478 research outputs found
The HIFI spectral survey of AFGL 2591 (CHESS). II. Summary of the survey
This paper presents the richness of submillimeter spectral features in the
high-mass star forming region AFGL 2591. As part of the CHESS (Chemical
Herschel Survey of Star Forming Regions) Key Programme, AFGL 2591 was observed
by the Herschel/HIFI instrument. The spectral survey covered a frequency range
from 480 up to 1240 GHz as well as single lines from 1267 to 1901 GHz (i.e. CO,
HCl, NH3, OH and [CII]). Rotational and population diagram methods were used to
calculate column densities, excitation temperatures and the emission extents of
the observed molecules associated with AFGL 2591. The analysis was supplemented
with several lines from ground-based JCMT spectra. From the HIFI spectral
survey analysis a total of 32 species were identified (including
isotopologues). In spite of the fact that lines are mostly quite week, 268
emission and 16 absorption lines were found (excluding blends). Molecular
column densities range from 6e11 to 1e19 cm-2 and excitation temperatures range
from 19 to 175 K. One can distinguish cold (e.g. HCN, H2S, NH3 with
temperatures below 70 K) and warm species (e.g. CH3OH, SO2) in the protostellar
envelope.Comment: Accepted to A&
Herschel and the Molecular Universe
Over the next decade, space-based missions will open up the universe to high spatial and spectral resolution studies at infrared and submillimeter wavelengths. This will allow us to study, in much greater detail, the composition and the origin and evolution of molecules in space. Moreover, molecular transitions in these spectral ranges provide a sensitive probe of the dynamics and the physical and chemical conditions in a wide range of objects at scales ranging from budding planetary systems to galactic and extragalactic sizes. Hence, these missions provide us with the tools to study key astrophysical and astrochemical processes involved in the formation and evolution of planets, stars, and galaxies. These new missions can be expected to lead to the detection of many thousands of new spectral features. Identification, analysis and interpretation of these features in terms of the physical and chemical characteristics of the astronomical sources will require detailed astronomical modeling tools supported by laboratory measurements and theoretical studies of chemical reactions and collisional excitation rates on species of astrophysical relevance. These data will have to be made easily accessible to the scientific community through web-based data archives. In this paper, we will review the Herschel mission and its expected impact on our understanding of the molecular universe
Hot gas and dust in a protostellar cluster near W3(OH
We used the IRAM Interferometer to obtain sub-arcsecond resolution
observations of the high-mass star-forming region W3(OH) and its surroundings
at a frequency of 220 GHz. With the improved angular resolution, we distinguish
3 peaks in the thermal dust continuum emission originating from the hot core
region about 6 arcsec (0.06 pc) east of W3(OH). The dust emission peaks are
coincident with known radio continuum sources, one of which is of non-thermal
nature. The latter source is also at the center of expansion of a powerful
bipolar outflow observed in water maser emission. We determine the hot core
mass to be 15 solar masses based on the integrated dust continuum emission.
Simultaneously many molecular lines are detected allowing the analysis of the
temperature structure and the distribution of complex organic molecules in the
hot core. From HNCO lines, spanning a wide range of excitation, two 200 K
temperature peaks are found coincident with dust continuum emission peaks
suggesting embedded heating sources within them.Comment: 12 pages, 3 figure
Detection of water at z = 0.685 towards B0218+357
We report the detection of the H_2O molecule in absorption at a redshift z =
0.68466 in front of the gravitationally lensed quasar B0218+357. We detect the
fundamental transition of ortho-water at 556.93 GHz (redshifted to 330.59 GHz).
