The polarimetry part of my thesis was dedicated to a study of the magnetic field structure of the Taurus-Auriga molecular cloud by means of optical and IR polarisation measurements of background stars (Moneti et al. 1984). The morphology of cloud structures relative to the magnetic field lines suggested that collapse occurred preferentially along the magnetic field lines, explained in terms of the coupling between the very weakly ionised cloud material and the magnetic field, giving rise to a few sheet-like structures. I also found that the polarisation of the young sources embedded in the clouds was much stronger and perpendicular to that of the background stars. I suggested that this polarisation was intrinsic to the sources, being due to scattering of the light of the central sources in extended, asymmetric circumstellar (CS) envelopes whose orientation was also determine by the magnetic field.

For the second part of my thesis I used the new IR camera to investigate the immediate environment of young stars in order to look for extended structures. Images of the young prototypical outflow source Lynds 1551-IRS5 at 1.6, 2.2, and 3.5 micron revealed a roughly elliptical source with the major axis of ~ 1000 AU and oriented perpendicular to the magnetic field and to the outflow (Moneti et al. 1986, 1988. I interpreted this structure as a flattened circumstellar envelope formed by preferential collapse along the magnetic field lines, and illuminated from within. Later higher resolution observations showed that the envelope is actually a thin disk (Hodapp et al. 1988). In my thesis I also showed that the source Haro 6-10 was slightly extended; higher resolution studies later revealed that this source is in fact a binary (Leinert & Haas 1989). Other sources studied with the IR camera were the core of the BN/KL star forming region in Orion (Woodward et al. 1986), to determine its content of young stars, and of the starburst galaxy M82, to study its starburst nucleus (Pipher et al. 1987}, Lorenzetti et al. 1987), and of SN 1987A in the LMC (Bouchet et al. 1987, 1987, 1989, 1996). In both cases, I concentrated on the study of the characteristics of the dust and its production rate. I also continued to collaborate with the University of Rochester group on the analysis of other infrared camera observations (Woodward et al. 1986, 1989, 1992).

While at ESO I also began a program of direct IR imaging of binary T Tauri stars with the objective of using the 1.2, 1.6, and 2.2 micron (J, H, and K-band) photometry of the binary components to perform a comparative study of the stellar masses, roughly known from optical observation (e.g. Cohen & Kuhi 1979) and the masses of the circumstellar disks. Since disk evolution (and also PMS stellar evolution) is rapid, it was necessary to study coeval systems, hence the binaries, and to perform a pair-wise comparison. This study (Moneti & Zinnecker 1991), based on seven binaries and two triple systems in the Taurus association, showed that the primaries were redder in (J-K) color than the secondaries, contrary to what is expected for main sequence stars. In fact, we showed that the (J-K) color is a good tracer of the circumstellar disk's luminosity, and the disk luminosity increase more rapidly than the stellar luminosity as the stellar mass (and luminosity) increases. The relation with disk mass, however, could not be studied on the basis of the near-IR data alone.

