Context. The 15N isotopologue abundance ratio measured today in different bodies of the solar system is thought to be connected to 15N-fractionation effects that would have occurred in the protosolar ...nebula. Aims. The present study aims at putting constraints on the degree of 15N-fractionation that occurs during the prestellar phase, through observations of D, 13C, and 15N-substituted isotopologues towards B1b. Molecules both from the nitrogen hydride family, i.e. N2H+, and NH3, and from the nitrile family, i.e. HCN, HNC, and CN, are considered in the analysis. Methods. As a first step, we modelled the continuum emission in order to derive the physical structure of the cloud, i.e. gas temperature and H2 density. These parameters were subsequently used as input in a non-local radiative transfer model to infer the radial abundance profiles of the various molecules. Results. Our modelling shows that all the molecules are affected by depletion onto dust grains in the region that encompasses the B1-bS and B1-bN cores. While high levels of deuterium fractionation are derived, we conclude that no fractionation occurs in the case of the nitrogen chemistry. Independently of the chemical family, the molecular abundances are consistent with 14N/15N ~ 300, a value representative of the elemental atomic abundances of the parental gas. Conclusions. The inefficiency of the 15N-fractionation effects in the B1b region can be linked to the relatively high gas temperature ~17 K, which is representative of the innermost part of the cloud. Since this region shows signs of depletion onto dust grains, we cannot exclude the possibility that the molecules were previously enriched in 15N, earlier in the B1b history and that such an enrichment could have been incorporated into the ice mantles. It is thus necessary to repeat this kind of study in colder sources to test such a possibility.
We present the initial highlights of the HOBYS key program, which are based on Herschel images of the Rosette molecular complex and maps of the RCW120 H ii region. Using both SPIRE at 250/350/500 μm ...and PACS at 70/160 μm or 100/160 μm, the HOBYS survey provides an unbiased and complete census of intermediate- to high-mass young stellar objects, some of which are not detected by Spitzer. Key core properties, such as bolometric luminosity and mass (as derived from spectral energy distributions), are used to constrain their evolutionary stages. We identify a handful of high-mass prestellar cores and show that their lifetimes could be shorter in the Rosette molecular complex than in nearby low-mass star-forming regions. We also quantify the impact of expanding H ii regions on the star formation process acting in both Rosette and RCW 120.
Context.
The CII 158 μm far-infrared fine-structure line is one of the dominant cooling lines of the star-forming interstellar medium. Hence CII emission originates in and thus can be used to trace a ...range of ISM processes. Velocity-resolved large-scale mapping of CII in star-forming regions provides a unique perspective of the kinematics of these regions and their interactions with the exciting source of radiation.
Aims.
We explore the scientific applications of large-scale mapping of velocity-resolved CII observations. With the CII observations, we investigate the effect of stellar feedback on the ISM. We present the details of observation, calibration, and data reduction using a heterodyne array receiver mounted on an airborne observatory.
Methods.
A 1.15 square degree velocity-resolved map of the Orion molecular cloud centred on the bar region was observed using the German REceiver for Astronomy at Terahertz Frequencies (upGREAT) heterodyne receiver flying on board the Stratospheric Observatory for Infrared Astronomy. The data were acquired using the 14 pixels of the German REceiver for Astronomy at Terahertz Frequencies that were observed in an on-the-fly mapping mode. 2.4 million spectra were taken in total. These spectra were gridded into a three-dimensional cube with a spatial resolution of 14.1 arcseconds and a spectral resolution of 0.3 km s
−1
.
Results.
A square-degree CII map with a spectral resolution of 0.3 km s
−1
is presented. The scientific potential of this data is summarized with discussion of mechanical and radiative stellar feedback, filament tracing using CII, CII opacity effects, CII and carbon recombination lines, and CII interaction with the large molecular cloud. The data quality and calibration is discussed in detail, and new techniques are presented to mitigate the effects of unavoidable instrument deficiencies (e.g. baseline stability) and thus to improve the data quality. A comparison with a smaller CII map taken with the
Herschel
/Heterodyne Instrument for the Far-Infrared spectrometer is presented.
Conclusions.
Large-scale CII mapping provides new insight into the kinematics of the ISM. The interaction between massive stars and the ISM is probed through CII observations. Spectrally resolving the CII emission is necessary to probe the microphysics induced by the feedback of massive stars. We show that certain heterodyne instrument data quality issues can be resolved using a spline-based technique, and better data correction routines allow for more efficient observing strategies.
