Water In Star-forming regions with Herschel (WISH) is a key program on the Herschel Space Observatory designed to probe the physical and chemical structures of young stellar objects using water and ...related molecules and to follow the water abundance from collapsing clouds to planet-forming disks. About 80 sources are targeted, covering a wide range of luminosities-from low (< 1) to high (>10)-and a wide range of evolutionary stages-from cold prestellar cores to warm protostellar envelopes and outflows to disks around young stars. Both the HIFI and PACS instruments are used to observe a variety of lines of HO , HO and chemically related species at the source position and in small maps around the protostars and selected outflow positions. In addition, high-frequency lines of CO, CO , and CO are obtained with Herschel and are complemented by ground-based observations of dust continuum, HDO, CO and its isotopologs, and other molecules to ensure a self-consistent data set for analysis. An overview of the scientific motivation and observational strategy of the program is given, together with the modeling approach and analysis tools that have been developed. Initial science results are presented. These include a lack of water in cold gas at abundances that are lower than most predictions, strong water emission from shocks in protostellar environments, the importance of UV radiation in heating the gas along outflow walls across the full range of luminosities, and surprisingly widespread detection of the chemically related hydrides OH and HO in outflows and foreground gas. Quantitative estimates of the energy budget indicate that HO is generally not the dominant coolant in the warm dense gas associated with protostars. Very deep limits on the cold gaseous water reservoir in the outer regions of protoplanetary disks are obtained that have profound implications for our understanding of grain growth and mixing in disks.
Aims. This paper describes the Heterodyne Instrument for the Far-Infrared (HIFI) that was launched onboard ESA's Herschel Space Observatory in May 2009. Methods. The instrument is a set of 7 ...heterodyne receivers that are electronically tuneable, covering 480–1250 GHz with SIS mixers and the 1410–1910 GHz range with hot electron bolometer (HEB) mixers. The local oscillator (LO) subsystem comprises a Ka-band synthesizer followed by 14 chains of frequency multipliers and 2 chains for each frequency band. A pair of auto-correlators and a pair of acousto-optical spectrometers process the two IF signals from the dual-polarization, single-pixel front-ends to provide instantaneous frequency coverage of 2 × 4 GHz, with a set of resolutions (125 kHz to 1 MHz) that are better than 0.1 km s-1. Results. After a successful qualification and a pre-launch TB/TV test program, the flight instrument is now in-orbit and completed successfully the commissioning and performance verification phase. The in-orbit performance of the receivers matches the pre-launch sensitivities. We also report on the in-orbit performance of the receivers and some first results of HIFI's operations.
Context.
Water is a key molecule in the physics and chemistry of star and planet formation, but it is difficult to observe from Earth. The
Herschel
Space Observatory provided unprecedented ...sensitivity as well as spatial and spectral resolution to study water. The Water In Star-forming regions with
Herschel
(WISH) key program was designed to observe water in a wide range of environments and provide a legacy data set to address its physics and chemistry.
Aims.
The aim of WISH is to determine which physical components are traced by the gas-phase water lines observed with
Herschel
and to quantify the excitation conditions and water abundances in each of these components. This then provides insight into how and where the bulk of the water is formed in space and how it is transported from clouds to disks, and ultimately comets and planets.
Methods.
Data and results from WISH are summarized together with those from related open time programs. WISH targeted ~80 sources along the two axes of luminosity and evolutionary stage: from low- to high-mass protostars (luminosities from <1 to > 10
5
L
⊙
) and from pre-stellar cores to protoplanetary disks. Lines of H
2
O and its isotopologs, HDO, OH, CO, and O I, were observed with the HIFI and PACS instruments, complemented by other chemically-related molecules that are probes of ultraviolet, X-ray, or grain chemistry. The analysis consists of coupling the physical structure of the sources with simple chemical networks and using non-LTE radiative transfer calculations to directly compare models and observations.
Results.
Most of the far-infrared water emission observed with
Herschel
in star-forming regions originates from warm outflowing and shocked gas at a high density and temperature (> 10
5
cm
−3
, 300–1000 K,
v
~ 25 km s
−1
), heated by kinetic energy dissipation. This gas is not probed by single-dish low-
J
CO lines, but only by CO lines with
J
up
> 14. The emission is compact, with at least two different types of velocity components seen. Water is a significant, but not dominant, coolant of warm gas in the earliest protostellar stages. The warm gas water abundance is universally low: orders of magnitude below the H
2
O/H
2
abundance of 4 × 10
−4
expected if all volatile oxygen is locked in water. In cold pre-stellar cores and outer protostellar envelopes, the water abundance structure is uniquely probed on scales much smaller than the beam through velocity-resolved line profiles. The inferred gaseous water abundance decreases with depth into the cloud with an enhanced layer at the edge due to photodesorption of water ice. All of these conclusions hold irrespective of protostellar luminosity. For low-mass protostars, a constant gaseous HDO/H
2
O ratio of ~0.025 with position into the cold envelope is found. This value is representative of the outermost photodesorbed ice layers and cold gas-phase chemistry, and much higher than that of bulk ice. In contrast, the gas-phase NH
3
abundance stays constant as a function of position in low-mass pre- and protostellar cores. Water abundances in the inner hot cores are high, but with variations from 5 × 10
−6
to a few × 10
−4
for low- and high-mass sources. Water vapor emission from both young and mature disks is weak.
