4,632 research outputs found
Discovery of Molecular Gas in the Outflow and Tidal Arms around M82
We present the first fully sampled map of 12CO (1-0) emission from M82
covering the entire galaxy. Our map contains a 12 x 15 kpc^2 area. We find that
extraplanar CO emission, previously reported at short distances above the
galactic plane, extends to heights of up to 6 kpc above the disk. Some of this
emission is associated with tidal arms seen in HI, implying either that M82
contained substantial amounts of molecular gas in the outer disk, or that
molecular gas formed after the tidal features. CO emission along the direction
of the outflow extends to distances of 3 kpc above and below the disk. At this
distance, the line is shifted in velocity about 100 km/s, and has the same
sense as the galactic outflow from the central starburst. This implies that
molecular gas may be entrained into the outflow.Comment: 4 pages, 6 figures. Uses emulateapj5. Accepted by ApJ Letter
SPI Measurements of Galactic 26Al
The precision measurement of the 1809 keV gamma-ray line from Galactic
Al is one of the goals of the SPI spectrometer on INTEGRAL with its Ge
detector camera. We aim for determination of the detailed shape of this
gamma-ray line, and its variation for different source regions along the plane
of the Galaxy. Data from the first part of the core program observations of the
first mission year have been inspected. A clear detection of the \Al line at
about 5--7 significance demonstrates that SPI will deepen \Al studies.
The line intensity is consistent with expectations from previous experiments,
and the line appears narrower than the 5.4 keV FWHM reported by GRIS, more
consistent with RHESSI's recent value. Only preliminary statements can be made
at this time, however, due to the multi-component background underlying the
signal at \about 40 times higher intensity than the signal from Galactic
Al.Comment: 5 pages, 8 figures; accepted for publication in A&A (special INTEGRAL
volume
The Interaction between the ISM and Star Formation in the Dwarf Starburst Galaxy NGC 4214
We present the first interferometric study of the molecular gas in the
metal-poor dwarf starburst galaxy NGC 4214. Our map of the 12CO(1-0) emission,
obtained at the OVRO millimeter array, reveals an unexpected structural wealth.
We detected three regions of molecular emission in the north-west (NW),
south-east (SE) and centre of NGC 4214 which are in very different and distinct
evolutionary stages (total molecular mass: 5.1 x 10^6 M_sun). These differences
are apparent most dramatically when the CO morphologies are compared to optical
ground based and HST imaging: massive star formation has not started yet in the
NW region; the well-known starburst in the centre is the most evolved and star
formation in the SE complex started more recently. We derive a star formation
efficiency of 8% for the SE complex. Using high--resolution VLA observations of
neutral hydrogen HI and our CO data we generated a total gas column density map
for NGC 4214 (HI + H_2). No clear correlation is seen between the peaks of HI,
CO and the sites of ongoing star formation. This emphasizes the irregular
nature of dwarf galaxies. The HI and CO velocities agree well, so do the
H-alpha velocities. In total, we cataloged 14 molecular clumps in NGC 4214. Our
results from a virial mass analysis are compatible with a Galactic CO-to-H_2
conversion factor for NGC 4214 (lower than what is usually found in metal-poor
dwarf galaxies).Comment: accepted for publication in the AJ (February 2001), full ps file at:
ftp://ftp.astro.caltech.edu/users/fw/ngc4214/walter_prep.p
Initial results from COMPTEL—an overview
COMPTEL is presently completing the first full sky survey in MeV gamma‐ray astronomy (0.7 to 30 MeV). An overview of initial results from the survey is given: among these are the observations of the Crab and Vela pulsars with unprecedented accuracy, the observation of the black hole candidates Cyg X‐1 and Nova Persei 1992, an analysis of the diffuse Galactic continuum emission from the Galactic center region, the broad scale distribution of the 1.8 MeV line from radioactive 2 6Al, upper limits on gamma‐ray line emission from SN 1991T, observations of the three quasars 3C273, 3C279 and PKS 0528+134 and the radio galaxy Cen A, measurements of energy spectra, time histories and locations of a number of cosmic gamma‐ray bursts, and gamma‐ray and neutron emission from solar flares
Molecular Gas in the Low Metallicity, Star Forming Dwarf IC 10
We present a complete survey of CO 1->0 emission in the Local Group dwarf
irregular IC 10. The survey, conducted with the BIMA interferometer, covers the
stellar disk and a large fraction of the extended HI envelope with the
sensitivity and resolution necessary to detect individual giant molecular
clouds (GMCs) at the distance of IC 10 (950 kpc). We find 16 clouds with a
total CO luminosity of 1 x 10^6 K km s^-1 pc^2, equivalent to 4 x 10^6 Msun of
molecular gas using the Galactic CO-to-H2 conversion factor. Observations with
the ARO 12m find that BIMA may resolve out as much as 50% of the CO emission,
and we estimate the total CO luminosity as 2.2 x 10^6 K km s^-1 pc^2. We
measure the properties of 14 GMCs from high resolution OVRO data. These clouds
are very similar to Galactic GMCs in their sizes, line widths, luminosities,
and CO-to-H2 conversion factors despite the low metallicity of IC 10 (Z ~ 1/5
Zsun). Comparing the BIMA survey to the atomic gas and stellar content of IC 10
we find that most of the CO emission is coincident with high surface density
HI. IC 10 displays a much higher star formation rate per unit molecular (H2) or
total (HI+H2) gas than most galaxies. This could be a real difference or may be
an evolutionary effect - the star formation rate may have been higher in the
recent past.Comment: 21 pages, 14 figures, Accepted to Ap
Giant Molecular Clouds in M31: I - Molecular Cloud Properties
We present Berkeley Illinois Maryland Association (BIMA) millimeter
interferometer observations of giant molecular clouds (GMCs) along a spiral arm
in M31. The observations consist of a survey using the compact configuration of
the interferometer and follow-up, higher-resolution observations on a subset of
the detections in the survey. The data are processed using an analysis
algorithm designed to extract GMCs and correct their derived properties for
observational biases thereby facilitating comparison with Milky Way data. The
algorithm identifies 67 GMCs of which 19 have sufficient signal-to-noise to
accurately measure their properties. The GMCs in this portion of M31 are