Context. The variability in IRC+10216, the envelope of the asymptotic giant branch (AGB) star CW Leo, has attracted increasing attention in recent years. Studying the details of this variability in ...the molecular emission required a systematic observation program. Aims. We aim to reveal and characterize the periodical variability of the rotational lines from several molecules and radicals in IRC+10216, and to compare it with previously reported IR variability. Methods. We carried out systematic monitoring within the ~80–116 GHz frequency range with the IRAM 30 m telescope. Results. We report on the periodical variability in IRC+10216 of several rotational lines from the following molecules and radicals: HC3N, HC5N, CCH, C4H, C5H, and CN. The analysis of the variable molecular lines provides periods that are consistent with previously reported IR variability, and interesting phase lags are revealed that point toward radiative transfer and pumping, rather than chemical effects. Conclusions. This study indicates that observations of several lines of a given molecule have to be performed simultaneously or at least at the same phase in order to avoid erroneous interpretation of the data. In particular, merging ALMA data from different epochs may prove to be difficult, as shown by the example of the variability we studied here. Moreover, radiative transfer codes have to incorporate the effect of population variability in the rotational levels in CW Leo.
Abstract
Asteroids (24) Themis and (65) Cybele have an absorption feature at 3.1
μ
m reported to be directly linked to surface water ice. We searched for water vapor escaping from these asteroids ...with the Herschel Space Observatory Heterodyne Instrument for the Far Infrared. While no H
2
O line emission was detected, we obtain sensitive 3
σ
water production rate upper limits of
Q
(H
2
O) < 4.1 × 10
26
molecules s
−1
for Themis and
Q
(H
2
O) < 7.6 × 10
26
molecules s
−1
for Cybele. Using a thermophysical model, we merge data from the Subaru/Cooled Mid-Infrared Camera and Spectrometer and the Herschel/Spectral and Photometric Imaging Receiver with the contents of a multi-observatory database to derive new radiometric properties for these two asteroids. For Themis, we find a thermal inertia
J m
−2
s
−1/2
K
−1
, a diameter
km, and a geometric
V
-band albedo
p
V
= 0.07 ± 0.01. For Cybele, we obtain a thermal inertia
J m
−2
s
−1/2
K
−1
, a diameter 282 ± 9 km, and an albedo
p
V
= 0.042 ± 0.005. Using all inputs, we estimate that water ice intimately mixed with the asteroids’ dark surface material would cover <0.0017% (for Themis) and <0.0033% (for Cybele) of their surfaces, while an areal mixture with very clean ice (Bond albedo 0.8 for Themis and 0.7 for Cybele) would cover <2.2% (for Themis) and <1.5% (for Cybele) of their surfaces. While surface (and subsurface) water ice may exist in small localized amounts on both asteroids, it is not the reason for the observed 3.1
μ
m absorption feature.
The properties of molecular gas, the fuel that forms stars, inside the cavity of the circumnuclear disk (CND) are not well constrained. We present results of a velocity-resolved submillimeter scan ...(~480 to 1250 GHz) and C ii 158
m line observations carried out with
/HIFI toward Sgr A*; these results are complemented by a ~2'×2'
CO (
=3-2) map taken with the IRAM 30 m telescope at ~7″ resolution. We report the presence of high positive-velocity emission (up to about +300 km s
) detected in the wings of
CO
=5-4 to 10-9 lines. This wing component is also seen in H
O (1
-1
), a tracer of hot molecular gas; in C ii158
m, an unambiguous tracer of UV radiation; but not in C i 492, 806 GHz. This first measurement of the high-velocity
CO rotational ladder toward Sgr A* adds more evidence that hot molecular gas exists inside the cavity of the CND, relatively close to the supermassive black hole (< 1 pc). Observed by ALMA, this velocity range appears as a collection of
CO (
=3-2) cloudlets lying in a very harsh environment that is pervaded by intense UV radiation fields, shocks, and affected by strong gravitational shears. We constrain the physical conditions of the high positive-velocity CO gas component by comparing with non-LTE excitation and radiative transfer models. We infer
≃400 K to 2000 K for
≃(0.2-1.0)·10
cm
. These results point toward the important role of stellar UV radiation, but we show that radiative heating alone cannot explain the excitation of this ~10-60
component of hot molecular gas inside the central cavity. Instead, strongly irradiated shocks are promising candidates.