While at ESO I also participated on the definition, construction, and installation of ESO's (and continental Europe's) first IR camera, and in January 1989 I accepted a position of resident astronomer and instrument scientist for the infrared cameras at ESO's La Silla Observatory. Once again I had left Europe. At La Silla I continued to perform high spatial resolution near-IR observations of various star-forming regions, and in particular I tried to exploit the 3.5 micron capabilities of the first ESO IR camera (Moorwood, Finger & Moneti 1988), e.g. revealing the double nature of RCW57/IRS1 (Moneti 1992). The most extensive study performed with that camera aimed to study of the characteristics of suspected young stellar objects in the central regions of the Galaxy (Glass, Moneti & Moorwood 1990, Moneti, Glass & Moorwood 1992, 1994). The ultimate goal of this program was to search for evidence of ongoing star formation within ~ 50 pc of the centre of the Galaxy. Such star formation is expected, for instance, on the basis of the total ionizing flux and the total far-IR luminosity of the Centre. Eight sources with very red K-L colours (from standard single-channel photometric observations) and with IRAS counterparts were selected for detailed study via direct IR imaging and spectroscopy. The most exciting of these sources turned out to be the Quintuplet Cluster, so named after its five very luminous and extremely red components. Our images revealed that the cluster contained many other fainter stars, though our spatial resolution was not sufficient to study them in detail, and our spectroscopy revealed featureless spectra of the Quintuplet proper member, making a definitive identification of the nature of these sources impossible. We referred to these as cocoon stars because they appear as very optically thick dust shells. Our spectroscopy, however did identify two cluster stars with emission-line spectra: one with weak Br-gamma and strong He 2.06 micron with a P-Cygni profile, which we identified as a likely Wolf-Rayet star, and one with strong Br-gamma on a ~ 7 mag K-band continuum, which we identified as a massive star undergoing heavy mass loss. The latter source attracted considerable attention, and later studies identified it as a probable luminous blue variable (LBV, see Figer et al. 1998). Given its location at the center of curvature of the Pistol HII region, this star became known as the Pistol star. The existence of WR stars in the cluster was also of particular interest because at about the same time other investigators began to find various He-emission stars in the Galactic Centre Cluster. As for the other targets of this work, some were found have emission lines, to be associated with compact radio continuum sources, and to have bolometric luminosities typical of late-type O star, and were believed to be true young sources. Others were found to have characteristics similar to the cocoon stars in the Quintuplet. No other cluster was identified.

ESO's second generation IR camera was installed in 1991 (Moorwood et al. 1992), incorporating larger and higher quality arrays, but losing the thermal IR capability. I used the new camera to observe nearly all the the spatially resolved binary T Tauri stars within about 200 pc of the Sun using ESO's second generation IR camera and under sub-arcsec seeing conditions (Moneti & Zinnecker, unpublished, some results in Brandner et al. 1996) to improve on the earlier results. I collaborated on a detailed study of star formation in the clouds associated with the Vela molecular Ridge (Liseau et al. 1992, Massi et al. 1999) which combined near-IR and IRAS data and (sub)-mm observations to identify many new Class I sources, and which led to the identification of several sites of star formation in these clouds. I conducted a search for and near IR study of the exciting sources of Herbig-Haro objects (Moneti & Reipurth 1995) to determine their location relative to the HH objects, which led to two new identifications and improved positions for a third, and shows that all have infrared colours typical of the youngest known sources and all are intimately associated with diffuse nebulosity. And I collaborated with the Bologna group on the studies of globular clusters in the near IR (Ferraro et al. 1994, Guarnieri et al. 1998).

In September 1994 I returned again to Europe to take a position of calibration astronomer with the ISO Science Operations Centre, first in ESTEC (The Netherlands) and then in Villafranca (Spain). This contract, which was as a SERCo contractor, lasted until December 1998. During the ISO mission I was responsible for ensuring consistency of the absolute calibration among the four ISO instruments, and between ISO and other space missions. I also advised the Project Scientist on calibration issues, wrote and maintained the top-level calibration-related documents, organized the bi-annual meetings of the Calibration Working Group, and organized other meetings on calibration and on detectors. During this time I presented the ISO calibration program at various conferences (Moneti 1995, Moneti & Breitfellner 1997, Moneti 1998).

But the pressures of satellite operations were stronger than envisaged by anyone on the team, and left very little time for research. Additionally, as I joined the ISO team after the Guaranteed Time programs and their teams had been defined, and after the deadline for the first (of two) call of observing proposals had passed, I found myself excluded from the established research groups. I did, however, continue to collaborate with the group of H. Zinnecker on issues related to the formation and early evolution of low-mass stars. In particular, we used ISO 7 and 15 micron observations to study the timescale for disk evolution and planet formation around weak-line and post T Tauri stars (Moneti et al. 1998, 1999, Stapelfeldt & Moneti 1999, Brandner et al. 2000) concluding that the circumstellar disks become dust depleted at ages of 5 to 15 Myr.

