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Universität zu Köln
Mathematisch-Naturwissenschaftliche Fakultät
Fachgruppe Physik

I. Physikalisches Institut

Heating and cooling processes in the interstellar medium, Cologne, 7-9.9.2016

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Heating and cooling process in the ISM, Cologne, 7-9.9.2016
Focus of the workshop

Studying the main heating and cooling processes in molecular clouds is vitally important for a better comprehension of the physics and chemistry of the interstellar medium, and ultimately of star formation.  Because gas cooling is dominated by line and continuum radiation in the far-infrared wavelength range, our current knowledge largely results from space missions such as Herschel, Spitzer and Akari. With SOFIA (Stratospheric Observatory for Far-Infrared Astronomy) we now have flexible and continuous access to this still highly unexplored spectral range.

The objective of this workshop is to summarize our theoretical and observational understanding of the relative importance of the various heating and cooling processes in the ISM. It is a logical continuation and extension of the FIR fine structure line workshop that took place in Heidelberg in June 2015. This productive meeting reviewed the physics of FIR cooling lines in Galactic and extragalactic environments. Now we want to go a step further and address detailed questions, i.e. the microphysics of molecular excitations and the coupling between gas and dust and ionized and neutral species, radiative transfer processes, and models of photon dominated regions (PDRs), protostellar cores, and more diffuse clouds. Special emphasize will be given to understand heating via low- and high-velocity shocks and cooling through far-infrared (FIR) fine-structure lines of CII, OI, and NII, and rotational transitions of CO. We want to discuss how to best combine observations using different instruments and settings on SOFIA and complementary telescopes to obtain a complete inventory of the main heating and cooling processes in individual regions. We address the Galactic and extra-galactic  community as well as theorists working in this field.

In order to make progress during the limited time of the workshop, we ask all participants to check the session topics below and propose a talk or poster that addresses one of the questions. All oral contributions are scheduled for 20 min + 5 min discussion. For each session, we will invite speakers for review talks  (30 min + 5 min).

The workshop is supported by the DFG Schwerpunkt-Programm ISM-SPP (1753) and the DFG Sonderforschungsbereich SFB 956 Conditions and Impact of Star Formation.


Session 1: Interpreting observations

  • How can we seperate the multi-phase (ionized, atomic, molecular gas) origin of CII and OI?
  • What are the consequences of optically thick and self-absorbed [CII] lines on Galactic and extragalactic observations? Is there a need for 13CII observations ?
  • What causes the observed [CII] deficit in the Central Molecular Zone, some molecular clouds, and galaxies with high SFR?
  • Which observations can disentangle the effects of surface density and local environment for the [CII] emission?
  • Which gas regimes are traced by [NII], [CII], [SIII], and [OIII] on which spatial scales?
  • Which complementary data sets (molecular lines, IR, FIR, radio, X-ray etc.) are required/useful for interpreting the current observations of finestructure lines?
  • How can we translate our observations into diagnostics of density, temperature and UV-field?
  • How does metallicity affect our interpretations of the finestructure lines?
  • Are lessons from high-z sources useful for interpreting local source observations?

Session 2: Heating and cooling processes

  • How can we best compare dust and line cooling?
  • What is the best diagnostic for the gas heating efficiency?
  • Which line-to-continuum ratio is the best diagnostic for the line cooling efficiency?
  • Which frequency bands are best suited for measuring the dust cooling – and on which scales?
  • What are the conditions for the coupling between gas and dust and ionized and neutral species?
  • Can we distinguish cosmic ray heating and X-ray heating?
  • Can we measure the contribution of UV heating in irradiated shocks?
  • Under which conditions do the [CII] and [OI] lines contribute significantly to the gas cooling?
  • On what scales can we compare the cooling by dust and the gas cooling through lines of [CII], [OI], and [NII], and CO?
  • On what scales do dust properties (size distribution, composition, material properties) change in the ISM?
  • How does UV irradiation alter the dust properties?
  • Are heating and cooling processes affected by turbulence such as that seen in some highly turbulent high-z sources?

Session 3: Accessing the THz (FIR) wavelength range

  • How to propose and perform the best SOFIA observations to measure the ISM heating/cooling balance?
  • Synergy with other existing and future single dish telescopes and interferometers (ALMA, NOEMA, CCAT, SPICA, ...)
  • How can we combine spatial and spectral information to obtain a 3-D model of the cooling line emission?
  • What is the most efficient way to combine observations at very different spectral resolutions? Do we always need the spectral information? 