The properties of molecular gas, the fuel that forms stars, inside the cavity of the circumnuclear disk (CND) are not well constrained. We present results of a velocity-resolved submillimeter scan ...(~480–1250 GHz) and C II 158 μm line observations carried out with Herschel/HIFI toward Sgr A*; these results are complemented by a ~2′ × 2′ 12CO (J = 3−2) map taken with the IRAM 30 m telescope at ~7″ resolution. We report the presence of high positive-velocity emission (up to about +300 km s−1) detected in the wings of 12CO J = 5−4 to 10−9 lines. This wing component is also seen in H2O (11,0−10,1), a tracer of hot molecular gas; in C II158 μm, an unambiguous tracer of UV radiation; but not in C I 492, 806 GHz. This first measurement of the high-velocity 12CO rotational ladder toward Sgr A* adds more evidence that hot molecular gas exists inside the cavity of the CND, relatively close to the supermassive black hole (<1 pc). Observed by ALMA, this velocity range appears as a collection of 12CO (J = 3−2) cloudlets lying in a very harsh environment that is pervaded by intense UV radiation fields, shocks, and affected by strong gravitational shears. We constrain the physical conditions of the high positive-velocity CO gas component by comparing with non-LTE excitation and radiative transfer models. We infer Tk ≃ 400 K–2000 K for nH ≃ (0.2−1.0) × 105 cm−3. These results point toward the important role of stellar UV radiation, but we show that radiative heating alone cannot explain the excitation of this ~10−60 M⊙ component of hot molecular gas inside the central cavity. Instead, strongly irradiated shocks are promising candidates.
The Orion Molecular Cloud is the nearest massive-star forming region. Massive stars have profound effects on their environment due to their strong radiation fields and stellar winds. Stellar feedback ...is one of the most crucial cosmological parameters that determine the properties and evolution of the interstellar medium in galaxies.
We aim to understand the role that feedback by stellar winds and radiation play in the evolution of the interstellar medium. Velocity-resolved observations of the C
158
m fine-structure line allow us to study the kinematics of UV-illuminated gas. Here, we present a square-degree-sized map of C
emission from the Orion Nebula complex at a spatial resolution of 16″ and high spectral resolution of 0.2kms
, covering the entire Orion Nebula (M42) plus M43 and the nebulae NGC 1973, 1975, and 1977 to the north. We compare the stellar characteristics of these three regions with the kinematics of the expanding bubbles surrounding them.
We use C
158
m line observations over an area of 1.2deg
in the Orion Nebula complex obtained by the upGREAT instrument onboard SOFIA.
The bubble blown by the O7V star
Ori C in the Orion Nebula expands rapidly, at 13kms
. Simple analytical models reproduce the characteristics of the hot interior gas and the neutral shell of this wind-blown bubble and give us an estimate of the expansion time of 0.2 Myr. M43 with the B0.5V star NU Ori also exhibits an expanding bubble structure, with an expansion velocity of 6kms
. Comparison with analytical models for the pressure-driven expansion of H
regions gives an age estimate of 0.02 Myr. The bubble surrounding NGC 1973, 1975, and 1977 with the central B1V star 42 Orionis expands at 1.5kms
, likely due to the over-pressurized ionized gas as in the case of M43. We derive an age of 0.4 Myr for this structure.
We conclude that the bubble of the Orion Nebula is driven by the mechanical energy input by the strong stellar wind from
Ori C, while the bubbles associated with M43 and NGC 1977 are caused by the thermal expansion of the gas ionized by their central later-type massive stars.
A new Main-Belt Comet (MBC) P/2012 T1 (PANSTARRS) was discovered on 2012 October 6, approximately one month after its perihelion, by the Pan-STARRS1 survey based in Hawaii. It displayed cometary ...activity upon its discovery with one hypothesis being that the activity was driven by sublimation of ices; as a result, we searched for emission assumed to be driven by the sublimation of subsurface ices. Our search was of the H sub(2)O 1 sub(10)-1 sub(01) ground state rotational line at 557 GHz from P/2012 T1 (PANSTARRS) with the Heterodyne Instrument for the Far Infrared on board the Herschel Space Observatory on 2013 January 16, when the object was at a heliocentric distance of 2.504 AU and a geocentric distance of 2.064 AU. Perihelion was in early 2012 September at a distance of 2.411 AU. While no H sub(2)O line emission was detected in our observations, we were able to derive sensitive 3sigma upper limits for the water production rate and column density of <7.63 x 10 super(25) molecules s super(-1) and of <1.61 x 10 super(11) cm super(-2), respectively. An observation taken on 2013 January 15 using the Very Large Telescope found the MBC to be active during the Herschel observation, suggesting that any ongoing sublimation due to subsurface ice was lower than our upper limit.
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