FLASH$^{+}$—A Dual-Channel Wide-Band Spectrometer for APEX

Klein, Thomas; Ciechanowicz, Mirosław; Leinz, C.; Heyminck, S.; Güsten, R.; Kasemann, C.; Wunsch, J.; Maier, D.; Sekímoto, Yutaro

doi:10.1109/tthz.2014.2342498

Cited by 58 publications

(54 citation statements)

References 3 publications

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“…+ (Klein et al 2014) heterodyne receiver on the APEX 12 m telescope was used to observe the ATLASGAL TOP100 sample in CH 3 , and CH 3 OH (7-6) on June 15th and 24th, August 11th, 23rd, 24th and 26th 2011. The observations were performed in position switching mode with reference positions offset from the central position of the sources by (600 ,0 ).…”

Section: The Flashmentioning

confidence: 99%

ATLASGAL-selected massive clumps in the inner Galaxy

Giannetti

Leurini

Wyrowski

et al. 2017

A&A

171

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Context. Observational identification of a solid evolutionary sequence for high-mass star-forming regions is still missing. Spectroscopic observations give the opportunity to test possible schemes and connect the phases identified to physical processes. Aims. We aim to use the progressive heating of the gas caused by the feedback of high-mass young stellar objects to prove the statistical validity of the most common schemes used to observationally define an evolutionary sequence for high-mass clumps, and characterise the sensitivity of different tracers to this process. Methods. From the spectroscopic follow-ups carried out towards submillimeter continuum (dust) emission-selected massive clumps (the ATLASGAL TOP100 sample) with the IRAM 30 m, Mopra, and APEX telescopes between 84 GHz and 365 GHz, we selected several multiplets of CH 3 CN, CH 3 CCH, and CH 3 OH emission lines to derive and compare the physical properties of the gas in the clumps along the evolutionary sequence, fitting simultaneously the large number of lines that these molecules have in the observed band. Our findings are compared with results obtained from optically thin CO isotopologues, dust, and ammonia from previous studies on the same sample. Results. The chemical properties of each species have a major role on the measured physical properties. Low temperatures are traced by ammonia, methanol, and CO (in the early phases), the warm and dense envelope can be probed with CH 3 CN, CH 3 CCH, and, in evolved sources where CO is abundant in the gas phase, via its optically thin isotopologues. CH 3 OH and CH 3 CN are also abundant in the hot cores, and we suggest that their high-excitation transitions are good tools to study the kinematics in the hot gas associated with the inner envelope surrounding the young stellar objects that these clumps are hosting. All tracers show, to different degrees according to their properties, progressive warming with evolution. The relation between gas temperature and the luminosity-to-mass (L/M) ratio is reproduced by a simple toy model of a spherical, internally heated clump. Hii regions become common, showing that dissipation of the parental clump dominates.

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Section: The Flashmentioning

confidence: 99%

ATLASGAL-selected massive clumps in the inner Galaxy

Giannetti

Leurini

Wyrowski

et al. 2017

A&A

171

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“…ortho para para ortho meta para ortho ortho ortho para ortho para Klein et al 2014), operates simultaneously in the 345 GHz and the 460 GHz atmospheric windows, and it can record two 4 GHz wide sidebands separated by 12 GHz in both windows, i.e., altogether 4 × 4 GHz frequency bands. The receivers were connected to MPIfR Fast Fourier Transform Spectrometers (XFTTS, Klein et al 2012) with spectral resolutions of ∼ 0.03 and ∼ 0.05 km s −1 at 345 and 460 GHz, respectively.…”

