NEW LARGE INTERSTELLAR MOLECULES
DETECTED WITH THE GBT
J. M. Hollis
NASA Goddard Space Flight Center
Colleagues: Frank Lovas (NIST), Phil Jewell (NRAO), Tony Remijan (NASA/NRC)
OUTLINE
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Introduce the Green Bank Telescope (GBT)
SgrB2(North-LMH): the best source of large molecules
Present the list of known interstellar molecules
Show typical spatial maps of large molecules that are compact or extended
Show typical GBT raw spectral bandpasses
Show reduced spectra of large molecules observed with the GBT
Suggest a GBT experiment that may explain interstellar sugar formation
The Green Bank Telescope
 B = 740 " /  [GHz]
 7854 m2
 6 hrs on LMH above
10o elevation
 4x200 MHz bands in
2 polarizations
 24.4 kHz resolution
 OFF(2 min)-ON(2 min)
Interstellar Molecules
135 as of February 2005
Red Lettering => IR or UV Detections | Colored Background ==> Isomers
Molecules with 2 atoms
Molecules with 3 atoms
H2
hydrogen molecule
CO
carbon monoxide
H2O
water
H2S
hydrogen sulfide
CSi
carbon monosilicide
CP
carbon
monophosphide
HCN
hydrogen cyanide
HNC
hydrogen isocyanide
CS
carbon monosulfide
NO
nitric oxide
CO2
carbon dioxide
SO2
sulfur dioxide
NS
nitrogen monosulfide
SO
sulfur monoxide
MgCN
magnesium cy anide
MgNC
magnesium
isocyanide
HCl
hydrogen chloride
NaCl
sodium chloride
NaCN
sodium cyanide
N2O
nitrous oxide
KCl
potassium chloride
AlCl
NH2
amidyl radical
OCS
carbonyl sulfide
AlF
aluminum
monofluoride
PN
HCO
formyl radical
C3
triatomic carbon
SiN
silicon mononitride
SiO
silicon monoxide
C2H
ethynyl radical
HCO
SiS
silicon monosulfide
NH
imidyl radical
HOC
hydroxymethylidyne
N2H
OH
hydroxyl radical
C2
diatomic carbon
HNO
nitrosyl hydride
HCS
CN
cyanide radical
HF
hydrogen fluoride
H3
+
sulfur monoxide ion
+
+
aluminum
monochloride
phosphorus
mononitride
+
+
+
formyl ion
+
dinitrogen
monohydride ion
+
thiooxomethylium
hydrogen ion
C2O
ketenylidene
C2S
thioxothenylidene
SiC2
silicon dicarbide
carbon monoxide ion
SO
CH
methylidyne
CH
methyliumylidene
AlNC
aluminum isocyanide
CH2
methylene
SH
mercapto radical
LiH
lithium hydride
SiCN
silicon monocyanide
SiNC
silicon isocyanide
FeO
iron oxide
N2
diatomic nitrogen
CO
Molecules with 4 atoms
Molecules with 7 atoms
NH 3
ammonia
H2CO
formaldehyde
CH 3CCH
methyl acetylene
CH 3CHO
acetaldehyde
H2CS
thioformaldehyde
C2H2
acetylene
CH 3NH 2
methylamine
CH 2CHCN
vinyl cyanide
HNCO
isocyanic acid
HNCS
thioisocyanic acid
HC 5N
cyanobutadiyne
C6H
1,3,5-hexatriynl
+
hydronium ion
HOCO
protonated carbon
dioxide
c-C 2H4O
ethylene oxide
CH 2CHOH
vinyl alcohol
C3S
1,2-propadienylidene,
3-thioxo
H2CN
methylene amidogen
c-C 3H
cyclopropenylidyne
l-C 3H
2-propynylidyne
CH 3COOH
acetic acid
CH 3OCHO
methyl formate
HCCN
cyanomethylene
C3O
tricarbon monoxide
CH 3C3N
cyanomethylacetylene
CH 2(OH) CHO
glycolaldehyde
C2CN
cyanoethynyl
SiC3
Rhomboidal SiC 3
H2C6
hexapentaenylidene
HC 6H
triacetylene
iminomethylium
CH 3
methyl radical
C2H6
ethane
C7H
