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- ID:
- ivo://CDS.VizieR/J/A+A/607/A78
- Title:
- APEX and IRAM spectra of CK Vul (Nova 1670)
- Short Name:
- J/A+A/607/A78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CK Vulpeculae (CK Vul) is an enigmatic star whose outburst was observed in 1670-72. A stellar-merger event was proposed to explain its ancient eruption. We aim to investigate the composition of the molecular gas recently discovered in the remnant of CK Vul. Deriving the chemical, elemental, and isotopic composition is crucial for identifying the nature of the object and obtaining clues on its progenitor(s). We observed millimeter and submillimeter-wave spectra of CK Vul using the IRAM 30m and APEX telescopes. Radiative-transfer modeling of the observed molecular features was performed to yield isotopic ratios for various elements. The spectra of CK Vul reveal a very rich molecular environment of low excitation (T_ex_~<12K). Atomic carbon and twenty seven different molecules, including two ions, were identified. They range from simple diatomic to complex polyatomic species of up to seven atoms large. The chemical composition of the molecular gas is indicative of carbon and nitrogen-driven chemistry but oxides are also present. Additionally, the abundance of F may be enhanced. The spectra are rich in isotopologues that are very rare in most known sources. All stable isotopes of C, N, O, Si, and S are observed and their isotopic ratios are derived. The composition of the remnant's molecular gas is most peculiar and gives rise to a very unique millimeter and submillimeter spectrum. The observation of ions and complex molecules suggests the presence of a photoionizing source but its nature (a central star or shocks) remains unknown. The elemental and isotopic composition of the gas cannot be easily reconciled with standard nucleosynthesis but processing in hot CNO cycles and partial He burning can explain most of the chemical peculiarities. The isotopic ratios of CK Vul are remarkably close to those of presolar nova grains but the link of Nova 1670 to objects responsible for these grains is unclear.
1033. APEX-CHAMP^+^. II.
- ID:
- ivo://CDS.VizieR/J/A+A/507/1425
- Title:
- APEX-CHAMP^+^. II.
- Short Name:
- J/A+A/507/1425
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The origin and heating mechanisms of warm (50<T<200K) molecular gas in low-mass young stellar objects (YSOs) are strongly debated. Both passive heating of the inner collapsing envelope by the protostellar luminosity as well as active heating by shocks and by UV associated with the outflows or accretion have been proposed. Most data so far have focussed on the colder gas component. We aim to characterize the warm gas within protosteller objects, and disentangle contributions from the (inner) envelope, bipolar outflows and the quiescent cloud. ************************************************************************** * * * Sorry, but the author(s) never supplied the tabular material * * announced in the paper * * * **************************************************************************
- ID:
- ivo://CDS.VizieR/J/A+A/608/A102
- Title:
- APEX CO and HI observations of Lupus I
- Short Name:
- J/A+A/608/A102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Lupus I cloud is found between the Upper Scorpius (USco) and Upper Centaurus-Lupus (UCL) subgroups of the Scorpius-Centaurus OB association, where the expanding USco HI shell appears to interact with a bubble currently driven by the winds of the remaining B stars of UCL. Aims. We investigate whether the Lupus I molecular could have formed in a colliding flow, and in particular, how the kinematics of the cloud might have been influenced by the larger scale gas dynamics. We performed APEX ^13^CO(2-1)and C^18^O(2-1) line observations of three distinct parts of Lupus I that provide kinematic information on the cloud at high angular and spectral resolution. We compare those results to the atomic hydrogen data from the GASS HI survey and our dust emission results presented in the previous paper. Based on the velocity information, we present a geometric model for the interaction zone between the USco shell and the UCL wind bubble. We present evidence that the molecular gas of Lupus Iis tightly linked to the atomic material of the USco shell. The CO emission in Lupus Iis found mainly at velocities between v_LSR_=3-6km/s, which is in the same range as the HI velocities. Thus, the molecular cloud is co-moving with the expanding USco atomic HI shell. The gas in the cloud shows a complex kinematic structure with several line-of-sight components that overlay each other. The nonthermal velocity dispersion is in the transonic regime in all parts of the cloud and could be injected by external compression. Our observations and the derived geometric model agree with a scenario in which Lupus Iis located in the interaction zone between the USco shell and the UCL wind bubble. The kinematics observations are consistent with a scenario in which the Lupus Icloud formed via shell instabilities. The particular location of Lupus I between USco and UCL suggests that counterpressure from the UCL wind bubble and pre-existing density enhancements, perhaps left over from the gas stream that formed the stellar subgroups, may have played a role in its formation.
