133 research outputs found
Extended Far-Infrared CO Emission in the Orion OMC-1 Core
We report on sensitive far-infrared observations of CO pure rotational
transitions in the OMC-1 core of Orion. The lines were observed with the Long
Wavelength Spectrometer (LWS) in the grating mode on board the Infrared Space
Observatory (ISO), covering the 43-197 m wavelength range. The transitions
from up to have been identified across the whole OMC-1
core and lines up to have been detected towards the central
region, KL/IRc2. In addition, we have taken high-quality spectra in the
Fabry-Perot mode of some of the CO lines. In KL/IRc2 the lines are
satisfactorily accounted for by a three-temperature model describing the
plateau and ridge emission. The fluxes detected in the high- transitions
() reveal the presence of a very hot and dense gas component
( K; =2\times 10^{17}\cmmd\rm H_2\geq 80$ K and as high as 150 K at some positions around IRc2,
from a simple Large-Velocity Gradient model.Comment: 10 pages, 3 figure
Recommended from our members
Molecular line emissions from pre main sequence objects
We present some preliminary results obtained with the LWS G.T. programme on the study of young objects driving molecular outflows. In particular, we discuss the importance of molecular emission in these sources and address the role of the H20 cooling
Recommended from our members
ISO-LWS study of pre-main sequence sources
We present the results obtained with the ISO Long Wavelength Spectrometer on a sample of Pre-MS sources, where several molecular lines of CO, H2O and OH have been detected. The analysis of the CO lines indicates that gas temperatures as low as 200 K are consistent with the data. This would be in agreement with the relatively low abundance of water in the gas phase measured in most of the objects
Open questions in the social lives of viruses
Social interactions among viruses occur whenever multiple viral genomes infect the same cells, hosts, or populations of hosts. Viral social interactions range from cooperation to conflict, occur throughout the viral world, and affect every stage of the viral lifecycle. The ubiquity of these social interactions means that they can determine the population dynamics, evolutionary trajectory, and clinical progression of viral infections. At the same time, social interactions in viruses raise new questions for evolutionary theory, providing opportunities to test and extend existing frameworks within social evolution. Many opportunities exist at this interface: Insights into the evolution of viral social interactions have immediate implications for our understanding of the fundamental biology and clinical manifestation of viral diseases. However, these opportunities are currently limited because evolutionary biologists only rarely study social evolution in viruses. Here, we bridge this gap by (1) summarizing the ways in which viruses can interact socially, including consequences for social evolution and evolvability; (2) outlining some open questions raised by viruses that could challenge concepts within social evolution theory; and (3) providing some illustrative examples, data sources, and conceptual questions, for studying the natural history of social viruses
An invitation to grieve: reconsidering critical incident responses by support teams in the school setting
This paper proposes that consideration could be given to an invitational intervention rather than an expectational intervention when support personnel respond to a critical incident in schools. Intuitively many practitioners know that it is necessary for guidance/counselling personnel to intervene in schools in and following times of trauma. Most educational authorities in Australia have mandated the formulation of a critical incident intervention plan. This paper defines the term critical incident and then outlines current intervention processes, discussing the efficacy of debriefing interventions. Recent literature suggests that even though it is accepted that a planned intervention is necessary, there is scant evidence as to the effectiveness of debriefing interventions in stemming later symptoms of post traumatic stress disorder. The authors of this paper advocate for an expressive therapy intervention that is invitational rather than expectational, arguing that not all people respond to trauma in the same way and to expect that they will need to recall and retell what has happened is most likely a dangerous assumption. A model of invitation using Howard Gardner’s (1983) multiple intelligences is proposed so that students are invited to grieve and understand emotionally what is happening to them following a critical incident
Herschel imaging of the dust in the Helix Nebula (NGC 7293)
In our series of papers presenting the Herschel imaging of evolved planetary
nebulae, we present images of the dust distribution in the Helix nebula (NGC
7293). Images at 70, 160, 250, 350, and 500 micron were obtained with the PACS
and SPIRE instruments on board the Herschel satellite. The broadband maps show
the dust distribution over the main Helix nebula to be clumpy and predominantly
present in the barrel wall. We determined the spectral energy distribution of
the main nebula in a consistent way using Herschel, IRAS, and Planck flux
values. The emissivity index of 0.99 +/- 0.09, in combination with the carbon
rich molecular chemistry of the nebula, indicates that the dust consists mainly
of amorphous carbon. The dust excess emission from the central star disk is
detected at 70 micron and the flux measurement agree with previous measurement.
