PHD Projects of the Millimeter and Submillimeter Astronomy

Director: Prof. Dr. Karl Menten

Group Website

Code: KM01

The chemistry and physics of the diffuse interstellar medium

The Heterodyne Instrument for the Far-Infrared (HIFI) abord Herschel opened a whole new era of studies of the diffuse interstellar medium (ISM). Utilizing Herschel’s superb sensitivity combined with its high spectral resolution receivers operating in a low thermal background space environment, HIFI revolutionized observations of light hydrides, many of which have their ground-state rotational transitions in the submillimeter and far infrared range. As the building blocks of larger molecules, the (mostly) di- or triatomic species detected by HIFI and (also by APEX and SOFIA) are of central astrochemical interest. In addition, they triggered new interest in the physics and chemistry of diffuse and translucent clouds, for example in their role as interfaces between the cold (and warm) neutral atomic and the denser, cold molecular phases of the ISM in our, but also in external galaxies.

Building on the success of Herschel, new opportunities arise with ground-based and airborne observations of hydrides: in the submillimeter range, hydrides such as 13CH+, OH+, and SH+ can be studied using the APEX telescope with new receivers and the exceptional atmospheric conditions on the Chajnantor Plateau in northern Chile. Access to even higher frequencies is provided by the airborne Stratospheric Observatory for Infrared Astronomy (SOFIA) and the GREAT receiver and allows observations of CH, SH and OH, to name just a few of the simplest hydrides. A thorough analysis of such observations will lead to a comprehensive characterization of hydrides in diffuse clouds throughout our Galaxy.

Possible dissertation projects comprise observational studies with, predominantly, SOFIA and APEX, but also with other telescopes as well modeling of the data and bringing them into context with a glabal view of the Milky Way galaxy's ISM.

Contact: Prof. Dr. Karl Menten (kmenten@mpifr-bonn.mpg.de)

Code: KM02

Effelsberg K-band fingerprints of star forming regions

The unprecendented sensitivity and large bandwidth (8GHz) of the new Effelsberg K-band receiver, covering 18-26 GHz in frequency, offer new opportunities to study the physical and chemical conditions of star forming regions and mant other interesting sources with unbiased line surveys. These surveys give access to probes of temperature, density and chemistry that can be used to characterize the evolutionary stages of the regions. The project will be very complementary to line survey projects conducted with the IRAM 30m and APEX 12m telescopes in the millimeter and submillimeter wavelength range, respetively.

The K-band contains many interesting lines, amongst them the many transitions of ammonia (including 15NH3 and non-metastable lines), as well as lines from carbon chains like HC3N, HC5N (for both also isotopologues and vibrationally excited levels), from molecules like methanol, CCS, C3H2, C6H and several recombination lines and maser transitions (water, methanol, ammonia), make K-band line surveys very appealing for molecular fingerprints, that can be used to rapidly characterize the main charactistics and the evolutioniary stage of the regions, then leading to a new “K-band spectral classification” of star forming regions.

For such surveys, a sophisticated data reduction pipeline, capable of processing and calibrating the large amount of data will be needed. The PhD candidate will participate in setting up this pipeline to prepare for the analysis of the wealth of molecular line data. A background in software engineering and experience with data reduction of radio astronomical data would be a plus.

Contact: Dr. Friedrich Wyrowski (wyrowski@mpifr.de), Dr. Benjamin Winkel (bwinkel@mpifr.de), Dr. A. Kraus (akraus@mpifr.de) Prof. Dr. Karl Menten (kmenten@mpifr-bonn.mpg.de)

Code: KM03

The Galactic center and the Central Molecular Zone

Studying the physical and chemical processes occurring in the nuclear regions of galaxies is of fundamental importance for understanding the formation, evolution and dynamics of galaxies. Many galaxies, including our Milky Way, contain huge amounts of gas in their central hundred parsecs. This molecular and atomic material is strongly affected by the presence of the large potential gradients, X-rays, cosmic rays, and magnetic fields. These extreme conditions result in the well known properties of the molecular clouds in our Galactic center, such as the large velocity widths, high kinetic temperatures and the high chemical complexity observed in this region.

