| 1. |
- Decin, L., et al.
(författare)
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Warm water vapour in the sooty outflow from a luminous carbon star
- 2010
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 467:7311, s. 64-67
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Tidskriftsartikel (refereegranskat)abstract
- The detection(1) of circumstellar water vapour around the ageing carbon star IRC + 10216 challenged the current understanding of chemistry in old stars, because water was predicted(2) to be almost absent in carbon-rich stars. Several explanations for the water were postulated, including the vaporization of icy bodies (comets or dwarf planets) in orbit around the star(1), grain surface reactions(3), and photochemistry in the outer circumstellar envelope(4). With a single water line detected so far from this one carbon-rich evolved star, it is difficult to discriminate between the different mechanisms proposed. Here we report the detection of dozens of water vapour lines in the far-infrared and sub-millimetre spectrum of IRC + 10216 using the Herschel satellite(5). This includes some high-excitation lines with energies corresponding to similar to 1,000 K, which can be explained only if water is present in the warm inner sooty region of the envelope. A plausible explanation for the warm water appears to be the penetration of ultraviolet photons deep into a clumpy circumstellar envelope. This mechanism also triggers the formation of other molecules, such as ammonia, whose observed abundances(6) are much higher than hitherto predicted(7).
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| 2. |
- Muller, Sebastien, 1976, et al.
(författare)
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An ALMA Early Science survey of molecular absorption lines toward PKS 1830-211 Analysis of the absorption profiles
- 2014
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 566
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Tidskriftsartikel (refereegranskat)abstract
- We present the first results of an ALMA spectral survey of strong absorption lines for common interstellar species in the z = 0.89 molecular absorber toward the lensed blazar PKS 1830-211. The dataset brings essential information on the structure and composition of the absorbing gas in the foreground galaxy. In particular, we find absorption over large velocity intervals (greater than or similar to 100 km s(-1)) toward both lensed images of the blazar. This suggests either that the galaxy inclination is intermediate and that we sample velocity gradients or streaming motions in the disk plane, that the molecular gas has a large vertical distribution or extraplanar components, or that the absorber is not a simple spiral galaxy but might be a merger system. The number of detected species is now reaching a total of 42 different species plus 14 different rare isotopologues toward the SW image, and 14 species toward the NE line-of-sight. The abundances of CH, H2O, HCO+, HCN, and NH3 relative to H-2 are found to be comparable to those in the Galactic diffuse medium. Of all the lines detected so far toward PKS 1830-211, the ground-state line of ortho-water has the deepest absorption. We argue that ground-state lines of water have the best potential for detecting diffuse molecular gas in absorption at high redshift.
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| 3. |
- Yang, C., et al.
(författare)
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Submillimeter H 2 O and H 2 O + emission in lensed ultra- and hyper-luminous infrared galaxies at z ~ 2-4
- 2016
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 595, s. Art no A80-
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Tidskriftsartikel (refereegranskat)abstract
- We report rest-frame submillimeter H2O emission line observations of 11 ultra- or hyper-luminous infrared galaxies (ULIRGs or HyLIRGs) at z ∼ 2-4 selected among the brightest lensed galaxies discovered in the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS). Using the IRAM NOrthern Extended Millimeter Array (NOEMA), we have detected 14 new H2O emission lines. These include five 321-312 ortho-H2O lines (Eup/k = 305 K) and nine J = 2 para-H2O lines, either 202-111 (Eup/k = 101 K) or 211-202 (Eup/k = 137 K). The apparent luminosities of the H2O emission lines are μLH2O ∼ 6-21 × 108 L⊙ (3 > μ > 15, where μ is the lens magnification factor), with velocity-integrated line fluxes ranging from 4-15 Jy km s-1. We have also observed CO emission lines using EMIR on the IRAM 30 m telescope in seven sources (most of those have not yet had their CO emission lines observed). The velocity widths for CO and H2O lines are found to be similar, generally within 1σ errors in the same source. With almost comparable integrated flux densities to those of the high-J CO line (ratios range from 0.4 to 1.1), H2O is found to be among the strongest molecular emitters in high-redshift Hy/ULIRGs. We also confirm our previously found correlation between luminosity of H2O(LH2O) and infrared (LIR) that LH2O ∼ LIR1:1-1:2, with our new detections. This correlation could be explained by a dominant role of far-infrared pumping in the H2O excitation. Modelling reveals that the far-infrared radiation fields have warm dust temperature Twarm ∼ 45-75 K, H2O column density per unit velocity interval NH2O/ΔV ≳ 0:3 × 1015 cm-2 km-1 s and 100 μm continuum opacity τ100 1 (optically thick), indicating that H2O is likely to trace highly obscured warm dense gas. However, further observations of J ≥ 4 H2O lines are needed to better constrain the continuum optical depth and other physical conditions of the molecular gas and dust. We have also detected H2O+ emission in three sources. A tight correlation between LH2O and LH2O+ has been found in galaxies from low to high redshift. The velocity-integrated flux density ratio between H2O+ and H2O suggests that cosmic rays generated by strong star formation are possibly driving the H2O+ formation. © 2016 ESO.
