Vincent Minier

Toute la vie d'une etoile est determinee par sa masse. C'est pourquoi les astrophysiciens s'interessent maintenant aux moments de la naissance des astres, recherchant ce qui definit leur masse. De nouveaux instruments d'observation, comme le telescope spatial Herschel, vont participer a cette etude demographique.

We report on recent multi-scale observational stud-ies of the earliest stages of high mass (>8 M) star formation using methanol MASERs as astronomical probes. Methanol masers can provide unique informa-tion about densely populated, embedded protoclusters in which precursors of O and B stars form. Tracers of high mass star-forming complexes in the Galactic plane: The brightest methanol masers are detected in radio frequencies at 6.7 and 12.2 GHz and are not affected by extinction in high mass star-forming regions. They were originally detected in the environment of very active star-forming complexes of HII regions a decade ago [1]. Since their discovery, more than 500 methanol maser sites have been located in the Galactic plane through searches toward IRAS colour selected sources [2], OH and H 2 O masers [3] as well as through unbiased full-sampling surveys [4,5]. Interestingly, 6.7-GHz methanol masers have not been detected toward low mass star-forming regions despite very sensit...

The implementation of Herschel as one of the most powerful space telescopes ever built was possible thanks to key inventions and innovations. They result from a long-term process, leading to the required scientific performances and an efficient mission management. The innovation process started during the design of the mission and finished with the final breath of the cryostat. This chapter examines the concept of innovation and apply it to the system design process and management that shaped the success of the Herschel mission.

Peter Barnes (U Sydney), Kate Brooks (ATNF), Michael Burton (UNSW), Maria Cunningham (UNSW), John Dickey (U Tasmania), Phil Edwards (ISAS), Ron Ekers (ATNF), Yasuo Fukui (U Nagoya), Annie Hughes (Swinburne U), Ilana Klamer (U Sydney / ATNF), Vincent Minier (CEA Saclay), Erik Mueller (ATNF), Juergen Ott (ATNF), Bob Sault (ATNF), Mark Thompson (U Hertfordshire), Andrew Walsh (UNSW), Tony Wong (UNSW / ATNF).

Here we describe the various elements of the Herschel cryogenic concept and its evolution since the first proposal submitted to ESA in 1982, following developments from previous cryogenic missions, and continuous adaptation to the evolving needs of the focal plane instruments, ending in a substantially different concept. A temperature below 2 K was necessary for the Herschel instruments to achieve the required sensitivity. Herschel therefore carried a liquid He cryostat of 2300 l capacity, with the liquid in the superfluid phase at a temperature of 1.6 K. This temperature was optimum for the photoconductive detectors of the PACS spectrometer and for the SIS mixers of the heterodyne HIFI instrument. The detectors of the PACS camera and of the SPIRE camera and spectrometer were bolometers, which required an even lower operating temperature. To achieve this, PACS and SPIRE had their own 3He sorption coolers to reach a temperature of 0.3 K. The telescope was launched warm and, once in o...

This chapter outlines the diagnostic importance of the far-infrared and submillimetre spectral range and presents the evolution of the mission’s science objectives from the time of its original conception and goes on to describe the results and scientific achievements of Herschel. It shows how the opening of a spectral window, previously poorly studied, has changed our view of the most important components of our Universe, from galaxies and stars and the processes of their formation to planetary systems and the ‘water trail ’. The last section is a bibliometric analysis of the scientific return of Herschel and how it has interconnected the scientific community, illustrated by a new and original co-citation mapping. The quantity and quality of the data coming from Herschel during its almost 4-year observing lifetime will remain unique for a long time, casting new light on astronomical phenomena and processes never seen before.

The newly upgraded Australia Telescope Compact Array (ATCA) at millimetre wavelengths is the first millimetre interferometer to be built in the Southern Hemisphere. The full array will be operational in 2004-2005 and will provide arcsec angular resolution at 3 mm and 12 mm. This will be a unique instrument to study at high angular resolution the interstellar chemistry and more generally the star formation process, especially in the bulk of the galactic plane and in the Magellanic Clouds. The upgraded ATCA will also be an excellent tool to detect dust emission from nearby protoplanetary disks. In this paper I will present the first results from the upgraded ATCA at 3 mm and 12 mm. The result review will cover the topics of massive star formation and hot molecular cores dust emission from star-forming regions and detection of protoplanetary disks.

