D+GBT (VLA D-configuration and GBT data are from the VLA Galactic Plane Survey, Stil et al. 2006) for the whole survey. The H i emission shows clear filamentary substructures at negative velocities with low velocity crowding. The emission at positive velocities is more smeared-out likely due to higher spatial and velocity crowding of structures at the positive velocities. Comparing to the spiral arm model of the Milky Way, the atomic gas follows the Sagittarius and Perseus Arm well but with significant material in the inter-arm regions. With the C-configuration-only H i+continuum data, we produced a H i optical depth map of the THOR areal coverage from 228 absorption spectra with the nearest-neighbor method. With this ⌧ map, we corrected the H i emission for optical depth and the derived column density is 38% higher than the column density with optically thin assumption. The total H i mass with optical depth correction in the survey region is 4.7⇥108 M, 31% more than the mass derived assuming the emission is optically thin. If we apply this 31% correction to the whole Milky Way, the total atomic gas mass would be 9.4–10.5⇥109 M. Comparing the H i with existing CO data, we find a significant increase in the atomic-to-molecular gas ration from the spiral arms to the inter-arm regions. Conclusions. The high sensitivity and resolution THOR H i dataset provides an important new window on the physical and kinematic properties of gas in the inner Galaxy. Although the optical depth we derive is a lower limit, our study shows that the optical depth correction is significant for H i column density and mass estimation. Together with the OH, RRL and continuum emission from the THOR survey, these new H i data provide the basis for high angular-resolution studies of the interstellar medium (ISM) in different phases

Interstellar MHD Turbulence and Star Formation

This chapter reviews the nature of turbulence in the Galactic interstellar medium (ISM) and its connections to the star formation (SF) process. The ISM is turbulent, magnetized, self-gravitating, and is subject to heating and cooling processes that control its thermodynamic behavior. The turbulence in the warm and hot ionized components of the ISM appears to be trans- or subsonic, and thus to behave nearly incompressibly. However, the neutral warm and cold components are highly compressible, as a consequence of both thermal instability in the atomic gas and of moderately-to-strongly supersonic motions in the roughly isothermal cold atomic and molecular components. Within this context, we discuss: i) the production and statistical distribution of turbulent density fluctuations in both isothermal and polytropic media; ii) the nature of the clumps produced by thermal instability, noting that, contrary to classical ideas, they in general accrete mass from their environment; iii) the density-magnetic field correlation (or lack thereof) in turbulent density fluctuations, as a consequence of the superposition of the different wave modes in the turbulent flow; iv) the evolution of the mass-to-magnetic flux ratio (MFR) in density fluctuations as they are built up by dynamic compressions; v) the formation of cold, dense clouds aided by thermal instability; vi) the expectation that star-forming molecular clouds are likely to be undergoing global gravitational contraction, rather than being near equilibrium, and vii) the regulation of the star formation rate (SFR) in such gravitationally contracting clouds by stellar feedback which, rather than keeping the clouds from collapsing, evaporates and diperses them while they collapse.Comment: 43 pages. Invited chapter for the book "Magnetic Fields in Diffuse Media", edited by Elisabete de Gouveia dal Pino and Alex Lazarian. Revised as per referee's recommendation

Socioeconomic disparities in physical health among Aboriginal and Torres Strait Islander children in Western Australia

Objective. Few empirical studies have specifically examined the relationship between socio-economic status (SES) and health in Indigenous populations of Australia. We sought to provide insights into the nature of this relationship by examining socio-economic disparities in physical health outcomes among Aboriginal and Torres Strait Islander children in Western Australia. Design. We used a diverse set of health and SES indicators from a representative survey conducted in 20002002 on the health and development of 5289 Indigenous children aged 017 years in Western Australia. Analysis was conducted using multivariate logistic regression within a multilevel framework. Results. After controlling for age and sex, we found statistically significant socio- economic disparities in health in almost half of the associations that were investigated, although the direction, shape and magnitude of associations differed. For ear infections, recurring chest infections and sensory function problems, the patterns were generally consistent with a positive socio-economic gradient where better health was associated with higher SES. The reverse pattern was found for asthma, accidents and injuries, and oral health problems, although this was primarily observed for area-level SES indicators. Conclusion. Conventional notions of social position and class have some influence on the physical health of Indigenous children, although the diversity of results implies that there are other ways of conceptualising and measuring SES that are important for Indigenous populations. We need to consider factors that relate specifically to Indigenous circumstances and culture in the past and present day, and give more thought to how we measure social position in the Indigenous community, to gain a better understanding of the pathways from SES to Indigenous child health

