Tom Rice Advised by Ted Bergin and Alyssa Goodman

Dendrograms
in the Milky Way
Tom Rice
NSF Graduate Fellow (U. Michigan / CfA)
@tomr_stargazer
Advised by Ted Bergin
and Alyssa Goodman
24 June 2014 #HHSF14
Friday, August 1, 14
Friday, August 1, 14
Dame, Hartmann, Thaddeus 2001
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Friday, August 1, 14
No all-Galaxy catalog
exists...
• In comparison, there are several molecular
catalogs of external galaxies (M33, M51,
LMC, NGC 4736...)
Engargiola et al. 2003
Hughes et al. 2013
Meyer et al. 2013
PAWS...
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Friday, August 1, 14
A Galactic catalog
would help answer
questions:
• What is the role of external pressure versus
self-gravity in star formation?
• How does our distribution of star formation
compare to other galaxies & to simulations?
• What is the origin of the Kennicutt-Schmidt
Law?
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Friday, August 1, 14
Why is there
no such catalog?
1. Molecular line data is hard
to “segment” into “clouds”
2. Accurate distances are hard to get
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Friday, August 1, 14
My project is to make an
all-Galaxy catalog of clouds
1. Take the famous Dame et al. (2001)
CO map of molecular clouds
2. Segment the data via “Dendrograms”
into hierarchical structures
3. Assign distances and physical
properties to structures that are
identified as “clouds”.
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Friday, August 1, 14
Hierarchical Catalog
of Molecular Clouds
Data & Dendrograms
Distances & Catalogs
Software & Linked Views
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Friday, August 1, 14
Hierarchical Catalog
of Molecular Clouds
Data & Dendrograms
Distances & Catalogs
Software & Linked Views
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Friday, August 1, 14
We use the Dame, Hartmann,
Thaddeus (2001) CO data
θ = (1/8)°
Δv = 1.3 km/s
N_pixels = 683,180,173 data size=1.3 GB
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Friday, August 1, 14
Dendrograms allow us to
study hierarchical structure
Illustration: Chris Beaumont
Friday, August 1, 14
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Anatomy of a Dendrogram
flux or intensity
“leaves”
“branches”
“trunk”
x-positions arbitrary
cartoon courtesy Tom Robitaille
see dendrograms.org
Friday, August 1, 14
flux or intensity
Dendrograms 101
x-positions arbitrary
cartoon courtesy Tom Robitaille
see dendrograms.org
Friday, August 1, 14
flux or intensity
Dendrograms 101
x-positions arbitrary
cartoon courtesy Tom Robitaille
see dendrograms.org
Friday, August 1, 14
flux or intensity
Dendrograms 101
x-positions arbitrary
cartoon courtesy Tom Robitaille
see dendrograms.org
Friday, August 1, 14
flux or intensity
Dendrograms 101
x-positions arbitrary
cartoon courtesy Tom Robitaille
see dendrograms.org
Friday, August 1, 14
flux or intensity
Dendrograms 101
x-positions arbitrary
cartoon courtesy Tom Robitaille
see dendrograms.org
Friday, August 1, 14
Dendrogramming
the whole Galaxy
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Friday, August 1, 14
Hierarchical Catalog
of Molecular Clouds
Data & Dendrograms
Distances & Catalogs
Software & Linked Views
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Friday, August 1, 14
We guess distances to clouds using
their kinematic (velocity) information
But be careful:
inner Galaxy clouds
have two possible
distances!
Reid et al. (2009,
2014) provide the
latest velocity-todistance calculator
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Friday, August 1, 14
The Virial Parameter
helps us find real “clouds”
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Friday, August 1, 14
Hierarchical Catalog
of Molecular Clouds
Data & Dendrograms
Distances & Catalogs
Software & Linked Views
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Friday, August 1, 14
I’m helping develop the
“astrodendro” python package
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Friday, August 1, 14
Dendrograms in Perseus
Dendrogram
12CO
Moment map
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Friday, August 1, 14
Dendrograms in Perseus
Dendrogram
12CO
Moment map
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Friday, August 1, 14
Dendrograms in Perseus
Size-linewidth
Virial α
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Size-linewidth
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Linked views of the Nearby Galaxy
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Project goals:
make something useful
• Catalog will be distributed online for
community use
• Various visualizations (online, WorldWide
Telescope) will be created
• Figure out which distance methods are best
• Contribute linked views to “astrodendro”
software package
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Friday, August 1, 14
Hierarchical Catalog
of Molecular Clouds
Data & Dendrograms
Distances & Catalogs
Software & Future work
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Friday, August 1, 14
Summary:
To understand star formation in our Galaxy,
we need to know where it’s happening.
We’re taking the famous
13-year-old CO survey,
applying a new hierarchical
structure-finding algorithm,
and creating a much-needed
catalog of molecular clouds.
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Friday, August 1, 14
Thanks to collaborators:
Alyssa Goodman
Ted Bergin
Chris Beaumont
Chris Faesi
Hope Chen
Michelle Borkin
Tom Robitaille
& the “astrodendro” project (dendrograms.org)
Friday, August 1, 14
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