2,4,6-heptatriynylidyne
CH 2CHCHO
propenal
H3O
HCNH
+
+
Molecules with 5 atoms
Molecules with 8 atoms
Molecules with 9 atoms
CH 4
methane
SiH4
silane
CH 2NH
methyleneimine
NH 2CN
cyanamide
(CH 3)2O
dimethyl ether
CH 3CH2OH
ethanol
CH 2CO
ketene
HCOOH
formic acid
CH 3CH 2CN
ethyl cyanide
CH 3C4H
methylbutadiyne
HC 3N
cyanoacetylene
HC 2NC
isocyanoacetylene
HC 7N
cyanohexatriyne
C8H
1,3,5,7-octateraynyl
c-C 3H2
cyclopropenylidene
l-C 3H2
propenylidene
CH 2CN
cyanomethyl radical
C4H
1,3-butadiynyl radical
(CH 3)2CO
acetone
HOCH 2CH 2OH
ethylene glycol
C4Si
silicon tetracarbide
C5
pentacarbon molecule
CH 3CH 2CHO
propanal
CH 3C5N
methylcyano
diacetylene
HNC 3
1,2-propadienylidene, 3-imino
H2COH
protonated
formaldehyde
+
Molecules with 6 atoms
methanol
CH 3SH
methanethiol
H2CCH 2
ethylene
HCCCCH
diacetylene
CH 3CN
methyl cyanide
CH 3NC
methylisocyanide
HCONH 2
formamide
HC 2CHO
propynal
C5H
2,4-pentadiynylidyne
HC 3NH
C5N
HC 4N
1,3-butadiynylium,
4-cyano
3-cyano
2-propynylidene
H2CCCC
Molecules with 11 atoms
HC 9N
CH 3OH
+
Molecules with 10 atoms
protonated 2propynenitrile
butatrienylidene
cyanooctatetrayne
Molecules with 12 atoms
C6H6
benzene
Molecules with 13 atoms
HC 11N
cyanodecapentayne
Species Detected with GBT
Acetaldehyde
(CH3CHO)
GMRT channel
maps
(Unpublished - Courtesy of
Chengular & Kanekar)
See also, Chengular & Kanekar,
2003, A&A, 403, L43
Ethyl Cyanide (CH3CH2CN) VLA Map
Hollis et al. 2003, ApJ, 596, L235
515 - 414 @ 43.5 GHz
Typical Raw
GBT
Instrumental
Bandpasses
Glycolaldehyde
GBT Spectra
Hollis et al. 2004, ApJ, 613, L45
 110-101 @ 13.48 GHz, B = 55’’
 211-202 @ 15.18 GHz, B = 49’’
 312-303 @ 17.98 GHz, B = 41’’
 413-404 @ 22.14 GHz, B = 34’’
 Smaller GBT beams
coupling better to continuum
sources
Ethylene Glycol GBT Spectra
(Unpublished)
Propenal GBT
Spectra
Hollis et al. 2004, ApJ, 610, L21
 K-Band
- No hot core line confusion
- Few extended large molecules
- Propenal has three likely
transitions in the 18-26
GHz range.
 Hydrogen addition likely
accounts for progressively
larger species:
propYnal
HC2CHO
propEnal
CH2CHCHO
propAnal
CH3CH2CHO
Propanal
GBT Spectra
Hollis et al. 2004, ApJ, 610, L21
 Each panel represents
two full tracks on
SgrB2(N)
 Transitions shown span
the range 19.1 - 22.3
GHz.
propYnal
propEnal
propAnal
HC2CHO
CH2CHCHO CH3CH2CHO
POLYMERIZATION OF FORMALDEHYDE
Formaldehyde Production:
O + CH3
H2CO + H
(1)
H2COH+ + H2
(2)
Formaldehyde Depletion to Protonated Formaldehyde:
H3+ + H2CO
Protonated Formaldehyde Destruction (Hoffmann & Schaefer 1981, ApJ, 249, 563):
e- + H2COH+
trans HCOH + H
(3a)
e- + H2COH+
cis HCOH + H
(3b)
e- + H2COH+
H2CO + H
(3c)
First Step in Polymerization of Formaldehyde Yields Glycolaldehyde:
(Flanagan, Ahmed, & Shevlin 1992, J.Am.Chem.Soc., 114, 3892)
(a) The electron pair on the divalent carbon adds to the formaldehyde carbon.
(b) Causing the double bond electron pair to accept the hydrogen.
(c) The pair of electrons that was bonded to the hydrogen forms the new C=O bond.