Observing the First Stars and Black Holes

The high sensitivity of JWST will open a new window on the end of the cosmological dark ages. Small stellar clusters, with a stellar mass of several 10^6 M_sun, and low-mass black holes (BHs), with a mass of several 10^5 M_sun should be directly detectable out to redshift z=10, and individual supernovae (SNe) and gamma ray burst (GRB) afterglows are bright enough to be visible beyond this redshift. Dense primordial gas, in the process of collapsing from large scales to form protogalaxies, may also be possible to image through diffuse recombination line emission, possibly even before stars or BHs are formed. In this article, I discuss the key physical processes that are expected to have determined the sizes of the first star-clusters and black holes, and the prospect of studying these objects by direct detections with JWST and with other instruments. The direct light emitted by the very first stellar clusters and intermediate-mass black holes at z>10 will likely fall below JWST's detection threshold. However, JWST could reveal a decline at the faint-end of the high-redshift luminosity function, and thereby shed light on radiative and other feedback effects that operate at these early epochs. JWST will also have the sensitivity to detect individual SNe from beyond z=10. In a dedicated survey lasting for several weeks, thousands of SNe could be detected at z>6, with a redshift distribution extending to the formation of the very first stars at z>15. Using these SNe as tracers may be the only method to map out the earliest stages of the cosmic star-formation history. Finally, we point out that studying the earliest objects at high redshift will also offer a new window on the primordial power spectrum, on 100 times smaller scales than probed by current large-scale structure data.Comment: Invited contribution to "Astrophysics in the Next Decade: JWST and Concurrent Facilities", Astrophysics & Space Science Library, Eds. H. Thronson, A. Tielens, M. Stiavelli, Springer: Dordrecht (2008

TOPoS: III. An ultra iron-poor CEMP multiple system

Aims. One of the primary objectives of the TOPoS survey is to search for the most metal-poor stars. Our search has led to the discovery of one of the most iron-poor objects known, SDSS J092912.32+023817.0. This object is a multiple system, in which two components are clearly detected in the spectrum. Methods. We have analysed 16 high-resolution spectra obtained using the UVES spectrograph at the ESO 8.2 m VLT telescope to measure radial velocities and determine the chemical composition of the system. Results. Cross correlation of the spectra with a synthetic template yields a double-peaked cross-correlation function (CCF) for eight spectra, and in one case there is evidence for the presence of a third peak. Chemical analysis of the spectrum obtained by averaging all the spectra for which the CCF showed a single peak found that the iron abundance is [Fe/H]=–4.97. The system is also carbon enhanced with [C/Fe]=+3.91 (A(C) = 7.44). From the permitted oxygen triplet we determined an upper limit for oxygen of [O/Fe] 1.3. We are also able to provide more stringent upper limits on the Sr and Ba abundances ([Sr/Fe] < +0.70, and [Ba/Fe] < +1.46, respectively)

Association between Features of Spontaneous Late Preterm Labor and Late Preterm Birth

Objective This study aimed to evaluate the association between clinical and examination features at admission and late preterm birth. Study Design The present study is a secondary analysis of a randomized trial of singleton pregnancies at 34 0/7 to 36 5/7 weeks' gestation. We included women in spontaneous preterm labor with intact membranes and compared them by gestational age at delivery (preterm vs. term). We calculated a statistical cut-point optimizing the sensitivity and specificity of initial cervical dilation and effacement at predicting preterm birth and used multivariable regression to identify factors associated with late preterm delivery. Results A total of 431 out of 732 (59%) women delivered preterm. Cervical dilation ≥ 4 cm was 60% sensitive and 68% specific for late preterm birth. Cervical effacement ≥ 75% was 59% sensitive and 65% specific for late preterm birth. Earlier gestational age at randomization, nulliparity, and fetal malpresentation were associated with late preterm birth. The final regression model including clinical and examination features significantly improved late preterm birth prediction (81% sensitivity, 48% specificity, area under the curve = 0.72, 95% confidence interval [CI]: 0.68-0.75, and p -value &lt; 0.01). Conclusion Four in 10 women in late-preterm labor subsequently delivered at term. Combination of examination and clinical features (including parity and gestational age) improved late-preterm birth prediction

Feedback in W94A diagnosed with Radio Recombination Lines and Models

We present images of radio recombination lines (RRLs) at wavelengths around 18 cm from the star-forming region W49A to determine the kinematics of ionized gas in the THOR survey (The Hi/OH/Recombination line survey of the inner Milky Way) at an angular resolution of 16:08 X 13:08. The distribution of ionized gas appears to be affected by feedback processes from the star clusters inW49A. The velocity structure of the RRLs shows a complex behaviour with respect to the molecular gas. We find a shell-like distribution of ionized gas as traced by RRL emission surrounding the central cluster of OB stars in W49A. We describe the evolution of the shell with the recent feedback model code warpfield that includes the important physical processes and has previously been applied to the 30 Doradus region in the Large Magellanic Cloud. The cloud structure and dynamics of W49A are in agreement with a feedbackdriven shell that is re-collapsing. The shell may have triggered star formation in other parts of W49A. We suggest that W49A is a potential candidate for star formation regulated by feedback-driven and re-collapsing shells