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A s A s t r t r o c h e m i e m i s t r t r y y t o S t u t u d y y T h e e E v o l u t i t i o n o f H i g o f i g h M a s s a s s S t a r a r s s u s i n s i n g A L M A N a o m i A s a b r e F r i m p o n g a n d P r

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A s A s t r t r o c h e m i e m i s t r t r y y t o S t u t u d y y T h e e E v o l u t i t i o n

  • f
  • f H i g

i g h M a s s a s s S t a r a r s s u s i n s i n g A L M A

N a o m i A s a b r e F r i m p o n g a n d P r o f . G a r y F u l l e r J o d r e l l B a n k C e n t e r f o r A s t r o p h y s i c s . Y E R A C 2 0 1 7

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In Intr troduc ductio tion

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  • The birth of stars begins in the core of dense molecular clouds under varies physical and

chemical conditions.

  • The collapse and condensation of these dense core of molecular clouds contribute to the

formation of proto-stars.

  • Initiated by turbulence, pressure waves from supernovae, stellar winds and the effect of

radiation and magnetic field

  • High mass stars are 80> mass of the sun.
  • More distant (∼> 400pc)
  • The formation time of the star is shorter.
  • Starts nuclear fusion in core before reaching main sequence structure.
  • high luminosity from nuclear burning and short lifetime

Evans, N. J., 1999, Annual Review of Astronomy and Astrophysics, 37

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SLIDE 3

Co Comp mplex mo molecules

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  • Complex molecules are molecules containing 6 or more

atoms such as CH3OH, CH3CN, CH3CH2CN, CH3CCH AND CH3CHO.

  • The interaction of gas with the dust grains in the

molecular cloud and the ionization by cosmic rays leads to the formation of complex molecules .

  • Accretion → Diffusion → Reaction → Cosmic ray/UV

interaction → Ejection

  • The rotation and vibrational spectra given off by the

excitation of the molecules give an indication about the physical conditions of the gas, dust and ice mantles.

  • The chemistry of complex molecules and their spectra

can be used as probes to investigate the physical and chemical conditions of gas and dust in their immediate environment.

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The ALMA Survey

  • Thirty nine (39) massive young stellar objects(MYSO). The

data was taken by ALMA in cycle 3 and in Band 6 covering a frequency range around 227GHz in the (LSB) and 241GHz (USB).

  • ALMA has sufficient resolution and sensitivity to investigate

the various chemical evolutionary tracers of MYSO.

  • The spectral setup covers multiple transitions of a range of
  • rganic species including CH3OH,CH3CN, CH3CCH CH3OCH3 as

well as J=2-1 transition of C17O and 2-1 transition of CN. ANALYSIS The CASSIS software uses the LTE and Non-LTE radiative transfer model to constrain the physical and chemical properties of the source of interest.

  • Column density
  • Kinetic and excitation temperatures
  • Abundance
  • Velocities
  • Line width

http://www.dailymail.co.uk/sciencetech/article-2292598/ALMA-Scientists-reveal-stunning-setting-worlds-largest-telescope.html http://cassis.irap.omp.eu/

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  • MSX6C G025.3953+00.0336 (18h 37m 30.308s -

6d 41m 18.313s, J2000) is located at 4.0 kpc.

  • It has been identified as a Massive Young Stellar

Object(YSO) in the Red MSX Source(RMS) Survey which contains a H2Omaser from the MSX Survey

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So Source examp mple - MS MSX6C 6C G025. 025.3953+ 3953+00. 00.0336 0336

Lumsden et al 2013

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Li Line Analysis

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CH3OH CH3CN CH3CCH SPECIES COMPONENT 1 COMPONENT2

Tex(K) N(cm-2) 1015 FWHM (km/s) Tex(K) N(cm-2) 1014 FWHM (km/s)

CH3OH

196 10.0 8.1 132 72.0 2.9

CH3CN

200 0.12 9.8 126.7 0.68 3.1

CH3CCH

157.9 1.6 5.1 112.6 4.2 2.5

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The modelled spectra of the detected species was superimposed

  • n the spectra from the source with

an offset of 2K

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HN HNCO

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  • G017.6380+00.1566 (18:22:26.38s, -13:30:12.00s) is located 2.2kpc .
  • It has been identified as a Massive Young Stellar Object(YSO) in the Red MSX

Source(RMS) Survey which contains a H2O maser from the MSX Survey.

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CH CH3OH 3OH

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SPECIES COMPONENT 1 COMPONENT2 Tex(K) N(cm-2) 1015 FWHM (km/s) Tex(K) N(cm-2) 1014 FWHM (km/s) CH3OH 256 50.6 4.2 120 4.7 3.9 HNCO 204 0.6 6.6 72 0.5 5.6

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FUTURE

These observations will help to address

  • How the properties of the circumstellar molecular gas changes with

source luminosity and SED properties, identifying possible evolutionary trends.

  • How the mass of dust in the circumstellar region evolves across the

range of luminosity and colour.

THANK YOU

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