indistinguishable from those found in the Milky Way, having a similar size-line
width relationship and distribution of virial parameters, confirming the
results of previous, smaller studies. The velocity gradients and angular
momenta of the GMCs are comparable to the values measured in M33 and the Milky
Way; and, in all cases, are below expected values based on the local galactic
shear. The studied region of M31 has a similar interstellar radiation field,
metallicity, Toomre Q parameter, and midplane volume density as the inner Milky
Way, so the similarity of GMC populations between the two systems is not
surprising.Comment: Accepted for publication in the Astrophysical Journal. 13 pages, 7
figure
COMPTEL observations of cosmic gamma‐ray bursts
The imaging γ‐ray telescope COMPTEL on board NASA’s Compton Gamma‐Ray Observatory (GRO) has observed many cosmic gamma‐ray bursts during the early mission phase of GRO. COMPTEL records time‐resolved burst spectra over 0.1 MeV to 10 MeV energies, and, for the first time, produces direct single‐telescope gamma‐ray images (0.8–30 MeV) of cosmic gamma‐ray bursts occurring in its 1 sr field of field
Relationships between child development at school entry and adolescent health - a participatory systematic review
The relationship between child development and adolescent health, and how this may be modified by socio-economic conditions, is poorly understood. This limits cross-sector interventions to address adolescent health inequality. This review summarises evidence on the associations between child development at school starting age and subsequent health in adolescence and identifies factors affecting associations. We undertook a participatory systematic review, searching electronic databases (MEDLINE, PsycINFO, ASSIA and ERIC) for articles published between November 1990 and November 2020. Observational, intervention and review studies reporting a measure of child development and subsequent health outcomes, specifically weight and mental health, were included. Studies were individually and collectively assessed for quality using a comparative rating system of stronger, weaker, inconsistent or limited evidence. Associations between child development and adolescent health outcomes were assessed and reported by four domains of child development (socio-emotional, cognitive, language and communication, and physical development). A conceptual diagram, produced with stakeholders at the outset of the study, acted as a framework for narrative synthesis of factors that modify or mediate associations. Thirty-four studies were included. Analysis indicated stronger evidence of associations between measures of socio-emotional development and subsequent mental health and weight outcomes; in particular, positive associations between early externalising behaviours and later internalising and externalising, and negative associations between emotional wellbeing and later internalising and unhealthy weight. For all other domains of child development, although associations with subsequent health were positive, the evidence was either weaker, inconsistent or limited. There was limited evidence on factors that altered associations. Positive socio-emotional development at school starting age appears particularly important for subsequent mental health and weight in adolescence. More collaborative research across health and education is needed on other domains of development and on the mechanisms that link development and later health, and on how any relationship is modified by socio-economic context
Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites (BORTAS) experiment: design, execution and science overview
We describe the design and execution of the BORTAS (Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites) experiment, which has the overarching objective of understanding the chemical aging of air masses that contain the emission products from seasonal boreal wildfires and how these air masses subsequently impact downwind atmospheric composition. The central focus of the experiment was a two-week deployment of the UK BAe-146-301 Atmospheric Research Aircraft (ARA) over eastern Canada, based out of Halifax, Nova Scotia. Atmospheric ground-based and sonde measurements over Canada and the Azores associated with the planned July 2010 deployment of the ARA, which was postponed by 12 months due to UK-based flights related to the dispersal of material emitted by the Eyjafjallajökull volcano, went ahead and constituted phase A of the experiment. Phase B of BORTAS in July 2011 involved the same atmospheric measurements, but included the ARA, special satellite observations and a more comprehensive ground-based measurement suite. The high-frequency aircraft data provided a comprehensive chemical snapshot of pyrogenic plumes from wildfires, corresponding to photochemical (and physical) ages ranging from 45 sr 10 days, largely by virtue of widespread fires over Northwestern Ontario. Airborne measurements reported a large number of emitted gases including semi-volatile species, some of which have not been been previously reported in pyrogenic plumes, with the corresponding emission ratios agreeing with previous work for common gases. Analysis of the NOy data shows evidence of net ozone production in pyrogenic plumes, controlled by aerosol abundance, which increases as a function of photochemical age. The coordinated ground-based and sonde data provided detailed but spatially limited information that put the aircraft data into context of the longer burning season in the boundary layer. Ground-based measurements of particulate matter smaller than 2.5 μm (PM2.5) over Halifax show that forest fires can on an episodic basis represent a substantial contribution to total surface PM2.5
Magnetic Fields in the Milky Way
This chapter presents a review of observational studies to determine the
magnetic field in the Milky Way, both in the disk and in the halo, focused on
recent developments and on magnetic fields in the diffuse interstellar medium.
I discuss some terminology which is confusingly or inconsistently used and try
to summarize current status of our knowledge on magnetic field configurations
and strengths in the Milky Way. Although many open questions still exist, more
and more conclusions can be drawn on the large-scale and small-scale components
of the Galactic magnetic field. The chapter is concluded with a brief outlook
to observational projects in the near future.Comment: 22 pages, 5 figures, to appear in "Magnetic Fields in Diffuse Media",
eds. E.M. de Gouveia Dal Pino and A. Lazaria
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