The SMA CO(6-5) &
690 GHz Continuum
Observations of Arp 220
Satoki Matsushita (ASIAA)
D. Iono (CfA), C.-Y. Chou (ASIAA), M. Gurwell (CfA),
P.-Y. Hsieh (NTU, ASIAA), T. Hunter(CfA), J. Lim (ASIAA),
S. Muller (ASIAA), A.B. Peck (CfA), G. Petitpas (CfA),
K. Sakamoto (NAOJ, CfA), S. Sawada-Satoh (ASIAA),
Dinh-V-Trung (ASIAA), M.C. Wiedner (Univ. Koln, CfA),
D. Wilner (CfA)
Introduction
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Arp 220
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Prototypical Ultra Luminous Infrared Galaxy (ULIRG).
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Final stage of galaxy merger.
Two nuclei at the center (~1” / 370 pc separation).
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One of the nearest ULIRGs (77 Mpc)
L8-1000mm = 1.4 x 1012 Lsun (Soifer et al. 1987)
2.2’
High resolution high-J CO lines & dust imagings are
important to know about the conditions of extreme starburst
in merging sequence.
19”
Scoville et al. 1998
believeHST/NICMOS
to be nearby
ULIRGs are
high-z starburst galaxies.
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
counterparts for
Due to the redshift, many of the high-z galaxies observed
with high-J CO lines.
Observing high-J CO lines of
nearby ULIRGs are important
Arp 1966
2.8’
for the study of high-z starburst
galaxies.
Palomar 5m
Observation & Calibration
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Telescope: SMA
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Date: March 2nd, 2005
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225 GHz opacity = 0.03-0.04
Frequency Setting
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Antennas: 1,2,3,4,5,6
LSB: 679.2 GHz CO(6-5)
USB: 689.2 GHz Continuum
Calibrators
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Amplitude & Phase: Callisto (~50o away)
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Flux of Ceres shows 78% of the actual.
=> Flux accuracy ~ 20%-25%
Position of Arp 220 shifted for ~0.7”, consistent with the
baseline errors.
Bandpass: Mars, Callisto, & Ganymede
Imaging
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Beam size: 1.2” x 0.8” (450 pc x 300 pc)
Results
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Arp 220 689 GHz (435 mm) continuum
Total flux: 2.3 Jy
 Single-dish 450mm
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 UKIRT
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Eales et al. 1989
3.0+-1.1 Jy
Missing flux = 23%
 JCMT
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UKT14
SCUBA
Dunne & Eales 2001
6.3+-0.8 Jy
Missing flux = 63%
1.2” x 0.8”
Contours: -2, 2, 4, 6s
Results
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Comparison between other continuum
images in different wavelengths.
E Nucleus
0.90 Jy/beam
W Nucleus
0.96 Jy/beam
1.2” x 0.8”
Sakamoto et al. (1999)
Sakamoto et al.
Discussion (Continuum)
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Arp 220 689 GHz continuum
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East Nucleus: 900 +- 0.16 mJy/B
West Nucleus: 960 +- 0.16 mJy/B
E/W flux ratio: 0.94 +- 0.23
Arp 220 230 GHz continuum
(Sakamoto et al. 1999)
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East Nucleus: 66 +- 9.3 mJy/B
West Nucleus: 142 +- 9.3 mJy/B
E/W flux ratio: 0.46 +- 0.07
Arp 220
Discussion (Continuum)
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Comparison of SED with that of the high-z QSO
D. Iono et al., poster in this meeting.
BR1202-0725
Arp 220
BR1202-0725
n3.2
n1.8
n2.9
Blue: Total flux
Red: W Nucleus
Green: E Nucleus
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n2.5
n3.4
SMA 333 GHz
(900 mm) image
The two nuclei/sources in both galaxies seem to have different
spectral indices.
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Note that separations of the nuclei are very different:
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Different dust properties?
Effect of synchrotron / free-free emission?
Arp 220: ~ 300-400 pc vs BR 1202-0725: ~ 30-40 kpc
Note that BR1202-0725 is z ~ 4.7 => 350 GHz -> 2 THz
Results
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Arp 220 CO(6-5) Integrated Intensity
Sakamoto et al. (1999)
1.2” x 0.8”
Sakamoto et al.
Results
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Arp 220 CO(6-5) Velocity Map
SMA CO(6-5)
Sakamoto et al. 1999
Results
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ARP 220 CO(6-5) Spectra
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8.3 K
Peak Temperature
@ 1.2” x 0.8” beam
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5.6 K
E Nucleus: Peak = 9.4 K
W Nucleus: Peak = 10.6 K
Peak Temperature
assuming 0.57” x 0.52” size
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E Nucleus
0.0 K
W Nucleus
E Nucleus: Peak = 30 K
W Nucleus: Peak = 34 K
8.3 K
ARP 220 CO(2-1)
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Peak Temperature
@ 0.57” x 0.52” size
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E Nucleus: Peak = 38 K
W Nucleus: Peak = 37 K
5.6 K
0.0 K
5350 km/s
Discussion (CO lines)
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Comparison of CO intensities between nearby to
high-z galaxies
Arp 220
Kawabe et al. 1999
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Arp 220 CO intensities are similar to nearby
starburst & high-z starburst galaxy.
Conclusion
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We succeeded to image CO(6-5) & 690 GHz
(435 mm) continuum maps of Arp 220 with the
SMA.
690 GHz continuum image
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Two nuclei seems to have different spectral indices at
sub-mm.
CO(6-5) image
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CO(6-5) emission seems to have similar distribution &
kinematics to that of CO(2-1).
Physical conditions of CO gas seems to have similar
to that of nearby & high-z starbursts.
=> Support the idea that ULIRGs are the nearby
counter part of high-z starburst galaxies.