ABSTRACT We illustrate the status of the international infra-red telescope IRAIT-ITM, a project developed thanks to an Italian- Spanish-French collaboration and now sited at the Dome C Antarctic base. The telescope and its subsystems were installed at DomeC by a team of Italian and French scientists. The 80 cm telescope is placed on a small snow hill next to a laboratory of astronomy. The operations started in January 2013, with the Nasmyth focal planes equipped with the midinfrared camera AMICA for 1.25 to 25 μm and the sub-millimetre camera CAMISTIC for observation of the sky noise at 200 and 350 μm using a bolometer camera. During 2013 the two winter-overs worked mainly on technological duties, learning how to operate the telescope, while temperatures decreased down to -80°C. The cryogenic systems could be operated respectively at 0.25K and 4K at all times, with satisfactory use of the heat from the compressors of the cryocoolers to the warm-up the laboratory through a closed loop glycol system. The lack of tests and reliability in extreme conditions of some components and difficult access to maintenance hampered regular observations below -50°C. Using the lessons of this first winter, the summer team improves the robustness of the failing systems and ease the access to maintenance. The winter 2014 is the first one with programmed observations. Because of power restrictions, the two instruments are used each one at a time by periods of 2 weeks. The Camistic camera continues to observe the stability of the sky at a fixed altitude in chopping mode and performs skydips. The TCS is being upgraded in order to prepare the next summer season with extensive observations of the sun with Camistic.

Astronomical observations at sub-millimetre wavelengths are limited either by the angular resolution of the telescope or by the sensitivity and field of view of the detector array. New generation of radio telescopes, such as the ALMA-type antennas on Chajnantor plateau in ...

This chapter reviews the development of the Herschel telescope and shows how the initial concept of FIRST (renamed Herschel in 2000) was ‘undecidable’ (not capable of being told feasible or unfeasible) due to the poor knowledge of how to build it following its introduction in the Horizon 2000 long-term plan. It describes the competition between various industrial concepts, the abandoned NASA concept and how the development of silicon carbide (SiC) mirror technology made it possible to build the largest telescope then ever flown, just fitting in an Ariane 5 fairing. It offers a reflection on the need of major innovations requiring advanced material technologies and innovative mirror structures to go from Herschel to the next generation of high-resolution far-infrared space telescopes.

This book has considered the dynamics of innovation in space science missions. Making Herschel an outstanding success was not a simple task and was not the result of a smooth and flawless process. We have addressed the essence of innovation and of technicity from a philosophical standpoint including tools and concepts borrowed from humanities and social sciences (sociology, economy, C-K theory, etc.). Specific patterns were applied to characterise some technological and social features of the creativity of scientists and engineers. The notion of an ‘instrumental community ’ has been coined and adopted in order to understand the effect Herschel had on the scientific field, using an original representation based on the bibliometric analysis of a co-citation network. While confirming the value of the approach taken by ESA in formulating its long-term plans, we conclude that the level of technology readiness and qualification was not a relevant discriminator for deciding to select FIRST...

This introduction presents some of the characteristics of space missions and considers why they are stimulating for a study on innovation and why the Herschel Space Observatory offers a particularly rich example for engaging an epistemology of innovation. Our socio-technological study assesses the historical, structural and sociological aspects, which are discussed in the book. The first three chapters describe the conditions which framed the Herschel story from invention through development, in-orbit operation and scientific discoveries. The second part of the book analyses the key innovations on which the main elements of Herschel relied and the complex management structure adopted among all partners involved. Finally, we discuss the role of innovation and of risk management in view of the need to foster creativity and ambition for the next generations of instruments.