The line is highly optically thick and relatively wide (15 km/s FWHM), with a
profile that is similar to that of the previously detected CO(2--1) and
HCO^+(2--1) optically thick absorption lines toward this quasar. From the
measured level of the continuum at 330.59 GHz, which corresponds to the level
expected from the power-law spectrum already
observed at lower frequencies, we deduce that the filling factor of the H_2O
absorption is large. It was already known from the high optical thickness of
the CO, ^{13}CO and C^{18}O lines that the molecular clouds entirely cover one
of the two lensed images of the quasar (all its continuum is absorbed); our
present results indicate that the H_2O clouds are covering a comparable
surface. The H_2O molecules are therefore not confined to small cores with a
tiny filling factor, but are extended over parsec scales. The H_2O line has a
very large optical depth, and only isotopic lines could give us the water
abundance. We have also searched for the 183 GHz line in absorption, obtaining
only an upper limit; this yields constraints on the excitation temperature.Comment: 4 pages, 3 figures, accepted in ApJ Letter
Early warning signals and critical transitions in psychopathology:challenges and recommendations
Empirical evidence is mounting that monitoring momentary experiences for the presence of early warning signals (EWS) may allow for personalized predictions of meaningful symptom shifts in psychopathology. Studies aiming to detect EWS require intensive longitudinal measurement designs that center on individuals undergoing change. We recommend that researchers: (a) define criteria for relevant symptom shifts a priori to allow specific hypothesis testing; (b) balance the observation period length and high-frequency measurements with participant burden by testing ambitious designs with pilot studies; (c) choose variables that are meaningful to their patient group and facilitate replication by others. Thoroughly considered designs are necessary to assess the promise of EWS as a clinical tool to detect, prevent or encourage impending symptom changes in psychopathology
Detection of interstellar CH_3
Observations with the Short Wavelength Spectrometer (SWS) onboard the {\it
Infrared Space Observatory} (ISO) have led to the first detection of the methyl
radical in the interstellar medium. The branch at 16.5
m and the (0) line at 16.0 m have been unambiguously detected
toward the Galactic center SgrA. The analysis of the measured bands gives a
column density of (8.02.4) cm and an excitation
temperature of K. Gaseous at a similarly low excitation
temperature and are detected for the same line of sight. Using
constraints on the column density obtained from and
visual extinction, the inferred abundance is
. The chemically related
molecule is not detected, but the pure rotational lines of are seen
with the Long Wavelength Spectrometer (LWS). The absolute abundances and the
and ratios are inconsistent with published
pure gas-phase models of dense clouds. The data require a mix of diffuse and
translucent clouds with different densities and extinctions, and/or the
development of translucent models in which gas-grain chemistry, freeze-out and
reactions of with polycyclic aromatic hydrocarbons and solid
aliphatic material are included.Comment: 2 figures. ApJL, Accepte
Probing the Early Stages of Low-Mass Star Formation in LDN 1689N: Dust and Water in IRAS 16293-2422A, B, and E
We present deep images of dust continuum emission at 450, 800, and 850 micron
of the dark cloud LDN 1689N which harbors the low-mass young stellar objects
(YSOs) IRAS 16293-2422A and B (I16293A and I16293B) and the cold prestellar
object I16293E. Toward the positions of I16293A and E we also obtained spectra
of CO-isotopomers and deep submillimeter observations of chemically related
molecules with high critical densities. To I16293A we report the detection of
the HDO 1_01 - 0_00 and H2O 1_10 - 1_01 ground-state transitions as broad
self-reversed emission profiles with narrow absorption, and a tentative
detection of H2D+ 1_10 - 1_11. To I16293E we detect weak emission of
subthermally excited HDO 1_01 - 0_00. Based on this set of submillimeter
continuum and line data we model the envelopes around I16293A and E. The
density and velocity structure of I16293A is fit by an inside-out collapse
model, yielding a sound speed of a=0.7 km/s, an age of t=(0.6--2.5)e4 yr, and a
mass of 6.1 Msun. The density in the envelope of I16293E is fit by a radial
power law with index -1.0+/-0.2, a mass of 4.4 Msun, and a constant temperature
of 16K. These respective models are used to study the chemistry of the
envelopes of these pre- and protostellar objects.
The [HDO]/[H2O] abundance ratio in the warm inner envelope of I16293A of a
few times 1e-4 is comparable to that measured in comets. This supports the idea
that the [HDO]/[H2O] ratio is determined in the cold prestellar core phase and
conserved throughout the formation process of low-mass stars and planets.Comment: 61 pages, 17 figures. Accepted for publication in ApJ. To get Fig.
