Understanding Local Luminous Infrared
Galaxies in the Herschel Era
Jason K. Chu ([email protected])
Institute for Astronomy, University of Hawai`i
Collaborators: David Sanders (IfA), Kirsten Larson (Caltech/IPAC), Joe
Mazzarella (Caltech/IPAC)
Why Study Luminous IR Galaxies?
• Hundreds of luminous infrared galaxies (LIRGs) first discovered in
the 1980s.
• They emit the bulk of their intrinsic luminosities in the infrared:
LIR= L(8-1000 μm).
• Many are interacting/merging!
• LIRGs are much more common in
the early universe!
• GOALS is a complete, nearby sample of infrared
luminous galaxies.
• They represent a complete picture of galaxy evolution.
– Very high star formation rates.
– Rapid feeding of the central supermassive black holes.
• Infrared radiation originates from dust in galaxies.
 Critical to study these galaxies in high resolution in the farinfrared, where they emit the bulk of their intrinsic luminosity.
Herschel-GOALS Observations
• Entire GOALS sample imaged by PACS and
SPIRE instruments on board the Herschel
Space Observatory.
• Imaging obtained between 70 – 500 μm in
wavelength.
• Herschel has better resolution than all
previous far-infrared space missions.
Chu+ 2017
Results: The Herschel-GOALS Atlas
• Maps of all ~200 GOALS systems have been published for
all six Herschel bands.
Results: Infrared Spectra of (U)LIRGs
n Ln [log LSun]
11.00 < log(L IR/LSun) < 11.25
11.25 < log(L IR/LSun) < 11.50
11.50 < log(L IR/LSun) < 11.75
12
12
12
11
11
11
10
10
10
9
9
9
1
10
l [mm]
100
1000 1
11.75 < log(L IR/LSun) < 12
10
100
1000 1
12.00 < log(L IR/LSun) < 12.25
12
12
11
11
11
10
10
10
9
9
9
10
100
1000 1
10
100
100
1000
12.25 < log(L IR/LSun)
12
1
10
1000 1
10
100
1000
Results: Infrared Spectra of (U)LIRGs
IRAS
11.00 < log(L IR/LSun) < 11.25
N=64
n Ln [log LSun]
12
11.25 < log(L IR/LSun) < 11.50
12
N=58
11.50 < log(L IR/LSun) < 11.75
12
11
11
11
10
10
10
9
9
9
1
10
l [mm]
100
1000 1
10
11.75 < log(L IR/LSun) < 12
N=19
12
100
1000 1
12
N=13
12
11
10
10
10
9
9
9
100
1000 1
10
100
100
1000
12.25 < log(L IR/LSun)
11
10
10
12.00 < log(L IR/LSun) < 12.25
11
1
N=38
1000 1
N=9
10
100
1000
Results: Infrared Spectra of (U)LIRGs
IRAS + Spitzer + WISE
11.00 < log(L IR/LSun) < 11.25
N=64
n Ln [log LSun]
12
11.25 < log(L IR/LSun) < 11.50
12
N=58
11.50 < log(L IR/LSun) < 11.75
12
11
11
11
10
10
10
9
9
9
1
10
l [mm]
100
1000 1
10
11.75 < log(L IR/LSun) < 12
N=19
12
100
1000 1
12
N=13
12
11
10
10
10
9
9
9
100
1000 1
10
100
100
1000
12.25 < log(L IR/LSun)
11
10
10
12.00 < log(L IR/LSun) < 12.25
11
1
N=38
1000 1
N=9
10
100
1000
Results: Infrared Spectra of (U)LIRGs
IRAS + Spitzer + WISE + Herschel
11.00 < log(L IR/LSun) < 11.25
N=64
n Ln [log LSun]
12
11.25 < log(L IR/LSun) < 11.50
12
N=58
11.50 < log(L IR/LSun) < 11.75
12
11
11
11
10
10
10
9
9
9
1
10
l [mm]
100
1000 1
10
11.75 < log(L IR/LSun) < 12
N=19
12
100
1000 1
12
N=13
12
11
10
10
10
9
9
9
100
1000 1
10
100
100
1000
12.25 < log(L IR/LSun)
11
10
10
12.00 < log(L IR/LSun) < 12.25
11
1
N=38
1000 1
N=9
10
100
1000
Summary
• Our Herschel observations of a complete sample of nearby LIRGs
represent the highest resolution far-infrared study of these
colliding, exotic galaxies.
• We can now accurately calculate many important far-infrared
galaxy properties that was previously impossible.
Or, the Tweet-able version:
We obtain the best far-infrared maps of local luminous infrared
galaxies allowing us to study galaxy properties previously impossible
to do.
Contact: Jason Chu ([email protected])
For more information visit: http://goals.ipac.caltech.edu/