ABSTRACT We present an implementation of ionization in order to study triggered star formation at the edge of HII regions. Our module is coupled with the grid-based hydrodynamic code Heracles. The geometry can be either plan-parallel or spheric, in one two or three dimensions. Cooling and heating of the gas due to ionization and recombination is explicitly treated allowing detailed studies of the thermal evolutions of HII regions. We present first tests of our method and discuss the effects of heating and cooling on these simple situations.

We present VLBI and BIMA observations of the Class II methanol maser source G 59.783+0.065. The methanol emission arises from the centre of a compact molecular core, supporting the view that methanol masers trace an early stage of massive star formation. The velocity spread of the masers is significantly larger than that of the parent molecular cloud, which is consistent with the methanol coming from a rotating structure within the molecular core. However, there is also weak evidence that the methanol is aligned with an outflow.

ABSTRACT We propose to image a small sample of 10 millimetre continuum sources identified in a 1.2mm continuum survey by Hill et al. (2005). These sources are devoid of typical indications of massive star formation such as methanol maser and radio continuum sources. Subsequent submillimetre continuum observations, Parkes ammonia observations and spectral energy distribution analysis indicate that these mm-only sources have characteristics similar to sources known to be forming massive stars, making them excellent candidates for early stage protostars. We are now proposing to image a small sample of these protostar candidates in 3 and 7mm continuum using the CABB system on the ATCA. These observations will allow resolution of the cores into individual components, study of their spectral index and their evolution; determination of their radial density structure and insight into the conditions required for fast protostellar collapse; determination of the clump mass fraction of the main mm-only complex as well as the individual components; in addition to providing insight into the turbulence of the cores. Ultimately these observations allow characterisation of the mm-only cores and insight into their star formation status and evolution.

Introduction Class II methanol masers appear to be closely associated with newly formed massive stars (Menten 2002). These stars are still deeply embedded in their natal molecular cloud and thus cannot be observed directly. Hence the methanol masers are a useful tool for ...

This thesis is the result of work undertaken between 2002 and 2006 in the Department of Astrophysics and Optics at the University of New South Wales. The reduction and analysis of data in this thesis utilised a multitude of software packages. The SIMBA data were reduced and analysed ...

The CAMISTIC project aims to install a filled bolometer-array camera with 16x16 pixels on a small telescope (e.g. IRAIT) at Dome C and open the 200-mum (i.e. THz) windows for ground-based observations. CAMISTIC will be located at about 500 m from the base, with very reduced access. Autonomous and automated cryogenic devices specifically designed for the harsh conditions in Antarctica will therefore be needed. We plan to demonstrate the reliability of a novel cryogenic system with all static parts placed next to cryostat at outer temperature conditions and a warmed cabinet for compressors, motors and valves. Extensive tests in wintering condition will be performed before expedition. CAMISTIC will be equipped with novel bolometer technology. The filled bolometer array with a monolithic grid of 256 pixels was designed by CEA for the PACS far-IR/submm imager on the Herschel Space Observatory and similar arrays are currently developed for the ArTéMiS submm camera on ground-based telescopes. A prototype camera operating in the 450 mum atmospheric window has successfully been tested in March 2006 on the KOSMA telescope. CAMISTIC will perform site testing on the atmospheric opacity and sky noise at 200-450 mum and then open the way for future, large submm telescopes at Dome C. In the future, placed on a 12-m single-dish telescope at Dome C, a bolometer camera with ~10000 pixels at 200-450 mum will be particularly powerful to undertake wide field surveys of star-forming complexes in our Galaxy as well as deep field surveys of dust-enshrouded high-redshift galaxies in the early Universe.

ABSTRACT We propose a millimetre spectral line study of southern massive star formation sources that were previously identified in a millimetre continuum emission survey on the SEST. These sources are found offset from, and are devoid of, methanol maser and UC Hriptsize II regions, which typically trace young massive stars. In subsequent SCUBA observations on the JCMT, these mm-only sources were also found to be associated with submillimetre continuum emission, confirming their association with cold, deeply embedded cores. Little or no information is currently available pertaining to the chemistry of these cores. The objective of this study is to probe the physical and chemical state of a small sample of the mm-only cores in order to improve our understanding of these objects and their role in the formation of massive stars. With Mopra we will obtain spectral information which will reveal the gas kinematics as well as the gas and chemical properties of the cores.

