18 research outputs found
A catalog of 1.5273 micron diffuse interstellar bands based on APOGEE hot telluric calibrators
High resolution stellar spectroscopic surveys provide massive amounts of
diffuse interstellar bands (DIBs) measurements. Data can be used to study the
distribution of the DIB carriers and those environmental conditions that favor
their formation. In parallel, recent studies have also proved that DIBs
extracted from stellar spectra constitute new tools for building the 3D
structure of the Galactic Interstellar Medium (ISM). The amount of details on
the structure depends directly on the quantity of available lines of sight
(LOS). Therefore there is a need to construct databases of high-quality DIB
measurements as large as possible. We aim at providing the community with a
catalog of high-quality measurements of the 1.5273 micron DIB towards a large
fraction of the Apache Point Observatory Galactic Evolution Experiment (APOGEE)
hot stars observed to correct for the telluric absorption and not used for ISM
studies so far. This catalog would complement the extensive database recently
extracted from the APOGEE observations and used for 3D ISM mapping. We devised
a method to fit the stellar continuum of the hot calibration stars and
extracted the DIB from the normalized spectrum. Severe selection criteria based
on the absorption characteristics are applied to the results. In particular
limiting constraints on the DIB widths and Doppler shifts are deduced from the
HI 21 cm measurements, following a new technique of decomposition of the
emission spectra. From ~16 000 available hot telluric spectra we have extracted
~ 6700 DIB measurements and their associated uncertainties. The statistical
properties of the extracted absorptions are examined and our selection criteria
are shown to provide a robust dataset. The resulting catalog contains the DIB
total equivalent widths, central wavelengths and widths. We briefly illustrate
its potential use for the stellar and interstellar communities.Comment: The Astrophysical Journal Supplement, in press, 35 pages, 14 figure
The ESO Diffuse Interstellar Bands Large Exploration Survey EDIBLES: I. Project description, survey sample and quality assessment
The carriers of the diffuse interstellar bands (DIBs) are largely unidentified molecules ubiquitously present in the interstellar medium (ISM). After decades of study, two strong and possibly three weak near-infrared DIBs have recently been attributed to the C+ 60 fullerene based on observational and laboratory measurements. There is great promise for the identification of the over 400 other known DIBs, as this result could provide chemical hints towards other possible carriers. In an effort to systematically study the properties of the DIB carriers, we have initiated a new large-scale observational survey: the ESO Diffuse Interstellar Bands Large Exploration Survey (EDIBLES). The main objective is to build on and extend existing DIB surveys to make a major step forward in characterising the physical and chemical conditions for a statistically significant sample of interstellar lines-of-sight, with the goal to reverse-engineer key molecular properties of the DIB carriers. EDIBLES is a filler Large Programme using the Ultraviolet and Visual Echelle Spectrograph at the Very Large Telescope at Paranal, Chile. It is designed to provide an observationally unbiased view of the presence and behaviour of the DIBs towards early-spectraltype stars whose lines-of-sight probe the diffuse-to-translucent ISM. Such a complete dataset will provide a deep census of the atomic and molecular content, physical conditions, chemical abundances and elemental depletion levels for each sightline. Achieving these goals requires a homogeneous set of high-quality data in terms of resolution (R ~ 70 000 â 100 000), sensitivity (S/N up to 1000 per resolution element), and spectral coverage (305â1042 nm), as well as a large sample size (100+ sightlines). In this first paper the goals, objectives and methodology of the EDIBLES programme are described and an initial assessment of the data is provided
PDRs4All II: JWST's NIR and MIR imaging view of the Orion Nebula
The JWST has captured the most detailed and sharpest infrared images ever
taken of the inner region of the Orion Nebula, the nearest massive star
formation region, and a prototypical highly irradiated dense photo-dissociation
region (PDR). We investigate the fundamental interaction of far-ultraviolet
photons with molecular clouds. The transitions across the ionization front
(IF), dissociation front (DF), and the molecular cloud are studied at
high-angular resolution. These transitions are relevant to understanding the
effects of radiative feedback from massive stars and the dominant physical and
chemical processes that lead to the IR emission that JWST will detect in many
Galactic and extragalactic environments. Due to the proximity of the Orion
Nebula and the unprecedented angular resolution of JWST, these data reveal that
the molecular cloud borders are hyper structured at small angular scales of
0.1-1" (0.0002-0.002 pc or 40-400 au at 414 pc). A diverse set of features are
observed such as ridges, waves, globules and photoevaporated protoplanetary
disks. At the PDR atomic to molecular transition, several bright features are
detected that are associated with the highly irradiated surroundings of the
dense molecular condensations and embedded young star. Toward the Orion Bar
PDR, a highly sculpted interface is detected with sharp edges and density
increases near the IF and DF. This was predicted by previous modeling studies,
but the fronts were unresolved in most tracers. A complex, structured, and
folded DF surface was traced by the H2 lines. This dataset was used to revisit
the commonly adopted 2D PDR structure of the Orion Bar. JWST provides us with a
complete view of the PDR, all the way from the PDR edge to the substructured
dense region, and this allowed us to determine, in detail, where the emission