We present the temperature and dust column density maps. The total dust mass
across the Helix nebula (without its halo) is determined to be 0.0035 solar
mass at a distance of 216 pc. The temperature map shows dust temperatures
between 22 and 42 K, which is similar to the kinetic temperature of the
molecular gas, strengthening the fact that the dust and gas co-exist in high
density clumps. Archived images are used to compare the location of the dust
emission in the far infrared (Herschel) with the ionized (GALEX, Hbeta) and
molecular hydrogen component. The different emission components are consistent
with the Helix consisting of a thick walled barrel-like structure inclined to
the line of sight. The radiation field decreases rapidly through the barrel
wall.Comment: 8 pages, 9 figures, revised version A&A in pres
ISO-LWS two colour diagram of young stellar objects
We present a [60--100] vs. [100--170] m two colour diagram for a sample
of 61 young stellar objects (YSOs) observed with the Long Wavelength
Spectrometer (LWS) on-board the Infrared Space Observatory (ISO). The sample
consists of 17 Class 0 sources, 15 Class I, 9 Bright Class I (), 20 Class II (14 Herbig Ae/Be stars and 6 T Tauri stars). We find
that each class occupies a well defined region in our diagram with colour
temperatures increasing from Class 0 to Class II. Therefore the [60--100] vs.
[100--170] two colours diagram is a powerful and simple tool to derive from
future (e.g. with the Herschel Space Observatory) photometric surveys the
evolutionary status of YSOs. The advantage over other tools already developed
is that photometry at other wavelengths is not required: three flux
measurements are enough to derive the evolutionary status of a source. As an
example we use the colours of the YSO IRAS 181480440 to classify it as Class
I. The main limitation of this work is the low spatial resolution of the LWS
which, for some objects, causes a high uncertainty in the measured fluxes due
to the background emission or to the source confusion inside the LWS beam.Comment: 7 pages, 2 figures, requires mn2e document class. Accepted by MNRA
Recommended from our members
An investigation of the B335 region through far infrared spectroscopy with ISO
We present far infrared spectra of the B335 dark cloud region, obtained with the Long Wavelength Spectrometer (LWS) on-board the ISO satellite. Deep spectra were obtained towards the far infrared outflow exciting source, located in the B335 core, and on the three associated Herbig Haro (HH) objects HH119 A, B and C. In addition, a region of about 9' in RA and 4' in Dec. was mapped which covers the whole molecular outflow. [CII]158 μm emission was found to be uniformly distributed across the observed region, with the intensity expected for a photodissociation region excited by the average interstellar field. The [OI]63 μm emission was detected only towards two out of the three HH objects and from the B335 FIR source; excitation from the high-velocity shocks responsible for the HH119 knots can account for the observed line intensity. CO line emission from the rotational levels J=15 to J=18 was detected only towards B335 FIR and can be modelled as arising in warm gas whose excitation temperature is in the range 150-800 K, located in a compact ( ~ 10-3 pc) and dense (nH2 ~ 106 cm-3 ) region. If we assume that the CO J = 6→5 line observed from the ground is also emitted from the same gas component, we derive for this component a temperature of 350 K and a density of 5•105 cm-3. Current collapse models for the B335 core fail to predict the presence of such warm gas in the infalling source envelope, at the spatial scales implied by our model fit. It is likely that the molecular emission is excited in a low-velocity (v ~ 10 km s-1 ) non-dissociative shock, originating at the base of the flow
- …