Malcolm’s Memoriesand OH study

Alain BaudryUniv. de Bordeaux, LAB

The scientific heritage of Malcolm WalmsleyFlorence, October 1-2, 2018

Simple memories of my early professional life with Malcolm

• First memories date back to my first coming to Effelsberg around 1978

• Our plan with Malcolm was to constrain physical conditions in the cloudsaround the iconic compact HII region, W3(OH) • We thought 18cm lines were insufficient. Observing higher energy states was the right

approach• OH spectroscopy was accurate + coherent set of Aij and freqs. across energy ladder

• Collision rates not well known

• It was my very first contact with the 100m • Malcolm was helping a lot and he decided I should be the PI of this project• Took us 2 years to gather ‘difficult’ observations at 13.4 and 23.8 GHz

• A&A paper published in 1981 with clear conclusions • OH excitation dominated by IR radiation emitted by dust at 150-200K

• OH clouds just against ionization front … we saw absorption

• Splitting of 13.4 GHz, 4-4 line due to Zeeman effect => 6 mG magnetic field

• Later confirmed by VLBA

• This OH paper was the first of a series made with Malcolm, Tom Wilson

and me together with Stephane Guilloteau -using the 100-m & VLA

• About 8 papers devoted to excited OH … truly an ‘adventure’ at that time

• Much due to or initiated by Malcolm who had a leading role in understanding

OH in the Galaxy

• Later, Malcolm strongly encouraged the work led by Thierry Jacq on

deuterated water HDO

• Malcolm helped in developing a radiative transfer code to interpret our data. …

was successful, very well cited publications

• These works, and others, contributed to the good spirit of cooperation

between the MPIfR and Observatoire de Bordeaux groups

• Culminating in joint research programs with the IRAM 30-m and P. de Bure

• Malcolm’s influence and projects strongly contributed in developing the

science coming out of the IRAM facilities

• Indirectly contributed in developing the IRAM institute as a whole

• The very first works done around 1978-1980 were I believe at the root of a most sincere friendship• Never failed even when we were not working together

• Final anecdote: time where I was building up the European ALMA Back-End and Correlator teams & looking for a good engineer in Italy• I discussed with Malcolm & fully trusted his recommendation … was truly succesful

• Malcolm also helped in producing an attractive A&A paper on the ALMA correlator

These simple facts to give evidenceof Malcolm’s generosity and perspicacity