Conclusions.
The main chemical pathways of water at each of the star-formation stages have been identified and quantified. Low warm water abundances can be explained with shock models that include UV radiation to dissociate water and modify the shock structure. UV fields up to 10
2
−10
3
times the general interstellar radiation field are inferred in the outflow cavity walls on scales of the
Herschel
beam from various hydrides. Both high temperature chemistry and ice sputtering contribute to the gaseous water abundance at low velocities, with only gas-phase (re-)formation producing water at high velocities. Combined analyses of water gas and ice show that up to 50% of the oxygen budget may be missing. In cold clouds, an elegant solution is that this apparently missing oxygen is locked up in larger
μ
m-sized grains that do not contribute to infrared ice absorption. The fact that even warm outflows and hot cores do not show H
2
O at full oxygen abundance points to an unidentified refractory component, which is also found in diffuse clouds. The weak water vapor emission from disks indicates that water ice is locked up in larger pebbles early on in the embedded Class I stage and that these pebbles have settled and drifted inward by the Class II stage. Water is transported from clouds to disks mostly as ice, with no evidence for strong accretion shocks. Even at abundances that are somewhat lower than expected, many oceans of water are likely present in planet-forming regions. Based on the lessons for galactic protostars, the low-
J
H
2
O line emission (
E
up
< 300 K) observed in extragalactic sources is inferred to be predominantly collisionally excited and to originate mostly from compact regions of current star formation activity. Recommendations for future mid- to far-infrared missions are made.
The HIFI spectral survey of AFGL 2591 (CHESS) Kazmierczak-Barthel, M; van der Tak, F F S; Helmich, F P ...
Astronomy and astrophysics (Berlin),
07/2014, Letnik:
567
Journal Article
Recenzirano
Odprti dostop
Aims. This paper presents the richness of submillimeter spectral features in the high-mass star forming region AFGL 2591. Methods. As part of the Chemical Herschel Survey of Star Forming Regions ...(CHESS) key programme, AFGL 2591 was observed by the Herschel (HIFI) instrument. The spectral survey covered a frequency range from 480 to 1240GHz as well as single lines from 1267 to 1901GHz (i.e. CO, HCl, NH sub(3), 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. Results. From the HIFI spectral survey analysis a total of 32 species were Identified (including isotopologues). Although the lines quite mostly (integraloperatorT sub(mb)dV ~ few K kms super(-1)), 268 emission and 16 absorption lines were found (excluding blends). Molecular column densities range from 6 x 10 super(11) to 1 cm super(-2) 10 super(19) cm super(-2) and excitation temperatures from 19 to 175 K. Cold (e.g. HCN, H sub(2)S, and NH sub(3) with temperatures below 70 K) and warm species (e.g. CH sub(3)OH, SO sub(2)) in the protostellar envelope can be distinguished.
We present high-resolution HIFI spectroscopy of the nucleus of the archetypical starburst galaxy M 82. Six 12CO lines, 2 13CO lines and 4 fine-structure lines have been detected. Besides showing the ...effects of the overall velocity structure of the nuclear region, the line profiles also indicate the presence of multiple components with different optical depths, temperatures, and densities in the observing beam. The data have been interpreted using a grid of PDR models. It is found that the majority of the molecular gas is in low density (n = 103.5 cm-3) clouds, with column densities of NH = 1021.5 cm-2 and a relatively low UV radiation field (G0 = 102). The remaining gas is predominantly found in clouds with higher densities (n = 105 cm-3) and radiation fields (G0 = 102.75), but somewhat lower column densities (NH = 1021.2 cm-2). The highest J CO lines are dominated by a small (1% relative surface filling) component, with an even higher density (n = 106 cm-3) and UV field (G0 = 103.25). These results show the strength of multi-component modelling for interpretating the integrated properties of galaxies.