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| 4. |
- Cernicharo, J., et al.
(författare)
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Discovery of time variation of the intensity of molecular lines in IRC+10216 in the submillimeter and far-infrared domains
- 2014
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 796:1
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Tidskriftsartikel (refereegranskat)abstract
- We report on the discovery of strong intensity variations in the high rotational lines of abundant molecular species toward the archetypical circumstellar envelope of IRC+10216. The observations have been carried out with the Heterodyne Instrument for the Far-Infrared (HIFI) instrument on board Herschel and with the IRAM30 m telescope. They cover several observing periods spreading over three years. The line intensity variations for molecules produced in the external layers of the envelope most likely result from time variations in the infrared pumping rates. We analyze the main implications this discovery has on the interpretation of molecular line emission in the envelopes of Mira-type stars. Radiative transfer calculations must take into account both the time variability of infrared pumping and the possible variation of the dust and gas temperatures with stellar phase in order to reproduce the observation of molecular lines at different epochs. The effect of gas temperature variations with stellar phase could be particularly important for lines produced in the innermost regions of the envelope. Each layer of the circumstellar envelope sees the stellar light radiation with a different lag time (phase). Our results show that this effect must be included in the models. The submillimeter and far infrared lines of asymptotic giant branch stars can no longer be considered as safe intensity calibrators.
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| 5. |
- Marti-Vidal, Ivan, 1980, et al.
(författare)
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Probing the jet base of the blazar PKS 1830-211 from the chromatic variability of its lensed images. Serendipitous ALMA observations of a strong gamma-ray flare
- 2013
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 558, s. 123-
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Tidskriftsartikel (refereegranskat)abstract
- The launching mechanism of the jets of active galactic nuclei is poorly constrained observationally, owing to the large distances to these objects and the very small scales (sub-parsec) involved. To better constrain theoretical models, it is especially important to get information from the region close to the physical base of the jet, where the plasma acceleration takes place. In this paper, we report multi-epoch and multifrequency continuum observations of the z = 2.5 blazar PKS 1830−211 with ALMA, serendipitously coincident with a strong γ-ray flare reported by Fermi-LAT. The blazar is lensed by a foreground z = 0.89 galaxy, with two bright images of the compact core separated by 1′′. Our ALMA observations individually resolve these two images (although not any of their substructures), and we study the change in their relative flux ratio with time (four epochs spread over nearly three times the time delay between the two lensed images) and frequency (between 350 and 1050 GHz, rest frame of the blazar), during the γ-ray flare. In particular, we detect a remarkable frequency-dependent behavior of the flux ratio, which implies the presence of a chromatic structure in the blazar (i.e., a core-shift effect). We rule out the possibility of micro- and milli-lensing effects and propose instead a simple model of plasmon ejection in the blazar’s jet to explain the time and frequency variability of the flux ratio. We suggest that PKS 1830−211 is likely to be one of the best sources to probe the activity at the base of a blazar’s jet at submillimeter wavelengths, thanks to the peculiar geometry of the system. The implications of the core shift in absorption studies of the foreground z = 0.89 galaxy (e.g., constraints on the cosmological variations of fundamental constants) are discussed.
