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Mathematisch-Naturwissenschaftliche Fakultät
Fachgruppe Physik

I. Physikalisches Institut

Molecules in Space

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ISM/CSS
extragalactic molecules

Press release by the MPIfR on the radio astronomical detection of i-propyl cyanide in Sagittarius B2(N) with ALMA. Deutsche Version der Pressemitteilung der Universität zu Köln

Note: Deuterium isotopic species are given separately only if their method of detection is intrinsically different from that of pure hydrogen ones. We plan to modify this in the future to include them with all hydrogen species.

The documentations generally provide information on the detection of the respective molecules, including minor isotopic species, molecules in excited vibrational states, or different media in which the species has been detected as well as links to articles.

All molecules have been detected (also) by rotational spectroscopy in the radiofrequency to far-infrared regions unless indicated otherwise.
* indicates molecules that have been detected by their rotation-vibration spectrum,
** those detected by electronic spectroscopy only.

Transition metal molecules detected in atmospheres of stars by electronic spectroscopy are currently not included. We plan to create a new table in the not so distant future dealing with molecules in stellar atmospheres. In this context, the table of molecules detected in the interstellar medium (ISM) or circumstellar envelopes (CSE) of late type stars, will be split. In the case of some metal monoxides, emission features have been detected in optical or IR spectra. Most likely, this emission indicates a presence of these molecules in the circumstellar shell. Around one handful of molecules may have to be added.

Note: Questionable or rebuted detections have been omitted from the table. Some noteworthy cases are given below the table. Tentative detections, which have a reasonable chance to be correct, are indicated by "?". Usually the number of observed transitions that are, at least, fairly free of overlap is small. Some detections that have been reported as secure ones are indicated by "(?)" because (partial) overlap of lines cannot be ruled at the moment or because the line list is somewhat small; obviously, there may be cases on the edge.

As the decision whether a molecule can be considered as detected frequently is a controversial one we refrain from stating an exact number of molecules as detected. As of November 2014, at least 180 molecules have been detected unambiguously in the interstellar medium or circumstellar shells; at least five of these are tentative detections, and for at least three others, the situation may be somewhat uncertain. Including some molecules missing in the table, the number of molecules detected in the ISM or in CSEs is around 185. Thus, we recommend phrases such as "more than 180 molecules have been detected in the interstellar medium or circumstellar shells". Two reported detections have been questioned seriously. Therefore, these are viewed currently as "probably not yet detected" – see below. They do not show up in the table anymore.

The number of molecules detected in extragalactic sources is 56 plus 1 tentative plus 1 questionable detections. More may have to be added.

We welcome comments on this list !

Molecules in the Interstellar Medium or Circumstellar Shells (as of 10/2014)

2 atoms 3 atoms 4 atoms 5 atoms 6 atoms 7 atoms 8 atoms 9 atoms 10 atoms 11 atoms 12 atoms >12 atoms
H2 C3 * c-C3H C5 * C5H C6H CH3C3N CH3C4H CH3C5N HC9N c-C6H6 * HC11N
AlF C2H l-C3H C4H l-H2C4 CH2CHCN HC(O)OCH3 CH3CH2CN (CH3)2CO CH3C6H C2H5OCH3 ? C60 *
AlCl C2O C3N C4Si C2H4* CH3C2H CH3COOH (CH3)2O (CH2OH)2 C2H5OCHO n-C3H7CN C70 *
C2** C2S C3O l-C3H2 CH3CN HC5N C7H CH3CH2OH CH3CH2CHO CH3OC(O)CH3
2013
i-C3H7CN
2014
 
CH CH2 C3S c-C3H2 CH3NC CH3CHO C6H2 HC7N        
CH+ HCN C2H2* H2CCN CH3OH CH3NH2 CH2OHCHO C8H        
CN HCO NH3 CH4 * CH3SH c-C2H4O l-HC6H * CH3C(O)NH2        
CO HCO+ HCCN HC3N HC3NH+ H2CCHOH CH2CHCHO (?) C8H        
CO+ HCS+ HCNH+ HC2NC HC2CHO C6H CH2CCHCN C3H6        
CP HOC+ HNCO HCOOH NH2CHO   H2NCH2CN CH3CH2SH (?)        
SiC H2O HNCS H2CNH C5N   CH3CHNH
2013
         
HCl H2S HOCO+ H2C2O l-HC4H *              
KCl HNC H2CO H2NCN l-HC4N              
NH HNO H2CN HNC3 c-H2C3O              
NO MgCN H2CS SiH4 * H2CCNH (?)              
NS MgNC H3O+ H2COH+ C5N              
NaCl N2H+ c-SiC3 C4H HNCHCN
2013
             
OH N2O CH3 * HC(O)CN                
PN NaCN C3N HNCNH                
SO OCS PH3 CH3O                
SO+ SO2 HCNO NH4+
2013
               
SiN c-SiC2 HOCN H2NCO+ (?)
2013
               
SiO CO2 * HSCN                  
SiS NH2 H2O2                  
CS H3+(*) C3H+                  
HF SiCN HMgNC
2013
                 
HD AlNC                    
FeO ? SiNC                    
O2 HCP                    
CF+ CCP                    
SiH ? AlOH                    
PO H2O+                    
AlO H2Cl+                    
OH+ KCN                    
CN FeCN                    
SH+ HO2                    
SH
2012
TiO2
2013
                   
HCl+ C2N
2014
                   
TiO
2012/13
                     
ArH+
2013
                     
NO+ ?
2014
                     

The year most relevant to the detection (including isotopic species or vibrationally excited states) is given for recent results – the past two to three years.

Currently, two molecules have been reported as detected whose detections have been questioned fairly convincingly in subsequent papers. Therefore, we consider these molecules as not yet detected. These molecules are aminoacetic acid, H2NCH2COOH, aka glycine, and 1,3-dihydroxypropanone, aka dihydroxyacetone.

The detection of SH by rovibrational spectroscopy of the S-type star R Andromedae has been omitted from this table as the molecule is present in the stellar atmosphere. It is hoped that a table of molecules in stellar atmospheres will be available in the not too distant future. Note, however, that the SH radical has recently been detected unambiguously in the ISM.

Extragalactic Molecules (as of 07/2014)

2 atoms 3 atoms 4 atoms 5 atoms 6 atoms 7 atoms 8 atoms >8 atoms
OH H2O H2CO c-C3H2 CH3OH CH3CCH HC6H c-C6H6 *
CO HCN NH3 HC3N CH3CN CH3NH2   C60* (?)
H2 * HCO+ HNCO CH2NH HC4H * CH3CHO    
CH C2H C2H2 * NH2CN HC(O)NH2
2013
     
CS HNC H2CS ? l-C3H2        
CH+ ** N2H+ HOCO+ H2CCN        
CN OCS c-C3H H2CCO        
SO HCO H3O+ C4H        
SiO H2S l-C3H          
CO+ SO2            
NO HOC+            
NS C2S            
NH H2O+            
OH+ HCS+
2013
           
HF H2Cl+
2014
           
SO+ NH2
2014