Comets with ALMAN. Biver, LESIA, Paris Observatory

I Comets composition

Chemical investigation and taxonomy

Monitoring of comet outgassing

II Mapping of cometary atmospheres

3-D Gas and dust jets

Physical properties of the coma and extended sources

Biver et al. 2002, E.M.P. 90, 323

I. ALMA and the composition of comets: Observing all types of comets (Kuiper Belt ones), new molecules

Measuring isotopic ratios in comets with ALMA

Hersant et al. 2001, ApJ 554, 391

13C/12C:terrestrial in > 6 cometsALMA: H13CN, 13CS, 13CO, 13CH3OH,…

34S/32S: ~ terrestrial in 2 cometsALMA: C34S, H2

34S

18O/16O:~ terrestrial in 4 comets (H2O)

15N/14N:~terrestrial in HCN Hale-Bopp buttwice higher in CN in > 4 comets?ALMA: HC15N, H15NC?

D/H: HDO/H2O 2× terrestrial in 3 comets, DCN/HCN 7× higher in Hale-Bopp

HDO with ALMA: in bright comets (Herschel more sensitive)

D/H in other molecules with ALMA (DCN, CH2DOH, HDCO, NH2D,…)

Cumulative number of molecules detected in comets as a function of abundance relative to water

Crovisier et al. 2004, A&A 418, L35

RA

DIO

Detection of ethylene glycol in comet C/1995 O1 (Hale-Bopp)together with 3 other new species (HC3N, HCOOCH3 and NH2CHO)

Crovisier et al. 2004, A&A 418, L35

Comparison of comets chemical composition with interstellar medium

Bockelée-Morvan et al. 2000, A&A 353, 1101

Progressive release of9 molecules by comet C/1995 O1 (Hale-Bopp)- As it approached the Sun(left: 1995-1997)- As it receded from the Sun(right:1997-2001)

Biver et al. 2002, E.M.P. 90, 5

ALMA: -Similar monitoring in less active comets (especially investigating transition between H2O and CO sublimation dominated regimes)

-Distant activity of comets: detection of CO outgassing in comets active at 5-15 AU(mag. 16-17 QCO=51026molec./s)

ALMA and the origins (composition) of comets (from line or dust integrated fluxes)

I.1 Relative abundance of 6-8 molecules in a wide diversity of comets: Chemical difference between Oort clouds comets and Kuiper Belt (Jupiter Family) ones?

I.2 Measuring molecular isotopic ratio: 34S/32S, 13C/12C, 15N/14N (issue with C15N and HC15N?) in moderately bright comets, D/H in several molecules (H2O, HCN, H2CO, NH3, CH3OH…): differs between molecules due to different enrichment process Place of formation of nuclei and proto-planetary nebula properties

I.3 Searching for complex molecules: ~15 only observed before in Hale-Bopp and new molecules Origin of solar system material

I.4 Monitoring molecular and dust production rates with heliocentric distance: Retrieving nucleus composition from abundances in the coma Structure of cometary ices

II Interferometric maps of cometary atmospheresALMA will enable high resolution (50-100km) 3-D imaging of gas jets with simultaneous dust jets imaging and good time sampling thanks to its extensive u-v plane coverage (large number of baselines)

Dust jets: 75% of the near nucleus coma signal in 1P/Halley (Giotto)

Strong gas and dust jets in Hale-Bopp:(most of nuclear CO): determines therotation period of 11h21m

Rotation of a CO jet in comet Hale-Bopp:3-D information

ALMA:HCN(3-2) or HCN(4-3) in several comets

Interferometric maps at 90 GHz and 220 GHz

comet Hale-Bopp

with IRAM Plateau de Bure

9, 11, 13 and 16 March 1997:

continuum of dust and nucleus

Altenhoff et al. 1999, A&A 348, 1020

Cometary « jets » with ALMAInvestigating the coupling between dust and gas, and different gaseous species:

Difference between night and day-time activity?

Dust features predicted different from gas ones close to the nucleus?

Variation of dust properties(opacity index, size distribution) with distance to the nucleus

Measurement of gas (e.g. CH3OH) temperature and velocity field

v

Molecules coming from a distributed source in the cometary atmospheres:

ALMA will be used to measure the scalelengths (100-10000 km)

H2CO: ~ 80% extended: thermo-degradation of polymers?

CO: ~50% extended in Hale-Bopp;

HNC, OCS: extended in Hale-Bopp?

CS, SO, NS?: daughter molecules;

Molecules released by grain sublimation

ALMA and the cometary atmospheres (interferometric mapping of physical properties)

II.1 Measuring rotation from molecular lines (e.g. HCN(3-2), strongest): 3-D measurements thanks to the spectral resolution: rotation of several comets per year

II.2 Comparing gaseous molecular jets and dust jets close to the nucleusCoupling of gas and dust in the near nucleus coma (sensitive to the nucleus shape), difference in day/night side activity: e.g. molecules only subliming on day side, difference in dust lifted by the gas,…

Cometary nuclei surface and gross properties (in addition to size)

II.3 Gas temperature and velocity field in the inner coma (50-1000km): Measuring adiabatic cooling and photolytic heating, T(r), v(r)

II.4 Molecular density profiles n(r) :extended sources Characterizing the parents (grains, other molecules, chemical reaction) of such daughter

molecules: CO, H2CO, CS, SO, HNC, NS… New parent molecules, better characterization of productions

comet date QH2O

[s-1]

[AU]

Molecules detectable

isotopes Moni-toring

Jets imaging

22P/Kopff 07/2009 1028 0.8 ~6 - - Low res.

81P/Wild 2 03/2010 1028 0.7 ~6 H13CN - Low res.

103P/Hartley2 10/2010 2.1028 0.13 15 +new ones

13C, 34S,

D, 15N, (7 molec.)

- High res.,

Dust, 6 molec.

45P/H.-M.-P. 08/2011 2.1027 0.07 ~10 13C,34S - Med. res.

2P/Encke 10/2013 6.1027 0.5 ~8 - - Low res.

New Comet Every year

1.1029 0.6 ~15 13C, 34S,

D, 15N, in 7 molec.

Up to 5 AU

High res.,

Dust, 6 molec

Great Comet Every 5 years

5.1029 0.6 15 + new ones

13C, 34S,

D, 15N, >10molec.

Up to 10AU

High res., Dust, 10 molec

Example of observable comets for ALMA