Detection of amino acetonitrile in Sgr B2(N)

Abstract

Context. Amino acids are building blocks of proteins and therefore key ingredients for the origin of life. The simplest amino acid, glycine (NH 2 CH 2 COOH), has long been searched for in the interstellar medium but has not been unambiguously detected so far. At the same time, more and more complex molecules have been newly found toward the prolific Galactic center source Sagittarius B2. Aims. Since the search for glycine has turned out to be extremely difficult, we aimed at detecting a chemically related species (possibly a direct precursor), amino acetonitrile (NH 2 CH 2 CN). Methods. With the IRAM 30 m telescope we carried out a complete line survey of the hot core regions Sgr B2(N) and (M) in the 3 mm range, plus partial surveys at 2 and 1.3 mm. We analyzed our 30 m line survey in the LTE approximation and modeled the emission of all known molecules simultaneously. We identified spectral features at the frequencies predicted for amino acetonitrile lines having intensities compatible with a unique rotation temperature. We also used the Very Large Array to look for cold, extended emission from amino acetonitrile. Results. We detected amino acetonitrile in Sgr B2(N) in our 30 m telescope line survey and conducted confirmatory observations of selected lines with the IRAM Plateau de Bure and the Australia Telescope Compact Array interferometers. The emission arises from a known hot core, the Large Molecule Heimat, and is compact with a source diameter of 2 (0.08 pc). We derived a column density of 2.8 × 10 16 cm −2 , a temperature of 100 K, and a linewidth of 7 km s −1 . Based on the simultaneously observed continuum emission, we calculated a density of 1.7 × 10 8 cm −3 , a mass of 2340 M , and an amino acetonitrile fractional abundance of 2.2 × 10 −9 . The high abundance and temperature may indicate that amino acetonitrile is formed by grain surface chemistry. We did not detect any hot, compact amino acetonitrile emission toward Sgr B2(M) or any cold, extended emission toward Sgr B2, with column-density upper limits of 6 × 10 15 and 3 × 10 12−14 cm −2 , respectively. Conclusions. Based on our amino acetonitrile detection toward Sgr B2(N) and a comparison to the pair methylcyanide/acetic acid both detected in this source, we suggest that the column density of both glycine conformers in Sgr B2(N) is well below the best upper limits published recently by other authors, and probably below the confusion limit in the 1−3 mm range.

TIMASSS: the IRAS 16293-2422 millimeter and submillimeter spectral survey

“…have value comparable to the present survey. SgrB2 appears as a noticeable exception, displaying significantly higher line densities, as high as 100 lines per GHz in the 3 mm range observed with IRAM (Belloche et al 2007) or 40 lines per GHz in the 1 mm range observed with SEST (Nummelin et al 1998(Nummelin et al , 2000. Interestingly, the slope of -0.9 that we observe for the cumulative number of lines versus flux threshold is identical to the slopes observed by Schilke et al (2001), White et al (2003), and Comito et al (2005) in their submillimeter surveys of Orion-KL.…”

“…They have covered the whole range of frequencies reachable from the ground, from the 3 mm range observed with IRAM, SEST, NRAO, or JCMT to the submillimeter windows observable with the CSO and JCMT (MacDonald et al 1996;Schilke et al 1997;Helmich & van Dishoeck 1997;Nummelin et al 1998;Thompson & MacDonald 1999;Kim et al 2000;Nummelin et al 2000;Lee et al 2001;Schilke et al 2001;White et al 2003;Comito et al 2005;Kim et al 2006;Belloche et al 2007;Olofsson et al 2007;Tercero et al 2010). The line densities usually range from 10 to 20 lines per GHz, i.e.…”

HCOOCH3as a probe of temperature and structure in Orion-KL

“…In addition that in the case of our dataset, the last parameters vary from one datacube to the next, so that η D is only an average value. It is, however, a first indication of the relative importance of the confusion problem -a similar indicator was given by Belloche et al (2008) for their search and detection of amino acetonitrile in Sgr B2(N).…”

Solid state chemistry of nitrogen oxides – Part II: surface consumption of NO2

“…1,61 The exact origin of these species is still unclear, but recent models indicate that surface reaction mechanisms are most likely the main formation channel. 2 Garrod 2 showed that the gas-phase formation of glycine (NH 2 CH 2 COOH) in hot cores depends on the timescale of the hot-core evolution and the availability of precursor species in the gas phase.…”