ABSTRACT The catalogue of the 6.7GHz methanol masers comprises all detected sources since the discovery of this intense radiation. For every source we report name, right ascension and declination in J2000, galactic coordinates, vlsr, velocity range, peak flux, galactocentric and heliocentric distances (near and far), IRAS and MSX associations if any, usual name, detected methanol masers at 12, 44, 85.5, 86.5, 95, 107, 108, 156GHz, reference of the 6.7GHz detection and reobservation. (2 data files).

The Onsala VLBI group has been conducting an extensive study of the Northern hemisphere methanol masers using the European VLBI Network (EVN) and the VLBA since early 1997. In parallel, a blind survey of the Galactic plane has been undertaken in order to discover new 6.7 GHz methanol masers using the Onsala-25m antenna, as well as a search for new class II methanol maser lines at higher frequencies (85-112 GHz). This thesis reports the results in these three observational projects and shows that methanol masers are excellent tracers of early stages in the process of massive star formation. VLBI observations of 6.7 and 12.2 GHz methanol masers toward fifteen star-forming regions (namely IRAS20126+4104, NGC7538, S252, W75N, W48, G31.28+0.06, S231, S255, S269, MonR2, G9.62+0.20, CepA, W51, G59.78+0.06 and G29.95-0.02) have given four main results. First, the majority of the observed methanol maser sites do not coincide spatially with UC HII regions. Instead, the methanol maser sites may trace a stage of massiveion prior to the development of observable ionised regions. Secondly, in many cases the methanol maser components form a line with a linear velocity gradient along it, which is consistent with a rotating disk seen edge-on. The masers partially delineate the edge-on disk and probably lie only in front of the star. There is also some evidence for methanol masers tracing outflows in a few sources. Preliminary proper motion studies of one source, G9.62+0.20, show that the maser components lying in the lines are moving apart. Finally, the intrinsic structures of the masing regions consist of a core and a halo. The first results of the unbiased survey after 35 square degrees observed toward the Galactic plane, show a poor detection rate of new methanol masers in the regions far away from the galactic centre. Instead, most of the detected methanol maser sites are located in the inner part of the Galactic plane. This confirms that the distribution of methanol maser sources is correlated to the distribution of massive star-forming regions. Some methanol maser sites do not exhibit any traditional emission of young massive stars, indicating that the methanol masers could trace deeply embedded massive protostars. The search for new methanol maser lines in the frequency range 85-112 GHz shows that strong thermal emissions are present at the frequencies of maser line candidates. Intense masers are only observed at 107 GHz. Likely detections of new methanol masers at 85.5, 94.5, 108.9 and 111.3 GHz are reported. In summary, the collected evidence resulting from multi-wavelength observations at high and low resolutions, demonstrates that class II methanol masers are directly involved in the earliest process of massive star formation and are potentially powerful tracers of stellar evolution.

Methanol masers have now been recognised as a likely exclusive signpost of massive star formation. More interestingly radio observations toward a large source sample have shown that methanol masers are isolated from traditional signposts of massive star formation such as ...

