The lower density gas around dense cores Clumps, interclump medium and the connection between molecular ices and gas-phase chemistry Òscar Morata, Kuan Yi-Jehng National Taiwan Normal University, Taiwan Academia Sinica Institute of Astronomy and Astrophysics, Taiwan ALMA-JT W ORKSHOP , D ECEMBER 5, 2008 Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 1 / 19
Outline Introduction 1 Clumps Chemistry Ices Single-dish results 2 Proposed project 3 Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 2 / 19
Scientific goals We aim to study: the structure and chemical properties of transient clumps found in dense cores of molecular clouds, the inter-clump gas that surround them and follow the depletion of molecules onto grains in lines of sight where ices were found. Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 3 / 19
Scientific goals We aim to study: the structure and chemical properties of transient clumps found in dense cores of molecular clouds, the inter-clump gas that surround them and follow the depletion of molecules onto grains in lines of sight where ices were found. Why: To constrain gas-grain chemical models and the earliest stages of star formation/chemical evolution. to show the enrichment (if any) of the more diffuse gas due to cycling of material Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 3 / 19
Scientific goals We aim to study: the structure and chemical properties of transient clumps found in dense cores of molecular clouds, the inter-clump gas that surround them and follow the depletion of molecules onto grains in lines of sight where ices were found. Why: To constrain gas-grain chemical models and the earliest stages of star formation/chemical evolution. to show the enrichment (if any) of the more diffuse gas due to cycling of material We propose to map the emission of several molecular tracers in the transitional regions between denser clumps and the inter-clump medium, using the 12-m array, complemented with the ACA. Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 3 / 19
Clumps in dense cores CCS emission in TMC-1 (Peng et al. 1998) n H 2 ∼ a few × 10 4 cm − 3 , masses 0.04–0.6 M ⊙ . only 5 of 45 clumps appear gravitationally unstable to collapse Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 4 / 19
Clumps in dense cores (cont.) BIMA FCRAO Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 5 / 19
Clumps in dense cores (cont.) Morata et al. (2003) HCO+ N2H+ CS 11 17 11 17 11 17 16 16 16 N N N DECLINATION (J2000) DECLINATION (J2000) DECLINATION (J2000) 15 15 15 W W W E E E 14 14 14 S S S 13 13 13 12 12 12 19 21 00 20 58 56 54 52 50 48 46 44 19 21 00 20 58 56 54 52 50 48 46 44 19 21 00 20 58 56 54 52 50 48 46 44 RIGHT ASCENSION (J2000) RIGHT ASCENSION (J2000) RIGHT ASCENSION (J2000) Clumpier structure is apparent But, we lose 90% of the flux! Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 5 / 19
Clumps in dense cores (cont.) 15 clumps, all resolved Using clump analysis technique (Williams et al. 1994) ◮ Sizes 0.03–0.09 pc ◮ M ∼ 0.02–0.36 M ⊙ ◮ n ∼ 0.6—4.6 × 10 4 cm − 3 (subthermalized) ◮ ∆ V ∼ 0.31–0.65 km s − 1 Morata et al. (2005) Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 6 / 19
Clumps in dense cores (cont.) 15 clumps, all resolved Using clump analysis technique (Williams et al. 1994) ◮ Sizes 0.03–0.09 pc ◮ M ∼ 0.02–0.36 M ⊙ ◮ n ∼ 0.6—4.6 × 10 4 cm − 3 (subthermalized) ◮ ∆ V ∼ 0.31–0.65 km s − 1 Morata et al. (2005) Spatial segregation N-S ◮ North - more clumps, smaller and less massive ◮ South - fewer clumps, but the largest and more massive one ◮ N 2 H + and NH 3 (low-res) in the southern region Probably most of them are transient (Morata et al. 2005) Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 6 / 19
Chemical Models (Garrod et al. 2004; 2006) Contracting and expanding density profile (2 Myr) (Falle & Hartquist 2002) Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 7 / 19
Chemical Models (Garrod et al. 2004; 2006) Contracting and expanding density profile (2 Myr) (Falle & Hartquist 2002) Falle & Hartquist (2002) Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 7 / 19
Chemical Models (Garrod et al. 2004; 2006) Contracting and expanding density profile (2 Myr) (Falle & Hartquist 2002) Molecules freeze-out during contraction; desorb during expansion Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 7 / 19
Chemical Models (Garrod et al. 2004; 2006) Contracting and expanding density profile (2 Myr) (Falle & Hartquist 2002) Molecules freeze-out during contraction; desorb during expansion Simulation of the maps Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 7 / 19
Chemistry of the gas The presence of transient clumps would have consequences for the physical and chemical evolution of these regions (Williams & Viti 2002): Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 8 / 19
Chemistry of the gas The presence of transient clumps would have consequences for the physical and chemical evolution of these regions (Williams & Viti 2002): the chemistry would be mainly young Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 8 / 19
Chemistry of the gas The presence of transient clumps would have consequences for the physical and chemical evolution of these regions (Williams & Viti 2002): the chemistry would be mainly young it would halt the processes of freeze-out of molecules onto dust (no complete depletion of molecules from the gas-phase). Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 8 / 19
Chemistry of the gas The presence of transient clumps would have consequences for the physical and chemical evolution of these regions (Williams & Viti 2002): the chemistry would be mainly young it would halt the processes of freeze-out of molecules onto dust (no complete depletion of molecules from the gas-phase). the cycling process produces a general enrichment of the clouds , some molecules are significantly enhanced by it (even even after core re-expansion) Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 8 / 19
Chemistry of the gas The presence of transient clumps would have consequences for the physical and chemical evolution of these regions (Williams & Viti 2002): the chemistry would be mainly young it would halt the processes of freeze-out of molecules onto dust (no complete depletion of molecules from the gas-phase). the cycling process produces a general enrichment of the clouds , some molecules are significantly enhanced by it (even even after core re-expansion) the background gas if fairly diffused, but chemically enriched. It could account for the variety of chemistries in diffuse clouds. Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 8 / 19
The connexion with ices Ices in dense molecular material detected by absorption features in the IR Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 9 / 19
The connexion with ices Ices in dense molecular material detected by absorption features in the IR H 2 O ice appears at fairly low extinctions, A V = 3 . 3 in Taurus (Adamson et al. 1988); CO-ice at A V ≥ 6 (Whittet et al. 1988) Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 9 / 19
The connexion with ices Ices in dense molecular material detected by absorption features in the IR H 2 O ice appears at fairly low extinctions, A V = 3 . 3 in Taurus (Adamson et al. 1988); CO-ice at A V ≥ 6 (Whittet et al. 1988) Increasing abundance of ices with A V . Formation/coagulation of CO and H 2 O ices with A V Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 9 / 19
The connexion with ices Ices in dense molecular material detected by absorption features in the IR H 2 O ice appears at fairly low extinctions, A V = 3 . 3 in Taurus (Adamson et al. 1988); CO-ice at A V ≥ 6 (Whittet et al. 1988) Increasing abundance of ices with A V . Formation/coagulation of CO and H 2 O ices with A V N( solid -CO 2 ) similar to N( solid -CO) (Nummelin et al. 2001) Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 9 / 19
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