- ID:
- ivo://CDS.VizieR/J/ApJ/767/36
- Title:
- APEX observations of HOPS protostars
- Short Name:
- J/ApJ/767/36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform a census of the reddest, and potentially youngest, protostars in the Orion molecular clouds using data obtained with the PACS instrument on board the Herschel Space Observatory and the LABOCA and SABOCA instruments on APEX as part of the Herschel Orion Protostar Survey (HOPS). A total of 55 new protostar candidates are detected at 70{mu}m and 160{mu}m that are either too faint (m_24_>7mag) to be reliably classified as protostars or undetected in the Spitzer/MIPS 24{mu}m band. We find that the 11 reddest protostar candidates with log{lambda}F_{lambda}_70/{lambda}F_{lambda}_24>1.65 are free of contamination and can thus be reliably explained as protostars. The remaining 44 sources have less extreme 70/24 colors, fainter 70{mu}m fluxes, and higher levels of contamination. Taking the previously known sample of Spitzer protostars and the new sample together, we find 18 sources that have log{lambda}F_{lambda}_70/{lambda}F_{lambda}_24>1.65; we name these sources "PACS Bright Red sources," or PBRs. Our analysis reveals that the PBR sample is composed of Class 0 like sources characterized by very red spectral energy distributions (SEDs; T_bol_<45K) and large values of sub-millimeter fluxes (L_smm_/L_bol_>0.6%). Modified blackbody fits to the SEDs provide lower limits to the envelope masses of 0.2-2M_{sun}_ and luminosities of 0.7-10L_{sun}_. Based on these properties, and a comparison of the SEDs with radiative transfer models of protostars, we conclude that the PBRs are most likely extreme Class 0 objects distinguished by higher than typical envelope densities and hence, high mass infall rates.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A98
- Title:
- APEX spectra of Centaurus A
- Short Name:
- J/A+A/608/A98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 5128 (Centaurus A) is one of the best targets to study AGN feedback in the local Universe. At 13.5kpc from the galaxy, optical filaments with recent star formation lie along the radio jet direction. This region is a testbed for positive feedback, here through jet-induced star formation. Atacama Pathfinder EXperiment (APEX) observations have revealed strong CO emission in star-forming regions and in regions with no detected tracers of star formation activity. In cases where star formation is observed, this activity appears to be inefficient compared to the Kennicutt-Schmidt relation. We used the Atacama Large Millimeter/submillimeter Array (ALMA) to map the 12CO(1-0) emission all along the filaments of NGC 5128 at a resolution of 1.3"~23.8pc. We find that the CO emission is clumpy and is distributed in two main structures: (i) the Horseshoe complex, located outside the HI cloud, where gas is mostly excited by shocks and where no star formation is observed, and (ii) the Vertical filament, located at the edge of the HI shell, which is a region of moderate star formation. We identified 140 molecular clouds using a clustering method applied to the CO data cube. A statistical study reveals that these clouds have very similar physical properties, such as size, velocity dispersion, and mass, as in the inner Milky Way. However, the range of radius available with the present ALMA observations does not enable us to investigate whether or not the clouds follow the Larson relation. The large virial parameter {alpha}_vir_ of the clouds suggests that gravity is not dominant and clouds are not gravitationally unstable. Finally, the total energy injection in the northern filaments of Centaurus A is of the same order as in the inner part of the Milky Way. The strong CO emission detected in the northern filaments is an indication that the energy injected by the jet acts positively in the formation of dense molecular gas. The relatively high virial parameter of the molecular clouds suggests that the injected kinetic energy is too strong for star formation to be efficient. This is particularly the case in the Horseshoe complex, where the virial parameter is the largest and where strong CO is detected with no associated star formation. This is the first evidence of AGN positive feedback in the sense of forming molecular gas through shocks, associated with low star formation efficiency due to turbulence injection by the interaction with the radio jet.
- ID:
- ivo://CDS.VizieR/J/A+A/627/A6
- Title:
- APEX spectra of Centaurus A
- Short Name:
- J/A+A/627/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 5128 (Centaurus A) is one of the best targets to study AGN-feedback in the local Universe. Optical filaments located at 16 kpc from the galaxy along the radio jet direction show recent star formation, likely triggered by the interaction of the jet with an HI shell. A large reservoir of molecular gas has been discovered outside the HI. In this reservoir, lies the Horseshoe complex: a filamentary structure seen in CO with ALMA and in Halpha with MUSE. The ionised gas is mostly excited by shocks, with only a minor contribution of star formation. We used the Atacama Pathfinder EXperiment (APEX) to observe the ^12^CO(3-2) and ^12^CO(4-3) transitions, as well as dense gas tracers in the Horseshoe complex. ^12^CO(3-2) and ^12^CO(4-3) are detected for the first time in the northern filaments of Centaurus A, with integrated intensity line ratios R32~0.2 and R43~0.1, compared to the ^12^CO(1-0) emission. We also derived a line ratio R21~0.6, based on the previous ^12^CO(2-1) observations of Salome et al. (2016, Cat. J/A+A/595/A65). We used the non-LTE radiative transfer code RADEX and determined that the molecular gas in this region has a temperature of 55-70K and densities between 2-6x10^2^cm^-3^. Such densities are also in agreement with results from the Paris-Durham shock code that predicts a post-shock density of a few 100cm^-3^. However, we need more observations of emission lines at a better angular resolution in order to place tighter constraints on our radiative models, whether they are used as a stand-alone tool (LVG codes) or combined with a shock model.
