Michael Dumke

Probing isotopic ratios at z = 0.89: molecular line absorption in front of the quasar PKS 1830-211

With the Plateau de Bure interferometer, we have measured the C, N, O and S isotopic abundance ratios in the arm of a spiral galaxy with a redshift of 0.89. The galaxy is seen face-on according to HST images. Its bulge intercepts the line of sight to the radio-loud quasar PKS 1830−211, giving rise at mm wavelengths to two Einstein images located each behind a spiral arm. The arms appear in absorption in the lines of several molecules, giving the opportunity to study the chemical composition of a galaxy only a few Gyr old. The isotopic ratios in this spiral galaxy differ markedly from those observed in the Milky Way. The 17 O/ 18 Oa nd 14 N/ 15 N ratios are low, as one would expect from an object too young to let low mass stars play a major role in the regeneration of the gas.

APEX: the Atacama Pathfinder EXperiment

APEX, the Atacama Pathfinder Experiment, has been successfully commissioned and is in operation now. This novel submillimeter telescope is located at 5107 m altitude on Llano de Chajnantor in the Chilean High Andes, on what is considered one of the worlds outstanding sites for submillimeter astronomy. The primary reflector with 12 m diameter has been carefully adjusted by means of holography. Its surface smoothness of 17-18 μm makes APEX suitable for observations up to 200 μm, through all atmospheric submm windows accessible from the ground.

Detection of H 2 D + in a massive prestellar core in Orion B

Aims. The purpose of this study is to examine the prediction that the deuterated H3+ ion, H2D+, can be found exclusively in the coldest regions of molecular cloud cores. This is also a feasibility study for the detection of the ground-state line of ortho-H2D+ at 372 GHz with APEX. Methods. The 1(10)-1(11) transition of H2D+ at 372 GHz was searched towards selected positions in the massive star forming cloud OriB9, in the dark cloud L183, and in the low- to intermediate mass star-forming cloud R CrA. Results. The line was detected in cold, prestellar cores in the regions of OriB9 and L183, but only upper limits were obtained towards other locations which either have elevated temperatures or contain a newly born star. The H2D+ detection towards OriB9 is the first one in a massive star-forming region. The fractional ortho-H2D+ abundances (relative to H2) are estimated to be about 1.0E-10 in two cold cores in OriB9, and 3.0E-10 in the cold core of L183. Conclusions. The H2D+ detection in OriB9 shows that also massive star forming regions contain very cold prestellar cores which probably have reached matured chemical composition characterized, e.g., by a high degree of deuterium fractionation. Besides as a tracer of the interior parts of prestellar cores, H2D+ may therefore be used to put contraints on the timescales related to massive star formation.

The APEX calibration plan: goals, implementation, and achievements

The quality of scientific data depends on the accuracy of the absolute intensity calibration. This absolute calibration is especially difficult in ground-based sub-mm astronomy. At the Atacama Pathfinder Experiment (APEX), we take various measures in order to ensure a proper calibration of the final science product, including real-time efforts (e.g. pointing models) and dedicated measurements whose results are applied afterwards (e.g. opacity or efficiencies). In this presentation we will give an overview over the various steps taken at APEX to overcome most calibration challenges. We will explain their implementation as calibration plan, present an analysis of the results obtained, and discuss those results in view of the reliability of the released science product.

APEX: five years of operations

APEX, the Atacama Pathfinder EXperiment, is being operated successfully, now for five years, on Llano de Chajnantor at 5107m altitude in the Chilean High Andes. This location is considered one of the worlds outstanding sites for submillimeter astronomy, which the results described in this contribution are underlining. The primary reflector with 12 m diameter is cautiously being maintained at about 15 μm by means of holography. This allows to access all atmospheric submillimeter windows accessible from the ground, up to 200 μm. Telescope and instrument performance, operational experiences and a selection of scientific results are given in this publication.

APEX beyond 2016: the evolution of an experiment into an efficient and productive Submillimeter Wavelength Observatory