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| 6. |
- Muller, Sebastien, 1976, et al.
(författare)
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Detection of CH+, SH+, and their C-13- and S-34-isotopologues toward PKS 1830-211
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 606
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Tidskriftsartikel (refereegranskat)abstract
- The z = 0.89 molecular absorber toward PKS 1830-211 provides us with the opportunity to probe the chemical and physical properties of the interstellar medium in the disk of a galaxy at a look-back time of half the present age of the Universe. Recent ALMA observations of hydrides have unveiled the multi-phase composition of this source's interstellar medium along two absorbing sightlines. Here, we report ALMA observations of CH+ and SH+, and of their C-13- and S-34-isotopologues, as potential tracers of energetic processes in the interstellar medium. CH+ and (CH+)-C-13 are detected toward both images of PKS 1830-211, CH+ showing the deepest and broadest absorption among all species observed so far. The [CH+]/[(CH+)-C-13] abundance ratio is similar to 100 in the south-west line of sight. This value is larger than any previous [(CX)-C-12]/[(CX)-C-13] ratios determined from other species toward this source and suggests either that the latter might be affected by fractionation or that CH+ might be tracing a different gas component. Toward the north-east image, we find an even larger value of [CH+]/[(CH+)-C-13], 146 +/- 43, although with a large uncertainty. This sightline intercepts the absorber at a larger galactocentric radius than the southwestern one, where material might be less processed in stellar nucleosynthesis. In contrast to CH+ and its C-13 isotopologue, SH+ and (SH+)-S-34 are only detected on the south-west sightline. These are the first detections of extragalactic SH+ and interstellar (SH+)-S-34. The spectroscopic parameters of SH+ are reevaluated and improved rest frequencies of (SH+)-S-34 are obtained. The [CH+]/[SH+] column density ratios show a large difference between the two lines of sight: similar to 25 and > 600 toward the SW and NE image, respectively. We are not able to shed light on the formation process of CH+ and SH+ with these data, but the differences between the two sightlines toward PKS 1830-211 suggest that their absorptions arise from gas with a molecular fraction of greater than or similar to 10%, with SH+ tracing significantly higher molecular fractions than CH+.
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| 7. |
- Muller, Sebastien, 1976, et al.
(författare)
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Detection of chloronium and measurement of the Cl-35/Cl-37 isotopic ratio at z=0.89 toward PKS 1830-211
- 2014
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 566
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Tidskriftsartikel (refereegranskat)abstract
- We report the first extragalactic detection of chloronium (H2Cl+) in the z = 0.89 absorber in front of the lensed blazar PKS 1830-211. The ion is detected through its 1(11)-0(00) line along two independent lines of sight toward the North-East and South-West images of the blazar. The relative abundance of H2Cl+ is significantly higher (by a factor similar to 7) in the NE line of sight, which has a lower H-2/H fraction, indicating that H2Cl+ preferably traces the diffuse gas component. From the ratio of the (H2Cl+)-Cl-35 and (H2Cl+)-Cl-37 absorptions toward the SW image, we measure a Cl-35/Cl-37 isotopic ratio of 3.1(-0.2)(+0.3) at z = 0.89, similar to that observed in the Galaxy and the solar system.
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| 8. |
- Muller, Sebastien, 1976, et al.
