Takahiro Oyama Rin Abe Ayane Miyazaki Mitsunori Araki Shuro Takano Nobuhiko Kuze Yoshihiro Sumiyoshi and Koichi Tsukiyama Interstellar Glycine Glycine the simplest amino acid Detection of ID: 629573
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Slide1
A search for the HOCO radical in the massive star-forming region Sgr B2(M)
Takahiro Oyama,
Rin Abe, Ayane Miyazaki,
Mitsunori Araki, Shuro Takano, Nobuhiko Kuze,
Yoshihiro Sumiyoshi, and Koichi TsukiyamaSlide2
Interstellar Glycine
Glycine:
the simplest amino acid
Detection of
interstellar glycine
However…
There is no obvious detection of interstellar glycine
・
Small dipole moment (
ma = 0.9 D)
・Large partition function
Crucial first step
in Astrobiology
First step:
Detection of Glycine precursor
It is difficult to observe the rotational
transitions of Glycine in interstellar medium
Because… Slide3
Dust surface
Aminomethyl
radical (CH
2
NH
2
)
No report of pure rotational spectra
CH
2
NH2 cannot be identified in ISM.
HOCO
+
CH
2
NH2 → NH2CH
2COOHWoon
et al.
, ApJ 571, L177 (2002).
HOCO
CH
2NH2
NH2
CH
2
COOH
Glycine is produced from
Sublimation or
Collision of the grain
Dust surface
Glycine product reaction on dust surface
Precursor are also moved into gas phase.Slide4
HOCO
is produced on grain surfaces as…
HOCO
radical
OH + CO →
HOCO
or HCOOH
→
HOCO
+ H
Distribution and column density of HOCO
is
correlated with those of interstellar Glycine
Stabilized with
release of excess
energy to grain
Moved into gas phase
by sublimationSlide5
HOCO
In 2011, accurate molecular constants were
determined by FTMW spectroscopy.
Oyama
et al
.,
J. Chem. Phys
. 134, 174303 (2011)
Detections in CO matrix and interstellar ice analogs Milligan et al
., J. Chem. Phys. 54, 927 (1987) Holton et al., Astrophys
. J. 626, 940 (2005) .
HOCO
radical
HOCO: A good tracer of interstellar Glycine
Rest frequencies can be calculated
precisely using the determined
molecular constants.
+
Distribution of HOCO is correlated
with that of interstellar Glycine.Slide6
Sgr B2(M) Massive star-forming region
Distance from sun:
8.5
kpc
≒
2.8×10
4
ly Radial velocity: 62 km/s
Features: Many interstellar molecules
cm wave continuum source
Observation positionSlide7
Estimation of column density
Column density of
HOCO
is estimated by that of
HOCO
+
and
HCO/HCO
+
ratio in
Sgr
B2.
Column density of HOCO in
Sgr
B2
Slide8
Nobeyama 45-m telescope
• Observing period
2016/4/8~11,
and 5/10~11
•
Autocorrelator
FX-type SAM45
• Receiver
TZ1(H/V)
•
Freq.resolution 488.24 kHz
• Bandwidth 1600 MHz
Telescope and Observing periodSlide9
Result
Total ON time: 4 hours
HOCO
N
= 4
04
−
3
03
J
= 4.5
−
3.5
J
= 3.5−2.5
r.m.s
: 9.6 mKNo detection
of HOCO radical
Next step
Determination of upper limitof column density for HOCOSlide10
W
: Integrated brightness
temperature
: Transition frequency
S
: Line intensity
m
:
Dipole moment
T
rot
: Rotational temperature
E
u
: Energy of the upper state
N
: Column density
Q
rot
: Rotational partition function
Rotational diagram method
T
rot
is fixed to be that of
HOCO
+
as 12.3 K.
m
a
of HOCO is almost the
same as that of HOCO
+
.
No beam dilution effect
Source size is larger than
beam size(HPBW 18.”2).
Jones
et al
.,
Mon
.
Not
.
R
.
Astron
.
Soc
.
386
, 117 (2008).Slide11
Assumption: Detection limit of lines are S/N ratio = 3
Upper limit of column density: 9.5×1012
cm
−2
r.m.s
: 9.6 mK
Simulation
Obs.
r.m.s
: 34.5 mK
Simulation
Obs.
Upper limits of column density of HOCO
88 GHz
44 GHz
There are no obvious lines in these region.Slide12
Assumption I. Glycine is produced mainly from…
Assumption II. Column density of Glycine is comparable to that of HOCO
Column density of Glycine:
~10
13
cm
−2
HOCO
+ CH2
NH2 → H2NCH2COOH
One to two orders of
magnitude smaller
than the reportedvalues
Reported upper limits
(cm
−2
)
Sgr B2(N)
2.2×10
13
Sgr B2(N-LMH)
4.2×10
14
Sgr B2(LMH)
3.7×10
14
Sgr B2(OH)
7.0×10
13
Upper limits of column density of GlycineSlide13
Summary
• No detection of HOCO radical in Sgr B2(M)
The upper limit of the column density of
HOCO in Sgr B2(M): 9.5×10
12
cm
−
2
The upper limit of the column density of
Glycine in Sgr B2(M): ~10
12 cm
−2Slide14
New oxygen-bearing organic molecule that is HCCO was detected in the starless core Lupus-1A and molecular cloud L483.
Agúndez
et al
,
A&A
577
, L5 (2015)
Next plan
The chemistry of the cold dark clouds needs to be
revised by the new observational results.
HOCO is a simple oxygen-bearing organic molecule, and may be observed in the cold clouds.
Observation of HOCO toward Lupus-1A and L483
Three orders of magnitude more abundant
than predicted by gas phase chemical models.Slide15Slide16
Beam width
Previous line surveys
Cummins
et al
. (1986)
70~150 GHz
r.m.s
: 30~50 mK
Turner (1989)
70~115 GHz
r.m.s
: ~50 mK
Friedel
et al
. (2004)
86~110 GHz
Present observation
87~91, 99~101 GHz
r.m.s
: ~13 mK
HPBW: 18.
″
2
17
h
47
m
20.3
S
−
28
23
′
07.3
″
Present observationSlide17
Result
LSB 87.5~91.5 GHz
USB 99.6~103.6 GHz
87.5
88.0
88.5
89.0
89.5
90.0
90.5
91.0
GHz
100.0
100.5
101.0
101.5
102.0
102.5
103.0
103.5
0.4
0.2
0.0
0.4
0.2
0.0
K
K
GHzSlide18
In 2011, accurate molecular constants were
determined by FTMW spectroscopy. Oyama et al., J. Chem. Phys. 134, 174303 (2011)
Detections in CO matrix and interstellar ice analogs
Milligan
et al
.,
J. Chem. Phys
. 54
, 927 (1987) Holton et al., Astrophys. J
. 626, 940 (2005) .
X 2A’
m
a
= 2.6 D
A
0 167768.064(42)B0
11433.322(41)C0
10686.630(41)
HOCO
HOCO
radical
Rest frequencies can be calculated precisely
using the determined molecular constants.
HOCO
A good tracer of
interstellar GlycineSlide19
HOCO
is produced on grain surfaces as…
HOCO
radical
OH + CO →
HOCO
or HCOOH
→
HOCO
+ H
The produced HOCO can be stabilized withrelease of the excess energy to grain.
Distribution of HOCO
is correlated with that
of interstellar glycine.
HOCO
A good tracer of
interstellar Glycine