At ~8 kpc from us, the center of our Galaxy presents a unique laboratory to study the phenomena occurring in the heart of the galaxies with high spatial resolution. APEX and ALMA with their location in the southern hemisphere, which allows 11 h of observing time per day, and the excellent weather conditions at the Chajnantor site, are unique telescopes to study the Galactic center in the submm regime.

In this ambitious project the large scale kinematics and the unique physical and chemical conditions in the Central Molecular Zone will be studied with new muti-beam receiver arrays on the APEX telescope. ALMA will be used for a high angular resolution view of selected regions.

Contact:  Prof. Dr. Karl Menten (kmenten@mpifr-bonn.mpg.de)
Site: Bonn, Max-Planck-Institut für Radioastronomie, Millimeter and Submillimeter Astronomy Group

Code: KM04

A comprehensive Galactic plane radio wavelength star formation survey

Understanding the circumstances of massive star formation is one of the great challenges of modern astronomy. In the last years, our view of massive star forming regions has dramatically been changed by Galactic plane surveys covering centimeter to infrared wavelengths. These surveys enable us for the first time to study ALL evolutionary stages of massive star formation in an unbiased way. With the exciting results of the new submm/FIR surveys from the ground (ATLASGAL) and space (Hi-GAL) the massive and cold dust clumps from which massive cluster form are now detected in an unbiased way. Complementary, the EVLA will allow incredibly powerful and comprehensive radio- wavelength surveys of, both, the ionized and the molecular tracers of star formation in the Galactic plane.

In this project, the extremely wideband (4-8 GHz) new C-band receivers of the EVLA will be used for an unbiased survey to find and characterize star-forming regions in the Galaxy.  This survey of the Galactic plane, that is now ongoing, will detect tell-tale tracers of star formation: compact, ultra-, and hyper-compact Hii regions and molecular masers which trace different stages of early stellar evolution and will pinpoint the very centers of the early phase of
star-forming activity. Combined with the submm/infrared surveys it will offer a nearly complete census of the number, luminosities and masses of massive star forming clusters in a large range of evolutionary stages and provide a unique dataset with true legacy value for a global perspective on star formation in our Galaxy.

Contact: Dr. Friedrich Wyrowski (wyrowski@mpifr- bonn.mpg.de), Prof. Dr. Karl Menten (kmenten@mpifr-bonn.mpg.de)

Site: Bonn, Max-Planck-Institut für Radioastronomie, Millimeter and Submillimeter Astronomy Group

Code: KM05

A 350 micron Galactic Plane survey of the inner Milky Way

The very successful APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) has revealed for the first time the structure of the cold interstellar medium over several 100 sq. deg. The survey was conducted with LABOCA at the APEX telescope to conduct an unbiased census of massive star forming clumps and their different evolutionary stages in the inner Galaxy.

Soon a new, much larger bolometer camera will be commissioned at the APEX telescope, the A-MKID dual color camera with ~3500 pixel at 870 and ~20000 pixel at 350 micrion. At the short wavelengths, this instrument will allow to resolve sources of 0.1 pc size within 3 kpc towards giant star forming complexes.  When combining the A-MKID data with the Herschel/Hi-GAL survey at 60 to 600 micron, it will be possible to:

• derive evolutionary stages for a representative sample of star forming clumps

• compute dust emissivity and temperature over a large star forming complex

• analyze how the physical conditions vary within one giant complex

• study the fragmentation of clumps into cores that can give birth to individual stars

Given its high angular resolution and unbiased nature, such a survey

will provide a legacy and pathfinder for years to come.

