The Fourth NEON Observing School
Calar-Alto, August 7-20, 2005

This school was held at the Calar Alto Observatory in Spain, where the very first Neon school was held already in year 2000.
Sixteen students and 8 tutors and lecturers, from 12 different nationalities, gathered in this nice location for a two weeks, intensive session devoted to all the "tricks" of an observating run, from the preparation of the observations, to observations themselves, data reductions and presentation of the scientific results on the last day.

The fundamentals of observing techniques were delivered in a series of introductory lectures, which included:
Photometric techniques, by H.J. Roeser (Heidelberg)
Optical and near-IR detectors by M. Dennefeld (Paris)
Image quality analysis, and specifics of wide-field imaging, by E. Bertin (Paris)
Spectroscopy by M. Dennefeld (Paris)

Further lectures during the school dealt with:
The use of  Virtual Observatories and large databases (J. Taylor, Edinburgh)
Novel instrumentation for VLT's (R. Gredel, Heidelberg)

For the research topics and observations at the telescope, students were divided into three groups, each of them having its specific topics and goals:

The first group, under the direction of A. Bik, made near-IR observations of high-mass Star Formation regions.
Such ultra-compact regions are not seen in the visible (absorption by dust, and sometimes screening by the surrounding gaz of
the HII region) , but are detected in radio.
Observations in the near-IR allow then to detect their "visible" counterpart, and study it both in imaging  and spectroscopy.
Among the various sources studied, a very high-mass star has been found in one of them, brighter than the most massive (O3) star,
with possible extra emisison from an accretion disk.

The second group, under the direction of S. Pedraz, studied a series of elliptical galaxies to determine their mass and stellar populations.
Imaging/photometry provided brightness profiles and masses, while spectroscopy provided line indices which, by comparison with various templates of standard stars, provided metallicity indexes and allowed to break the age-metallicity degeneracy. As expected, elliptical galaxies
show rather old stellar population, whose velocity dispersion could be measured also.

The third group, under the direction of S. Sanchez, studied a number of Luminous IR galaxies (LIRG's), through multi-colour imaging, including narrow-band filters in characteristic emission lines like Halpha or Sulfur II.
Once the line ratios are calibrated through spectroscopy, the images directly provide the star formation rate from the Halpha flux,
and an indication of the metallicity through the SII line. It was then shown (not unexpectedly...) that the LIRG's experience episodes of much stronger Star Formation then "standard" galaxies.

In addition, two Targets of Opportunity, which happened to be available at the appropriate moment, could also be observed!
This was the optical counterpart of the Gamma-ray burst 050714A;
and the new Nova Aquila 2005, which appears to be rather peculiar: indeed, combined visible and
near-IR observations showed that this object, being effectively a Nova,
suffers however a substantial reddening, which is rather unusual for such objects!

The  presentations of the scientific results at the end of the school gave opportunity to each of the students, without exception,
to make an oral presentation, sometimes their first one in english!
This is a necessary step  for  future  scientists.
A general discussion at the end of the school, led by M. Dennefeld and R. Gredel, allowed the presentation
of  various career opportunities in Europe, including those sponsored by the EU,
as well as a glance of the various observing facilities available to European scientists.

The students unanimously agreed that the school was "fantastic" although tiring, because so much had to be done in so little time!
Fortunately, a short break in the middle of the school, and  relaxation on the terrasse during diner time gave also opportunities to enjoy the nice scenery and tackle other topics of wide european interest...