Session 4: Radiative heating

  • Are there any distinctive chemical tracers for particular heating mechanisms?
  • Does the Draine field exist?
  • Can we measure the shape of the UV field through the chemistry in photo-selective dissociation?
  • What is the role of H2 in the gas cooling of the different dense phases?
  • How can we estimate the total H2 cooling?
  • What are crucial couplings between local and global ISM/cloud properties (e.g. how does 'local' chemistry influence global properties)?
  • How well are binding energies on 'dust' surfaces know, and how does their uncertainty affect the chemistry/ energy balance?
  • How can we derive the 3-dim UV field strength/structure in molecular clouds by combining various observations?
  • What are the 'rule-of-thumb' uncertainties invoked by standard assumptions made in analysis/interpretation of astronomical data? (e.g. same T for dust & gas, all gas in the same plane of sky, isothermal assumption, etc.)

Session 5: Shocks

  • What are best tracers for low-velocity shocks and turbulent dissipation under different conditions?
  • How important are low-velocity shocks for the thermal and chemical excitation of [CII],[OI], CH+, OH+, and OH? When can they be neglected?
  • What is the role of the shock geometry for the gas heating efficiency?
  • How does the gas chemistry differ in irradiated shocks from a simple PDR chemistry?
  • What scales are affected by what velocities?
  • What is the statistical impact of protostellar outflow shocks, stellar wind shocks, and SN bubble shocks on the dense medium?
  • How do shocks couple to the chemical properties of the ISM?

Invited Review speakers:

Session 1:    Diane Cormier (ZAH Heidelberg, Germany)  and Jorge Pineda (JPL, USA)

Session 2:    Mark Wolfire (University of Maryland, USA)

Session 3:    Juergen Stutzki (KOSMA, Germany)

Session 4:    Jacques Le Bourlot (Observatoire de Paris, France)

Session 5:    Sibylle Anderl (LAOG Grenoble, France)

Scientific Organizing Committee
Local Organizing Comittee
Sylvain Bontemps Laboratoire d'astrophysique Universite de Bordeaux/France Nicola Schneider KOSMA
Carl Ferkinhoff Winona State University USA Volker Ossenkopf KOSMA
Javier Goicoechea CSIC Madrid/Spain Markus Röllig KOSMA
Michael Kaufman San Jose State University USA Robert Simon KOSMA
Suzanne Madden CEA Saclay/France Susanne Herbst SFB 956
Nicola Schneider KOSMA University of Cologne
Simon Glover Institut fuer theoretische Astrophysik Universität Heidelberg/Germany
Alexander Tielens Leiden observatory Leiden/Netherlands
Hans Zinnecker Deutsches SOFIA Institut Germany



Please go to the form and supply the information as asked in the form. Please indicate clearly in which session(s) you propose your contribution. You will be notified of your registration by email.

There is no registration fee. Invited review speakers (one for each session thus 5 in total) receive a travel grant of 500 Euros each. We are able to support 5 students/postdocs with 300 Euros each. The applicants should indicate that they are interested in such a support and are expected to propose a talk or poster.

Submission deadline for contributions is 1.7. 2016, for registration 1.7. 2016.
There are no proceedings, but we intend to make talks (if requested password protected and thus only accessible to the conference participants) and posters available on the workshop web pages.

All sessions will take place in the Hoersaal III in the I. Physik. Institut, University of Cologne.

I. Physik. Institut, University of Cologne
Zuelpicher Str. 77
50937 Köln

Please view map or read turn-by-turn directions how to get there.

Lunch at the university canteen:  For having lunch at the university canteen you need either a voucher or plastic money. You can get both in the canteen building, Zülpicher Straße 70. The ticket booth is located in the first floor opposite of the coffee shop. For the 'canteen card”'(plastic money) one has to deposit 5 EURO. When returning the card, you will receive the left over money and the deposit in cash. Please be aware that the card can only be returned during the very limited opening hours.
In case you prefer a voucher you need to select your meal first. Then you buy the respective voucher at the ticket booth.

The opening hours of the ticket booth are typically ~12:30 - 13:30.


Hotel ibis-styles Koeln City
Barbarossaplatz 4a
50674 Köln, Germany
Phone: +49 221 9215200
Fax: +49 221 9215208
Room rate: single € 89 (plus 12% tax/levy), 20 rooms are reserved for this event until 8.8., cancellation free until 24.8.
Distance to venue: 1.6 km, 0.99 miles

Social Events

We plan to have a Rhine river cruise and an evening in a Koelsch-brewery on the evenings of wednesday and thursday. Please indicate during registration if you are interested.

If you have any questions or comments regarding the meeting, please contact nschneid (at)