The Atacama Pathfinder EXperiment (APEX) operates a 12m submillimeter wavelength telescope in the high Andes in Chile at 5107 m above sea level since 20061. Several steps have been taken to improve the operation efficiency of the facility in the given harsh environmental conditions2. The developments in remote control and -sensing allowed in 2017 for the transition to a remote science operations scheme, observing 24/7 from the basecamp control center in San Pedro de Atacama. Also engineering and maintenance is in the transition phase to a similar scheme to minimize presence and activities at the very high site. Instrument control servers allowing remote operation even of heterodyne THz instrumentation, with no compromise on instrument performance, had been developed and proven to reliably work3. The transition to full remote science operations required major hardware upgrades on the antenna drive system and a failsafe remote-control system to ensure the safety of the antenna, the Sun Avoidance System (SAS). We report on the layout, the implementation and on the experience of the first year of this new operations model started in April 2017. The engineering tasks also are in a transition phase to a scheme that minimizes the presence at the antenna. Daily engineering work at the high site for preventive and corrective maintenance can be reduced when all critical hardware systems are integrated in a remote monitoring and control system. We have started with this in 2015 and have stepwise introduced this new scheme. This required the introduction of redundancies of systems as well as the extension of sensing points and remote-control interfaces, throughout all levels in the project breakdown structure of the telescope and its auxiliary systems. We present examples of theses implemented systems and discuss the concept of redundancies. The APEX observatory is the smallest ESO site in Chile, incorporated as a department of LPO, the ESO La Silla – Paranal Observatory, within the directorate of Operations (DoO). The work presented will attempt an outline of approaches that can be applied to telescopes exposed to similar environmental conditions as well as to larger and distributed operations such as envisaged for the Paranal Observatory extended by the ELT on Cerro Armazones.

First results of the polarimeter for the Large APEX Bolometer Camera (LABOCA)

An enhanced version of the ”Polarimeter für bolometer Kameras” (PolKa) has been installed on the APEX telescope (Atacama Pathfinder EXperiment) in October 2009, to work in combination with LABOCA (the Large APEX Bolometer Camera). This polarimeter was included in the design of LABOCA’s optics from the beginning and it is now going through a commissioning and science verification phase. The combination of PolKa, LABOCA and APEX provides superior capabilities in mapping the polarization of the continuum at submillimeter wavelengths. We present here some preliminary results of the last commissioning run.

Service observing management at the APEX telescope

The execution of scientific observations in service observing mode requires an efficient transfer of information about project setup and observing procedures from the PI to the actual observer. At the APEX telescope, we have implemented an efficient, web-based system to manage the service observing of astronomical projects. This system includes the submission of relevant project information through a web form, the monitoring of the observing progress through collaboration tools, and the data handling and archiving. In this paper I give an overview over how service observing is managed and performed at APEX. I explain the implementation of the project submission facility, the information flow from submission to observation, and the various components involved. I conclude highlighting the advantages of this system.

Detection of H

Aims. The purpose of this study is to examine the prediction that the deuterated H3+ ion, H2D+, can be found exclusively in the coldest regions of molecular cloud cores. This is also a feasibility study for the detection of the ground-state line of ortho-H2D+ at 372 GHz with APEX. Methods. The 1(10)-1(11) transition of H2D+ at 372 GHz was searched towards selected positions in the massive star forming cloud OriB9, in the dark cloud L183, and in the low- to intermediate mass star-forming cloud R CrA. Results. The line was detected in cold, prestellar cores in the regions of OriB9 and L183, but only upper limits were obtained towards other locations which either have elevated temperatures or contain a newly born star. The H2D+ detection towards OriB9 is the first one in a massive star-forming region. The fractional ortho-H2D+ abundances (relative to H2) are estimated to be about 1.0E-10 in two cold cores in OriB9, and 3.0E-10 in the cold core of L183. Conclusions. The H2D+ detection in OriB9 shows that also massive star forming regions contain very cold prestellar cores which probably have reached matured chemical composition characterized, e.g., by a high degree of deuterium fractionation. Besides as a tracer of the interior parts of prestellar cores, H2D+ may therefore be used to put contraints on the timescales related to massive star formation.

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Aims. The purpose of this study is to examine the prediction that the deuterated H3+ ion, H2D+, can be found exclusively in the coldest regions of molecular cloud cores. This is also a feasibility study for the detection of the ground-state line of ortho-H2D+ at 372 GHz with APEX. Methods. The 1(10)-1(11) transition of H2D+ at 372 GHz was searched towards selected positions in the massive star forming cloud OriB9, in the dark cloud L183, and in the low- to intermediate mass star-forming cloud R CrA. Results. The line was detected in cold, prestellar cores in the regions of OriB9 and L183, but only upper limits were obtained towards other locations which either have elevated temperatures or contain a newly born star. The H2D+ detection towards OriB9 is the first one in a massive star-forming region. The fractional ortho-H2D+ abundances (relative to H2) are estimated to be about 1.0E-10 in two cold cores in OriB9, and 3.0E-10 in the cold core of L183. Conclusions. The H2D+ detection in OriB9 shows that also massive star forming regions contain very cold prestellar cores which probably have reached matured chemical composition characterized, e.g., by a high degree of deuterium fractionation. Besides as a tracer of the interior parts of prestellar cores, H2D+ may therefore be used to put contraints on the timescales related to massive star formation.