Forest laws, Indian forest laws, why they are important
Dissection of a Cold, Infalling High-Mass Star-Forming Core
1. Tigran Khanzadyan
Centre for Astronomy, NUIG
ASGI Autumn Meeting at UCC, 3rd of October 2008
Dissection of a Cold, Infalling
High-Mass Star-Forming Core
In CollaborationWith :
Patrick Carolan & Matt Redman (NUIG, Ireland), MarkThompson (Hertfordshire, UK),
Paul Jones & Maria Cunningham (Univ. New SouthWales,Australia) and
Indra Bains (Swinburne University of Technology,Australia)
2. Talk Content
• Brief introduction into star-formation (SF).
• Observing the SF, what can be done.
• JCMT 18354-0649S core and our project
• Modelling and understanding “the beast”
3. Low-Mass High-Mass
Formation
Slow vs. Quick
Isolated vs. Crouded
Life
Long vs. Short
Quiet vs.Violent
Death
Planetary Neb. vs. SN Explosion
If their evolution is different then how about the origin?
4. High-Mass SF (I)
• There is still a debate about the origin of High-Mass
Stars : Mergers vs. Size-up version of Low-Mass SF -
both approaches have pros and cons (obviously).
• Many difficulties to trace the high-mass SF in making -
complicated environment
• Current understanding is more inclined towards Size-
up theory due to the emerging observational
evidence - infall and outflow signatures similar to low-
mass SF vs. no reliable kinematical evidence for
merger theory.
5. High-Mass SF (II)
• If they originate in the same way/conditions where did
the divergence take place?
• What are the chemical and physical processes at play?
• Freeze-out - When the temperature is low enough and
the density is high enough the gas will ‘freeze-out’ or
stick onto a dust grain (depletion due to freez-out)
• Infall - A starless core will collapse when it loses pressure
support
• Outflow - Once Infall starts there has to be outflow to
conserve angular momentum
6. Observing these all ...
• Early stage of SF is
Heavily obscured
optically so we need to
look in the mm part of
the spectrum
• We have a choice to
study continuum
radiation as well as tune
into some well know
molecular line
transitions
JCMT
MOPRA
APEX
ALMA
7. Kind of Data we get
Bolometers detect thermal continuum
emission from the cold dust grains.
Temperature Density are calculated
from it.
Receivers tune to mm emission lines
of gas. Line emission can tell us the
chemistry and dynamics. Candidate
species would be N2H+, HCO+,
HCN, NH3, CO and others ...
8. Infall Signature
• So can we actually
observe the infall
motions in the star-
forming cores?YES!
• Not only we can
observe it, we can
actually explain it!
B335
All this was known from Low-Mass SF, how about High-Mass SF?
9. JCMT 18354-0649S
• First reported by Wu et al, 2005,ApJ, 628, L57 to be a
direct indication of infall motions towards high-mass SF
core! No objects were detected in any shorter
wavelengths at that position - so it’s pretty exciting!
10.
11. Observing campaign
• So infall in High-Mass SF? - we need more data to get
into the mechanism of the process.
• We successfully applied to JCMT (30h), MOPRA(8h)
times!
• We obtained lot’s of archive data, JCMT, SPITZER, etc
• We analysed all the data!
14. Then comes the model
• After obtaining all these “nice” data-sets we can try to
interpret what all these lines mean or we could try to
model them by using a 3D, non-LTE radiative
transfer code in our disposal (chronologically speaking
we had this code before the observations).
• Each cell in the 3D grid is given a temperature, turbulent
width, velocity, density and chemical abundance (from data)
• The code calculates level populations and hence emission seen
by an observer
• Can load observations into the code and run multiple models
27. The Fit Parameters
Molecule
Density
(cm-3)
Velocity
km/s
Turb.Width
km/s
Temp. (K)
Abundance
n(H2) in cm-3
12CO env. 1 x 106 1 (inf) 1.6 20 1 x 10-6
12CO out 6 x 104 10 1.7 110 2 x 10-5
C17O 1 x 106 1 (inf) 1.6 20 1 x 10-9
C18O 1 x 106 1 (inf) 1.6 20 10 x 10-9
HCN 1 x 106 2 (inf) 1.5 17 1 x 10-11
HCO+ 1 x 106 1 (inf) 0.8 20 90 x 10-11
H13CO+ 1 x 106 1 (inf) 1.4 20 15 x 10-11
28.
29. So?
• We have quite a good fit on temperature
(20K), infall velocity, turbulent width and
the density.
• We have a rotation of the cloud about
1km/s.
• We have an outflow and we know the
direction, velocity all the essential
parameters.
30. Points to take with you
• It is much likely that High-Mass SF is Size-up version of
the Low-Mass SF
• We can use SubMM and MM to carefully dissect the
High-Mass SF core in order to learn about the physics
and dynamics.
• JCMT 18354-0649S is an example core with infall/
outflow motions where we can follow the early stage of
High-Mass SF.
• We produced pretty good fit with our 3d non-lte
radiative transfer code which reveals quite a good inside
of processes occurring in the core.Talk to us if you need
more ...