(författare)
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OH+ and H2O+ absorption toward PKS 1830-211
- 2016
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 595, s. A128(1-10)
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Tidskriftsartikel (refereegranskat)abstract
- We report the detection of OH+ and H2O+ in the z = 0.89 absorber toward the lensed quasar PKS 1830-211. The abundance ratio of OH+ and H2O+ is used to quantify the molecular hydrogen fraction (fH2) and the cosmic-ray ionization rate of atomic hydrogen (ζH) along two lines of sight, located at 2 kpc and 4 kpc to either side of the absorber's center. The molecular fraction decreases outward, from 0.04 to 0.02, comparable to values measured in the Milky Way at similar galactocentric radii. For ζH , we find values of 2 × 10-14 s-1 and 3 × 10-15 s-1, respectively, which are slightly higher than in the Milky Way at comparable galactocentric radii, possibly due to a higher average star formation activity in the z = 0.89 absorber. The ALMA observations of OH+, H2O+, and other hydrides toward PKS 1830-211reveal the multi-phase composition of the absorbing gas. Taking the column density ratios along the southwest and northeast lines of sight as a proxy of molecular fraction, we classify the species ArH+, OH+, H2Cl+, H2O+, CH, and HF as tracing gases increasingly more molecular. Incidentally, our data allow us to improve the accuracy of H2O+ rest frequencies and thus refine the spectroscopic parameters.
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| 9. |
- Muller, Sebastien, 1976, et al.
(författare)
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Detection of deuterated molecules, but not of lithium hydride, in the z=0.89 absorber toward PKS 1830-211
- 2020
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 637
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Tidskriftsartikel (refereegranskat)abstract
- Deuterium and lithium are light elements of high cosmological and astrophysical importance. In this work we report the first detection of deuterated molecules and a search for lithium hydride, (LiH)-Li-7, at redshift z=0.89 in the spiral galaxy intercepting the line of sight to the quasar PKS 1830-211. We used ALMA to observe several submillimeter lines of ND, NH2D, and HDO, and their related isotopomers NH2, NH3, and (H2O)-O-18 H 2 18 O , in absorption against the southwest image of the quasar, allowing us to derive XD/XH abundance ratios. The absorption spectra mainly consist of two distinct narrow velocity components for which we find remarkable differences. One velocity component shows XD/XH abundances that is about 10 times larger than the primordial elemental D/H ratio, and no variability of the absorption profile during the time span of our observations. In contrast, the other component shows a stronger deuterium fractionation. Compared to the first component, this second component has XD/XH abundances that are 100 times larger than the primordial D/H ratio, a deepening of the absorption by a factor of two within a few months, and a rich chemical composition, with relative enhancements of N2H+, CH3OH, SO2 and complex organic molecules. We therefore speculate that this component is associated with the analog of a Galactic dark cloud, while the first component is likely more diffuse. Our search for the (LiH)-Li-7 (1-0) line was unsuccessful and we derive an upper limit (LiH)-Li-7/H-2 = 4x10(-13) (3 sigma) in the z=0.89 absorber toward PKS 1830-211. Besides, with ALMA archival data, we could not confirm the previous tentative detections of this line in the z=0.68 absorber toward B 0218+357; we derive an upper limit (LiH)-Li-7/H-2 = 5x10(-11) (3 sigma), although this is less constraining than our limit toward PKS 1830-211. We conclude that, as in the Milky Way, only a tiny fraction of lithium nuclei are possibly bound in LiH in these absorbers at intermediate redshift.
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| 10. |
- Cernicharo, J., et al.
(författare)
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Discovery of the first Ca-bearing molecule in space: CaNC
- 2019
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 627
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Tidskriftsartikel (refereegranskat)abstract
- We report on the detection of calcium isocyanide, CaNC, in the carbon-rich evolved star IRC + 10216. We derived a column density for this species of (2 +/- 0.5) x 10(11) cm(-2). Based on the observed line profiles and the modelling of its emission through the envelope, the molecule has to be produced in the intermediate and outer layers of the circumstellar envelope where other metal-isocyanides have previously been found in this source. The abundance ratio of CaNC relative to MgNC and FeCN is congruent to 1/60 and congruent to 1, respectively. We searched for the species CaF, CaCl, CaC, CaCCH, and CaCH3 for which accurate frequency predictions are available. Only upper limits have been obtained for these molecules.
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