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The lower density gas around dense cores Clumps, interclump medium and the connection between molecular ices and gas-phase chemistry scar Morata, Kuan Yi-Jehng National Taiwan Normal University, Taiwan Academia Sinica Institute of Astronomy

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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 WORKSHOP, DECEMBER 5, 2008 Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 1 / 19

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Outline

1

Introduction Clumps Chemistry Ices

2

Single-dish results

3

Proposed project

Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 2 / 19

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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

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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

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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

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Clumps in dense cores

CCS emission in TMC-1 (Peng et al. 1998) nH2 ∼ a few ×104 cm−3, masses 0.04–0.6M⊙.

  • nly 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

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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

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Clumps in dense cores (cont.)

Morata et al. (2003)

DECLINATION (J2000) RIGHT ASCENSION (J2000) 19 21 00 20 58 56 54 52 50 48 46 44 11 17 16 15 14 13 12 CS S E W N DECLINATION (J2000) RIGHT ASCENSION (J2000) 19 21 00 20 58 56 54 52 50 48 46 44 11 17 16 15 14 13 12 S E W N HCO+ DECLINATION (J2000) RIGHT ASCENSION (J2000) 19 21 00 20 58 56 54 52 50 48 46 44 11 17 16 15 14 13 12 S E W N N2H+

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

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Clumps in dense cores (cont.)

Using clump analysis technique (Williams et al. 1994) Morata et al. (2005)

15 clumps, all resolved

◮ Sizes 0.03–0.09 pc ◮ M ∼ 0.02–0.36 M⊙ ◮ n ∼0.6—4.6×104

cm−3 (subthermalized)

◮ ∆V ∼ 0.31–0.65

km s−1

Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 6 / 19

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Clumps in dense cores (cont.)

Using clump analysis technique (Williams et al. 1994) Morata et al. (2005)

15 clumps, all resolved

◮ Sizes 0.03–0.09 pc ◮ M ∼ 0.02–0.36 M⊙ ◮ n ∼0.6—4.6×104

cm−3 (subthermalized)

◮ ∆V ∼ 0.31–0.65

km s−1

Spatial segregation N-S

◮ North - more clumps, smaller and less massive ◮ South - fewer clumps, but the largest and more massive one ◮ N2H+ and NH3 (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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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The connexion with ices

Ices in dense molecular material detected by absorption features in the IR H2O ice appears at fairly low extinctions, AV = 3.3 in Taurus (Adamson et al. 1988); CO-ice at AV ≥ 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

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The connexion with ices

Ices in dense molecular material detected by absorption features in the IR H2O ice appears at fairly low extinctions, AV = 3.3 in Taurus (Adamson et al. 1988); CO-ice at AV ≥ 6 (Whittet et al. 1988) Increasing abundance of ices with AV. Formation/coagulation of CO and H2O ices with AV

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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The connexion with ices

Ices in dense molecular material detected by absorption features in the IR H2O ice appears at fairly low extinctions, AV = 3.3 in Taurus (Adamson et al. 1988); CO-ice at AV ≥ 6 (Whittet et al. 1988) Increasing abundance of ices with AV. Formation/coagulation of CO and H2O ices with AV N(solid-CO2) 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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The connexion with ices

Ices in dense molecular material detected by absorption features in the IR H2O ice appears at fairly low extinctions, AV = 3.3 in Taurus (Adamson et al. 1988); CO-ice at AV ≥ 6 (Whittet et al. 1988) Increasing abundance of ices with AV. Formation/coagulation of CO and H2O ices with AV N(solid-CO2) similar to N(solid-CO) (Nummelin et al. 2001) The amount of C and O in ice mantles is a fair fraction of the total gas phase abundance of C and O (at least 30% in Taurus)

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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The connexion with ices

Ices in dense molecular material detected by absorption features in the IR H2O ice appears at fairly low extinctions, AV = 3.3 in Taurus (Adamson et al. 1988); CO-ice at AV ≥ 6 (Whittet et al. 1988) Increasing abundance of ices with AV. Formation/coagulation of CO and H2O ices with AV N(solid-CO2) similar to N(solid-CO) (Nummelin et al. 2001) The amount of C and O in ice mantles is a fair fraction of the total gas phase abundance of C and O (at least 30% in Taurus) Therefore, in order to understand the chemistry in molecular dense cores, we must understand the abundances of molecules in the gas and condensed phases.

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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The connexion with ices

Ices in dense molecular material detected by absorption features in the IR H2O ice appears at fairly low extinctions, AV = 3.3 in Taurus (Adamson et al. 1988); CO-ice at AV ≥ 6 (Whittet et al. 1988) Increasing abundance of ices with AV. Formation/coagulation of CO and H2O ices with AV N(solid-CO2) similar to N(solid-CO) (Nummelin et al. 2001) The amount of C and O in ice mantles is a fair fraction of the total gas phase abundance of C and O (at least 30% in Taurus) Therefore, in order to understand the chemistry in molecular dense cores, we must understand the abundances of molecules in the gas and condensed phases. But, very few (or no) observations of the gas phase in the same regions where ices had been detected

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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Exploring the clump and inter-clump medium

Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 10 / 19

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Exploring the clump and inter-clump medium

CL8 CL1 Clump positions

Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 10 / 19

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Exploring the clump and inter-clump medium

CL8 CL1 Clump positions ICL1 ICL2 Inter-clump positions

Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 10 / 19

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Exploring the clump and inter-clump medium

CL8 CL1 Clump positions ICL1 ICL2 Inter-clump positions

  • bservations of 2 clump and 2

inter-clump positions 23 transitions observed with IRAM 30m:(CS, C2H, C3H2,

H13CO+, H2CO, HCN, NO, CN, SO, SO2)

Goals: to explore the chemical properties of the N and S regions, and the inter-clump medium Is there any recycling of material?

Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 10 / 19

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Exploring the clump-interclump medium (cont.)

Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 11 / 19

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Molecular emission in lines of sight with detected ices

Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 12 / 19

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Pipe Nebula

Alves, Franco & Girart (2008) Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 13 / 19

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Pipe Nebula

Alves, Franco & Girart (2008)

17h 26m 00s 25m 45s 30s 15s Right Ascension (2000)

  • 26o 50’

45 40 Declination (2000)

10%

Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 13 / 19

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Pipe Nebula

Alves, Franco & Girart (2008)

17h 26m 00s 25m 45s 30s 15s Right Ascension (2000)

  • 26o 50’

45 40 Declination (2000)

10%

17h 33m 00s 32m 45s 30s 15s 00s Right Ascension (2000)

  • 26o 20’

15 10 Declination (2000)

10%

Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 13 / 19

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Pipe Nebula

Alves, Franco & Girart (2008)

17h 26m 00s 25m 45s 30s 15s Right Ascension (2000)

  • 26o 50’

45 40 Declination (2000)

10%

17h 33m 00s 32m 45s 30s 15s 00s Right Ascension (2000)

  • 26o 20’

15 10 Declination (2000)

10%

17h 36m 15s 00s 35m 45s 30s 15s Right Ascension (2000)

  • 25o 40’

35 30 25 Declination (2000)

10%

Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 13 / 19

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Sources

12 sources (could be more)

◮ 5 in Taurus (Elias 3, Elias 13, Elias 16, Tamura 8, E034384) ◮ 1 in Orion (HH 43) ◮ 4 in the Pipe Nebula ◮ 1 in Aquila (LDN 673) Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 14 / 19

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Sources

12 sources (could be more)

◮ 5 in Taurus (Elias 3, Elias 13, Elias 16, Tamura 8, E034384) ◮ 1 in Orion (HH 43) ◮ 4 in the Pipe Nebula ◮ 1 in Aquila (LDN 673)

1′ × 1′ maps (min.), including the transition zones (mix of dense and more diffuse material) different resolutions and coverage of combined observations of 12-m array (∼ 1 − 3′′) and ACA (∼ 8 − 40′′). Sampling of different spatial scales. Discrimination of clumps and more extended material?

Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 14 / 19

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Frequencies

Band 3, Band 4 and Band 6

◮ 3 frequency settings in Band 3 ⋆ c-C3H2, HCS+, CCS, HCO+, CCH, HCN, H13CO+, HNC, HC3N,

N2H+

⋆ SO, HC3N, SO2 ⋆ HC3N, C18O, CCS, CN ◮ 1 frequency setting in Band 4 ⋆ HC3N, CS, NO, c-C3H2, N2D+ ◮ 3 frequency settings in Band 6 ⋆ C18O, H2CO, CN ⋆ CS, NO, HCS+ ⋆ H13CO+, SO, CCH, HCN, HCO+

spectral resolution: 0.25 km/s

Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 15 / 19

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Line intensities

Typical values: weak lines ∼ 0.1 K, strong lines ∼ 2 K required rms per channel:

◮ 0.025 K, for Bands 3 and 4 ⋆ at 110 GHz, 12-m array (beam ∼ 3′′): ∼ 2700s ⋆

7-m array (beam ∼ 19′′): ∼ 335s

◮ 0.035 K, for Band 6 ⋆ at 230 GHz, 12-m array (beam ∼ 1.5′′): ∼ 2700s ⋆

7-m array (beam ∼ 9′′): ∼ 360s

Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 16 / 19

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Time Estimations

if no mosaicking, and accounting ∼ 25% of the time for overheads,

◮ 1 hour per frequency setting ◮ 84 h for all sources and all frequency settings Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 17 / 19

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Some considerations

Most of the gas we want to observe is rather diffuse, and probably extended.

◮ 12-m can be useful to discriminate the clumps with high precision

and sensitivity

◮ With ACA and/or (powerful) single-dish observations –very good

sensitivity and high/medium angular resolution– we can be able to recover the more diffuse background emission (clump subtraction).

◮ Morata et al. (2003) found that part of the non-detected emission

with an interferometer can come for small weak clumps, difficult to detect with BIMA, but possibly with ALMA

Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 18 / 19

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Some considerations

Most of the gas we want to observe is rather diffuse, and probably extended.

◮ 12-m can be useful to discriminate the clumps with high precision

and sensitivity

◮ With ACA and/or (powerful) single-dish observations –very good

sensitivity and high/medium angular resolution– we can be able to recover the more diffuse background emission (clump subtraction).

◮ Morata et al. (2003) found that part of the non-detected emission

with an interferometer can come for small weak clumps, difficult to detect with BIMA, but possibly with ALMA

Sampling of different spatial scales.

◮ Possibility to follow clump evolution in different stages. ◮ Mapping with high-sensitivity with ACA, surrounding dense and

diffuse gas.

◮ Description of the chemistry with high detail Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 18 / 19

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Some considerations (cont.)

Combination of results from these lines to models of the chemical evolution of starless cores

◮ more detailed knowledge of the physical and chemical conditions of

the cores, evolutionary stage and depletion conditions of the cores

◮ better restriction of the parameters used by the chemical models ◮ sampling of the molecular abundances in the gas-phase and in the

solid-phase in the same regions

Òscar Morata, Kuan Yi-Jehng (NTNU, ASIAA) Lower density gas around dense cores ALMA-JT workshop, 5/12/2008 19 / 19