Section: Apex Observationsmentioning

confidence: 99%

Deuteration of ammonia in the starless core Ophiuchus/H-MM1

Harju

Daniel

Sipilä

et al. 2017

A&A

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Context. Ammonia and its deuterated isotopologues probe physical conditions in dense molecular cloud cores. The time-dependence of deuterium fractionation and the relative abundances of different nuclear spin modifications are supposed to provide means of determining the evolutionary stages of these objects. Aims. We aim to test the current understanding of spin-state chemistry of deuterated species by determining the abundances and spin ratios of NH 2 D, NHD 2 , and ND 3 in a quiescent, dense cloud. Methods. Spectral lines of NH 3 , NH 2 D, NHD 2 , ND 3 , and N 2 D + were observed towards a dense, starless core in Ophiuchus with the APEX, GBT, and IRAM 30-m telescopes. The observations were interpreted using a gas-grain chemistry model combined with radiative transfer calculations. The chemistry model distinguishes between the different nuclear spin states of light hydrogen molecules, ammonia, and their deuterated forms. Different desorption schemes can be considered. Results. High deuterium fractionation ratios with NH 2 D/NH 3 ∼ 0.4, NHD 2 /NH 2 D ∼ 0.2, and ND 3 /NHD 2 ∼ 0.06 are found in the core. The observed ortho/para ratios of NH 2 D and NHD 2 are close to the corresponding nuclear spin statistical weights. The chemistry model can approximately reproduce the observed abundances, but predicts uniformly too low ortho/para-NH 2 D, and too large ortho/para-NHD 2 ratios. The longevity of N 2 H + and NH 3 in dense gas, which is prerequisite to their strong deuteration, can be attributed to the chemical inertia of N 2 on grain surfaces. Conclusions. The discrepancies between the chemistry model and the observations are likely to be caused by the fact that the model assumes complete scrambling in principal gas-phase deuteration reactions of ammonia, which means that all the nuclei are mixed in reactive collisions. If, instead, these reactions occur through proton hop/hydrogen abstraction processes, statistical spin ratios are to be expected. The present results suggest that while the deuteration of ammonia changes with physical conditions and time, the nuclear spin ratios of ammonia isotopologues do not probe the evolutionary stage of a cloud.

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“…4.1), we used spectroscopic observations of a typical shock tracer, SiO, as an indirect probe of ongoing accretion processes. Of the 80 infrared-quiet clumps, we selected 46 objects to follow up with the FLASH + receiver (Klein et al 2014) at the APEX telescope (Güsten et al 2006). The source selection was driven by the distance distribution of the sample to favour close-by objects (d ≤4.5 kpc), and focused on the newly discovered objects (see Sect.…”

Section: Sio (8-7) Emission Towards Infrared-quiet Massive Clumpsmentioning

confidence: 99%

The ATLASGAL survey: The sample of young massive cluster progenitors

Csengeri

Bontemps

Wyrowski

et al. 2017

A&A

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Context. The progenitors of high-mass stars and clusters are still challenging to recognise. Only unbiased surveys, sensitive to compact regions of high dust column density, can unambiguously reveal such a small population of particularly massive and cold clumps. Aims. Here we use the ATLASGAL survey to identify a sample of candidate progenitors of massive clusters in the inner Galaxy. Methods. We characterise a flux limited sample of compact sources selected from the ATLASGAL survey. Sensitive mid-infrared data at 21−24 µm from the WISE and MIPSGAL surveys were explored to search for embedded objects, and complementary spectroscopic data were used to investigate their stability and their star formation activity. Results. We identify an unbiased sample of infrared-quiet massive clumps in the Galaxy that potentially represent the earliest stages of massive cluster formation. An important fraction of this sample consists of sources that have not been studied in detail before. We first find that clumps hosting more evolved embedded objects and infrared-quiet clumps exhibit similar physical properties in terms of mass and size, suggesting that the sources are not only capable of forming high-mass stars, but likely also follow a single evolutionary track leading to the formation of massive clusters. The majority of the clumps are likely not in virial-equilibrium, suggesting collapse on the clump scale. Conclusions. We identify the precursors of the most massive clusters in the Galaxy within our completeness limit, and argue that these objects are undergoing large-scale collapse. This is in line with the low number of infrared-quiet massive clumps and earlier findings that star formation, in particular for high-mass objects is a fast, dynamic process. We propose a scenario in which massive clumps start to fragment and collapse before their final mass is accumulated indicating that strong self-gravity and global collapse is needed to build up rich clusters and the most massive stars.

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FLASH$^{+}$—A Dual-Channel Wide-Band Spectrometer for APEX

Cited by 58 publications

References 3 publications

ATLASGAL-selected massive clumps in the inner Galaxy

ATLASGAL-selected massive clumps in the inner Galaxy

Deuteration of ammonia in the starless core Ophiuchus/H-MM1

The ATLASGAL survey: The sample of young massive cluster progenitors

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