We present IRAM 30 m and JCMT observations of HDO lines towards the solar-type protostar IRAS 16293-2422. Five HDO transitions have been detected on-source, and two were unfruitfully searched for ...towards a bright spot of the outflow of IRAS 16293-2422. We interpret the data by means of the Ceccarelli et al. (1996) model, and derive the HDO abundance in the warm inner and cold outer parts of the envelope. The emission is well explained by a jump model, with an inner abundance x sub(in) super(HDO) 1 x 10 super(-7) and an outer abundance x sub(out) super(HDO) less than or equal to 1 x 10 super(-9) (3 sigma ). This result is in favor of HDO enhancement due to ice evaporation from the grains in the inner envelope. The deuteration ratio HDO/H sub(2)O is found to be f sub(in) = 3% and f sub(out) less than or equal to 0.2% (3 sigma ) in the inner and outer envelope respectively and therefore, the fractionation also undergoes a jump in the inner part of the envelope. These results are consistent with the formation of water in the gas phase during the cold prestellar core phase and storage of the molecules on the grains, but do not explain why observations of H sub(2)O ices consistently derive a H sub(2)O ice abundance of several 10 super(-5) to 10 super(-4), some two orders of magnitude larger than the gas phase abundance of water in the hot core around IRAS 16293-2422.
An 83-year old woman had been treated with bendamustin and rituximab for prolymphocytic leukemia. Two weeks after cycle 6 of chemotherapy, signs and symptoms of a severe hepatitis occurred.
Highly ...elevated values for AST (1353 U/l) and bilirubin (27.8 mg/dl), impaired coagulation parameters (INR 1,68) and the detection of ascites led to the diagnosis of an impending liver failure induced by reactivation of a hitherto unknown hepatitis B (HBs antigen pos., HBe antigen pos., anti HBc IgG pos., HBV DNA 1,65 Mio copies/ml).
After an immediately started treatment with entecavir (0.5 mg/d po), symptoms and laboratory parameters rapidly improved. 4 months later liver chemistry was completely normal and HBV DNA was negative. After 8 months, a seroconversion to anti HBs was noted.
In single cases, life threatening complications of chemotherapy induced reactivation of hepatitis B may be successfully treated by potent and stabile nucleosidanalogs.
The modelling of infrared dark cloud cores Ormel, C. W.; Shipman, R. F.; Ossenkopf, V. ...
Astronomy and astrophysics (Berlin),
08/2005, Letnik:
439, Številka:
2
Journal Article
Recenzirano
Odprti dostop
This paper presents results from modelling $450~ \mu{\rm m}$ and $850~ \mu{\rm m}$ continuum and $\element+{HCO}$ line observations of three distinct cores of an infrared dark cloud (IRDC) directed ...toward the W51 GMC. In the sub-mm continuum these cores appear as bright, isolated emission features. One of them coincides with the peak of $8.3~ \mu{\rm m}$ extinction as measured by the Midcourse Space Experiment satellite. Detailed radiative transfer codes are applied to constrain the cores' physical conditions to address the key question: Do these IRDC-cores harbour luminous sources? The results of the continuum model, expressed in the $\chi^2$ quality-of-fit parameter, are also constrained by the absence of $100~ \mu{\rm m}$ emission from IRAS. For the sub-mm emission peaks this shows that sources of ∼$300~{L}_{\odot}$ are embedded within the cores. For the extinction peak, the combination of continuum and $\element+{HCO}$ line modelling indicates that a heating source is present as well. Furthermore, the line model provides constraints on the clumpiness of the medium. All three cores have similar masses of about $70{-}150~{M}_{\odot}$ and similar density structures. The extinction peak differs from the other two cores by hosting a much weaker heating source, and the sub-mm emission core at the edge of the IRDC deviates from the other cores by a higher internal clumpiness.
Detection of Interstellar CH3 Feuchtgruber, H; Helmich, F. P; van Dishoeck, E. F ...
The Astrophysical journal,
06/2000, Letnik:
535, Številka:
2
Journal Article
Recenzirano
Observations with the Short Wavelength Spectrometer on board the Infrared Space Observatory have led to the first detection of the methyl radical CH(3) in the interstellar medium. The nu(2) Q-branch ...at 16.5 µm and the R(0) line at 16.0 µm have been unambiguously detected toward the Galactic center Sagittarius A*. The analysis of the measured bands gives a column density of 8.0+/-2.4 x1014 cm(-2) and an excitation temperature of 17+/-2 K. Gaseous CO at a similarly low excitation temperature and C(2)H(2) are detected for the same line of sight. Using constraints on the H(2) column density obtained from C(18)O and visual extinction, the inferred CH(3) abundance is 1.3+2.2-0.7 x10-8. The chemically related CH(4) molecule is not detected, but the pure rotational lines of CH are seen with the Long Wavelength Spectrometer. The absolute abundances and the CH(3)/CH(4) and CH(3)/CH 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 H with polycyclic aromatic hydrocarbons and solid aliphatic material are included.
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