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Water in Interstellar Medium and Circumstellar Disks

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Water in Interstellar Medium and Circumstellar Disks 1- Introduction ASTROBIOLOGY WINTER SCHOOL HAWAII - 2005 WATER IN INTERSTELLAR MEDIUM AND CIRCUMSTELLAR DISKS Cecilia Ceccarelli Laboratoire d’Astrophysique de l’Observatoire de Grenoble C.Ceccarelli : Water in circumstellar disks and interstellar medium 1 Astrobiology Winter School , Hawaii 2005 1- Introduction OUTLINE OF THE COURSE ASTROBIOLOGY • THREE KEY WORDS: 1- WATER 2- DEUTERATION 3- ORGANIC CHEMISTRY I.E. CHEMISTRY DURING THE FIRST PHASES OF STAR FORMATION C.Ceccarelli : Water in circumstellar disks and interstellar medium 2 Astrobiology Winter School , Hawaii 2005 1- Introduction OUTLINE OF THE COURSE 1. Introduction: the formation of a solar type star. 2- The chemistry in the ISM. Setting the stage 3- Observations of water in the ISM. 4- The deuteration in the ISM. 5- Observations of ices in protostellar environments. (AB) p F r r 6- Water in the outflow shocks. o o t m o p a 7- Water in the protostellar envelopes. l a c n l o e u 8- Ices general inventory and complexity. (AB) t d a r t y o s 9- The hot corinos a y s t 10- The protostellar disk phase e m t C.Ceccarelli : Water in circumstellar disks and interstellar medium 3 Astrobiology Winter School , Hawaii 2005 1- Introduction : the formation of a Sun-like star From a cloud to a protostar and protoplanetary system C.Ceccarelli : Water in circumstellar disks and interstellar medium 4 Astrobiology Winter School , Hawaii 2005 1- Introduction THE MILKY WAY : stars and star formation C.Ceccarelli : Water in circumstellar disks and interstellar medium 5 Astrobiology Winter School , Hawaii 2005 1- Introduction THE MILKY WAY : stars and star formation C.Ceccarelli : Water in circumstellar disks and interstellar medium 6 Astrobiology Winter School , Hawaii 2005 1- Introduction THE MILKY WAY : stars and star formation C.Ceccarelli : Water in circumstellar disks and interstellar medium 7 Astrobiology Winter School , Hawaii 2005 1- Introduction THE MOLECULAR CLOUDS: • Solar type stars forms in the coldest and densest regions of our Galaxy: the Molecular Clouds (the star nurseries). • The Molecular Clouds (MCs) are (the densest) components of the so- called InterStellar Medium (ISM), i.e. the material in between the stars. The ISM is constituted by GAS and DUST. • MC are « molecular » because the InterStellar FUV photons (emitted by the Galaxy stars), which photodissociate the molecules, do not penetrate. When molecules form, they cool down efficiently the gas, which becomes therefore cold (30 K), and dense (>103cm-3). • The gas in MCs is formed of molecules, atoms and electrons. -> lines • The dust in MC is formed by small (~10-5cm) grains of silicates, graphite and amorphous carbon, surrounded by mantles of dirty water ices. -> continuum C.Ceccarelli : Water in circumstellar disks and interstellar medium 8 Astrobiology Winter School , Hawaii 2005 1- Introduction THE LIFECYCLE OF THE GALAXY Gas and Dust are cycled through ISM: the gas and dust injected by dying stars are mixed with ISM gas and dust, processed through various phases of ISM clouds and eventually condense into newly formed stars and planetary systems. There is a complex feedback between STAR FORMATION and the ISM. protostar dying star molecular cloud diffuse cloud C.Ceccarelli : Water in circumstellar disks and interstellar medium 9 Astrobiology Winter School , Hawaii 2005 1- Introduction STAR FORMATION IN MOLECULAR CLOUDS Young stellar objects (YSOs) are found in the denser regions of molecular clouds. The left Figure shows the example of the ρ Ophiuchus molecular cloud, as mapped by CO 1-0 line emission, overlapped with the position of the YSOs known in 1990. They were sources undetected in the optical, and only visible in the IR and FIR. C.Ceccarelli : Water in circumstellar disks and interstellar medium 10 Astrobiology Winter School , Hawaii 2005 1- Introduction THE FORMATION OF A SUN-LIKE STAR Low mass protostars form from the (slow: ~10Myr ?) collapse of dense fragments of molecular clouds, the so-called pre-stellar cores. Once the free-fall collapse sets on, an hydrostatic core is formed (likely) at the center of the collapsing core, surrounded by a massive (of few solar masses) envelope, which totally obscures the forming star. At the same time, due to the initial rotation of the core, a disk is formed and an important fraction of the infalling matter is ejected back towards the ISM, in the so- called outflows. C.Ceccarelli : Water in circumstellar disks and interstellar medium 11 Astrobiology Winter School , Hawaii 2005 1- Introduction THE FORMATION OF A SUN-LIKE STAR As the time passes, the inner hydrostatic core accretes matter from the infalling envelope, whose mass decreases along, until the temperature of the newborn star reaches the D-burning limit, and the star appears in the visible. At first, the star is surrounded by a residual envelope + a young/gas rich disk. With time, the envelope completely dissipates, and only the disk remains visible. The disk slowly (10 Myr?) evolves: gas is lost and dust coagulates into planetesimal, which eventually will form the planets of a C.Ceccarelli : Water in circumnsetewllalry di s ks apnlda interstteallrary m esdyiusmtem. 