13: send email to [email protected]
ISO observations of far-infrared rotational emission lines of water vapor toward the supergiant star VY Canis Majoris
We report the detection of numerous far-infrared emission lines of water
vapor toward the supergiant star VY Canis Majoris. A 29.5 - 45 micron grating
scan of VY CMa, obtained using the Short Wavelength Spectrometer (SWS) of the
Infrared Space Observatory (ISO) at a spectral resolving power of approximately
2000, reveals at least 41 spectral features due to water vapor that together
radiate a total luminosity ~ 25 solar luminosities. In addition to pure
rotational transitions within the ground vibrational state, these features
include rotational transitions within the (010) excited vibrational state. The
spectrum also shows the doublet Pi 1/2 (J=5/2) <-- doublet Pi 3/2 (J=3/2) OH
feature near 34.6 micron in absorption. Additional SWS observations of VY CMa
were carried out in the instrument's Fabry-Perot mode for three water
transitions: the 7(25)-6(16) line at 29.8367 micron, the 4(41)-3(12) line
31.7721 micron, and the 4(32)-3(03) line at 40.6909 micron. The higher spectral
resolving power of approximately 30,000 thereby obtained permits the line
profiles to be resolved spectrally for the first time and reveals the "P Cygni"
profiles that are characteristic of emission from an outflowing envelope.Comment: 11 pages (inc. 2 figures), LaTeX, uses aaspp4.sty, accepted for
publication in ApJ Letter
High-Resolution Continuum Imaging at 1.3 and 0.7 cm of the W3 IRS 5 Region
High-resolution images of the hypercompact HII regions (HCHII) in W3 IRS 5
taken with the Very Large Array (VLA) at 1.3 and 0.7 cm are presented. Four
HCHII regions were detected with sufficient signal-to-noise ratios to allow the
determination of relevant parameters such as source position, size and flux
density. The sources are slightly extended in our ~0.2 arcsecond beams; the
deconvolved radii are less than 240 AU. A comparison of our data with VLA
images taken at epoch 1989.1 shows proper motions for sources IRS 5a and IRS
5f. Between 1989.1 and 2002.5, we find a proper motion of 210 mas at a position
angle of 12 deg for IRS 5f and a proper motion of 190 mas at a position angle
of 50 deg for IRS 5a. At the assumed distance to W3 IRS 5, 1.83 +/- 0.14 kpc,
these offsets translate to proper motions of ~135 km/s and ~122 km/s$
respectively. These sources are either shock ionized gas in an outflow or
ionized gas ejected from high mass stars. We find no change in the positions of
IRS 5d1/d2 and IRS 5b; and we show through a comparison with archival NICMOS
2.2 micron images that these two radio sources coincide with the infrared
double constituting W3 IRS 5. These sources contain B or perhaps O stars. The
flux densities of the four sources have changed compared to the epoch 1989.1
results. In our epoch 2002.5 data, none of the spectral indicies obtained from
flux densities at 1.3 and 0.7 cm are consistent with optically thin free-free
emission; IRS 5d1/d2 shows the largest increase in flux density from 1.3 cm to
0.7 cm. This may be an indication of free-free optical depth within an ionized
wind, a photoevaporating disk, or an accretion flow. It is less likely that
this increase is caused by dust emission at 0.7 cm.Comment: 13 pages, 3 figures To be published in The Astrophysical Journa
Detecting impending symptom transitions using early warning signals in individuals receiving treatment for depression
Background: The path to depressive symptom improvement during therapy is often complex, as many individuals experience periods of instability and discontinuous symptom change. If the process of remission follows complex dynamic systems principles, early warning signals (EWS) may precede such depressive symptom transitions. Aims: We aimed to test whether EWS, in the form of rises in lag-1 autocorrelation and variance, occur in momentary affect time series preceding transitions towards lower levels of depressive symptoms during therapy. We also investigated the presence of EWS in patients without symptom transitions. Methods: In a sample of 41 depressed individuals who were starting psychological treatment, positive affect and negative affect (high and low arousal) were measured five times a day using ecological momentary assessments (EMA) for four months (521 observations per individual on average; yielding 25,197 observations in total), and depressive symptoms were assessed weekly over six months. We used a moving window method and time-varying autoregressive generalized additive modeling (TV-AR GAM) to determine whether EWS occurred in these momentary affect measures, within-persons. Results: For the moving-window autocorrelation, 89% of individuals with transitions showed at least one EWS in one of the variables (versus 62.5% in the no-transition group), and the proportion of EWS in the separate variables was consistently higher (~44% across affect measures) than for individuals without transitions (~27%). Rising variance was found for few individuals, both preceding transitions (~11%) and for individuals without a transition (~12%). Conclusions: The process of symptom remission showed critical slowing down in at least part of our sample. Our findings indicate that EWS are not generic across all affect measures and may have limited value as a personalized prediction method
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