``Radio astronomy is the study of the universe by observing electromagnetic radiation after it has been amplified. The use of amplifiers that preserve the oscillatory character of radiation - the phase information - is the mark of Radio astronomy.'' Thus, the development of low noise amplifiers for microwave and millimeter wavelengths is a major part of Radio astronomy as important as the observations themselves. This technical report involves those two aspects of Radio astronomy, the observational and technical aspects. In the first part, observations of methanol masers in massive star forming regions using Very Long Baseline Interferometry (VLBI) are presented. The second part concerns the realization of low noise amplifiers using in a radio camera. Recent observations have confirmed that the methanol masers are powerful tools for probing the regions of massive star formation. The methanol masers fall in two distinct classes related to their location in the star forming regions. Class I methanol masers are observed offset far away from the UC HII region emission peak. They are certainly collisionally pumped and may occur in the interface between high velocity gas outflows and the ambient molecular material. Class II methanol masers coincide with the UC HII region emission. They may be radiatively pumped by FIR radiation from the dust grains and reside either in spherical layers surrounding the UC HII regions or in circumstellar discs. The maser spots are usually compact (~1-10 AU) and lie in region of physical conditions n(H)~104-108 cm-3 and T=100-1000 K. CH3OH may be produced by hydrogenation of CO on the surface of the icy mantles of the dust grains . The methanol is then injected in the molecular gas by evaporation of the ice (n(H)=106 cm-3, T=100-300 K). In this report we present VLBI observations of 6.7 and 12.2 GHz methanol masers in the star forming regions NGC7538, W75N and S252. Our results show the existence of two groups of masers in NGC7538. The first group exhibits a linear velocity gradient and forms a line in our VLBI map which is consistent with a rotating disc of masers seen edge-on around a massive star. The second group of masers are blueshifted with respect to the first group and lie in a conical region south of the inferred disc. We argue that these masers probably arise in an outflow emerging approximately perpendicularly to the disc. We find that the maser positions at 6.7 and 12.2 GHz are coincident and those of the second group correspond approximately to the absolute positions of NH3, H2CO and OH masers associated with the radio-continuum and infrared source NGC7538-IRS1. In addition we find similar evidence for circumstellar discs of masers in W75N and S252. For these three sources associated with ultra compact HII regions, from the linear velocity gradients and assuming that the central protostars are massive, we derive that the radii of the circumstellar discs are in the range 300-1200 AU which is typical of protoplanetary discs. In the second part, we present the design and realization of 4 GHz cryogenic low noise amplifiers used as IF amplifiers in a radio-camera receiver (SISYFOS project) which will be installed in the Onsala 20m millimeter wave telescope. The requirements of the SISYFOS project at cryogenic temperature are a minimum gain of 25 dB and noise equivalent temperature less than 10 K over the frequency range 3.4-4.6 GHz. Because of its low noise and high gain properties, the MGF4310E series super low noise HEMT from Mitsubishi have been selected to satisfy these requirements. We show that a very simple input design using a high impedance series line viewed as a series inductor provides good matching over a broad bandwidth while ensuring the stability of the amplifier. The minimum noise equivalent temperature and gain of the amplifier measured at cryogenic ambient temperature over the specified bandwidth are 7 K and 28 dB respectively.

We propose an SiO, HCN/HNC and HCO+ spectral line study of southern massive star formation sources that were previously identified in a millimetre continuum emission survey on the SEST. These sources are found offset from and devoid of methanol maser and an UC HII sources which typically trace young massive stars. Subsequent SCUBA observations on the JCMT reveal them to be associated with submillimetre continuum emission, confirming their association with cold, deeply embedded objects. Recent CO and CS observations using the Mopra telescope reveal them to be rich in molecular species. We are seeking complementary observations in both SiO, HCN/HNC and HCO+ species to aid our understanding of these cores and their role in the formation of massive stars. We will attempt to identify whether these cores display evidence of mssive star formation and whether they have similar characteristics to sources with a methanol maser and/or UC HII region. Ultimately we will address whether these cores are indeed forming massive stars.

ABSTRACT This paper reviews recent results in the field of massive star formation in connection with methanol masers. 6.7 and 12.2 GHz methanol masers are used as probes to investigate the early phases of massive star formation and appear as excellent tracers of the youngest massive-star forming regions. An evolutionay sequence for massive star formation is proposed in which methanol masers occur in cold dust condensations, hot molecular cores and hyper compact HII regions, i.e. at the earliest stages of the star-forming process. New millimetre continuum observations using SIMBA are also presented and support our evolutionay scenario for massive star formation. Finally, further work at millimetre wavelengths for continuum and spectral lines using the next generation of ground-based interferometer is discussed.