of the atomic and molecular lines, aromatic bands, and dust originate
The 15â273 Ă diffuse interstellar band in the dark cloud Barnardâ68
International audienceHigh obscuration of background stars behind dark clouds precludes the detection of optical diffuse interstellar bands (DIBs) and hence our knowledge of DIB carriers in these environments. Taking advantage of the reduced obscuration of starlight in the near-infrared (NIR) we used one of the strongest NIR DIBs at 15â273 Ă
to probe the presence and properties of its carrier throughout the nearby interstellar dark cloud Barnardâ68. We measured equivalent widths (EW) for different ranges of visual extinction AV, using VLT/KMOS H-band (1.46â1.85 ÎŒm) moderate-resolution (R ~ 4000) spectra of 43 stars situated behind the cloud. To do so, we fitted the data with synthetic stellar spectra from the APOGEE project and TAPAS synthetic telluric transmissions appropriate for the observing site and time period. The results show an increase of DIB EW with increasing AV. However, the rate of increase is much flatter than expected from the EW-AV quasi-proportionality established for this DIB in the Galactic diffuse interstellar medium. Based on a simplified inversion assuming sphericity, it is found that the volume density of the DIB carrier is 2.7 and 7.9 times lower than this expected average value in the external and central regions of the cloud, which have nHâ 0.4 and 3.5 Ă 105 cm-3, respectively. Further measurements with multiplex NIR spectrographs should allow detailed modeling of such an edge effect of this DIB and other bands and help clarify its actual origin
The EDIBLES survey V: Line profile variations in the 5797, 6379, and 6614 diffuse interstellar bands as a tool to constrain carrier sizes
Several diffuse interstellar bands (DIBs) have profiles with resolved
sub-peaks that resemble rotational bands of large molecules. Analysis of these
profiles can constrain the sizes and geometries of the DIB carriers, especially
if the profiles exhibit clear variations along lines of sight probing different
physical conditions. Using the extensive data set from the EDIBLES survey we
searched for systematic variations in the peak-to-peak separation of these
sub-peaks for the 5797, 6379, and 6614 DIBs in lines of sight
with a single dominant interstellar cloud. We used the spectra of twelve
single-cloud sight lines to measure the peak-to-peak separation in the band
profile substructures for these DIBs. We adopted the rotational contour
formalism to infer the rotational constant for each DIB carrier and the
rotational excitation temperature in the sight lines. We compared these to
rotational constants for linear and spherical molecules to estimate the DIB
carrier sizes. All three DIBs have peak separations that vary systematically
between lines of sight, indicating correlated changes in the rotational
excitation temperatures. We derived =
cm, consistent with previous estimates. Assuming a similar rotational
temperature for the 6614 DIB carrier and assuming a linear carrier, we
found B and
B. If the
carriers of those DIBs however are spherical species, their rotational
constants are half that value, and . We estimate molecule sizes that range
from 7--9 carbon atoms (6614 carrier, linear) to 77--114 carbon atoms
(6379, spherical).Comment: 21 pages, 56 figures. Accepted for publication in Astronomy &
Astrophysic
Formation of the methyl cation by photochemistry in a protoplanetary disk
Forty years ago it was proposed that gas phase organic chemistry in the interstellar medium was initiated by the methyl cation CH + 3 (1-3), but hitherto it has not been observed outside the Solar System (4,5). Alternative routes involving processes on grain surfaces have been invoke
The ESO DIBs Large Exploration Survey
VizieR online Data Catalogue associated with article published in journal Astronomy & Astrophysics with title 'The ESO Diffuse Interstellar Bands Large Exploration Survey (EDIBLES). I. Project description, survey sample, and quality assessment.' (bibcode: 2017A&A...606A..76C
PDRs4All II: JWST's NIR and MIR imaging view of the Orion Nebula
International audienceThe JWST has captured the most detailed and sharpest infrared images ever taken of the inner region of the Orion Nebula, the nearest massive star formation region, and a prototypical highly irradiated dense photo-dissociation region (PDR). We investigate the fundamental interaction of far-ultraviolet photons with molecular clouds. The transitions across the ionization front (IF), dissociation front (DF), and the molecular cloud are studied at high-angular resolution. These transitions are relevant to understanding the effects of radiative feedback from massive stars and the dominant physical and chemical processes that lead to the IR emission that JWST will detect in many Galactic and extragalactic environments. Due to the proximity of the Orion Nebula and the unprecedented angular resolution of JWST, these data reveal that the molecular cloud borders are hyper structured at small angular scales of 0.1-1" (0.0002-0.002 pc or 40-400 au at 414 pc). A diverse set of features are observed such as ridges, waves, globules and photoevaporated protoplanetary disks. At the PDR atomic to molecular transition, several bright features are detected that are associated with the highly irradiated surroundings of the dense molecular condensations and embedded young star. Toward the Orion Bar PDR, a highly sculpted interface is detected with sharp edges and density increases near the IF and DF. This was predicted by previous modeling studies, but the fronts were unresolved in most tracers. A complex, structured, and folded DF surface was traced by the H2 lines. This dataset was used to revisit the commonly adopted 2D PDR structure of the Orion Bar. JWST provides us with a complete view of the PDR, all the way from the PDR edge to the substructured dense region, and this allowed us to determine, in detail, where the emission of the atomic and molecular lines, aromatic bands, and dust originate