12 Astrobiology Winter School , Hawaii 2005 1- Introduction THE FORMATION OF A SUN-LIKE STAR C.Ceccarelli : Water in circumstellar disks and interstellar medium 13 Astrobiology Winter School , Hawaii 2005 1- Introduction PROTOSTAR CLASSIFICATION Observational and theoretical studies of the star formation process have had a giant leap forward in the last 20 years. First, the IRAS satellite, flown in 1984, discovered thousands of FIR sources, previously unkwon. Later on, the large mm/submmtelescopes in the 90s (IRAM-30m, JCMT-15m and CSO-10m) discovered even colder sources. Based on the observed continuum Spectral Energy Distribution (SED), the following classification of YSOs emerged: •Class 0 sources, which are only visible in the submm/mm wavelenghts: likely these sources represent the first stages of the protostar formation. The inner object is hidden by the large dusty envelope, from which the object likely accretes. The « bolometric » temperature Tbol is aroun 10-30 K. C.Ceccarelli : Water in circumstellar disks and interstellar medium 14 Astrobiology Winter School , Hawaii 2005 1- Introduction PROTOSTAR CLASSIFICATION •Class I sources, detected in the IR, with a SED flat from the NIR to FIR wavelenghts: these sources represent probably a later stage than Class 0. The envelope starts to dissipate and becomes less thick, giving rise to larger Tbol, ~50 K. •Class II sources, detected in the visible, known as T Tauri (M<2Mo) and Herbig AeBe (M~2-3Mo) stars, and with an IR to FIR excess. Most of the envelope has disappeared, and the IR excess is due to a dust+gas disk. •Class III sources, like Class II sources are detected in the visible, but they have a very small NIR excess. The envelope is definitively dissipated. A cold disk is all it remains. C.Ceccarelli : Water in circumstellar disks and interstellar medium 15 Astrobiology Winter School , Hawaii 2005 1- Introduction THE PRE-STELLAR CORES Pre-stellar cores (PSC) were discovered as black spots on the optical plates, testifying the presence of dense patches of cold material. PSCs have been lately studied in the millimeter continuum, as well as in many molecular tracers. The figure below is a nice example of a PSC, B68, in three molecular lines, overlapped to the continuum emission. Note the different location of the peak emission in the different tracers. C.Ceccarelli : Water in circumstellar disks and interstellar medium 16 Astrobiology Winter School , Hawaii 2005 1- Introduction THE CLASS 0 SOURCES The Class 0 sources were discovered about 10 years ago as mm continuum sources, with no IR or FIR counterparts. The prototype of the Class 0 sources is IRAS16293-2422 (IRAS16293), in the ρ Oph complex. Because of its vicinity (120pc) and relatively large envelope (~3Mo), it is the best studied Class 0 source. The figure on the left shows a map of the H2CO emission around IRAS16293. The 2 0 two stars are the two YSOs of the region, 0 2 . l IRAS16293 (on the right) and 16293E a t e (on the left). Note that while IRAS16293 n s t « shines » in H2CO, the other source, e t s colder and likely younger, does not. In a C addition to the envelope of IRAS16293 there are other peaks of H2CO emission. They are associated with the shocks at the interface of the gas outflowing from IRAS16293 and the parental cloud gas. Highly collimated and fast outflowing gas, giving rise to « bright » shocks, are indeed a distinct propriety of Class 0 sources. C.Ceccarelli : Water in circumstellar disks and interstellar medium 17 Astrobiology Winter School , Hawaii 2005 1- Introduction Summary • Stars form in the Molecular Clouds, the densest (>103cm-3) and coldest (<30K) regions of the Galaxy. • Fragments of MCs, the Pre-Stellar Cores, slowly collapse under the gravitational force, to form Protostars. • The youngest protostars are the so-called Class 0 sources, formed by massive (few Mo) envelopes, plus a disk, plus an outflow, plus the central star. • In the final stage, the protostars are only surrounded by Protoplanetary Disks, from which planets may eventually form. C.Ceccarelli : Water in circumstellar disks and interstellar medium 18 Astrobiology Winter School , Hawaii 2005 1- Introduction THE NAKED DISK PHASE From a gas rich to a debris disk. C.Ceccarelli : Water in circumstellar disks and interstellar medium 19 Astrobiology Winter School , Hawaii 2005.
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