Contact: Dr. Friedrich Wyrowski (wyrowski@mpifr- bonn.mpg.de), Prof. Dr.Karl Menten (kmenten@mpifr-bonn.mpg.de)

Site: Bonn, Max-Planck-Institut für Radioastronomie, Millimeter and Submillimeter Astronomy Group

Code: KM06

Physical and chemical conditions in giant molecular clouds

Massive stars form in dense clumps within giant molecular clouds (GMCs), but how do these clouds form and evolve, how do the dense clumps form within them and what are the conditions for star formation within these dense clumps? To address these questions the MPIfR operates powerful heterodyne cameras for line observations, such as the upcoming new LAsMA array for observations at 345GHz and the CHAMP+ array (690 and 810 GHz), both at APEX, complemented by the upGREAT array on SOFIA for THz observations of important fine structure cooling lines. The high mapping speed of these cameras enables to map giant molecular clouds on degree scales in a variety of molecules. Such a chemical inventory provides a new view on the large scale properties of molecular clouds. Furthermore, by combining results from the different cameras the excitation and cooling of the clouds can be constrained to form a comprehensive picture of the formation and condition in GMCs.

Some of scientific questions to tackle with these observations are: What is the dynamics of the clouds and the embedded clumps? How strongly are the chemical conditions in the clouds altered by interaction processes, either from the outside of the clouds or by feedback from the ongoing star formation in the clouds? Can some of the chemical variations be used in conjunction with chemical models as chemical clocks to put different clumps in the clouds into an evolutionary sequence? How do these large-scale chemical properties of Galactic GMCs compare with observations of their extra-galactic counterparts that are now feasible with the high sensitivity and angular resolution of ALMA?

Contact: Dr. Friedrich Wyrowski (wyrowski@mpifr-bonn.mpg.de), Prof. Dr.Karl Menten (kmenten@mpifr-bonn.mpg.de)
Site: Bonn, Max-Planck-Institut für Radioastronomie, Millimeter and Submillimeter Astronomy Group

Code: KM07

Star forming galaxies in the early universe

In the last two decades, millimeter and submillimeter surveys have transformed our understanding of galaxy formation and evolution by revealing that luminous, dusty galaxies were a thousand times more abundant in the early universe than they are at the present day and form an important population of star forming galaxies in the high redshift universe. Large scale surveys, such as the LABOCA Submillimeter Survey of the Extended Chandra Deep Field South (LESS) and South Pole Telescope survey (SPT) have revealed hundreds of high redshift DSFGs. In order to determine the formation mechanisms and the physical conditions in these actively star- forming galaxies this project aims on conducting detailed follow-up observations using ALMA, ATCA and APEX. In conjunction with archival Herschel these observations can be used to derive the redshifts, the dust properties as well as the molecular excitation via observations of multiple CO, the CI fine structure lines and observations of ionised carbon. The aim of this project is to combine all the available information, potential including ALMA high spatial resolution maps, to determine the intrinsic properties of the gas reservoirs in great detail and to compare they to the properties of local actively star forming systems.

Contact: Dr. Axel Weiss (aweiss@mpifr.de)

Code: KM08

Deuterated molecules in early stages of high-mass star-formation

Probing the initial conditions and early stages of high-mass clumps is key for our understanding of the formation of high-mass star clusters. Deuterated molecules might provide a unique view onto the physical conditions in cold molecular clumps. A high deuteration of molecules has been found towards early stages of high-mass star-formation. In particular, the ATLASGAL unbiased inner Galactic Plane survey of the 870~$\mu$m dust continuum provides an ideal hunting ground for massive clumps in early evolutionary stages and our previous 3mm line surveys of flux-limited samples of massive clumps lead to many new detections of bright deuterated ammonia. These clumps were followed up in the deep integrations with the IRAM 30m and APEX 12m telescopes to study a range of deuterated molecules and their excitation. These new observations will be used to constrain chemical models of deuteration and to study the physical conditions and dynamics in early stages of high-mass star-formation.

contact: Dr. Friedrich Wyrowski (fwyrowski@mpifr.de)

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