With the ISO mission lasting longer than expected, I obtained some guaranteed time, and used it to observe the Pistol Star and the Quintuplet Cluster with ISO-CAM and ISO-SWS. This led to the discovery of a nebula of ejected material around the Pistol Star (Moneti et al. 1999), and thus confirming its LBV. Previously only the ionised part of that nebula had been known as the Pistol HII region. Indeed, the emission line images extracted from the ISO-CAM Circular Variable Filter datacube also showed that part of the nebula is ionised, and it was concluded that the ionising photons originated in the hot WR stars in the Quintuplet Cluster, while the Pistol Star provided most of the energy necessary to heat the dust in the nebula (Moneti et al. 1999). As for the cocoon stars in the Quintuplet Cluster, the new results, which were combined with Palomar 5-m mid-IR imaging and spectroscopy, and with HST/NICMOS near-IR photometry, provided new arguments against all the tentative identifications that had been proposed (young objects, late-type, dusty WC stars, supergiants). The nature of these cocoon stars remains enigmatic (Moneti et al. 2001).

At the end of the ISO contract, I joined the astrophysics group of the Instituto de la Estructura de la Materia, led by Dr. J. Cernicharo, which is part of Spain's Consejo Superior de Investigaciones Científicas. In collaboration with J. Cernicharo I used archive ISO-SWS high resolution spectra of Sgr A* and of the Quintuplet sources to determine the physical conditions and the abundance of CO and H2O (in both gas and solid phase) in the cold, quiescent of molecular clouds along these lines of sight. Both molecules reveal that the gas is cold T ~ 8-12 K, though some 5\% of the total is somewhat warmer, at at few tens of degrees K, and that the abundance of water vapour relative to hydrogen is to be ~ 3E-7. In fact, some 98\% of the H2O molecules in these quiescent clouds are in the solid phase, condensed on grains, while 98% of the CO is in the gas phase. We find that the total (i.e., gas + solid) CO to H2O abundance ratio is ~ 5, making H2O the third most abundant molecule in molecular clouds, and implying that the mechanisms that lead to its formation, be they in the solid or in the gas phase, must be very efficient (Moneti & Cernicharo 2001).

In parallel with the work on the Galactic Centre sources, I continued to collaborate with H. Zinnecker on near-IR studies of young clusters. A particularly exciting project was the observation of the prototypical starburst cluster 30 Doradus using NICMOS on HST in order to search for sub-solar mass PMS stars, and to determine the cluster IMF. The NICMOS 1.6 micron high resolution images proved difficult to analyse due primarily to the very peculiar PSF of the NICMOS instrument and to the extreme crowding. Initial results (Zinnecker & Moneti 1998, Zinnecker et al. (1999) demonstrate that we indeed reach stars with H\moresim 22 mag, corresponding to a mass much below a solar mass (the exact value depends on the choice of evolutionary tracks) for an age of ~ 2 Myr of the 30Dor cluster. We are now conducting more detailed analysis, including completeness tests, to determine the luminosity and mass functions.

At the end of 1999 I moved to Paris, France, for family reasons. While looking for a more stable position, I have been visiting the Institut d'Astrophysique de Paris, where I have been working with Dr. A. Omont on the publication of the ISOGAL catalog, especially in checking the absolute and the relative photometric calibrations, and in preparing follow-up ground-based spectroscopic observations of selected sources. My goal in this collaboration is to investigate the extent of star formation in the Galactic Bulge, expanding on the work done earlier with I. S. Glass. A large amount of time was also dedicated to preparing a SIRTF Legacy Science program, which unfortunately was not accepted, but in the process I have become familiar with the SIRTF instruments, and I expect to be heavily when they will become available.

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