- ID:
- ivo://CDS.VizieR/J/A+A/595/A65
- Title:
- APEX spectra of Centaurus A
- Short Name:
- J/A+A/595/A65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 5128 (Centaurus A) is one of the best example to study AGN-feedback in the local Universe. At 13.5kpc from the galaxy, optical filaments with recent star formation are lying along the radio-jet direction. We used the Atacama Pathfinder EXperiment (APEX) to map the CO(2-1) emission all along the filaments structure. Molecular gas mass of 8.2x10^7M_{sun}_ was found over the 4.2kpc-structure which represents about 3% of the total gas mass of the NGC 5128 cold gas content. Two dusty mostly molecular structures are identified, following the optical filaments. The region corresponds to the crossing of the radio jet with the northern HI shell, coming from a past galaxy merger. One filament is located at the border of the HI shell, while the other is entirely molecular, and devoid of HI gas. The molecular mass is comparable to the HI mass in the shell, suggesting a scenario where the atomic gas was shocked and transformed in molecular clouds by the radio jet. Comparison with combined FIR Herschel and UV GALEX estimation of star formation rates in the same regions leads to depletion times of more than 10 Gyr. The filaments are thus less efficient than discs in converting molecular gas into stars. Kinetic energy injection triggered by shocks all along the jet/gas interface is a possible process that appears to be consistent with MUSE line ratio diagnostics derived in a smaller region of the northern filaments. Whether the AGN is the sole origin of this energy input and what is the dominant (mechanical vs radiative) mode for this process is however still to be investigated.
- ID:
- ivo://CDS.VizieR/J/A+A/570/A49
- Title:
- APEX spectra of massive YSOs
- Short Name:
- J/A+A/570/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Molecular outflows are a direct consequence of accretion, and therefore they represent one of the best tracers of accretion processes in the still poorly understood early phases of high-mass star formation. Previous studies suggested that the SiO abundance decreases with the evolution of a massive young stellar object probably because of a decay of jet activity, as witnessed in low-mass star-forming regions. We investigate the SiO excitation conditions and its abundance in outflows from a sample of massive young stellar objects through observations of the SiO(8-7) and CO(4-3) lines with the APEX telescope.
- ID:
- ivo://CDS.VizieR/J/A+A/615/A8
- Title:
- APEX spectrum of R Dor (159.0-368.5GHz)
- Short Name:
- J/A+A/615/A8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our current insights into the circumstellar chemistry of asymptotic giant branch (AGB) stars are largely based on studies of carbon-rich stars and stars with high mass-loss rates. In order to expand the current molecular inventory of evolved stars we present a spectral scan of the nearby, oxygen-rich star R Dor, a star with a low mass-loss rate (~2x10^-7^M_{sun}_/yr). We carried out a spectral scan in the frequency ranges 159.0-321.5GHz and 338.5-368.5GHz (wavelength range 0.8-1.9mm) using the SEPIA/Band-5 and SHeFI instruments on the APEX telescope and we compare it to previous surveys, including one of the oxygen-rich AGB star IK Tau, which has a high mass-loss rate (~5x10^-6^M_{sun}_/yr). The spectrum of R Dor is dominated by emission lines of SO_2_ and the different isotopologues of SiO. We also detect CO, H_2_O, HCN, CN, PO, PN, SO, and tentatively TiO_2_, AlO, and NaCl. Sixteen out of approximately 320 spectral features remain unidentified. Among these is a strong but previously unknown maser at 354.2GHz, which we suggest could pertain to H_2_SiO, silanone. With the exception of one, none of these unidentified lines are found in a similarly sensitive survey of IK Tau performed with the IRAM 30 m telescope. We present radiative transfer models for five isotopologues of SiO (^28^SiO, ^29^SiO, ^30^SiO, Si^17^O, Si^18^O), providing constraints on their fractional abundance and radial extent. We derive isotopic ratios for C, O, Si, and S and estimate that, based on our results for ^17^O/^18^O, R Dor likely had an initial mass in the range 1.3-1.6M_{sun}_, in agreement with earlier findings based on models of H_2_O line emission. From the presence of spectral features recurring in many of the measured thermal and maser emission lines we tentatively identify up to five kinematical components in the outflow of R Dor, indicating deviations from a smooth, spherical wind.
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